From 25d8b86992fd326efbb15cabd9e89a2116a7a96d Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 3 Dec 2022 10:48:00 -0500
Subject: [PATCH 001/157] Add new IsCheckedChanged event to ToggleButton

Old events are now obsoleted
---
 .../Primitives/ToggleButton.cs                | 41 ++++++++++++++++---
 1 file changed, 35 insertions(+), 6 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/ToggleButton.cs b/src/Avalonia.Controls/Primitives/ToggleButton.cs
index 148797c53a..93ec17f0ca 100644
--- a/src/Avalonia.Controls/Primitives/ToggleButton.cs
+++ b/src/Avalonia.Controls/Primitives/ToggleButton.cs
@@ -32,20 +32,37 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Defines the <see cref="Checked"/> event.
         /// </summary>
+        [Obsolete("Use IsCheckedChangedEvent instead.")]
         public static readonly RoutedEvent<RoutedEventArgs> CheckedEvent =
-            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(nameof(Checked), RoutingStrategies.Bubble);
+            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(
+                nameof(Checked),
+                RoutingStrategies.Bubble);
 
         /// <summary>
         /// Defines the <see cref="Unchecked"/> event.
         /// </summary>
+        [Obsolete("Use IsCheckedChangedEvent instead.")]
         public static readonly RoutedEvent<RoutedEventArgs> UncheckedEvent =
-            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(nameof(Unchecked), RoutingStrategies.Bubble);
+            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(
+                nameof(Unchecked),
+                RoutingStrategies.Bubble);
 
         /// <summary>
         /// Defines the <see cref="Unchecked"/> event.
         /// </summary>
+        [Obsolete("Use IsCheckedChangedEvent instead.")]
         public static readonly RoutedEvent<RoutedEventArgs> IndeterminateEvent =
-            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(nameof(Indeterminate), RoutingStrategies.Bubble);
+            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(
+                nameof(Indeterminate),
+                RoutingStrategies.Bubble);
+
+        /// <summary>
+        /// Defines the <see cref="IsCheckedChanged"/> event.
+        /// </summary>
+        public static readonly RoutedEvent<RoutedEventArgs> IsCheckedChangedEvent =
+            RoutedEvent.Register<ToggleButton, RoutedEventArgs>(
+                nameof(IsCheckedChanged),
+                RoutingStrategies.Bubble);
 
         private bool? _isChecked = false;
 
@@ -62,6 +79,7 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Raised when a <see cref="ToggleButton"/> is checked.
         /// </summary>
+        [Obsolete("Use IsCheckedChanged instead.")]
         public event EventHandler<RoutedEventArgs>? Checked
         {
             add => AddHandler(CheckedEvent, value);
@@ -71,6 +89,7 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Raised when a <see cref="ToggleButton"/> is unchecked.
         /// </summary>
+        [Obsolete("Use IsCheckedChanged instead.")]
         public event EventHandler<RoutedEventArgs>? Unchecked
         {
             add => AddHandler(UncheckedEvent, value);
@@ -80,12 +99,22 @@ namespace Avalonia.Controls.Primitives
         /// <summary>
         /// Raised when a <see cref="ToggleButton"/> is neither checked nor unchecked.
         /// </summary>
+        [Obsolete("Use IsCheckedChanged instead.")]
         public event EventHandler<RoutedEventArgs>? Indeterminate
         {
             add => AddHandler(IndeterminateEvent, value);
             remove => RemoveHandler(IndeterminateEvent, value);
         }
 
+        /// <summary>
+        /// Raised when the <see cref="IsChecked"/> property value changes.
+        /// </summary>
+        public event EventHandler<RoutedEventArgs>? IsCheckedChanged
+        {
+            add => AddHandler(IsCheckedChangedEvent, value);
+            remove => RemoveHandler(IsCheckedChangedEvent, value);
+        }
+
         /// <summary>
         /// Gets or sets whether the <see cref="ToggleButton"/> is checked.
         /// </summary>
@@ -182,13 +211,13 @@ namespace Avalonia.Controls.Primitives
             switch (newValue)
             {
                 case true:
-                    OnChecked(new RoutedEventArgs(CheckedEvent));
+                    OnChecked(new RoutedEventArgs(IsCheckedChangedEvent));
                     break;
                 case false:
-                    OnUnchecked(new RoutedEventArgs(UncheckedEvent));
+                    OnUnchecked(new RoutedEventArgs(IsCheckedChangedEvent));
                     break;
                 default:
-                    OnIndeterminate(new RoutedEventArgs(IndeterminateEvent));
+                    OnIndeterminate(new RoutedEventArgs(IsCheckedChangedEvent));
                     break;
             }
         }

From 0a36aec64a1f312578b02e5d9dd63ac7e3c39b3a Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 3 Dec 2022 10:48:24 -0500
Subject: [PATCH 002/157] Fix IsCheckedChanged in ToggleSplitButton to be
 nullable

---
 src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
index 83bc9851c1..fd7ea28ba1 100644
--- a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
@@ -18,7 +18,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Raised when the <see cref="IsChecked"/> property value changes.
         /// </summary>
-        public event EventHandler<RoutedEventArgs> IsCheckedChanged
+        public event EventHandler<RoutedEventArgs>? IsCheckedChanged
         {
             add => AddHandler(IsCheckedChangedEvent, value);
             remove => RemoveHandler(IsCheckedChangedEvent, value);

From 59ee997516c1d96f1a7fe4c774bb36e619f7d963 Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 3 Dec 2022 10:50:56 -0500
Subject: [PATCH 003/157] Remove code section formatting blocks

In later commits it was agreed not to include these in the future.
---
 .../SplitButton/SplitButton.cs                | 20 -------------------
 .../SplitButton/ToggleSplitButton.cs          | 16 ---------------
 2 files changed, 36 deletions(-)

diff --git a/src/Avalonia.Controls/SplitButton/SplitButton.cs b/src/Avalonia.Controls/SplitButton/SplitButton.cs
index f39064435d..b2139f01e9 100644
--- a/src/Avalonia.Controls/SplitButton/SplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/SplitButton.cs
@@ -68,10 +68,6 @@ namespace Avalonia.Controls
 
         private IDisposable? _flyoutPropertyChangedDisposable;
 
-        ////////////////////////////////////////////////////////////////////////
-        // Constructor / Destructors
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Initializes a new instance of the <see cref="SplitButton"/> class.
         /// </summary>
@@ -79,10 +75,6 @@ namespace Avalonia.Controls
         {
         }
 
-        ////////////////////////////////////////////////////////////////////////
-        // Properties
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Gets or sets the <see cref="ICommand"/> invoked when the primary part is pressed.
         /// </summary>
@@ -123,10 +115,6 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         protected override bool IsEnabledCore => base.IsEnabledCore && _commandCanExecute;
 
-        ////////////////////////////////////////////////////////////////////////
-        // Methods
-        ////////////////////////////////////////////////////////////////////////
-
         /// <inheritdoc/>
         void ICommandSource.CanExecuteChanged(object sender, EventArgs e) => this.CanExecuteChanged(sender, e);
 
@@ -221,10 +209,6 @@ namespace Avalonia.Controls
             }
         }
 
-        ////////////////////////////////////////////////////////////////////////
-        // OnEvent Overridable Methods
-        ////////////////////////////////////////////////////////////////////////
-
         /// <inheritdoc/>
         protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
@@ -428,10 +412,6 @@ namespace Avalonia.Controls
             // Available for derived types
         }
 
-        ////////////////////////////////////////////////////////////////////////
-        // Event Handling
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Event handler for when the internal primary button part is pressed.
         /// </summary>
diff --git a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
index fd7ea28ba1..70d2983b9b 100644
--- a/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/ToggleSplitButton.cs
@@ -39,10 +39,6 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<ToggleSplitButton, bool>(
                 nameof(IsChecked));
 
-        ////////////////////////////////////////////////////////////////////////
-        // Constructor / Destructors
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ToggleSplitButton"/> class.
         /// </summary>
@@ -50,10 +46,6 @@ namespace Avalonia.Controls
         {
         }
 
-        ////////////////////////////////////////////////////////////////////////
-        // Properties
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Gets or sets a value indicating whether the <see cref="ToggleSplitButton"/> is checked.
         /// </summary>
@@ -73,10 +65,6 @@ namespace Avalonia.Controls
         /// </remarks>
         Type IStyleable.StyleKey => typeof(SplitButton);
 
-        ////////////////////////////////////////////////////////////////////////
-        // Methods
-        ////////////////////////////////////////////////////////////////////////
-
         /// <summary>
         /// Toggles the <see cref="IsChecked"/> property between true and false.
         /// </summary>
@@ -85,10 +73,6 @@ namespace Avalonia.Controls
             IsChecked = !IsChecked;
         }
 
-        ////////////////////////////////////////////////////////////////////////
-        // OnEvent Overridable Methods
-        ////////////////////////////////////////////////////////////////////////
-
         /// <inheritdoc/>
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs e)
         {

From f4827bdfdbe22acb37132029975ed0fd711e8a65 Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 3 Dec 2022 10:52:29 -0500
Subject: [PATCH 004/157] Fix Click in SplitButton to be nullable

---
 src/Avalonia.Controls/SplitButton/SplitButton.cs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls/SplitButton/SplitButton.cs b/src/Avalonia.Controls/SplitButton/SplitButton.cs
index b2139f01e9..353674b26e 100644
--- a/src/Avalonia.Controls/SplitButton/SplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/SplitButton.cs
@@ -24,7 +24,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Raised when the user presses the primary part of the <see cref="SplitButton"/>.
         /// </summary>
-        public event EventHandler<RoutedEventArgs> Click
+        public event EventHandler<RoutedEventArgs>? Click
         {
             add => AddHandler(ClickEvent, value);
             remove => RemoveHandler(ClickEvent, value);
@@ -34,7 +34,9 @@ namespace Avalonia.Controls
         /// Defines the <see cref="Click"/> event.
         /// </summary>
         public static readonly RoutedEvent<RoutedEventArgs> ClickEvent =
-            RoutedEvent.Register<SplitButton, RoutedEventArgs>(nameof(Click), RoutingStrategies.Bubble);
+            RoutedEvent.Register<SplitButton, RoutedEventArgs>(
+                nameof(Click),
+                RoutingStrategies.Bubble);
 
         /// <summary>
         /// Defines the <see cref="Command"/> property.

From 0bb1b2ec03c7caf68d9a9fdcfa77d11ed51ce518 Mon Sep 17 00:00:00 2001
From: robloo <robloo@users.noreply.github.com>
Date: Sat, 3 Dec 2022 11:37:45 -0500
Subject: [PATCH 005/157] Fix ToggleButton tests

---
 .../Primitives/ToggleButton.cs                | 47 ++++++++++++++-----
 1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/ToggleButton.cs b/src/Avalonia.Controls/Primitives/ToggleButton.cs
index 93ec17f0ca..dfb436a55e 100644
--- a/src/Avalonia.Controls/Primitives/ToggleButton.cs
+++ b/src/Avalonia.Controls/Primitives/ToggleButton.cs
@@ -68,7 +68,6 @@ namespace Avalonia.Controls.Primitives
 
         static ToggleButton()
         {
-            IsCheckedProperty.Changed.AddClassHandler<ToggleButton>((x, e) => x.OnIsCheckedChanged(e));
         }
 
         public ToggleButton()
@@ -176,6 +175,7 @@ namespace Avalonia.Controls.Primitives
         /// Called when <see cref="IsChecked"/> becomes true.
         /// </summary>
         /// <param name="e">Event arguments for the routed event that is raised by the default implementation of this method.</param>
+        [Obsolete("Use OnIsCheckedChanged instead.")]
         protected virtual void OnChecked(RoutedEventArgs e)
         {
             RaiseEvent(e);
@@ -185,6 +185,7 @@ namespace Avalonia.Controls.Primitives
         /// Called when <see cref="IsChecked"/> becomes false.
         /// </summary>
         /// <param name="e">Event arguments for the routed event that is raised by the default implementation of this method.</param>
+        [Obsolete("Use OnIsCheckedChanged instead.")]
         protected virtual void OnUnchecked(RoutedEventArgs e)
         {
             RaiseEvent(e);
@@ -194,31 +195,51 @@ namespace Avalonia.Controls.Primitives
         /// Called when <see cref="IsChecked"/> becomes null.
         /// </summary>
         /// <param name="e">Event arguments for the routed event that is raised by the default implementation of this method.</param>
+        [Obsolete("Use OnIsCheckedChanged instead.")]
         protected virtual void OnIndeterminate(RoutedEventArgs e)
         {
             RaiseEvent(e);
         }
 
+        /// <summary>
+        /// Called when <see cref="IsChecked"/> changes.
+        /// </summary>
+        /// <param name="e">Event arguments for the routed event that is raised by the default implementation of this method.</param>
+        protected virtual void OnIsCheckedChanged(RoutedEventArgs e)
+        {
+            RaiseEvent(e);
+        }
+
         protected override AutomationPeer OnCreateAutomationPeer()
         {
             return new ToggleButtonAutomationPeer(this);
         }
 
-        private void OnIsCheckedChanged(AvaloniaPropertyChangedEventArgs e)
+        /// <inheritdoc/>
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
-            var newValue = (bool?)e.NewValue;
+            base.OnPropertyChanged(change);
 
-            switch (newValue)
+            if (change.Property == IsCheckedProperty)
             {
-                case true:
-                    OnChecked(new RoutedEventArgs(IsCheckedChangedEvent));
-                    break;
-                case false:
-                    OnUnchecked(new RoutedEventArgs(IsCheckedChangedEvent));
-                    break;
-                default:
-                    OnIndeterminate(new RoutedEventArgs(IsCheckedChangedEvent));
-                    break;
+                var newValue = change.GetNewValue<bool?>();
+
+#pragma warning disable CS0618 // Type or member is obsolete
+                switch (newValue)
+                {
+                    case true:
+                        OnChecked(new RoutedEventArgs(CheckedEvent));
+                        break;
+                    case false:
+                        OnUnchecked(new RoutedEventArgs(UncheckedEvent));
+                        break;
+                    default:
+                        OnIndeterminate(new RoutedEventArgs(IndeterminateEvent));
+                        break;
+                }
+#pragma warning restore CS0618 // Type or member is obsolete
+
+                OnIsCheckedChanged(new RoutedEventArgs(IsCheckedChangedEvent));
             }
         }
 

From 692c0c155dd2f9c8285fb95ede288a18f2ded600 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 24 Nov 2022 23:13:05 +0100
Subject: [PATCH 006/157] Begin refactoring ItemsPresenter.

A lot still broken, in particular virtualization is completely removed.`ItemsPresenter` now no longer has an `Items` or `ItemTemplate` property; it detects when it's hosted in an `ItemsControl`. `IItemsPresenter` interface removed.
---
 .../ControlCatalog/Pages/DialogsPage.xaml.cs  |  588 +++---
 .../HamburgerMenu/HamburgerMenu.xaml          |    4 +-
 .../Themes/Fluent/ColorView.xaml              |    5 +-
 .../Themes/Simple/ColorView.xaml              |    5 +-
 src/Avalonia.Controls/ComboBox.cs             |    2 +-
 src/Avalonia.Controls/IVirtualizingPanel.cs   |   78 -
 src/Avalonia.Controls/ItemsControl.cs         |   12 +-
 src/Avalonia.Controls/ListBox.cs              |    2 +-
 .../Presenters/CarouselPresenter.cs           |  344 ++--
 .../Presenters/IItemsPresenter.cs             |   18 -
 .../Presenters/IItemsPresenterHost.cs         |    4 +-
 .../Presenters/ItemContainerSync.cs           |  125 --
 .../Presenters/ItemVirtualizer.cs             |  303 ---
 .../Presenters/ItemVirtualizerNone.cs         |  106 -
 .../Presenters/ItemVirtualizerSimple.cs       |  606 ------
 .../Presenters/ItemsPresenter.cs              |  187 +-
 .../Presenters/ItemsPresenterBase.cs          |  308 ---
 .../ItemsPresenterContainerGenerator.cs       |  108 +
 .../Primitives/SelectingItemsControl.cs       |    2 +-
 .../VirtualizingStackPanel.cs                 |  252 +--
 .../Controls/Carousel.xaml                    |    1 -
 .../Controls/ComboBox.xaml                    |    5 +-
 .../Controls/ContextMenu.xaml                 |    2 -
 .../Controls/ItemsControl.xaml                |    4 +-
 .../Controls/ListBox.xaml                     |    5 +-
 .../Controls/ManagedFileChooser.xaml          |    5 +-
 src/Avalonia.Themes.Fluent/Controls/Menu.xaml |    4 -
 .../Controls/MenuFlyoutPresenter.xaml         |    2 -
 .../Controls/MenuItem.xaml                    |    2 -
 .../Controls/TabControl.xaml                  |    2 -
 .../Controls/TabStrip.xaml                    |    4 +-
 .../Controls/TreeView.xaml                    |    1 -
 .../Controls/TreeViewItem.xaml                |    1 -
 .../Controls/Carousel.xaml                    |    1 -
 .../Controls/ComboBox.xaml                    |    5 +-
 .../Controls/ContextMenu.xaml                 |    2 -
 .../Controls/ItemsControl.xaml                |    2 -
 .../Controls/ListBox.xaml                     |    5 +-
 src/Avalonia.Themes.Simple/Controls/Menu.xaml |    4 -
 .../Controls/MenuFlyoutPresenter.xaml         |    2 -
 .../Controls/MenuItem.xaml                    |    2 -
 .../Controls/TabControl.xaml                  |    2 -
 .../Controls/TabStrip.xaml                    |    2 -
 .../Controls/TreeView.xaml                    |    1 -
 .../Controls/TreeViewItem.xaml                |    1 -
 .../CarouselTests.cs                          |    1 -
 .../ComboBoxTests.cs                          |    1 -
 .../ItemsControlTests.cs                      |    4 +-
 .../ListBoxTests.cs                           |   52 +-
 .../ListBoxTests_Multiple.cs                  |    1 -
 .../ListBoxTests_Single.cs                    |    1 -
 .../Presenters/CarouselPresenterTests.cs      | 1464 ++++++-------
 .../Presenters/ItemsPresenterTests.cs         |  370 +---
 .../ItemsPresenterTests_Virtualization.cs     |  748 +++----
 ...emsPresenterTests_Virtualization_Simple.cs | 1822 ++++++++---------
 .../Primitives/PopupTests.cs                  |    5 +-
 .../Primitives/SelectingItemsControlTests.cs  |    2 -
 .../SelectingItemsControlTests_AutoSelect.cs  |    1 -
 .../SelectingItemsControlTests_Multiple.cs    |    1 -
 .../Primitives/TabStripTests.cs               |    1 -
 .../TreeViewTests.cs                          |    2 -
 .../VirtualizingStackPanelTests.cs            |  522 ++---
 .../AutoDataTemplateBindingHookTest.cs        |    1 -
 tests/Avalonia.UnitTests/TestExtensions.cs    |    1 -
 64 files changed, 3040 insertions(+), 5086 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/IItemsPresenter.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemContainerSync.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
 delete mode 100644 src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
 create mode 100644 src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 67e9ef4e40..41a5b86ebd 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -24,301 +24,301 @@ namespace ControlCatalog.Pages
         {
             this.InitializeComponent();
 
-            var results = this.Get<ItemsPresenter>("PickerLastResults");
-            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
-            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
-            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
-            var openMultiple = this.Get<CheckBox>("OpenMultiple");
-
-            IStorageFolder? lastSelectedDirectory = null;
-
-            List<FileDialogFilter> GetFilters()
-            {
-                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-                    return new List<FileDialogFilter>();
-                return  new List<FileDialogFilter>
-                {
-                    new FileDialogFilter
-                    {
-                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
-                    },
-                    new FileDialogFilter
-                    {
-                        Name = "All files",
-                        Extensions = new List<string> {"*"}
-                    }
-                };
-            }
-
-            List<FilePickerFileType>? GetFileTypes()
-            {
-                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-                    return null;
-                return new List<FilePickerFileType>
-                {
-                    FilePickerFileTypes.All,
-                    FilePickerFileTypes.TextPlain
-                };
-            }
-
-            this.Get<Button>("OpenFile").Click += async delegate
-            {
-                // Almost guaranteed to exist
-                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
-                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
-                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
-
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Open file",
-                    Filters = GetFilters(),
-                    Directory = initialDirectory,
-                    InitialFileName = initialFileName
-                }.ShowAsync(GetWindow());
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("OpenMultipleFiles").Click += async delegate
-            {
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Open multiple files",
-                    Filters = GetFilters(),
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    AllowMultiple = true
-                }.ShowAsync(GetWindow());
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("SaveFile").Click += async delegate
-            {
-                var filters = GetFilters();
-                var result = await new SaveFileDialog()
-                {
-                    Title = "Save file",
-                    Filters = filters,
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    DefaultExtension = filters?.Any() == true ? "txt" : null,
-                    InitialFileName = "test.txt"
-                }.ShowAsync(GetWindow());
-                results.Items = new[] { result };
-                resultsVisible.IsVisible = result != null;
-            };
-            this.Get<Button>("SelectFolder").Click += async delegate
-            {
-                var result = await new OpenFolderDialog()
-                {
-                    Title = "Select folder",
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
-                }.ShowAsync(GetWindow());
-                if (string.IsNullOrEmpty(result))
-                {
-                    resultsVisible.IsVisible = false;
-                }
-                else
-                {
-                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
-                    results.Items = new[] { result };
-                    resultsVisible.IsVisible = true;
-                }
-            };
-            this.Get<Button>("OpenBoth").Click += async delegate
-            {
-                var result = await new OpenFileDialog()
-                {
-                    Title = "Select both",
-                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-                    AllowMultiple = true
-                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
-                {
-                    AllowDirectorySelection = true
-                });
-                results.Items = result;
-                resultsVisible.IsVisible = result?.Any() == true;
-            };
-            this.Get<Button>("DecoratedWindow").Click += delegate
-            {
-                new DecoratedWindow().Show();
-            };
-            this.Get<Button>("DecoratedWindowDialog").Click += delegate
-            {
-                _ = new DecoratedWindow().ShowDialog(GetWindow());
-            };
-            this.Get<Button>("Dialog").Click += delegate
-            {
-                var window = CreateSampleWindow();
-                window.Height = 200;
-                _ = window.ShowDialog(GetWindow());
-            };
-            this.Get<Button>("DialogNoTaskbar").Click += delegate
-            {
-                var window = CreateSampleWindow();
-                window.Height = 200;
-                window.ShowInTaskbar = false;
-                _ = window.ShowDialog(GetWindow());
-            };
-            this.Get<Button>("OwnedWindow").Click += delegate
-            {
-                var window = CreateSampleWindow();
-
-                window.Show(GetWindow());
-            };
-
-            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
-            {
-                var window = CreateSampleWindow();
-
-                window.ShowInTaskbar = false;
-
-                window.Show(GetWindow());
-            };
-
-            this.Get<Button>("OpenFilePicker").Click += async delegate
-            {
-                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
-                {
-                    Title = "Open file",
-                    FileTypeFilter = GetFileTypes(),
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    AllowMultiple = openMultiple.IsChecked == true
-                });
-
-                await SetPickerResult(result);
-            };
-            this.Get<Button>("SaveFilePicker").Click += async delegate
-            {
-                var fileTypes = GetFileTypes();
-                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
-                {
-                    Title = "Save file",
-                    FileTypeChoices = fileTypes,
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    SuggestedFileName = "FileName",
-                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
-                    ShowOverwritePrompt = false
-                });
-
-                if (file is not null && file.CanOpenWrite)
-                {
-                    // Sync disposal of StreamWriter is not supported on WASM
-#if NET6_0_OR_GREATER
-                    await using var stream = await file.OpenWriteAsync();
-                    await using var reader = new System.IO.StreamWriter(stream);
-#else
-                    using var stream = await file.OpenWriteAsync();
-                    using var reader = new System.IO.StreamWriter(stream);
-#endif
-                    await reader.WriteLineAsync(openedFileContent.Text);
-
-                    lastSelectedDirectory = await file.GetParentAsync();
-                }
-
-                await SetPickerResult(file is null ? null : new [] {file});
-            };
-            this.Get<Button>("OpenFolderPicker").Click += async delegate
-            {
-                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
-                {
-                    Title = "Folder file",
-                    SuggestedStartLocation = lastSelectedDirectory,
-                    AllowMultiple = openMultiple.IsChecked == true
-                });
-
-                await SetPickerResult(folders);
-
-                lastSelectedDirectory = folders.FirstOrDefault();
-            };
-            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
-            {
-                var file = bookmarkContainer.Text is not null
-                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
-                    : null;
-
-                await SetPickerResult(file is null ? null : new[] { file });
-            };
-            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
-            {
-                var folder = bookmarkContainer.Text is not null
-                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
-                    : null;
-
-                await SetPickerResult(folder is null ? null : new[] { folder });
+////            var results = this.Get<ItemsPresenter>("PickerLastResults");
+////            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
+////            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
+////            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
+////            var openMultiple = this.Get<CheckBox>("OpenMultiple");
+
+////            IStorageFolder? lastSelectedDirectory = null;
+
+////            List<FileDialogFilter> GetFilters()
+////            {
+////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+////                    return new List<FileDialogFilter>();
+////                return  new List<FileDialogFilter>
+////                {
+////                    new FileDialogFilter
+////                    {
+////                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
+////                    },
+////                    new FileDialogFilter
+////                    {
+////                        Name = "All files",
+////                        Extensions = new List<string> {"*"}
+////                    }
+////                };
+////            }
+
+////            List<FilePickerFileType>? GetFileTypes()
+////            {
+////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+////                    return null;
+////                return new List<FilePickerFileType>
+////                {
+////                    FilePickerFileTypes.All,
+////                    FilePickerFileTypes.TextPlain
+////                };
+////            }
+
+////            this.Get<Button>("OpenFile").Click += async delegate
+////            {
+////                // Almost guaranteed to exist
+////                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
+////                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
+////                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
+
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Open file",
+////                    Filters = GetFilters(),
+////                    Directory = initialDirectory,
+////                    InitialFileName = initialFileName
+////                }.ShowAsync(GetWindow());
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("OpenMultipleFiles").Click += async delegate
+////            {
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Open multiple files",
+////                    Filters = GetFilters(),
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    AllowMultiple = true
+////                }.ShowAsync(GetWindow());
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("SaveFile").Click += async delegate
+////            {
+////                var filters = GetFilters();
+////                var result = await new SaveFileDialog()
+////                {
+////                    Title = "Save file",
+////                    Filters = filters,
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    DefaultExtension = filters?.Any() == true ? "txt" : null,
+////                    InitialFileName = "test.txt"
+////                }.ShowAsync(GetWindow());
+////                results.Items = new[] { result };
+////                resultsVisible.IsVisible = result != null;
+////            };
+////            this.Get<Button>("SelectFolder").Click += async delegate
+////            {
+////                var result = await new OpenFolderDialog()
+////                {
+////                    Title = "Select folder",
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
+////                }.ShowAsync(GetWindow());
+////                if (string.IsNullOrEmpty(result))
+////                {
+////                    resultsVisible.IsVisible = false;
+////                }
+////                else
+////                {
+////                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
+////                    results.Items = new[] { result };
+////                    resultsVisible.IsVisible = true;
+////                }
+////            };
+////            this.Get<Button>("OpenBoth").Click += async delegate
+////            {
+////                var result = await new OpenFileDialog()
+////                {
+////                    Title = "Select both",
+////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+////                    AllowMultiple = true
+////                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
+////                {
+////                    AllowDirectorySelection = true
+////                });
+////                results.Items = result;
+////                resultsVisible.IsVisible = result?.Any() == true;
+////            };
+////            this.Get<Button>("DecoratedWindow").Click += delegate
+////            {
+////                new DecoratedWindow().Show();
+////            };
+////            this.Get<Button>("DecoratedWindowDialog").Click += delegate
+////            {
+////                _ = new DecoratedWindow().ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("Dialog").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+////                window.Height = 200;
+////                _ = window.ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("DialogNoTaskbar").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+////                window.Height = 200;
+////                window.ShowInTaskbar = false;
+////                _ = window.ShowDialog(GetWindow());
+////            };
+////            this.Get<Button>("OwnedWindow").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+
+////                window.Show(GetWindow());
+////            };
+
+////            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
+////            {
+////                var window = CreateSampleWindow();
+
+////                window.ShowInTaskbar = false;
+
+////                window.Show(GetWindow());
+////            };
+
+////            this.Get<Button>("OpenFilePicker").Click += async delegate
+////            {
+////                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
+////                {
+////                    Title = "Open file",
+////                    FileTypeFilter = GetFileTypes(),
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    AllowMultiple = openMultiple.IsChecked == true
+////                });
+
+////                await SetPickerResult(result);
+////            };
+////            this.Get<Button>("SaveFilePicker").Click += async delegate
+////            {
+////                var fileTypes = GetFileTypes();
+////                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
+////                {
+////                    Title = "Save file",
+////                    FileTypeChoices = fileTypes,
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    SuggestedFileName = "FileName",
+////                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
+////                    ShowOverwritePrompt = false
+////                });
+
+////                if (file is not null && file.CanOpenWrite)
+////                {
+////                    // Sync disposal of StreamWriter is not supported on WASM
+////#if NET6_0_OR_GREATER
+////                    await using var stream = await file.OpenWriteAsync();
+////                    await using var reader = new System.IO.StreamWriter(stream);
+////#else
+////                    using var stream = await file.OpenWriteAsync();
+////                    using var reader = new System.IO.StreamWriter(stream);
+////#endif
+////                    await reader.WriteLineAsync(openedFileContent.Text);
+
+////                    lastSelectedDirectory = await file.GetParentAsync();
+////                }
+
+////                await SetPickerResult(file is null ? null : new [] {file});
+////            };
+////            this.Get<Button>("OpenFolderPicker").Click += async delegate
+////            {
+////                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
+////                {
+////                    Title = "Folder file",
+////                    SuggestedStartLocation = lastSelectedDirectory,
+////                    AllowMultiple = openMultiple.IsChecked == true
+////                });
+
+////                await SetPickerResult(folders);
+
+////                lastSelectedDirectory = folders.FirstOrDefault();
+////            };
+////            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
+////            {
+////                var file = bookmarkContainer.Text is not null
+////                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
+////                    : null;
+
+////                await SetPickerResult(file is null ? null : new[] { file });
+////            };
+////            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
+////            {
+////                var folder = bookmarkContainer.Text is not null
+////                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
+////                    : null;
+
+////                await SetPickerResult(folder is null ? null : new[] { folder });
                 
-                lastSelectedDirectory = folder;
-            };
-
-            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
-            {
-                items ??= Array.Empty<IStorageItem>();
-                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
-                var mappedResults = new List<string>();
-
-                if (items.FirstOrDefault() is IStorageItem item)
-                {
-                    var resultText = item is IStorageFile ? "File:" : "Folder:";
-                    resultText += Environment.NewLine;
-
-                    var props = await item.GetBasicPropertiesAsync();
-                    resultText += @$"Size: {props.Size}
-DateCreated: {props.DateCreated}
-DateModified: {props.DateModified}
-CanBookmark: {item.CanBookmark}
-";
-                    if (item is IStorageFile file)
-                    {
-                        resultText += @$"
-CanOpenRead: {file.CanOpenRead}
-CanOpenWrite: {file.CanOpenWrite}
-Content:
-";
-                        if (file.CanOpenRead)
-                        {
-#if NET6_0_OR_GREATER
-                            await using var stream = await file.OpenReadAsync();
-#else
-                            using var stream = await file.OpenReadAsync();
-#endif
-                            using var reader = new System.IO.StreamReader(stream);
-
-                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
-                            const int length = 10000;
-                            var buffer = ArrayPool<char>.Shared.Rent(length);
-                            try
-                            {
-                                var charsRead = await reader.ReadAsync(buffer, 0, length);
-                                resultText += new string(buffer, 0, charsRead);
-                            }
-                            finally
-                            {
-                                ArrayPool<char>.Shared.Return(buffer);
-                            }
-                        }
-                    }
-
-                    openedFileContent.Text = resultText;
-
-                    lastSelectedDirectory = await item.GetParentAsync();
-                    if (lastSelectedDirectory is not null)
-                    {
-                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
-                    }
-
-                    foreach (var selectedItem in items)
-                    {
-                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
-                        if (selectedItem is IStorageFolder folder)
-                        {
-                            foreach (var innerItems in await folder.GetItemsAsync())
-                            {
-                                mappedResults.Add("++> " + FullPathOrName(innerItems));
-                            }
-                        }
-                    }
-                }
-
-                results.Items = mappedResults;
-                resultsVisible.IsVisible = mappedResults.Any();
-            }
+////                lastSelectedDirectory = folder;
+////            };
+
+////            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
+////            {
+////                items ??= Array.Empty<IStorageItem>();
+////                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
+////                var mappedResults = new List<string>();
+
+////                if (items.FirstOrDefault() is IStorageItem item)
+////                {
+////                    var resultText = item is IStorageFile ? "File:" : "Folder:";
+////                    resultText += Environment.NewLine;
+
+////                    var props = await item.GetBasicPropertiesAsync();
+////                    resultText += @$"Size: {props.Size}
+////DateCreated: {props.DateCreated}
+////DateModified: {props.DateModified}
+////CanBookmark: {item.CanBookmark}
+////";
+////                    if (item is IStorageFile file)
+////                    {
+////                        resultText += @$"
+////CanOpenRead: {file.CanOpenRead}
+////CanOpenWrite: {file.CanOpenWrite}
+////Content:
+////";
+////                        if (file.CanOpenRead)
+////                        {
+////#if NET6_0_OR_GREATER
+////                            await using var stream = await file.OpenReadAsync();
+////#else
+////                            using var stream = await file.OpenReadAsync();
+////#endif
+////                            using var reader = new System.IO.StreamReader(stream);
+
+////                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
+////                            const int length = 10000;
+////                            var buffer = ArrayPool<char>.Shared.Rent(length);
+////                            try
+////                            {
+////                                var charsRead = await reader.ReadAsync(buffer, 0, length);
+////                                resultText += new string(buffer, 0, charsRead);
+////                            }
+////                            finally
+////                            {
+////                                ArrayPool<char>.Shared.Return(buffer);
+////                            }
+////                        }
+////                    }
+
+////                    openedFileContent.Text = resultText;
+
+////                    lastSelectedDirectory = await item.GetParentAsync();
+////                    if (lastSelectedDirectory is not null)
+////                    {
+////                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
+////                    }
+
+////                    foreach (var selectedItem in items)
+////                    {
+////                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
+////                        if (selectedItem is IStorageFolder folder)
+////                        {
+////                            foreach (var innerItems in await folder.GetItemsAsync())
+////                            {
+////                                mappedResults.Add("++> " + FullPathOrName(innerItems));
+////                            }
+////                        }
+////                    }
+////                }
+
+////                results.Items = mappedResults;
+////                resultsVisible.IsVisible = mappedResults.Any();
+////            }
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
diff --git a/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml b/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
index f36b79224a..8bdcf2bb0a 100644
--- a/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
+++ b/samples/SampleControls/HamburgerMenu/HamburgerMenu.xaml
@@ -168,9 +168,7 @@
                               HorizontalScrollBarVisibility="{TemplateBinding (ScrollViewer.HorizontalScrollBarVisibility)}"
                               VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  HorizontalAlignment="Stretch"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}">
+                                  HorizontalAlignment="Stretch">
                     <ItemsPresenter.ItemsPanel>
                       <ItemsPanelTemplate>
                         <StackPanel x:Name="HamburgerItemsPanel"
diff --git a/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml b/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
index f9c4f9b57a..286ca71bc2 100644
--- a/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
+++ b/src/Avalonia.Controls.ColorPicker/Themes/Fluent/ColorView.xaml
@@ -98,11 +98,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml b/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
index 554bca3b63..556099f56b 100644
--- a/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
+++ b/src/Avalonia.Controls.ColorPicker/Themes/Simple/ColorView.xaml
@@ -98,11 +98,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index f02df2e9c1..f8b0ebbbce 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -57,7 +57,7 @@ namespace Avalonia.Controls
         /// Defines the <see cref="VirtualizationMode"/> property.
         /// </summary>
         public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            ItemsPresenter.VirtualizationModeProperty.AddOwner<ComboBox>();
+            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ComboBox>();
 
         /// <summary>
         /// Defines the <see cref="PlaceholderText"/> property.
diff --git a/src/Avalonia.Controls/IVirtualizingPanel.cs b/src/Avalonia.Controls/IVirtualizingPanel.cs
index 9cdbc69cfb..eff469f37a 100644
--- a/src/Avalonia.Controls/IVirtualizingPanel.cs
+++ b/src/Avalonia.Controls/IVirtualizingPanel.cs
@@ -7,83 +7,5 @@ namespace Avalonia.Controls
     /// </summary>
     public interface IVirtualizingPanel
     {
-        /// <summary>
-        /// Gets the children of the panel.
-        /// </summary>
-        Controls Children { get; }
-
-        /// <summary>
-        /// Gets or sets the controller for the virtualizing panel.
-        /// </summary>
-        /// <remarks>
-        /// A virtualizing controller is responsible for maintaining the controls in the virtualizing
-        /// panel. This property will be set by the controller when virtualization is initialized.
-        /// Note that this property may remain null if the panel is added to a control that does
-        /// not act as a virtualizing controller.
-        /// </remarks>
-        IVirtualizingController? Controller { get; set; }
-
-        /// <summary>
-        /// Gets a value indicating whether the panel is full.
-        /// </summary>
-        /// <remarks>
-        /// This property should return false until enough children are added to fill the space
-        /// passed into the last measure or arrange in the direction of scroll. It should be
-        /// updated immediately after a child is added or removed.
-        /// </remarks>
-        bool IsFull { get; }
-
-        /// <summary>
-        /// Gets the number of items that can be removed while keeping the panel full.
-        /// </summary>
-        /// <remarks>
-        /// This property should return the number of children that are completely out of the
-        /// panel's current bounds in the direction of scroll. It should be updated after an
-        /// arrange.
-        /// </remarks>
-        int OverflowCount { get; }
-
-        /// <summary>
-        /// Gets the direction of scroll.
-        /// </summary>
-        Orientation ScrollDirection { get; }
-
-        /// <summary>
-        /// Gets the average size of the materialized items in the direction of scroll.
-        /// </summary>
-        double AverageItemSize { get; }
-
-        /// <summary>
-        /// Gets or sets a size in pixels by which the content is overflowing the panel, in the
-        /// direction of scroll.
-        /// </summary>
-        /// <remarks>
-        /// This may be non-zero even when <see cref="OverflowCount"/> is zero if the last item
-        /// overflows the panel bounds.
-        /// </remarks>
-        double PixelOverflow { get; }
-
-        /// <summary>
-        /// Gets or sets the current pixel offset of the items in the direction of scroll.
-        /// </summary>
-        double PixelOffset { get; set; }
-
-        /// <summary>
-        /// Gets or sets the current scroll offset in the cross axis.
-        /// </summary>
-        double CrossAxisOffset { get; set; }
-
-        /// <summary>
-        /// Invalidates the measure of the control and forces a call to 
-        /// <see cref="IVirtualizingController.UpdateControls"/> on the next measure.
-        /// </summary>
-        /// <remarks>
-        /// The implementation for this method should call
-        /// <see cref="Layoutable.InvalidateMeasure"/> and also ensure that the next call to
-        /// <see cref="Layoutable.Measure(Size)"/> calls
-        /// <see cref="IVirtualizingController.UpdateControls"/> on the next measure even if
-        /// the available size hasn't changed.
-        /// </remarks>
-        void ForceInvalidateMeasure();
     }
 }
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e6c3d67bf4..e51296cdec 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -174,7 +174,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets the items presenter control.
         /// </summary>
-        public IItemsPresenter? Presenter
+        public ItemsPresenter? Presenter
         {
             get;
             protected set;
@@ -189,7 +189,7 @@ namespace Avalonia.Controls
         }
 
         /// <inheritdoc/>
-        void IItemsPresenterHost.RegisterItemsPresenter(IItemsPresenter presenter)
+        void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
             if (Presenter is IChildIndexProvider oldInnerProvider)
             {
@@ -408,12 +408,6 @@ namespace Avalonia.Controls
             UpdateItemCount();
             RemoveControlItemsFromLogicalChildren(oldValue);
             AddControlItemsToLogicalChildren(newValue);
-
-            if (Presenter != null)
-            {
-                Presenter.Items = newValue;
-            }
-
             SubscribeToItems(newValue);
         }
 
@@ -437,8 +431,6 @@ namespace Avalonia.Controls
                     RemoveControlItemsFromLogicalChildren(e.OldItems);
                     break;
             }
-
-            Presenter?.ItemsChanged(e);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 7e5981688c..0adc8a61ba 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -51,7 +51,7 @@ namespace Avalonia.Controls
         /// Defines the <see cref="VirtualizationMode"/> property.
         /// </summary>
         public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            ItemsPresenter.VirtualizationModeProperty.AddOwner<ListBox>();
+            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ListBox>();
 
         private IScrollable? _scroll;
 
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
index 7b435e287d..d5b89a1bdc 100644
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
@@ -12,7 +12,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Displays pages inside an <see cref="ItemsControl"/>.
     /// </summary>
-    public class CarouselPresenter : ItemsPresenterBase
+    public class CarouselPresenter : ItemsPresenter
     {
         /// <summary>
         /// Defines the <see cref="IsVirtualized"/> property.
@@ -43,8 +43,8 @@ namespace Avalonia.Controls.Presenters
         /// </summary>
         static CarouselPresenter()
         {
-            IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
-            SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
+            ////IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
+            ////SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
         }
 
         /// <summary>
@@ -71,14 +71,14 @@ namespace Avalonia.Controls.Presenters
 
             set
             {
-                var old = SelectedIndex;
-                var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
+                ////var old = SelectedIndex;
+                ////var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
 
-                if (old != effective)
-                {
-                    _selectedIndex = effective;
-                    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
-                }
+                ////if (old != effective)
+                ////{
+                ////    _selectedIndex = effective;
+                ////    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
+                ////}
             }
         }
 
@@ -92,185 +92,185 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <inheritdoc/>
-        protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            if (!IsVirtualized)
-            {
-                base.ItemsChanged(e);
+        ////protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
+        ////{
+        ////    if (!IsVirtualized)
+        ////    {
+        ////        base.ItemsChanged(e);
 
-                if (Items == null || SelectedIndex >= Items.Count())
-                {
-                    SelectedIndex = Items.Count() - 1;
-                }
+        ////        if (Items == null || SelectedIndex >= Items.Count())
+        ////        {
+        ////            SelectedIndex = Items.Count() - 1;
+        ////        }
 
-                foreach (var c in ItemContainerGenerator.Containers)
-                {
-                    c.ContainerControl.IsVisible = c.Index == SelectedIndex;
-                }
-            }
-            else if (SelectedIndex != -1 && Panel != null)
-            {
-                switch (e.Action)
-                {
-                    case NotifyCollectionChangedAction.Add:
-                        if (e.NewStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Remove:
-                        if (e.OldStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Replace:
-                        if (e.OldStartingIndex > SelectedIndex ||
-                            e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                    case NotifyCollectionChangedAction.Move:
-                        if (e.OldStartingIndex > SelectedIndex &&
-                            e.NewStartingIndex > SelectedIndex)
-                        {
-                            return;
-                        }
-                        break;
-                }
+        ////        foreach (var c in ItemContainerGenerator.Containers)
+        ////        {
+        ////            c.ContainerControl.IsVisible = c.Index == SelectedIndex;
+        ////        }
+        ////    }
+        ////    else if (SelectedIndex != -1 && Panel != null)
+        ////    {
+        ////        switch (e.Action)
+        ////        {
+        ////            case NotifyCollectionChangedAction.Add:
+        ////                if (e.NewStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Remove:
+        ////                if (e.OldStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Replace:
+        ////                if (e.OldStartingIndex > SelectedIndex ||
+        ////                    e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////            case NotifyCollectionChangedAction.Move:
+        ////                if (e.OldStartingIndex > SelectedIndex &&
+        ////                    e.NewStartingIndex > SelectedIndex)
+        ////                {
+        ////                    return;
+        ////                }
+        ////                break;
+        ////        }
 
-                if (Items == null || SelectedIndex >= Items.Count())
-                {
-                    SelectedIndex = Items.Count() - 1;
-                }
+        ////        if (Items == null || SelectedIndex >= Items.Count())
+        ////        {
+        ////            SelectedIndex = Items.Count() - 1;
+        ////        }
 
-                Panel.Children.Clear();
-                ItemContainerGenerator.Clear();
+        ////        Panel.Children.Clear();
+        ////        ItemContainerGenerator.Clear();
 
-                if (SelectedIndex != -1)
-                {
-                    GetOrCreateContainer(SelectedIndex);
-                }
-            }
-        }
+        ////        if (SelectedIndex != -1)
+        ////        {
+        ////            GetOrCreateContainer(SelectedIndex);
+        ////        }
+        ////    }
+        ////}
 
-        protected override void PanelCreated(Panel panel)
-        {
-            ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        }
+        ////protected override void PanelCreated(Panel panel)
+        ////{
+        ////    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        ////}
 
-        /// <summary>
-        /// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
-        /// </summary>
-        /// <param name="fromIndex">The index of the old page.</param>
-        /// <param name="toIndex">The index of the new page.</param>
-        /// <returns>A task tracking the animation.</returns>
-        private async Task MoveToPage(int fromIndex, int toIndex)
-        {
-            if (fromIndex != toIndex)
-            {
-                var generator = ItemContainerGenerator;
-                Control? from = null;
-                Control? to = null;
+        /////// <summary>
+        /////// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
+        /////// </summary>
+        /////// <param name="fromIndex">The index of the old page.</param>
+        /////// <param name="toIndex">The index of the new page.</param>
+        /////// <returns>A task tracking the animation.</returns>
+        ////private async Task MoveToPage(int fromIndex, int toIndex)
+        ////{
+        ////    if (fromIndex != toIndex)
+        ////    {
+        ////        var generator = ItemContainerGenerator;
+        ////        Control? from = null;
+        ////        Control? to = null;
 
-                if (fromIndex != -1)
-                {
-                    from = generator.ContainerFromIndex(fromIndex);
-                }
+        ////        if (fromIndex != -1)
+        ////        {
+        ////            from = generator.ContainerFromIndex(fromIndex);
+        ////        }
 
-                if (toIndex != -1)
-                {
-                    to = GetOrCreateContainer(toIndex);
-                }
+        ////        if (toIndex != -1)
+        ////        {
+        ////            to = GetOrCreateContainer(toIndex);
+        ////        }
 
-                if (PageTransition != null && (from != null || to != null))
-                {
-                    await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
-                }
-                else if (to != null)
-                {
-                    to.IsVisible = true;
-                }
+        ////        if (PageTransition != null && (from != null || to != null))
+        ////        {
+        ////            await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
+        ////        }
+        ////        else if (to != null)
+        ////        {
+        ////            to.IsVisible = true;
+        ////        }
 
-                if (from != null)
-                {
-                    if (IsVirtualized)
-                    {
-                        Panel!.Children.Remove(from);
-                        generator.Dematerialize(fromIndex, 1);
-                    }
-                    else
-                    {
-                        from.IsVisible = false;
-                    }
-                }
-            }
-        }
+        ////        if (from != null)
+        ////        {
+        ////            if (IsVirtualized)
+        ////            {
+        ////                Panel!.Children.Remove(from);
+        ////                generator.Dematerialize(fromIndex, 1);
+        ////            }
+        ////            else
+        ////            {
+        ////                from.IsVisible = false;
+        ////            }
+        ////        }
+        ////    }
+        ////}
 
-        private Control? GetOrCreateContainer(int index)
-        {
-            var container = ItemContainerGenerator.ContainerFromIndex(index);
+        ////private Control? GetOrCreateContainer(int index)
+        ////{
+        ////    var container = ItemContainerGenerator.ContainerFromIndex(index);
 
-            if (container == null && IsVirtualized)
-            {
-                var item = Items!.Cast<object>().ElementAt(index);
-                var materialized = ItemContainerGenerator.Materialize(index, item);
-                Panel!.Children.Add(materialized.ContainerControl);
-                container = materialized.ContainerControl;
-            }
+        ////    if (container == null && IsVirtualized)
+        ////    {
+        ////        var item = Items!.Cast<object>().ElementAt(index);
+        ////        var materialized = ItemContainerGenerator.Materialize(index, item);
+        ////        Panel!.Children.Add(materialized.ContainerControl);
+        ////        container = materialized.ContainerControl;
+        ////    }
 
-            return container;
-        }
+        ////    return container;
+        ////}
 
-        /// <summary>
-        /// Called when the <see cref="IsVirtualized"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-            }
-        }
+        /////// <summary>
+        /////// Called when the <see cref="IsVirtualized"/> property changes.
+        /////// </summary>
+        /////// <param name="e">The event args.</param>
+        ////private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
+        ////{
+        ////    if (Panel != null)
+        ////    {
+        ////        ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+        ////    }
+        ////}
 
-        /// <summary>
-        /// Called when the <see cref="SelectedIndex"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                if (_currentTransition == null)
-                {
-                    int fromIndex = (int)e.OldValue!;
-                    int toIndex = (int)e.NewValue!;
+        /////// <summary>
+        /////// Called when the <see cref="SelectedIndex"/> property changes.
+        /////// </summary>
+        /////// <param name="e">The event args.</param>
+        ////private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
+        ////{
+        ////    if (Panel != null)
+        ////    {
+        ////        if (_currentTransition == null)
+        ////        {
+        ////            int fromIndex = (int)e.OldValue!;
+        ////            int toIndex = (int)e.NewValue!;
 
-                    for (;;)
-                    {
-                        _currentTransition = MoveToPage(fromIndex, toIndex);
-                        await _currentTransition;
+        ////            for (;;)
+        ////            {
+        ////                _currentTransition = MoveToPage(fromIndex, toIndex);
+        ////                await _currentTransition;
 
-                        if (_queuedTransitionIndex != -1)
-                        {
-                            fromIndex = toIndex;
-                            toIndex = _queuedTransitionIndex;
-                            _queuedTransitionIndex = -1;
-                        }
-                        else
-                        {
-                            _currentTransition = null;
-                            break;
-                        }
-                    }
-                }
-                else
-                {
-                    _queuedTransitionIndex = (int)e.NewValue!;
-                }
-            }
-        }
+        ////                if (_queuedTransitionIndex != -1)
+        ////                {
+        ////                    fromIndex = toIndex;
+        ////                    toIndex = _queuedTransitionIndex;
+        ////                    _queuedTransitionIndex = -1;
+        ////                }
+        ////                else
+        ////                {
+        ////                    _currentTransition = null;
+        ////                    break;
+        ////                }
+        ////            }
+        ////        }
+        ////        else
+        ////        {
+        ////            _queuedTransitionIndex = (int)e.NewValue!;
+        ////        }
+        ////    }
+        ////}
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenter.cs b/src/Avalonia.Controls/Presenters/IItemsPresenter.cs
deleted file mode 100644
index dea8d4960e..0000000000
--- a/src/Avalonia.Controls/Presenters/IItemsPresenter.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-using System.Collections;
-using System.Collections.Specialized;
-using Avalonia.Metadata;
-
-namespace Avalonia.Controls.Presenters
-{
-    [NotClientImplementable]
-    public interface IItemsPresenter : IPresenter
-    {
-        IEnumerable? Items { get; set; }
-
-        Panel? Panel { get; }
-
-        void ItemsChanged(NotifyCollectionChangedEventArgs e);
-
-        void ScrollIntoView(int index);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
index a73d2abb5f..8bf190dbda 100644
--- a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
+++ b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
@@ -18,9 +18,9 @@ namespace Avalonia.Controls.Presenters
     public interface IItemsPresenterHost
     {
         /// <summary>
-        /// Registers an <see cref="IItemsPresenter"/> with a host control.
+        /// Registers an <see cref="ItemsPresenter"/> with a host control.
         /// </summary>
         /// <param name="presenter">The items presenter.</param>
-        void RegisterItemsPresenter(IItemsPresenter presenter);
+        void RegisterItemsPresenter(ItemsPresenter presenter);
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemContainerSync.cs b/src/Avalonia.Controls/Presenters/ItemContainerSync.cs
deleted file mode 100644
index 7346a074f3..0000000000
--- a/src/Avalonia.Controls/Presenters/ItemContainerSync.cs
+++ /dev/null
@@ -1,125 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Utils;
-
-namespace Avalonia.Controls.Presenters
-{
-    internal static class ItemContainerSync
-    {
-        public static void ItemsChanged(
-            ItemsPresenterBase owner,
-            IEnumerable? items,
-            NotifyCollectionChangedEventArgs e)
-        {
-            var generator = owner.ItemContainerGenerator;
-            var panel = owner.Panel;
-
-            if (panel == null)
-            {
-                return;
-            }
-
-            void Add()
-            {
-                if (e.NewStartingIndex + e.NewItems!.Count < items!.Count())
-                {
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems.Count);
-                }
-
-                AddContainers(owner, e.NewStartingIndex, e.NewItems);
-            }
-
-            void Remove()
-            {
-                RemoveContainers(panel, generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count));
-            }
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    Add();
-                    break;
-
-                case NotifyCollectionChangedAction.Remove:
-                    Remove();
-                    break;
-
-                case NotifyCollectionChangedAction.Replace:
-                    RemoveContainers(panel, generator.Dematerialize(e.OldStartingIndex, e.OldItems!.Count));
-                    var containers = AddContainers(owner, e.NewStartingIndex, e.NewItems!);
-
-                    var i = e.NewStartingIndex;
-
-                    foreach (var container in containers)
-                    {
-                        panel.Children[i++] = container.ContainerControl;
-                    }
-
-                    break;
-
-                case NotifyCollectionChangedAction.Move:
-                    Remove();
-                    Add();
-                    break;
-
-                case NotifyCollectionChangedAction.Reset:
-                    RemoveContainers(panel, generator.Clear());
-
-                    if (items != null)
-                    {
-                        AddContainers(owner, 0, items);
-                    }
-
-                    break;
-            }
-        }
-
-        private static IList<ItemContainerInfo> AddContainers(
-            ItemsPresenterBase owner,
-            int index,
-            IEnumerable items)
-        {
-            var generator = owner.ItemContainerGenerator;
-            var result = new List<ItemContainerInfo>();
-            var panel = owner.Panel;
-
-            foreach (var item in items)
-            {
-                var i = generator.Materialize(index++, item);
-
-                if (i.ContainerControl != null)
-                {
-                    if (i.Index < panel!.Children.Count)
-                    {
-                        // TODO: This will insert at the wrong place when there are null items.
-                        panel.Children.Insert(i.Index, i.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Add(i.ContainerControl);
-                    }
-                }
-
-                result.Add(i);
-            }
-
-            return result;
-        }
-
-        private static void RemoveContainers(
-            Panel panel,
-            IEnumerable<ItemContainerInfo> items)
-        {
-            foreach (var i in items)
-            {
-                if (i.ContainerControl != null)
-                {
-                    panel.Children.Remove(i.ContainerControl);
-                }
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
deleted file mode 100644
index 1f0f2a2f67..0000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
+++ /dev/null
@@ -1,303 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using System.Reactive.Linq;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Base class for classes which handle virtualization for an <see cref="ItemsPresenter"/>.
-    /// </summary>
-    internal abstract class ItemVirtualizer : IVirtualizingController, IDisposable
-    {
-        private double _crossAxisOffset;
-        private IDisposable? _subscriptions;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemVirtualizer"/> class.
-        /// </summary>
-        /// <param name="owner"></param>
-        public ItemVirtualizer(ItemsPresenter owner)
-        {
-            Owner = owner;
-            Items = owner.Items;
-            ItemCount = owner.Items.Count();
-
-            var panel = VirtualizingPanel;
-
-            if (panel != null)
-            {
-                _subscriptions = ((AvaloniaObject)panel).GetObservable(Panel.BoundsProperty)
-                    .Skip(1)
-                    .Subscribe(_ => InvalidateScroll());
-            }
-        }
-
-        /// <summary>
-        /// Gets the <see cref="ItemsPresenter"/> which owns the virtualizer.
-        /// </summary>
-        public ItemsPresenter Owner { get; }
-
-        /// <summary>
-        /// Gets the <see cref="IVirtualizingPanel"/> which will host the items.
-        /// </summary>
-        public IVirtualizingPanel? VirtualizingPanel => Owner.Panel as IVirtualizingPanel;
-
-        /// <summary>
-        /// Gets the items to display.
-        /// </summary>
-        public IEnumerable? Items { get; private set; }
-
-        /// <summary>
-        /// Gets the number of items in <see cref="Items"/>.
-        /// </summary>
-        public int ItemCount { get; private set; }
-
-        /// <summary>
-        /// Gets or sets the index of the first item displayed in the panel.
-        /// </summary>
-        public int FirstIndex { get; protected set; }
-
-        /// <summary>
-        /// Gets or sets the index of the first item beyond those displayed in the panel.
-        /// </summary>
-        public int NextIndex { get; protected set; }
-
-        /// <summary>
-        /// Gets a value indicating whether the items should be scroll horizontally or vertically.
-        /// </summary>
-        public bool Vertical => VirtualizingPanel?.ScrollDirection == Orientation.Vertical;
-
-        /// <summary>
-        /// Gets a value indicating whether logical scrolling is enabled.
-        /// </summary>
-        public abstract bool IsLogicalScrollEnabled { get; }
-
-        /// <summary>
-        /// Gets the value of the scroll extent.
-        /// </summary>
-        public abstract double ExtentValue { get; }
-
-        /// <summary>
-        /// Gets or sets the value of the current scroll offset.
-        /// </summary>
-        public abstract double OffsetValue { get; set; }
-
-        /// <summary>
-        /// Gets the value of the scrollable viewport.
-        /// </summary>
-        public abstract double ViewportValue { get; }
-
-        /// <summary>
-        /// Gets the <see cref="ExtentValue"/> as a <see cref="Size"/>.
-        /// </summary>
-        public Size Extent
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled && Owner.Panel is Panel panel)
-                {
-                    return Vertical ?
-                        new Size(panel.DesiredSize.Width, ExtentValue) :
-                        new Size(ExtentValue, panel.DesiredSize.Height);
-                }
-
-                return default;
-            }
-        }
-
-        /// <summary>
-        /// Gets the <see cref="ViewportValue"/> as a <see cref="Size"/>.
-        /// </summary>
-        public Size Viewport
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled && Owner.Panel is Panel panel)
-                {
-                    return Vertical ?
-                        new Size(panel.Bounds.Width, ViewportValue) :
-                        new Size(ViewportValue, panel.Bounds.Height);
-                }
-
-                return default;
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets the <see cref="OffsetValue"/> as a <see cref="Vector"/>.
-        /// </summary>
-        public Vector Offset
-        {
-            get
-            {
-                if (IsLogicalScrollEnabled)
-                {
-                    return Vertical ? new Vector(_crossAxisOffset, OffsetValue) : new Vector(OffsetValue, _crossAxisOffset);
-                }
-
-                return default;
-            }
-
-            set
-            {
-                if (!IsLogicalScrollEnabled)
-                {
-                    throw new NotSupportedException("Logical scrolling disabled.");
-                }
-
-                var oldCrossAxisOffset = _crossAxisOffset;
-
-                if (Vertical)
-                {
-                    OffsetValue = value.Y;
-                    _crossAxisOffset = value.X;
-                }
-                else
-                {
-                    OffsetValue = value.X;
-                    _crossAxisOffset = value.Y;
-                }
-
-                if (_crossAxisOffset != oldCrossAxisOffset)
-                {
-                    Owner.InvalidateArrange();
-                }
-            }
-        }
-        
-        /// <summary>
-        /// Creates an <see cref="ItemVirtualizer"/> based on an item presenter's 
-        /// <see cref="ItemVirtualizationMode"/>.
-        /// </summary>
-        /// <param name="owner">The items presenter.</param>
-        /// <returns>An <see cref="ItemVirtualizer"/>.</returns>
-        public static ItemVirtualizer? Create(ItemsPresenter owner)
-        {
-            if (owner.Panel == null)
-            {
-                return null;
-            }
-
-            var virtualizingPanel = owner.Panel as IVirtualizingPanel;
-            var scrollContentPresenter = owner.Parent as IScrollable;
-            ItemVirtualizer? result = null;
-
-            if (virtualizingPanel != null && scrollContentPresenter is object)
-            {
-                switch (owner.VirtualizationMode)
-                {
-                    case ItemVirtualizationMode.Simple:
-                        result = new ItemVirtualizerSimple(owner);
-                        break;
-                }
-            }
-
-            if (result == null)
-            {
-                result = new ItemVirtualizerNone(owner);
-            }
-
-            if (virtualizingPanel != null)
-            {
-                virtualizingPanel.Controller = result;
-            }
-
-            return result;
-        }
-
-        /// <summary>
-        /// Carries out a measure for the related <see cref="ItemsPresenter"/>.
-        /// </summary>
-        /// <param name="availableSize">The size available to the control.</param>
-        /// <returns>The desired size for the control.</returns>
-        public virtual Size MeasureOverride(Size availableSize)
-        {
-            Owner.Panel!.Measure(availableSize);
-            return Owner.Panel.DesiredSize;
-        }
-
-        /// <summary>
-        /// Carries out an arrange for the related <see cref="ItemsPresenter"/>.
-        /// </summary>
-        /// <param name="finalSize">The size available to the control.</param>
-        /// <returns>The actual size used.</returns>
-        public virtual Size ArrangeOverride(Size finalSize)
-        {
-            if (VirtualizingPanel != null)
-            {
-                VirtualizingPanel.CrossAxisOffset = _crossAxisOffset;
-                Owner.Panel!.Arrange(new Rect(finalSize));
-            }
-            else
-            {
-                var origin = Vertical ? new Point(-_crossAxisOffset, 0) : new Point(0, _crossAxisOffset);
-                Owner.Panel!.Arrange(new Rect(origin, finalSize));
-            }
-
-            return finalSize;
-        }
-
-        /// <inheritdoc/>
-        public virtual void UpdateControls()
-        {
-        }
-
-        /// <summary>
-        /// Gets the next control in the specified direction.
-        /// </summary>
-        /// <param name="direction">The movement direction.</param>
-        /// <param name="from">The control from which movement begins.</param>
-        /// <returns>The control.</returns>
-        public virtual Control? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            return null;
-        }
-
-        /// <summary>
-        /// Called when the items for the presenter change, either because 
-        /// <see cref="ItemsPresenterBase.Items"/> has been set, the items collection has been
-        /// modified, or the panel has been created.
-        /// </summary>
-        /// <param name="items">The items.</param>
-        /// <param name="e">A description of the change.</param>
-        public virtual void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            Items = items;
-            ItemCount = items?.Count() ?? 0;
-        }
-
-        /// <summary>
-        /// Scrolls the specified item into view.
-        /// </summary>
-        /// <param name="index">The index of the item.</param>
-        public virtual void ScrollIntoView(int index)
-        {
-        }
-
-        /// <inheritdoc/>
-        public virtual void Dispose()
-        {
-            _subscriptions?.Dispose();
-            _subscriptions = null;
-
-            if (VirtualizingPanel != null)
-            {
-                VirtualizingPanel.Controller = null;
-                VirtualizingPanel.Children.Clear();
-            }
-
-            Owner.ItemContainerGenerator.Clear();
-        }
-
-        /// <summary>
-        /// Invalidates the current scroll.
-        /// </summary>
-        protected void InvalidateScroll() => ((ILogicalScrollable)Owner).RaiseScrollInvalidated(EventArgs.Empty);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
deleted file mode 100644
index c1b6842b88..0000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizerNone.cs
+++ /dev/null
@@ -1,106 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Utils;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Represents an item virtualizer for an <see cref="ItemsPresenter"/> that doesn't actually
-    /// virtualize items - it just creates a container for every item.
-    /// </summary>
-    internal class ItemVirtualizerNone : ItemVirtualizer
-    {
-        public ItemVirtualizerNone(ItemsPresenter owner)
-            : base(owner)
-        {
-            if (Items != null && owner.Panel != null)
-            {
-                AddContainers(0, Items);
-            }
-        }
-
-        /// <inheritdoc/>
-        public override bool IsLogicalScrollEnabled => false;
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double ExtentValue
-        {
-            get { throw new NotSupportedException(); }
-        }
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double OffsetValue
-        {
-            get { throw new NotSupportedException(); }
-            set { throw new NotSupportedException(); }
-        }
-
-        /// <summary>
-        /// This property should never be accessed because <see cref="IsLogicalScrollEnabled"/> is
-        /// false.
-        /// </summary>
-        public override double ViewportValue
-        {
-            get { throw new NotSupportedException(); }
-        }
-
-        /// <inheritdoc/>
-        public override void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            base.ItemsChanged(items, e);
-            ItemContainerSync.ItemsChanged(Owner, items, e);
-            Owner.InvalidateMeasure();
-        }
-
-        /// <summary>
-        /// Scrolls the specified item into view.
-        /// </summary>
-        /// <param name="index">The index of the item.</param>
-        public override void ScrollIntoView(int index)
-        {
-            if (index != -1)
-            {
-                var container = Owner.ItemContainerGenerator.ContainerFromIndex(index);
-                container?.BringIntoView();
-            }
-        }
-
-        private IList<ItemContainerInfo> AddContainers(int index, IEnumerable items)
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var result = new List<ItemContainerInfo>();
-            var panel = Owner.Panel;
-
-            foreach (var item in items)
-            {
-                var i = generator.Materialize(index++, item);
-
-                if (i.ContainerControl != null)
-                {
-                    if (i.Index < panel!.Children.Count)
-                    {
-                        // TODO: This will insert at the wrong place when there are null items.
-                        panel.Children.Insert(i.Index, i.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Add(i.ContainerControl);
-                    }
-                }
-
-                result.Add(i);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
deleted file mode 100644
index f010c46c1a..0000000000
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizerSimple.cs
+++ /dev/null
@@ -1,606 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using System.Linq;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.Utilities;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Handles virtualization in an <see cref="ItemsPresenter"/> for
-    /// <see cref="ItemVirtualizationMode.Simple"/>.
-    /// </summary>
-    internal class ItemVirtualizerSimple : ItemVirtualizer
-    {
-        private int _anchor;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemVirtualizerSimple"/> class.
-        /// </summary>
-        /// <param name="owner"></param>
-        public ItemVirtualizerSimple(ItemsPresenter owner)
-            : base(owner)
-        {
-            // Don't need to add children here as UpdateControls should be called by the panel
-            // measure/arrange.
-        }
-
-        /// <inheritdoc/>
-        public override bool IsLogicalScrollEnabled => true;
-
-        /// <inheritdoc/>
-        public override double ExtentValue => ItemCount;
-
-        /// <inheritdoc/>
-        public override double OffsetValue
-        {
-            get
-            {
-                var offset = VirtualizingPanel.PixelOffset > 0 ? 1 : 0;
-                return FirstIndex + offset;
-            }
-
-            set
-            {
-                var panel = VirtualizingPanel;
-                var offset = VirtualizingPanel.PixelOffset > 0 ? 1 : 0;
-                var delta = (int)(value - (FirstIndex + offset));
-
-                if (delta != 0)
-                {
-                    var newLastIndex = (NextIndex - 1) + delta;
-
-                    if (newLastIndex < ItemCount)
-                    {
-                        if (panel.PixelOffset > 0)
-                        {
-                            panel.PixelOffset = 0;
-                            delta += 1;
-                        }
-
-                        if (delta != 0)
-                        {
-                            RecycleContainersForMove(delta);
-                        }
-                    }
-                    else
-                    {
-                        // We're moving to a partially obscured item at the end of the list so
-                        // offset the panel by the height of the first item.
-                        var firstIndex = ItemCount - panel.Children.Count;
-                        RecycleContainersForMove(firstIndex - FirstIndex);
-
-                        double pixelOffset;
-                        var child = panel.Children[0];
-
-                        if (child.IsArrangeValid)
-                        {
-                            pixelOffset = VirtualizingPanel.ScrollDirection == Orientation.Vertical ?
-                                                    child.Bounds.Height :
-                                                    child.Bounds.Width;
-                        }
-                        else
-                        {
-                            pixelOffset = VirtualizingPanel.ScrollDirection == Orientation.Vertical ?
-                                                    child.DesiredSize.Height :
-                                                    child.DesiredSize.Width;
-                        }
-
-                        panel.PixelOffset = pixelOffset;
-                    }
-                }
-            }
-        }
-
-        /// <inheritdoc/>
-        public override double ViewportValue
-        {
-            get
-            {
-                // If we can't fit the last item in the panel fully, subtract 1 from the viewport.
-                var overflow = VirtualizingPanel.PixelOverflow > 0 ? 1 : 0;
-                return VirtualizingPanel.Children.Count - overflow;
-            }
-        }
-
-        public new IVirtualizingPanel VirtualizingPanel => base.VirtualizingPanel!;
-
-        /// <inheritdoc/>
-        public override Size MeasureOverride(Size availableSize)
-        {
-            var scrollable = (ILogicalScrollable)Owner;
-            var visualRoot = Owner.GetVisualRoot();
-            var maxAvailableSize = (visualRoot as WindowBase)?.PlatformImpl?.MaxAutoSizeHint
-                 ?? (visualRoot as TopLevel)?.ClientSize;
-
-            // If infinity is passed as the available size and we're virtualized then we need to
-            // fill the available space, but to do that we *don't* want to materialize all our
-            // items! Take a look at the root of the tree for a MaxClientSize and use that as
-            // the available size.
-            if (VirtualizingPanel.ScrollDirection == Orientation.Vertical)
-            {
-                if (availableSize.Height == double.PositiveInfinity)
-                {
-                    if (maxAvailableSize.HasValue)
-                    {
-                        availableSize = availableSize.WithHeight(maxAvailableSize.Value.Height);
-                    }
-                }
-
-                if (scrollable.CanHorizontallyScroll)
-                {
-                    availableSize = availableSize.WithWidth(double.PositiveInfinity);
-                }
-            }
-            else
-            {
-                if (availableSize.Width == double.PositiveInfinity)
-                {
-                    if (maxAvailableSize.HasValue)
-                    {
-                        availableSize = availableSize.WithWidth(maxAvailableSize.Value.Width);
-                    }
-                }
-
-                if (scrollable.CanVerticallyScroll)
-                {
-                    availableSize = availableSize.WithHeight(double.PositiveInfinity);
-                }
-            }
-
-            Owner.Panel!.Measure(availableSize);
-            return Owner.Panel.DesiredSize;
-        }
-
-        /// <inheritdoc/>
-        public override void UpdateControls()
-        {
-            CreateAndRemoveContainers();
-            InvalidateScroll();
-        }
-
-        /// <inheritdoc/>
-        public override void ItemsChanged(IEnumerable? items, NotifyCollectionChangedEventArgs e)
-        {
-            base.ItemsChanged(items, e);
-
-            var panel = VirtualizingPanel;
-
-            if (items != null)
-            {
-                switch (e.Action)
-                {
-                    case NotifyCollectionChangedAction.Add:
-                        CreateAndRemoveContainers();
-
-                        if (e.NewStartingIndex < NextIndex)
-                        {
-                            RecycleContainers();
-                        }
-
-                        panel.ForceInvalidateMeasure();
-                        break;
-
-                    case NotifyCollectionChangedAction.Remove:
-                        if (e.OldStartingIndex < NextIndex ||
-                            panel.Children.Count > ItemCount)
-                        {
-                            RecycleContainersOnRemove();
-                        }
-
-                        panel.ForceInvalidateMeasure();
-                        break;
-
-                    case NotifyCollectionChangedAction.Move:
-                    case NotifyCollectionChangedAction.Replace:
-                        RecycleContainers();
-                        break;
-
-                    case NotifyCollectionChangedAction.Reset:
-                        RecycleContainersOnRemove();
-                        CreateAndRemoveContainers();
-                        panel.ForceInvalidateMeasure();
-                        break;
-                }
-            }
-            else
-            {
-                Owner.ItemContainerGenerator.Clear();
-                VirtualizingPanel.Children.Clear();
-                FirstIndex = NextIndex = 0;
-            }
-
-            // If we are scrolled to view a partially visible last item but controls were added
-            // then we need to return to a non-offset scroll position.
-            if (panel.PixelOffset != 0 && FirstIndex + panel.Children.Count < ItemCount)
-            {
-                panel.PixelOffset = 0;
-                RecycleContainersForMove(1);
-            }
-
-            InvalidateScroll();
-        }
-
-        public override Control? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var panel = VirtualizingPanel;
-            var itemIndex = generator.IndexFromContainer(from);
-            var vertical = VirtualizingPanel.ScrollDirection == Orientation.Vertical;
-
-            var newItemIndex = -1;
-
-            switch (direction)
-            {
-                case NavigationDirection.First:
-                    newItemIndex = 0;
-                    break;
-
-                case NavigationDirection.Last:
-                    newItemIndex = ItemCount - 1;
-                    break;
-
-                default:
-                    if (itemIndex == -1)
-                    {
-                        return null;
-                    }
-                    break;
-            }
-
-            switch (direction)
-            {
-                case NavigationDirection.Up:
-                    if (vertical)
-                    {
-                        newItemIndex = itemIndex - 1;
-                    }
-
-                    break;
-                case NavigationDirection.Down:
-                    if (vertical)
-                    {
-                        newItemIndex = itemIndex + 1;
-                    }
-
-                    break;
-
-                case NavigationDirection.Left:
-                    if (!vertical)
-                    {
-                        newItemIndex = itemIndex - 1;
-                    }
-                    break;
-
-                case NavigationDirection.Right:
-                    if (!vertical)
-                    {
-                        newItemIndex = itemIndex + 1;
-                    }
-                    break;
-
-                case NavigationDirection.PageUp:
-                    newItemIndex = Math.Max(0, itemIndex - (int)ViewportValue);
-                    break;
-
-                case NavigationDirection.PageDown:
-                    newItemIndex = Math.Min(ItemCount - 1, itemIndex + (int)ViewportValue);
-                    break;
-            }
-
-            return ScrollIntoViewCore(newItemIndex);
-        }
-
-        /// <inheritdoc/>
-        public override void ScrollIntoView(int index)
-        {
-            if (index != -1)
-            {
-                ScrollIntoViewCore(index);
-            }
-        }
-
-        /// <summary>
-        /// Creates and removes containers such that we have at most enough containers to fill
-        /// the panel.
-        /// </summary>
-        private void CreateAndRemoveContainers()
-        {
-            var generator = Owner.ItemContainerGenerator;
-            var panel = VirtualizingPanel;
-            var panelControl = (Control)panel;
-
-            if (!panel.IsFull && Items != null && panelControl.IsAttachedToVisualTree)
-            {
-                var index = NextIndex;
-                var step = 1;
-
-                while (!panel.IsFull && index >= 0)
-                {
-                    if (index >= ItemCount)
-                    {
-                        // We can fit more containers in the panel, but we're at the end of the
-                        // items. If we're scrolled to the top (FirstIndex == 0), then there are
-                        // no more items to create. Otherwise, go backwards adding containers to
-                        // the beginning of the panel.
-                        if (FirstIndex == 0)
-                        {
-                            break;
-                        }
-                        else
-                        {
-                            index = FirstIndex - 1;
-                            step = -1;
-                        }
-                    }
-
-                    var materialized = generator.Materialize(index, Items.ElementAt(index)!);
-
-                    if (step == 1)
-                    {
-                        panel.Children.Add(materialized.ContainerControl);
-                    }
-                    else
-                    {
-                        panel.Children.Insert(0, materialized.ContainerControl);
-                    }
-
-                    index += step;
-                }
-
-                if (step == 1)
-                {
-                    NextIndex = index;
-                }
-                else
-                {
-                    NextIndex = ItemCount;
-                    FirstIndex = index + 1;
-                }
-            }
-
-            if (panel.OverflowCount > 0)
-            {
-                if (_anchor <= FirstIndex)
-                {
-                    RemoveContainers(panel.OverflowCount);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Updates the containers in the panel to make sure they are displaying the correct item
-        /// based on <see cref="ItemVirtualizer.FirstIndex"/>.
-        /// </summary>
-        /// <remarks>
-        /// This method requires that <see cref="ItemVirtualizer.FirstIndex"/> + the number of
-        /// materialized containers is not more than <see cref="ItemVirtualizer.ItemCount"/>.
-        /// </remarks>
-        private void RecycleContainers()
-        {
-            var panel = VirtualizingPanel;
-            var generator = Owner.ItemContainerGenerator;
-            var containers = generator.Containers.ToList();
-            var itemIndex = FirstIndex;
-
-            foreach (var container in containers)
-            {
-                var item = Items!.ElementAt(itemIndex)!;
-
-                if (!object.Equals(container.Item, item))
-                {
-                    if (!generator.TryRecycle(itemIndex, itemIndex, item))
-                    {
-                        throw new NotImplementedException();
-                    }
-                }
-
-                ++itemIndex;
-            }
-        }
-
-        /// <summary>
-        /// Recycles containers when a move occurs.
-        /// </summary>
-        /// <param name="delta">The delta of the move.</param>
-        /// <remarks>
-        /// If the move is less than a page, then this method moves the containers for the items
-        /// that are still visible to the correct place, and recycles and moves the others. For
-        /// example: if there are 20 items and 10 containers visible and the user scrolls 5
-        /// items down, then the bottom 5 containers will be moved to the top and the top 5 will
-        /// be moved to the bottom and recycled to display the newly visible item. Updates 
-        /// <see cref="ItemVirtualizer.FirstIndex"/> and <see cref="ItemVirtualizer.NextIndex"/>
-        /// with their new values.
-        /// </remarks>
-        private void RecycleContainersForMove(int delta)
-        {
-            var panel = VirtualizingPanel;
-            var generator = Owner.ItemContainerGenerator;
-
-            //validate delta it should never overflow last index or generate index < 0 
-            delta = MathUtilities.Clamp(delta, -FirstIndex, ItemCount - FirstIndex - panel.Children.Count);
-
-            var sign = delta < 0 ? -1 : 1;
-            var count = Math.Min(Math.Abs(delta), panel.Children.Count);
-            var move = count < panel.Children.Count;
-            var first = delta < 0 && move ? panel.Children.Count + delta : 0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                var oldItemIndex = FirstIndex + first + i;
-                var newItemIndex = oldItemIndex + delta + ((panel.Children.Count - count) * sign);
-
-                var item = Items!.ElementAt(newItemIndex)!;
-
-                if (!generator.TryRecycle(oldItemIndex, newItemIndex, item))
-                {
-                    throw new NotImplementedException();
-                }
-            }
-
-            if (move)
-            {
-                if (delta > 0)
-                {
-                    panel.Children.MoveRange(first, count, panel.Children.Count);
-                }
-                else
-                {
-                    panel.Children.MoveRange(first, count, 0);
-                }
-            }
-
-            FirstIndex += delta;
-            NextIndex += delta;
-        }
-
-        /// <summary>
-        /// Recycles containers due to items being removed.
-        /// </summary>
-        private void RecycleContainersOnRemove()
-        {
-            var panel = VirtualizingPanel;
-
-            if (NextIndex <= ItemCount)
-            {
-                // Items have been removed but FirstIndex..NextIndex is still a valid range in the
-                // items, so just recycle the containers to adapt to the new state.
-                RecycleContainers();
-            }
-            else
-            {
-                // Items have been removed and now the range FirstIndex..NextIndex goes out of 
-                // the item bounds. Remove any excess containers, try to scroll up and then recycle
-                // the containers to make sure they point to the correct item.
-                var newFirstIndex = Math.Max(0, FirstIndex - (NextIndex - ItemCount));
-                var delta = newFirstIndex - FirstIndex;
-                var newNextIndex = NextIndex + delta;
-
-                if (newNextIndex > ItemCount)
-                {
-                    RemoveContainers(newNextIndex - ItemCount);
-                }
-
-                if (delta != 0)
-                {
-                    RecycleContainersForMove(delta);
-                }
-
-                RecycleContainers();
-            }
-        }
-
-        /// <summary>
-        /// Removes the specified number of containers from the end of the panel and updates
-        /// <see cref="ItemVirtualizer.NextIndex"/>.
-        /// </summary>
-        /// <param name="count">The number of containers to remove.</param>
-        private void RemoveContainers(int count)
-        {
-            var index = VirtualizingPanel.Children.Count - count;
-
-            VirtualizingPanel.Children.RemoveRange(index, count);
-            Owner.ItemContainerGenerator.Dematerialize(FirstIndex + index, count);
-            NextIndex -= count;
-        }
-
-        /// <summary>
-        /// Scrolls the item with the specified index into view.
-        /// </summary>
-        /// <param name="index">The item index.</param>
-        /// <returns>The container that was brought into view.</returns>
-        private Control? ScrollIntoViewCore(int index)
-        {
-            var panel = VirtualizingPanel;
-            var panelControl = (Control)panel;
-            var generator = Owner.ItemContainerGenerator;
-            var newOffset = -1.0;
-
-            //better not trigger any container generation/recycle while  or layout stuff
-            //before panel is attached/visible
-            if (!panelControl.IsAttachedToVisualTree)
-            {
-                return null;
-            }
-
-            if (!panelControl.IsMeasureValid && panelControl.PreviousMeasure.HasValue)
-            {
-                //before any kind of scrolling we need to make sure panel measure is valid
-                //or we risk get panel into not valid state
-                //we make a preemptive quick measure so scrolling is valid
-                panelControl.Measure(panelControl.PreviousMeasure.Value);
-            }
-
-            if (index >= 0 && index < ItemCount)
-            {
-                if (index <= FirstIndex)
-                {
-                    newOffset = index;
-                }
-                else if (index >= NextIndex)
-                {
-                    newOffset = index - Math.Ceiling(ViewportValue - 1);
-                }
-
-                if (newOffset != -1)
-                {
-                    OffsetValue = newOffset;
-                }
-
-                var container = generator.ContainerFromIndex(index);
-                var layoutManager = (Owner.GetVisualRoot() as ILayoutRoot)?.LayoutManager;
-
-                // We need to do a layout here because it's possible that the container we moved to
-                // is only partially visible due to differing item sizes. If the container is only 
-                // partially visible, scroll again. Don't do this if there's no layout manager:
-                // it means we're running a unit test.
-                if (container != null && layoutManager != null)
-                {
-                    _anchor = index;
-                    layoutManager.ExecuteLayoutPass();
-                    _anchor = -1;
-
-                    if (newOffset != -1 && newOffset != OffsetValue)
-                    {
-                        OffsetValue = newOffset;
-                    }
-                    
-                    if (panel.ScrollDirection == Orientation.Vertical)
-                    {
-                        if (container.Bounds.Y < panelControl.Bounds.Y || container.Bounds.Bottom > panelControl.Bounds.Bottom)
-                        {
-                            OffsetValue += 1;
-                        }
-                    }
-                    else
-                    {
-                        if (container.Bounds.X < panelControl.Bounds.X || container.Bounds.Right > panelControl.Bounds.Right)
-                        {
-                            OffsetValue += 1;
-                        }
-                    }
-                }
-
-                return container;
-            }
-
-            return null;
-        }
-
-        /// <summary>
-        /// Ensures an offset value is within the value range.
-        /// </summary>
-        /// <param name="value">The value.</param>
-        /// <returns>The coerced value.</returns>
-        private double CoerceOffset(double value)
-        {
-            var max = Math.Max(ExtentValue - ViewportValue, 0);
-            return MathUtilities.Clamp(value, 0, max);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 924c4567f6..2a52e00d67 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,179 +1,88 @@
 using System;
+using System.Collections;
 using System.Collections.Specialized;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using static Avalonia.Utilities.MathUtilities;
+using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
 {
     /// <summary>
-    /// Displays items inside an <see cref="ItemsControl"/>.
+    /// Presents items inside an <see cref="Avalonia.Controls.ItemsControl"/>.
     /// </summary>
-    public class ItemsPresenter : ItemsPresenterBase, ILogicalScrollable
+    public class ItemsPresenter : Control
     {
         /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// Defines the <see cref="ItemsPanel"/> property.
         /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.Register<ItemsPresenter, ItemVirtualizationMode>(
-                nameof(VirtualizationMode),
-                defaultValue: ItemVirtualizationMode.None);
+        public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
+            ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
-        private bool _canHorizontallyScroll;
-        private bool _canVerticallyScroll;
-        private EventHandler? _scrollInvalidated;
+        private ItemsPresenterContainerGenerator? _generator;
 
         /// <summary>
-        /// Initializes static members of the <see cref="ItemsPresenter"/> class.
+        /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
-        static ItemsPresenter()
+        public ITemplate<Panel> ItemsPanel
         {
-            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
-                typeof(ItemsPresenter),
-                KeyboardNavigationMode.Once);
-
-            VirtualizationModeProperty.Changed
-                .AddClassHandler<ItemsPresenter>((x, e) => x.VirtualizationModeChanged(e));
+            get => GetValue(ItemsPanelProperty);
+            set => SetValue(ItemsPanelProperty, value);
         }
 
         /// <summary>
-        /// Gets or sets the virtualization mode for the items.
+        /// Gets the panel used to display the items.
         /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
+        public Panel? Panel { get; private set; }
 
         /// <summary>
-        /// Gets or sets a value indicating whether the content can be scrolled horizontally.
+        /// Gets the owner <see cref="ItemsControl"/>.
         /// </summary>
-        bool ILogicalScrollable.CanHorizontallyScroll
-        {
-            get { return _canHorizontallyScroll; }
-            set
-            {
-                _canHorizontallyScroll = value;
-                InvalidateMeasure();
-            }
-        }
+        internal ItemsControl? ItemsControl { get; private set; }
 
-        /// <summary>
-        /// Gets or sets a value indicating whether the content can be scrolled horizontally.
-        /// </summary>
-        bool ILogicalScrollable.CanVerticallyScroll
+        public override sealed void ApplyTemplate()
         {
-            get { return _canVerticallyScroll; }
-            set
+            if (Panel is null)
             {
-                _canVerticallyScroll = value;
-                InvalidateMeasure();
+                Panel = ItemsPanel.Build();
+                Panel.SetValue(TemplatedParentProperty, TemplatedParent);
+                LogicalChildren.Add(Panel);
+                VisualChildren.Add(Panel);
+                CreateGeneratorIfSimplePanel();
             }
         }
-        /// <inheritdoc/>
-        bool ILogicalScrollable.IsLogicalScrollEnabled
-        {
-            get { return Virtualizer?.IsLogicalScrollEnabled ?? false; }
-        }
-
-        /// <inheritdoc/>
-        Size IScrollable.Extent => Virtualizer?.Extent ?? Size.Empty;
 
-        /// <inheritdoc/>
-        Vector IScrollable.Offset
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
-            get { return Virtualizer?.Offset ?? new Vector(); }
-            set
+            base.OnPropertyChanged(change);
+
+            if (change.Property == TemplatedParentProperty)
             {
-                if (Virtualizer != null)
+                _generator?.Dispose();
+                _generator = null;
+
+                if (change.NewValue is ItemsControl itemsControl)
                 {
-                    Virtualizer.Offset = CoerceOffset(value);
+                    ItemsControl = itemsControl;
+                    ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
+                    CreateGeneratorIfSimplePanel();
                 }
             }
+            else if (change.Property == ItemsPanelProperty)
+            {
+                _generator?.Dispose();
+                _generator = null;
+                LogicalChildren.Clear();
+                VisualChildren.Clear();
+                Panel = null;
+                InvalidateMeasure();
+            }
         }
 
-        /// <inheritdoc/>
-        Size IScrollable.Viewport => Virtualizer?.Viewport ?? Bounds.Size;
-
-        /// <inheritdoc/>
-        event EventHandler? ILogicalScrollable.ScrollInvalidated
-        {
-            add => _scrollInvalidated += value;
-            remove => _scrollInvalidated -= value;
-        }
-
-        /// <inheritdoc/>
-        Size ILogicalScrollable.ScrollSize => new Size(ScrollViewer.DefaultSmallChange, 1);
-
-        /// <inheritdoc/>
-        Size ILogicalScrollable.PageScrollSize => Virtualizer?.Viewport ?? new Size(16, 16);
-
-        internal ItemVirtualizer? Virtualizer { get; private set; }
-
-        /// <inheritdoc/>
-        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
-        {
-            return false;
-        }
-
-        /// <inheritdoc/>
-        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            return Virtualizer?.GetControlInDirection(direction, from);
-        }
-
-        /// <inheritdoc/>
-        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e)
-        {
-            _scrollInvalidated?.Invoke(this, e);
-        }
-
-        public override void ScrollIntoView(int index)
-        {
-            Virtualizer?.ScrollIntoView(index);
-        }
-
-        /// <inheritdoc/>
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            return Virtualizer?.MeasureOverride(availableSize) ?? Size.Empty;
-        }
-
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            return Virtualizer?.ArrangeOverride(finalSize) ?? Size.Empty;
-        }
-
-        /// <inheritdoc/>
-        protected override void PanelCreated(Panel panel)
-        {
-            Virtualizer?.Dispose();
-            Virtualizer = ItemVirtualizer.Create(this);
-            _scrollInvalidated?.Invoke(this, EventArgs.Empty);
-
-            KeyboardNavigation.SetTabNavigation(
-                (InputElement)panel,
-                KeyboardNavigation.GetTabNavigation(this));
-        }
-
-        protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            Virtualizer?.ItemsChanged(Items, e);
-        }
-
-        private Vector CoerceOffset(Vector value)
+        private void CreateGeneratorIfSimplePanel()
         {
-            var scrollable = (ILogicalScrollable)this;
-            var maxX = Math.Max(scrollable.Extent.Width - scrollable.Viewport.Width, 0);
-            var maxY = Math.Max(scrollable.Extent.Height - scrollable.Viewport.Height, 0);
-            return new Vector(Clamp(value.X, 0, maxX), Clamp(value.Y, 0, maxY));
-        }
+            if (ItemsControl is null || Panel is null || Panel is IVirtualizingPanel)
+                return;
 
-        private void VirtualizationModeChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            Virtualizer?.Dispose();
-            Virtualizer = ItemVirtualizer.Create(this);
-            _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+            _generator?.Dispose();
+            _generator = new(this);
         }
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
deleted file mode 100644
index 38a2a5722c..0000000000
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterBase.cs
+++ /dev/null
@@ -1,308 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Templates;
-using Avalonia.Controls.Utils;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Base class for controls that present items inside an <see cref="ItemsControl"/>.
-    /// </summary>
-    public abstract class ItemsPresenterBase : Control, IItemsPresenter, IChildIndexProvider
-    {
-        /// <summary>
-        /// Defines the <see cref="Items"/> property.
-        /// </summary>
-        public static readonly DirectProperty<ItemsPresenterBase, IEnumerable?> ItemsProperty =
-            ItemsControl.ItemsProperty.AddOwner<ItemsPresenterBase>(o => o.Items, (o, v) => o.Items = v);
-
-        /// <summary>
-        /// Defines the <see cref="ItemsPanel"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
-            ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenterBase>();
-
-        /// <summary>
-        /// Defines the <see cref="ItemTemplate"/> property.
-        /// </summary>
-        public static readonly StyledProperty<IDataTemplate?> ItemTemplateProperty =
-            ItemsControl.ItemTemplateProperty.AddOwner<ItemsPresenterBase>();
-
-        /// <summary>
-        /// Defines the <see cref="DisplayMemberBinding" /> property
-        /// </summary>
-        public static readonly StyledProperty<IBinding?> DisplayMemberBindingProperty =
-            ItemsControl.DisplayMemberBindingProperty.AddOwner<ItemsPresenterBase>();
-        
-        private IEnumerable? _items;
-        private IDisposable? _itemsSubscription;
-        private bool _createdPanel;
-        private IItemContainerGenerator? _generator;
-        private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
-
-        /// <summary>
-        /// Initializes static members of the <see cref="ItemsPresenter"/> class.
-        /// </summary>
-        static ItemsPresenterBase()
-        {
-            TemplatedParentProperty.Changed.AddClassHandler<ItemsPresenterBase>((x,e) => x.TemplatedParentChanged(e));
-        }
-
-        /// <summary>
-        /// Gets or sets the items to be displayed.
-        /// </summary>
-        public IEnumerable? Items
-        {
-            get
-            {
-                return _items;
-            }
-
-            set
-            {
-                _itemsSubscription?.Dispose();
-                _itemsSubscription = null;
-
-                if (!IsHosted && _createdPanel && value is INotifyCollectionChanged incc)
-                {
-                    _itemsSubscription = incc.WeakSubscribe(ItemsCollectionChanged);
-                }
-
-                SetAndRaise(ItemsProperty, ref _items, value);
-
-                if (_createdPanel)
-                {
-                    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-                }
-            }
-        }
-
-        /// <summary>
-        /// Gets the item container generator.
-        /// </summary>
-        public IItemContainerGenerator ItemContainerGenerator
-        {
-            get
-            {
-                if (_generator == null)
-                {
-                    _generator = CreateItemContainerGenerator();
-                }
-
-                return _generator;
-            }
-
-            internal set
-            {
-                if (_generator != null)
-                {
-                    throw new InvalidOperationException("ItemContainerGenerator already created.");
-                }
-
-                _generator = value;
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
-        /// </summary>
-        public ITemplate<Panel> ItemsPanel
-        {
-            get { return GetValue(ItemsPanelProperty); }
-            set { SetValue(ItemsPanelProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
-        /// </summary>
-        public IDataTemplate? ItemTemplate
-        {
-            get { return GetValue(ItemTemplateProperty); }
-            set { SetValue(ItemTemplateProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the <see cref="IBinding"/> to use for binding to the display member of each item.
-        /// </summary>
-        public IBinding? DisplayMemberBinding
-        {
-            get { return GetValue(DisplayMemberBindingProperty); }
-            set { SetValue(DisplayMemberBindingProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets the panel used to display the items.
-        /// </summary>
-        public Panel? Panel
-        {
-            get;
-            private set;
-        }
-
-        protected bool IsHosted => TemplatedParent is IItemsPresenterHost;
-
-        event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
-        {
-            add => _childIndexChanged += value;
-            remove => _childIndexChanged -= value;
-        }
-
-        /// <inheritdoc/>
-        public override sealed void ApplyTemplate()
-        {
-            if (!_createdPanel)
-            {
-                CreatePanel();
-            }
-        }
-
-        /// <inheritdoc/>
-        public virtual void ScrollIntoView(int index)
-        {
-        }
-
-        /// <inheritdoc/>
-        void IItemsPresenter.ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            if (Panel != null)
-            {
-                ItemsChanged(e);
-
-                _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-            }
-        }
-
-        /// <summary>
-        /// Creates the <see cref="ItemContainerGenerator"/> for the control.
-        /// </summary>
-        /// <returns>
-        /// An <see cref="IItemContainerGenerator"/> or null.
-        /// </returns>
-        protected virtual IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            var i = TemplatedParent as ItemsControl;
-            var result = i?.ItemContainerGenerator;
-
-            if (result == null)
-            {
-                result = new ItemContainerGenerator(this);
-                result.ItemTemplate = ItemTemplate;
-                result.DisplayMemberBinding = DisplayMemberBinding;
-            }
-
-            result.Materialized += ContainerActionHandler;
-            result.Dematerialized += ContainerActionHandler;
-            result.Recycled += ContainerActionHandler;
-
-            return result;
-        }
-
-        private void ContainerActionHandler(object? sender, ItemContainerEventArgs e)
-        {
-            for (var i = 0; i < e.Containers.Count; i++)
-            {
-                _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(e.Containers[i].ContainerControl));
-            }
-        }
-
-        /// <inheritdoc/>
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            Panel!.Measure(availableSize);
-            return Panel.DesiredSize;
-        }
-
-        /// <inheritdoc/>
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            Panel!.Arrange(new Rect(finalSize));
-            return finalSize;
-        }
-
-        /// <summary>
-        /// Called when the <see cref="Panel"/> is created.
-        /// </summary>
-        /// <param name="panel">The panel.</param>
-        protected virtual void PanelCreated(Panel panel)
-        {
-        }
-
-        /// <summary>
-        /// Called when the items for the presenter change, either because <see cref="Items"/>
-        /// has been set, the items collection has been modified, or the panel has been created.
-        /// </summary>
-        /// <param name="e">A description of the change.</param>
-        /// <remarks>
-        /// The panel is guaranteed to be created when this method is called.
-        /// </remarks>
-        protected virtual void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        {
-            ItemContainerSync.ItemsChanged(this, Items, e);
-        }
-
-        /// <summary>
-        /// Creates the <see cref="Panel"/> when <see cref="ApplyTemplate"/> is called for the first
-        /// time.
-        /// </summary>
-        private void CreatePanel()
-        {
-            Panel = ItemsPanel.Build();
-            Panel.SetValue(TemplatedParentProperty, TemplatedParent);
-
-            LogicalChildren.Clear();
-            VisualChildren.Clear();
-            LogicalChildren.Add(Panel);
-            VisualChildren.Add(Panel);
-
-            _createdPanel = true;
-
-            if (!IsHosted && _itemsSubscription == null && Items is INotifyCollectionChanged incc)
-            {
-                _itemsSubscription = incc.WeakSubscribe(ItemsCollectionChanged);
-            }
-
-            PanelCreated(Panel);
-        }
-
-        /// <summary>
-        /// Called when the <see cref="Items"/> collection changes.
-        /// </summary>
-        /// <param name="sender">The sender.</param>
-        /// <param name="e">The event args.</param>
-        private void ItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
-        {
-            if (_createdPanel)
-            {
-                ItemsChanged(e);
-            }
-        }
-
-        private void TemplatedParentChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            (e.NewValue as IItemsPresenterHost)?.RegisterItemsPresenter(this);
-        }
-
-        int IChildIndexProvider.GetChildIndex(ILogical child)
-        {
-            if (child is Control control && ItemContainerGenerator is { } generator)
-            {
-                var index = ItemContainerGenerator.IndexFromContainer(control);
-
-                return index;
-            }
-
-            return -1;
-        }
-
-        bool IChildIndexProvider.TryGetTotalCount(out int count)
-        {
-            return Items.TryGetCountFast(out count);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
new file mode 100644
index 0000000000..4c2bd35f5a
--- /dev/null
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
@@ -0,0 +1,108 @@
+using System;
+using System.Collections;
+using System.Collections.Specialized;
+using System.Diagnostics;
+
+namespace Avalonia.Controls.Presenters
+{
+    /// <summary>
+    /// Generates containers for <see cref="ItemsPresenter"/>s that have non-virtualizing panels.
+    /// </summary>
+    internal class ItemsPresenterContainerGenerator : IDisposable
+    {
+        private static NotifyCollectionChangedEventArgs s_Reset = new(NotifyCollectionChangedAction.Reset);
+        private ItemsPresenter _presenter;
+
+        public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
+        {
+            Debug.Assert(presenter.ItemsControl is not null);
+            Debug.Assert(presenter.Panel is not null or IVirtualizingPanel);
+            
+            _presenter = presenter;
+            _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
+
+            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged += OnItemsChanged;
+
+            OnItemsChanged(null, s_Reset);
+        }
+
+        public void Dispose()
+        {
+            _presenter.ItemsControl!.PropertyChanged -= OnItemsControlPropertyChanged;
+
+            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged -= OnItemsChanged;
+
+            _presenter.Panel!.Children.Clear();
+        }
+
+        private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            if (e.Property == ItemsControl.ItemsProperty)
+            {
+                if (e.OldValue is INotifyCollectionChanged inccOld)
+                    inccOld.CollectionChanged -= OnItemsChanged;
+                OnItemsChanged(null, s_Reset);
+                if (e.NewValue is INotifyCollectionChanged inccNew)
+                    inccNew.CollectionChanged += OnItemsChanged;
+            }
+        }
+
+        private void OnItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (_presenter.ItemsControl?.Items is null || _presenter.Panel is null)
+                return;
+
+            var generator = _presenter.ItemsControl.ItemContainerGenerator;
+            var panel = _presenter.Panel;
+
+            void Add(int index, IEnumerable items)
+            {
+                var i = index;
+
+                foreach (var item in items)
+                {
+                    var c = generator.Materialize(i, item);
+                    panel.Children.Insert(i++, c.ContainerControl);
+                }
+            }
+            
+            void Remove(int index, int count)
+            {
+                for (var i = 0; i < count; ++i)
+                    panel.Children.RemoveAt(i + index);
+            }
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Move:
+                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    generator.Clear();
+                    panel.Children.Clear();
+                    if (_presenter.ItemsControl.Items is { } items)
+                        Add(0, items);
+                    break;
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 44fa78ac21..7f8d8f098a 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -373,7 +373,7 @@ namespace Avalonia.Controls.Primitives
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        public void ScrollIntoView(int index) => Presenter?.ScrollIntoView(index);
+        public void ScrollIntoView(int index) => throw new NotImplementedException(); ////Presenter?.ScrollIntoView(index);
 
         /// <summary>
         /// Scrolls the specified item into view.
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index f7cf1b922d..ea94440bf1 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,252 +1,20 @@
 using System;
-using System.Collections.Specialized;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
-    public class VirtualizingStackPanel : StackPanel, IVirtualizingPanel
+    public class VirtualizingStackPanel : StackPanel
     {
-        private Size _availableSpace;
-        private double _takenSpace;
-        private int _canBeRemoved;
-        private double _averageItemSize;
-        private int _averageCount;
-        private double _pixelOffset;
-        private double _crossAxisOffset;
-        private bool _forceRemeasure;
+        /// <summary>
+        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// </summary>
+        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
+            AvaloniaProperty.Register<VirtualizingStackPanel, ItemVirtualizationMode>(
+                nameof(VirtualizationMode));
 
-        bool IVirtualizingPanel.IsFull
+        public ItemVirtualizationMode VirtualizationMode
         {
-            get
-            {
-                return Orientation == Orientation.Horizontal ?
-                    _takenSpace >= _availableSpace.Width :
-                    _takenSpace >= _availableSpace.Height;
-            }
-        }
-
-        IVirtualizingController? IVirtualizingPanel.Controller { get; set; }
-        int IVirtualizingPanel.OverflowCount => _canBeRemoved;
-        Orientation IVirtualizingPanel.ScrollDirection => Orientation;
-        double IVirtualizingPanel.AverageItemSize => _averageItemSize;
-
-        double IVirtualizingPanel.PixelOverflow
-        {
-            get
-            {
-                var bounds = Orientation == Orientation.Horizontal ?
-                    _availableSpace.Width : _availableSpace.Height;
-                return Math.Max(0, _takenSpace - bounds);
-            }
-        }
-
-        double IVirtualizingPanel.PixelOffset
-        {
-            get { return _pixelOffset; }
-
-            set
-            {
-                if (_pixelOffset != value)
-                {
-                    _pixelOffset = value;
-                    InvalidateArrange();
-                }
-            }
-        }
-
-        double IVirtualizingPanel.CrossAxisOffset
-        {
-            get { return _crossAxisOffset; }
-
-            set
-            {
-                if (_crossAxisOffset != value)
-                {
-                    _crossAxisOffset = value;
-                    InvalidateArrange();
-                }
-            }
-        }
-
-        private IVirtualizingController? Controller => ((IVirtualizingPanel)this).Controller;
-
-        void IVirtualizingPanel.ForceInvalidateMeasure()
-        {
-            InvalidateMeasure();
-            _forceRemeasure = true;
-        }
-
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            if (_forceRemeasure || availableSize != PreviousMeasure)
-            {
-                _forceRemeasure = false;
-                _availableSpace = availableSize;
-                Controller?.UpdateControls();
-            }
-
-            return base.MeasureOverride(availableSize);
-        }
-
-        protected override Size ArrangeOverride(Size finalSize)
-        {
-            _availableSpace = finalSize;
-            _canBeRemoved = 0;
-            _takenSpace = 0;
-            _averageItemSize = 0;
-            _averageCount = 0;
-            var result = base.ArrangeOverride(finalSize);
-            _takenSpace += _pixelOffset;
-            Controller?.UpdateControls();
-            return result;
-        }
-
-        protected override void ChildrenChanged(object? sender, NotifyCollectionChangedEventArgs e)
-        {
-            base.ChildrenChanged(sender, e);
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    foreach (Control control in e.NewItems!)
-                    {
-                        UpdateAdd(control);
-                    }
-
-                    break;
-
-                case NotifyCollectionChangedAction.Remove:
-                    foreach (Control control in e.OldItems!)
-                    {
-                        UpdateRemove(control);
-                    }
-
-                    break;
-            }
-        }
-
-        protected override IInputElement? GetControlInDirection(NavigationDirection direction, Control? from)
-        {
-            var logicalScrollable = Parent as ILogicalScrollable;
-
-            if (logicalScrollable?.IsLogicalScrollEnabled == true)
-            {
-                return logicalScrollable.GetControlInDirection(direction, from);
-            }
-            else
-            {
-                return base.GetControlInDirection(direction, from);
-            }
-        }
-
-        internal override void ArrangeChild(
-            Control child,
-            Rect rect,
-            Size panelSize,
-            Orientation orientation)
-        {
-            if (orientation == Orientation.Vertical)
-            {
-                rect = new Rect(
-                    rect.X - _crossAxisOffset,
-                    rect.Y - _pixelOffset,
-                    rect.Width,
-                    rect.Height);
-                child.Arrange(rect);
-
-                if (rect.Y >= _availableSpace.Height)
-                {
-                    ++_canBeRemoved;
-                }
-
-                if (rect.Bottom >= _takenSpace)
-                {
-                    _takenSpace = rect.Bottom;
-                }
-
-                AddToAverageItemSize(rect.Height);
-            }
-            else
-            {
-                rect = new Rect(
-                    rect.X - _pixelOffset,
-                    rect.Y - _crossAxisOffset,
-                    rect.Width,
-                    rect.Height);
-                child.Arrange(rect);
-
-                if (rect.X >= _availableSpace.Width)
-                {
-                    ++_canBeRemoved;
-                }
-
-                if (rect.Right >= _takenSpace)
-                {
-                    _takenSpace = rect.Right;
-                }
-
-                AddToAverageItemSize(rect.Width);
-            }
-        }
-
-        private void UpdateAdd(Control child)
-        {
-            var bounds = Bounds;
-            var spacing = Spacing;
-
-            child.Measure(_availableSpace);
-            ++_averageCount;
-
-            if (Orientation == Orientation.Vertical)
-            {
-                var height = child.DesiredSize.Height;
-                _takenSpace += height + spacing;
-                AddToAverageItemSize(height);
-            }
-            else
-            {
-                var width = child.DesiredSize.Width;
-                _takenSpace += width + spacing;
-                AddToAverageItemSize(width);
-            }
-        }
-
-        private void UpdateRemove(Control child)
-        {
-            var bounds = Bounds;
-            var spacing = Spacing;
-
-            if (Orientation == Orientation.Vertical)
-            {
-                var height = child.DesiredSize.Height;
-                _takenSpace -= height + spacing;
-                RemoveFromAverageItemSize(height);
-            }
-            else
-            {
-                var width = child.DesiredSize.Width;
-                _takenSpace -= width + spacing;
-                RemoveFromAverageItemSize(width);
-            }
-
-            if (_canBeRemoved > 0)
-            {
-                --_canBeRemoved;
-            }
-        }
-
-        private void AddToAverageItemSize(double value)
-        {
-            ++_averageCount;
-            _averageItemSize += (value - _averageItemSize) / _averageCount;
-        }
-
-        private void RemoveFromAverageItemSize(double value)
-        {
-            _averageItemSize = ((_averageItemSize * _averageCount) - value) / (_averageCount - 1);
-            --_averageCount;
+            get => GetValue(VirtualizationModeProperty);
+            set => SetValue(VirtualizationModeProperty, value);
         }
     }
 }
diff --git a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
index 2cac701e1b..1dab50052d 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
@@ -8,7 +8,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <CarouselPresenter IsVirtualized="{TemplateBinding IsVirtualized}"
-                             Items="{TemplateBinding Items}"
                              ItemsPanel="{TemplateBinding ItemsPanel}"
                              Margin="{TemplateBinding Padding}"
                              SelectedIndex="{TemplateBinding SelectedIndex}"
diff --git a/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml b/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
index 24d9d21df8..bc36ad987e 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ComboBox.xaml
@@ -128,11 +128,8 @@
                 <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                               VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  Items="{TemplateBinding Items}"
                                   Margin="{DynamicResource ComboBoxDropdownContentMargin}"
-                                  ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                                  ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
             </Popup>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml b/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
index fdd79ed736..f6900f785f 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ContextMenu.xaml
@@ -56,9 +56,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                             KeyboardNavigation.TabNavigation="Continue"
                             Grid.IsSharedSizeScope="True" />
diff --git a/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml b/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
index fc85b7b9ff..1306985f5f 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ItemsControl.xaml
@@ -9,9 +9,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
-                          ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"/>
+                          ItemsPanel="{TemplateBinding ItemsPanel}"/>
         </Border>
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml b/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
index c17dc65cca..ec0b876c71 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ListBox.xaml
@@ -34,11 +34,8 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Margin="{TemplateBinding Padding}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            Margin="{TemplateBinding Padding}"/>
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
index d1707d0af2..cdfca65ff6 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
@@ -273,11 +273,8 @@
           <Border Name="border" BoxShadow="inset -6 0 3 -3 #20000000" Background="{TemplateBinding Background}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}">
             <ScrollViewer Name="PART_ScrollViewer" HorizontalScrollBarVisibility="{TemplateBinding (ScrollViewer.HorizontalScrollBarVisibility)}" VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
               <ItemsPresenter Name="PART_ItemsPresenter"
-                              Items="{TemplateBinding Items}"
                               ItemsPanel="{TemplateBinding ItemsPanel}"
-                              ItemTemplate="{TemplateBinding ItemTemplate}"
-                              Margin="{TemplateBinding Padding}"
-                              VirtualizationMode="{TemplateBinding VirtualizationMode}"/>
+                              Margin="{TemplateBinding Padding}"/>
             </ScrollViewer>
           </Border>
         </ControlTemplate>
diff --git a/src/Avalonia.Themes.Fluent/Controls/Menu.xaml b/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
index f5fd69a67f..692bac958a 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Menu.xaml
@@ -48,9 +48,7 @@
                       CornerRadius="{DynamicResource OverlayCornerRadius}">
                 <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
                                   Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                                   Grid.IsSharedSizeScope="True" />
                 </ScrollViewer>
@@ -101,9 +99,7 @@
                 HorizontalAlignment="Stretch"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
                           VerticalAlignment="Stretch"
                           KeyboardNavigation.TabNavigation="Continue" />
         </Border>
diff --git a/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
index 6bca00b219..b1f44cc70d 100644
--- a/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/MenuFlyoutPresenter.xaml
@@ -22,9 +22,7 @@
                         Theme="{StaticResource FluentMenuScrollViewer}"
                         VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                             KeyboardNavigation.TabNavigation="Continue"
                             Grid.IsSharedSizeScope="True" />
diff --git a/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml b/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
index 4060d7efbe..e87f4b7d93 100644
--- a/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/MenuItem.xaml
@@ -131,9 +131,7 @@
                     CornerRadius="{DynamicResource OverlayCornerRadius}">
               <ScrollViewer Theme="{StaticResource FluentMenuScrollViewer}">
                 <ItemsPresenter Name="PART_ItemsPresenter"
-                                Items="{TemplateBinding Items}"
                                 ItemsPanel="{TemplateBinding ItemsPanel}"
-                                ItemTemplate="{TemplateBinding ItemTemplate}"
                                 Margin="{DynamicResource MenuFlyoutScrollerMargin}"
                                 Grid.IsSharedSizeScope="True" />
               </ScrollViewer>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml b/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
index 17d179e0cd..cd89443e1f 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TabControl.xaml
@@ -32,9 +32,7 @@
                 VerticalAlignment="{TemplateBinding VerticalAlignment}">
           <DockPanel>
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
                             DockPanel.Dock="{TemplateBinding TabStripPlacement}" />
             <ContentPresenter Name="PART_SelectedContentHost"
                               Margin="{TemplateBinding Padding}"
diff --git a/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml b/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
index 59cb7f6752..ead6fc41ab 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TabStrip.xaml
@@ -19,9 +19,7 @@
                 CornerRadius="{TemplateBinding CornerRadius}"
                 Padding="{TemplateBinding Padding}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          Items="{TemplateBinding Items}"
-                          ItemsPanel="{TemplateBinding ItemsPanel}"
-                          ItemTemplate="{TemplateBinding ItemTemplate}" />
+                          ItemsPanel="{TemplateBinding ItemsPanel}" />
         </Border>
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
index c340599000..c43e416191 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeView.xaml
@@ -32,7 +32,6 @@
                         IsScrollChainingEnabled="{TemplateBinding (ScrollViewer.IsScrollChainingEnabled)}"
                         AllowAutoHide="{TemplateBinding (ScrollViewer.AllowAutoHide)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             Margin="{TemplateBinding Padding}" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
index 9171791a0f..834c2245a8 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
@@ -95,7 +95,6 @@
           </Border>
           <ItemsPresenter Name="PART_ItemsPresenter"
                           IsVisible="{TemplateBinding IsExpanded}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </StackPanel>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
index e79e3942c9..66a4a1866a 100644
--- a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
@@ -10,7 +10,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <CarouselPresenter Margin="{TemplateBinding Padding}"
                              IsVirtualized="{TemplateBinding IsVirtualized}"
-                             Items="{TemplateBinding Items}"
                              ItemsPanel="{TemplateBinding ItemsPanel}"
                              PageTransition="{TemplateBinding PageTransition}"
                              SelectedIndex="{TemplateBinding SelectedIndex}" />
diff --git a/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml b/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
index d7dabae516..1f4e48e4a8 100644
--- a/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ComboBox.xaml
@@ -62,10 +62,7 @@
                 <ScrollViewer HorizontalScrollBarVisibility="{TemplateBinding ScrollViewer.HorizontalScrollBarVisibility}"
                               VerticalScrollBarVisibility="{TemplateBinding ScrollViewer.VerticalScrollBarVisibility}">
                   <ItemsPresenter Name="PART_ItemsPresenter"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
-                                  ItemsPanel="{TemplateBinding ItemsPanel}"
-                                  VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                                  ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
             </Popup>
diff --git a/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml b/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
index e99f1c5ac0..3317178979 100644
--- a/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ContextMenu.xaml
@@ -17,8 +17,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ScrollViewer Theme="{StaticResource SimpleMenuScrollViewer}">
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             KeyboardNavigation.TabNavigation="Continue" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml b/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
index d8cdf96abd..d85cf193fa 100644
--- a/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ItemsControl.xaml
@@ -10,8 +10,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/ListBox.xaml b/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
index 7308738681..e1257ef10f 100644
--- a/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ListBox.xaml
@@ -23,10 +23,7 @@
                         VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
-                            ItemsPanel="{TemplateBinding ItemsPanel}"
-                            VirtualizationMode="{TemplateBinding VirtualizationMode}" />
+                            ItemsPanel="{TemplateBinding ItemsPanel}" />
           </ScrollViewer>
         </Border>
       </ControlTemplate>
diff --git a/src/Avalonia.Themes.Simple/Controls/Menu.xaml b/src/Avalonia.Themes.Simple/Controls/Menu.xaml
index 95b259bfa6..797aeedd23 100644
--- a/src/Avalonia.Themes.Simple/Controls/Menu.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Menu.xaml
@@ -36,8 +36,6 @@
                   <ItemsPresenter Name="PART_ItemsPresenter"
                                   Margin="2"
                                   Grid.IsSharedSizeScope="True"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
@@ -72,8 +70,6 @@
                 BorderThickness="{TemplateBinding BorderThickness}"
                 CornerRadius="{TemplateBinding CornerRadius}">
           <ItemsPresenter Name="PART_ItemsPresenter"
-                          ItemTemplate="{TemplateBinding ItemTemplate}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}"
                           KeyboardNavigation.TabNavigation="Continue" />
         </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml b/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
index d974c36d31..05337d774f 100644
--- a/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/MenuFlyoutPresenter.xaml
@@ -20,8 +20,6 @@
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
                             Grid.IsSharedSizeScope="True"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}"
                             KeyboardNavigation.TabNavigation="Continue" />
           </ScrollViewer>
diff --git a/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml b/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
index ec22ee413d..de31f90d64 100644
--- a/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/MenuItem.xaml
@@ -72,8 +72,6 @@
                   <ItemsPresenter Name="PART_ItemsPresenter"
                                   Margin="2"
                                   Grid.IsSharedSizeScope="True"
-                                  ItemTemplate="{TemplateBinding ItemTemplate}"
-                                  Items="{TemplateBinding Items}"
                                   ItemsPanel="{TemplateBinding ItemsPanel}" />
                 </ScrollViewer>
               </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/TabControl.xaml b/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
index 4d1fcc0336..c3cecb4fb8 100644
--- a/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TabControl.xaml
@@ -14,8 +14,6 @@
                 CornerRadius="{TemplateBinding CornerRadius}">
           <DockPanel>
             <ItemsPresenter Name="PART_ItemsPresenter"
-                            ItemTemplate="{TemplateBinding ItemTemplate}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}" />
             <ContentPresenter Name="PART_SelectedContentHost"
                               Margin="{TemplateBinding Padding}"
diff --git a/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml b/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
index 3960c1d275..fd12eaa258 100644
--- a/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TabStrip.xaml
@@ -5,8 +5,6 @@
     <Setter Property="Template">
       <ControlTemplate>
         <ItemsPresenter Name="PART_ItemsPresenter"
-                        ItemTemplate="{TemplateBinding ItemTemplate}"
-                        Items="{TemplateBinding Items}"
                         ItemsPanel="{TemplateBinding ItemsPanel}" />
       </ControlTemplate>
     </Setter>
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeView.xaml b/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
index 2bc38a0673..8630c14aa2 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeView.xaml
@@ -21,7 +21,6 @@
                         VerticalScrollBarVisibility="{TemplateBinding (ScrollViewer.VerticalScrollBarVisibility)}">
             <ItemsPresenter Name="PART_ItemsPresenter"
                             Margin="{TemplateBinding Padding}"
-                            Items="{TemplateBinding Items}"
                             ItemsPanel="{TemplateBinding ItemsPanel}" />
           </ScrollViewer>
         </Border>
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
index 6ca3262419..c36bf4c673 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
@@ -63,7 +63,6 @@
           </Border>
           <ItemsPresenter Name="PART_ItemsPresenter"
                           IsVisible="{TemplateBinding IsExpanded}"
-                          Items="{TemplateBinding Items}"
                           ItemsPanel="{TemplateBinding ItemsPanel}" />
         </StackPanel>
       </ControlTemplate>
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index 76527b67e4..1d9e5df74a 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -300,7 +300,6 @@ namespace Avalonia.Controls.UnitTests
             {
                 Name = "PART_ItemsPresenter",
                 [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-                [~CarouselPresenter.ItemsProperty] = control[~Carousel.ItemsProperty],
                 [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
                 [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
                 [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
diff --git a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
index 1a8061bfd9..6eaef4c849 100644
--- a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
@@ -204,7 +204,6 @@ namespace Avalonia.Controls.UnitTests
                             Child = new ItemsPresenter
                             {
                                 Name = "PART_ItemsPresenter",
-                                [!ItemsPresenter.ItemsProperty] = parent[!ComboBox.ItemsProperty],
                             }.RegisterInNameScope(scope)
                         }.RegisterInNameScope(scope)
                     }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index f803ea2d53..ada5e10a7f 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -544,7 +544,6 @@ namespace Avalonia.Controls.UnitTests
             var presenter = new ItemsPresenter
             {
                 [StyledElement.TemplatedParentProperty] = target,
-                [~ItemsPresenter.ItemsProperty] = target[~ItemsControl.ItemsProperty],
             };
 
             presenter.ApplyTemplate();
@@ -777,7 +776,6 @@ namespace Avalonia.Controls.UnitTests
                     Child = new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                     }.RegisterInNameScope(scope)
                 };
             });
@@ -785,7 +783,7 @@ namespace Avalonia.Controls.UnitTests
 
         private class TestItemsControl : ItemsControl
         {
-            public new IItemsPresenter Presenter
+            public new ItemsPresenter Presenter
             {
                 get { return base.Presenter; }
                 set { base.Presenter = value; }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index 2804078861..b6375278b1 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.ObjectModel;
 using System.Linq;
 using System.Reactive.Subjects;
@@ -330,38 +331,39 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void ListBox_After_Scroll_IndexOutOfRangeException_Shouldnt_Be_Thrown()
         {
-            using (UnitTestApplication.Start(TestServices.StyledWindow))
-            {
-                var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
+            throw new NotImplementedException();
+            ////using (UnitTestApplication.Start(TestServices.StyledWindow))
+            ////{
+            ////    var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
 
-                var target = new ListBox
-                {
-                    Template = ListBoxTemplate(),
-                    Items = items,
-                    ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
-                };
+            ////    var target = new ListBox
+            ////    {
+            ////        Template = ListBoxTemplate(),
+            ////        Items = items,
+            ////        ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
+            ////    };
 
-                Prepare(target);
+            ////    Prepare(target);
 
-                var panel = target.Presenter.Panel as IVirtualizingPanel;
+            ////    var panel = target.Presenter.Panel as IVirtualizingPanel;
 
-                var listBoxItems = panel.Children.OfType<ListBoxItem>();
+            ////    var listBoxItems = panel.Children.OfType<ListBoxItem>();
 
-                //virtualization should have created exactly 10 items
-                Assert.Equal(10, listBoxItems.Count());
-                Assert.Equal("0", listBoxItems.First().DataContext);
-                Assert.Equal("9", listBoxItems.Last().DataContext);
+            ////    //virtualization should have created exactly 10 items
+            ////    Assert.Equal(10, listBoxItems.Count());
+            ////    Assert.Equal("0", listBoxItems.First().DataContext);
+            ////    Assert.Equal("9", listBoxItems.Last().DataContext);
 
-                //instead pixeloffset > 0 there could be pretty complex sequence for repro
-                //it involves add/remove/scroll to end multiple actions
-                //which i can't find so far :(, but this is the simplest way to add it to unit test
-                panel.PixelOffset = 1;
+            ////    //instead pixeloffset > 0 there could be pretty complex sequence for repro
+            ////    //it involves add/remove/scroll to end multiple actions
+            ////    //which i can't find so far :(, but this is the simplest way to add it to unit test
+            ////    panel.PixelOffset = 1;
 
-                //here scroll to end -> IndexOutOfRangeException is thrown
-                target.Scroll.Offset = new Vector(0, 2);
+            ////    //here scroll to end -> IndexOutOfRangeException is thrown
+            ////    target.Scroll.Offset = new Vector(0, 2);
 
-                Assert.True(true);
-            }
+            ////    Assert.True(true);
+            ////}
         }
 
         [Fact]
@@ -600,9 +602,7 @@ namespace Avalonia.Controls.UnitTests
                     Content = new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                         [~ItemsPresenter.ItemsPanelProperty] = parent.GetObservable(ItemsControl.ItemsPanelProperty).ToBinding(),
-                        [~ItemsPresenter.VirtualizationModeProperty] = parent.GetObservable(ListBox.VirtualizationModeProperty).ToBinding(),
                     }.RegisterInNameScope(scope)
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
index 87d45fa106..b358c98a62 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Multiple.cs
@@ -93,7 +93,6 @@ namespace Avalonia.Controls.UnitTests
                 Content = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = ((Control)parent).GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                 }.RegisterInNameScope(scope)
             };
         }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
index 03aac5e2f4..cb4e81001f 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests_Single.cs
@@ -324,7 +324,6 @@ namespace Avalonia.Controls.UnitTests
                 Content = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = parent.GetObservable(ItemsControl.ItemsProperty).ToBinding(),
                 }.RegisterInNameScope(scope)
             };
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
index 1408b8760b..f5094accb5 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
@@ -1,732 +1,732 @@
-using System.Linq;
-using Moq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Xunit;
-using System.Collections.ObjectModel;
-using System.Collections;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class CarouselPresenterTests
-    {
-        [Fact]
-        public void Should_Register_With_Host_When_TemplatedParent_Set()
-        {
-            var host = new Carousel();
-            var target = new CarouselPresenter();
-
-            Assert.Null(host.Presenter);
-
-            target.SetValue(Control.TemplatedParentProperty, host);
-
-            Assert.Same(target, host.Presenter);
-        }
-
-        [Fact]
-        public void ApplyTemplate_Should_Create_Panel()
-        {
-            var target = new CarouselPresenter
-            {
-                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
-            };
-
-            target.ApplyTemplate();
-
-            Assert.IsType<Panel>(target.Panel);
-        }
-
-        [Fact]
-        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-        {
-            var parent = new TestItemsControl();
-            var target = new CarouselPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-
-            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-        }
-
-        public class Virtualized
-        {
-            [Fact]
-            public void Should_Initially_Materialize_Selected_Container()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Switching_To_Virtualized_Should_Reset_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                target.IsVirtualized = true;
-
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Changing_SelectedIndex_Should_Show_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                AssertSingle(target);
-
-                target.SelectedIndex = 1;
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Remove_NonCurrent_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = true,
-                    SelectedIndex = 0,
-                };
-
-                target.ApplyTemplate();
-                AssertSingle(target);
-
-                target.SelectedIndex = 1;
-                AssertSingle(target);
-
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items.Insert(2, "after");
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(1);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items.RemoveAt(2);
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(2);
-                Assert.Equal(1, target.SelectedIndex);
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Last_Item()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Should_Handle_Replacing_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items[1] = "replaced";
-                AssertSingle(target);
-            }
-
-            [Fact]
-            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                var child = AssertSingle(target);
-                items[0] = "replaced";
-                Assert.Same(child, AssertSingle(target));
-            }
-
-            [Fact]
-            public void Should_Handle_Moving_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-
-                items.Move(1, 0);
-                AssertSingle(target);
-            }
-
-            private static Control AssertSingle(CarouselPresenter target)
-            {
-                var items = (IList)target.Items;
-                var index = target.SelectedIndex;
-                var content = items[index];
-                var child = Assert.Single(target.Panel.Children);
-                var presenter = Assert.IsType<ContentPresenter>(child);
-                var container = Assert.Single(target.ItemContainerGenerator.Containers);
-                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
-
-                Assert.Same(child, container.ContainerControl);
-                Assert.Same(child, visible);
-                Assert.Equal(content, presenter.Content);
-                Assert.Equal(content, container.Item);
-                Assert.Equal(index, container.Index);
-
-                return child;
-            }
-        }
-
-        public class NonVirtualized
-        {
-            [Fact]
-            public void Should_Initially_Materialize_All_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Initially_Show_Selected_Item()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = true,
-                };
-
-                target.ApplyTemplate();
-                target.IsVirtualized = false;
-
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Changing_SelectedIndex_Should_Show_Page()
-            {
-                var target = new CarouselPresenter
-                {
-                    Items = new[] { "foo", "bar" },
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                AssertAll(target);
-
-                target.SelectedIndex = 1;
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Insert(1, "item1a");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                items.Insert(2, "after");
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_At_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(1);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_Before_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Item_After_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-                items.RemoveAt(2);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 2,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(2);
-                Assert.Equal(1, target.SelectedIndex);
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Removing_Last_Item()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 0,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.RemoveAt(0);
-                Assert.Empty(target.Panel.Children);
-                Assert.Empty(target.ItemContainerGenerator.Containers);
-            }
-
-            [Fact]
-            public void Should_Handle_Replacing_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items[1] = "replaced";
-                AssertAll(target);
-            }
-
-            [Fact]
-            public void Should_Handle_Moving_SelectedItem()
-            {
-                var items = new ObservableCollection<string>
-                {
-                    "item0",
-                    "item1",
-                    "item2",
-                };
-
-                var target = new CarouselPresenter
-                {
-                    Items = items,
-                    SelectedIndex = 1,
-                    IsVirtualized = false,
-                };
-
-                target.ApplyTemplate();
-
-                items.Move(1, 0);
-                AssertAll(target);
-            }
-
-            private static void AssertAll(CarouselPresenter target)
-            {
-                var items = (IList)target.Items;
-
-                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
-                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
-
-                for (var i = 0; i < items?.Count; ++i)
-                {
-                    var content = items[i];
-                    var child = target.Panel.Children[i];
-                    var presenter = Assert.IsType<ContentPresenter>(child);
-                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
-
-                    Assert.Same(child, container);
-                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
-                    Assert.Equal(content, presenter.Content);
-                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
-                }
-            }
-        }
-
-        private class TestItem : ContentControl
-        {
-        }
-
-        private class TestItemsControl : ItemsControl
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-            }
-        }
-    }
-}
+////using System.Linq;
+////using Moq;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Xunit;
+////using System.Collections.ObjectModel;
+////using System.Collections;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class CarouselPresenterTests
+////    {
+////        [Fact]
+////        public void Should_Register_With_Host_When_TemplatedParent_Set()
+////        {
+////            var host = new Carousel();
+////            var target = new CarouselPresenter();
+
+////            Assert.Null(host.Presenter);
+
+////            target.SetValue(Control.TemplatedParentProperty, host);
+
+////            Assert.Same(target, host.Presenter);
+////        }
+
+////        [Fact]
+////        public void ApplyTemplate_Should_Create_Panel()
+////        {
+////            var target = new CarouselPresenter
+////            {
+////                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.IsType<Panel>(target.Panel);
+////        }
+
+////        [Fact]
+////        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
+////        {
+////            var parent = new TestItemsControl();
+////            var target = new CarouselPresenter
+////            {
+////                [StyledElement.TemplatedParentProperty] = parent,
+////            };
+
+////            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
+////        }
+
+////        public class Virtualized
+////        {
+////            [Fact]
+////            public void Should_Initially_Materialize_Selected_Container()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Switching_To_Virtualized_Should_Reset_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                target.IsVirtualized = true;
+
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Changing_SelectedIndex_Should_Show_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertSingle(target);
+
+////                target.SelectedIndex = 1;
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Remove_NonCurrent_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = true,
+////                    SelectedIndex = 0,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertSingle(target);
+
+////                target.SelectedIndex = 1;
+////                AssertSingle(target);
+
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items.Insert(2, "after");
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(1);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items.RemoveAt(2);
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(2);
+////                Assert.Equal(1, target.SelectedIndex);
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Last_Item()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Replacing_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items[1] = "replaced";
+////                AssertSingle(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                var child = AssertSingle(target);
+////                items[0] = "replaced";
+////                Assert.Same(child, AssertSingle(target));
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Moving_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Move(1, 0);
+////                AssertSingle(target);
+////            }
+
+////            private static Control AssertSingle(CarouselPresenter target)
+////            {
+////                var items = (IList)target.Items;
+////                var index = target.SelectedIndex;
+////                var content = items[index];
+////                var child = Assert.Single(target.Panel.Children);
+////                var presenter = Assert.IsType<ContentPresenter>(child);
+////                var container = Assert.Single(target.ItemContainerGenerator.Containers);
+////                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
+
+////                Assert.Same(child, container.ContainerControl);
+////                Assert.Same(child, visible);
+////                Assert.Equal(content, presenter.Content);
+////                Assert.Equal(content, container.Item);
+////                Assert.Equal(index, container.Index);
+
+////                return child;
+////            }
+////        }
+
+////        public class NonVirtualized
+////        {
+////            [Fact]
+////            public void Should_Initially_Materialize_All_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Initially_Show_Selected_Item()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = true,
+////                };
+
+////                target.ApplyTemplate();
+////                target.IsVirtualized = false;
+
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Changing_SelectedIndex_Should_Show_Page()
+////            {
+////                var target = new CarouselPresenter
+////                {
+////                    Items = new[] { "foo", "bar" },
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                AssertAll(target);
+
+////                target.SelectedIndex = 1;
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Insert(1, "item1a");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                items.Insert(2, "after");
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_At_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(1);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_Before_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Item_After_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+////                items.RemoveAt(2);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 2,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(2);
+////                Assert.Equal(1, target.SelectedIndex);
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Removing_Last_Item()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 0,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.RemoveAt(0);
+////                Assert.Empty(target.Panel.Children);
+////                Assert.Empty(target.ItemContainerGenerator.Containers);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Replacing_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items[1] = "replaced";
+////                AssertAll(target);
+////            }
+
+////            [Fact]
+////            public void Should_Handle_Moving_SelectedItem()
+////            {
+////                var items = new ObservableCollection<string>
+////                {
+////                    "item0",
+////                    "item1",
+////                    "item2",
+////                };
+
+////                var target = new CarouselPresenter
+////                {
+////                    Items = items,
+////                    SelectedIndex = 1,
+////                    IsVirtualized = false,
+////                };
+
+////                target.ApplyTemplate();
+
+////                items.Move(1, 0);
+////                AssertAll(target);
+////            }
+
+////            private static void AssertAll(CarouselPresenter target)
+////            {
+////                var items = (IList)target.Items;
+
+////                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
+////                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
+
+////                for (var i = 0; i < items?.Count; ++i)
+////                {
+////                    var content = items[i];
+////                    var child = target.Panel.Children[i];
+////                    var presenter = Assert.IsType<ContentPresenter>(child);
+////                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
+
+////                    Assert.Same(child, container);
+////                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
+////                    Assert.Equal(content, presenter.Content);
+////                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
+////                }
+////            }
+////        }
+
+////        private class TestItem : ContentControl
+////        {
+////        }
+
+////        private class TestItemsControl : ItemsControl
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
index 7024b1dde8..71f803fab7 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests.cs
@@ -1,14 +1,15 @@
+using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using System.Linq;
-using Moq;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
-using Avalonia.Input;
+using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using Xunit;
 
+#nullable enable
+
 namespace Avalonia.Controls.UnitTests.Presenters
 {
     public class ItemsPresenterTests
@@ -27,327 +28,126 @@ namespace Avalonia.Controls.UnitTests.Presenters
         }
 
         [Fact]
-        public void Should_Add_Containers()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.IsType<ContentPresenter>(target.Panel.Children[0]);
-            Assert.IsType<ContentPresenter>(target.Panel.Children[1]);
-            Assert.Equal("foo", ((ContentPresenter)target.Panel.Children[0]).Content);
-            Assert.Equal("bar", ((ContentPresenter)target.Panel.Children[1]).Content);
-        }
-
-        [Fact]
-        public void Should_Add_Containers_Of_Correct_Type()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
-
-            target.ItemContainerGenerator = new ItemContainerGenerator<ListBoxItem>(
-                target, 
-                ListBoxItem.ContentProperty,
-                null);
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.IsType<ListBoxItem>(target.Panel.Children[0]);
-            Assert.IsType<ListBoxItem>(target.Panel.Children[1]);
-        }
-
-        [Fact]
-        public void Should_Create_Containers_Only_Once()
-        {
-            var parent = new TestItemsControl();
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-            var raised = 0;
-
-            parent.ItemContainerGenerator.Materialized += (s, e) => ++raised;
-
-            target.ApplyTemplate();
-
-            Assert.Equal(2, target.Panel.Children.Count);
-            Assert.Equal(2, raised);
-        }
-
-        [Fact]
-        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-        {
-            var parent = new TestItemsControl();
-            var target = new ItemsPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = parent,
-            };
-
-            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-        }
-
-        [Fact]
-        public void Should_Remove_Containers()
+        public void Panel_Should_Be_Visual_Child()
         {
-            var items = new AvaloniaList<string>(new[] { "foo", "bar" });
-            var target = new ItemsPresenter
-            {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            items.RemoveAt(0);
+            var (target, _, _) = CreateTarget();
+            var child = target.GetVisualChildren().Single();
 
-            Assert.Single(target.Panel.Children);
-            Assert.Equal("bar", ((ContentPresenter)target.Panel.Children[0]).Content);
-            Assert.Equal("bar", ((ContentPresenter)target.ItemContainerGenerator.ContainerFromIndex(0)).Content);
+            Assert.Equal(target.Panel, child);
         }
 
-        [Fact]
-        public void Clearing_Items_Should_Remove_Containers()
+        public class NonVirtualizingPanel
         {
-            var items = new ObservableCollection<string> { "foo", "bar" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Creates_Containers_For_Initial_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new[] { "foo", "bar", "baz" };
+                var (target, _, _) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items.Clear();
-
-            Assert.Empty(target.Panel.Children);
-            Assert.Empty(target.ItemContainerGenerator.Containers);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Replacing_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Creates_Containers_For_Inserted_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items[1] = "baz";
+                items.Insert(1, "foo2");
+                root.LayoutManager.ExecuteLayoutPass();
 
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "baz", "baz" }, text);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Moving_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Removes_Containers_For_Removed_Items()
             {
-                Items = items,
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
-            items.Move(2, 1);
+                items.RemoveAt(1);
+                root.LayoutManager.ExecuteLayoutPass();
 
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "baz", "bar" }, text);
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Inserting_Items_Should_Update_Containers()
-        {
-            var items = new ObservableCollection<string> { "foo", "bar", "baz" };
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_For_Moved_Items()
             {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            items.Insert(2, "insert");
-
-            var text = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(new[] { "foo", "bar", "insert", "baz" }, text);
-        }
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-        [Fact]
-        public void Setting_Items_To_Null_Should_Remove_Containers()
-        {
-            var target = new ItemsPresenter
-            {
-                Items = new[] { "foo", "bar" },
-            };
+                items.Move(0, 2);
+                root.LayoutManager.ExecuteLayoutPass();
 
-            target.ApplyTemplate();
-            target.Items = null;
-
-            Assert.Empty(target.Panel.Children);
-            Assert.Empty(target.ItemContainerGenerator.Containers);
-        }
-
-        [Fact]
-        public void Should_Handle_Null_Items()
-        {
-            var items = new AvaloniaList<string>(new[] { "foo", null, "bar" });
+                AssertContainers(panel, items);
+            }
 
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_For_Replaced_Items()
             {
-                Items = items,
-            };
-
-            target.ApplyTemplate();
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, _, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            var text = target.Panel.Children.Cast<ContentPresenter>().Select(x => x.Content).ToList();
+                items[1] = "bar2";
+                root.LayoutManager.ExecuteLayoutPass();
 
-            Assert.Equal(new[] { "foo", null, "bar" }, text);
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(0));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(1));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(2));
-
-            items.RemoveAt(1);
-
-            text = target.Panel.Children.Cast<ContentPresenter>().Select(x => x.Content).ToList();
-
-            Assert.Equal(new[] { "foo", "bar" }, text);
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(0));
-            Assert.NotNull(target.ItemContainerGenerator.ContainerFromIndex(1));
-        }
+                AssertContainers(panel, items);
+            }
 
-        [Fact]
-        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-        {
-            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-            var target = new ItemsPresenter
+            [Fact]
+            public void Updates_Containers_On_Items_Changed()
             {
-                VirtualizationMode = ItemVirtualizationMode.None,
-                Items = items,
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-            };
+                using var app = Start();
+                var items = new ObservableCollection<string>(new[] { "foo", "bar", "baz" });
+                var (target, itemsControl, root) = CreateTarget(items);
+                var panel = Assert.IsType<StackPanel>(target.Panel);
 
-            target.ApplyTemplate();
+                var newItems = new[] { "qux", "quux", "corge" };
+                itemsControl.Items = newItems;
+                root.LayoutManager.ExecuteLayoutPass();
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-            foreach (var item in toAdd)
-            {
-                items.Insert(1, item);
+                AssertContainers(panel, newItems);
             }
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-            foreach (var item in toAdd)
+            private static void AssertContainers(StackPanel panel, IReadOnlyList<string> items)
             {
-                items.Remove(item);
-            }
+                Assert.Equal(items.Count, panel.Children.Count);
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+                for (var i = 0; i < items.Count; i++)
+                {
+                    var container = Assert.IsType<ContentPresenter>(panel.Children[i]);
+                    Assert.Equal(items[i], container.DataContext);
+                    Assert.Equal(items[i], container.Content);
+                }
+            }
         }
 
-        [Fact]
-        public void Should_Handle_Duplicate_Items()
+        private static (ItemsPresenter, ItemsControl, TestRoot) CreateTarget(IReadOnlyList<string>? items = null)
         {
-            var items = new AvaloniaList<int>(new[] { 1, 2, 1 });
+            var result = new ItemsPresenter();
 
-            var target = new ItemsPresenter
+            var itemsControl = new ItemsControl
             {
                 Items = items,
+                Template = new FuncControlTemplate<ItemsControl>((_, _) => result)
             };
 
-            target.ApplyTemplate();
-            items.RemoveAt(2);
-
-            var numbers = target.Panel.Children
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .Cast<int>();
-            Assert.Equal(new[] { 1, 2 }, numbers);
-        }
-
-        [Fact]
-        public void Panel_Should_Be_Created_From_ItemsPanel_Template()
-        {
-            var panel = new Panel();
-            var target = new ItemsPresenter
-            {
-                ItemsPanel = new FuncTemplate<Panel>(() => panel),
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Same(panel, target.Panel);
-            Assert.Same(target, target.Panel.Parent);
+            var root = new TestRoot(itemsControl);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+            return (result, itemsControl, root);
         }
 
-        [Fact]
-        public void Panel_TabNavigation_Should_Be_Set_To_Once()
-        {
-            var target = new ItemsPresenter();
-
-            target.ApplyTemplate();
-
-            Assert.Equal(KeyboardNavigationMode.Once, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
-        }
-
-        [Fact]
-        public void Panel_TabNavigation_Should_Be_Set_To_ItemsPresenter_Value()
-        {
-            var target = new ItemsPresenter();
-
-            KeyboardNavigation.SetTabNavigation(target, KeyboardNavigationMode.Cycle);
-            target.ApplyTemplate();
-
-            Assert.Equal(KeyboardNavigationMode.Cycle, KeyboardNavigation.GetTabNavigation((InputElement)target.Panel));
-        }
-
-        [Fact]
-        public void Panel_Should_Be_Visual_Child()
-        {
-            var target = new ItemsPresenter();
-
-            target.ApplyTemplate();
-
-            var child = target.GetVisualChildren().Single();
-
-            Assert.Equal(target.Panel, child);
-        }
-
-        private class Item
-        {
-            public Item(string value)
-            {
-                Value = value;
-            }
-
-            public string Value { get; }
-        }
-
-        private class TestItem : ContentControl
-        {
-        }
-
-        private class TestItemsControl : ItemsControl
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-            }
-        }
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
index bf3d838849..d0798d469f 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
@@ -1,374 +1,374 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Layout;
-using Avalonia.Platform;
-using Avalonia.Rendering;
-using Avalonia.UnitTests;
-using Avalonia.VisualTree;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class ItemsPresenterTests_Virtualization
-    {
-        [Fact]
-        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
-        {
-            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var target = new TestItemsPresenter(true)
-            {
-                Items = items,
-                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
-                ItemTemplate = ItemTemplate(),
-                VirtualizationMode = ItemVirtualizationMode.Simple,
-            };
-
-            var scroller = new ScrollContentPresenter
-            {
-                Content = target,
-            };
-
-            scroller.UpdateChild();
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Empty(target.Panel.Children);
-
-            var root = new TestRoot
-            {
-                Child = scroller,
-            };
-
-            target.InvalidateMeasure();
-            target.Panel.InvalidateMeasure();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
-        {
-            var target = CreateTarget();
-            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
-        {
-            var target = CreateTarget(ItemVirtualizationMode.None);
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
-        {
-            var target = new ItemsPresenter
-            {
-                ItemsPanel = VirtualizingPanelTemplate(),
-                ItemTemplate = ItemTemplate(),
-                VirtualizationMode = ItemVirtualizationMode.Simple,
-            };
-
-            target.ApplyTemplate();
-
-            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Should_Return_IsLogicalScrollEnabled_True()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-        }
-
-        [Fact]
-        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            var scroll = (ScrollContentPresenter)target.Parent;
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-        }
-
-        [Fact]
-        public void Should_Fill_Panel_With_Containers()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            target.Measure(new Size(100, 100));
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Arrange(new Rect(0, 0, 100, 100));
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
-        {
-            var target = CreateTarget(itemCount: 2);
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(2, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(Size.Infinity);
-            target.Arrange(new Rect(target.DesiredSize));
-
-            Assert.Equal(new Size(10, 200), target.DesiredSize);
-            Assert.Equal(new Size(10, 200), target.Bounds.Size);
-            Assert.Equal(20, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Initial_Item_DataContexts_Should_Be_Correct()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
-
-        [Fact]
-        public void Should_Add_New_Items_When_Control_Is_Enlarged()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Measure(new Size(120, 120));
-            target.Arrange(new Rect(0, 0, 100, 120));
-
-            Assert.Equal(12, target.Panel.Children.Count);
-
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
-
-        [Fact]
-        public void Should_Not_Create_Virtualizer_Before_Panel()
-        {
-            var target = CreateTarget();
-
-            Assert.Null(target.Panel);
-            Assert.Null(target.Virtualizer);
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
-        {
-            var target = CreateTarget(mode: ItemVirtualizationMode.None);
-            var scroll = (ScrollContentPresenter)target.Parent;
-
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(20, target.Panel.Children.Count);
-            Assert.Equal(new Size(100, 200), scroll.Extent);
-            Assert.Equal(new Size(100, 100), scroll.Viewport);
-
-            target.VirtualizationMode = ItemVirtualizationMode.Simple;
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
-        {
-            using (UnitTestApplication.Start(new TestServices()))
-            {
-                var target = CreateTarget(mode: ItemVirtualizationMode.None);
-                var scroll = (TestScroller)target.Parent;
-
-                scroll.Width = scroll.Height = 100;
-                scroll.LayoutManager.ExecuteInitialLayoutPass();
-
-                // Ensure than an intermediate measure pass doesn't add more controls than it
-                // should. This can happen if target gets measured with Size.Infinity which
-                // is what the available size should be when VirtualizationMode == None but not
-                // what it should after VirtualizationMode is changed to Simple.
-                target.Panel.Children.CollectionChanged += (s, e) =>
-                {
-                    Assert.InRange(target.Panel.Children.Count, 0, 10);
-                };
-
-                target.VirtualizationMode = ItemVirtualizationMode.Simple;
-                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
-
-                Assert.Equal(10, target.Panel.Children.Count);
-            }
-        }
-
-        [Fact]
-        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
-        {
-            var target = CreateTarget();
-            var scroll = (ScrollContentPresenter)target.Parent;
-
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-            Assert.Equal(new Size(10, 20), scroll.Extent);
-            Assert.Equal(new Size(100, 10), scroll.Viewport);
-
-            target.VirtualizationMode = ItemVirtualizationMode.None;
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            // Here - unlike changing the other way - we need to do a layout pass on the scroll
-            // content presenter as non-logical scroll values are only updated on arrange.
-            scroll.Measure(new Size(100, 100));
-            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(20, target.Panel.Children.Count);
-            Assert.Equal(new Size(100, 200), scroll.Extent);
-            Assert.Equal(new Size(100, 100), scroll.Viewport);
-        }
-
-        private static ItemsPresenter CreateTarget(
-            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
-            Orientation orientation = Orientation.Vertical,
-            bool useContainers = true,
-            int itemCount = 20)
-        {
-            ItemsPresenter result;
-            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
-
-            var scroller = new TestScroller
-            {
-                CanHorizontallyScroll = false,
-                CanVerticallyScroll = true,
-                Content = result = new TestItemsPresenter(useContainers)
-                {
-                    Items = items,
-                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-                    ItemTemplate = ItemTemplate(),
-                    VirtualizationMode = mode,
-                }
-            };
-
-            scroller.UpdateChild();
-
-            return result;
-        }
-
-        private static IDataTemplate ItemTemplate()
-        {
-            return new FuncDataTemplate<string>((x, _) => new Canvas
-            {
-                Width = 10,
-                Height = 10,
-            });
-        }
-
-        private static ITemplate<Panel> VirtualizingPanelTemplate(
-            Orientation orientation = Orientation.Vertical)
-        {
-            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-            {
-                Orientation = orientation,
-            });
-        }
-
-        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
-        {
-            public TestScroller()
-            {
-                LayoutManager = new LayoutManager(this);
-            }
-
-            public IRenderer Renderer { get; }
-            public Size ClientSize { get; }
-            public double RenderScaling => 1;
-
-            public Size MaxClientSize => Size.Infinity;
-
-            public double LayoutScaling => 1;
-
-            public ILayoutManager LayoutManager { get; }
-
-            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-            public void Invalidate(Rect rect) => throw new NotImplementedException();
-            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-        }
-
-        private class TestItemsPresenter : ItemsPresenter
-        {
-            private bool _useContainers;
-
-            public TestItemsPresenter(bool useContainers)
-            {
-                _useContainers = useContainers;
-            }
-
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return _useContainers ?
-                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
-                    new ItemContainerGenerator(this);
-            }
-        }
-
-        private class TestContainer : ContentControl
-        {
-            public TestContainer()
-            {
-                Width = 10;
-                Height = 10;
-            }
-        }
-    }
-}
+////using System;
+////using System.Collections.Generic;
+////using System.Linq;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Layout;
+////using Avalonia.Platform;
+////using Avalonia.Rendering;
+////using Avalonia.UnitTests;
+////using Avalonia.VisualTree;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class ItemsPresenterTests_Virtualization
+////    {
+////        [Fact]
+////        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
+////        {
+////            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var target = new TestItemsPresenter(true)
+////            {
+////                Items = items,
+////                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
+////                ItemTemplate = ItemTemplate(),
+////                VirtualizationMode = ItemVirtualizationMode.Simple,
+////            };
+
+////            var scroller = new ScrollContentPresenter
+////            {
+////                Content = target,
+////            };
+
+////            scroller.UpdateChild();
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Empty(target.Panel.Children);
+
+////            var root = new TestRoot
+////            {
+////                Child = scroller,
+////            };
+
+////            target.InvalidateMeasure();
+////            target.Panel.InvalidateMeasure();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
+////        {
+////            var target = CreateTarget();
+////            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
+////        {
+////            var target = CreateTarget(ItemVirtualizationMode.None);
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
+////        {
+////            var target = new ItemsPresenter
+////            {
+////                ItemsPanel = VirtualizingPanelTemplate(),
+////                ItemTemplate = ItemTemplate(),
+////                VirtualizationMode = ItemVirtualizationMode.Simple,
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Should_Return_IsLogicalScrollEnabled_True()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
+////        }
+
+////        [Fact]
+////        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            var scroll = (ScrollContentPresenter)target.Parent;
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Fill_Panel_With_Containers()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            target.Measure(new Size(100, 100));
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Arrange(new Rect(0, 0, 100, 100));
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
+////        {
+////            var target = CreateTarget(itemCount: 2);
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(2, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(Size.Infinity);
+////            target.Arrange(new Rect(target.DesiredSize));
+
+////            Assert.Equal(new Size(10, 200), target.DesiredSize);
+////            Assert.Equal(new Size(10, 200), target.Bounds.Size);
+////            Assert.Equal(20, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Initial_Item_DataContexts_Should_Be_Correct()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
+
+////        [Fact]
+////        public void Should_Add_New_Items_When_Control_Is_Enlarged()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Measure(new Size(120, 120));
+////            target.Arrange(new Rect(0, 0, 100, 120));
+
+////            Assert.Equal(12, target.Panel.Children.Count);
+
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
+
+////        [Fact]
+////        public void Should_Not_Create_Virtualizer_Before_Panel()
+////        {
+////            var target = CreateTarget();
+
+////            Assert.Null(target.Panel);
+////            Assert.Null(target.Virtualizer);
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
+////        {
+////            var target = CreateTarget(mode: ItemVirtualizationMode.None);
+////            var scroll = (ScrollContentPresenter)target.Parent;
+
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(20, target.Panel.Children.Count);
+////            Assert.Equal(new Size(100, 200), scroll.Extent);
+////            Assert.Equal(new Size(100, 100), scroll.Viewport);
+
+////            target.VirtualizationMode = ItemVirtualizationMode.Simple;
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
+////        {
+////            using (UnitTestApplication.Start(new TestServices()))
+////            {
+////                var target = CreateTarget(mode: ItemVirtualizationMode.None);
+////                var scroll = (TestScroller)target.Parent;
+
+////                scroll.Width = scroll.Height = 100;
+////                scroll.LayoutManager.ExecuteInitialLayoutPass();
+
+////                // Ensure than an intermediate measure pass doesn't add more controls than it
+////                // should. This can happen if target gets measured with Size.Infinity which
+////                // is what the available size should be when VirtualizationMode == None but not
+////                // what it should after VirtualizationMode is changed to Simple.
+////                target.Panel.Children.CollectionChanged += (s, e) =>
+////                {
+////                    Assert.InRange(target.Panel.Children.Count, 0, 10);
+////                };
+
+////                target.VirtualizationMode = ItemVirtualizationMode.Simple;
+////                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+
+////                Assert.Equal(10, target.Panel.Children.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
+////        {
+////            var target = CreateTarget();
+////            var scroll = (ScrollContentPresenter)target.Parent;
+
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(new Size(10, 20), scroll.Extent);
+////            Assert.Equal(new Size(100, 10), scroll.Viewport);
+
+////            target.VirtualizationMode = ItemVirtualizationMode.None;
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            // Here - unlike changing the other way - we need to do a layout pass on the scroll
+////            // content presenter as non-logical scroll values are only updated on arrange.
+////            scroll.Measure(new Size(100, 100));
+////            scroll.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(20, target.Panel.Children.Count);
+////            Assert.Equal(new Size(100, 200), scroll.Extent);
+////            Assert.Equal(new Size(100, 100), scroll.Viewport);
+////        }
+
+////        private static ItemsPresenter CreateTarget(
+////            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
+////            Orientation orientation = Orientation.Vertical,
+////            bool useContainers = true,
+////            int itemCount = 20)
+////        {
+////            ItemsPresenter result;
+////            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
+
+////            var scroller = new TestScroller
+////            {
+////                CanHorizontallyScroll = false,
+////                CanVerticallyScroll = true,
+////                Content = result = new TestItemsPresenter(useContainers)
+////                {
+////                    Items = items,
+////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
+////                    ItemTemplate = ItemTemplate(),
+////                    VirtualizationMode = mode,
+////                }
+////            };
+
+////            scroller.UpdateChild();
+
+////            return result;
+////        }
+
+////        private static IDataTemplate ItemTemplate()
+////        {
+////            return new FuncDataTemplate<string>((x, _) => new Canvas
+////            {
+////                Width = 10,
+////                Height = 10,
+////            });
+////        }
+
+////        private static ITemplate<Panel> VirtualizingPanelTemplate(
+////            Orientation orientation = Orientation.Vertical)
+////        {
+////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
+////            {
+////                Orientation = orientation,
+////            });
+////        }
+
+////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
+////        {
+////            public TestScroller()
+////            {
+////                LayoutManager = new LayoutManager(this);
+////            }
+
+////            public IRenderer Renderer { get; }
+////            public Size ClientSize { get; }
+////            public double RenderScaling => 1;
+
+////            public Size MaxClientSize => Size.Infinity;
+
+////            public double LayoutScaling => 1;
+
+////            public ILayoutManager LayoutManager { get; }
+
+////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
+////            public void Invalidate(Rect rect) => throw new NotImplementedException();
+////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
+////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
+////        }
+
+////        private class TestItemsPresenter : ItemsPresenter
+////        {
+////            private bool _useContainers;
+
+////            public TestItemsPresenter(bool useContainers)
+////            {
+////                _useContainers = useContainers;
+////            }
+
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return _useContainers ?
+////                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
+////                    new ItemContainerGenerator(this);
+////            }
+////        }
+
+////        private class TestContainer : ContentControl
+////        {
+////            public TestContainer()
+////            {
+////                Width = 10;
+////                Height = 10;
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
index 08fd777ac6..131b86e4b1 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
@@ -1,1110 +1,1110 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.Linq;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Input;
-using Avalonia.Layout;
-using Avalonia.LogicalTree;
-using Avalonia.Platform;
-using Avalonia.Rendering;
-using Avalonia.Styling;
-using Avalonia.UnitTests;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Presenters
-{
-    public class ItemsPresenterTests_Virtualization_Simple
-    {
-        [Fact]
-        public void Should_Return_Items_Count_For_Extent_Vertical()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-
-            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
-        }
-
-        [Fact]
-        public void Should_Return_Items_Count_For_Extent_Horizontal()
-        {
-            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-            target.ApplyTemplate();
-
-            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
-        }
-
-        [Fact]
-        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
-        {
-            var target = CreateTarget();
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
-        }
-
-        [Fact]
-        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
-        {
-            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
-        }
-
-        [Fact]
-        public void Should_Add_Containers_When_Panel_Is_Not_Full()
-        {
-            var target = CreateTarget(itemCount: 5);
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(5, target.Panel.Children.Count);
-
-            items.Add("New Item");
-
-            Assert.Equal(6, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Remove_Items_When_Control_Is_Shrank()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
-
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            Assert.Equal(10, target.Panel.Children.Count);
-
-            target.Measure(new Size(100, 80));
-            target.Arrange(new Rect(0, 0, 100, 80));
-
-            Assert.Equal(8, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
+////using System;
+////using System.Collections;
+////using System.Collections.Generic;
+////using System.Collections.ObjectModel;
+////using System.Linq;
+////using Avalonia.Collections;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Input;
+////using Avalonia.Layout;
+////using Avalonia.LogicalTree;
+////using Avalonia.Platform;
+////using Avalonia.Rendering;
+////using Avalonia.Styling;
+////using Avalonia.UnitTests;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests.Presenters
+////{
+////    public class ItemsPresenterTests_Virtualization_Simple
+////    {
+////        [Fact]
+////        public void Should_Return_Items_Count_For_Extent_Vertical()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
+////        }
+
+////        [Fact]
+////        public void Should_Return_Items_Count_For_Extent_Horizontal()
+////        {
+////            var target = CreateTarget(orientation: Orientation.Horizontal);
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
+////        }
+
+////        [Fact]
+////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
+////        {
+////            var target = CreateTarget();
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
+////        {
+////            var target = CreateTarget(orientation: Orientation.Horizontal);
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
+////        }
+
+////        [Fact]
+////        public void Should_Add_Containers_When_Panel_Is_Not_Full()
+////        {
+////            var target = CreateTarget(itemCount: 5);
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(5, target.Panel.Children.Count);
+
+////            items.Add("New Item");
+
+////            Assert.Equal(6, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Remove_Items_When_Control_Is_Shrank()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
+
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
+
+////            Assert.Equal(10, target.Panel.Children.Count);
+
+////            target.Measure(new Size(100, 80));
+////            target.Arrange(new Rect(0, 0, 100, 80));
+
+////            Assert.Equal(8, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(10, target.Panel.Children.Count);
 
-            ((IScrollable)target).Offset = new Vector(0, 10);
-            target.Measure(new Size(120, 120));
-            target.Arrange(new Rect(0, 0, 100, 120));
+////            ((IScrollable)target).Offset = new Vector(0, 10);
+////            target.Measure(new Size(120, 120));
+////            target.Arrange(new Rect(0, 0, 100, 120));
 
-            Assert.Equal(12, target.Panel.Children.Count);
+////            Assert.Equal(12, target.Panel.Children.Count);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        [Fact]
-        public void Should_Update_Containers_When_Items_Changes()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Should_Update_Containers_When_Items_Changes()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            target.Items = new[] { "foo", "bar", "baz" };
+////            target.Items = new[] { "foo", "bar", "baz" };
 
-            Assert.Equal(3, target.Panel.Children.Count);
-        }
+////            Assert.Equal(3, target.Panel.Children.Count);
+////        }
 
-        [Fact]
-        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
-        }
+////            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
+////        }
 
-        [Fact]
-        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
 
-            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
 
-            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(10, minIndex);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-        }
+////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
+////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(10, minIndex);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////        }
 
-        [Fact]
-        public void Inserting_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Inserting_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Insert(6, "Inserted");
-            expected.Insert(1, "Inserted");
-            expected.RemoveAt(expected.Count - 1);
+////            items.Insert(6, "Inserted");
+////            expected.Insert(1, "Inserted");
+////            expected.RemoveAt(expected.Count - 1);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Insert(0, "Inserted");
+////            items.Insert(0, "Inserted");
 
-            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_First_Materialized_Item_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_First_Materialized_Item_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveAt(0);
-            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
+////            items.RemoveAt(0);
+////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 200));
-            target.Arrange(new Rect(0, 0, 100, 200));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 200));
+////            target.Arrange(new Rect(0, 0, 100, 200));
 
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(items, actual);
+////            Assert.Equal(items, actual);
 
-            items.RemoveAt(2);
+////            items.RemoveAt(2);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(items, actual);
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(items, actual);
 
-            items.RemoveAt(items.Count - 2);
+////            items.RemoveAt(items.Count - 2);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(items, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(items, actual);
+////        }
 
-        [Fact]
-        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 200));
-            target.Arrange(new Rect(0, 0, 100, 200));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 200));
+////            target.Arrange(new Rect(0, 0, 100, 200));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
 
-            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Remove(items.Last());
-            expected.Remove(expected.Last());
+////            items.Remove(items.Last());
+////            expected.Remove(expected.Last());
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveRange(18, 2);
-            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
+////            items.RemoveRange(18, 2);
+////            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
 
-            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.RemoveRange(15, 3);
-            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
-                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
-                .ToList();
+////            items.RemoveRange(15, 3);
+////            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
+////                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
+////                .ToList();
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
 
-            // Check for issue #589: this should not throw.
-            target.Measure(Size.Infinity);
+////            // Check for issue #589: this should not throw.
+////            target.Measure(Size.Infinity);
 
-            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
-        }
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Replacing_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Replacing_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items[4] = expected[4] = "Replaced";
+////            items[4] = expected[4] = "Replaced";
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Moving_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Moving_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            items.Move(4, 8);
-            var i = expected[4];
-            expected.RemoveAt(4);
-            expected.Insert(8, i);
+////            items.Move(4, 8);
+////            var i = expected[4];
+////            expected.RemoveAt(4);
+////            expected.Insert(8, i);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Setting_Items_To_Null_Should_Remove_Containers()
-        {
-            var target = CreateTarget();
+////        [Fact]
+////        public void Setting_Items_To_Null_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget();
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            target.Items = null;
+////            target.Items = null;
 
-            Assert.Empty(target.Panel.Children);
-        }
+////            Assert.Empty(target.Panel.Children);
+////        }
 
-        [Fact]
-        public void Reassigning_Items_Should_Create_Containers()
-        {
-            var target = CreateTarget(itemCount: 5);
+////        [Fact]
+////        public void Reassigning_Items_Should_Create_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 5);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-        {
-            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-            var target = new ItemsPresenter
-            {
-                VirtualizationMode = ItemVirtualizationMode.None,
-                Items = items,
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-            };
+////        [Fact]
+////        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
+////        {
+////            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
+////            var target = new ItemsPresenter
+////            {
+////                VirtualizationMode = ItemVirtualizationMode.None,
+////                Items = items,
+////                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
+////            };
 
-            target.ApplyTemplate();
+////            target.ApplyTemplate();
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
 
-            int addIndex = 1;
-            foreach (var item in toAdd)
-            {
-                items.Insert(addIndex++, item);
-            }
+////            int addIndex = 1;
+////            foreach (var item in toAdd)
+////            {
+////                items.Insert(addIndex++, item);
+////            }
 
-            Assert.Equal(items.Count, target.Panel.Children.Count);
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
 
-            foreach (var item in toAdd)
-            {
-                items.Remove(item);
-            }
-
-            Assert.Equal(items.Count, target.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Reassigning_Items_Should_Remove_Containers()
-        {
-            var target = CreateTarget(itemCount: 6);
+////            foreach (var item in toAdd)
+////            {
+////                items.Remove(item);
+////            }
+
+////            Assert.Equal(items.Count, target.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Reassigning_Items_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 6);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
-        {
-            var target = CreateTarget(itemCount: 6);
+////        [Fact]
+////        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 6);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-            var items = (ObservableCollection<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
+////            var items = (ObservableCollection<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-            target.Items = null;
-            target.Items = expected;
+////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
+////            target.Items = null;
+////            target.Items = expected;
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
-        {
-            var target = CreateTarget(itemCount: 10);
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
+////        {
+////            var target = CreateTarget(itemCount: 10);
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 95));
-            target.Arrange(new Rect(0, 0, 100, 95));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 95));
+////            target.Arrange(new Rect(0, 0, 100, 95));
 
-            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
 
-            items.Add("Item 10");
+////            items.Add("Item 10");
 
-            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-        }
+////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
+////        }
 
-        [Fact]
-        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
-        {
-            using (UnitTestApplication.Start(new TestServices()))
-            {
-                var target = CreateTarget(itemCount: 10);
-                var items = (IList<string>)target.Items;
-                target.ApplyTemplate();
-                target.Measure(Size.Empty);
-                target.Arrange(Rect.Empty);
+////        [Fact]
+////        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
+////        {
+////            using (UnitTestApplication.Start(new TestServices()))
+////            {
+////                var target = CreateTarget(itemCount: 10);
+////                var items = (IList<string>)target.Items;
+////                target.ApplyTemplate();
+////                target.Measure(Size.Empty);
+////                target.Arrange(Rect.Empty);
 
-                // Check for issue #591: this should not throw.
-                target.ScrollIntoView(0);
-            }
-        }
+////                // Check for issue #591: this should not throw.
+////                target.ScrollIntoView(0);
+////            }
+////        }
 
-        [Fact]
-        public void InsertRange_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void InsertRange_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
 
-            int index = 1;
+////            int index = 1;
 
-            items.InsertRange(index, toAdd);
-            expected.InsertRange(index, toAdd);
-            expected.RemoveRange(10, toAdd.Count);
+////            items.InsertRange(index, toAdd);
+////            expected.InsertRange(index, toAdd);
+////            expected.RemoveRange(10, toAdd.Count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void InsertRange_Items_Before_Last_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void InsertRange_Items_Before_Last_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected, actual);
+////            Assert.Equal(expected, actual);
 
-            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
+////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
 
-            int index = 8;
+////            int index = 8;
 
-            items.InsertRange(index, toAdd);
-            expected.InsertRange(index, toAdd);
-            expected.RemoveRange(10, toAdd.Count);
+////            items.InsertRange(index, toAdd);
+////            expected.InsertRange(index, toAdd);
+////            expected.RemoveRange(10, toAdd.Count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void RemoveRange_Items_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void RemoveRange_Items_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected.Take(10), actual);
+////            Assert.Equal(expected.Take(10), actual);
 
-            int index = 5;
-            int count = 3;
+////            int index = 5;
+////            int count = 3;
 
-            items.RemoveRange(index, count);
-            expected.RemoveRange(index, count);
+////            items.RemoveRange(index, count);
+////            expected.RemoveRange(index, count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
-        {
-            var target = CreateTarget(useAvaloniaList: true);
+////        [Fact]
+////        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
+////        {
+////            var target = CreateTarget(useAvaloniaList: true);
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-            var items = (AvaloniaList<string>)target.Items;
-            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
+////            var items = (AvaloniaList<string>)target.Items;
+////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            Assert.Equal(expected.Take(10), actual);
+////            Assert.Equal(expected.Take(10), actual);
 
-            int index = 8;
-            int count = 3;
+////            int index = 8;
+////            int count = 3;
 
-            items.RemoveRange(index, count);
-            expected.RemoveRange(index, count);
+////            items.RemoveRange(index, count);
+////            expected.RemoveRange(index, count);
 
-            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-            Assert.Equal(expected, actual);
-        }
+////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            Assert.Equal(expected, actual);
+////        }
 
-        [Fact]
-        public void Should_Add_Containers_For_Items_After_Clear()
-        {
-            var target = CreateTarget(itemCount: 10);
-            var defaultItems = (IList<string>)target.Items;
-            var items = new AvaloniaList<string>(defaultItems);
-            target.Items = items;
+////        [Fact]
+////        public void Should_Add_Containers_For_Items_After_Clear()
+////        {
+////            var target = CreateTarget(itemCount: 10);
+////            var defaultItems = (IList<string>)target.Items;
+////            var items = new AvaloniaList<string>(defaultItems);
+////            target.Items = items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(10, target.Panel.Children.Count);
+////            Assert.Equal(10, target.Panel.Children.Count);
 
-            items.Clear();
+////            items.Clear();
 
-            target.Panel.Measure(new Size(100, 100));
-            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
+////            target.Panel.Measure(new Size(100, 100));
+////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Empty(target.Panel.Children);
+////            Assert.Empty(target.Panel.Children);
 
-            items.AddRange(defaultItems.Select(s => s + " new"));
+////            items.AddRange(defaultItems.Select(s => s + " new"));
 
-            target.Panel.Measure(new Size(100, 100));
-            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
+////            target.Panel.Measure(new Size(100, 100));
+////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(target.DesiredSize));
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(target.DesiredSize));
 
-            Assert.Equal(10, target.Panel.Children.Count);
-        }
+////            Assert.Equal(10, target.Panel.Children.Count);
+////        }
 
-        [Fact]
-        public void Scroll_To_Last_Should_Work()
-        {
-            var target = CreateTarget(itemCount: 11);
-            var scroller = (TestScroller)target.Parent;
+////        [Fact]
+////        public void Scroll_To_Last_Should_Work()
+////        {
+////            var target = CreateTarget(itemCount: 11);
+////            var scroller = (TestScroller)target.Parent;
 
-            scroller.Width = scroller.Height = 100;
-            scroller.LayoutManager.ExecuteInitialLayoutPass();
+////            scroller.Width = scroller.Height = 100;
+////            scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-            var last = (target.Items as IList)[10];
+////            var last = (target.Items as IList)[10];
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
-        }
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
+////        }
 
-        [Fact]
-        public void Second_Scroll_To_Last_Should_Work()
-        {
-            var target = CreateTarget(itemCount: 11);
-            var scroller = (TestScroller)target.Parent;
+////        [Fact]
+////        public void Second_Scroll_To_Last_Should_Work()
+////        {
+////            var target = CreateTarget(itemCount: 11);
+////            var scroller = (TestScroller)target.Parent;
 
-            scroller.Width = scroller.Height = 100;
-            scroller.LayoutManager.ExecuteInitialLayoutPass();
+////            scroller.Width = scroller.Height = 100;
+////            scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-            var last = (target.Items as IList)[10];
+////            var last = (target.Items as IList)[10];
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
 
-            target.ScrollIntoView(10);
+////            target.ScrollIntoView(10);
 
-            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-            Assert.Same(target.Panel.Children[9].DataContext, last);
-        }
+////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////            Assert.Same(target.Panel.Children[9].DataContext, last);
+////        }
 
-        [Fact]
-        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
-        {
-            var target = CreateTarget();
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
+////        {
+////            var target = CreateTarget();
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var containers = target.Panel.Children.ToList();
-            var scroller = (ScrollContentPresenter)target.Parent;
+////            var containers = target.Panel.Children.ToList();
+////            var scroller = (ScrollContentPresenter)target.Parent;
 
-            scroller.Offset = new Vector(0, 5);
+////            scroller.Offset = new Vector(0, 5);
 
-            var scrolledContainers = containers
-                .Skip(5)
-                .Take(5)
-                .Concat(containers.Take(5)).ToList();
+////            var scrolledContainers = containers
+////                .Skip(5)
+////                .Take(5)
+////                .Concat(containers.Take(5)).ToList();
 
-            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(scrolledContainers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(scrolledContainers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
-            }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
+////            }
 
-            scroller.Offset = new Vector(0, 0);
-            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            scroller.Offset = new Vector(0, 0);
+////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
+////            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        [Fact]
-        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
-        {
-            var target = CreateTarget(itemCount: 50);
-            var items = (IList<string>)target.Items;
+////        [Fact]
+////        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
+////        {
+////            var target = CreateTarget(itemCount: 50);
+////            var items = (IList<string>)target.Items;
 
-            target.ApplyTemplate();
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+////            target.ApplyTemplate();
+////            target.Measure(new Size(100, 100));
+////            target.Arrange(new Rect(0, 0, 100, 100));
 
-            var containers = target.Panel.Children.ToList();
-            var scroller = (ScrollContentPresenter)target.Parent;
+////            var containers = target.Panel.Children.ToList();
+////            var scroller = (ScrollContentPresenter)target.Parent;
 
-            scroller.Offset = new Vector(0, 20);
+////            scroller.Offset = new Vector(0, 20);
 
-            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
-            }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
+////            }
 
-            scroller.Offset = new Vector(0, 0);
+////            scroller.Offset = new Vector(0, 0);
 
-            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-            Assert.Equal(containers, target.Panel.Children);
+////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
+////            Assert.Equal(containers, target.Panel.Children);
 
-            for (var i = 0; i < target.Panel.Children.Count; ++i)
-            {
-                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-            }
-        }
+////            for (var i = 0; i < target.Panel.Children.Count; ++i)
+////            {
+////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
+////            }
+////        }
 
-        public class Vertical
-        {
-            [Fact]
-            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
+////        public class Vertical
+////        {
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
 
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
 
-                var from = target.Panel.Children[5];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Same(target.Panel.Children[6], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[9];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[9], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 100;
-                scroller.Height = 95;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[8];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Down,
-                    from);
-
-                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[8], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-            {
-                var target = CreateTarget();
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 100;
-                scroller.Height = 95;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-                var from = target.Panel.Children[1];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Up,
-                    from);
-
-                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[0], result);
-            }
-
-            [Fact]
-            public void Should_Return_Horizontal_Extent_And_Viewport()
-            {
-                var target = CreateTarget();
-
-                target.ApplyTemplate();
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
-                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
-            }
-
-            [Fact]
-            public void Horizontal_Scroll_Should_Update_Item_Position()
-            {
-                var target = CreateTarget();
-
-                target.ApplyTemplate();
-
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
-
-                target.Measure(new Size(5, 100));
-                target.Arrange(new Rect(0, 0, 5, 100));
-
-                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
-            }
-        }
-
-        public class Horizontal
-        {
-            [Fact]
-            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[5];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Same(target.Panel.Children[6], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[9];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[9], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 95;
-                scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-                var from = target.Panel.Children[8];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Right,
-                    from);
-
-                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[8], result);
-            }
-
-            [Fact]
-            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-            {
-                var target = CreateTarget(orientation: Orientation.Horizontal);
-                var scroller = (TestScroller)target.Parent;
-
-                scroller.Width = 95;
-                scroller.Height = 100;
-                scroller.LayoutManager.ExecuteInitialLayoutPass();
-                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
-
-                var from = target.Panel.Children[1];
-                var result = ((ILogicalScrollable)target).GetControlInDirection(
-                    NavigationDirection.Left,
-                    from);
-
-                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
-                Assert.Same(target.Panel.Children[0], result);
-            }
-        }
-
-        private static ItemsPresenter CreateTarget(
-            Orientation orientation = Orientation.Vertical,
-            int itemCount = 20,
-            bool useAvaloniaList = false)
-        {
-            ItemsPresenter result;
-            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
-            var items = useAvaloniaList ?
-                (IEnumerable)new AvaloniaList<string>(itemsSource) :
-                (IEnumerable)new ObservableCollection<string>(itemsSource);
-
-            var scroller = new TestScroller
-            {
-                CanHorizontallyScroll = true,
-                CanVerticallyScroll = true,
-                Content = result = new TestItemsPresenter
-                {
-                    Items = items,
-                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-                    DataTemplates = { StringDataTemplate() },
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
-                }
-            };
-
-            scroller.UpdateChild();
-            return result;
-        }
-
-        private static IDataTemplate StringDataTemplate()
-        {
-            return new FuncDataTemplate<string>((x, _) => new Canvas
-            {
-                Width = 10,
-                Height = 10,
-            });
-        }
-
-        private static ITemplate<Panel> VirtualizingPanelTemplate(
-            Orientation orientation = Orientation.Vertical)
-        {
-            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-            {
-                Orientation = orientation,
-            });
-        }
-
-        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
-        {
-            public TestScroller()
-            {
-                LayoutManager = new LayoutManager(this);
-            }
-
-            public IRenderer Renderer { get; }
-            public Size ClientSize { get; }
-            public double RenderScaling => 1;
-
-            public Size MaxClientSize => Size.Infinity;
-
-            public double LayoutScaling => 1;
-
-            public ILayoutManager LayoutManager { get; }
-
-            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-            public void Invalidate(Rect rect) => throw new NotImplementedException();
-            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-        }
-
-        private class TestItemsPresenter : ItemsPresenter
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator()
-            {
-                return new ItemContainerGenerator<TestContainer>(
-                    this,
-                    TestContainer.ContentProperty,
-                    null);
-            }
-        }
-
-        private class TestContainer : ContentControl
-        {
-            public TestContainer()
-            {
-                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
-                {
-                    Name = "PART_ContentPresenter",
-                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
-                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
-                }.RegisterInNameScope(scope));
-            }
-        }
-    }
-}
+////                var from = target.Panel.Children[5];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Same(target.Panel.Children[6], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[9];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[9], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 100;
+////                scroller.Height = 95;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[8];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Down,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[8], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
+////            {
+////                var target = CreateTarget();
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 100;
+////                scroller.Height = 95;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
+
+////                var from = target.Panel.Children[1];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Up,
+////                    from);
+
+////                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[0], result);
+////            }
+
+////            [Fact]
+////            public void Should_Return_Horizontal_Extent_And_Viewport()
+////            {
+////                var target = CreateTarget();
+
+////                target.ApplyTemplate();
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
+////                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
+////            }
+
+////            [Fact]
+////            public void Horizontal_Scroll_Should_Update_Item_Position()
+////            {
+////                var target = CreateTarget();
+
+////                target.ApplyTemplate();
+
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
+
+////                target.Measure(new Size(5, 100));
+////                target.Arrange(new Rect(0, 0, 5, 100));
+
+////                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
+////            }
+////        }
+
+////        public class Horizontal
+////        {
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[5];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Same(target.Panel.Children[6], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[9];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[9], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 95;
+////                scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+
+////                var from = target.Panel.Children[8];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Right,
+////                    from);
+
+////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[8], result);
+////            }
+
+////            [Fact]
+////            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
+////            {
+////                var target = CreateTarget(orientation: Orientation.Horizontal);
+////                var scroller = (TestScroller)target.Parent;
+
+////                scroller.Width = 95;
+////                scroller.Height = 100;
+////                scroller.LayoutManager.ExecuteInitialLayoutPass();
+////                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
+
+////                var from = target.Panel.Children[1];
+////                var result = ((ILogicalScrollable)target).GetControlInDirection(
+////                    NavigationDirection.Left,
+////                    from);
+
+////                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
+////                Assert.Same(target.Panel.Children[0], result);
+////            }
+////        }
+
+////        private static ItemsPresenter CreateTarget(
+////            Orientation orientation = Orientation.Vertical,
+////            int itemCount = 20,
+////            bool useAvaloniaList = false)
+////        {
+////            ItemsPresenter result;
+////            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
+////            var items = useAvaloniaList ?
+////                (IEnumerable)new AvaloniaList<string>(itemsSource) :
+////                (IEnumerable)new ObservableCollection<string>(itemsSource);
+
+////            var scroller = new TestScroller
+////            {
+////                CanHorizontallyScroll = true,
+////                CanVerticallyScroll = true,
+////                Content = result = new TestItemsPresenter
+////                {
+////                    Items = items,
+////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
+////                    DataTemplates = { StringDataTemplate() },
+////                    VirtualizationMode = ItemVirtualizationMode.Simple,
+////                }
+////            };
+
+////            scroller.UpdateChild();
+////            return result;
+////        }
+
+////        private static IDataTemplate StringDataTemplate()
+////        {
+////            return new FuncDataTemplate<string>((x, _) => new Canvas
+////            {
+////                Width = 10,
+////                Height = 10,
+////            });
+////        }
+
+////        private static ITemplate<Panel> VirtualizingPanelTemplate(
+////            Orientation orientation = Orientation.Vertical)
+////        {
+////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
+////            {
+////                Orientation = orientation,
+////            });
+////        }
+
+////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
+////        {
+////            public TestScroller()
+////            {
+////                LayoutManager = new LayoutManager(this);
+////            }
+
+////            public IRenderer Renderer { get; }
+////            public Size ClientSize { get; }
+////            public double RenderScaling => 1;
+
+////            public Size MaxClientSize => Size.Infinity;
+
+////            public double LayoutScaling => 1;
+
+////            public ILayoutManager LayoutManager { get; }
+
+////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
+////            public void Invalidate(Rect rect) => throw new NotImplementedException();
+////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
+////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
+////        }
+
+////        private class TestItemsPresenter : ItemsPresenter
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator()
+////            {
+////                return new ItemContainerGenerator<TestContainer>(
+////                    this,
+////                    TestContainer.ContentProperty,
+////                    null);
+////            }
+////        }
+
+////        private class TestContainer : ContentControl
+////        {
+////            public TestContainer()
+////            {
+////                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
+////                {
+////                    Name = "PART_ContentPresenter",
+////                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
+////                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
+////                }.RegisterInNameScope(scope));
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
index d4193d33ee..a9e1c65c50 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
@@ -1115,10 +1115,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             {
                 Name = "popup",
                 PlacementTarget = control,
-                Child = new ItemsPresenter
-                {
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
-                }
+                Child = new ItemsPresenter(),
             }.RegisterInNameScope(scope);
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index e20c03f67f..2c57c20b6c 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -2090,9 +2090,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 new ItemsPresenter
                 {
                     Name = "itemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
-                    [~ItemsPresenter.VirtualizationModeProperty] = control[~ListBox.VirtualizationModeProperty],
                 }.RegisterInNameScope(scope));
         }
 
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
index d2537a0635..c3e37666f7 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_AutoSelect.cs
@@ -125,7 +125,6 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 new ItemsPresenter
                 {
                     Name = "itemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index bc6147d64c..efce0a715c 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -1536,7 +1536,6 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = control[~ItemsControl.ItemsProperty],
                     [~ItemsPresenter.ItemsPanelProperty] = control[~ItemsControl.ItemsPanelProperty],
                 }.RegisterInNameScope(scope));
         }
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
index b1e18dc587..05183fe787 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/TabStripTests.cs
@@ -106,7 +106,6 @@ namespace Avalonia.Controls.UnitTests.Primitives
             return new ItemsPresenter
             {
                 Name = "itemsPresenter",
-                [!ItemsPresenter.ItemsProperty] = parent[!ItemsControl.ItemsProperty],
             }.RegisterInNameScope(scope);
         }
     }
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 4f0446d406..8be1e112e7 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1303,7 +1303,6 @@ namespace Avalonia.Controls.UnitTests
             return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
             {
                 Name = "PART_ItemsPresenter",
-                [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
             }.RegisterInNameScope(scope));
         }
 
@@ -1321,7 +1320,6 @@ namespace Avalonia.Controls.UnitTests
                     new ItemsPresenter
                     {
                         Name = "PART_ItemsPresenter",
-                        [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                     }.RegisterInNameScope(scope)
                 }
             });
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index b80df2c5d3..6270d698e7 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -1,261 +1,261 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Primitives;
-using Avalonia.Input;
-using Avalonia.LogicalTree;
-using Moq;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class VirtualizingStackPanelTests
-    {
-        public class Vertical
-        {
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Once());
-            }
-
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 101));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.InvalidateMeasure();
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Once());
-            }
-
-            [Fact]
-            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
-                target.Measure(new Size(100, 100));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Arrange_Invokes_Controller_UpdateControls()
-            {
-                var target = new VirtualizingStackPanel();
-                var controller = new Mock<IVirtualizingController>();
-
-                ((IVirtualizingPanel)target).Controller = controller.Object;
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(0, 0, 110, 110));
-
-                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-            }
-
-            [Fact]
-            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Measure(new Size(100, 100));
-
-                Assert.Equal(new Size(0, 0), target.DesiredSize);
-                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-                Assert.False(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.False(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.True(vp.IsFull);
-                Assert.Equal(0, vp.OverflowCount);
-            }
-
-            [Fact]
-            public void Reports_Overflow_After_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                Assert.Equal(0, vp.OverflowCount);
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, vp.OverflowCount);
-            }
-
-            [Fact]
-            public void Reports_Correct_Overflow_During_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-                var controller = new Mock<IVirtualizingController>();
-                var called = false;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                target.Measure(new Size(100, 100));
-
-                controller.Setup(x => x.UpdateControls()).Callback(() =>
-                {
-                    Assert.Equal(2, vp.PixelOverflow);
-                    Assert.Equal(0, vp.OverflowCount);
-                    called = true;
-                });
-
-                vp.Controller = controller.Object;
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.True(called);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_After_Arrange()
-            {
-                var target = new VirtualizingStackPanel();
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
-            {
-                var target = new VirtualizingStackPanel();
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(0, 0, 50, 50));
-
-                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
-            }
-
-            [Fact]
-            public void Reports_PixelOverflow_With_PixelOffset()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                vp.PixelOffset = 2;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(2, vp.PixelOverflow);
-            }
-
-            [Fact]
-            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
-            {
-                var target = new VirtualizingStackPanel();
-                var vp = (IVirtualizingPanel)target;
-
-                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-                vp.PixelOffset = 55;
-
-                target.Measure(new Size(100, 100));
-                target.Arrange(new Rect(target.DesiredSize));
-
-                Assert.Equal(55, vp.PixelOffset);
-                Assert.Equal(2, vp.PixelOverflow);
-                Assert.True(vp.IsFull);
-            }
-
-            [Fact]
-            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
-            {
-                var target = new VirtualizingStackPanel();
-                var presenter = new TestPresenter { Child = target };
-                var from = new Canvas();
-
-                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
-
-                Assert.Equal(1, presenter.NavigationRequests.Count);
-                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
-            }
-
-            private class TestPresenter : Decorator, ILogicalScrollable
-            {
-                public bool CanHorizontallyScroll { get; set; }
-                public bool CanVerticallyScroll { get; set; }
-                public bool IsLogicalScrollEnabled => true;
-                public Size ScrollSize { get; }
-                public Size PageScrollSize { get; }
-                public Size Extent { get; }
-                public Vector Offset { get; set; }
-                public Size Viewport { get; }
-
-                public event EventHandler ScrollInvalidated;
-
-                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
-
-                public bool BringIntoView(Control target, Rect targetRect)
-                {
-                    throw new NotImplementedException();
-                }
-
-                public Control GetControlInDirection(NavigationDirection direction, Control from)
-                {
-                    NavigationRequests.Add((direction, from));
-                    return null;
-                }
-
-                public void RaiseScrollInvalidated(EventArgs e)
-                {
-                    throw new NotImplementedException();
-                }
-            }
-        }
-    }
-}
+////using System;
+////using System.Collections.Generic;
+////using Avalonia.Controls.Primitives;
+////using Avalonia.Input;
+////using Avalonia.LogicalTree;
+////using Moq;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class VirtualizingStackPanelTests
+////    {
+////        public class Vertical
+////        {
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Once());
+////            }
+
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 101));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.InvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Once());
+////            }
+
+////            [Fact]
+////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
+////                target.Measure(new Size(100, 100));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Arrange_Invokes_Controller_UpdateControls()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var controller = new Mock<IVirtualizingController>();
+
+////                ((IVirtualizingPanel)target).Controller = controller.Object;
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(0, 0, 110, 110));
+
+////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
+////            }
+
+////            [Fact]
+////            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Measure(new Size(100, 100));
+
+////                Assert.Equal(new Size(0, 0), target.DesiredSize);
+////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
+
+////                Assert.False(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.False(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.True(vp.IsFull);
+////                Assert.Equal(0, vp.OverflowCount);
+////            }
+
+////            [Fact]
+////            public void Reports_Overflow_After_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                Assert.Equal(0, vp.OverflowCount);
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, vp.OverflowCount);
+////            }
+
+////            [Fact]
+////            public void Reports_Correct_Overflow_During_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+////                var controller = new Mock<IVirtualizingController>();
+////                var called = false;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                target.Measure(new Size(100, 100));
+
+////                controller.Setup(x => x.UpdateControls()).Callback(() =>
+////                {
+////                    Assert.Equal(2, vp.PixelOverflow);
+////                    Assert.Equal(0, vp.OverflowCount);
+////                    called = true;
+////                });
+
+////                vp.Controller = controller.Object;
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.True(called);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_After_Arrange()
+////            {
+////                var target = new VirtualizingStackPanel();
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
+////            {
+////                var target = new VirtualizingStackPanel();
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(0, 0, 50, 50));
+
+////                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void Reports_PixelOverflow_With_PixelOffset()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                vp.PixelOffset = 2;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(2, vp.PixelOverflow);
+////            }
+
+////            [Fact]
+////            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var vp = (IVirtualizingPanel)target;
+
+////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
+////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
+////                vp.PixelOffset = 55;
+
+////                target.Measure(new Size(100, 100));
+////                target.Arrange(new Rect(target.DesiredSize));
+
+////                Assert.Equal(55, vp.PixelOffset);
+////                Assert.Equal(2, vp.PixelOverflow);
+////                Assert.True(vp.IsFull);
+////            }
+
+////            [Fact]
+////            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
+////            {
+////                var target = new VirtualizingStackPanel();
+////                var presenter = new TestPresenter { Child = target };
+////                var from = new Canvas();
+
+////                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
+
+////                Assert.Equal(1, presenter.NavigationRequests.Count);
+////                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
+////            }
+
+////            private class TestPresenter : Decorator, ILogicalScrollable
+////            {
+////                public bool CanHorizontallyScroll { get; set; }
+////                public bool CanVerticallyScroll { get; set; }
+////                public bool IsLogicalScrollEnabled => true;
+////                public Size ScrollSize { get; }
+////                public Size PageScrollSize { get; }
+////                public Size Extent { get; }
+////                public Vector Offset { get; set; }
+////                public Size Viewport { get; }
+
+////                public event EventHandler ScrollInvalidated;
+
+////                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
+
+////                public bool BringIntoView(Control target, Rect targetRect)
+////                {
+////                    throw new NotImplementedException();
+////                }
+
+////                public Control GetControlInDirection(NavigationDirection direction, Control from)
+////                {
+////                    NavigationRequests.Add((direction, from));
+////                    return null;
+////                }
+
+////                public void RaiseScrollInvalidated(EventArgs e)
+////                {
+////                    throw new NotImplementedException();
+////                }
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs b/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
index 53bdff5dff..c00303f4f8 100644
--- a/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
+++ b/tests/Avalonia.ReactiveUI.UnitTests/AutoDataTemplateBindingHookTest.cs
@@ -139,7 +139,6 @@ namespace Avalonia.ReactiveUI.UnitTests
                 Child = new ItemsPresenter
                 {
                     Name = "PART_ItemsPresenter",
-                    [~ItemsPresenter.ItemsProperty] = parent[~ItemsControl.ItemsProperty],
                 }.RegisterInNameScope(scope)
             });
         }
diff --git a/tests/Avalonia.UnitTests/TestExtensions.cs b/tests/Avalonia.UnitTests/TestExtensions.cs
index 1bbf84e88d..21a67a8800 100644
--- a/tests/Avalonia.UnitTests/TestExtensions.cs
+++ b/tests/Avalonia.UnitTests/TestExtensions.cs
@@ -9,6 +9,5 @@ namespace Avalonia.UnitTests
     public static class TestExtensions
     {
         public static void ApplyTemplate(this IContentPresenter presenter) => ((Layoutable)presenter).ApplyTemplate();
-        public static void ApplyTemplate(this IItemsPresenter presenter) => ((Layoutable)presenter).ApplyTemplate();
     }
 }

From c20e3c29e6965f6f6a6cf52aa08fc38f5de37ae0 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 25 Nov 2022 12:28:35 +0100
Subject: [PATCH 007/157] Initial (re)impl of VirtualizingStackPanel.

Currently only supports smooth scrolling.
---
 .../IVirtualizingController.cs                |  19 -
 src/Avalonia.Controls/IVirtualizingPanel.cs   |  11 -
 .../ItemVirtualizationMode.cs                 |   5 +
 src/Avalonia.Controls/ListBox.cs              |   2 +-
 .../Presenters/ItemsPresenter.cs              |  43 +-
 .../ItemsPresenterContainerGenerator.cs       |  10 +-
 .../Primitives/SelectingItemsControl.cs       |   2 +-
 .../Utils/CollectionUtils.cs                  |  49 ++
 src/Avalonia.Controls/VirtualizingPanel.cs    |  95 +++
 .../VirtualizingStackPanel.Smooth.cs          | 662 ++++++++++++++++++
 .../VirtualizingStackPanel.cs                 | 125 +++-
 .../VirtualizingStackPanelTests.cs            | 261 -------
 .../VirtualizingStackPanelTests_Smooth.cs     | 197 ++++++
 13 files changed, 1161 insertions(+), 320 deletions(-)
 delete mode 100644 src/Avalonia.Controls/IVirtualizingController.cs
 delete mode 100644 src/Avalonia.Controls/IVirtualizingPanel.cs
 create mode 100644 src/Avalonia.Controls/Utils/CollectionUtils.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingPanel.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
 create mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs

diff --git a/src/Avalonia.Controls/IVirtualizingController.cs b/src/Avalonia.Controls/IVirtualizingController.cs
deleted file mode 100644
index 7c87f8abbc..0000000000
--- a/src/Avalonia.Controls/IVirtualizingController.cs
+++ /dev/null
@@ -1,19 +0,0 @@
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// Interface implemented by controls that act as controllers for an
-    /// <see cref="IVirtualizingPanel"/>.
-    /// </summary>
-    public interface IVirtualizingController
-    {
-        /// <summary>
-        /// Called when the <see cref="IVirtualizingPanel"/>'s controls should be updated.
-        /// </summary>
-        /// <remarks>
-        /// The controller should respond to this method being called by either adding
-        /// children up until <see cref="IVirtualizingPanel.IsFull"/> becomes true or
-        /// removing <see cref="IVirtualizingPanel.OverflowCount"/> controls.
-        /// </remarks>
-        void UpdateControls();
-    }
-}
diff --git a/src/Avalonia.Controls/IVirtualizingPanel.cs b/src/Avalonia.Controls/IVirtualizingPanel.cs
deleted file mode 100644
index eff469f37a..0000000000
--- a/src/Avalonia.Controls/IVirtualizingPanel.cs
+++ /dev/null
@@ -1,11 +0,0 @@
-using Avalonia.Layout;
-
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// A panel that can be used to virtualize items.
-    /// </summary>
-    public interface IVirtualizingPanel
-    {
-    }
-}
diff --git a/src/Avalonia.Controls/ItemVirtualizationMode.cs b/src/Avalonia.Controls/ItemVirtualizationMode.cs
index 1950bb7f20..66dd32d28c 100644
--- a/src/Avalonia.Controls/ItemVirtualizationMode.cs
+++ b/src/Avalonia.Controls/ItemVirtualizationMode.cs
@@ -14,5 +14,10 @@
         /// Virtualize items without smooth scrolling.
         /// </summary>
         Simple,
+
+        /// <summary>
+        /// Virtualize items with smooth scrolling.
+        /// </summary>
+        Smooth,
     }
 }
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 0adc8a61ba..cb9f2f42ef 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -61,7 +61,7 @@ namespace Avalonia.Controls
         static ListBox()
         {
             ItemsPanelProperty.OverrideDefaultValue<ListBox>(DefaultPanel);
-            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Simple);
+            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Smooth);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 2a52e00d67..b731f48d9c 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,6 +1,3 @@
-using System;
-using System.Collections;
-using System.Collections.Specialized;
 using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
@@ -39,46 +36,62 @@ namespace Avalonia.Controls.Presenters
 
         public override sealed void ApplyTemplate()
         {
-            if (Panel is null)
+            if (Panel is null && ItemsControl is not null)
             {
                 Panel = ItemsPanel.Build();
                 Panel.SetValue(TemplatedParentProperty, TemplatedParent);
                 LogicalChildren.Add(Panel);
                 VisualChildren.Add(Panel);
-                CreateGeneratorIfSimplePanel();
+
+                if (Panel is VirtualizingPanel v)
+                    v.Attach(ItemsControl);
+                else
+                    CreateSimplePanelGenerator();
             }
         }
 
+        internal void ScrollIntoView(int index)
+        {
+
+        }
+
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
         {
             base.OnPropertyChanged(change);
 
             if (change.Property == TemplatedParentProperty)
             {
-                _generator?.Dispose();
-                _generator = null;
+                ResetState();
+                ItemsControl = null;
 
                 if (change.NewValue is ItemsControl itemsControl)
                 {
                     ItemsControl = itemsControl;
                     ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
-                    CreateGeneratorIfSimplePanel();
                 }
             }
             else if (change.Property == ItemsPanelProperty)
             {
-                _generator?.Dispose();
-                _generator = null;
-                LogicalChildren.Clear();
-                VisualChildren.Clear();
-                Panel = null;
+                ResetState();
                 InvalidateMeasure();
             }
         }
 
-        private void CreateGeneratorIfSimplePanel()
+        private void ResetState()
         {
-            if (ItemsControl is null || Panel is null || Panel is IVirtualizingPanel)
+            _generator?.Dispose();
+            _generator = null;
+            LogicalChildren.Clear();
+            VisualChildren.Clear();
+            (Panel as VirtualizingPanel)?.Detach();
+            Panel = null;
+        }
+
+        private void CreateSimplePanelGenerator()
+        {
+            Debug.Assert(Panel is not VirtualizingPanel);
+
+            if (ItemsControl is null || Panel is null)
                 return;
 
             _generator?.Dispose();
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
index 4c2bd35f5a..233635a414 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
@@ -2,6 +2,7 @@
 using System.Collections;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using Avalonia.Controls.Utils;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -10,13 +11,12 @@ namespace Avalonia.Controls.Presenters
     /// </summary>
     internal class ItemsPresenterContainerGenerator : IDisposable
     {
-        private static NotifyCollectionChangedEventArgs s_Reset = new(NotifyCollectionChangedAction.Reset);
-        private ItemsPresenter _presenter;
+        private readonly ItemsPresenter _presenter;
 
         public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
         {
             Debug.Assert(presenter.ItemsControl is not null);
-            Debug.Assert(presenter.Panel is not null or IVirtualizingPanel);
+            Debug.Assert(presenter.Panel is not null or VirtualizingPanel);
             
             _presenter = presenter;
             _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
@@ -24,7 +24,7 @@ namespace Avalonia.Controls.Presenters
             if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
                 incc.CollectionChanged += OnItemsChanged;
 
-            OnItemsChanged(null, s_Reset);
+            OnItemsChanged(null, CollectionUtils.ResetEventArgs);
         }
 
         public void Dispose()
@@ -43,7 +43,7 @@ namespace Avalonia.Controls.Presenters
             {
                 if (e.OldValue is INotifyCollectionChanged inccOld)
                     inccOld.CollectionChanged -= OnItemsChanged;
-                OnItemsChanged(null, s_Reset);
+                OnItemsChanged(null, CollectionUtils.ResetEventArgs);
                 if (e.NewValue is INotifyCollectionChanged inccNew)
                     inccNew.CollectionChanged += OnItemsChanged;
             }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 7f8d8f098a..44fa78ac21 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -373,7 +373,7 @@ namespace Avalonia.Controls.Primitives
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        public void ScrollIntoView(int index) => throw new NotImplementedException(); ////Presenter?.ScrollIntoView(index);
+        public void ScrollIntoView(int index) => Presenter?.ScrollIntoView(index);
 
         /// <summary>
         /// Scrolls the specified item into view.
diff --git a/src/Avalonia.Controls/Utils/CollectionUtils.cs b/src/Avalonia.Controls/Utils/CollectionUtils.cs
new file mode 100644
index 0000000000..8db5564557
--- /dev/null
+++ b/src/Avalonia.Controls/Utils/CollectionUtils.cs
@@ -0,0 +1,49 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Controls.Utils
+{
+    internal static class CollectionUtils
+    {
+        public static NotifyCollectionChangedEventArgs ResetEventArgs { get; } = new(NotifyCollectionChangedAction.Reset);
+
+        public static void InsertMany<T>(this List<T> list, int index, T item, int count)
+        {
+            var repeat = FastRepeat<T>.Instance;
+            repeat.Count = count;
+            repeat.Item = item;
+            list.InsertRange(index, FastRepeat<T>.Instance);
+            repeat.Item = default;
+        }
+
+        private class FastRepeat<T> : ICollection<T>
+        {
+            public static readonly FastRepeat<T> Instance = new();
+            public int Count { get; set; }
+            public bool IsReadOnly => true;
+            [AllowNull] public T Item { get; set; }
+            public void Add(T item) => throw new NotImplementedException();
+            public void Clear() => throw new NotImplementedException();
+            public bool Contains(T item) => throw new NotImplementedException();
+            public bool Remove(T item) => throw new NotImplementedException();
+            IEnumerator IEnumerable.GetEnumerator() => throw new NotImplementedException();
+            public IEnumerator<T> GetEnumerator() => throw new NotImplementedException();
+
+            public void CopyTo(T[] array, int arrayIndex)
+            {
+                var end = arrayIndex + Count;
+
+                for (var i = arrayIndex; i < end; ++i)
+                {
+                    array[i] = Item;
+                }
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
new file mode 100644
index 0000000000..19b1c4002c
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -0,0 +1,95 @@
+using System.Collections;
+using System.Collections.Specialized;
+using Avalonia.Controls.Utils;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// Base class for panels that can be used to virtualize items.
+    /// </summary>
+    public abstract class VirtualizingPanel : Panel
+    {
+        private ItemsControl? _itemsControl;
+
+        protected ItemsControl? ItemsControl 
+        {
+            get => _itemsControl;
+            private set
+            {
+                if (_itemsControl != value)
+                {
+                    var oldValue = _itemsControl;
+                    _itemsControl= value;
+                    OnItemsControlChanged(oldValue);
+                }
+            }
+        }
+
+        /// <summary>
+        /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
+        /// </summary>
+        /// <param name="oldValue">
+        /// The old value of the <see cref="ItemsControl"/> property.
+        /// </param>
+        protected virtual void OnItemsControlChanged(ItemsControl? oldValue)
+        {
+        }
+
+        /// <summary>
+        /// Called when the <see cref="ItemsControl.Items"/> collection of the owner
+        /// <see cref="ItemsControl"/> changes.
+        /// </summary>
+        /// <param name="items">The items.</param>
+        /// <param name="e">The event args.</param>
+        /// <remarks>
+        /// This method is called a <see cref="INotifyCollectionChanged"/> event is raised by
+        /// the items, or when the <see cref="ItemsControl.Items"/> property is assigned a
+        /// new collection, in which case the <see cref="NotifyCollectionChangedAction"/> will
+        /// be <see cref="NotifyCollectionChangedAction.Reset"/>.
+        /// </remarks>
+        protected virtual void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+        }
+
+        internal void Attach(ItemsControl itemsControl)
+        {
+            ItemsControl = itemsControl;
+            ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
+
+            if (ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged += OnItemsControlItemsChanged;
+        }
+
+        internal void Detach()
+        {
+            if (ItemsControl is null)
+                return;
+
+            ItemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
+
+            if (ItemsControl.Items is INotifyCollectionChanged incc)
+                incc.CollectionChanged -= OnItemsControlItemsChanged;
+
+            ItemsControl = null;
+            Children.Clear();
+        }
+
+        private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            if (e.Property == ItemsControl.ItemsProperty)
+            {
+                if (e.OldValue is INotifyCollectionChanged inccOld)
+                    inccOld.CollectionChanged -= OnItemsControlItemsChanged;
+                OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+                if (e.NewValue is INotifyCollectionChanged inccNew)
+                    inccNew.CollectionChanged += OnItemsControlItemsChanged;
+            }
+        }
+
+        private void OnItemsControlItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        {
+            if (_itemsControl?.Items is IList items)
+                OnItemsChanged(items, e);
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
new file mode 100644
index 0000000000..1f6d8319fb
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
@@ -0,0 +1,662 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics;
+using Avalonia.Controls.Utils;
+using Avalonia.Layout;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
+
+namespace Avalonia.Controls
+{
+    public partial class VirtualizingStackPanel : VirtualizingPanel
+    {
+        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
+        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _updateElementIndex;
+        private int _anchorIndex = -1;
+        private Control? _anchorElement;
+        private bool _isWaitingForViewportUpdate;
+        private double _lastEstimatedElementSizeU = 25;
+        private RealizedElementList? _measureElements;
+        private RealizedElementList? _realizedElements;
+        private Rect _viewport = s_invalidViewport;
+
+        private Size MeasureOverrideSmooth(Size availableSize)
+        {
+            if (!IsEffectivelyVisible)
+                return default;
+
+            var items = ItemsControl?.Items as IList;
+
+            if (items is null || items.Count == 0)
+            {
+                Children.Clear();
+                return default;
+            }
+
+            var orientation = Orientation;
+
+            _realizedElements ??= new();
+            _measureElements ??= new();
+
+            // If we're bringing an item into view, ignore any layout passes until we receive a new
+            // effective viewport.
+            if (_isWaitingForViewportUpdate)
+            {
+                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                return CalculateDesiredSize(orientation, items, sizeV);
+            }
+
+            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+            // - Horizontal layouts: U = horizontal, V = vertical
+            // - Vertical layouts: U = vertical, V = horizontal
+            var viewport = CalculateMeasureViewport(items);
+
+            // Recycle elements outside of the expected range.
+            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+
+            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+            // write to _realizedElements yet, only _measureElements.
+            GenerateElements(availableSize, ref viewport);
+
+            // Now we know what definitely fits, recycle anything left over.
+            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+
+            // And swap the measureElements and realizedElements collection.
+            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+            _measureElements.ResetForReuse();
+
+            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+        }
+
+        private Size ArrangeOverrideSmooth(Size finalSize)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            var orientation = Orientation;
+            var u = _realizedElements!.StartU;
+
+            for (var i = 0; i < _realizedElements.Count; ++i)
+            {
+                var e = _realizedElements.Elements[i];
+
+                if (e is object)
+                {
+                    var sizeU = _realizedElements.SizeU[i];
+                    var rect = orientation == Orientation.Horizontal ?
+                        new Rect(u, 0, sizeU, finalSize.Height) :
+                        new Rect(0, u, finalSize.Width, sizeU);
+                    e.Arrange(rect);
+                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                }
+            }
+
+            return finalSize;
+        }
+
+        private MeasureViewport CalculateMeasureViewport(IList items)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            // If the control has not yet been laid out then the effective viewport won't have been set.
+            // Try to work it out from an ancestor control.
+            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
+
+            // Get the viewport in the orientation direction.
+            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
+            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
+
+            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var estimatedElementSize = -1.0;
+            var itemCount = items?.Count ?? 0;
+
+            if (firstIndex == -1)
+            {
+                estimatedElementSize = EstimateElementSizeU();
+                firstIndex = (int)(viewportStart / estimatedElementSize);
+                firstIndexU = firstIndex * estimatedElementSize;
+            }
+
+            if (lastIndex == -1)
+            {
+                if (estimatedElementSize == -1)
+                    estimatedElementSize = EstimateElementSizeU();
+                lastIndex = (int)(viewportEnd / estimatedElementSize);
+            }
+
+            return new MeasureViewport
+            {
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
+                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                viewportUStart = viewportStart,
+                viewportUEnd = viewportEnd,
+                startU = firstIndexU,
+            };
+        }
+
+        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
+        {
+            var sizeU = EstimateElementSizeU() * items.Count;
+
+            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
+                throw new InvalidOperationException("Invalid calculated size.");
+
+            return orientation == Orientation.Horizontal ?
+                new Size(sizeU, sizeV) :
+                new Size(sizeV, sizeU);
+        }
+
+        private double EstimateElementSizeU()
+        {
+            var count = _realizedElements!.Count;
+            var divisor = 0.0;
+            var total = 0.0;
+
+            for (var i = 0; i < count; ++i)
+            {
+                if (_realizedElements.Elements[i] is object)
+                {
+                    total += _realizedElements.SizeU[i];
+                    ++divisor;
+                }
+            }
+
+            if (divisor == 0 || total == 0)
+                return _lastEstimatedElementSizeU;
+
+            _lastEstimatedElementSizeU = total / divisor;
+            return _lastEstimatedElementSizeU;
+        }
+
+        private Rect EstimateViewport()
+        {
+            var c = this.GetVisualParent();
+            var viewport = new Rect();
+
+            if (c is null)
+            {
+                return viewport;
+            }
+
+            while (c is not null)
+            {
+                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                {
+                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
+                        .TransformToAABB(transform);
+                    break;
+                }
+
+                c = c?.GetVisualParent();
+            }
+
+
+            return viewport;
+        }
+
+        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
+        {
+            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(_measureElements is not null);
+
+            var items = (IList)ItemsControl!.Items;
+            var horizontal = Orientation == Orientation.Horizontal;
+            var index = viewport.firstIndex;
+            var u = viewport.startU;
+
+            do
+            {
+                var e = GetOrCreateElement(items, index);
+                e.Measure(availableSize);
+
+                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
+                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
+
+                _measureElements!.Add(index, e, u, sizeU);
+                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
+
+                u += sizeU;
+                ++index;
+            } while (u < viewport.viewportUEnd && index < items.Count);
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            InvalidateHack(e);
+            return e;
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            if (_anchorIndex == index)
+                return _anchorElement;
+            return _realizedElements!.GetElement(index);
+        }
+
+        private Control GetRecycledOrCreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
+            Children.Add(c);
+            return c;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
+            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
+            Children.Remove(element);
+        }
+
+        private void UpdateElementIndex(Control element, int index)
+        {
+            // TODO: Implement this after we refactor ItemContainerGenerator.
+        }
+
+        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
+        {
+            _viewport = e.EffectiveViewport;
+            _isWaitingForViewportUpdate = false;
+            InvalidateMeasure();
+        }
+
+        private void OnItemsChangedSmooth(NotifyCollectionChangedEventArgs e)
+        {
+            if (_realizedElements is null)
+                return;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    ////RecycleAllElements();
+                    break;
+            }
+
+            InvalidateMeasure();
+        }
+
+        private static void InvalidateHack(Control c)
+        {
+            bool HasInvalidations(Control c)
+            {
+                if (!c.IsMeasureValid)
+                    return true;
+
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                    {
+                        if (!child.IsMeasureValid || HasInvalidations(child))
+                            return true;
+                    }
+                }
+
+                return false;
+            }
+
+            void Invalidate(Control c)
+            {
+                c.InvalidateMeasure();
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                        Invalidate(child);
+                }
+            }
+
+            if (HasInvalidations(c))
+                Invalidate(c);
+        }
+
+        /// <summary>
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// </summary>
+        internal class RealizedElementList
+        {
+            private int _firstIndex;
+            private List<Control?>? _elements;
+            private List<double>? _sizes;
+            private double _startU;
+
+            /// <summary>
+            /// Gets the number of realized elements.
+            /// </summary>
+            public int Count => _elements?.Count ?? 0;
+
+            /// <summary>
+            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+
+            /// <summary>
+            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+
+            /// <summary>
+            /// Gets the elements.
+            /// </summary>
+            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
+
+            /// <summary>
+            /// Gets the sizes of the elements on the primary axis.
+            /// </summary>
+            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
+
+            /// <summary>
+            /// Gets the position of the first element on the primary axis.
+            /// </summary>
+            public double StartU => _startU;
+
+            /// <summary>
+            /// Adds a newly realized element to the collection.
+            /// </summary>
+            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="element">The element.</param>
+            /// <param name="u">The position of the elemnt on the primary axis.</param>
+            /// <param name="sizeU">The size of the element on the primary axis.</param>
+            public void Add(int modelIndex, Control element, double u, double sizeU)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+
+                _elements ??= new List<Control?>();
+                _sizes ??= new List<double>();
+
+                if (Count == 0)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                    _startU = u;
+                    _firstIndex = modelIndex;
+                }
+                else if (modelIndex == LastModelIndex + 1)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                }
+                else if (modelIndex == FirstModelIndex - 1)
+                {
+                    --_firstIndex;
+                    _elements.Insert(0, element);
+                    _sizes.Insert(0, sizeU);
+                    _startU = u;
+                }
+                else
+                {
+                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
+                }
+            }
+
+            /// <summary>
+            /// Gets the element at the specified model index, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <returns>The element if realized; otherwise null.</returns>
+            public Control? GetElement(int modelIndex)
+            {
+                var index = modelIndex - FirstModelIndex;
+                if (index >= 0 && index < _elements?.Count)
+                    return _elements[index];
+                return null;
+            }
+
+            /// <summary>
+            /// Gets the element at the specified position on the primary axis, if realized.
+            /// </summary>
+            /// <param name="position">The position.</param>
+            /// <returns>
+            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
+            /// primary axis.
+            /// </returns>
+            public (int index, double position) GetElementAt(double position)
+            {
+                if (_sizes is null || position < StartU)
+                    return (-1, 0);
+
+                var u = StartU;
+                var i = FirstModelIndex;
+
+                foreach (var size in _sizes)
+                {
+                    var endU = u + size;
+                    if (position < endU)
+                        return (i, u);
+                    u += size;
+                    ++i;
+                }
+
+                return (-1, 0);
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being inserted into the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="count">The number of items inserted.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var index = modelIndex - first;
+
+                if (index < Count)
+                {
+                    // The insertion point affects the realized elements. Update the index of the
+                    // elements after the insertion point.
+                    var elementCount = _elements.Count;
+                    var start = Math.Max(index, 0);
+
+                    for (var i = start; i < elementCount; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i + count);
+                    }
+
+                    if (index <= 0)
+                    {
+                        // The insertion point was before the first element, update the first index.
+                        _firstIndex += count;
+                    }
+                    else
+                    {
+                        // The insertion point was within the realized elements, insert an empty space
+                        // in _elements and _sizes.
+                        _elements!.InsertMany(index, null, count);
+                        _sizes!.InsertMany(index, 0.0, count);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being removed from the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="count">The number of items removed.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsRemoved(
+                int modelIndex,
+                int count,
+                Action<Control, int> updateElementIndex,
+                Action<Control> recycleElement)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the removal start and end index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var last = LastModelIndex;
+                var startIndex = modelIndex - first;
+                var endIndex = (modelIndex + count) - first;
+
+                if (endIndex < 0)
+                {
+                    // The removed range was before the realized elements. Update the first index and
+                    // the indexes of the realized elements.
+                    _firstIndex -= count;
+
+                    for (var i = 0; i < _elements.Count; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, _firstIndex + i);
+                    }
+                }
+                else if (startIndex < _elements.Count)
+                {
+                    // Recycle and remove the affected elements.
+                    var start = Math.Max(startIndex, 0);
+                    var end = Math.Min(endIndex, _elements.Count);
+
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            recycleElement(element);
+                    }
+
+                    _elements.RemoveRange(start, end - start);
+                    _sizes!.RemoveRange(start, end - start);
+
+                    // If the remove started before and ended within our realized elements, then our new
+                    // first index will be the index where the remove started.
+                    if (startIndex <= 0 && end < last)
+                        _firstIndex = first = modelIndex;
+
+                    // Update the indexes of the elements after the removed range.
+                    end = _elements.Count;
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements before a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex > LastModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var endIndex = modelIndex - FirstModelIndex;
+
+                    for (var i = 0; i < endIndex; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(0, endIndex);
+                    _sizes!.RemoveRange(0, endIndex);
+                    _firstIndex = modelIndex;
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements after a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex < FirstModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var count = _elements.Count;
+
+                    for (var i = startIndex; i < count; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
+                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
+                }
+            }
+
+            /// <summary>
+            /// Recycles all realized elements.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleAllElements(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is object)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+
+            /// <summary>
+            /// Resets the element list and prepares it for reuse.
+            /// </summary>
+            public void ResetForReuse()
+            {
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+        }
+
+        private struct MeasureViewport
+        {
+            public int firstIndex;
+            public int estimatedLastIndex;
+            public double viewportUStart;
+            public double viewportUEnd;
+            public double measuredV;
+            public double startU;
+        }
+    }
+}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index ea94440bf1..78839c44b8 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,20 +1,131 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
-    public class VirtualizingStackPanel : StackPanel
+    public partial class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
+        /// Defines the <see cref="Orientation"/> property.
         /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.Register<VirtualizingStackPanel, ItemVirtualizationMode>(
-                nameof(VirtualizationMode));
+        public static readonly StyledProperty<Orientation> OrientationProperty =
+            StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
+        /// <summary>
+        /// Defines the VirtualizationMode attached property.
+        /// </summary>
+        public static readonly AttachedProperty<ItemVirtualizationMode> VirtualizationModeProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, ItemVirtualizationMode>(
+                "VirtualizationMode", ItemVirtualizationMode.None);
+
+        private ItemVirtualizationMode _virtualizationMode;
+
+        public VirtualizingStackPanel()
+        {
+            _recycleElement = RecycleElement;
+            _updateElementIndex = UpdateElementIndex;
+        }
+
+        /// <summary>
+        /// Gets or sets the axis along which items are laid out.
+        /// </summary>
+        /// <value>
+        /// One of the enumeration values that specifies the axis along which items are laid out.
+        /// The default is Vertical.
+        /// </value>
+        public Orientation Orientation
+        {
+            get => GetValue(OrientationProperty);
+            set => SetValue(OrientationProperty, value);
+        }
+
+        /// <summary>
+        /// Gets the current <see cref="ItemVirtualizationMode"/> in use for the panel.
+        /// </summary>
         public ItemVirtualizationMode VirtualizationMode
         {
-            get => GetValue(VirtualizationModeProperty);
-            set => SetValue(VirtualizationModeProperty, value);
+            get => _virtualizationMode;
+            set
+            {
+                if (_virtualizationMode != value)
+                {
+                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
+                        EffectiveViewportChanged -= OnEffectiveViewportChanged;
+
+                    _virtualizationMode = value;
+
+                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
+                        EffectiveViewportChanged += OnEffectiveViewportChanged;
+
+                    Children.Clear();
+                }
+            }
+        }
+
+        public static ItemVirtualizationMode GetVirtualizationMode(Control c)
+        {
+            return c.GetValue(VirtualizationModeProperty);
+        }
+
+        public static void SetVirtualizationMode(Control c, ItemVirtualizationMode value)
+        {
+            c.SetValue(VirtualizationModeProperty, value);
+        }
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => MeasureOverrideSmooth(availableSize),
+                _ => throw new NotImplementedException()
+            };
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => ArrangeOverrideSmooth(finalSize),
+                _ => throw new NotImplementedException()
+            };
+        }
+
+        protected override void OnItemsControlChanged(ItemsControl? oldValue)
+        {
+            base.OnItemsControlChanged(oldValue);
+            VirtualizationMode = ItemsControl is null ? ItemVirtualizationMode.None : GetVirtualizationMode(ItemsControl);
+        }
+
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+            switch (VirtualizationMode)
+            {
+                case ItemVirtualizationMode.Smooth:
+                    OnItemsChangedSmooth(e);
+                    break;
+            }
+        }
+
+        internal IReadOnlyList<Control?> GetRealizedElements()
+        {
+            return VirtualizationMode switch
+            {
+                ItemVirtualizationMode.Smooth => _realizedElements?.Elements ?? Array.Empty<Control>(),
+                _ => Children,
+            };
+        }
+
+        private protected override void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        {
+            base.OnItemsControlPropertyChanged(sender, e);
+
+            if (e.Property == VirtualizationModeProperty)
+            {
+                VirtualizationMode = e.GetNewValue<ItemVirtualizationMode>();
+            }
         }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
deleted file mode 100644
index 6270d698e7..0000000000
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ /dev/null
@@ -1,261 +0,0 @@
-////using System;
-////using System.Collections.Generic;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Input;
-////using Avalonia.LogicalTree;
-////using Moq;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class VirtualizingStackPanelTests
-////    {
-////        public class Vertical
-////        {
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Once());
-////            }
-
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Changes()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 101));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Measure_Does_Not_Invoke_Controller_UpdateControls_If_AvailableSize_Is_The_Same()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.InvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Once());
-////            }
-
-////            [Fact]
-////            public void Measure_Invokes_Controller_UpdateControls_If_AvailableSize_Is_The_Same_After_ForceInvalidateMeasure()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                ((IVirtualizingPanel)target).ForceInvalidateMeasure();
-////                target.Measure(new Size(100, 100));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Arrange_Invokes_Controller_UpdateControls()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var controller = new Mock<IVirtualizingController>();
-
-////                ((IVirtualizingPanel)target).Controller = controller.Object;
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(0, 0, 110, 110));
-
-////                controller.Verify(x => x.UpdateControls(), Times.Exactly(2));
-////            }
-
-////            [Fact]
-////            public void Reports_IsFull_False_Until_Measure_Height_Is_Reached()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Measure(new Size(100, 100));
-
-////                Assert.Equal(new Size(0, 0), target.DesiredSize);
-////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-////                Assert.False(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.False(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.True(vp.IsFull);
-////                Assert.Equal(0, vp.OverflowCount);
-////            }
-
-////            [Fact]
-////            public void Reports_Overflow_After_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(new Size(0, 0), target.Bounds.Size);
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                Assert.Equal(0, vp.OverflowCount);
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, vp.OverflowCount);
-////            }
-
-////            [Fact]
-////            public void Reports_Correct_Overflow_During_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-////                var controller = new Mock<IVirtualizingController>();
-////                var called = false;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                target.Measure(new Size(100, 100));
-
-////                controller.Setup(x => x.UpdateControls()).Callback(() =>
-////                {
-////                    Assert.Equal(2, vp.PixelOverflow);
-////                    Assert.Equal(0, vp.OverflowCount);
-////                    called = true;
-////                });
-
-////                vp.Controller = controller.Object;
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.True(called);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_After_Arrange()
-////            {
-////                var target = new VirtualizingStackPanel();
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, ((IVirtualizingPanel)target).PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_After_Arrange_Smaller_Than_Measure()
-////            {
-////                var target = new VirtualizingStackPanel();
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(0, 0, 50, 50));
-
-////                Assert.Equal(52, ((IVirtualizingPanel)target).PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void Reports_PixelOverflow_With_PixelOffset()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                vp.PixelOffset = 2;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(2, vp.PixelOverflow);
-////            }
-
-////            [Fact]
-////            public void PixelOffset_Can_Be_More_Than_Child_Without_Affecting_IsFull()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var vp = (IVirtualizingPanel)target;
-
-////                target.Children.Add(new Canvas { Width = 50, Height = 50 });
-////                target.Children.Add(new Canvas { Width = 50, Height = 52 });
-////                vp.PixelOffset = 55;
-
-////                target.Measure(new Size(100, 100));
-////                target.Arrange(new Rect(target.DesiredSize));
-
-////                Assert.Equal(55, vp.PixelOffset);
-////                Assert.Equal(2, vp.PixelOverflow);
-////                Assert.True(vp.IsFull);
-////            }
-
-////            [Fact]
-////            public void Passes_Navigation_Request_To_ILogicalScrollable_Parent()
-////            {
-////                var target = new VirtualizingStackPanel();
-////                var presenter = new TestPresenter { Child = target };
-////                var from = new Canvas();
-
-////                ((INavigableContainer)target).GetControl(NavigationDirection.Next, from, false);
-
-////                Assert.Equal(1, presenter.NavigationRequests.Count);
-////                Assert.Equal((NavigationDirection.Next, from), presenter.NavigationRequests[0]);
-////            }
-
-////            private class TestPresenter : Decorator, ILogicalScrollable
-////            {
-////                public bool CanHorizontallyScroll { get; set; }
-////                public bool CanVerticallyScroll { get; set; }
-////                public bool IsLogicalScrollEnabled => true;
-////                public Size ScrollSize { get; }
-////                public Size PageScrollSize { get; }
-////                public Size Extent { get; }
-////                public Vector Offset { get; set; }
-////                public Size Viewport { get; }
-
-////                public event EventHandler ScrollInvalidated;
-
-////                public List<(NavigationDirection, Control)> NavigationRequests { get; } = new();
-
-////                public bool BringIntoView(Control target, Rect targetRect)
-////                {
-////                    throw new NotImplementedException();
-////                }
-
-////                public Control GetControlInDirection(NavigationDirection direction, Control from)
-////                {
-////                    NavigationRequests.Add((direction, from));
-////                    return null;
-////                }
-
-////                public void RaiseScrollInvalidated(EventArgs e)
-////                {
-////                    throw new NotImplementedException();
-////                }
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
new file mode 100644
index 0000000000..7f7a956f2c
--- /dev/null
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
@@ -0,0 +1,197 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Layout;
+using Avalonia.LogicalTree;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class VirtualizingStackPanelTests_Smooth
+    {
+        [Fact]
+        public void Creates_Initial_Items()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            AssertRealizedItems(target, itemsControl, 0, 10);
+        }
+
+        [Fact]
+        public void Scrolls_Down_One_Item()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            scroll.Offset = new Vector(0, 10);
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 1, 10);
+        }
+
+        [Fact]
+        public void Scrolls_Down_More_Than_A_Page()
+        {
+            using var app = App();
+
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 20, 10);
+        }
+
+        [Fact]
+        public void Creates_Elements_For_Inserted_Item()
+        {
+            using var app = App();
+
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (IList)itemsControl.Items;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            items.Insert(2, "new");
+
+            Assert.Equal(11, target.GetRealizedElements().Count);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Blank space inserted in realized elements and subsequent row indexes updated.
+            Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9, 10 }, indexes);
+
+            var elements = target.GetRealizedElements().ToList();
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout an element for the new row is created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+
+            // But apart from the new row and the removed last row, all existing elements should be the same.
+            elements[2] = target.GetRealizedElements().ElementAt(2);
+            elements.RemoveAt(elements.Count - 1);
+            Assert.Equal(elements, target.GetRealizedElements());
+        }
+
+        [Fact]
+        public void Updates_Elements_On_Removed_Row()
+        {
+            using var app = App();
+
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (IList)itemsControl.Items;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toRecycle = target.GetRealizedElements().ElementAt(2);
+            items.RemoveAt(2);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements and subsequent row indexes updated.
+            Assert.Equal(Enumerable.Range(0, 9), indexes);
+
+            var elements = target.GetRealizedElements().ToList();
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout an element for the newly visible last row is created and indexes updated.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+
+            // And the removed row should now have been recycled as the last row.
+            elements.Add(toRecycle);
+            Assert.Equal(elements, target.GetRealizedElements());
+        }
+
+        private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
+        {
+            return target.GetRealizedElements()
+                .Select(x => x is null ? -1 : itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .ToList();
+        }
+
+        private static void AssertRealizedItems(
+            VirtualizingStackPanel target,
+            ItemsControl itemsControl,
+            int firstIndex,
+            int count)
+        {
+            var childIndexes = target.GetLogicalChildren()
+                .Select(x => itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .Where(x => x >= 0)
+                .OrderBy(x => x)
+                .ToList();
+            Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
+        }
+
+        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(int itemCount = 100)
+        {
+            var items = new ObservableCollection<string>(Enumerable.Range(0, itemCount).Select(x => $"Item {x}"));
+            var target = new VirtualizingStackPanel();
+            
+            var presenter = new ItemsPresenter
+            {
+                [~ItemsPresenter.ItemsPanelProperty] = new TemplateBinding(ItemsPresenter.ItemsPanelProperty),
+            };
+
+            var scroll = new ScrollViewer 
+            { 
+                Content = presenter,
+                Template = ScrollViewerTemplate(),
+            };
+
+            var itemsControl = new ItemsControl
+            {
+                Items = items,
+                Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
+                ItemsPanel = new FuncTemplate<Panel>(() => target),
+                ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
+                [VirtualizingStackPanel.VirtualizationModeProperty] = ItemVirtualizationMode.Smooth,
+            };
+
+            var root = new TestRoot(true, itemsControl);
+            root.ClientSize = new(100, 100);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+
+            return (target, scroll, itemsControl);
+        }
+
+        private static void Layout(Control target)
+        {
+            var root = (ILayoutRoot?)target.GetVisualRoot();
+            root?.LayoutManager.ExecuteLayoutPass();
+        }
+
+        private static IControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((x, ns) =>
+                new ScrollContentPresenter
+                {
+                    Name = "PART_ContentPresenter",
+                    [~ContentPresenter.ContentProperty] = x[~ContentControl.ContentProperty],
+                    [~~ScrollContentPresenter.ExtentProperty] = x[~~ScrollViewer.ExtentProperty],
+                    [~~ScrollContentPresenter.OffsetProperty] = x[~~ScrollViewer.OffsetProperty],
+                    [~~ScrollContentPresenter.ViewportProperty] = x[~~ScrollViewer.ViewportProperty],
+                    [~ScrollContentPresenter.CanHorizontallyScrollProperty] = x[~ScrollViewer.CanHorizontallyScrollProperty],
+                    [~ScrollContentPresenter.CanVerticallyScrollProperty] = x[~ScrollViewer.CanVerticallyScrollProperty],
+                }.RegisterInNameScope(ns));
+        }
+
+        private static IDisposable App() => UnitTestApplication.Start();
+    }
+}

From 5d1f9f4a0f387589b2aecd585e49a43b45b859d3 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 25 Nov 2022 20:39:27 +0100
Subject: [PATCH 008/157] Removed VirtualizationMode.

If you want a different virtualization mode, use a different panel.
---
 src/Avalonia.Controls/ComboBox.cs             |  15 -
 .../ItemVirtualizationMode.cs                 |  23 -
 src/Avalonia.Controls/ListBox.cs              |  16 -
 .../VirtualizingStackPanel.Smooth.cs          | 662 -----------------
 .../VirtualizingStackPanel.cs                 | 668 ++++++++++++++++--
 .../Diagnostics/Views/ConsoleView.xaml        |   3 +-
 .../Controls/ManagedFileChooser.xaml          |   1 -
 .../Controls/ManagedFileChooser.xaml          |   3 +-
 .../ComboBoxTests.cs                          |   1 -
 .../ListBoxTests.cs                           |   6 -
 .../Primitives/SelectingItemsControlTests.cs  |   1 -
 .../VirtualizingStackPanelTests_Smooth.cs     |   1 -
 tests/Avalonia.LeakTests/ControlTests.cs      |   1 -
 .../Xaml/StyleTests.cs                        |   1 -
 14 files changed, 617 insertions(+), 785 deletions(-)
 delete mode 100644 src/Avalonia.Controls/ItemVirtualizationMode.cs
 delete mode 100644 src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index f8b0ebbbce..41c17bd3e1 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -53,12 +53,6 @@ namespace Avalonia.Controls
         public static readonly DirectProperty<ComboBox, object?> SelectionBoxItemProperty =
             AvaloniaProperty.RegisterDirect<ComboBox, object?>(nameof(SelectionBoxItem), o => o.SelectionBoxItem);
 
-        /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ComboBox>();
-
         /// <summary>
         /// Defines the <see cref="PlaceholderText"/> property.
         /// </summary>
@@ -146,15 +140,6 @@ namespace Avalonia.Controls
             set { SetValue(PlaceholderForegroundProperty, value); }
         }
 
-        /// <summary>
-        /// Gets or sets the virtualization mode for the items.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
-
         /// <summary>
         /// Gets or sets the horizontal alignment of the content within the control.
         /// </summary>
diff --git a/src/Avalonia.Controls/ItemVirtualizationMode.cs b/src/Avalonia.Controls/ItemVirtualizationMode.cs
deleted file mode 100644
index 66dd32d28c..0000000000
--- a/src/Avalonia.Controls/ItemVirtualizationMode.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-namespace Avalonia.Controls
-{
-    /// <summary>
-    /// Describes the item virtualization method to use for a list.
-    /// </summary>
-    public enum ItemVirtualizationMode
-    {
-        /// <summary>
-        /// Do not virtualize items.
-        /// </summary>
-        None,
-
-        /// <summary>
-        /// Virtualize items without smooth scrolling.
-        /// </summary>
-        Simple,
-
-        /// <summary>
-        /// Virtualize items with smooth scrolling.
-        /// </summary>
-        Smooth,
-    }
-}
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index cb9f2f42ef..a8a926691a 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -47,12 +47,6 @@ namespace Avalonia.Controls
         public static readonly new StyledProperty<SelectionMode> SelectionModeProperty = 
             SelectingItemsControl.SelectionModeProperty;
 
-        /// <summary>
-        /// Defines the <see cref="VirtualizationMode"/> property.
-        /// </summary>
-        public static readonly StyledProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            VirtualizingStackPanel.VirtualizationModeProperty.AddOwner<ListBox>();
-
         private IScrollable? _scroll;
 
         /// <summary>
@@ -61,7 +55,6 @@ namespace Avalonia.Controls
         static ListBox()
         {
             ItemsPanelProperty.OverrideDefaultValue<ListBox>(DefaultPanel);
-            VirtualizationModeProperty.OverrideDefaultValue<ListBox>(ItemVirtualizationMode.Smooth);
         }
 
         /// <summary>
@@ -100,15 +93,6 @@ namespace Avalonia.Controls
             set { base.SelectionMode = value; }
         }
 
-        /// <summary>
-        /// Gets or sets the virtualization mode for the items.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return GetValue(VirtualizationModeProperty); }
-            set { SetValue(VirtualizationModeProperty, value); }
-        }
-
         /// <summary>
         /// Selects all items in the <see cref="ListBox"/>.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs b/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
deleted file mode 100644
index 1f6d8319fb..0000000000
--- a/src/Avalonia.Controls/VirtualizingStackPanel.Smooth.cs
+++ /dev/null
@@ -1,662 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.Specialized;
-using System.Diagnostics;
-using Avalonia.Controls.Utils;
-using Avalonia.Layout;
-using Avalonia.Utilities;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls
-{
-    public partial class VirtualizingStackPanel : VirtualizingPanel
-    {
-        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
-        private readonly Action<Control> _recycleElement;
-        private readonly Action<Control, int> _updateElementIndex;
-        private int _anchorIndex = -1;
-        private Control? _anchorElement;
-        private bool _isWaitingForViewportUpdate;
-        private double _lastEstimatedElementSizeU = 25;
-        private RealizedElementList? _measureElements;
-        private RealizedElementList? _realizedElements;
-        private Rect _viewport = s_invalidViewport;
-
-        private Size MeasureOverrideSmooth(Size availableSize)
-        {
-            if (!IsEffectivelyVisible)
-                return default;
-
-            var items = ItemsControl?.Items as IList;
-
-            if (items is null || items.Count == 0)
-            {
-                Children.Clear();
-                return default;
-            }
-
-            var orientation = Orientation;
-
-            _realizedElements ??= new();
-            _measureElements ??= new();
-
-            // If we're bringing an item into view, ignore any layout passes until we receive a new
-            // effective viewport.
-            if (_isWaitingForViewportUpdate)
-            {
-                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
-                return CalculateDesiredSize(orientation, items, sizeV);
-            }
-
-            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
-            // - Horizontal layouts: U = horizontal, V = vertical
-            // - Vertical layouts: U = vertical, V = horizontal
-            var viewport = CalculateMeasureViewport(items);
-
-            // Recycle elements outside of the expected range.
-            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
-
-            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
-            // write to _realizedElements yet, only _measureElements.
-            GenerateElements(availableSize, ref viewport);
-
-            // Now we know what definitely fits, recycle anything left over.
-            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
-
-            // And swap the measureElements and realizedElements collection.
-            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
-            _measureElements.ResetForReuse();
-
-            return CalculateDesiredSize(orientation, items, viewport.measuredV);
-        }
-
-        private Size ArrangeOverrideSmooth(Size finalSize)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            var orientation = Orientation;
-            var u = _realizedElements!.StartU;
-
-            for (var i = 0; i < _realizedElements.Count; ++i)
-            {
-                var e = _realizedElements.Elements[i];
-
-                if (e is object)
-                {
-                    var sizeU = _realizedElements.SizeU[i];
-                    var rect = orientation == Orientation.Horizontal ?
-                        new Rect(u, 0, sizeU, finalSize.Height) :
-                        new Rect(0, u, finalSize.Width, sizeU);
-                    e.Arrange(rect);
-                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
-                }
-            }
-
-            return finalSize;
-        }
-
-        private MeasureViewport CalculateMeasureViewport(IList items)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            // If the control has not yet been laid out then the effective viewport won't have been set.
-            // Try to work it out from an ancestor control.
-            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
-
-            // Get the viewport in the orientation direction.
-            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
-            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
-
-            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
-            var estimatedElementSize = -1.0;
-            var itemCount = items?.Count ?? 0;
-
-            if (firstIndex == -1)
-            {
-                estimatedElementSize = EstimateElementSizeU();
-                firstIndex = (int)(viewportStart / estimatedElementSize);
-                firstIndexU = firstIndex * estimatedElementSize;
-            }
-
-            if (lastIndex == -1)
-            {
-                if (estimatedElementSize == -1)
-                    estimatedElementSize = EstimateElementSizeU();
-                lastIndex = (int)(viewportEnd / estimatedElementSize);
-            }
-
-            return new MeasureViewport
-            {
-                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
-                viewportUStart = viewportStart,
-                viewportUEnd = viewportEnd,
-                startU = firstIndexU,
-            };
-        }
-
-        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
-        {
-            var sizeU = EstimateElementSizeU() * items.Count;
-
-            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
-                throw new InvalidOperationException("Invalid calculated size.");
-
-            return orientation == Orientation.Horizontal ?
-                new Size(sizeU, sizeV) :
-                new Size(sizeV, sizeU);
-        }
-
-        private double EstimateElementSizeU()
-        {
-            var count = _realizedElements!.Count;
-            var divisor = 0.0;
-            var total = 0.0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                if (_realizedElements.Elements[i] is object)
-                {
-                    total += _realizedElements.SizeU[i];
-                    ++divisor;
-                }
-            }
-
-            if (divisor == 0 || total == 0)
-                return _lastEstimatedElementSizeU;
-
-            _lastEstimatedElementSizeU = total / divisor;
-            return _lastEstimatedElementSizeU;
-        }
-
-        private Rect EstimateViewport()
-        {
-            var c = this.GetVisualParent();
-            var viewport = new Rect();
-
-            if (c is null)
-            {
-                return viewport;
-            }
-
-            while (c is not null)
-            {
-                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
-                {
-                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
-                        .TransformToAABB(transform);
-                    break;
-                }
-
-                c = c?.GetVisualParent();
-            }
-
-
-            return viewport;
-        }
-
-        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
-        {
-            Debug.Assert(ItemsControl?.Items is IList);
-            Debug.Assert(_measureElements is not null);
-
-            var items = (IList)ItemsControl!.Items;
-            var horizontal = Orientation == Orientation.Horizontal;
-            var index = viewport.firstIndex;
-            var u = viewport.startU;
-
-            do
-            {
-                var e = GetOrCreateElement(items, index);
-                e.Measure(availableSize);
-
-                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
-                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
-
-                _measureElements!.Add(index, e, u, sizeU);
-                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
-
-                u += sizeU;
-                ++index;
-            } while (u < viewport.viewportUEnd && index < items.Count);
-        }
-
-        private Control GetOrCreateElement(IList items, int index)
-        {
-            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
-            InvalidateHack(e);
-            return e;
-        }
-
-        private Control? GetRealizedElement(int index)
-        {
-            Debug.Assert(_realizedElements is not null);
-
-            if (_anchorIndex == index)
-                return _anchorElement;
-            return _realizedElements!.GetElement(index);
-        }
-
-        private Control GetRecycledOrCreateElement(IList items, int index)
-        {
-            Debug.Assert(ItemsControl is not null);
-
-            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
-            Children.Add(c);
-            return c;
-        }
-
-        private void RecycleElement(Control element)
-        {
-            Debug.Assert(ItemsControl is not null);
-
-            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
-            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
-            Children.Remove(element);
-        }
-
-        private void UpdateElementIndex(Control element, int index)
-        {
-            // TODO: Implement this after we refactor ItemContainerGenerator.
-        }
-
-        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
-        {
-            _viewport = e.EffectiveViewport;
-            _isWaitingForViewportUpdate = false;
-            InvalidateMeasure();
-        }
-
-        private void OnItemsChangedSmooth(NotifyCollectionChangedEventArgs e)
-        {
-            if (_realizedElements is null)
-                return;
-
-            switch (e.Action)
-            {
-                case NotifyCollectionChangedAction.Add:
-                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
-                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
-                    break;
-                case NotifyCollectionChangedAction.Remove:
-                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
-                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
-                    break;
-                case NotifyCollectionChangedAction.Reset:
-                    ////RecycleAllElements();
-                    break;
-            }
-
-            InvalidateMeasure();
-        }
-
-        private static void InvalidateHack(Control c)
-        {
-            bool HasInvalidations(Control c)
-            {
-                if (!c.IsMeasureValid)
-                    return true;
-
-                for (var i = 0; i < c.VisualChildren.Count; ++i)
-                {
-                    if (c.VisualChildren[i] is Control child)
-                    {
-                        if (!child.IsMeasureValid || HasInvalidations(child))
-                            return true;
-                    }
-                }
-
-                return false;
-            }
-
-            void Invalidate(Control c)
-            {
-                c.InvalidateMeasure();
-                for (var i = 0; i < c.VisualChildren.Count; ++i)
-                {
-                    if (c.VisualChildren[i] is Control child)
-                        Invalidate(child);
-                }
-            }
-
-            if (HasInvalidations(c))
-                Invalidate(c);
-        }
-
-        /// <summary>
-        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
-        /// </summary>
-        internal class RealizedElementList
-        {
-            private int _firstIndex;
-            private List<Control?>? _elements;
-            private List<double>? _sizes;
-            private double _startU;
-
-            /// <summary>
-            /// Gets the number of realized elements.
-            /// </summary>
-            public int Count => _elements?.Count ?? 0;
-
-            /// <summary>
-            /// Gets the model index of the first realized element, or -1 if no elements are realized.
-            /// </summary>
-            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
-
-            /// <summary>
-            /// Gets the model index of the last realized element, or -1 if no elements are realized.
-            /// </summary>
-            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
-
-            /// <summary>
-            /// Gets the elements.
-            /// </summary>
-            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
-
-            /// <summary>
-            /// Gets the sizes of the elements on the primary axis.
-            /// </summary>
-            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
-
-            /// <summary>
-            /// Gets the position of the first element on the primary axis.
-            /// </summary>
-            public double StartU => _startU;
-
-            /// <summary>
-            /// Adds a newly realized element to the collection.
-            /// </summary>
-            /// <param name="modelIndex">The model index of the element.</param>
-            /// <param name="element">The element.</param>
-            /// <param name="u">The position of the elemnt on the primary axis.</param>
-            /// <param name="sizeU">The size of the element on the primary axis.</param>
-            public void Add(int modelIndex, Control element, double u, double sizeU)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-
-                _elements ??= new List<Control?>();
-                _sizes ??= new List<double>();
-
-                if (Count == 0)
-                {
-                    _elements.Add(element);
-                    _sizes.Add(sizeU);
-                    _startU = u;
-                    _firstIndex = modelIndex;
-                }
-                else if (modelIndex == LastModelIndex + 1)
-                {
-                    _elements.Add(element);
-                    _sizes.Add(sizeU);
-                }
-                else if (modelIndex == FirstModelIndex - 1)
-                {
-                    --_firstIndex;
-                    _elements.Insert(0, element);
-                    _sizes.Insert(0, sizeU);
-                    _startU = u;
-                }
-                else
-                {
-                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
-                }
-            }
-
-            /// <summary>
-            /// Gets the element at the specified model index, if realized.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
-            /// <returns>The element if realized; otherwise null.</returns>
-            public Control? GetElement(int modelIndex)
-            {
-                var index = modelIndex - FirstModelIndex;
-                if (index >= 0 && index < _elements?.Count)
-                    return _elements[index];
-                return null;
-            }
-
-            /// <summary>
-            /// Gets the element at the specified position on the primary axis, if realized.
-            /// </summary>
-            /// <param name="position">The position.</param>
-            /// <returns>
-            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
-            /// primary axis.
-            /// </returns>
-            public (int index, double position) GetElementAt(double position)
-            {
-                if (_sizes is null || position < StartU)
-                    return (-1, 0);
-
-                var u = StartU;
-                var i = FirstModelIndex;
-
-                foreach (var size in _sizes)
-                {
-                    var endU = u + size;
-                    if (position < endU)
-                        return (i, u);
-                    u += size;
-                    ++i;
-                }
-
-                return (-1, 0);
-            }
-
-            /// <summary>
-            /// Updates the elements in response to items being inserted into the source collection.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the insert.</param>
-            /// <param name="count">The number of items inserted.</param>
-            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                // Get the index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var index = modelIndex - first;
-
-                if (index < Count)
-                {
-                    // The insertion point affects the realized elements. Update the index of the
-                    // elements after the insertion point.
-                    var elementCount = _elements.Count;
-                    var start = Math.Max(index, 0);
-
-                    for (var i = start; i < elementCount; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i + count);
-                    }
-
-                    if (index <= 0)
-                    {
-                        // The insertion point was before the first element, update the first index.
-                        _firstIndex += count;
-                    }
-                    else
-                    {
-                        // The insertion point was within the realized elements, insert an empty space
-                        // in _elements and _sizes.
-                        _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, 0.0, count);
-                    }
-                }
-            }
-
-            /// <summary>
-            /// Updates the elements in response to items being removed from the source collection.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the remove.</param>
-            /// <param name="count">The number of items removed.</param>
-            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void ItemsRemoved(
-                int modelIndex,
-                int count,
-                Action<Control, int> updateElementIndex,
-                Action<Control> recycleElement)
-            {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                // Get the removal start and end index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var last = LastModelIndex;
-                var startIndex = modelIndex - first;
-                var endIndex = (modelIndex + count) - first;
-
-                if (endIndex < 0)
-                {
-                    // The removed range was before the realized elements. Update the first index and
-                    // the indexes of the realized elements.
-                    _firstIndex -= count;
-
-                    for (var i = 0; i < _elements.Count; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, _firstIndex + i);
-                    }
-                }
-                else if (startIndex < _elements.Count)
-                {
-                    // Recycle and remove the affected elements.
-                    var start = Math.Max(startIndex, 0);
-                    var end = Math.Min(endIndex, _elements.Count);
-
-                    for (var i = start; i < end; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            recycleElement(element);
-                    }
-
-                    _elements.RemoveRange(start, end - start);
-                    _sizes!.RemoveRange(start, end - start);
-
-                    // If the remove started before and ended within our realized elements, then our new
-                    // first index will be the index where the remove started.
-                    if (startIndex <= 0 && end < last)
-                        _firstIndex = first = modelIndex;
-
-                    // Update the indexes of the elements after the removed range.
-                    end = _elements.Count;
-                    for (var i = start; i < end; ++i)
-                    {
-                        if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i);
-                    }
-                }
-            }
-
-            /// <summary>
-            /// Recycles elements before a specific index.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new first element.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
-            {
-                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
-                    return;
-
-                if (modelIndex > LastModelIndex)
-                {
-                    RecycleAllElements(recycleElement);
-                }
-                else
-                {
-                    var endIndex = modelIndex - FirstModelIndex;
-
-                    for (var i = 0; i < endIndex; ++i)
-                    {
-                        if (_elements[i] is Control e)
-                            recycleElement(e);
-                    }
-
-                    _elements.RemoveRange(0, endIndex);
-                    _sizes!.RemoveRange(0, endIndex);
-                    _firstIndex = modelIndex;
-                }
-            }
-
-            /// <summary>
-            /// Recycles elements after a specific index.
-            /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new last element.</param>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
-            {
-                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
-                    return;
-
-                if (modelIndex < FirstModelIndex)
-                {
-                    RecycleAllElements(recycleElement);
-                }
-                else
-                {
-                    var startIndex = (modelIndex + 1) - FirstModelIndex;
-                    var count = _elements.Count;
-
-                    for (var i = startIndex; i < count; ++i)
-                    {
-                        if (_elements[i] is Control e)
-                            recycleElement(e);
-                    }
-
-                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
-                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
-                }
-            }
-
-            /// <summary>
-            /// Recycles all realized elements.
-            /// </summary>
-            /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleAllElements(Action<Control> recycleElement)
-            {
-                if (_elements is null || _elements.Count == 0)
-                    return;
-
-                foreach (var e in _elements)
-                {
-                    if (e is object)
-                        recycleElement(e);
-                }
-
-                _startU = _firstIndex = 0;
-                _elements?.Clear();
-                _sizes?.Clear();
-            }
-
-            /// <summary>
-            /// Resets the element list and prepares it for reuse.
-            /// </summary>
-            public void ResetForReuse()
-            {
-                _startU = _firstIndex = 0;
-                _elements?.Clear();
-                _sizes?.Clear();
-            }
-        }
-
-        private struct MeasureViewport
-        {
-            public int firstIndex;
-            public int estimatedLastIndex;
-            public double viewportUStart;
-            public double viewportUEnd;
-            public double measuredV;
-            public double startU;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 78839c44b8..5d9b3b56b1 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -2,11 +2,15 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.Diagnostics;
+using Avalonia.Controls.Utils;
 using Avalonia.Layout;
+using Avalonia.Utilities;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
-    public partial class VirtualizingStackPanel : VirtualizingPanel
+    public class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
         /// Defines the <see cref="Orientation"/> property.
@@ -14,19 +18,22 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<Orientation> OrientationProperty =
             StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
-        /// <summary>
-        /// Defines the VirtualizationMode attached property.
-        /// </summary>
-        public static readonly AttachedProperty<ItemVirtualizationMode> VirtualizationModeProperty =
-            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, ItemVirtualizationMode>(
-                "VirtualizationMode", ItemVirtualizationMode.None);
-
-        private ItemVirtualizationMode _virtualizationMode;
+        private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
+        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _updateElementIndex;
+        private int _anchorIndex = -1;
+        private Control? _anchorElement;
+        private bool _isWaitingForViewportUpdate;
+        private double _lastEstimatedElementSizeU = 25;
+        private RealizedElementList? _measureElements;
+        private RealizedElementList? _realizedElements;
+        private Rect _viewport = s_invalidViewport;
 
         public VirtualizingStackPanel()
         {
             _recycleElement = RecycleElement;
             _updateElementIndex = UpdateElementIndex;
+            EffectiveViewportChanged += OnEffectiveViewportChanged;
         }
 
         /// <summary>
@@ -42,90 +49,645 @@ namespace Avalonia.Controls
             set => SetValue(OrientationProperty, value);
         }
 
-        /// <summary>
-        /// Gets the current <see cref="ItemVirtualizationMode"/> in use for the panel.
-        /// </summary>
-        public ItemVirtualizationMode VirtualizationMode
+        protected override Size MeasureOverride(Size availableSize)
         {
-            get => _virtualizationMode;
-            set
+            if (!IsEffectivelyVisible)
+                return default;
+
+            var items = ItemsControl?.Items as IList;
+
+            if (items is null || items.Count == 0)
             {
-                if (_virtualizationMode != value)
-                {
-                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
-                        EffectiveViewportChanged -= OnEffectiveViewportChanged;
+                Children.Clear();
+                return default;
+            }
+
+            var orientation = Orientation;
+
+            _realizedElements ??= new();
+            _measureElements ??= new();
+
+            // If we're bringing an item into view, ignore any layout passes until we receive a new
+            // effective viewport.
+            if (_isWaitingForViewportUpdate)
+            {
+                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                return CalculateDesiredSize(orientation, items, sizeV);
+            }
+
+            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+            // - Horizontal layouts: U = horizontal, V = vertical
+            // - Vertical layouts: U = vertical, V = horizontal
+            var viewport = CalculateMeasureViewport(items);
+
+            // Recycle elements outside of the expected range.
+            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+
+            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+            // write to _realizedElements yet, only _measureElements.
+            GenerateElements(availableSize, ref viewport);
+
+            // Now we know what definitely fits, recycle anything left over.
+            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+
+            // And swap the measureElements and realizedElements collection.
+            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+            _measureElements.ResetForReuse();
+
+            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            Debug.Assert(_realizedElements is not null);
 
-                    _virtualizationMode = value;
+            var orientation = Orientation;
+            var u = _realizedElements!.StartU;
 
-                    if (_virtualizationMode == ItemVirtualizationMode.Smooth)
-                        EffectiveViewportChanged += OnEffectiveViewportChanged;
+            for (var i = 0; i < _realizedElements.Count; ++i)
+            {
+                var e = _realizedElements.Elements[i];
 
-                    Children.Clear();
+                if (e is object)
+                {
+                    var sizeU = _realizedElements.SizeU[i];
+                    var rect = orientation == Orientation.Horizontal ?
+                        new Rect(u, 0, sizeU, finalSize.Height) :
+                        new Rect(0, u, finalSize.Width, sizeU);
+                    e.Arrange(rect);
+                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
                 }
             }
+
+            return finalSize;
         }
 
-        public static ItemVirtualizationMode GetVirtualizationMode(Control c)
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
         {
-            return c.GetValue(VirtualizationModeProperty);
+            if (_realizedElements is null)
+                return;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    ////RecycleAllElements();
+                    break;
+            }
+
+            InvalidateMeasure();
         }
 
-        public static void SetVirtualizationMode(Control c, ItemVirtualizationMode value)
+        internal IReadOnlyList<Control?> GetRealizedElements()
         {
-            c.SetValue(VirtualizationModeProperty, value);
+            return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        protected override Size MeasureOverride(Size availableSize)
+        private MeasureViewport CalculateMeasureViewport(IList items)
         {
-            return VirtualizationMode switch
+            Debug.Assert(_realizedElements is not null);
+
+            // If the control has not yet been laid out then the effective viewport won't have been set.
+            // Try to work it out from an ancestor control.
+            var viewport = _viewport != s_invalidViewport ? _viewport : EstimateViewport();
+
+            // Get the viewport in the orientation direction.
+            var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
+            var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
+
+            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var estimatedElementSize = -1.0;
+            var itemCount = items?.Count ?? 0;
+
+            if (firstIndex == -1)
+            {
+                estimatedElementSize = EstimateElementSizeU();
+                firstIndex = (int)(viewportStart / estimatedElementSize);
+                firstIndexU = firstIndex * estimatedElementSize;
+            }
+
+            if (lastIndex == -1)
+            {
+                if (estimatedElementSize == -1)
+                    estimatedElementSize = EstimateElementSizeU();
+                lastIndex = (int)(viewportEnd / estimatedElementSize);
+            }
+
+            return new MeasureViewport
             {
-                ItemVirtualizationMode.Smooth => MeasureOverrideSmooth(availableSize),
-                _ => throw new NotImplementedException()
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
+                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                viewportUStart = viewportStart,
+                viewportUEnd = viewportEnd,
+                startU = firstIndexU,
             };
         }
 
-        protected override Size ArrangeOverride(Size finalSize)
+        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
         {
-            return VirtualizationMode switch
-            {
-                ItemVirtualizationMode.Smooth => ArrangeOverrideSmooth(finalSize),
-                _ => throw new NotImplementedException()
-            };
+            var sizeU = EstimateElementSizeU() * items.Count;
+
+            if (double.IsInfinity(sizeU) || double.IsNaN(sizeU))
+                throw new InvalidOperationException("Invalid calculated size.");
+
+            return orientation == Orientation.Horizontal ?
+                new Size(sizeU, sizeV) :
+                new Size(sizeV, sizeU);
         }
 
-        protected override void OnItemsControlChanged(ItemsControl? oldValue)
+        private double EstimateElementSizeU()
         {
-            base.OnItemsControlChanged(oldValue);
-            VirtualizationMode = ItemsControl is null ? ItemVirtualizationMode.None : GetVirtualizationMode(ItemsControl);
+            var count = _realizedElements!.Count;
+            var divisor = 0.0;
+            var total = 0.0;
+
+            for (var i = 0; i < count; ++i)
+            {
+                if (_realizedElements.Elements[i] is object)
+                {
+                    total += _realizedElements.SizeU[i];
+                    ++divisor;
+                }
+            }
+
+            if (divisor == 0 || total == 0)
+                return _lastEstimatedElementSizeU;
+
+            _lastEstimatedElementSizeU = total / divisor;
+            return _lastEstimatedElementSizeU;
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        private Rect EstimateViewport()
         {
-            switch (VirtualizationMode)
+            var c = this.GetVisualParent();
+            var viewport = new Rect();
+
+            if (c is null)
             {
-                case ItemVirtualizationMode.Smooth:
-                    OnItemsChangedSmooth(e);
+                return viewport;
+            }
+
+            while (c is not null)
+            {
+                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                {
+                    viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
+                        .TransformToAABB(transform);
                     break;
+                }
+
+                c = c?.GetVisualParent();
             }
+
+
+            return viewport;
         }
 
-        internal IReadOnlyList<Control?> GetRealizedElements()
+        private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            return VirtualizationMode switch
+            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(_measureElements is not null);
+
+            var items = (IList)ItemsControl!.Items;
+            var horizontal = Orientation == Orientation.Horizontal;
+            var index = viewport.firstIndex;
+            var u = viewport.startU;
+
+            do
             {
-                ItemVirtualizationMode.Smooth => _realizedElements?.Elements ?? Array.Empty<Control>(),
-                _ => Children,
-            };
+                var e = GetOrCreateElement(items, index);
+                e.Measure(availableSize);
+
+                var sizeU = horizontal ? e.DesiredSize.Width : e.DesiredSize.Height;
+                var sizeV = horizontal ? e.DesiredSize.Height : e.DesiredSize.Width;
+
+                _measureElements!.Add(index, e, u, sizeU);
+                viewport.measuredV = Math.Max(viewport.measuredV, sizeV);
+
+                u += sizeU;
+                ++index;
+            } while (u < viewport.viewportUEnd && index < items.Count);
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            InvalidateHack(e);
+            return e;
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            Debug.Assert(_realizedElements is not null);
+
+            if (_anchorIndex == index)
+                return _anchorElement;
+            return _realizedElements!.GetElement(index);
+        }
+
+        private Control GetRecycledOrCreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
+            Children.Add(c);
+            return c;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
+            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
+            Children.Remove(element);
+        }
+
+        private void UpdateElementIndex(Control element, int index)
+        {
+            // TODO: Implement this after we refactor ItemContainerGenerator.
+        }
+
+        private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
+        {
+            _viewport = e.EffectiveViewport;
+            _isWaitingForViewportUpdate = false;
+            InvalidateMeasure();
+        }
+
+        private static void InvalidateHack(Control c)
+        {
+            bool HasInvalidations(Control c)
+            {
+                if (!c.IsMeasureValid)
+                    return true;
+
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                    {
+                        if (!child.IsMeasureValid || HasInvalidations(child))
+                            return true;
+                    }
+                }
+
+                return false;
+            }
+
+            void Invalidate(Control c)
+            {
+                c.InvalidateMeasure();
+                for (var i = 0; i < c.VisualChildren.Count; ++i)
+                {
+                    if (c.VisualChildren[i] is Control child)
+                        Invalidate(child);
+                }
+            }
+
+            if (HasInvalidations(c))
+                Invalidate(c);
         }
 
-        private protected override void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
+        /// <summary>
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// </summary>
+        internal class RealizedElementList
         {
-            base.OnItemsControlPropertyChanged(sender, e);
+            private int _firstIndex;
+            private List<Control?>? _elements;
+            private List<double>? _sizes;
+            private double _startU;
+
+            /// <summary>
+            /// Gets the number of realized elements.
+            /// </summary>
+            public int Count => _elements?.Count ?? 0;
+
+            /// <summary>
+            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+
+            /// <summary>
+            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// </summary>
+            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+
+            /// <summary>
+            /// Gets the elements.
+            /// </summary>
+            public IReadOnlyList<Control?> Elements => _elements ??= new List<Control?>();
+
+            /// <summary>
+            /// Gets the sizes of the elements on the primary axis.
+            /// </summary>
+            public IReadOnlyList<double> SizeU => _sizes ??= new List<double>();
+
+            /// <summary>
+            /// Gets the position of the first element on the primary axis.
+            /// </summary>
+            public double StartU => _startU;
+
+            /// <summary>
+            /// Adds a newly realized element to the collection.
+            /// </summary>
+            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="element">The element.</param>
+            /// <param name="u">The position of the elemnt on the primary axis.</param>
+            /// <param name="sizeU">The size of the element on the primary axis.</param>
+            public void Add(int modelIndex, Control element, double u, double sizeU)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+
+                _elements ??= new List<Control?>();
+                _sizes ??= new List<double>();
 
-            if (e.Property == VirtualizationModeProperty)
+                if (Count == 0)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                    _startU = u;
+                    _firstIndex = modelIndex;
+                }
+                else if (modelIndex == LastModelIndex + 1)
+                {
+                    _elements.Add(element);
+                    _sizes.Add(sizeU);
+                }
+                else if (modelIndex == FirstModelIndex - 1)
+                {
+                    --_firstIndex;
+                    _elements.Insert(0, element);
+                    _sizes.Insert(0, sizeU);
+                    _startU = u;
+                }
+                else
+                {
+                    throw new NotSupportedException("Can only add items to the beginning or end of realized elements.");
+                }
+            }
+
+            /// <summary>
+            /// Gets the element at the specified model index, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <returns>The element if realized; otherwise null.</returns>
+            public Control? GetElement(int modelIndex)
             {
-                VirtualizationMode = e.GetNewValue<ItemVirtualizationMode>();
+                var index = modelIndex - FirstModelIndex;
+                if (index >= 0 && index < _elements?.Count)
+                    return _elements[index];
+                return null;
             }
+
+            /// <summary>
+            /// Gets the element at the specified position on the primary axis, if realized.
+            /// </summary>
+            /// <param name="position">The position.</param>
+            /// <returns>
+            /// A tuple containing the index of the element (or -1 if not found) and the position of the element on the
+            /// primary axis.
+            /// </returns>
+            public (int index, double position) GetElementAt(double position)
+            {
+                if (_sizes is null || position < StartU)
+                    return (-1, 0);
+
+                var u = StartU;
+                var i = FirstModelIndex;
+
+                foreach (var size in _sizes)
+                {
+                    var endU = u + size;
+                    if (position < endU)
+                        return (i, u);
+                    u += size;
+                    ++i;
+                }
+
+                return (-1, 0);
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being inserted into the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="count">The number of items inserted.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var index = modelIndex - first;
+
+                if (index < Count)
+                {
+                    // The insertion point affects the realized elements. Update the index of the
+                    // elements after the insertion point.
+                    var elementCount = _elements.Count;
+                    var start = Math.Max(index, 0);
+
+                    for (var i = start; i < elementCount; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i + count);
+                    }
+
+                    if (index <= 0)
+                    {
+                        // The insertion point was before the first element, update the first index.
+                        _firstIndex += count;
+                    }
+                    else
+                    {
+                        // The insertion point was within the realized elements, insert an empty space
+                        // in _elements and _sizes.
+                        _elements!.InsertMany(index, null, count);
+                        _sizes!.InsertMany(index, 0.0, count);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Updates the elements in response to items being removed from the source collection.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="count">The number of items removed.</param>
+            /// <param name="updateElementIndex">A method used to update the element indexes.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsRemoved(
+                int modelIndex,
+                int count,
+                Action<Control, int> updateElementIndex,
+                Action<Control> recycleElement)
+            {
+                if (modelIndex < 0)
+                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                // Get the removal start and end index within the realized _elements collection.
+                var first = FirstModelIndex;
+                var last = LastModelIndex;
+                var startIndex = modelIndex - first;
+                var endIndex = (modelIndex + count) - first;
+
+                if (endIndex < 0)
+                {
+                    // The removed range was before the realized elements. Update the first index and
+                    // the indexes of the realized elements.
+                    _firstIndex -= count;
+
+                    for (var i = 0; i < _elements.Count; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, _firstIndex + i);
+                    }
+                }
+                else if (startIndex < _elements.Count)
+                {
+                    // Recycle and remove the affected elements.
+                    var start = Math.Max(startIndex, 0);
+                    var end = Math.Min(endIndex, _elements.Count);
+
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            recycleElement(element);
+                    }
+
+                    _elements.RemoveRange(start, end - start);
+                    _sizes!.RemoveRange(start, end - start);
+
+                    // If the remove started before and ended within our realized elements, then our new
+                    // first index will be the index where the remove started.
+                    if (startIndex <= 0 && end < last)
+                        _firstIndex = first = modelIndex;
+
+                    // Update the indexes of the elements after the removed range.
+                    end = _elements.Count;
+                    for (var i = start; i < end; ++i)
+                    {
+                        if (_elements[i] is Control element)
+                            updateElementIndex(element, first + i);
+                    }
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements before a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex > LastModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var endIndex = modelIndex - FirstModelIndex;
+
+                    for (var i = 0; i < endIndex; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(0, endIndex);
+                    _sizes!.RemoveRange(0, endIndex);
+                    _firstIndex = modelIndex;
+                }
+            }
+
+            /// <summary>
+            /// Recycles elements after a specific index.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            {
+                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                    return;
+
+                if (modelIndex < FirstModelIndex)
+                {
+                    RecycleAllElements(recycleElement);
+                }
+                else
+                {
+                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var count = _elements.Count;
+
+                    for (var i = startIndex; i < count; ++i)
+                    {
+                        if (_elements[i] is Control e)
+                            recycleElement(e);
+                    }
+
+                    _elements.RemoveRange(startIndex, _elements.Count - startIndex);
+                    _sizes!.RemoveRange(startIndex, _sizes.Count - startIndex);
+                }
+            }
+
+            /// <summary>
+            /// Recycles all realized elements.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void RecycleAllElements(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is object)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+
+            /// <summary>
+            /// Resets the element list and prepares it for reuse.
+            /// </summary>
+            public void ResetForReuse()
+            {
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+            }
+        }
+
+        private struct MeasureViewport
+        {
+            public int firstIndex;
+            public int estimatedLastIndex;
+            public double viewportUStart;
+            public double viewportUEnd;
+            public double measuredV;
+            public double startU;
         }
     }
 }
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml b/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
index c0ba508179..3bef23a160 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/ConsoleView.xaml
@@ -40,8 +40,7 @@
              BorderBrush="{DynamicResource ThemeControlMidBrush}"
              BorderThickness="0,0,0,1"
              FontFamily="/Assets/Fonts/SourceSansPro-Regular.ttf"
-             Items="{Binding History}"
-             VirtualizationMode="None">
+             Items="{Binding History}">
       <ListBox.ItemTemplate>
         <DataTemplate>
           <StackPanel Orientation="Vertical">
diff --git a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
index cdfca65ff6..9a8f41ac8a 100644
--- a/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/ManagedFileChooser.xaml
@@ -216,7 +216,6 @@
               <TextBlock Grid.Column="8" Text="Size" />
             </Grid>
             <ListBox x:Name="PART_Files"
-                VirtualizationMode="Simple"
                 Items="{Binding Items}"
                 Margin="0 5"
                 SelectionMode="{Binding SelectionMode}"
diff --git a/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml b/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
index 61dae9b445..5514aa4593 100644
--- a/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/ManagedFileChooser.xaml
@@ -149,8 +149,7 @@
                      Items="{Binding Items}"
                      ScrollViewer.HorizontalScrollBarVisibility="Disabled"
                      SelectedItems="{Binding SelectedItems}"
-                     SelectionMode="{Binding SelectionMode}"
-                     VirtualizationMode="Simple">
+                     SelectionMode="{Binding SelectionMode}">
               <ListBox.ItemTemplate>
                 <DataTemplate>
                   <Grid Background="Transparent">
diff --git a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
index 6eaef4c849..e206d809d3 100644
--- a/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ComboBoxTests.cs
@@ -285,7 +285,6 @@ namespace Avalonia.Controls.UnitTests
                 var target = new ComboBox
                 {
                     Template = GetTemplate(),
-                    VirtualizationMode =  ItemVirtualizationMode.None
                 };
 
                 target.ApplyTemplate();
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index b6375278b1..280f140a79 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -369,7 +369,6 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void LayoutManager_Should_Measure_Arrange_All()
         {
-            var virtualizationMode = ItemVirtualizationMode.Simple;
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
                 var items = new AvaloniaList<string>(Enumerable.Range(1, 7).Select(v => v.ToString()));
@@ -387,7 +386,6 @@ namespace Avalonia.Controls.UnitTests
                 target.Height = 110;
                 target.Width = 50;
                 target.DataContext = items;
-                target.VirtualizationMode = virtualizationMode;
 
                 target.ItemTemplate = new FuncDataTemplate<object>((c, _) =>
                 {
@@ -448,7 +446,6 @@ namespace Avalonia.Controls.UnitTests
                     AutoScrollToSelectedItem = true,
                     Height = 100,
                     Width = 50,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
                     Items = items,
                 };
@@ -488,7 +485,6 @@ namespace Avalonia.Controls.UnitTests
                     Items = items,
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
                     SelectionMode = SelectionMode.AlwaysSelected,
-                    VirtualizationMode = ItemVirtualizationMode.None,
                 };
 
                 Prepare(target);
@@ -532,7 +528,6 @@ namespace Avalonia.Controls.UnitTests
                     VerticalAlignment = Layout.VerticalAlignment.Top,
                     AutoScrollToSelectedItem = true,
                     Width = 50,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
                     Items = items,
                 };
@@ -705,7 +700,6 @@ namespace Avalonia.Controls.UnitTests
                 Items = new[] { "Foo" },
                 ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
                 SelectionMode = SelectionMode.AlwaysSelected,
-                VirtualizationMode = ItemVirtualizationMode.None
             };
 
             Prepare(target);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 2c57c20b6c..d89e88b2ba 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -1475,7 +1475,6 @@ namespace Avalonia.Controls.UnitTests.Primitives
                             Height = 10
                         }),
                     AutoScrollToSelectedItem = true,
-                    VirtualizationMode = ItemVirtualizationMode.Simple,
                 };
 
                 var root = new TestRoot(true, target);
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
index 7f7a956f2c..54b76b1931 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
@@ -161,7 +161,6 @@ namespace Avalonia.Controls.UnitTests
                 Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
                 ItemsPanel = new FuncTemplate<Panel>(() => target),
                 ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
-                [VirtualizingStackPanel.VirtualizationModeProperty] = ItemVirtualizationMode.Smooth,
             };
 
             var root = new TestRoot(true, itemsControl);
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index ae8df6168d..9170c68e11 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -836,7 +836,6 @@ namespace Avalonia.LeakTests
                     {
                         Width = 100,
                         Height = 100,
-                        VirtualizationMode = ItemVirtualizationMode.None,
                         // Create a button with binding to the KeyGesture in the template and add it to references list
                         ItemTemplate = new FuncDataTemplate(typeof(KeyGesture), (o, scope) =>
                         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 70a5295008..6361dcdbea 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -372,7 +372,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 };
 
                 var list = window.FindControl<ListBox>("list");
-                list.VirtualizationMode = ItemVirtualizationMode.Simple;
                 list.Items = collection;
 
                 window.Show();

From 1101f28dd7a6460764873b6cc2e9ce4da293eb61 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 28 Nov 2022 18:53:03 +0100
Subject: [PATCH 009/157] Refactored ItemContainerGenerator.

A bunch of tests still failing, and some code commented out, but outlines the new API shape.
---
 src/Avalonia.Controls/ComboBox.cs             |   26 +-
 src/Avalonia.Controls/ContextMenu.cs          |    5 -
 .../Flyouts/MenuFlyoutPresenter.cs            |    5 -
 .../Generators/IItemContainerGenerator.cs     |  114 -
 .../Generators/ITreeItemContainerGenerator.cs |   18 -
 .../Generators/ItemContainerEventArgs.cs      |   49 -
 .../Generators/ItemContainerGenerator.cs      |  284 +-
 .../Generators/ItemContainerGenerator`1.cs    |  102 -
 .../Generators/ItemContainerInfo.cs           |   42 -
 .../Generators/MenuItemContainerGenerator.cs  |   21 -
 .../Generators/TabItemContainerGenerator.cs   |  105 -
 .../Generators/TreeContainerIndex.cs          |  166 -
 .../Generators/TreeItemContainerGenerator.cs  |  164 -
 src/Avalonia.Controls/ItemsControl.cs         |  205 +-
 src/Avalonia.Controls/ListBox.cs              |    9 +-
 src/Avalonia.Controls/MenuBase.cs             |   13 +-
 src/Avalonia.Controls/MenuItem.cs             |   13 +-
 .../Presenters/ItemsPresenter.cs              |   23 +-
 ...enerator.cs => PanelContainerGenerator.cs} |   57 +-
 .../Primitives/SelectingItemsControl.cs       |  138 +-
 src/Avalonia.Controls/Primitives/TabStrip.cs  |    8 -
 src/Avalonia.Controls/TabControl.cs           |   13 +-
 src/Avalonia.Controls/TreeView.cs             |  440 ++-
 src/Avalonia.Controls/TreeViewItem.cs         |   35 -
 src/Avalonia.Controls/VirtualizingPanel.cs    |  101 +-
 .../VirtualizingStackPanel.cs                 |  290 +-
 .../Diagnostics/Views/TreePageView.xaml.cs    |   12 +-
 .../CarouselTests.cs                          |  658 ++--
 .../Generators/ItemContainerGeneratorTests.cs |  173 -
 .../ItemContainerGeneratorTypedTests.cs       |   42 -
 .../ItemsControlTests.cs                      |   65 +-
 .../ListBoxTests.cs                           |  119 +-
 .../TreeViewTests.cs                          | 2900 ++++++++---------
 tests/Avalonia.LeakTests/ControlTests.cs      |   27 +-
 34 files changed, 2670 insertions(+), 3772 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
 delete mode 100644 src/Avalonia.Controls/Generators/ItemContainerInfo.cs
 delete mode 100644 src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TreeContainerIndex.cs
 delete mode 100644 src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
 rename src/Avalonia.Controls/Presenters/{ItemsPresenterContainerGenerator.cs => PanelContainerGenerator.cs} (66%)
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index 41c17bd3e1..e6af255c29 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -158,15 +158,6 @@ namespace Avalonia.Controls
             set { SetValue(VerticalContentAlignmentProperty, value); }
         }
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<ComboBoxItem>(
-                this,
-                ComboBoxItem.ContentProperty,
-                ComboBoxItem.ContentTemplateProperty);
-        }
-
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnAttachedToVisualTree(e);
@@ -449,14 +440,15 @@ namespace Avalonia.Controls
 
         private void SelectFocusedItem()
         {
-            foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
-            {
-                if (dropdownItem.ContainerControl.IsFocused)
-                {
-                    SelectedIndex = dropdownItem.Index;
-                    break;
-                }
-            }
+            throw new NotImplementedException();
+            ////foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
+            ////{
+            ////    if (dropdownItem.ContainerControl.IsFocused)
+            ////    {
+            ////        SelectedIndex = dropdownItem.Index;
+            ////        break;
+            ////    }
+            ////}
         }
 
         private void SelectNext()
diff --git a/src/Avalonia.Controls/ContextMenu.cs b/src/Avalonia.Controls/ContextMenu.cs
index 020a6de539..c0b1297b6d 100644
--- a/src/Avalonia.Controls/ContextMenu.cs
+++ b/src/Avalonia.Controls/ContextMenu.cs
@@ -315,11 +315,6 @@ namespace Avalonia.Controls
             remove => _popupHostChangedHandler -= value;
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         private void Open(Control control, Control placementTarget, bool requestedByPointer)
         {
             if (IsOpen)
diff --git a/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
index 278e498a67..7aca21b42e 100644
--- a/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
+++ b/src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs
@@ -35,11 +35,6 @@ namespace Avalonia.Controls
             throw new NotSupportedException("Use MenuFlyout.ShowAt(Control) instead");
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromVisualTree(e);
diff --git a/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
deleted file mode 100644
index 8f0e3c88c1..0000000000
--- a/src/Avalonia.Controls/Generators/IItemContainerGenerator.cs
+++ /dev/null
@@ -1,114 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
-    /// </summary>
-    public interface IItemContainerGenerator
-    {
-        /// <summary>
-        /// Gets the currently realized containers.
-        /// </summary>
-        IEnumerable<ItemContainerInfo> Containers { get; }
-
-        /// <summary>
-        /// Gets or sets the theme to be applied to the items in the control.
-        /// </summary>
-        ControlTheme? ItemContainerTheme { get; set; }
-
-        /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
-        /// </summary>
-        IDataTemplate? ItemTemplate { get; set; }
-        
-        /// <summary>
-        /// Gets or sets the binding to use to bind to the member of an item used for displaying
-        /// </summary>
-        IBinding? DisplayMemberBinding { get; set; }
-
-        /// <summary>
-        /// Gets the ContainerType, or null if its an untyped ContainerGenerator.
-        /// </summary>
-        Type? ContainerType { get; }
-
-        /// <summary>
-        /// Signaled whenever new containers are materialized.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <summary>
-        /// Event raised whenever containers are dematerialized.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <summary>
-        /// Event raised whenever containers are recycled.
-        /// </summary>
-        event EventHandler<ItemContainerEventArgs>? Recycled;
-
-        /// <summary>
-        /// Creates a container control for an item.
-        /// </summary>
-        /// <param name="index">
-        /// The index of the item of data in the control's items.
-        /// </param>
-        /// <param name="item">The item.</param>
-        /// <returns>The created controls.</returns>
-        ItemContainerInfo Materialize(int index, object item);
-
-        /// <summary>
-        /// Removes a set of created containers.
-        /// </summary>
-        /// <param name="startingIndex">
-        /// The index of the first item in the control's items.
-        /// </param>
-        /// <param name="count">The the number of items to remove.</param>
-        /// <returns>The removed containers.</returns>
-        IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count);
-
-        /// <summary>
-        /// Inserts space for newly inserted containers in the index.
-        /// </summary>
-        /// <param name="index">The index at which space should be inserted.</param>
-        /// <param name="count">The number of blank spaces to create.</param>
-        void InsertSpace(int index, int count);
-
-        /// <summary>
-        /// Removes a set of created containers and updates the index of later containers to fill
-        /// the gap.
-        /// </summary>
-        /// <param name="startingIndex">
-        /// The index of the first item in the control's items.
-        /// </param>
-        /// <param name="count">The the number of items to remove.</param>
-        /// <returns>The removed containers.</returns>
-        IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count);
-
-        bool TryRecycle(int oldIndex, int newIndex, object item);
-
-        /// <summary>
-        /// Clears all created containers and returns the removed controls.
-        /// </summary>
-        /// <returns>The removed controls.</returns>
-        IEnumerable<ItemContainerInfo> Clear();
-
-        /// <summary>
-        /// Gets the container control representing the item with the specified index.
-        /// </summary>
-        /// <param name="index">The index.</param>
-        /// <returns>The container, or null if no container created.</returns>
-        Control? ContainerFromIndex(int index);
-
-        /// <summary>
-        /// Gets the index of the specified container control.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        /// <returns>The index of the container, or -1 if not found.</returns>
-        int IndexFromContainer(Control? container);
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
deleted file mode 100644
index f15987fe79..0000000000
--- a/src/Avalonia.Controls/Generators/ITreeItemContainerGenerator.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for tree items and maintains a list of created containers.
-    /// </summary>
-    public interface ITreeItemContainerGenerator : IItemContainerGenerator
-    {
-        /// <summary>
-        /// Gets the container index for the tree.
-        /// </summary>
-        TreeContainerIndex? Index { get; }
-
-        /// <summary>
-        /// Updates the index based on the parent <see cref="TreeView"/>.
-        /// </summary>
-        void UpdateIndex();
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs b/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
deleted file mode 100644
index f65018531e..0000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerEventArgs.cs
+++ /dev/null
@@ -1,49 +0,0 @@
-using System;
-using System.Collections.Generic;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Provides details for the <see cref="IItemContainerGenerator.Materialized"/>
-    /// and <see cref="IItemContainerGenerator.Dematerialized"/> events.
-    /// </summary>
-    public class ItemContainerEventArgs : EventArgs
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerEventArgs"/> class.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        public ItemContainerEventArgs(ItemContainerInfo container)
-        {
-            StartingIndex = container.Index;
-            Containers = new[] { container };
-        }
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerEventArgs"/> class.
-        /// </summary>
-        /// <param name="startingIndex">The index of the first container in the source items.</param>
-        /// <param name="containers">The containers.</param>
-        /// <remarks>
-        /// TODO: Do we really need to pass in StartingIndex here? The ItemContainerInfo objects
-        /// have an index, and what happens if the contains passed in aren't sequential?
-        /// </remarks>
-        public ItemContainerEventArgs(
-            int startingIndex, 
-            IList<ItemContainerInfo> containers)
-        {
-            StartingIndex = startingIndex;
-            Containers = containers;
-        }
-
-        /// <summary>
-        /// Gets the containers.
-        /// </summary>
-        public IList<ItemContainerInfo> Containers { get; }
-
-        /// <summary>
-        /// Gets the index of the first container in the source items.
-        /// </summary>
-        public int StartingIndex { get; }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index d87422e57e..0598bb1a63 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -1,262 +1,68 @@
 using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Styling;
 
 namespace Avalonia.Controls.Generators
 {
     /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
+    /// Generates containers for an <see cref="ItemsControl"/>.
     /// </summary>
-    public class ItemContainerGenerator : IItemContainerGenerator
+    /// <remarks>
+    /// Although this class is similar to that found in WPF/UWP, in Avalonia this class only
+    /// concerns itself with generating and clearing item containers; it does not maintain a
+    /// record of the currently realized containers, that responsibility is delegated to the
+    /// items panel.
+    /// </remarks>
+    public class ItemContainerGenerator
     {
-        private SortedDictionary<int, ItemContainerInfo> _containers = new SortedDictionary<int, ItemContainerInfo>();
+        private ItemsControl _owner;
 
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        public ItemContainerGenerator(Control owner)
-        {
-            Owner = owner ?? throw new ArgumentNullException(nameof(owner));
-        }
-
-        /// <inheritdoc/>
-        public IEnumerable<ItemContainerInfo> Containers => _containers.Values;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <inheritdoc/>
-        public event EventHandler<ItemContainerEventArgs>? Recycled;
+        internal ItemContainerGenerator(ItemsControl owner) => _owner = owner;
 
         /// <summary>
-        /// Gets or sets the theme to be applied to the items in the control.
+        /// Creates a new container control.
         /// </summary>
-        public ControlTheme? ItemContainerTheme { get; set; }
+        /// <returns>The newly created container control.</returns>
+        /// <remarks>
+        /// Before calling this method, <see cref="IsItemItsOwnContainer(Control)"/> should be
+        /// called to determine whether the item itself should be used as a container. After
+        /// calling this method, <see cref="PrepareItemContainer(Control, object, int)"/> should
+        /// be called to prepare the container to display the specified item.
+        /// </remarks>
+        public Control CreateContainer() => _owner.CreateContainerOverride();
 
         /// <summary>
-        /// Gets or sets the data template used to display the items in the control.
+        /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
-        public IDataTemplate? ItemTemplate { get; set; }
-        
-        /// <inheritdoc />
-        public IBinding? DisplayMemberBinding { get; set; }
+        /// <param name="container">The item.</param>
+        /// <returns>true if the item is its own container, otherwise false.</returns>
+        /// <remarks>
+        /// Whereas in WPF/UWP, non-control items can be their own container, in Avalonia only
+        /// control items may be; the caller is responsible for checking if each item is a control
+        /// and calling this method before creating a new container.
+        /// </remarks>
+        public bool IsItemItsOwnContainer(Control container) => _owner.IsItemItsOwnContainerOverride(container);
 
         /// <summary>
-        /// Gets the owner control.
+        /// Prepares the specified element as the container for the corresponding item.
         /// </summary>
-        public Control Owner { get; }
-
-        /// <inheritdoc/>
-        public virtual Type? ContainerType => null;
-
-        /// <inheritdoc/>
-        public ItemContainerInfo Materialize(int index, object item)
-        {
-            var container = new ItemContainerInfo(CreateContainer(item)!, item, index);
-
-            _containers.Add(container.Index, container);
-            Materialized?.Invoke(this, new ItemContainerEventArgs(container));
-
-            return container;
-        }
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            for (int i = startingIndex; i < startingIndex + count; ++i)
-            {
-                result.Add(_containers[i]);
-                _containers.Remove(i);
-            }
-
-            Dematerialized?.Invoke(this, new ItemContainerEventArgs(startingIndex, result));
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public virtual void InsertSpace(int index, int count)
-        {
-            if (count > 0)
-            {
-                var toMove = _containers.Where(x => x.Key >= index)
-                    .OrderByDescending(x => x.Key)
-                    .ToArray();
-
-                foreach (var i in toMove)
-                {
-                    _containers.Remove(i.Key);
-                    i.Value.Index += count;
-                    _containers.Add(i.Value.Index, i.Value);
-                }
-            }
-        }
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            if (count > 0)
-            {
-                for (var i = startingIndex; i < startingIndex + count; ++i)
-                {
-                    if (_containers.TryGetValue(i, out var found))
-                    {
-                        result.Add(found);
-                    }
-
-                    _containers.Remove(i);
-                }
-
-                var toMove = _containers.Where(x => x.Key >= startingIndex)
-                                        .OrderBy(x => x.Key).ToArray();
-
-                foreach (var i in toMove)
-                {
-                    _containers.Remove(i.Key);
-                    i.Value.Index -= count;
-                    _containers.Add(i.Value.Index, i.Value);
-                }
-
-                Dematerialized?.Invoke(this, new ItemContainerEventArgs(startingIndex, result));
-
-                if (toMove.Length > 0)
-                {
-                    var containers = toMove.Select(x => x.Value).ToArray();
-                    Recycled?.Invoke(this, new ItemContainerEventArgs(containers[0].Index, containers));
-                }
-            }
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public virtual bool TryRecycle(int oldIndex, int newIndex, object item) => false;
-
-        /// <inheritdoc/>
-        public virtual IEnumerable<ItemContainerInfo> Clear()
-        {
-            var result = Containers.ToArray();
-            _containers.Clear();
-
-            if (result.Length > 0)
-            {
-                Dematerialized?.Invoke(this, new ItemContainerEventArgs(0, result));
-            }
-
-            return result;
-        }
-
-        /// <inheritdoc/>
-        public Control? ContainerFromIndex(int index)
-        {
-            ItemContainerInfo? result;
-            _containers.TryGetValue(index, out result);
-            return result?.ContainerControl;
-        }
-
-        /// <inheritdoc/>
-        public int IndexFromContainer(Control? container)
-        {
-            foreach (var i in _containers)
-            {
-                if (i.Value.ContainerControl == container)
-                {
-                    return i.Key;
-                }
-            }
-
-            return -1;
-        }
+        /// <param name="container">The element that's used to display the specified item.</param>
+        /// <param name="item">The item to display.</param>
+        /// <param name="index">The index of the item to display.</param>
+        /// <remarks>
+        /// If <see cref="IsItemItsOwnContainer(Control)"/> is true for an item, then this method
+        /// only needs to be called a single time, otherwise this method should be called after the
+        /// container is created, and each subsequent time the container is recycled to display a
+        /// new item.
+        /// </remarks>
+        public void PrepareItemContainer(Control container, object? item, int index) => 
+            _owner.PrepareItemContainer(container, item, index);
 
         /// <summary>
-        /// Creates the container for an item.
+        /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
-        /// <param name="item">The item.</param>
-        /// <returns>The created container control.</returns>
-        protected virtual Control? CreateContainer(object item)
-        {
-            var result = item as Control;
-
-            if (result == null)
-            {
-                result = new ContentPresenter();
-                if (DisplayMemberBinding is not null)
-                {
-                    result.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    result.Bind(ContentPresenter.ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    result.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Style);
-                }
-
-                if (ItemTemplate != null)
-                {
-                    result.SetValue(
-                        ContentPresenter.ContentTemplateProperty,
-                        ItemTemplate,
-                        BindingPriority.Style);
-                }
-            }
+        /// <param name="container">The element that's used to display the specified item.</param>
+        public void ClearItemContainer(Control container) => _owner.ClearContainerForItemOverride(container);
 
-            if (ItemContainerTheme != null)
-            {
-                result.SetValue(
-                    StyledElement.ThemeProperty,
-                    ItemContainerTheme,
-                    BindingPriority.Template);
-            }
-
-            return result;
-        }
-
-        /// <summary>
-        /// Moves a container.
-        /// </summary>
-        /// <param name="oldIndex">The old index.</param>
-        /// <param name="newIndex">The new index.</param>
-        /// <param name="item">The new item.</param>
-        /// <returns>The container info.</returns>
-        protected ItemContainerInfo MoveContainer(int oldIndex, int newIndex, object item)
-        {
-            var container = _containers[oldIndex];
-            container.Index = newIndex;
-            container.Item = item;
-            _containers.Remove(oldIndex);
-            _containers.Add(newIndex, container);
-            return container;
-        }
-
-        /// <summary>
-        /// Gets all containers with an index that fall within a range.
-        /// </summary>
-        /// <param name="index">The first index.</param>
-        /// <param name="count">The number of elements in the range.</param>
-        /// <returns>The containers.</returns>
-        protected IEnumerable<ItemContainerInfo> GetContainerRange(int index, int count)
-        {
-            return _containers.Where(x => x.Key >= index && x.Key < index + count).Select(x => x.Value);
-        }
-
-        /// <summary>
-        /// Raises the <see cref="Recycled"/> event.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        protected void RaiseRecycled(ItemContainerEventArgs e)
-        {
-            Recycled?.Invoke(this, e);
-        }
+        public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
+        public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
     }
 }
diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
deleted file mode 100644
index ad5bf0219c..0000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator`1.cs
+++ /dev/null
@@ -1,102 +0,0 @@
-using System;
-using Avalonia.Data;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for items and maintains a list of created containers.
-    /// </summary>
-    /// <typeparam name="T">The type of the container.</typeparam>
-    public class ItemContainerGenerator<T> : ItemContainerGenerator where T : Control, new()
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        /// <param name="contentProperty">The container's Content property.</param>
-        /// <param name="contentTemplateProperty">The container's ContentTemplate property.</param>
-        public ItemContainerGenerator(
-            Control owner,
-            AvaloniaProperty contentProperty,
-            AvaloniaProperty? contentTemplateProperty)
-            : base(owner)
-        {
-            ContentProperty = contentProperty ?? throw new ArgumentNullException(nameof(contentProperty));
-            ContentTemplateProperty = contentTemplateProperty;
-        }
-
-        /// <inheritdoc/>
-        public override Type ContainerType => typeof(T);
-
-        /// <summary>
-        /// Gets the container's Content property.
-        /// </summary>
-        protected AvaloniaProperty ContentProperty { get; }
-
-        /// <summary>
-        /// Gets the container's ContentTemplate property.
-        /// </summary>
-        protected AvaloniaProperty? ContentTemplateProperty { get; }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object item)
-        {
-            var container = item as T;
-
-            if (container is null)
-            {
-                container = new T();
-
-                if (ContentTemplateProperty != null)
-                {
-                    container.SetValue(ContentTemplateProperty, ItemTemplate, BindingPriority.Style);
-                }
-
-                if (DisplayMemberBinding is not null)
-                {
-                    container.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    container.Bind(ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    container.SetValue(ContentProperty, item, BindingPriority.Style);
-                }
-                
-                if (!(item is Control))
-                {
-                    container.DataContext = item;
-                }
-            }
-
-            if (ItemContainerTheme != null)
-            {
-                container.SetValue(StyledElement.ThemeProperty, ItemContainerTheme, BindingPriority.Style);
-            }
-
-            return container;
-        }
-
-        /// <inheritdoc/>
-        public override bool TryRecycle(int oldIndex, int newIndex, object item)
-        {
-            var container = ContainerFromIndex(oldIndex);
-
-            if (container == null)
-            {
-                throw new IndexOutOfRangeException("Could not recycle container: not materialized.");
-            }
-
-            container.SetValue(ContentProperty, item);
-
-            if (!(item is Control))
-            {
-                container.DataContext = item;
-            }
-
-            var info = MoveContainer(oldIndex, newIndex, item);
-            RaiseRecycled(new ItemContainerEventArgs(info));
-
-            return true;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/ItemContainerInfo.cs b/src/Avalonia.Controls/Generators/ItemContainerInfo.cs
deleted file mode 100644
index 047e457e7c..0000000000
--- a/src/Avalonia.Controls/Generators/ItemContainerInfo.cs
+++ /dev/null
@@ -1,42 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Holds information about an item container generated by an 
-    /// <see cref="IItemContainerGenerator"/>.
-    /// </summary>
-    public class ItemContainerInfo
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerInfo"/> class.
-        /// </summary>
-        /// <param name="container">The container control.</param>
-        /// <param name="item">The item that the container represents.</param>
-        /// <param name="index">
-        /// The index of the item in the <see cref="ItemsControl.Items"/> collection.
-        /// </param>
-        public ItemContainerInfo(Control container, object item, int index)
-        {
-            ContainerControl = container;
-            Item = item;
-            Index = index;
-        }
-
-        /// <summary>
-        /// Gets the container control.
-        /// </summary>
-        /// <remarks>
-        /// This will be null if <see cref="Item"/> is null.
-        /// </remarks>
-        public Control ContainerControl { get; }
-
-        /// <summary>
-        /// Gets the item that the container represents.
-        /// </summary>
-        public object Item { get; internal set; }
-
-        /// <summary>
-        /// Gets the index of the item in the <see cref="ItemsControl.Items"/> collection.
-        /// </summary>
-        public int Index { get; set; }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
deleted file mode 100644
index 0dcb6c05e1..0000000000
--- a/src/Avalonia.Controls/Generators/MenuItemContainerGenerator.cs
+++ /dev/null
@@ -1,21 +0,0 @@
-namespace Avalonia.Controls.Generators
-{
-    public class MenuItemContainerGenerator : ItemContainerGenerator<MenuItem>
-    {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="ItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        public MenuItemContainerGenerator(Control owner)
-            : base(owner, MenuItem.HeaderProperty, null)
-        {
-        }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object item)
-        {
-            var separator = item as Separator;
-            return separator != null ? separator : base.CreateContainer(item);
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
deleted file mode 100644
index b26b113fbb..0000000000
--- a/src/Avalonia.Controls/Generators/TabItemContainerGenerator.cs
+++ /dev/null
@@ -1,105 +0,0 @@
-using System;
-using System.Collections.Generic;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.Reactive;
-using Avalonia.VisualTree;
-
-namespace Avalonia.Controls.Generators
-{    
-    public class TabItemContainerGenerator : ItemContainerGenerator<TabItem>
-    {
-        public TabItemContainerGenerator(TabControl owner)
-            : base(owner, ContentControl.ContentProperty, ContentControl.ContentTemplateProperty)
-        {
-            Owner = owner;
-        }
-
-        public new TabControl Owner { get; }
-
-        protected override Control CreateContainer(object item)
-        {
-            var tabItem = (TabItem)base.CreateContainer(item)!;
-
-            tabItem.Bind(TabItem.TabStripPlacementProperty, new OwnerBinding<Dock>(
-                tabItem,
-                TabControl.TabStripPlacementProperty));
-
-            if (tabItem.HeaderTemplate == null)
-            {
-                tabItem.Bind(TabItem.HeaderTemplateProperty, new OwnerBinding<IDataTemplate?>(
-                    tabItem,
-                    TabControl.ItemTemplateProperty));
-            }
-
-            if (Owner.HeaderDisplayMemberBinding is not null)
-            {
-                tabItem.Bind(HeaderedContentControl.HeaderProperty, Owner.HeaderDisplayMemberBinding,
-                    BindingPriority.Style);
-            }
-
-            if (tabItem.Header == null)
-            {
-                if (item is IHeadered headered)
-                {
-                    tabItem.Header = headered.Header;
-                }
-                else
-                {
-                    if (!(tabItem.DataContext is Control))
-                    {
-                        tabItem.Header = tabItem.DataContext;
-                    }
-                }
-            }
-
-            if (!(tabItem.Content is Control))
-            {
-                tabItem.Bind(TabItem.ContentTemplateProperty, new OwnerBinding<IDataTemplate?>(
-                    tabItem,
-                    TabControl.ContentTemplateProperty));
-            }
-
-            return tabItem;
-        }
-
-        private class OwnerBinding<T> : SingleSubscriberObservableBase<T>
-        {
-            private readonly TabItem _item;
-            private readonly StyledProperty<T> _ownerProperty;
-            private IDisposable? _ownerSubscription;
-            private IDisposable? _propertySubscription;
-
-            public OwnerBinding(TabItem item, StyledProperty<T> ownerProperty)
-            {
-                _item = item;
-                _ownerProperty = ownerProperty;
-            }
-
-            protected override void Subscribed()
-            {
-                _ownerSubscription = ControlLocator.Track(_item, 0, typeof(TabControl)).Subscribe(OwnerChanged);
-            }
-
-            protected override void Unsubscribed()
-            {
-                _ownerSubscription?.Dispose();
-                _ownerSubscription = null;
-            }
-
-            private void OwnerChanged(ILogical? c)
-            {
-                _propertySubscription?.Dispose();
-                _propertySubscription = null;
-
-                if (c is TabControl tabControl)
-                {
-                    _propertySubscription = tabControl.GetObservable(_ownerProperty)
-                        .Subscribe(x => PublishNext(x));
-                }
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TreeContainerIndex.cs b/src/Avalonia.Controls/Generators/TreeContainerIndex.cs
deleted file mode 100644
index 02b8e7003e..0000000000
--- a/src/Avalonia.Controls/Generators/TreeContainerIndex.cs
+++ /dev/null
@@ -1,166 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Maintains an index of all item containers currently materialized by a <see cref="TreeView"/>.
-    /// </summary>
-    /// <remarks>
-    /// Each <see cref="TreeViewItem"/> has its own <see cref="TreeItemContainerGenerator{T}"/> 
-    /// that maintains the list of its direct children, but they also share an instance of this
-    /// class in their <see cref="TreeItemContainerGenerator{T}.Index"/> property which tracks 
-    /// the containers materialized for the entire tree.
-    /// </remarks>
-    public class TreeContainerIndex
-    {
-        private readonly Dictionary<object, HashSet<Control>> _itemToContainerSet = new Dictionary<object, HashSet<Control>>();
-        private readonly Dictionary<object, Control> _itemToContainer = new Dictionary<object, Control>();
-        private readonly Dictionary<Control, object> _containerToItem = new Dictionary<Control, object>();
-
-        /// <summary>
-        /// Signaled whenever new containers are materialized.
-        /// </summary>
-        public event EventHandler<ItemContainerEventArgs>? Materialized;
-
-        /// <summary>
-        /// Event raised whenever containers are dematerialized.
-        /// </summary>
-        public event EventHandler<ItemContainerEventArgs>? Dematerialized;
-
-        /// <summary>
-        /// Gets the currently materialized containers.
-        /// </summary>
-        public IEnumerable<Control> Containers => _containerToItem.Keys;
-
-        /// <summary>
-        /// Gets the items of currently materialized containers.
-        /// </summary>
-        public IEnumerable<object> Items => _containerToItem.Values;
-
-        /// <summary>
-        /// Adds an entry to the index.
-        /// </summary>
-        /// <param name="item">The item.</param>
-        /// <param name="container">The item container.</param>
-        public void Add(object item, Control container)
-        {
-            _itemToContainer[item] = container;
-            if (_itemToContainerSet.TryGetValue(item, out var set))
-            {
-                set.Add(container);
-            }
-            else
-            {
-                _itemToContainerSet.Add(item, new HashSet<Control> { container });
-            }
-
-            _containerToItem.Add(container, item);
-
-            Materialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(new ItemContainerInfo(container, item, 0)));
-        }
-
-        /// <summary>
-        /// Removes a container from private collections.
-        /// </summary>
-        /// <param name="container">The item container.</param>
-        /// <param name="item">The DataContext object</param>
-        private void RemoveContainer(Control container, object item)
-        {
-            if (_itemToContainerSet.TryGetValue(item, out var set))
-            {
-                set.Remove(container);
-                if (set.Count == 0)
-                {
-                    _itemToContainerSet.Remove(item);
-                    _itemToContainer.Remove(item);
-                }
-                else
-                {
-                    _itemToContainer[item] = set.First();
-                }
-            }
-        }
-        
-        /// <summary>
-        /// Removes a container from the index.
-        /// </summary>
-        /// <param name="container">The item container.</param>
-        public void Remove(Control container)
-        {
-            var item = _containerToItem[container];
-            _containerToItem.Remove(container);
-            RemoveContainer(container, item);
-
-            Dematerialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(new ItemContainerInfo(container, item, 0)));
-        }
-
-        /// <summary>
-        /// Removes a set of containers from the index.
-        /// </summary>
-        /// <param name="startingIndex">The index of the first item.</param>
-        /// <param name="containers">The item containers.</param>
-        public void Remove(int startingIndex, IEnumerable<ItemContainerInfo> containers)
-        {
-            foreach (var container in containers)
-            {
-                var item = _containerToItem[container.ContainerControl];
-                _containerToItem.Remove(container.ContainerControl);
-                RemoveContainer(container.ContainerControl, item);
-            }
-
-            Dematerialized?.Invoke(
-                this,
-                new ItemContainerEventArgs(startingIndex, containers.ToList()));
-        }
-
-        /// <summary>
-        /// Gets the container for an item.
-        /// </summary>
-        /// <param name="item">The item.</param>
-        /// <returns>The container, or null of not found.</returns>
-        public Control? ContainerFromItem(object item)
-        {
-            if (item != null)
-            {
-                _itemToContainer.TryGetValue(item, out var result);
-                if (result == null)
-                {
-                    _itemToContainerSet.TryGetValue(item, out var set);
-                    if (set?.Count > 0)
-                    {
-                        return set.FirstOrDefault();
-                    }
-                }
-                return result;
-            }
-
-            return null;
-        }
-
-        /// <summary>
-        /// Gets the item for a container.
-        /// </summary>
-        /// <param name="container">The container.</param>
-        /// <returns>The item, or null of not found.</returns>
-        public object? ItemFromContainer(Control? container)
-        {
-            if (container != null)
-            {
-                _containerToItem.TryGetValue(container, out var result);
-                if (result != null)
-                {
-                    _itemToContainer[result] = container;
-                }
-                return result;
-            }
-
-            return null;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
deleted file mode 100644
index b7111c0ef2..0000000000
--- a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
+++ /dev/null
@@ -1,164 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-
-namespace Avalonia.Controls.Generators
-{
-    /// <summary>
-    /// Creates containers for tree items and maintains a list of created containers.
-    /// </summary>
-    /// <typeparam name="T">The type of the container.</typeparam>
-    public class TreeItemContainerGenerator<T> : ItemContainerGenerator<T>, ITreeItemContainerGenerator
-        where T : Control, new()
-    {
-        private TreeView? _treeView;
-
-        /// <summary>
-        /// Initializes a new instance of the <see cref="TreeItemContainerGenerator{T}"/> class.
-        /// </summary>
-        /// <param name="owner">The owner control.</param>
-        /// <param name="contentProperty">The container's Content property.</param>
-        /// <param name="contentTemplateProperty">The container's ContentTemplate property.</param>
-        /// <param name="itemsProperty">The container's Items property.</param>
-        /// <param name="isExpandedProperty">The container's IsExpanded property.</param>
-        public TreeItemContainerGenerator(
-            Control owner,
-            AvaloniaProperty contentProperty,
-            AvaloniaProperty contentTemplateProperty,
-            AvaloniaProperty itemsProperty,
-            AvaloniaProperty isExpandedProperty)
-            : base(owner, contentProperty, contentTemplateProperty)
-        {
-            ItemsProperty = itemsProperty ?? throw new ArgumentNullException(nameof(itemsProperty));
-            IsExpandedProperty = isExpandedProperty ?? throw new ArgumentNullException(nameof(isExpandedProperty));
-            UpdateIndex();
-        }
-
-        /// <summary>
-        /// Gets the container index for the tree.
-        /// </summary>
-        public TreeContainerIndex? Index { get; private set; }
-
-        /// <summary>
-        /// Gets the item container's Items property.
-        /// </summary>
-        protected AvaloniaProperty ItemsProperty { get; }
-
-        /// <summary>
-        /// Gets the item container's IsExpanded property.
-        /// </summary>
-        protected AvaloniaProperty IsExpandedProperty { get; }
-
-        /// <inheritdoc/>
-        protected override Control? CreateContainer(object? item)
-        {
-            var container = item as T;
-
-            if (item == null)
-            {
-                return null;
-            }
-            else if (container != null)
-            {
-                Index?.Add(item, container);
-                return container;
-            }
-            else
-            {
-                var template = GetTreeDataTemplate(item, ItemTemplate);
-                var result = new T();
-
-                if (ItemContainerTheme != null)
-                {
-                    result.SetValue(Control.ThemeProperty, ItemContainerTheme, BindingPriority.Style);
-                }
-
-                if (DisplayMemberBinding is not null)
-                {
-                    result.SetValue(StyledElement.DataContextProperty, item, BindingPriority.Style);
-                    result.Bind(ContentProperty, DisplayMemberBinding, BindingPriority.Style);
-                }
-                else
-                {
-                    result.SetValue(ContentProperty, template.Build(item), BindingPriority.Style);
-                }
-
-                var itemsSelector = template.ItemsSelector(item);
-
-                if (itemsSelector != null)
-                {
-                    BindingOperations.Apply(result, ItemsProperty, itemsSelector, null);
-                }
-
-                if (!(item is Control))
-                {
-                    result.DataContext = item;
-                }
-
-                Index?.Add(item, result);
-
-                return result;
-            }
-        }
-
-        public override IEnumerable<ItemContainerInfo> Clear()
-        {
-            var items = base.Clear();
-            Index?.Remove(0, items);
-            return items;
-        }
-
-        public override IEnumerable<ItemContainerInfo> Dematerialize(int startingIndex, int count)
-        {
-            Index?.Remove(startingIndex, GetContainerRange(startingIndex, count));
-            return base.Dematerialize(startingIndex, count);
-        }
-
-        public override IEnumerable<ItemContainerInfo> RemoveRange(int startingIndex, int count)
-        {
-            Index?.Remove(startingIndex, GetContainerRange(startingIndex, count));
-            return base.RemoveRange(startingIndex, count);
-        }
-
-        public override bool TryRecycle(int oldIndex, int newIndex, object item) => false;
-
-        public void UpdateIndex()
-        {
-            if (Owner is TreeView treeViewOwner && Index == null)
-            {
-                Index = new TreeContainerIndex();
-                _treeView = treeViewOwner;
-            }
-            else
-            {
-                var treeView = Owner.GetSelfAndLogicalAncestors().OfType<TreeView>().FirstOrDefault();
-                
-                if (treeView != _treeView)
-                {
-                    Clear();
-                    Index = treeView?.ItemContainerGenerator?.Index;
-                    _treeView = treeView;
-                }
-            }
-        }
-
-        class WrapperTreeDataTemplate : ITreeDataTemplate
-        {
-            private readonly IDataTemplate _inner;
-            public WrapperTreeDataTemplate(IDataTemplate inner) => _inner = inner;
-            public Control? Build(object? param) => _inner.Build(param);
-            public bool Match(object? data) => _inner.Match(data);
-            public InstancedBinding? ItemsSelector(object item) => null;
-        }
-
-        private ITreeDataTemplate GetTreeDataTemplate(object item, IDataTemplate? primary)
-        {
-            var template = Owner.FindDataTemplate(item, primary) ?? FuncDataTemplate.Default;
-            var treeTemplate = template as ITreeDataTemplate ?? new WrapperTreeDataTemplate(template);
-            return treeTemplate;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e51296cdec..c4356e2967 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -3,8 +3,8 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Linq;
-using Avalonia.Collections;
 using Avalonia.Automation.Peers;
+using Avalonia.Collections;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
@@ -15,7 +15,6 @@ using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
-using Avalonia.VisualTree;
 using Avalonia.Styling;
 
 namespace Avalonia.Controls
@@ -81,7 +80,7 @@ namespace Avalonia.Controls
         
         private IEnumerable? _items = new AvaloniaList<object>();
         private int _itemCount;
-        private IItemContainerGenerator? _itemContainerGenerator;
+        private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
 
         /// <summary>
@@ -103,27 +102,9 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Gets the <see cref="IItemContainerGenerator"/> for the control.
+        /// Gets the <see cref="ItemContainerGenerator"/> for the control.
         /// </summary>
-        public IItemContainerGenerator ItemContainerGenerator
-        {
-            get
-            {
-                if (_itemContainerGenerator == null)
-                {
-                    _itemContainerGenerator = CreateItemContainerGenerator();
-
-                    _itemContainerGenerator.ItemContainerTheme = ItemContainerTheme;
-                    _itemContainerGenerator.ItemTemplate = ItemTemplate;
-                    _itemContainerGenerator.DisplayMemberBinding = DisplayMemberBinding;
-                    _itemContainerGenerator.Materialized += (_, e) => OnContainersMaterialized(e);
-                    _itemContainerGenerator.Dematerialized += (_, e) => OnContainersDematerialized(e);
-                    _itemContainerGenerator.Recycled += (_, e) => OnContainersRecycled(e);
-                }
-
-                return _itemContainerGenerator;
-            }
-        }
+        public ItemContainerGenerator ItemContainerGenerator => _itemContainerGenerator ??= new(this);
 
         /// <summary>
         /// Gets or sets the items to display.
@@ -174,11 +155,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets the items presenter control.
         /// </summary>
-        public ItemsPresenter? Presenter
-        {
-            get;
-            protected set;
-        }
+        public ItemsPresenter? Presenter { get; private set; }
 
         private protected bool WrapFocus { get; set; }
 
@@ -188,6 +165,52 @@ namespace Avalonia.Controls
             remove => _childIndexChanged -= value;
         }
 
+        /// <summary>
+        /// Returns the container for the item at the specified index.
+        /// </summary>
+        /// <param name="index">The index of the item to retrieve.</param>
+        /// <returns>
+        /// The container for the item at the specified index within the item collection, if the
+        /// item has a container; otherwise, null.
+        /// </returns>
+        public Control? ContainerFromIndex(int index) => Presenter?.ContainerFromIndex(index);
+
+        /// <summary>
+        /// Returns the container corresponding to the specified item.
+        /// </summary>
+        /// <param name="item">The item to retrieve the container for.</param>
+        /// <returns>
+        /// A container that corresponds to the specified item, if the item has a container and
+        /// exists in the collection; otherwise, null.
+        /// </returns>
+        public Control? ContainerFromItem(object item)
+        {
+            throw new NotImplementedException();
+        }
+
+        /// <summary>
+        /// Returns the index to the item that has the specified, generated container.
+        /// </summary>
+        /// <param name="container">The generated container to retrieve the item index for.</param>
+        /// <returns>
+        /// The index to the item that corresponds to the specified generated container, or -1 if 
+        /// <paramref name="container"/> is not found.
+        /// </returns>
+        public int IndexFromContainer(Control container) => Presenter?.IndexFromContainer(container) ?? -1;
+
+        /// <summary>
+        /// Returns the item that corresponds to the specified, generated container.
+        /// </summary>
+        /// <param name="container">The control that corresponds to the item to be returned.</param>
+        /// <returns>
+        /// The contained item, or the container if it does not contain an item.
+        /// </returns>
+        public object? ItemFromContainer(Control container)
+        {
+            // TODO: Should this throw or return null of container isn't a container?
+            throw new NotImplementedException();
+        }
+
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
@@ -197,7 +220,7 @@ namespace Avalonia.Controls
             }
 
             Presenter = presenter;
-            ItemContainerGenerator?.Clear();
+            ////ItemContainerGenerator?.Clear();
 
             if (Presenter is IChildIndexProvider innerProvider)
             {
@@ -237,6 +260,47 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Creates or a container that can be used to display an item.
+        /// </summary>
+        protected internal virtual Control CreateContainerOverride() => new ContentPresenter();
+
+        /// <summary>
+        /// Prepares the specified element to display the specified item.
+        /// </summary>
+        /// <param name="container">The element that's used to display the specified item.</param>
+        /// <param name="item">The item to display.</param>
+        /// <param name="index">The index of the item to display.</param>
+        protected internal virtual void PrepareContainerForItemOverride(Control container, object? item, int index)
+        {
+            if (container == item)
+                return;
+
+            if (container is ContentControl cc)
+            {
+                cc.SetValue(ContentControl.ContentProperty, item, BindingPriority.Template);
+                if (ItemTemplate is { } it)
+                    cc.SetValue(ContentControl.ContentTemplateProperty, it, BindingPriority.Template);
+            }
+            else if (container is ContentPresenter p)
+            {
+                p.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Template);
+                if (ItemTemplate is { } it)
+                    p.SetValue(ContentPresenter.ContentTemplateProperty, it, BindingPriority.Template);
+            }
+
+            if (ItemContainerTheme is not null)
+                container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
+        }
+
+        /// <summary>
+        /// Undoes the effects of the <see cref="PrepareContainerForItemOverride(Control, object?, int)"/> method.
+        /// </summary>
+        /// <param name="container">The container element.</param>
+        protected internal virtual void ClearContainerForItemOverride(Control container)
+        {
+        }
+
         /// <summary>
         /// Gets the index of an item in a collection.
         /// </summary>
@@ -273,60 +337,11 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Creates the <see cref="ItemContainerGenerator"/> for the control.
+        /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
-        /// <returns>
-        /// An <see cref="IItemContainerGenerator"/>.
-        /// </returns>
-        protected virtual IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator(this);
-        }
-
-        /// <summary>
-        /// Called when new containers are materialized for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersMaterialized(ItemContainerEventArgs e)
-        {
-            foreach (var container in e.Containers)
-            {
-                // If the item is its own container, then it will be added to the logical tree when
-                // it was added to the Items collection.
-                if (container.ContainerControl != null && container.ContainerControl != container.Item)
-                {
-                    LogicalChildren.Add(container.ContainerControl);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Called when containers are dematerialized for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersDematerialized(ItemContainerEventArgs e)
-        {
-            foreach (var container in e.Containers)
-            {
-                // If the item is its own container, then it will be removed from the logical tree
-                // when it is removed from the Items collection.
-                if (container.ContainerControl != container.Item)
-                {
-                    LogicalChildren.Remove(container.ContainerControl);
-                }
-            }
-        }
-
-        /// <summary>
-        /// Called when containers are recycled for the <see cref="ItemsControl"/> by its
-        /// <see cref="ItemContainerGenerator"/>.
-        /// </summary>
-        /// <param name="e">The details of the containers.</param>
-        protected virtual void OnContainersRecycled(ItemContainerEventArgs e)
-        {
-        }
+        /// <param name="item">The item to check.</param>
+        /// <returns>true if the item is (or is eligible to be) its own container; otherwise, false.</returns>
+        protected internal virtual bool IsItemItsOwnContainerOverride(Control item) => true;
 
         /// <summary>
         /// Handles directional navigation within the <see cref="ItemsControl"/>.
@@ -387,7 +402,8 @@ namespace Avalonia.Controls
             }
             else if (change.Property == ItemContainerThemeProperty && _itemContainerGenerator is not null)
             {
-                _itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
+                throw new NotImplementedException();
+                ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
             }
         }
 
@@ -433,6 +449,27 @@ namespace Avalonia.Controls
             }
         }
 
+        internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
+        internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
+        internal void ClearLogicalChildren() => LogicalChildren.Clear();
+
+        internal void PrepareItemContainer(Control container, object? item, int index)
+        {
+            var itemContainerTheme = ItemContainerTheme;
+
+            if (itemContainerTheme is not null && 
+                !container.IsSet(ThemeProperty) &&
+                ((IStyleable)container).StyleKey == itemContainerTheme.TargetType)
+            {
+                container.Theme = itemContainerTheme;
+            }
+
+            if (item is not Control)
+                container.DataContext = item;
+
+            PrepareContainerForItemOverride(container, item, index);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
@@ -501,7 +538,7 @@ namespace Avalonia.Controls
         {
             if (_itemContainerGenerator != null)
             {
-                _itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
+                ////_itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
                 // TODO: Rebuild the item containers.
             }
         }
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index a8a926691a..78a2d5d990 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -103,14 +103,7 @@ namespace Avalonia.Controls
         /// </summary>
         public void UnselectAll() => Selection.Clear();
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<ListBoxItem>(
-                this, 
-                ListBoxItem.ContentProperty,
-                ListBoxItem.ContentTemplateProperty);
-        }
+        protected internal override Control CreateContainerOverride() => new ListBoxItem();
 
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index bd7a2749c5..3b211d4cc7 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -99,9 +99,10 @@ namespace Avalonia.Controls
         {
             get
             {
-                return ItemContainerGenerator.Containers
-                    .Select(x => x.ContainerControl)
-                    .OfType<IMenuItem>();
+                throw new NotImplementedException();
+                ////return ItemContainerGenerator.Containers
+                ////    .Select(x => x.ContainerControl)
+                ////    .OfType<IMenuItem>();
             }
         }
 
@@ -141,12 +142,6 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         bool IMenuElement.MoveSelection(NavigationDirection direction, bool wrap) => MoveSelection(direction, wrap);
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<MenuItem>(this, MenuItem.HeaderProperty, null);
-        }
-
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index 3e00cea430..d134704b26 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -332,9 +332,10 @@ namespace Avalonia.Controls
         {
             get
             {
-                return ItemContainerGenerator.Containers
-                    .Select(x => x.ContainerControl)
-                    .OfType<IMenuItem>();
+                throw new NotImplementedException();
+                ////return ItemContainerGenerator.Containers
+                ////    .Select(x => x.ContainerControl)
+                ////    .OfType<IMenuItem>();
             }
         }
 
@@ -357,12 +358,6 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         void IMenuItem.RaiseClick() => RaiseEvent(new RoutedEventArgs(ClickEvent));
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new MenuItemContainerGenerator(this);
-        }
-
         protected override void OnPointerReleased(PointerReleasedEventArgs e)
         {
             base.OnPointerReleased(e);
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index b731f48d9c..5f90c264d7 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics;
 
 namespace Avalonia.Controls.Presenters
@@ -13,7 +14,7 @@ namespace Avalonia.Controls.Presenters
         public static readonly StyledProperty<ITemplate<Panel>> ItemsPanelProperty =
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
-        private ItemsPresenterContainerGenerator? _generator;
+        private PanelContainerGenerator? _generator;
 
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
@@ -52,7 +53,10 @@ namespace Avalonia.Controls.Presenters
 
         internal void ScrollIntoView(int index)
         {
-
+            if (Panel is VirtualizingPanel v)
+                v.ScrollIntoView(index);
+            else if (index >= 0 && index < Panel?.Children.Count)
+                Panel.Children[index].BringIntoView();
         }
 
         protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
@@ -97,5 +101,20 @@ namespace Avalonia.Controls.Presenters
             _generator?.Dispose();
             _generator = new(this);
         }
+
+        internal Control? ContainerFromIndex(int index)
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.ContainerFromIndex(index);
+            return index >= 0 && index < Panel?.Children.Count ? Panel.Children[index] : null;
+        }
+
+        internal int IndexFromContainer(Control container)
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.IndexFromContainer(container);
+            return Panel?.Children.IndexOf(container) ?? -1;
+        }
+
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
similarity index 66%
rename from src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
rename to src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 233635a414..f1765ba986 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenterContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -9,11 +9,11 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Generates containers for <see cref="ItemsPresenter"/>s that have non-virtualizing panels.
     /// </summary>
-    internal class ItemsPresenterContainerGenerator : IDisposable
+    internal class PanelContainerGenerator : IDisposable
     {
         private readonly ItemsPresenter _presenter;
 
-        public ItemsPresenterContainerGenerator(ItemsPresenter presenter)
+        public PanelContainerGenerator(ItemsPresenter presenter)
         {
             Debug.Assert(presenter.ItemsControl is not null);
             Debug.Assert(presenter.Panel is not null or VirtualizingPanel);
@@ -29,12 +29,17 @@ namespace Avalonia.Controls.Presenters
 
         public void Dispose()
         {
-            _presenter.ItemsControl!.PropertyChanged -= OnItemsControlPropertyChanged;
+            if (_presenter.ItemsControl is { } itemsControl)
+            {
+                itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
 
-            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged -= OnItemsChanged;
+                if (itemsControl.Items is INotifyCollectionChanged incc)
+                    incc.CollectionChanged -= OnItemsChanged;
 
-            _presenter.Panel!.Children.Clear();
+                itemsControl.ClearLogicalChildren();
+            }
+
+            _presenter.Panel?.Children.Clear();
         }
 
         private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
@@ -51,58 +56,68 @@ namespace Avalonia.Controls.Presenters
 
         private void OnItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            if (_presenter.ItemsControl?.Items is null || _presenter.Panel is null)
+            if (_presenter.Panel is null || _presenter.ItemsControl is null)
                 return;
 
-            var generator = _presenter.ItemsControl.ItemContainerGenerator;
+            var itemsControl = _presenter.ItemsControl;
             var panel = _presenter.Panel;
 
             void Add(int index, IEnumerable items)
             {
                 var i = index;
-
                 foreach (var item in items)
-                {
-                    var c = generator.Materialize(i, item);
-                    panel.Children.Insert(i++, c.ContainerControl);
-                }
+                    panel.Children.Insert(i++, CreateContainer(itemsControl, item, i));
             }
             
             void Remove(int index, int count)
             {
                 for (var i = 0; i < count; ++i)
+                {
+                    itemsControl.RemoveLogicalChild(panel.Children[i + index]);
                     panel.Children.RemoveAt(i + index);
+                }
             }
 
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Replace:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Move:
-                    generator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    generator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    generator.Clear();
+                    itemsControl.ClearLogicalChildren();
                     panel.Children.Clear();
-                    if (_presenter.ItemsControl.Items is { } items)
+                    if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
                     break;
             }
         }
+
+        private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
+        {
+            var generator = itemsControl.ItemContainerGenerator;
+
+            if (item is Control c && generator.IsItemItsOwnContainer(c))
+            {
+                return c;
+            }
+            else
+            {
+                c = generator.CreateContainer();
+                itemsControl.AddLogicalChild(c);
+                generator.PrepareItemContainer(c, item, index);
+                return c;
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 44fa78ac21..1503da1322 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
+using System.Xml.Linq;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Selection;
 using Avalonia.Data;
@@ -391,7 +392,7 @@ namespace Avalonia.Controls.Primitives
             for (var current = eventSource as Visual; current != null; current = current.VisualParent)
             {
                 if (current is Control control && control.Parent == this &&
-                    ItemContainerGenerator?.IndexFromContainer(control) != -1)
+                    IndexFromContainer(control) != -1)
                 {
                     return control;
                 }
@@ -432,54 +433,34 @@ namespace Avalonia.Controls.Primitives
             }
         }
 
-        /// <inheritdoc/>
-        protected override void OnContainersMaterialized(ItemContainerEventArgs e)
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
-            base.OnContainersMaterialized(e);
+            base.PrepareContainerForItemOverride(element, item, index);
 
-            foreach (var container in e.Containers)
+            if ((element as ISelectable)?.IsSelected == true)
             {
-                if ((container.ContainerControl as ISelectable)?.IsSelected == true)
-                {
-                    Selection.Select(container.Index);
-                    MarkContainerSelected(container.ContainerControl, true);
-                }
-                else
-                {
-                    var selected = Selection.IsSelected(container.Index);
-                    MarkContainerSelected(container.ContainerControl, selected);
-                }
+                Selection.Select(index);
+                MarkContainerSelected(element, true);
             }
-        }
-
-        /// <inheritdoc/>
-        protected override void OnContainersDematerialized(ItemContainerEventArgs e)
-        {
-            base.OnContainersDematerialized(e);
-
-            if (Presenter?.Panel is InputElement panel)
+            else
             {
-                foreach (var container in e.Containers)
-                {
-                    if (KeyboardNavigation.GetTabOnceActiveElement(panel) == container.ContainerControl)
-                    {
-                        KeyboardNavigation.SetTabOnceActiveElement(panel, null);
-                        break;
-                    }
-                }
+                var selected = Selection.IsSelected(index);
+                MarkContainerSelected(element, selected);
             }
         }
 
-        protected override void OnContainersRecycled(ItemContainerEventArgs e)
+        protected internal override void ClearContainerForItemOverride(Control element)
         {
-            foreach (var i in e.Containers)
+            base.ClearContainerForItemOverride(element);
+
+            if (Presenter?.Panel is InputElement panel && 
+                KeyboardNavigation.GetTabOnceActiveElement(panel) == element)
             {
-                if (i.ContainerControl != null && i.Item != null)
-                {
-                    bool selected = Selection.IsSelected(i.Index);
-                    MarkContainerSelected(i.ContainerControl, selected);
-                }
+                KeyboardNavigation.SetTabOnceActiveElement(panel, null);
             }
+
+            if (element is ISelectable selectable)
+                MarkContainerSelected(element, false);
         }
 
         /// <inheritdoc/>
@@ -526,44 +507,45 @@ namespace Avalonia.Controls.Primitives
 
         protected override void OnTextInput(TextInputEventArgs e)
         {
-            if (!e.Handled)
-            {
-                if (!IsTextSearchEnabled)
-                    return;
-
-                StopTextSearchTimer();
-
-                _textSearchTerm += e.Text;
-
-                bool Match(ItemContainerInfo info)
-                {
-                    if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
-                    {
-                        var searchText = ao.GetValue(TextSearch.TextProperty);
-
-                        if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
-                        {
-                            return true;
-                        }
-                    }
-
-                    return info.ContainerControl is IContentControl control &&
-                           control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
-                }
+            throw new NotImplementedException();
+            ////if (!e.Handled)
+            ////{
+            ////    if (!IsTextSearchEnabled)
+            ////        return;
+
+            ////    StopTextSearchTimer();
+
+            ////    _textSearchTerm += e.Text;
+
+            ////    bool Match(ItemContainerInfo info)
+            ////    {
+            ////        if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
+            ////        {
+            ////            var searchText = ao.GetValue(TextSearch.TextProperty);
+
+            ////            if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
+            ////            {
+            ////                return true;
+            ////            }
+            ////        }
+
+            ////        return info.ContainerControl is IContentControl control &&
+            ////               control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
+            ////    }
                 
-                var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
+            ////    var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
 
-                if (info != null)
-                {
-                    SelectedIndex = info.Index;
-                }
+            ////    if (info != null)
+            ////    {
+            ////        SelectedIndex = info.Index;
+            ////    }
 
-                StartTextSearchTimer();
+            ////    StartTextSearchTimer();
 
-                e.Handled = true;
-            }
+            ////    e.Handled = true;
+            ////}
 
-            base.OnTextInput(e);
+            ////base.OnTextInput(e);
         }
 
         protected override void OnKeyDown(KeyEventArgs e)
@@ -634,7 +616,7 @@ namespace Avalonia.Controls.Primitives
         /// <returns>True if the selection was moved; otherwise false.</returns>
         protected bool MoveSelection(NavigationDirection direction, bool wrap)
         {
-            var from = SelectedIndex != -1 ? ItemContainerGenerator?.ContainerFromIndex(SelectedIndex) : null;
+            var from = SelectedIndex != -1 ? ContainerFromIndex(SelectedIndex) : null;
             return MoveSelection(from, direction, wrap);
         }
 
@@ -650,7 +632,7 @@ namespace Avalonia.Controls.Primitives
             if (Presenter?.Panel is INavigableContainer container &&
                 GetNextControl(container, direction, from, wrap) is Control next)
             {
-                var index = ItemContainerGenerator?.IndexFromContainer(next) ?? -1;
+                var index = IndexFromContainer(next);
 
                 if (index != -1)
                 {
@@ -733,7 +715,7 @@ namespace Avalonia.Controls.Primitives
 
             if (Presenter?.Panel != null)
             {
-                var container = ItemContainerGenerator?.ContainerFromIndex(index);
+                var container = ContainerFromIndex(index);
                 KeyboardNavigation.SetTabOnceActiveElement(
                     (InputElement)Presenter.Panel,
                     container);
@@ -757,7 +739,7 @@ namespace Avalonia.Controls.Primitives
             bool rightButton = false,
             bool fromFocus = false)
         {
-            var index = ItemContainerGenerator?.IndexFromContainer(container) ?? -1;
+            var index = IndexFromContainer(container);
 
             if (index != -1)
             {
@@ -842,7 +824,7 @@ namespace Avalonia.Controls.Primitives
         {
             void Mark(int index, bool selected)
             {
-                var container = ItemContainerGenerator?.ContainerFromIndex(index);
+                var container = ContainerFromIndex(index);
 
                 if (container != null)
                 {
@@ -909,7 +891,7 @@ namespace Avalonia.Controls.Primitives
                 e.Source is Control control &&
                 e.Source is ISelectable selectable &&
                 control.Parent == this &&
-                ItemContainerGenerator?.IndexFromContainer(control) != -1)
+                IndexFromContainer(control) != -1)
             {
                 UpdateSelection(control, selectable.IsSelected);
             }
@@ -961,7 +943,7 @@ namespace Avalonia.Controls.Primitives
                 {
                     MarkContainerSelected(
                         container,
-                        Selection.IsSelected(ItemContainerGenerator.IndexFromContainer(container)));
+                        Selection.IsSelected(IndexFromContainer(container)));
                 }
             }
         }
diff --git a/src/Avalonia.Controls/Primitives/TabStrip.cs b/src/Avalonia.Controls/Primitives/TabStrip.cs
index d27b1faaed..a6a6f4cec8 100644
--- a/src/Avalonia.Controls/Primitives/TabStrip.cs
+++ b/src/Avalonia.Controls/Primitives/TabStrip.cs
@@ -18,14 +18,6 @@ namespace Avalonia.Controls.Primitives
             ItemsPanelProperty.OverrideDefaultValue<TabStrip>(DefaultPanel);
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new ItemContainerGenerator<TabStripItem>(
-                this,
-                ContentControl.ContentProperty,
-                ContentControl.ContentTemplateProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 2e7059b838..8ce1befde5 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -165,15 +165,15 @@ namespace Avalonia.Controls
             return RegisterContentPresenter(presenter);
         }
 
-        protected override void OnContainersMaterialized(ItemContainerEventArgs e)
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
-            base.OnContainersMaterialized(e);
+            base.PrepareContainerForItemOverride(element, item, index);
             UpdateSelectedContent();
         }
 
-        protected override void OnContainersRecycled(ItemContainerEventArgs e)
+        protected internal override void ClearContainerForItemOverride(Control element)
         {
-            base.OnContainersRecycled(e);
+            base.ClearContainerForItemOverride(element);
             UpdateSelectedContent();
         }
 
@@ -207,11 +207,6 @@ namespace Avalonia.Controls
             return false;
         }
 
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            return new TabItemContainerGenerator(this);
-        }
-
         protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
             ItemsPresenterPart = e.NameScope.Get<ItemsPresenter>("PART_ItemsPresenter");
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 2fa4a02fa2..6336219fb6 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -75,12 +75,6 @@ namespace Avalonia.Controls
             remove => RemoveHandler(SelectingItemsControl.SelectionChangedEvent, value);
         }
 
-        /// <summary>
-        /// Gets the <see cref="ITreeItemContainerGenerator"/> for the tree view.
-        /// </summary>
-        public new ITreeItemContainerGenerator ItemContainerGenerator =>
-            (ITreeItemContainerGenerator)base.ItemContainerGenerator;
-
         /// <summary>
         /// Gets or sets a value indicating whether to automatically scroll to newly selected items.
         /// </summary>
@@ -188,7 +182,8 @@ namespace Avalonia.Controls
         /// </remarks>
         public void SelectAll()
         {
-            SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
+            throw new NotImplementedException();
+            ////SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
         }
 
         /// <summary>
@@ -242,7 +237,7 @@ namespace Avalonia.Controls
 
                     if (AutoScrollToSelectedItem)
                     {
-                        var container = ItemContainerGenerator.Index!.ContainerFromItem(e.NewItems![0]!);
+                        var container = ContainerFromItem(e.NewItems![0]!);
 
                         container?.BringIntoView();
                     }
@@ -282,9 +277,10 @@ namespace Avalonia.Controls
                     break;
                 case NotifyCollectionChangedAction.Reset:
 
-                    foreach (Control container in ItemContainerGenerator.Index!.Containers)
+                    foreach (var child in LogicalChildren)
                     {
-                        MarkContainerSelected(container, false);
+                        if (child is Control container && IndexFromContainer(container) != -1)
+                            MarkContainerSelected(container, false);
                     }
 
                     if (SelectedItems.Count > 0)
@@ -337,7 +333,7 @@ namespace Avalonia.Controls
 
         private void MarkItemSelected(object item, bool selected)
         {
-            var container = ItemContainerGenerator.Index!.ContainerFromItem(item)!;
+            var container = ContainerFromItem(item)!;
 
             MarkContainerSelected(container, selected);
         }
@@ -378,8 +374,8 @@ namespace Avalonia.Controls
                 if (!this.IsVisualAncestorOf((Visual)element))
                 {
                     var result = _selectedItem != null ?
-                        ItemContainerGenerator.Index!.ContainerFromItem(_selectedItem) :
-                        ItemContainerGenerator.ContainerFromIndex(0);
+                        ContainerFromItem(_selectedItem) :
+                        ContainerFromIndex(0);
                     
                     return (result != null, result); // SelectedItem may not be in the treeview.
                 }
@@ -390,27 +386,6 @@ namespace Avalonia.Controls
             return (false, null);
         }
 
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator()
-        {
-            var result = CreateTreeItemContainerGenerator();
-            result.Index!.Materialized += ContainerMaterialized;
-            return result;
-        }
-
-        protected virtual ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-            CreateTreeItemContainerGenerator<TreeViewItem>();
-
-        protected ITreeItemContainerGenerator CreateTreeItemContainerGenerator<TVItem>() where TVItem: TreeViewItem, new()
-        {
-            return new TreeItemContainerGenerator<TVItem>(
-                this,
-                TreeViewItem.HeaderProperty,
-                TreeViewItem.ItemTemplateProperty,
-                TreeViewItem.ItemsProperty,
-                TreeViewItem.IsExpandedProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -466,53 +441,54 @@ namespace Avalonia.Controls
             NavigationDirection direction,
             bool intoChildren)
         {
-            IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
-
-            if (parentGenerator == null)
-            {
-                return null;
-            }
-
-            var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
-            var parent = from?.Parent as ItemsControl;
-            TreeViewItem? result = null;
-
-            switch (direction)
-            {
-                case NavigationDirection.Up:
-                    if (index > 0)
-                    {
-                        var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
-                        result = previous.IsExpanded && previous.ItemCount > 0 ?
-                            (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
-                            previous;
-                    }
-                    else
-                    {
-                        result = from?.Parent as TreeViewItem;
-                    }
-
-                    break;
-
-                case NavigationDirection.Down:
-                case NavigationDirection.Right:
-                    if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
-                    {
-                        result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
-                    }
-                    else if (index < parent?.ItemCount - 1)
-                    {
-                        result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
-                    }
-                    else if (parent is TreeViewItem parentItem)
-                    {
-                        return GetContainerInDirection(parentItem, direction, false);
-                    }
-
-                    break;
-            }
-
-            return result;
+            throw new NotImplementedException();
+            ////IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
+
+            ////if (parentGenerator == null)
+            ////{
+            ////    return null;
+            ////}
+
+            ////var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
+            ////var parent = from?.Parent as ItemsControl;
+            ////TreeViewItem? result = null;
+
+            ////switch (direction)
+            ////{
+            ////    case NavigationDirection.Up:
+            ////        if (index > 0)
+            ////        {
+            ////            var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
+            ////            result = previous.IsExpanded && previous.ItemCount > 0 ?
+            ////                (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
+            ////                previous;
+            ////        }
+            ////        else
+            ////        {
+            ////            result = from?.Parent as TreeViewItem;
+            ////        }
+
+            ////        break;
+
+            ////    case NavigationDirection.Down:
+            ////    case NavigationDirection.Right:
+            ////        if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
+            ////        {
+            ////            result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
+            ////        }
+            ////        else if (index < parent?.ItemCount - 1)
+            ////        {
+            ////            result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
+            ////        }
+            ////        else if (parent is TreeViewItem parentItem)
+            ////        {
+            ////            return GetContainerInDirection(parentItem, direction, false);
+            ////        }
+
+            ////        break;
+            ////}
+
+            ////return result;
         }
 
         /// <inheritdoc/>
@@ -551,80 +527,63 @@ namespace Avalonia.Controls
             bool toggleModifier = false,
             bool rightButton = false)
         {
-            var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
-
-            if (item == null)
-            {
-                return;
-            }
-
-            Control? selectedContainer = null;
-
-            if (SelectedItem != null)
-            {
-                selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
-            }
-
-            var mode = SelectionMode;
-            var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
-            var multi = mode.HasAllFlags(SelectionMode.Multiple);
-            var range = multi && rangeModifier && selectedContainer != null;
-
-            if (rightButton)
-            {
-                if (!SelectedItems.Contains(item))
-                {
-                    SelectSingleItem(item);
-                }
-            }
-            else if (!toggle && !range)
-            {
-                SelectSingleItem(item);
-            }
-            else if (multi && range)
-            {
-                SynchronizeItems(
-                    SelectedItems,
-                    GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
-            }
-            else
-            {
-                var i = SelectedItems.IndexOf(item);
-
-                if (i != -1)
-                {
-                    SelectedItems.Remove(item);
-                }
-                else
-                {
-                    if (multi)
-                    {
-                        SelectedItems.Add(item);
-                    }
-                    else
-                    {
-                        SelectedItem = item;
-                    }
-                }
-            }
-        }
-
-        private static IItemContainerGenerator? GetParentContainerGenerator(TreeViewItem? item)
-        {
-            if (item == null)
-            {
-                return null;
-            }
-
-            switch (item.Parent)
-            {
-                case TreeView treeView:
-                    return treeView.ItemContainerGenerator;
-                case TreeViewItem treeViewItem:
-                    return treeViewItem.ItemContainerGenerator;
-                default:
-                    return null;
-            }
+            throw new NotImplementedException();
+            ////var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
+
+            ////if (item == null)
+            ////{
+            ////    return;
+            ////}
+
+            ////Control? selectedContainer = null;
+
+            ////if (SelectedItem != null)
+            ////{
+            ////    selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
+            ////}
+
+            ////var mode = SelectionMode;
+            ////var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
+            ////var multi = mode.HasAllFlags(SelectionMode.Multiple);
+            ////var range = multi && rangeModifier && selectedContainer != null;
+
+            ////if (rightButton)
+            ////{
+            ////    if (!SelectedItems.Contains(item))
+            ////    {
+            ////        SelectSingleItem(item);
+            ////    }
+            ////}
+            ////else if (!toggle && !range)
+            ////{
+            ////    SelectSingleItem(item);
+            ////}
+            ////else if (multi && range)
+            ////{
+            ////    SynchronizeItems(
+            ////        SelectedItems,
+            ////        GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
+            ////}
+            ////else
+            ////{
+            ////    var i = SelectedItems.IndexOf(item);
+
+            ////    if (i != -1)
+            ////    {
+            ////        SelectedItems.Remove(item);
+            ////    }
+            ////    else
+            ////    {
+            ////        if (multi)
+            ////        {
+            ////            SelectedItems.Add(item);
+            ////        }
+            ////        else
+            ////        {
+            ////            SelectedItem = item;
+            ////        }
+            ////    }
+            ////}
         }
 
         /// <summary>
@@ -639,23 +598,24 @@ namespace Avalonia.Controls
             return FindInContainers(treeView.ItemContainerGenerator, nodeA, nodeB);
         }
 
-        private static TreeViewItem? FindInContainers(ITreeItemContainerGenerator containerGenerator,
+        private static TreeViewItem? FindInContainers(ItemContainerGenerator containerGenerator,
             TreeViewItem nodeA,
             TreeViewItem nodeB)
         {
-            IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
+            throw new NotImplementedException();
+            ////IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
 
-            foreach (ItemContainerInfo container in containers)
-            {
-                TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
+            ////foreach (ItemContainerInfo container in containers)
+            ////{
+            ////    TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
 
-                if (node != null)
-                {
-                    return node;
-                }
-            }
+            ////    if (node != null)
+            ////    {
+            ////        return node;
+            ////    }
+            ////}
 
-            return null;
+            ////return null;
         }
 
         private static TreeViewItem? FindFirstNode(TreeViewItem? node, TreeViewItem nodeA, TreeViewItem nodeB)
@@ -683,59 +643,60 @@ namespace Avalonia.Controls
         /// <param name="to">To container.</param>
         private List<object> GetItemsInRange(TreeViewItem? from, TreeViewItem? to)
         {
-            var items = new List<object>();
+            throw new NotImplementedException();
+            ////var items = new List<object>();
 
-            if (from == null || to == null)
-            {
-                return items;
-            }
+            ////if (from == null || to == null)
+            ////{
+            ////    return items;
+            ////}
 
-            TreeViewItem? firstItem = FindFirstNode(this, from, to);
+            ////TreeViewItem? firstItem = FindFirstNode(this, from, to);
 
-            if (firstItem == null)
-            {
-                return items;
-            }
+            ////if (firstItem == null)
+            ////{
+            ////    return items;
+            ////}
 
-            bool wasReversed = false;
+            ////bool wasReversed = false;
 
-            if (firstItem == to)
-            {
-                var temp = from;
+            ////if (firstItem == to)
+            ////{
+            ////    var temp = from;
 
-                from = to;
-                to = temp;
+            ////    from = to;
+            ////    to = temp;
 
-                wasReversed = true;
-            }
+            ////    wasReversed = true;
+            ////}
 
-            TreeViewItem? node = from;
+            ////TreeViewItem? node = from;
 
-            while (node != to)
-            {
-                var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
+            ////while (node != to)
+            ////{
+            ////    var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
 
-                if (item != null)
-                {
-                    items.Add(item);
-                }
+            ////    if (item != null)
+            ////    {
+            ////        items.Add(item);
+            ////    }
 
-                node = GetContainerInDirection(node, NavigationDirection.Down, true);
-            }
+            ////    node = GetContainerInDirection(node, NavigationDirection.Down, true);
+            ////}
 
-            var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
+            ////var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
 
-            if (toItem != null)
-            {
-                items.Add(toItem);
-            }
+            ////if (toItem != null)
+            ////{
+            ////    items.Add(toItem);
+            ////}
 
-            if (wasReversed)
-            {
-                items.Reverse();
-            }
+            ////if (wasReversed)
+            ////{
+            ////    items.Reverse();
+            ////}
 
-            return items;
+            ////return items;
         }
 
         /// <summary>
@@ -776,19 +737,20 @@ namespace Avalonia.Controls
         /// <returns>The container or null if the event did not originate in a container.</returns>
         protected TreeViewItem? GetContainerFromEventSource(object eventSource)
         {
-            var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
-                .OfType<TreeViewItem>()
-                .FirstOrDefault();
+            throw new NotImplementedException();
+            ////var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
+            ////    .OfType<TreeViewItem>()
+            ////    .FirstOrDefault();
 
-            if (item != null)
-            {
-                if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
-                {
-                    return item;
-                }
-            }
+            ////if (item != null)
+            ////{
+            ////    if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
+            ////    {
+            ////        return item;
+            ////    }
+            ////}
 
-            return null;
+            ////return null;
         }
 
         /// <summary>
@@ -796,30 +758,30 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="sender">The event sender.</param>
         /// <param name="e">The event args.</param>
-        private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
-        {
-            var selectedItem = SelectedItem;
-
-            if (selectedItem == null)
-            {
-                return;
-            }
-
-            foreach (var container in e.Containers)
-            {
-                if (container.Item == selectedItem)
-                {
-                    ((TreeViewItem)container.ContainerControl).IsSelected = true;
-
-                    if (AutoScrollToSelectedItem)
-                    {
-                        Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
-                    }
-
-                    break;
-                }
-            }
-        }
+        ////private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
+        ////{
+        ////    var selectedItem = SelectedItem;
+
+        ////    if (selectedItem == null)
+        ////    {
+        ////        return;
+        ////    }
+
+        ////    foreach (var container in e.Containers)
+        ////    {
+        ////        if (container.Item == selectedItem)
+        ////        {
+        ////            ((TreeViewItem)container.ContainerControl).IsSelected = true;
+
+        ////            if (AutoScrollToSelectedItem)
+        ////            {
+        ////                Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
+        ////            }
+
+        ////            break;
+        ////        }
+        ////    }
+        ////}
 
         /// <summary>
         /// Sets a container's 'selected' class or <see cref="ISelectable.IsSelected"/>.
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 9bfcf5adfa..097fe54f42 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -58,7 +58,6 @@ namespace Avalonia.Controls
             PressedMixin.Attach<TreeViewItem>();
             FocusableProperty.OverrideDefaultValue<TreeViewItem>(true);
             ItemsPanelProperty.OverrideDefaultValue<TreeViewItem>(DefaultPanel);
-            ParentProperty.Changed.AddClassHandler<TreeViewItem>((o, e) => o.OnParentChanged(e));
             RequestBringIntoViewEvent.AddClassHandler<TreeViewItem>((x, e) => x.OnRequestBringIntoView(e));
         }
 
@@ -89,27 +88,6 @@ namespace Avalonia.Controls
             private set { SetAndRaise(LevelProperty, ref _level, value); }
         }
 
-        /// <summary>
-        /// Gets the <see cref="ITreeItemContainerGenerator"/> for the tree view.
-        /// </summary>
-        public new ITreeItemContainerGenerator ItemContainerGenerator =>
-            (ITreeItemContainerGenerator)base.ItemContainerGenerator;
-
-        /// <inheritdoc/>
-        protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<TreeViewItem>();
-
-        /// <inheritdoc/>
-        protected ITreeItemContainerGenerator CreateTreeItemContainerGenerator<TVItem>()
-            where TVItem: TreeViewItem, new()
-        {
-            return new TreeItemContainerGenerator<TVItem>(
-                this,
-                TreeViewItem.HeaderProperty,
-                TreeViewItem.ItemTemplateProperty,
-                TreeViewItem.ItemsProperty,
-                TreeViewItem.IsExpandedProperty);
-        }
-
         /// <inheritdoc/>
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
@@ -118,7 +96,6 @@ namespace Avalonia.Controls
             _treeView = this.GetLogicalAncestors().OfType<TreeView>().FirstOrDefault();
             
             Level = CalculateDistanceFromLogicalParent<TreeView>(this) - 1;
-            ItemContainerGenerator.UpdateIndex();
 
             if (ItemTemplate == null && _treeView?.ItemTemplate != null)
             {
@@ -134,7 +111,6 @@ namespace Avalonia.Controls
         protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
             base.OnDetachedFromLogicalTree(e);
-            ItemContainerGenerator.UpdateIndex();
         }
 
         protected virtual void OnRequestBringIntoView(RequestBringIntoViewEventArgs e)
@@ -219,16 +195,5 @@ namespace Avalonia.Controls
 
             return logical != null ? result : @default;
         }
-
-        private void OnParentChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (!((ILogical)this).IsAttachedToLogicalTree && e.NewValue is null)
-            {
-                // If we're not attached to the logical tree, then OnDetachedFromLogicalTree isn't going to be
-                // called when the item is removed. This results in the item not being removed from the index,
-                // causing #3551. In this case, update the index when Parent is changed to null.
-                ItemContainerGenerator.UpdateIndex();
-            }
-        }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 19b1c4002c..dd40f868d5 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,5 +1,7 @@
-using System.Collections;
+using System;
+using System.Collections;
 using System.Collections.Specialized;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
 
 namespace Avalonia.Controls
@@ -25,6 +27,32 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Scrolls the specified item into view.
+        /// </summary>
+        /// <param name="index">The index of the item.</param>
+        protected internal abstract void ScrollIntoView(int index);
+
+        /// <summary>
+        /// Returns the container for the item at the specified index.
+        /// </summary>
+        /// <param name="index">The index of the item to retrieve.</param>
+        /// <returns>
+        /// The container for the item at the specified index within the item collection, if the
+        /// item is realized; otherwise, null.
+        /// </returns>
+        protected internal abstract Control? ContainerFromIndex(int index);
+
+        /// <summary>
+        /// Returns the index to the item that has the specified realized container.
+        /// </summary>
+        /// <param name="container">The generated container to retrieve the item index for.</param>
+        /// <returns>
+        /// The index to the item that corresponds to the specified realized container, or -1 if 
+        /// <paramref name="container"/> is not found.
+        /// </returns>
+        protected internal abstract int IndexFromContainer(Control container);
+
         /// <summary>
         /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
         /// </summary>
@@ -51,8 +79,59 @@ namespace Avalonia.Controls
         {
         }
 
+        /// <summary>
+        /// Adds the specified <see cref="Control"/> to the <see cref="Panel.Children"/> collection
+        /// of a <see cref="VirtualizingPanel"/> element.
+        /// </summary>
+        /// <param name="control">The control to add to the collection.</param>
+        protected void AddInternalChild(Control control)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.AddLogicalChild(control);
+            Children.Add(control);
+        }
+
+        /// <summary>
+        /// Adds the specified <see cref="Control"/> to the <see cref="Panel.Children"/> collection
+        /// of a <see cref="VirtualizingPanel"/> element at the specified index position.
+        /// </summary>
+        /// <param name="index">
+        /// The index position within the collection at which the child element is inserted.
+        /// </param>
+        /// <param name="control">The control to add to the collection.</param>
+        protected void InsertInternalChild(int index, Control control)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.AddLogicalChild(control);
+            Children.Insert(index, control);
+        }
+
+        /// <summary>
+        /// Removes child elements from the <see cref="Panel.Children"/> collection.
+        /// </summary>
+        /// <param name="index">
+        /// The beginning index position within the collection at which the first child element is
+        /// removed.
+        /// </param>
+        /// <param name="count">The number of child elements to remove.</param>
+        protected void RemoveInternalChildRange(int index, int count)
+        {
+            var itemsControl = EnsureItemsControl();
+            
+            for (var i = 0; i < count; ++i)
+            {
+                var c = Children[i];
+                itemsControl.RemoveLogicalChild(c);
+            }
+
+            Children.RemoveRange(index, count);
+        }
+
         internal void Attach(ItemsControl itemsControl)
         {
+            if (ItemsControl is not null)
+                throw new InvalidOperationException("The VirtualizingPanel is already attached to an ItemsControl");
+
             ItemsControl = itemsControl;
             ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
 
@@ -62,18 +141,24 @@ namespace Avalonia.Controls
 
         internal void Detach()
         {
-            if (ItemsControl is null)
-                return;
+            var itemsControl = EnsureItemsControl();
 
-            ItemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
+            itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
 
-            if (ItemsControl.Items is INotifyCollectionChanged incc)
+            if (itemsControl.Items is INotifyCollectionChanged incc)
                 incc.CollectionChanged -= OnItemsControlItemsChanged;
 
             ItemsControl = null;
             Children.Clear();
         }
 
+        private ItemsControl EnsureItemsControl()
+        {
+            if (ItemsControl is null)
+                ThrowNotAttached();
+            return ItemsControl;
+        }
+
         private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == ItemsControl.ItemsProperty)
@@ -91,5 +176,11 @@ namespace Avalonia.Controls
             if (_itemsControl?.Items is IList items)
                 OnItemsChanged(items, e);
         }
+
+        [DoesNotReturn]
+        private static void ThrowNotAttached()
+        {
+            throw new InvalidOperationException("The VirtualizingPanel does not belong to an ItemsControl.");
+        }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 5d9b3b56b1..a4e287dc08 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,6 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Xml.Linq;
 using Avalonia.Controls.Utils;
 using Avalonia.Layout;
 using Avalonia.Utilities;
@@ -18,16 +19,21 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<Orientation> OrientationProperty =
             StackLayout.OrientationProperty.AddOwner<VirtualizingStackPanel>();
 
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, bool>("ItemIsOwnContainer");
+
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
         private readonly Action<Control, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
+        private bool _isInLayout;
         private bool _isWaitingForViewportUpdate;
         private double _lastEstimatedElementSizeU = 25;
         private RealizedElementList? _measureElements;
         private RealizedElementList? _realizedElements;
         private Rect _viewport = s_invalidViewport;
+        private Stack<Control>? _recyclePool;
 
         public VirtualizingStackPanel()
         {
@@ -54,73 +60,92 @@ namespace Avalonia.Controls
             if (!IsEffectivelyVisible)
                 return default;
 
-            var items = ItemsControl?.Items as IList;
+            _isInLayout = true;
 
-            if (items is null || items.Count == 0)
+            try
             {
-                Children.Clear();
-                return default;
-            }
+                var items = ItemsControl?.Items as IList;
+
+                if (items is null || items.Count == 0)
+                {
+                    RemoveInternalChildRange(0, Children.Count);
+                    return default;
+                }
 
-            var orientation = Orientation;
+                var orientation = Orientation;
 
-            _realizedElements ??= new();
-            _measureElements ??= new();
+                _realizedElements ??= new();
+                _measureElements ??= new();
 
-            // If we're bringing an item into view, ignore any layout passes until we receive a new
-            // effective viewport.
-            if (_isWaitingForViewportUpdate)
-            {
-                var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
-                return CalculateDesiredSize(orientation, items, sizeV);
-            }
+                // If we're bringing an item into view, ignore any layout passes until we receive a new
+                // effective viewport.
+                if (_isWaitingForViewportUpdate)
+                {
+                    var sizeV = orientation == Orientation.Horizontal ? DesiredSize.Height : DesiredSize.Width;
+                    return CalculateDesiredSize(orientation, items, sizeV);
+                }
 
-            // We handle horizontal and vertical layouts here so X and Y are abstracted to:
-            // - Horizontal layouts: U = horizontal, V = vertical
-            // - Vertical layouts: U = vertical, V = horizontal
-            var viewport = CalculateMeasureViewport(items);
+                // We handle horizontal and vertical layouts here so X and Y are abstracted to:
+                // - Horizontal layouts: U = horizontal, V = vertical
+                // - Vertical layouts: U = vertical, V = horizontal
+                var viewport = CalculateMeasureViewport(items);
 
-            // Recycle elements outside of the expected range.
-            _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-            _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+                // Recycle elements outside of the expected range.
+                _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
 
-            // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
-            // write to _realizedElements yet, only _measureElements.
-            GenerateElements(availableSize, ref viewport);
+                // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
+                // write to _realizedElements yet, only _measureElements.
+                GenerateElements(availableSize, ref viewport);
 
-            // Now we know what definitely fits, recycle anything left over.
-            _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+                // Now we know what definitely fits, recycle anything left over.
+                _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
 
-            // And swap the measureElements and realizedElements collection.
-            (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
-            _measureElements.ResetForReuse();
+                // And swap the measureElements and realizedElements collection.
+                (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
+                _measureElements.ResetForReuse();
 
-            return CalculateDesiredSize(orientation, items, viewport.measuredV);
+                return CalculateDesiredSize(orientation, items, viewport.measuredV);
+            }
+            finally
+            {
+                _isInLayout = false;
+            }
         }
 
         protected override Size ArrangeOverride(Size finalSize)
         {
-            Debug.Assert(_realizedElements is not null);
+            if (_realizedElements is null)
+                return default;
 
-            var orientation = Orientation;
-            var u = _realizedElements!.StartU;
+            _isInLayout = true;
 
-            for (var i = 0; i < _realizedElements.Count; ++i)
+            try
             {
-                var e = _realizedElements.Elements[i];
+                var orientation = Orientation;
+                var u = _realizedElements!.StartU;
 
-                if (e is object)
+                for (var i = 0; i < _realizedElements.Count; ++i)
                 {
-                    var sizeU = _realizedElements.SizeU[i];
-                    var rect = orientation == Orientation.Horizontal ?
-                        new Rect(u, 0, sizeU, finalSize.Height) :
-                        new Rect(0, u, finalSize.Width, sizeU);
-                    e.Arrange(rect);
-                    u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                    var e = _realizedElements.Elements[i];
+
+                    if (e is object)
+                    {
+                        var sizeU = _realizedElements.SizeU[i];
+                        var rect = orientation == Orientation.Horizontal ?
+                            new Rect(u, 0, sizeU, finalSize.Height) :
+                            new Rect(0, u, finalSize.Width, sizeU);
+                        e.Arrange(rect);
+                        u += orientation == Orientation.Horizontal ? rect.Width : rect.Height;
+                    }
                 }
-            }
 
-            return finalSize;
+                return finalSize;
+            }
+            finally
+            {
+                _isInLayout = false;
+            }
         }
 
         protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
@@ -132,20 +157,70 @@ namespace Avalonia.Controls
             {
                 case NotifyCollectionChangedAction.Add:
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
-                    ItemsControl!.ItemContainerGenerator.InsertSpace(e.NewStartingIndex, e.NewItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Remove:
                     _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
-                    ItemsControl!.ItemContainerGenerator.RemoveRange(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    ////RecycleAllElements();
+                    _realizedElements.RecycleAllElements(_recycleElement);
                     break;
             }
 
             InvalidateMeasure();
         }
 
+        protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
+        protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
+
+        protected internal override void ScrollIntoView(int index)
+        {
+            var items = ItemsControl?.Items as IList;
+
+            if (_isInLayout || items is null || index < 0 || index >= items.Count)
+                return;
+
+            if (GetRealizedElement(index) is Control element)
+            {
+                element.BringIntoView();
+            }
+            else if (this.GetVisualRoot() is ILayoutRoot root)
+            {
+                // Create and measure the element to be brought into view. Store it in a field so that
+                // it can be re-used in the layout pass.
+                _anchorElement = GetOrCreateElement(items, index);
+                _anchorElement.Measure(Size.Infinity);
+                _anchorIndex = index;
+
+                // Get the expected position of the elment and put it in place.
+                var anchorU = GetOrEstimateElementPosition(index);
+                var rect = Orientation == Orientation.Horizontal ?
+                    new Rect(anchorU, 0, _anchorElement.DesiredSize.Width, _anchorElement.DesiredSize.Height) :
+                    new Rect(0, anchorU, _anchorElement.DesiredSize.Width, _anchorElement.DesiredSize.Height);
+                _anchorElement.Arrange(rect);
+
+                // If the item being brought into view was added since the last layout pass then
+                // our bounds won't be updated, so any containing scroll viewers will not have an
+                // updated extent. Do a layout pass to ensure that the containing scroll viewers
+                // will be able to scroll the new item into view.
+                if (!Bounds.Contains(rect) && !_viewport.Contains(rect))
+                {
+                    _isWaitingForViewportUpdate = true;
+                    root.LayoutManager.ExecuteLayoutPass();
+                    _isWaitingForViewportUpdate = false;
+                }
+
+                // Try to bring the item into view and do a layout pass.
+                _anchorElement.BringIntoView();
+
+                _isWaitingForViewportUpdate = !_viewport.Contains(rect);
+                root.LayoutManager.ExecuteLayoutPass();
+                _isWaitingForViewportUpdate = false;
+
+                _anchorElement = null;
+                _anchorIndex = -1;
+            }
+        }
+
         internal IReadOnlyList<Control?> GetRealizedElements()
         {
             return _realizedElements?.Elements ?? Array.Empty<Control>();
@@ -206,7 +281,10 @@ namespace Avalonia.Controls
 
         private double EstimateElementSizeU()
         {
-            var count = _realizedElements!.Count;
+            if (_realizedElements is null)
+                return _lastEstimatedElementSizeU;
+
+            var count = _realizedElements.Count;
             var divisor = 0.0;
             var total = 0.0;
 
@@ -280,36 +358,89 @@ namespace Avalonia.Controls
 
         private Control GetOrCreateElement(IList items, int index)
         {
-            var e = GetRealizedElement(index) ?? GetRecycledOrCreateElement(items, index);
+            var e = GetRealizedElement(index) ?? 
+                GetRecycledElement(items, index) ??
+                CreateElement(items, index);
             InvalidateHack(e);
             return e;
         }
 
         private Control? GetRealizedElement(int index)
         {
-            Debug.Assert(_realizedElements is not null);
-
             if (_anchorIndex == index)
                 return _anchorElement;
-            return _realizedElements!.GetElement(index);
+            return _realizedElements?.GetElement(index);
         }
 
-        private Control GetRecycledOrCreateElement(IList items, int index)
+        private Control? GetRecycledElement(IList items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
-            var c = ItemsControl!.ItemContainerGenerator.Materialize(index, items[index]!).ContainerControl;
-            Children.Add(c);
-            return c;
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+            if (item is Control controlItem)
+            {
+                if (controlItem.IsSet(ItemIsOwnContainerProperty))
+                {
+                    controlItem.IsVisible = true;
+                    return controlItem;
+                }
+                else if (generator.IsItemItsOwnContainer(controlItem))
+                {
+                    generator.PrepareItemContainer(controlItem, item, index);
+                    controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    AddInternalChild(controlItem);
+                    return controlItem;
+                }
+            }
+
+            if (_recyclePool?.Count > 0)
+            {
+                var recycled = _recyclePool.Pop();
+                recycled.IsVisible = true;
+                generator.PrepareItemContainer(recycled, item, index);
+                return recycled;
+            }
+
+            return null;
         }
 
-        private void RecycleElement(Control element)
+        private Control CreateElement(IList items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
-            var index = ItemsControl.ItemContainerGenerator!.IndexFromContainer(element);
-            ItemsControl!.ItemContainerGenerator.Dematerialize(index, 1);
-            Children.Remove(element);
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+            var container = generator.CreateContainer();
+
+            AddInternalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+
+            return container;
+        }
+
+        private double GetOrEstimateElementPosition(int index)
+        {
+            var estimatedElementSize = EstimateElementSizeU();
+            return index * estimatedElementSize;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+            
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                element.IsVisible = false;
+            }
+            else
+            {
+                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+            }
         }
 
         private void UpdateElementIndex(Control element, int index)
@@ -478,6 +609,43 @@ namespace Avalonia.Controls
                 return (-1, 0);
             }
 
+            /// <summary>
+            /// Gets the position of an element on the primary axis, if realized.
+            /// </summary>
+            /// <param name="modelIndex">The index in the source collection of the element.</param>
+            /// <param name="position">
+            /// When the method exits, contains the element's position on the primary axis, if 
+            /// the element is realized.
+            /// </param>
+            /// <returns>
+            /// True if the requested element was found, otherwise false.
+            /// </returns>
+            public bool TryGetElementU(int modelIndex, out double position)
+            {
+                if (_sizes is null || modelIndex < FirstModelIndex || modelIndex > LastModelIndex)
+                {
+                    position = double.NaN;
+                    return false;
+                }
+
+                var index = modelIndex - FirstModelIndex;
+                position = StartU;
+
+                for (var i = 0; i < index; ++i)
+                {
+                    position += _sizes[i];
+                }
+
+                return true;
+            }
+
+            /// <summary>
+            /// Gets the model index of the specified element.
+            /// </summary>
+            /// <param name="element">The element.</param>
+            /// <returns>The model index or -1 if the element is not present in the collection.</returns>
+            public int GetIndex(Control element) => _elements?.IndexOf(element) is int index && index >= 0 ? index : -1;
+
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.
             /// </summary>
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
index 587898ac6e..d8feb579f0 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
@@ -21,7 +21,7 @@ namespace Avalonia.Diagnostics.Views
         {
             InitializeComponent();
             _tree = this.GetControl<TreeView>("tree");
-            _tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
+            ////_tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
 
             _adorner = new Panel
             {
@@ -103,11 +103,11 @@ namespace Avalonia.Diagnostics.Views
             AvaloniaXamlLoader.Load(this);
         }
 
-        private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
-        {
-            var item = (TreeViewItem)e.Containers[0].ContainerControl;
-            item.TemplateApplied += TreeViewItemTemplateApplied;
-        }
+        ////private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
+        ////{
+        ////    var item = (TreeViewItem)e.Containers[0].ContainerControl;
+        ////    item.TemplateApplied += TreeViewItemTemplateApplied;
+        ////}
 
         private void TreeViewItemTemplateApplied(object? sender, TemplateAppliedEventArgs e)
         {
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index 1d9e5df74a..ddf471e513 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -1,341 +1,341 @@
-using System.Collections.ObjectModel;
-using System.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.UnitTests;
-using Avalonia.VisualTree;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class CarouselTests
-    {
-        [Fact]
-        public void First_Item_Should_Be_Selected_By_Default()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[]
-                {
-                    "Foo",
-                    "Bar"
-                }
-            };
-
-            target.ApplyTemplate();
-
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Equal("Foo", target.SelectedItem);
-        }
-
-        [Fact]
-        public void LogicalChild_Should_Be_Selected_Item()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[]
-                {
-                    "Foo",
-                    "Bar"
-                }
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.GetLogicalChildren());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Foo", child.Text);
-        }
-
-        [Fact]
-        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
-        {
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = new[] { "foo", "bar" },
-                IsVirtualized = true,
-                SelectedIndex = 0,
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.ItemContainerGenerator.Containers);
-            target.SelectedIndex = 1;
-            Assert.Single(target.ItemContainerGenerator.Containers);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Foo", child.Text);
-
-            var newItems = items.ToList();
-            newItems.RemoveAt(0);
-
-            target.Items = newItems;
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Bar", child.Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = true,
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Single(target.GetLogicalChildren());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Foo", child.Text);
-
-            var newItems = items.ToList();
-            newItems.RemoveAt(0);
-
-            target.Items = newItems;
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-            Assert.Equal("Bar", child.Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
-        {
-            var items = new ObservableCollection<string>();
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
+////using System.Collections.ObjectModel;
+////using System.Linq;
+////using System.Reactive.Subjects;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Data;
+////using Avalonia.LogicalTree;
+////using Avalonia.UnitTests;
+////using Avalonia.VisualTree;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class CarouselTests
+////    {
+////        [Fact]
+////        public void First_Item_Should_Be_Selected_By_Default()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[]
+////                {
+////                    "Foo",
+////                    "Bar"
+////                }
+////            };
+
+////            target.ApplyTemplate();
+
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Equal("Foo", target.SelectedItem);
+////        }
+
+////        [Fact]
+////        public void LogicalChild_Should_Be_Selected_Item()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[]
+////                {
+////                    "Foo",
+////                    "Bar"
+////                }
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.GetLogicalChildren());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Foo", child.Text);
+////        }
+
+////        [Fact]
+////        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
+////        {
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = new[] { "foo", "bar" },
+////                IsVirtualized = true,
+////                SelectedIndex = 0,
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.ItemContainerGenerator.Containers);
+////            target.SelectedIndex = 1;
+////            Assert.Single(target.ItemContainerGenerator.Containers);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            var newItems = items.ToList();
+////            newItems.RemoveAt(0);
+
+////            target.Items = newItems;
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Bar", child.Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = true,
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Single(target.GetLogicalChildren());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            var newItems = items.ToList();
+////            newItems.RemoveAt(0);
+
+////            target.Items = newItems;
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
+
+////            Assert.Equal("Bar", child.Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
+////        {
+////            var items = new ObservableCollection<string>();
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
 
-            Assert.Equal(-1, target.SelectedIndex);
-            Assert.Empty(target.GetLogicalChildren());
+////            Assert.Equal(-1, target.SelectedIndex);
+////            Assert.Empty(target.GetLogicalChildren());
 
-            items.Add("Foo");
+////            items.Add("Foo");
 
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Single(target.GetLogicalChildren());
-        }
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Single(target.GetLogicalChildren());
+////        }
 
-        [Fact]
-        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
+////        [Fact]
+////        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
 
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
 
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
 
-            Assert.Equal(3, target.GetLogicalChildren().Count());
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
 
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
 
-            Assert.Equal("Foo", child.Text);
+////            Assert.Equal("Foo", child.Text);
 
-            target.Items = null;
+////            target.Items = null;
 
-            var numChildren = target.GetLogicalChildren().Count();
+////            var numChildren = target.GetLogicalChildren().Count();
 
-            Assert.Equal(0, numChildren);
-            Assert.Equal(-1, target.SelectedIndex);
-        }
-
-        [Fact]
-        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false,
-                SelectedIndex = 2
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal("FooBar", target.SelectedItem);
-
-            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
-
-            Assert.IsType<TextBlock>(child);
-            Assert.Equal("FooBar", ((TextBlock)child).Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.Equal("Foo", child.Text);
-
-            items.RemoveAt(0);
-
-            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-            Assert.IsType<TextBlock>(child);
-            Assert.Equal("Bar", ((TextBlock)child).Text);
-        }
-
-        [Fact]
-        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
-        {
-            var items = new ObservableCollection<string>
-            {
-                "Foo",
-                "Bar",
-                "FooBar"
-            };
-
-            var target = new Carousel
-            {
-                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                Items = items,
-                IsVirtualized = false
-            };
-
-            target.ApplyTemplate();
-            ((Control)target.Presenter).ApplyTemplate();
-
-            target.SelectedIndex = 1;
-
-            items.RemoveAt(1);
-
-            Assert.Equal(0, target.SelectedIndex);
-            Assert.Equal("Foo", target.SelectedItem);
-        }
-
-        private Control CreateTemplate(Carousel control, INameScope scope)
-        {
-            return new CarouselPresenter
-            {
-                Name = "PART_ItemsPresenter",
-                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
-                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
-                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
-            }.RegisterInNameScope(scope);
-        }
-
-        private static TextBlock GetContainerTextBlock(object control)
-        {
-            var contentPresenter = Assert.IsType<ContentPresenter>(control);
-            contentPresenter.UpdateChild();
-            return Assert.IsType<TextBlock>(contentPresenter.Child);
-        }
-
-        [Fact]
-        public void SelectedItem_Validation()
-        {
-            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
-            {
-                var target = new Carousel
-                {
-                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-                    IsVirtualized = false
-                };
-
-                target.ApplyTemplate();
-                ((Control)target.Presenter).ApplyTemplate();
-
-                var exception = new System.InvalidCastException("failed validation");
-                var textObservable =
-                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
-                        BindingErrorType.DataValidationError));
-                target.Bind(ComboBox.SelectedItemProperty, textObservable);
-
-                Assert.True(DataValidationErrors.GetHasErrors(target));
-                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
-            }
-        }
-    }
-}
+////            Assert.Equal(0, numChildren);
+////            Assert.Equal(-1, target.SelectedIndex);
+////        }
+
+////        [Fact]
+////        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false,
+////                SelectedIndex = 2
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal("FooBar", target.SelectedItem);
+
+////            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
+
+////            Assert.IsType<TextBlock>(child);
+////            Assert.Equal("FooBar", ((TextBlock)child).Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            Assert.Equal(3, target.GetLogicalChildren().Count());
+
+////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.Equal("Foo", child.Text);
+
+////            items.RemoveAt(0);
+
+////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
+
+////            Assert.IsType<TextBlock>(child);
+////            Assert.Equal("Bar", ((TextBlock)child).Text);
+////        }
+
+////        [Fact]
+////        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
+////        {
+////            var items = new ObservableCollection<string>
+////            {
+////                "Foo",
+////                "Bar",
+////                "FooBar"
+////            };
+
+////            var target = new Carousel
+////            {
+////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                Items = items,
+////                IsVirtualized = false
+////            };
+
+////            target.ApplyTemplate();
+////            ((Control)target.Presenter).ApplyTemplate();
+
+////            target.SelectedIndex = 1;
+
+////            items.RemoveAt(1);
+
+////            Assert.Equal(0, target.SelectedIndex);
+////            Assert.Equal("Foo", target.SelectedItem);
+////        }
+
+////        private Control CreateTemplate(Carousel control, INameScope scope)
+////        {
+////            return new CarouselPresenter
+////            {
+////                Name = "PART_ItemsPresenter",
+////                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
+////                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
+////                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
+////                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
+////            }.RegisterInNameScope(scope);
+////        }
+
+////        private static TextBlock GetContainerTextBlock(object control)
+////        {
+////            var contentPresenter = Assert.IsType<ContentPresenter>(control);
+////            contentPresenter.UpdateChild();
+////            return Assert.IsType<TextBlock>(contentPresenter.Child);
+////        }
+
+////        [Fact]
+////        public void SelectedItem_Validation()
+////        {
+////            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
+////            {
+////                var target = new Carousel
+////                {
+////                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+////                    IsVirtualized = false
+////                };
+
+////                target.ApplyTemplate();
+////                ((Control)target.Presenter).ApplyTemplate();
+
+////                var exception = new System.InvalidCastException("failed validation");
+////                var textObservable =
+////                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
+////                        BindingErrorType.DataValidationError));
+////                target.Bind(ComboBox.SelectedItemProperty, textObservable);
+
+////                Assert.True(DataValidationErrors.GetHasErrors(target));
+////                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
+////            }
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs b/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
deleted file mode 100644
index 8a053c2a91..0000000000
--- a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTests.cs
+++ /dev/null
@@ -1,173 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using System.Reactive.Linq;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Data;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Generators
-{
-    public class ItemContainerGeneratorTests
-    {
-        [Fact]
-        public void Materialize_Should_Create_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-            var result = containers
-                .Select(x => x.ContainerControl)
-                .OfType<ContentPresenter>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(items, result);
-        }
-
-        [Fact]
-        public void ContainerFromIndex_Should_Return_Materialized_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Equal(containers[1].ContainerControl, target.ContainerFromIndex(1));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(2));
-        }
-
-        [Fact]
-        public void IndexFromContainer_Should_Return_Index()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            Assert.Equal(0, target.IndexFromContainer(containers[0].ContainerControl));
-            Assert.Equal(1, target.IndexFromContainer(containers[1].ContainerControl));
-            Assert.Equal(2, target.IndexFromContainer(containers[2].ContainerControl));
-        }
-
-        [Fact]
-        public void Dematerialize_Should_Remove_Container()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            target.Dematerialize(1, 1);
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Null(target.ContainerFromIndex(1));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(2));
-        }
-
-        [Fact]
-        public void Dematerialize_Should_Return_Removed_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-            var expected = target.Containers.Take(2).ToList();
-            var result = target.Dematerialize(0, 2);
-
-            Assert.Equal(expected, result);
-        }
-
-        [Fact]
-        public void InsertSpace_Should_Alter_Successive_Container_Indexes()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            target.InsertSpace(1, 3);
-
-            Assert.Equal(3, target.Containers.Count());
-            Assert.Equal(new[] { 0, 4, 5 }, target.Containers.Select(x => x.Index));
-        }
-
-        [Fact]
-        public void RemoveRange_Should_Alter_Successive_Container_Indexes()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var containers = Materialize(target, 0, items);
-
-            var removed = target.RemoveRange(1, 1).Single();
-
-            Assert.Equal(containers[0].ContainerControl, target.ContainerFromIndex(0));
-            Assert.Equal(containers[2].ContainerControl, target.ContainerFromIndex(1));
-            Assert.Equal(containers[1], removed);
-            Assert.Equal(new[] { 0, 1 }, target.Containers.Select(x => x.Index));
-        }
-
-        [Fact]
-        public void Style_Binding_Should_Be_Able_To_Override_Content()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator(owner);
-            var container = (ContentPresenter)target.Materialize(0, "foo").ContainerControl;
-
-            Assert.Equal("foo", container.Content);
-
-            container.Bind(
-                ContentPresenter.ContentProperty,
-                Observable.Never<object>().StartWith("bar"),
-                BindingPriority.Style);
-
-            Assert.Equal("bar", container.Content);
-        }
-
-        [Fact]
-        public void Style_Binding_Should_Be_Able_To_Override_Content_Typed()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var container = (ListBoxItem)target.Materialize(0, "foo").ContainerControl;
-
-            Assert.Equal("foo", container.Content);
-
-            container.Bind(
-                ContentPresenter.ContentProperty,
-                Observable.Never<object>().StartWith("bar"),
-                BindingPriority.Style);
-
-            Assert.Equal("bar", container.Content);
-        }
-
-        [Fact]
-        public void Materialize_Should_Create_Containers_When_Item_Is_Null()
-        {
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var container = (ListBoxItem)target.Materialize(0, null).ContainerControl;
-
-            Assert.True(container != null, "The containers is not materialized.");
-        }
-
-        private static IList<ItemContainerInfo> Materialize(
-            IItemContainerGenerator generator,
-            int index,
-            string[] items)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            foreach (var item in items)
-            {
-                var container = generator.Materialize(index++, item);
-                result.Add(container);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs b/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs
deleted file mode 100644
index f63a764a21..0000000000
--- a/tests/Avalonia.Controls.UnitTests/Generators/ItemContainerGeneratorTypedTests.cs
+++ /dev/null
@@ -1,42 +0,0 @@
-using System.Collections.Generic;
-using System.Linq;
-using Avalonia.Controls.Generators;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests.Generators
-{
-    public class ItemContainerGeneratorTypedTests
-    {
-        [Fact]
-        public void Materialize_Should_Create_Containers()
-        {
-            var items = new[] { "foo", "bar", "baz" };
-            var owner = new Decorator();
-            var target = new ItemContainerGenerator<ListBoxItem>(owner, ListBoxItem.ContentProperty, null);
-            var containers = Materialize(target, 0, items);
-            var result = containers
-                .Select(x => x.ContainerControl)
-                .OfType<ListBoxItem>()
-                .Select(x => x.Content)
-                .ToList();
-
-            Assert.Equal(items, result);
-        }
-
-        private static IList<ItemContainerInfo> Materialize(
-            IItemContainerGenerator generator,
-            int index,
-            string[] items)
-        {
-            var result = new List<ItemContainerInfo>();
-
-            foreach (var item in items)
-            {
-                var container = generator.Materialize(index++, item);
-                result.Add(container);
-            }
-
-            return result;
-        }
-    }
-}
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index ada5e10a7f..25d93746d5 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -1,3 +1,4 @@
+using System;
 using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.Linq;
@@ -367,12 +368,13 @@ namespace Avalonia.Controls.UnitTests
             target.ApplyTemplate();
             target.Presenter.ApplyTemplate();
 
-            Assert.Equal(2, target.ItemContainerGenerator.Containers.Count());
+            var panel = target.Presenter.Panel;
+            Assert.Equal(2, panel.Children.Count());
 
             target.Template = GetTemplate();
             target.ApplyTemplate();
 
-            Assert.Empty(target.ItemContainerGenerator.Containers);
+            Assert.Empty(panel.Children);
         }
 
         [Fact]
@@ -535,26 +537,6 @@ namespace Avalonia.Controls.UnitTests
             Assert.DoesNotContain(":singleitem", target.Classes);
         }
 
-        [Fact]
-        public void Setting_Presenter_Explicitly_Should_Set_Item_Parent()
-        {
-            var target = new TestItemsControl();
-            var child = new Control();
-
-            var presenter = new ItemsPresenter
-            {
-                [StyledElement.TemplatedParentProperty] = target,
-            };
-
-            presenter.ApplyTemplate();
-            target.Presenter = presenter;
-            target.Items = new[] { child };
-            target.ApplyTemplate();
-
-            Assert.Equal(target, child.Parent);
-            Assert.Equal(target, ((ILogical)child).LogicalParent);
-        }
-
         [Fact]
         public void DataContexts_Should_Be_Correctly_Set()
         {
@@ -683,36 +665,6 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
-        [Fact]
-        public void Presenter_Items_Should_Be_In_Sync()
-        {
-            var target = new ItemsControl
-            {
-                Template = GetTemplate(),
-                Items = new object[]
-                {
-                    new Button(),
-                    new Button(),
-                },
-            };
-
-            var root = new TestRoot { Child = target };
-            var otherPanel = new StackPanel();
-
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
-            
-            target.ItemContainerGenerator.Materialized += (s, e) =>
-            {
-                Assert.IsType<Canvas>(e.Containers[0].Item);
-            };
-
-            target.Items = new[]
-            {
-                new Canvas()
-            };
-        }
-
         [Fact]
         public void Detaching_Then_Reattaching_To_Logical_Tree_Twice_Does_Not_Throw()
         {
@@ -780,14 +732,5 @@ namespace Avalonia.Controls.UnitTests
                 };
             });
         }
-
-        private class TestItemsControl : ItemsControl
-        {
-            public new ItemsPresenter Presenter
-            {
-                get { return base.Presenter; }
-                set { base.Presenter = value; }
-            }
-        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index 280f140a79..cc824876ac 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -8,6 +8,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Input;
+using Avalonia.Layout;
 using Avalonia.LogicalTree;
 using Avalonia.Styling;
 using Avalonia.UnitTests;
@@ -218,6 +219,7 @@ namespace Avalonia.Controls.UnitTests
 
                 // Scroll down a page.
                 target.Scroll.Offset = new Vector(0, 10);
+                Layout(target);
 
                 // Make sure recycled item isn't now selected.
                 Assert.False(((ListBoxItem)target.Presenter.Panel.Children[0]).IsSelected);
@@ -239,8 +241,8 @@ namespace Avalonia.Controls.UnitTests
 
                 Prepare(target);
 
-                Assert.Equal(new Size(20, 20), target.Scroll.Extent);
-                Assert.Equal(new Size(100, 10), target.Scroll.Viewport);
+                Assert.Equal(new Size(100, 200), target.Scroll.Extent);
+                Assert.Equal(new Size(100, 100), target.Scroll.Viewport);
             }
         }
 
@@ -263,11 +265,13 @@ namespace Avalonia.Controls.UnitTests
 
                 items.Clear();
                 items.AddRange(Enumerable.Range(0, 11).Select(x => $"Item {x}"));
+                Layout(target);
+
                 items.Remove("Item 2");
+                Layout(target);
 
-                Assert.Equal(
-                    items,
-                    target.Presenter.Panel.Children.Cast<ListBoxItem>().Select(x => (string)x.Content));
+                var actual = target.Presenter.Panel.Children.Cast<ListBoxItem>().Select(x => (string)x.Content).ToList();
+                Assert.Equal(items.OrderBy(x => x), actual.OrderBy(x => x));
             }
         }
 
@@ -328,44 +332,6 @@ namespace Avalonia.Controls.UnitTests
             _mouse.Click(listBox, item, mouseButton);
         }
 
-        [Fact]
-        public void ListBox_After_Scroll_IndexOutOfRangeException_Shouldnt_Be_Thrown()
-        {
-            throw new NotImplementedException();
-            ////using (UnitTestApplication.Start(TestServices.StyledWindow))
-            ////{
-            ////    var items = Enumerable.Range(0, 11).Select(x => $"{x}").ToArray();
-
-            ////    var target = new ListBox
-            ////    {
-            ////        Template = ListBoxTemplate(),
-            ////        Items = items,
-            ////        ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 11 })
-            ////    };
-
-            ////    Prepare(target);
-
-            ////    var panel = target.Presenter.Panel as IVirtualizingPanel;
-
-            ////    var listBoxItems = panel.Children.OfType<ListBoxItem>();
-
-            ////    //virtualization should have created exactly 10 items
-            ////    Assert.Equal(10, listBoxItems.Count());
-            ////    Assert.Equal("0", listBoxItems.First().DataContext);
-            ////    Assert.Equal("9", listBoxItems.Last().DataContext);
-
-            ////    //instead pixeloffset > 0 there could be pretty complex sequence for repro
-            ////    //it involves add/remove/scroll to end multiple actions
-            ////    //which i can't find so far :(, but this is the simplest way to add it to unit test
-            ////    panel.PixelOffset = 1;
-
-            ////    //here scroll to end -> IndexOutOfRangeException is thrown
-            ////    target.Scroll.Offset = new Vector(0, 2);
-
-            ////    Assert.True(true);
-            ////}
-        }
-
         [Fact]
         public void LayoutManager_Should_Measure_Arrange_All()
         {
@@ -464,11 +430,11 @@ namespace Avalonia.Controls.UnitTests
                 items.Remove("1");
                 lm.ExecuteLayoutPass();
 
-                Assert.Equal("30", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 1).DataContext);
-                Assert.Equal("29", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 2).DataContext);
-                Assert.Equal("28", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 3).DataContext);
-                Assert.Equal("27", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 4).DataContext);
-                Assert.Equal("26", target.ItemContainerGenerator.ContainerFromIndex(items.Count - 5).DataContext);
+                Assert.Equal("30", target.ContainerFromIndex(items.Count - 1).DataContext);
+                Assert.Equal("29", target.ContainerFromIndex(items.Count - 2).DataContext);
+                Assert.Equal("28", target.ContainerFromIndex(items.Count - 3).DataContext);
+                Assert.Equal("27", target.ContainerFromIndex(items.Count - 4).DataContext);
+                Assert.Equal("26", target.ContainerFromIndex(items.Count - 5).DataContext);
             }
         }
 
@@ -525,7 +491,7 @@ namespace Avalonia.Controls.UnitTests
 
                 var target = new ListBox()
                 {
-                    VerticalAlignment = Layout.VerticalAlignment.Top,
+                    VerticalAlignment = VerticalAlignment.Top,
                     AutoScrollToSelectedItem = true,
                     Width = 50,
                     ItemTemplate = new FuncDataTemplate<object>((c, _) => new Border() { Height = 10 }),
@@ -627,6 +593,8 @@ namespace Avalonia.Controls.UnitTests
                             [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
                             [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
                             [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
                         }.RegisterInNameScope(scope),
                         new ScrollBar
                         {
@@ -640,45 +608,28 @@ namespace Avalonia.Controls.UnitTests
 
         private static void Prepare(ListBox target)
         {
-            // The ListBox needs to be part of a rooted visual tree.
-            var root = new TestRoot();
-            root.Child = target;
-
-            // Apply the template to the ListBox itself.
-            target.ApplyTemplate();
+            target.Width = target.Height = 100;
 
-            // Then to its inner ScrollViewer.
-            var scrollViewer = (ScrollViewer)target.GetVisualChildren().Single();
-            scrollViewer.ApplyTemplate();
-
-            // Then make the ScrollViewer create its child.
-            ((ContentPresenter)scrollViewer.Presenter).UpdateChild();
-
-            // Now the ItemsPresenter should be reigstered, so apply its template.
-            target.Presenter.ApplyTemplate();
-
-            // Because ListBox items are virtualized we need to do a layout to make them appear.
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
-
-            // Now set and apply the item templates.
-            foreach (ListBoxItem item in target.Presenter.Panel.Children)
+            var root = new TestRoot(target)
             {
-                item.Template = ListBoxItemTemplate();
-                item.ApplyTemplate();
-                item.Presenter.ApplyTemplate();
-                ((ContentPresenter)item.Presenter).UpdateChild();
-            }
+                Resources =
+                {
+                    { 
+                        typeof(ListBoxItem),
+                        new ControlTheme(typeof(ListBoxItem))
+                        {
+                            Setters = { new Setter(ListBoxItem.TemplateProperty, ListBoxItemTemplate()) }
+                        }
+                    }
+                }
+            };
 
-            // The items were created before the template was applied, so now we need to go back
-            // and re-arrange everything.
-            foreach (Control i in target.GetSelfAndVisualDescendants())
-            {
-                i.InvalidateMeasure();
-            }
+            root.LayoutManager.ExecuteInitialLayoutPass();
+        }
 
-            target.Measure(new Size(100, 100));
-            target.Arrange(new Rect(0, 0, 100, 100));
+        private static void Layout(Control c)
+        {
+            ((ILayoutRoot)c.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
         }
 
         private class Item
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 8be1e112e7..8ded57956b 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1,1475 +1,1475 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using System.ComponentModel;
-using System.Linq;
-using System.Runtime.CompilerServices;
-using Avalonia.Collections;
-using Avalonia.Controls.Generators;
-using Avalonia.Controls.Presenters;
-using Avalonia.Controls.Templates;
-using Avalonia.Data;
-using Avalonia.Data.Core;
-using Avalonia.Input;
-using Avalonia.Input.Platform;
-using Avalonia.Interactivity;
-using Avalonia.LogicalTree;
-using Avalonia.Styling;
-using Avalonia.UnitTests;
-using JetBrains.Annotations;
-using Moq;
-using Xunit;
-
-namespace Avalonia.Controls.UnitTests
-{
-    public class TreeViewTests
-    {
-        MouseTestHelper _mouse = new MouseTestHelper();
-
-        [Fact]
-        public void Items_Should_Be_Created()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-        }
-
-        [Fact]
-        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
-        {
-            TreeView target;
-
-            var root = new TestRoot
-            {
-                Child = target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
-                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-                        (_, __) => new Canvas(),
-                        x => x.Children),
-                }
-            };
-
-            ApplyTemplates(target);
-
-            var items = target.ItemContainerGenerator.Index.Containers
-                .OfType<TreeViewItem>()
-                .ToList();
-
-            Assert.Equal(5, items.Count);
-            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
-        }
-
-        [Fact]
-        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
-        {
-            TreeView target;
-            var theme = new ControlTheme(typeof(TreeViewItem));
-
-            var root = new TestRoot
-            {
-                Child = target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = CreateTestTreeData(),
-                    ItemContainerTheme = theme,
-                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-                        (_, __) => new Canvas(),
-                        x => x.Children),
-                }
-            };
-
-            ApplyTemplates(target);
-
-            var items = target.ItemContainerGenerator.Index.Containers
-                .OfType<TreeViewItem>()
-                .ToList();
-
-            Assert.Equal(5, items.Count);
-            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
-        }
-
-        [Fact]
-        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = CreateTestTreeData(),
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
-            var header = (TextBlock)container.Header;
-            Assert.Equal("Root", header.Text);
-        }
-
-        [Fact]
-        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
-            // to be called, which requires an IStyleRoot.
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
-                tree[0].Children[1].Children[0]);
-
-            Assert.NotNull(container);
-
-            var header = ((TreeViewItem)container).Header;
-            var headerContent = ((TextBlock)header).Text;
-
-            Assert.Equal("Grandchild2a", headerContent);
-        }
-
-        [Fact]
-        public void Clicking_Item_Should_Select_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                _mouse.Click(container);
-
-                Assert.Equal(item, target.SelectedItem);
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                target.SelectedItem = item;
-
-                Assert.True(container.IsSelected);
-
-                _mouse.Click(container, modifiers: KeyModifiers.Control);
-
-                Assert.Null(target.SelectedItem);
-                Assert.False(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree
-                };
+////using System;
+////using System.Collections;
+////using System.Collections.Generic;
+////using System.Collections.ObjectModel;
+////using System.ComponentModel;
+////using System.Linq;
+////using System.Runtime.CompilerServices;
+////using Avalonia.Collections;
+////using Avalonia.Controls.Generators;
+////using Avalonia.Controls.Presenters;
+////using Avalonia.Controls.Templates;
+////using Avalonia.Data;
+////using Avalonia.Data.Core;
+////using Avalonia.Input;
+////using Avalonia.Input.Platform;
+////using Avalonia.Interactivity;
+////using Avalonia.LogicalTree;
+////using Avalonia.Styling;
+////using Avalonia.UnitTests;
+////using JetBrains.Annotations;
+////using Moq;
+////using Xunit;
+
+////namespace Avalonia.Controls.UnitTests
+////{
+////    public class TreeViewTests
+////    {
+////        MouseTestHelper _mouse = new MouseTestHelper();
+
+////        [Fact]
+////        public void Items_Should_Be_Created()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = CreateTestTreeData(),
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+////        }
+
+////        [Fact]
+////        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
+////        {
+////            TreeView target;
+
+////            var root = new TestRoot
+////            {
+////                Child = target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = CreateTestTreeData(),
+////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+////                        (_, __) => new Canvas(),
+////                        x => x.Children),
+////                }
+////            };
+
+////            ApplyTemplates(target);
+
+////            var items = target.ItemContainerGenerator.Index.Containers
+////                .OfType<TreeViewItem>()
+////                .ToList();
+
+////            Assert.Equal(5, items.Count);
+////            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
+////        }
+
+////        [Fact]
+////        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
+////        {
+////            TreeView target;
+////            var theme = new ControlTheme(typeof(TreeViewItem));
+
+////            var root = new TestRoot
+////            {
+////                Child = target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = CreateTestTreeData(),
+////                    ItemContainerTheme = theme,
+////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+////                        (_, __) => new Canvas(),
+////                        x => x.Children),
+////                }
+////            };
+
+////            ApplyTemplates(target);
+
+////            var items = target.ItemContainerGenerator.Index.Containers
+////                .OfType<TreeViewItem>()
+////                .ToList();
+
+////            Assert.Equal(5, items.Count);
+////            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
+////        }
+
+////        [Fact]
+////        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = CreateTestTreeData(),
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
+////            var header = (TextBlock)container.Header;
+////            Assert.Equal("Root", header.Text);
+////        }
+
+////        [Fact]
+////        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
+////            // to be called, which requires an IStyleRoot.
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
+////                tree[0].Children[1].Children[0]);
+
+////            Assert.NotNull(container);
+
+////            var header = ((TreeViewItem)container).Header;
+////            var headerContent = ((TextBlock)header).Text;
+
+////            Assert.Equal("Grandchild2a", headerContent);
+////        }
+
+////        [Fact]
+////        public void Clicking_Item_Should_Select_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                _mouse.Click(container);
+
+////                Assert.Equal(item, target.SelectedItem);
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                target.SelectedItem = item;
+
+////                Assert.True(container.IsSelected);
+
+////                _mouse.Click(container, modifiers: KeyModifiers.Control);
+
+////                Assert.Null(target.SelectedItem);
+////                Assert.False(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var item1 = tree[0].Children[1].Children[0];
-                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+////                var item1 = tree[0].Children[1].Children[0];
+////                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
 
-                var item2 = tree[0].Children[1];
-                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+////                var item2 = tree[0].Children[1];
+////                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
 
-                Assert.NotNull(container1);
-                Assert.NotNull(container2);
-
-                target.SelectedItem = item1;
-
-                Assert.True(container1.IsSelected);
-
-                _mouse.Click(container2, modifiers: KeyModifiers.Control);
-
-                Assert.Equal(item2, target.SelectedItem);
-                Assert.False(container1.IsSelected);
-                Assert.True(container2.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
+////                Assert.NotNull(container1);
+////                Assert.NotNull(container2);
+
+////                target.SelectedItem = item1;
+
+////                Assert.True(container1.IsSelected);
+
+////                _mouse.Click(container2, modifiers: KeyModifiers.Control);
+
+////                Assert.Equal(item2, target.SelectedItem);
+////                Assert.False(container1.IsSelected);
+////                Assert.True(container2.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
-
-                var item1 = rootNode.Children[0];
-                var item2 = rootNode.Children.Last();
-
-                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
-                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
-
-                ClickContainer(item1Container, KeyModifiers.Control);
-                Assert.True(item1Container.IsSelected);
-
-                ClickContainer(item2Container, KeyModifiers.Control);
-                Assert.True(item2Container.IsSelected);
+////                var rootNode = tree[0];
+
+////                var item1 = rootNode.Children[0];
+////                var item2 = rootNode.Children.Last();
+
+////                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+////                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+
+////                ClickContainer(item1Container, KeyModifiers.Control);
+////                Assert.True(item1Container.IsSelected);
+
+////                ClickContainer(item2Container, KeyModifiers.Control);
+////                Assert.True(item2Container.IsSelected);
 
-                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
+////                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
 
-                ClickContainer(item1Container, KeyModifiers.Control);
-                Assert.False(item1Container.IsSelected);
+////                ClickContainer(item1Container, KeyModifiers.Control);
+////                Assert.False(item1Container.IsSelected);
 
-                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
-            }
-        }
+////                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
+////        [Fact]
+////        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
 
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
 
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
+////                var rootNode = tree[0];
 
-                var from = rootNode.Children[0];
-                var to = rootNode.Children.Last();
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children.Last();
 
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
 
-                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(fromContainer, KeyModifiers.None);
 
-                Assert.True(fromContainer.IsSelected);
+////                Assert.True(fromContainer.IsSelected);
 
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
+////        [Fact]
+////        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
 
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
 
-                Assert.True(fromContainer.IsSelected);
+////                Assert.True(fromContainer.IsSelected);
 
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
 
-        [Fact]
-        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-
-                ClickContainer(toContainer, KeyModifiers.Shift);
-                AssertChildrenSelected(target, rootNode);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-
-                Assert.True(fromContainer.IsSelected);
-
-                foreach (var child in rootNode.Children)
-                {
-                    if (child == from)
-                    {
-                        continue;
-                    }
-
-                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-                    Assert.False(container.IsSelected);
-                }
-            }
-        }
-
-        [Fact]
-        public void Setting_SelectedItem_Should_Set_Container_Selected()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-                Assert.NotNull(container);
-
-                target.SelectedItem = item;
-
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        [Fact]
-        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = tree[0].Children[1].Children[0];
-
-                var called = false;
-                target.SelectionChanged += (s, e) =>
-                {
-                    Assert.Empty(e.RemovedItems);
-                    Assert.Equal(1, e.AddedItems.Count);
-                    Assert.Same(item, e.AddedItems[0]);
-                    called = true;
-                };
-
-                target.SelectedItem = item;
-                Assert.True(called);
-            }
-        }
-
-        [Fact]
-        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
-        {
-            using (Application())
-            {
-                var dataContext = new TestDataContext();
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    DataContext = dataContext
-                };
-
-                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
-                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-
-                var selectedValues = new List<object>();
-
-                dataContext.PropertyChanged += (_, e) =>
-                {
-                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
-                        selectedValues.Add(dataContext.SelectedItem);
-                };
-                selectedValues.Add(dataContext.SelectedItem);
-
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
-
-                Assert.Equal(3, selectedValues.Count);
-                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
-            }
-        }
-
-        [Fact]
-        public void LogicalChildren_Should_Be_Set()
-        {
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = new[] { "Foo", "Bar", "Baz " },
-            };
-
-            ApplyTemplates(target);
-
-            var result = target.GetLogicalChildren()
-                .OfType<TreeViewItem>()
-                .Select(x => x.Header)
-                .OfType<TextBlock>()
-                .Select(x => x.Text)
-                .ToList();
-
-            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
-        }
-
-        [Fact]
-        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-            tree[0].Children.RemoveAt(1);
-
-            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
-        }
-
-        [Fact]
-        public void DataContexts_Should_Be_Correctly_Set()
-        {
-            var items = new object[]
-            {
-                "Foo",
-                new Node { Value = "Bar" },
-                new TextBlock { Text = "Baz" },
-                new TreeViewItem { Header = "Qux" },
-            };
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                DataContext = "Base",
-                DataTemplates =
-                {
-                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
-                },
-                Items = items,
-            };
-
-            ApplyTemplates(target);
-
-            var dataContexts = target.Presenter.Panel.Children
-                .Cast<Control>()
-                .Select(x => x.DataContext)
-                .ToList();
-
-            Assert.Equal(
-                new object[] { items[0], items[1], "Base", "Base" },
-                dataContexts);
-        }
-
-        [Fact]
-        public void Control_Item_Should_Not_Be_NameScope()
-        {
-            var items = new object[]
-            {
-                new TreeViewItem(),
-            };
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = items,
-            };
-
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
-
-            var item = target.Presenter.Panel.LogicalChildren[0];
-            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
-        }
-
-        [Fact]
-        public void Should_React_To_Children_Changing()
-        {
-            var data = CreateTestTreeData();
-
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = data,
-            };
-
-            var root = new TestRoot(target);
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-
-            // Make sure that the binding to Node.Children does not get collected.
-            GC.Collect();
-
-            data[0].Children = new AvaloniaList<Node>
-            {
-                new Node
-                {
-                    Value = "NewChild1",
-                }
-            };
-
-            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
-        }
-
-        [Fact]
-        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
-        {
-            using (Application())
-            {
-                var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-                var data = CreateTestTreeData();
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = data,
-                };
-
-                var button = new Button();
-
-                var root = new TestRoot
-                {
-                    Child = new StackPanel
-                    {
-                        Children = { target, button },
-                    }
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = data[0].Children[0];
-                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-                Assert.NotNull(node);
-
-                target.SelectedItem = item;
-                node.Focus();
-                Assert.Same(node, focus.Current);
-
-                navigation.Move(focus.Current, NavigationDirection.Next);
-                Assert.Same(button, focus.Current);
-
-                navigation.Move(focus.Current, NavigationDirection.Next);
-                Assert.Same(node, focus.Current);
-            }
-        }
-
-        [Fact]
-        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
-        {
-            using (Application())
-            {
-                var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-                var data = CreateTestTreeData();
-
-                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
-
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = data,
-                    SelectedItem = selectedNode
-                };
-
-                var button = new Button();
-
-                var root = new TestRoot
-                {
-                    Child = new StackPanel
-                    {
-                        Children = { target, button },
-                    }
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var item = data[0].Children[0];
-                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-                Assert.NotNull(node);
-
-                target.SelectedItem = selectedNode;
-                node.Focus();
-                Assert.Same(node, focus.Current);
-
-                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
-        {
-            using (UnitTestApplication.Start())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children[0];
-                var to = rootNode.Children.Last();
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                ExpandAll(target);
-
-                var rootNode = tree[0];
-
-                var from = rootNode.Children.Last();
-                var to = rootNode.Children[0];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-                var selectAllGesture = keymap.SelectAll.First();
-
-                var keyEvent = new KeyEventArgs
-                {
-                    RoutedEvent = InputElement.KeyDownEvent,
-                    Key = selectAllGesture.Key,
-                    KeyModifiers = selectAllGesture.KeyModifiers
-                };
-
-                target.RaiseEvent(keyEvent);
-
-                AssertChildrenSelected(target, rootNode);
-            }
-        }
-
-        [Fact]
-        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
-        {
-            using (UnitTestApplication.Start())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-                target.SelectAll();
-
-                AssertChildrenSelected(target, tree[0]);
-                Assert.Equal(5, target.SelectedItems.Count);
-
-                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
-
-                Assert.Equal(5, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var to = rootNode.Children[0];
-                var then = rootNode.Children[1];
-
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
-
-                ClickContainer(fromContainer, KeyModifiers.None);
-                ClickContainer(toContainer, KeyModifiers.Shift);
-
-                Assert.Equal(2, target.SelectedItems.Count);
-
-                _mouse.Click(thenContainer, MouseButton.Right);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Shift_Right_Click_Should_Not_Select_Multiple()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var from = rootNode.Children[0];
-                var to = rootNode.Children[1];
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                _mouse.Click(fromContainer);
-                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
-        {
-            using (Application())
-            {
-                var tree = CreateTestTreeData();
-                var target = new TreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    Items = tree,
-                    SelectionMode = SelectionMode.Multiple,
-                };
-
-                var visualRoot = new TestRoot();
-                visualRoot.Child = target;
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-                var rootNode = tree[0];
-                var from = rootNode.Children[0];
-                var to = rootNode.Children[1];
-                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-                _mouse.Click(fromContainer);
-                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
-
-                Assert.Equal(1, target.SelectedItems.Count);
-            }
-        }
-
-        [Fact]
-        public void TreeViewItems_Level_Should_Be_Set()
-        {
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(0, GetItem(target, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 1).Level);
-            Assert.Equal(1, GetItem(target, 0, 2).Level);
-            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-        }
-
-        [Fact]
-        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
-        {
-            var tree = CreateTestTreeData();
-            var target = new DerivedTreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(0, GetItem(target, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 0).Level);
-            Assert.Equal(1, GetItem(target, 0, 1).Level);
-            Assert.Equal(1, GetItem(target, 0, 2).Level);
-            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-        }
-
-        [Fact]
-        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
-        {
-            // Issue #2985
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var visualRoot = new TestRoot();
-            visualRoot.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            var parent = tree[0];
-            var node = parent.Children[1];
-
-            parent.Children.Remove(node);
-            parent.Children.Add(node);
-
-            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
-            ApplyTemplates(new[] { item });
-
-            // #2985 causes ArgumentException here.
-            node.Children.Add(new Node());
-        }
-
-        [Fact]
-        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
-        {
-            // Issue #2980.
-            using (Application())
-            {
-                var target = new DerivedTreeView
-                {
-                    Template = CreateTreeViewTemplate(),
-                    SelectionMode = SelectionMode.Multiple,
-                    Items = new List<Node>
-                {
-                    new Node { Value = "Root1", },
-                    new Node { Value = "Root2", },
-                },
-                };
-
-                var visualRoot = new TestRoot
-                {
-                    Styles =
-                    {
-                        new Style(x => x.OfType<TreeViewItem>())
-                        {
-                            Setters =
-                            {
-                                new Setter(TreeViewItem.IsExpandedProperty, true),
-                            },
-                        },
-                    },
-                    Child = target,
-                };
-
-                CreateNodeDataTemplate(target);
-                ApplyTemplates(target);
-
-                _mouse.Click(GetItem(target, 0));
-                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
-            }
-        }
-
-        [Fact]
-        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
-        {
-            // Issue #3328
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-            ExpandAll(target);
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-            root.Child = null;
-
-            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-            Assert.Equal(1, target.Presenter.Panel.Children.Count);
-
-            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
-            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
-            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
-
-            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
-            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
-            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
-        }
-
-        [Fact]
-        public void Clearing_TreeView_Items_Clears_Index()
-        {
-            // Issue #3551
-            var tree = CreateTestTreeData();
-            var target = new TreeView
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            var root = new TestRoot();
-            root.Child = target;
-
-            CreateNodeDataTemplate(target);
-            ApplyTemplates(target);
-
-            var rootNode = tree[0];
-            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-
-            Assert.NotNull(container);
-
-            root.Child = null;
-
-            tree.Clear();
-
-            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
-        }
-
-        [Fact]
-        public void Can_Use_Derived_TreeViewItem()
-        {
-            var tree = CreateTestTreeData();
-            var target = new DerivedTreeViewWithDerivedTreeViewItems
-            {
-                Template = CreateTreeViewTemplate(),
-                Items = tree,
-            };
-
-            ApplyTemplates(target);
-
-            // Verify that all items are DerivedTreeViewItem
-            VerifyItemType(target.ItemContainerGenerator);
-
-            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
-            {
-                foreach (var container in containerGenerator.Index.Containers)
-                {
-                    var item = Assert.IsType<DerivedTreeViewItem>(container);
-                    if (item.ItemCount > 0)
-                    {
-                        VerifyItemType(item.ItemContainerGenerator);
-                    }
-                }
-            }
-        }
-
-        private void ApplyTemplates(TreeView tree)
-        {
-            tree.ApplyTemplate();
-            tree.Presenter.ApplyTemplate();
-            ApplyTemplates(tree.Presenter.Panel.Children);
-        }
-
-        private void ApplyTemplates(IEnumerable<Control> controls)
-        {
-            foreach (TreeViewItem control in controls)
-            {
-                control.Template = CreateTreeViewItemTemplate();
-                control.ApplyTemplate();
-                control.Presenter.ApplyTemplate();
-                control.HeaderPresenter.ApplyTemplate();
-                ApplyTemplates(control.Presenter.Panel.Children);
-            }
-        }
-
-        private TreeViewItem GetItem(TreeView target, params int[] indexes)
-        {
-            var c = (ItemsControl)target;
-
-            foreach (var index in indexes)
-            {
-                var item = ((IList)c.Items)[index];
-                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-            }
-
-            return (TreeViewItem)c;
-        }
-
-        private IList<Node> CreateTestTreeData()
-        {
-            return new AvaloniaList<Node>
-            {
-                new Node
-                {
-                    Value = "Root",
-                    Children = new AvaloniaList<Node>
-                    {
-                        new Node
-                        {
-                            Value = "Child1",
-                        },
-                        new Node
-                        {
-                            Value = "Child2",
-                            Children = new AvaloniaList<Node>
-                            {
-                                new Node
-                                {
-                                    Value = "Grandchild2a",
-                                },
-                            },
-                        },
-                        new Node
-                        {
-                            Value = "Child3",
-                        }
-                    }
-                }
-            };
-        }
-
-        private void CreateNodeDataTemplate(Control control)
-        {
-            control.DataTemplates.Add(new TestTreeDataTemplate());
-        }
-
-        private IControlTemplate CreateTreeViewTemplate()
-        {
-            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
-            {
-                Name = "PART_ItemsPresenter",
-            }.RegisterInNameScope(scope));
-        }
-
-        private IControlTemplate CreateTreeViewItemTemplate()
-        {
-            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
-            {
-                Children =
-                {
-                    new ContentPresenter
-                    {
-                        Name = "PART_HeaderPresenter",
-                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
-                    }.RegisterInNameScope(scope),
-                    new ItemsPresenter
-                    {
-                        Name = "PART_ItemsPresenter",
-                    }.RegisterInNameScope(scope)
-                }
-            });
-        }
-
-        private void ExpandAll(TreeView tree)
-        {
-            foreach (var i in tree.ItemContainerGenerator.Containers)
-            {
-                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
-            }
-        }
-
-        private List<string> ExtractItemHeader(TreeView tree, int level)
-        {
-            return ExtractItemContent(tree.Presenter.Panel, 0, level)
-                .Select(x => x.Header)
-                .OfType<TextBlock>()
-                .Select(x => x.Text)
-                .ToList();
-        }
-
-        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
-        {
-            foreach (TreeViewItem container in panel.Children)
-            {
-                if (container.Template == null)
-                {
-                    container.Template = CreateTreeViewItemTemplate();
-                    container.ApplyTemplate();
-                }
-
-                if (currentLevel == level)
-                {
-                    yield return container;
-                }
-                else
-                {
-                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
-                    {
-                        yield return child;
-                    }
-                }
-            }
-        }
-
-        private void ClickContainer(Control container, KeyModifiers modifiers)
-        {
-            _mouse.Click(container, modifiers: modifiers);
-        }
-
-        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
-        {
-            foreach (var child in rootNode.Children)
-            {
-                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-                Assert.True(container.IsSelected);
-            }
-        }
-
-        private IDisposable Application()
-        {
-            return UnitTestApplication.Start(
-                TestServices.MockThreadingInterface.With(
-                    focusManager: new FocusManager(),
-                    keyboardDevice: () => new KeyboardDevice(),
-                    keyboardNavigation: new KeyboardNavigationHandler(),
-                    inputManager: new InputManager()));
-        }
-
-        private class Node : NotifyingBase
-        {
-            private IAvaloniaList<Node> _children;
-
-            public string Value { get; set; }
-
-            public IAvaloniaList<Node> Children
-            {
-                get
-                {
-                    return _children;
-                }
-
-                set
-                {
-                    _children = value;
-                    RaisePropertyChanged(nameof(Children));
-                }
-            }
-        }
-
-        private class TestTreeDataTemplate : ITreeDataTemplate
-        {
-            public Control Build(object param)
-            {
-                var node = (Node)param;
-                return new TextBlock { Text = node.Value };
-            }
-
-            public InstancedBinding ItemsSelector(object item)
-            {
-                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
-                return InstancedBinding.OneWay(obs);
-            }
-
-            public bool Match(object data)
-            {
-                return data is Node;
-            }
-        }
-
-        private class DerivedTreeView : TreeView
-        {
-        }
-
-        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
-        {
-            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-        }
-
-        private class DerivedTreeViewItem : TreeViewItem
-        {
-            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-        }
-
-        private class TestDataContext : INotifyPropertyChanged
-        {
-            private string _selectedItem;
-
-            public TestDataContext()
-            {
-                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
-            }
-
-            public ObservableCollection<string> Items { get; }
-
-            public string SelectedItem
-            {
-                get { return _selectedItem; }
-                set
-                {
-                    _selectedItem = value;
-                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
-                }
-            }
-
-            public event PropertyChangedEventHandler PropertyChanged;
-
-        }
-    }
-}
+////        [Fact]
+////        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+////                AssertChildrenSelected(target, rootNode);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+
+////                Assert.True(fromContainer.IsSelected);
+
+////                foreach (var child in rootNode.Children)
+////                {
+////                    if (child == from)
+////                    {
+////                        continue;
+////                    }
+
+////                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
+
+////                    Assert.False(container.IsSelected);
+////                }
+////            }
+////        }
+
+////        [Fact]
+////        public void Setting_SelectedItem_Should_Set_Container_Selected()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+
+////                Assert.NotNull(container);
+
+////                target.SelectedItem = item;
+
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        [Fact]
+////        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = tree[0].Children[1].Children[0];
+
+////                var called = false;
+////                target.SelectionChanged += (s, e) =>
+////                {
+////                    Assert.Empty(e.RemovedItems);
+////                    Assert.Equal(1, e.AddedItems.Count);
+////                    Assert.Same(item, e.AddedItems[0]);
+////                    called = true;
+////                };
+
+////                target.SelectedItem = item;
+////                Assert.True(called);
+////            }
+////        }
+
+////        [Fact]
+////        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
+////        {
+////            using (Application())
+////            {
+////                var dataContext = new TestDataContext();
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    DataContext = dataContext
+////                };
+
+////                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
+////                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+
+////                var selectedValues = new List<object>();
+
+////                dataContext.PropertyChanged += (_, e) =>
+////                {
+////                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
+////                        selectedValues.Add(dataContext.SelectedItem);
+////                };
+////                selectedValues.Add(dataContext.SelectedItem);
+
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
+
+////                Assert.Equal(3, selectedValues.Count);
+////                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
+////            }
+////        }
+
+////        [Fact]
+////        public void LogicalChildren_Should_Be_Set()
+////        {
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = new[] { "Foo", "Bar", "Baz " },
+////            };
+
+////            ApplyTemplates(target);
+
+////            var result = target.GetLogicalChildren()
+////                .OfType<TreeViewItem>()
+////                .Select(x => x.Header)
+////                .OfType<TextBlock>()
+////                .Select(x => x.Text)
+////                .ToList();
+
+////            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
+////        }
+
+////        [Fact]
+////        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+
+////            tree[0].Children.RemoveAt(1);
+
+////            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
+////        }
+
+////        [Fact]
+////        public void DataContexts_Should_Be_Correctly_Set()
+////        {
+////            var items = new object[]
+////            {
+////                "Foo",
+////                new Node { Value = "Bar" },
+////                new TextBlock { Text = "Baz" },
+////                new TreeViewItem { Header = "Qux" },
+////            };
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                DataContext = "Base",
+////                DataTemplates =
+////                {
+////                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
+////                },
+////                Items = items,
+////            };
+
+////            ApplyTemplates(target);
+
+////            var dataContexts = target.Presenter.Panel.Children
+////                .Cast<Control>()
+////                .Select(x => x.DataContext)
+////                .ToList();
+
+////            Assert.Equal(
+////                new object[] { items[0], items[1], "Base", "Base" },
+////                dataContexts);
+////        }
+
+////        [Fact]
+////        public void Control_Item_Should_Not_Be_NameScope()
+////        {
+////            var items = new object[]
+////            {
+////                new TreeViewItem(),
+////            };
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = items,
+////            };
+
+////            target.ApplyTemplate();
+////            target.Presenter.ApplyTemplate();
+
+////            var item = target.Presenter.Panel.LogicalChildren[0];
+////            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
+////        }
+
+////        [Fact]
+////        public void Should_React_To_Children_Changing()
+////        {
+////            var data = CreateTestTreeData();
+
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = data,
+////            };
+
+////            var root = new TestRoot(target);
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+
+////            // Make sure that the binding to Node.Children does not get collected.
+////            GC.Collect();
+
+////            data[0].Children = new AvaloniaList<Node>
+////            {
+////                new Node
+////                {
+////                    Value = "NewChild1",
+////                }
+////            };
+
+////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+////            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
+////        }
+
+////        [Fact]
+////        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
+////        {
+////            using (Application())
+////            {
+////                var focus = FocusManager.Instance;
+////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+////                var data = CreateTestTreeData();
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = data,
+////                };
+
+////                var button = new Button();
+
+////                var root = new TestRoot
+////                {
+////                    Child = new StackPanel
+////                    {
+////                        Children = { target, button },
+////                    }
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = data[0].Children[0];
+////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////                Assert.NotNull(node);
+
+////                target.SelectedItem = item;
+////                node.Focus();
+////                Assert.Same(node, focus.Current);
+
+////                navigation.Move(focus.Current, NavigationDirection.Next);
+////                Assert.Same(button, focus.Current);
+
+////                navigation.Move(focus.Current, NavigationDirection.Next);
+////                Assert.Same(node, focus.Current);
+////            }
+////        }
+
+////        [Fact]
+////        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
+////        {
+////            using (Application())
+////            {
+////                var focus = FocusManager.Instance;
+////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+////                var data = CreateTestTreeData();
+
+////                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
+
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = data,
+////                    SelectedItem = selectedNode
+////                };
+
+////                var button = new Button();
+
+////                var root = new TestRoot
+////                {
+////                    Child = new StackPanel
+////                    {
+////                        Children = { target, button },
+////                    }
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var item = data[0].Children[0];
+////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////                Assert.NotNull(node);
+
+////                target.SelectedItem = selectedNode;
+////                node.Focus();
+////                Assert.Same(node, focus.Current);
+
+////                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
+////        {
+////            using (UnitTestApplication.Start())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children.Last();
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                ExpandAll(target);
+
+////                var rootNode = tree[0];
+
+////                var from = rootNode.Children.Last();
+////                var to = rootNode.Children[0];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+////                var selectAllGesture = keymap.SelectAll.First();
+
+////                var keyEvent = new KeyEventArgs
+////                {
+////                    RoutedEvent = InputElement.KeyDownEvent,
+////                    Key = selectAllGesture.Key,
+////                    KeyModifiers = selectAllGesture.KeyModifiers
+////                };
+
+////                target.RaiseEvent(keyEvent);
+
+////                AssertChildrenSelected(target, rootNode);
+////            }
+////        }
+
+////        [Fact]
+////        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
+////        {
+////            using (UnitTestApplication.Start())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+////                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+////                target.SelectAll();
+
+////                AssertChildrenSelected(target, tree[0]);
+////                Assert.Equal(5, target.SelectedItems.Count);
+
+////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
+
+////                Assert.Equal(5, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var to = rootNode.Children[0];
+////                var then = rootNode.Children[1];
+
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+////                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
+
+////                ClickContainer(fromContainer, KeyModifiers.None);
+////                ClickContainer(toContainer, KeyModifiers.Shift);
+
+////                Assert.Equal(2, target.SelectedItems.Count);
+
+////                _mouse.Click(thenContainer, MouseButton.Right);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Shift_Right_Click_Should_Not_Select_Multiple()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children[1];
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                _mouse.Click(fromContainer);
+////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
+////        {
+////            using (Application())
+////            {
+////                var tree = CreateTestTreeData();
+////                var target = new TreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    Items = tree,
+////                    SelectionMode = SelectionMode.Multiple,
+////                };
+
+////                var visualRoot = new TestRoot();
+////                visualRoot.Child = target;
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+////                var rootNode = tree[0];
+////                var from = rootNode.Children[0];
+////                var to = rootNode.Children[1];
+////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
+////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+
+////                _mouse.Click(fromContainer);
+////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
+
+////                Assert.Equal(1, target.SelectedItems.Count);
+////            }
+////        }
+
+////        [Fact]
+////        public void TreeViewItems_Level_Should_Be_Set()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(0, GetItem(target, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 1).Level);
+////            Assert.Equal(1, GetItem(target, 0, 2).Level);
+////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+////        }
+
+////        [Fact]
+////        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new DerivedTreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(0, GetItem(target, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 0).Level);
+////            Assert.Equal(1, GetItem(target, 0, 1).Level);
+////            Assert.Equal(1, GetItem(target, 0, 2).Level);
+////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+////        }
+
+////        [Fact]
+////        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
+////        {
+////            // Issue #2985
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var visualRoot = new TestRoot();
+////            visualRoot.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            var parent = tree[0];
+////            var node = parent.Children[1];
+
+////            parent.Children.Remove(node);
+////            parent.Children.Add(node);
+
+////            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
+////            ApplyTemplates(new[] { item });
+
+////            // #2985 causes ArgumentException here.
+////            node.Children.Add(new Node());
+////        }
+
+////        [Fact]
+////        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
+////        {
+////            // Issue #2980.
+////            using (Application())
+////            {
+////                var target = new DerivedTreeView
+////                {
+////                    Template = CreateTreeViewTemplate(),
+////                    SelectionMode = SelectionMode.Multiple,
+////                    Items = new List<Node>
+////                {
+////                    new Node { Value = "Root1", },
+////                    new Node { Value = "Root2", },
+////                },
+////                };
+
+////                var visualRoot = new TestRoot
+////                {
+////                    Styles =
+////                    {
+////                        new Style(x => x.OfType<TreeViewItem>())
+////                        {
+////                            Setters =
+////                            {
+////                                new Setter(TreeViewItem.IsExpandedProperty, true),
+////                            },
+////                        },
+////                    },
+////                    Child = target,
+////                };
+
+////                CreateNodeDataTemplate(target);
+////                ApplyTemplates(target);
+
+////                _mouse.Click(GetItem(target, 0));
+////                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
+////            }
+////        }
+
+////        [Fact]
+////        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
+////        {
+////            // Issue #3328
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+////            ExpandAll(target);
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+
+////            root.Child = null;
+
+////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
+////            Assert.Equal(1, target.Presenter.Panel.Children.Count);
+
+////            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
+////            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
+////            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
+
+////            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
+////            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
+////            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
+////        }
+
+////        [Fact]
+////        public void Clearing_TreeView_Items_Clears_Index()
+////        {
+////            // Issue #3551
+////            var tree = CreateTestTreeData();
+////            var target = new TreeView
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            var root = new TestRoot();
+////            root.Child = target;
+
+////            CreateNodeDataTemplate(target);
+////            ApplyTemplates(target);
+
+////            var rootNode = tree[0];
+////            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
+
+////            Assert.NotNull(container);
+
+////            root.Child = null;
+
+////            tree.Clear();
+
+////            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
+////        }
+
+////        [Fact]
+////        public void Can_Use_Derived_TreeViewItem()
+////        {
+////            var tree = CreateTestTreeData();
+////            var target = new DerivedTreeViewWithDerivedTreeViewItems
+////            {
+////                Template = CreateTreeViewTemplate(),
+////                Items = tree,
+////            };
+
+////            ApplyTemplates(target);
+
+////            // Verify that all items are DerivedTreeViewItem
+////            VerifyItemType(target.ItemContainerGenerator);
+
+////            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
+////            {
+////                foreach (var container in containerGenerator.Index.Containers)
+////                {
+////                    var item = Assert.IsType<DerivedTreeViewItem>(container);
+////                    if (item.ItemCount > 0)
+////                    {
+////                        VerifyItemType(item.ItemContainerGenerator);
+////                    }
+////                }
+////            }
+////        }
+
+////        private void ApplyTemplates(TreeView tree)
+////        {
+////            tree.ApplyTemplate();
+////            tree.Presenter.ApplyTemplate();
+////            ApplyTemplates(tree.Presenter.Panel.Children);
+////        }
+
+////        private void ApplyTemplates(IEnumerable<Control> controls)
+////        {
+////            foreach (TreeViewItem control in controls)
+////            {
+////                control.Template = CreateTreeViewItemTemplate();
+////                control.ApplyTemplate();
+////                control.Presenter.ApplyTemplate();
+////                control.HeaderPresenter.ApplyTemplate();
+////                ApplyTemplates(control.Presenter.Panel.Children);
+////            }
+////        }
+
+////        private TreeViewItem GetItem(TreeView target, params int[] indexes)
+////        {
+////            var c = (ItemsControl)target;
+
+////            foreach (var index in indexes)
+////            {
+////                var item = ((IList)c.Items)[index];
+////                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+////            }
+
+////            return (TreeViewItem)c;
+////        }
+
+////        private IList<Node> CreateTestTreeData()
+////        {
+////            return new AvaloniaList<Node>
+////            {
+////                new Node
+////                {
+////                    Value = "Root",
+////                    Children = new AvaloniaList<Node>
+////                    {
+////                        new Node
+////                        {
+////                            Value = "Child1",
+////                        },
+////                        new Node
+////                        {
+////                            Value = "Child2",
+////                            Children = new AvaloniaList<Node>
+////                            {
+////                                new Node
+////                                {
+////                                    Value = "Grandchild2a",
+////                                },
+////                            },
+////                        },
+////                        new Node
+////                        {
+////                            Value = "Child3",
+////                        }
+////                    }
+////                }
+////            };
+////        }
+
+////        private void CreateNodeDataTemplate(Control control)
+////        {
+////            control.DataTemplates.Add(new TestTreeDataTemplate());
+////        }
+
+////        private IControlTemplate CreateTreeViewTemplate()
+////        {
+////            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
+////            {
+////                Name = "PART_ItemsPresenter",
+////            }.RegisterInNameScope(scope));
+////        }
+
+////        private IControlTemplate CreateTreeViewItemTemplate()
+////        {
+////            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
+////            {
+////                Children =
+////                {
+////                    new ContentPresenter
+////                    {
+////                        Name = "PART_HeaderPresenter",
+////                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
+////                    }.RegisterInNameScope(scope),
+////                    new ItemsPresenter
+////                    {
+////                        Name = "PART_ItemsPresenter",
+////                    }.RegisterInNameScope(scope)
+////                }
+////            });
+////        }
+
+////        private void ExpandAll(TreeView tree)
+////        {
+////            foreach (var i in tree.ItemContainerGenerator.Containers)
+////            {
+////                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
+////            }
+////        }
+
+////        private List<string> ExtractItemHeader(TreeView tree, int level)
+////        {
+////            return ExtractItemContent(tree.Presenter.Panel, 0, level)
+////                .Select(x => x.Header)
+////                .OfType<TextBlock>()
+////                .Select(x => x.Text)
+////                .ToList();
+////        }
+
+////        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
+////        {
+////            foreach (TreeViewItem container in panel.Children)
+////            {
+////                if (container.Template == null)
+////                {
+////                    container.Template = CreateTreeViewItemTemplate();
+////                    container.ApplyTemplate();
+////                }
+
+////                if (currentLevel == level)
+////                {
+////                    yield return container;
+////                }
+////                else
+////                {
+////                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
+////                    {
+////                        yield return child;
+////                    }
+////                }
+////            }
+////        }
+
+////        private void ClickContainer(Control container, KeyModifiers modifiers)
+////        {
+////            _mouse.Click(container, modifiers: modifiers);
+////        }
+
+////        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
+////        {
+////            foreach (var child in rootNode.Children)
+////            {
+////                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
+
+////                Assert.True(container.IsSelected);
+////            }
+////        }
+
+////        private IDisposable Application()
+////        {
+////            return UnitTestApplication.Start(
+////                TestServices.MockThreadingInterface.With(
+////                    focusManager: new FocusManager(),
+////                    keyboardDevice: () => new KeyboardDevice(),
+////                    keyboardNavigation: new KeyboardNavigationHandler(),
+////                    inputManager: new InputManager()));
+////        }
+
+////        private class Node : NotifyingBase
+////        {
+////            private IAvaloniaList<Node> _children;
+
+////            public string Value { get; set; }
+
+////            public IAvaloniaList<Node> Children
+////            {
+////                get
+////                {
+////                    return _children;
+////                }
+
+////                set
+////                {
+////                    _children = value;
+////                    RaisePropertyChanged(nameof(Children));
+////                }
+////            }
+////        }
+
+////        private class TestTreeDataTemplate : ITreeDataTemplate
+////        {
+////            public Control Build(object param)
+////            {
+////                var node = (Node)param;
+////                return new TextBlock { Text = node.Value };
+////            }
+
+////            public InstancedBinding ItemsSelector(object item)
+////            {
+////                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
+////                return InstancedBinding.OneWay(obs);
+////            }
+
+////            public bool Match(object data)
+////            {
+////                return data is Node;
+////            }
+////        }
+
+////        private class DerivedTreeView : TreeView
+////        {
+////        }
+
+////        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
+////        {
+////            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
+////                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
+////        }
+
+////        private class DerivedTreeViewItem : TreeViewItem
+////        {
+////            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
+////        }
+
+////        private class TestDataContext : INotifyPropertyChanged
+////        {
+////            private string _selectedItem;
+
+////            public TestDataContext()
+////            {
+////                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
+////            }
+
+////            public ObservableCollection<string> Items { get; }
+
+////            public string SelectedItem
+////            {
+////                get { return _selectedItem; }
+////                set
+////                {
+////                    _selectedItem = value;
+////                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
+////                }
+////            }
+
+////            public event PropertyChangedEventHandler PropertyChanged;
+
+////        }
+////    }
+////}
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index 9170c68e11..f46ad44684 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -361,7 +361,8 @@ namespace Avalonia.LeakTests
 
                     // Do a layout and make sure that TreeViewItems get realized.
                     window.LayoutManager.ExecuteInitialLayoutPass();
-                    Assert.Single(target.ItemContainerGenerator.Containers);
+                    throw new NotImplementedException();
+                    ////Assert.Single(target.ItemContainerGenerator.Containers);
 
                     // Clear the content and ensure the TreeView is removed.
                     window.Content = null;
@@ -756,20 +757,22 @@ namespace Avalonia.LeakTests
                 window.Show();
                 window.LayoutManager.ExecuteInitialLayoutPass();
 
-                void AssertInitialItemState()
-                {
-                    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
-                    var canvas0 = (Canvas)item0.Presenter.Child;
-                    Assert.Equal("foo", canvas0.Tag);
-                }
+                throw new NotImplementedException();
+
+                ////void AssertInitialItemState()
+                ////{
+                ////    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
+                ////    var canvas0 = (Canvas)item0.Presenter.Child;
+                ////    Assert.Equal("foo", canvas0.Tag);
+                ////}
                
-                Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
-                AssertInitialItemState();
+                ////Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
+                ////AssertInitialItemState();
 
-                items.Clear();
-                window.LayoutManager.ExecuteLayoutPass();
+                ////items.Clear();
+                ////window.LayoutManager.ExecuteLayoutPass();
 
-                Assert.Empty(lb.ItemContainerGenerator.Containers);
+                ////Assert.Empty(lb.ItemContainerGenerator.Containers);
 
                 // Process all Loaded events to free control reference(s)
                 Dispatcher.UIThread.RunJobs(DispatcherPriority.Loaded);

From 57b1ba965cb40bcfd7b724fba51fec2614d61cc2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 28 Nov 2022 23:17:11 +0100
Subject: [PATCH 010/157] Implement INavigableContainer.

---
 src/Avalonia.Controls/VirtualizingPanel.cs    | 22 +++++-
 .../VirtualizingStackPanel.cs                 | 70 ++++++++++++++++++-
 2 files changed, 87 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index dd40f868d5..87c630658f 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -3,13 +3,14 @@ using System.Collections;
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
+using Avalonia.Input;
 
 namespace Avalonia.Controls
 {
     /// <summary>
     /// Base class for panels that can be used to virtualize items.
     /// </summary>
-    public abstract class VirtualizingPanel : Panel
+    public abstract class VirtualizingPanel : Panel, INavigableContainer
     {
         private ItemsControl? _itemsControl;
 
@@ -27,11 +28,19 @@ namespace Avalonia.Controls
             }
         }
 
+        IInputElement? INavigableContainer.GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
+        {
+            return GetControl(direction, from, wrap);
+        }
+
         /// <summary>
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="index">The index of the item.</param>
-        protected internal abstract void ScrollIntoView(int index);
+        /// <returns>
+        /// The element with the specified index, or null if the element could not be brought into view.
+        /// </returns>
+        protected internal abstract Control? ScrollIntoView(int index);
 
         /// <summary>
         /// Returns the container for the item at the specified index.
@@ -53,6 +62,15 @@ namespace Avalonia.Controls
         /// </returns>
         protected internal abstract int IndexFromContainer(Control container);
 
+        /// <summary>
+        /// Gets the next control in the specified direction.
+        /// </summary>
+        /// <param name="direction">The movement direction.</param>
+        /// <param name="from">The control from which movement begins.</param>
+        /// <param name="wrap">Whether to wrap around when the first or last item is reached.</param>
+        /// <returns>The control.</returns>
+        protected abstract IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap);
+
         /// <summary>
         /// Called when the <see cref="ItemsControl"/> that owns the panel changes.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index a4e287dc08..2e80edd6bb 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,8 +3,8 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
-using System.Xml.Linq;
 using Avalonia.Controls.Utils;
+using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
@@ -169,19 +169,79 @@ namespace Avalonia.Controls
             InvalidateMeasure();
         }
 
+        protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
+        {
+            var count = (ItemsControl?.Items as IList)?.Count ?? 0;
+
+            if (count == 0)
+                return null;
+
+            var horiz = Orientation == Orientation.Horizontal;
+            var fromIndex = from != null ? Children.IndexOf(from) : -1;
+            var toIndex = fromIndex;
+
+            switch (direction)
+            {
+                case NavigationDirection.First:
+                    toIndex = 0;
+                    break;
+                case NavigationDirection.Last:
+                    toIndex = count - 1;
+                    break;
+                case NavigationDirection.Next:
+                    ++toIndex;
+                    break;
+                case NavigationDirection.Previous:
+                    --toIndex;
+                    break;
+                case NavigationDirection.Left:
+                    if (horiz)
+                        --toIndex;
+                    break;
+                case NavigationDirection.Right:
+                    if (horiz)
+                        ++toIndex;
+                    break;
+                case NavigationDirection.Up:
+                    if (!horiz)
+                        --toIndex;
+                    break;
+                case NavigationDirection.Down:
+                    if (!horiz)
+                        ++toIndex;
+                    break;
+                default:
+                    return null;
+            }
+
+            if (fromIndex == toIndex)
+                return from;
+
+            if (wrap)
+            {
+                if (toIndex < 0)
+                    toIndex = count - 1;
+                else if (toIndex >= count - 1)
+                    toIndex = 0;
+            }
+
+            return ScrollIntoView(toIndex);
+        }
+
         protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
         protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
 
-        protected internal override void ScrollIntoView(int index)
+        protected internal override Control? ScrollIntoView(int index)
         {
             var items = ItemsControl?.Items as IList;
 
             if (_isInLayout || items is null || index < 0 || index >= items.Count)
-                return;
+                return null;
 
             if (GetRealizedElement(index) is Control element)
             {
                 element.BringIntoView();
+                return element;
             }
             else if (this.GetVisualRoot() is ILayoutRoot root)
             {
@@ -216,9 +276,13 @@ namespace Avalonia.Controls
                 root.LayoutManager.ExecuteLayoutPass();
                 _isWaitingForViewportUpdate = false;
 
+                var result = _anchorElement;
                 _anchorElement = null;
                 _anchorIndex = -1;
+                return result;
             }
+
+            return null;
         }
 
         internal IReadOnlyList<Control?> GetRealizedElements()

From e07e5cead56c41ee3c14ca3f874eeb1a88d59ead Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:16:55 +0100
Subject: [PATCH 011/157] Fix container generation logic.

---
 .../Presenters/PanelContainerGenerator.cs     | 21 ++++++++-----------
 1 file changed, 9 insertions(+), 12 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index f1765ba986..ea6276feb4 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -66,7 +66,10 @@ namespace Avalonia.Controls.Presenters
             {
                 var i = index;
                 foreach (var item in items)
-                    panel.Children.Insert(i++, CreateContainer(itemsControl, item, i));
+                {
+                    panel.Children.Insert(i, CreateContainer(itemsControl, item, i));
+                    ++i;
+                }
             }
             
             void Remove(int index, int count)
@@ -106,18 +109,12 @@ namespace Avalonia.Controls.Presenters
         private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
+            var container = item is Control c && generator.IsItemItsOwnContainer(c) ?
+                c : generator.CreateContainer();
 
-            if (item is Control c && generator.IsItemItsOwnContainer(c))
-            {
-                return c;
-            }
-            else
-            {
-                c = generator.CreateContainer();
-                itemsControl.AddLogicalChild(c);
-                generator.PrepareItemContainer(c, item, index);
-                return c;
-            }
+            itemsControl.AddLogicalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+            return container;
         }
     }
 }

From a1d809b49dbceb8aa07b3205387a64d436db212f Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:17:29 +0100
Subject: [PATCH 012/157] Fix VirtualizingStackPanel navigation logic.

---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 2e80edd6bb..1016a0af59 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -173,11 +173,11 @@ namespace Avalonia.Controls
         {
             var count = (ItemsControl?.Items as IList)?.Count ?? 0;
 
-            if (count == 0)
+            if (count == 0 || from is not Control fromControl)
                 return null;
 
             var horiz = Orientation == Orientation.Horizontal;
-            var fromIndex = from != null ? Children.IndexOf(from) : -1;
+            var fromIndex = from != null ? IndexFromContainer(fromControl) : -1;
             var toIndex = fromIndex;
 
             switch (direction)
@@ -708,7 +708,10 @@ namespace Avalonia.Controls
             /// </summary>
             /// <param name="element">The element.</param>
             /// <returns>The model index or -1 if the element is not present in the collection.</returns>
-            public int GetIndex(Control element) => _elements?.IndexOf(element) is int index && index >= 0 ? index : -1;
+            public int GetIndex(Control element)
+            {
+                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstModelIndex : -1;
+            }
 
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.

From b3982f18281a01d820564dada9fde55ba624d96c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:17:59 +0100
Subject: [PATCH 013/157] Create correct TabControl containers.

---
 src/Avalonia.Controls/TabControl.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 8ce1befde5..970d7de727 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -165,6 +165,9 @@ namespace Avalonia.Controls
             return RegisterContentPresenter(presenter);
         }
 
+        protected internal override Control CreateContainerOverride() => new TabItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabItem;
+
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
             base.PrepareContainerForItemOverride(element, item, index);

From fab8f15213b3c120ec4e9e029f4212f5a7205909 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:18:07 +0100
Subject: [PATCH 014/157] Make a few more tests pass.

---
 .../Primitives/SelectingItemsControlTests.cs           | 10 +++++++++-
 tests/Avalonia.Controls.UnitTests/TabControlTests.cs   |  2 --
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index d89e88b2ba..dbea9f79b8 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -16,11 +16,13 @@ using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
+using Avalonia.Layout;
 using Avalonia.Markup.Data;
 using Avalonia.Platform;
 using Avalonia.Styling;
 using Avalonia.Threading;
 using Avalonia.UnitTests;
+using Avalonia.VisualTree;
 using Moq;
 using Xunit;
 
@@ -1488,9 +1490,10 @@ namespace Avalonia.Controls.UnitTests.Primitives
 
                 // #3148 triggered here.
                 items.Reset(new[] { "Item99" });
+                Layout(target);
 
                 Assert.Equal(0, target.SelectedIndex);
-                Assert.Equal(1, target.Presenter.Panel.Children.Count);
+                Assert.Equal(1, target.Presenter.Panel.Children.Where(x => x.IsVisible).Count());
             }
         }
 
@@ -2083,6 +2086,11 @@ namespace Avalonia.Controls.UnitTests.Primitives
             root.LayoutManager.ExecuteInitialLayoutPass();
         }
 
+        private static void Layout(Control c)
+        {
+            ((ILayoutRoot)c.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+        }
+
         private static FuncControlTemplate Template()
         {
             return new FuncControlTemplate<SelectingItemsControl>((control, scope) =>
diff --git a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
index 3dcbb6caca..4c5397db60 100644
--- a/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TabControlTests.cs
@@ -431,8 +431,6 @@ namespace Avalonia.Controls.UnitTests
                         new ItemsPresenter
                         {
                             Name = "PART_ItemsPresenter",
-                            [!TabStrip.ItemsProperty] = parent[!TabControl.ItemsProperty],
-                            [!TabStrip.ItemTemplateProperty] = parent[!TabControl.ItemTemplateProperty],
                         }.RegisterInNameScope(scope),
                         new ContentPresenter
                         {

From 14d429ec4eca994998c995753bcf2a45f5ed914b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 00:18:48 +0100
Subject: [PATCH 015/157] Added ItemsControl.GetRealizedContainers().

---
 src/Avalonia.Controls/ItemsControl.cs         |  5 ++
 src/Avalonia.Controls/MenuItem.cs             | 11 +---
 .../Presenters/ItemsPresenter.cs              | 10 ++++
 .../Primitives/SelectingItemsControl.cs       | 59 +++++++++----------
 src/Avalonia.Controls/VirtualizingPanel.cs    |  6 ++
 .../VirtualizingStackPanel.cs                 |  6 ++
 tests/Avalonia.LeakTests/ControlTests.cs      | 27 ++++-----
 7 files changed, 69 insertions(+), 55 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index c4356e2967..e56cad15b8 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -211,6 +211,11 @@ namespace Avalonia.Controls
             throw new NotImplementedException();
         }
 
+        /// <summary>
+        /// Gets the currently realized containers.
+        /// </summary>
+        public IEnumerable<Control> GetRealizedContainers() => Presenter?.GetRealizedContainers() ?? Array.Empty<Control>();
+
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index d134704b26..dd336974ca 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -328,16 +328,7 @@ namespace Avalonia.Controls
         }
 
         /// <inheritdoc/>
-        IEnumerable<IMenuItem> IMenuElement.SubItems
-        {
-            get
-            {
-                throw new NotImplementedException();
-                ////return ItemContainerGenerator.Containers
-                ////    .Select(x => x.ContainerControl)
-                ////    .OfType<IMenuItem>();
-            }
-        }
+        IEnumerable<IMenuItem> IMenuElement.SubItems => GetRealizedContainers().OfType<IMenuItem>();
 
         /// <summary>
         /// Opens the submenu.
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 5f90c264d7..6f27349cc1 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,5 +1,8 @@
 using System;
+using System.Collections;
+using System.Collections.Generic;
 using System.Diagnostics;
+using System.Reflection;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -109,6 +112,13 @@ namespace Avalonia.Controls.Presenters
             return index >= 0 && index < Panel?.Children.Count ? Panel.Children[index] : null;
         }
 
+        internal IEnumerable<Control>? GetRealizedContainers()
+        {
+            if (Panel is VirtualizingPanel v)
+                return v.GetRealizedContainers();
+            return Panel?.Children;
+        }
+
         internal int IndexFromContainer(Control container)
         {
             if (Panel is VirtualizingPanel v)
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 1503da1322..a49705d754 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -507,45 +507,44 @@ namespace Avalonia.Controls.Primitives
 
         protected override void OnTextInput(TextInputEventArgs e)
         {
-            throw new NotImplementedException();
-            ////if (!e.Handled)
-            ////{
-            ////    if (!IsTextSearchEnabled)
-            ////        return;
+            if (!e.Handled)
+            {
+                if (!IsTextSearchEnabled)
+                    return;
 
-            ////    StopTextSearchTimer();
+                StopTextSearchTimer();
 
-            ////    _textSearchTerm += e.Text;
+                _textSearchTerm += e.Text;
 
-            ////    bool Match(ItemContainerInfo info)
-            ////    {
-            ////        if (info.ContainerControl is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
-            ////        {
-            ////            var searchText = ao.GetValue(TextSearch.TextProperty);
+                bool Match(Control container)
+                {
+                    if (container is AvaloniaObject ao && ao.IsSet(TextSearch.TextProperty))
+                    {
+                        var searchText = ao.GetValue(TextSearch.TextProperty);
 
-            ////            if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
-            ////            {
-            ////                return true;
-            ////            }
-            ////        }
+                        if (searchText?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true)
+                        {
+                            return true;
+                        }
+                    }
 
-            ////        return info.ContainerControl is IContentControl control &&
-            ////               control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
-            ////    }
-                
-            ////    var info = ItemContainerGenerator?.Containers.FirstOrDefault(Match);
+                    return container is IContentControl control &&
+                           control.Content?.ToString()?.StartsWith(_textSearchTerm, StringComparison.OrdinalIgnoreCase) == true;
+                }
 
-            ////    if (info != null)
-            ////    {
-            ////        SelectedIndex = info.Index;
-            ////    }
+                var container = GetRealizedContainers().FirstOrDefault(Match);
 
-            ////    StartTextSearchTimer();
+                if (container != null)
+                {
+                    SelectedIndex = IndexFromContainer(container);
+                }
 
-            ////    e.Handled = true;
-            ////}
+                StartTextSearchTimer();
+
+                e.Handled = true;
+            }
 
-            ////base.OnTextInput(e);
+            base.OnTextInput(e);
         }
 
         protected override void OnKeyDown(KeyEventArgs e)
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 87c630658f..0b7a183728 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections;
+using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Utils;
@@ -62,6 +63,11 @@ namespace Avalonia.Controls
         /// </returns>
         protected internal abstract int IndexFromContainer(Control container);
 
+        /// <summary>
+        /// Gets the currently realized containers.
+        /// </summary>
+        protected internal abstract IEnumerable<Control>? GetRealizedContainers();
+
         /// <summary>
         /// Gets the next control in the specified direction.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 1016a0af59..76cbf94f09 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -3,6 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
+using System.Linq;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
 using Avalonia.Layout;
@@ -228,6 +229,11 @@ namespace Avalonia.Controls
             return ScrollIntoView(toIndex);
         }
 
+        protected internal override IEnumerable<Control>? GetRealizedContainers()
+        {
+            return _realizedElements?.Elements.Where(x => x is not null)!;
+        }
+
         protected internal override Control? ContainerFromIndex(int index) => _realizedElements?.GetElement(index);
         protected internal override int IndexFromContainer(Control container) => _realizedElements?.GetIndex(container) ?? -1;
 
diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index f46ad44684..4433e25c5a 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -361,8 +361,7 @@ namespace Avalonia.LeakTests
 
                     // Do a layout and make sure that TreeViewItems get realized.
                     window.LayoutManager.ExecuteInitialLayoutPass();
-                    throw new NotImplementedException();
-                    ////Assert.Single(target.ItemContainerGenerator.Containers);
+                    Assert.Single(target.GetRealizedContainers());
 
                     // Clear the content and ensure the TreeView is removed.
                     window.Content = null;
@@ -757,22 +756,20 @@ namespace Avalonia.LeakTests
                 window.Show();
                 window.LayoutManager.ExecuteInitialLayoutPass();
 
-                throw new NotImplementedException();
+                void AssertInitialItemState()
+                {
+                    var item0 = (ListBoxItem)lb.GetRealizedContainers().First();
+                    var canvas0 = (Canvas)item0.Presenter.Child;
+                    Assert.Equal("foo", canvas0.Tag);
+                }
 
-                ////void AssertInitialItemState()
-                ////{
-                ////    var item0 = (ListBoxItem)lb.ItemContainerGenerator.Containers.First().ContainerControl;
-                ////    var canvas0 = (Canvas)item0.Presenter.Child;
-                ////    Assert.Equal("foo", canvas0.Tag);
-                ////}
-               
-                ////Assert.Equal(10, lb.ItemContainerGenerator.Containers.Count());
-                ////AssertInitialItemState();
+                Assert.Equal(10, lb.GetRealizedContainers().Count());
+                AssertInitialItemState();
 
-                ////items.Clear();
-                ////window.LayoutManager.ExecuteLayoutPass();
+                items.Clear();
+                window.LayoutManager.ExecuteLayoutPass();
 
-                ////Assert.Empty(lb.ItemContainerGenerator.Containers);
+                Assert.Empty(lb.GetRealizedContainers());
 
                 // Process all Loaded events to free control reference(s)
                 Dispatcher.UIThread.RunJobs(DispatcherPriority.Loaded);

From bbd3d2a500a977983680cdacbfed84577f12075b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 17:43:25 +0100
Subject: [PATCH 016/157] Only remove generated logical children.

---
 src/Avalonia.Controls/ItemsControl.cs         |  1 -
 .../Presenters/PanelContainerGenerator.cs     | 35 ++++++++++++++++---
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e56cad15b8..b7a63811c4 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -456,7 +456,6 @@ namespace Avalonia.Controls
 
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
-        internal void ClearLogicalChildren() => LogicalChildren.Clear();
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index ea6276feb4..56e1901117 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -11,6 +11,9 @@ namespace Avalonia.Controls.Presenters
     /// </summary>
     internal class PanelContainerGenerator : IDisposable
     {
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<PanelContainerGenerator, Control, bool>("ItemIsOwnContainer");
+
         private readonly ItemsPresenter _presenter;
 
         public PanelContainerGenerator(ItemsPresenter presenter)
@@ -36,7 +39,7 @@ namespace Avalonia.Controls.Presenters
                 if (itemsControl.Items is INotifyCollectionChanged incc)
                     incc.CollectionChanged -= OnItemsChanged;
 
-                itemsControl.ClearLogicalChildren();
+                ClearItemsControlLogicalChildren();
             }
 
             _presenter.Panel?.Children.Clear();
@@ -98,7 +101,7 @@ namespace Avalonia.Controls.Presenters
                     Add(e.NewStartingIndex, e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    itemsControl.ClearLogicalChildren();
+                    ClearItemsControlLogicalChildren();
                     panel.Children.Clear();
                     if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
@@ -109,12 +112,36 @@ namespace Avalonia.Controls.Presenters
         private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
-            var container = item is Control c && generator.IsItemItsOwnContainer(c) ?
-                c : generator.CreateContainer();
+            Control container;
+            
+            if (item is Control c && generator.IsItemItsOwnContainer(c))
+            {
+                container = c;
+                container.SetValue(ItemIsOwnContainerProperty, true);
+            }
+            else
+            {
+                container = generator.CreateContainer();
+            }
 
             itemsControl.AddLogicalChild(container);
             generator.PrepareItemContainer(container, item, index);
             return container;
         }
+
+        private void ClearItemsControlLogicalChildren()
+        {
+            if (_presenter.Panel is null || _presenter.ItemsControl is null)
+                return;
+
+            var itemsControl = _presenter.ItemsControl;
+            var panel = _presenter.Panel;
+
+            foreach (var c in panel.Children)
+            {
+                if (!c.IsSet(ItemIsOwnContainerProperty))
+                    itemsControl.RemoveLogicalChild(c);
+            }
+        }
     }
 }

From a9ca85230002e7c88299da447209f1d1ee531475 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 30 Nov 2022 23:29:06 +0100
Subject: [PATCH 017/157] Notify ItemsControl when container index changes.

---
 .../Generators/ItemContainerGenerator.cs      | 10 +++++++
 src/Avalonia.Controls/ItemsControl.cs         | 16 +++++++++++
 .../Presenters/PanelContainerGenerator.cs     | 27 ++++++++++++++-----
 .../Primitives/SelectingItemsControl.cs       |  6 +++++
 .../VirtualizingStackPanel.cs                 | 22 +++++++++------
 5 files changed, 67 insertions(+), 14 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index 0598bb1a63..1cf40d335f 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -56,6 +56,16 @@ namespace Avalonia.Controls.Generators
         public void PrepareItemContainer(Control container, object? item, int index) => 
             _owner.PrepareItemContainer(container, item, index);
 
+        /// <summary>
+        /// Called when the index for a container changes due to an insertion or removal in the
+        /// items collection.
+        /// </summary>
+        /// <param name="container">The container whose index changed.</param>
+        /// <param name="oldIndex">The old index.</param>
+        /// <param name="newIndex">The new index.</param>
+        public void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex) =>
+            _owner.ItemContainerIndexChanged(container, oldIndex, newIndex);
+
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b7a63811c4..7c24717a06 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -298,6 +298,17 @@ namespace Avalonia.Controls
                 container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
         }
 
+        /// <summary>
+        /// Called when the index for a container changes due to an insertion or removal in the
+        /// items collection.
+        /// </summary>
+        /// <param name="container">The container whose index changed.</param>
+        /// <param name="oldIndex">The old index.</param>
+        /// <param name="newIndex">The new index.</param>
+        protected virtual void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+        }
+
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareContainerForItemOverride(Control, object?, int)"/> method.
         /// </summary>
@@ -474,6 +485,11 @@ namespace Avalonia.Controls
             PrepareContainerForItemOverride(container, item, index);
         }
 
+        internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
+        {
+            ContainerIndexChangedOverride(container, oldIndex, newIndex);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 56e1901117..4a31017fbd 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -63,25 +63,40 @@ namespace Avalonia.Controls.Presenters
                 return;
 
             var itemsControl = _presenter.ItemsControl;
-            var panel = _presenter.Panel;
+            var generator = itemsControl.ItemContainerGenerator;
+            var children = _presenter.Panel.Children;
 
             void Add(int index, IEnumerable items)
             {
                 var i = index;
                 foreach (var item in items)
                 {
-                    panel.Children.Insert(i, CreateContainer(itemsControl, item, i));
+                    children.Insert(i, CreateContainer(itemsControl, item, i));
                     ++i;
                 }
+
+                var childCount = children.Count;
+                var delta = i - index;
+
+                for (; i < childCount; ++i)
+                    generator.ItemContainerIndexChanged(children[i], i - delta, i);
             }
-            
+
             void Remove(int index, int count)
             {
                 for (var i = 0; i < count; ++i)
                 {
-                    itemsControl.RemoveLogicalChild(panel.Children[i + index]);
-                    panel.Children.RemoveAt(i + index);
+                    var c = children[i];
+                    if (!c.IsSet(ItemIsOwnContainerProperty))
+                        itemsControl.RemoveLogicalChild(children[i + index]);
                 }
+
+                children.RemoveRange(index, count);
+
+                var childCount = children.Count;
+
+                for (var i = index; i < childCount; ++i)
+                    generator.ItemContainerIndexChanged(children[i], i - count, i);
             }
 
             switch (e.Action)
@@ -102,7 +117,7 @@ namespace Avalonia.Controls.Presenters
                     break;
                 case NotifyCollectionChangedAction.Reset:
                     ClearItemsControlLogicalChildren();
-                    panel.Children.Clear();
+                    children.Clear();
                     if (_presenter.ItemsControl?.Items is { } items)
                         Add(0, items);
                     break;
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index a49705d754..253726c5aa 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -449,6 +449,12 @@ namespace Avalonia.Controls.Primitives
             }
         }
 
+        protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+            base.ContainerIndexChangedOverride(container, oldIndex, newIndex);
+            MarkContainerSelected(container, Selection.IsSelected(newIndex));
+        }
+
         protected internal override void ClearContainerForItemOverride(Control element)
         {
             base.ClearContainerForItemOverride(element);
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 76cbf94f09..6373d5f3bd 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -25,7 +25,7 @@ namespace Avalonia.Controls
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
-        private readonly Action<Control, int> _updateElementIndex;
+        private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
         private bool _isInLayout;
@@ -513,9 +513,9 @@ namespace Avalonia.Controls
             }
         }
 
-        private void UpdateElementIndex(Control element, int index)
+        private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
-            // TODO: Implement this after we refactor ItemContainerGenerator.
+            ItemsControl!.ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
         }
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
@@ -725,7 +725,7 @@ namespace Avalonia.Controls
             /// <param name="modelIndex">The index in the source collection of the insert.</param>
             /// <param name="count">The number of items inserted.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int> updateElementIndex)
+            public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> updateElementIndex)
             {
                 if (modelIndex < 0)
                     throw new ArgumentOutOfRangeException(nameof(modelIndex));
@@ -742,11 +742,13 @@ namespace Avalonia.Controls
                     // elements after the insertion point.
                     var elementCount = _elements.Count;
                     var start = Math.Max(index, 0);
+                    var newIndex = first + count;
 
                     for (var i = start; i < elementCount; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i + count);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
 
                     if (index <= 0)
@@ -774,7 +776,7 @@ namespace Avalonia.Controls
             public void ItemsRemoved(
                 int modelIndex,
                 int count,
-                Action<Control, int> updateElementIndex,
+                Action<Control, int, int> updateElementIndex,
                 Action<Control> recycleElement)
             {
                 if (modelIndex < 0)
@@ -794,10 +796,12 @@ namespace Avalonia.Controls
                     // the indexes of the realized elements.
                     _firstIndex -= count;
 
+                    var newIndex = _firstIndex;
                     for (var i = 0; i < _elements.Count; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, _firstIndex + i);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
                 }
                 else if (startIndex < _elements.Count)
@@ -822,10 +826,12 @@ namespace Avalonia.Controls
 
                     // Update the indexes of the elements after the removed range.
                     end = _elements.Count;
+                    var newIndex = first;
                     for (var i = start; i < end; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, first + i);
+                            updateElementIndex(element, newIndex - count, newIndex);
+                        ++newIndex;
                     }
                 }
             }

From c1ee26c05a0b6c70749775dd69918cd8ddc52d75 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 00:20:22 +0100
Subject: [PATCH 018/157] Fixed SelectingItemsControlTests.

`ListBox` now needs a root as it uses a `VirtualizingStackPanel`.
---
 .../SelectingItemsControlTests_Multiple.cs    | 136 ++++++++++++------
 1 file changed, 96 insertions(+), 40 deletions(-)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
index efce0a715c..0b72baf336 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests_Multiple.cs
@@ -710,14 +710,16 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Shift);
 
-                var panel = target.Presenter.Panel;
-
                 Assert.Equal(new[] { "Foo", "Bar", "Baz" }, target.SelectedItems);
                 Assert.Equal(new[] { 0, 1, 2 }, SelectedContainers(target));
             }
@@ -733,10 +735,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 SelectionChangedEventArgs receivedArgs = null;
 
@@ -787,10 +793,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Control);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3], modifiers: KeyModifiers.Control);
@@ -817,11 +827,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
 
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
+                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], modifiers: KeyModifiers.Control);
 
@@ -845,10 +858,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[4], modifiers: KeyModifiers.Control);
 
@@ -869,10 +886,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[3]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[5], modifiers: KeyModifiers.Shift);
 
@@ -893,10 +914,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[5], modifiers: KeyModifiers.Shift);
 
@@ -917,10 +942,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Qux" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 SelectionChangedEventArgs receivedArgs = null;
 
@@ -966,11 +994,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Template = Template(),
                     Items = new[] { "Foo", "Bar", "Baz", "Foo", "Bar", "Baz" },
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
 
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
 
                 Assert.Equal(new[] { "Foo" }, target.SelectedItems);
@@ -1084,13 +1115,16 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items.Insert(0, "Qux");
+            root.LayoutManager.ExecuteLayoutPass();
 
             Assert.Equal(1, target.SelectedIndex);
             Assert.Equal("Foo", target.SelectedItem);
@@ -1146,10 +1180,12 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items.RemoveAt(0);
@@ -1175,10 +1211,12 @@ namespace Avalonia.Controls.UnitTests.Primitives
                 Template = Template(),
                 Items = items,
                 SelectionMode = SelectionMode.Multiple,
+                Width = 100,
+                Height = 100,
             };
 
-            target.ApplyTemplate();
-            target.Presenter.ApplyTemplate();
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
 
             target.SelectAll();
             items[1] = "Qux";
@@ -1197,10 +1235,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 target.SelectAll();
 
                 Assert.Equal(3, target.SelectedItems.Count);
@@ -1224,10 +1265,13 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
-                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 target.SelectAll();
 
                 Assert.Equal(3, target.SelectedItems.Count);
@@ -1249,10 +1293,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[1], modifiers: KeyModifiers.Shift);
 
@@ -1301,10 +1349,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Right, modifiers: KeyModifiers.Shift);
@@ -1324,10 +1376,14 @@ namespace Avalonia.Controls.UnitTests.Primitives
                     Items = new[] { "Foo", "Bar", "Baz" },
                     ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Width = 20, Height = 10 }),
                     SelectionMode = SelectionMode.Multiple,
+                    Width = 100,
+                    Height = 100,
                 };
+
+                var root = new TestRoot(target);
+                root.LayoutManager.ExecuteInitialLayoutPass();
+
                 AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-                target.ApplyTemplate();
-                target.Presenter.ApplyTemplate();
 
                 _helper.Click((Interactive)target.Presenter.Panel.Children[0]);
                 _helper.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Right, modifiers: KeyModifiers.Control);
@@ -1526,7 +1582,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
         private static IEnumerable<int> SelectedContainers(SelectingItemsControl target)
         {
             return target.Presenter.Panel.Children
-                .Select((x, i) => x.Classes.Contains(":selected") ? i : -1)
+                .Select(x => x.Classes.Contains(":selected") ? target.IndexFromContainer(x) : -1)
                 .Where(x => x != -1);
         }
 

From 6626a2e2182ae09d33c2c495f8b07019b96468d5 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 10:33:44 +0100
Subject: [PATCH 019/157] Update TabControl on container index change.

---
 .../Presenters/PanelContainerGenerator.cs              |  2 +-
 src/Avalonia.Controls/TabControl.cs                    | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 4a31017fbd..b080a9044f 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -96,7 +96,7 @@ namespace Avalonia.Controls.Presenters
                 var childCount = children.Count;
 
                 for (var i = index; i < childCount; ++i)
-                    generator.ItemContainerIndexChanged(children[i], i - count, i);
+                    generator.ItemContainerIndexChanged(children[i], i + count, i);
             }
 
             switch (e.Action)
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 970d7de727..d08e0a61da 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -174,6 +174,16 @@ namespace Avalonia.Controls
             UpdateSelectedContent();
         }
 
+        protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)
+        {
+            base.ContainerIndexChangedOverride(container, oldIndex, newIndex);
+
+            var selectedIndex = SelectedIndex;
+            
+            if (selectedIndex == oldIndex || selectedIndex == newIndex)
+                UpdateSelectedContent();
+        }
+
         protected internal override void ClearContainerForItemOverride(Control element)
         {
             base.ClearContainerForItemOverride(element);

From 8bb1349785fa3f68a920ccfc63936e378c4b0a93 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:31:01 +0100
Subject: [PATCH 020/157] Setup TabItems.

---
 src/Avalonia.Controls/ItemsControl.cs | 25 +++++++++++++++++--------
 src/Avalonia.Controls/TabControl.cs   | 10 +++++++++-
 2 files changed, 26 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 7c24717a06..3de4017190 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -281,21 +281,30 @@ namespace Avalonia.Controls
             if (container == item)
                 return;
 
-            if (container is ContentControl cc)
+            if (container is HeaderedContentControl hcc)
             {
-                cc.SetValue(ContentControl.ContentProperty, item, BindingPriority.Template);
+                hcc.Content = item;
+
+                if (item is IHeadered headered)
+                    hcc.Header = headered.Header;
+                else if (item is not Visual)
+                    hcc.Header = item;
+
+                if (ItemTemplate is { } it)
+                    hcc.HeaderTemplate = it;
+            }
+            else if (container is ContentControl cc)
+            {
+                cc.Content = item;
                 if (ItemTemplate is { } it)
-                    cc.SetValue(ContentControl.ContentTemplateProperty, it, BindingPriority.Template);
+                    cc.ContentTemplate = it;
             }
             else if (container is ContentPresenter p)
             {
-                p.SetValue(ContentPresenter.ContentProperty, item, BindingPriority.Template);
+                p.Content = item;
                 if (ItemTemplate is { } it)
-                    p.SetValue(ContentPresenter.ContentTemplateProperty, it, BindingPriority.Template);
+                    p.ContentTemplate = it;
             }
-
-            if (ItemContainerTheme is not null)
-                container.SetValue(ThemeProperty, ItemContainerTheme, BindingPriority.Template);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index d08e0a61da..952a9e448c 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -171,7 +171,15 @@ namespace Avalonia.Controls
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
         {
             base.PrepareContainerForItemOverride(element, item, index);
-            UpdateSelectedContent();
+            
+            if (element is HeaderedContentControl hcc && ContentTemplate is { } ct)
+                hcc.ContentTemplate = ct;
+
+            if (index == SelectedIndex && element is ContentControl container)
+            {
+                SelectedContentTemplate = container.ContentTemplate;
+                SelectedContent = container.Content;
+            }
         }
 
         protected override void ContainerIndexChangedOverride(Control container, int oldIndex, int newIndex)

From 2c4572a98eb1288b7e17bfb5c041dc0ea65a2f3b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:54:44 +0100
Subject: [PATCH 021/157] Attach to panel before preparing container.

---
 src/Avalonia.Controls/ItemsControl.cs               |  9 +++++++++
 .../Presenters/PanelContainerGenerator.cs           | 13 +++++++------
 src/Avalonia.Controls/VirtualizingStackPanel.cs     |  2 +-
 3 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 3de4017190..e9c959df6a 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -16,6 +16,7 @@ using Avalonia.Input;
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
 using Avalonia.Styling;
+using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
@@ -479,6 +480,14 @@ namespace Avalonia.Controls
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
+            // Putting this precondition in place in case we want to raise an event when a
+            // container is realized. If we want to do that, then the event subscriber will expect
+            // the container to be attached to the tree. Not using IsAttachedToVisualTree here
+            // because a bunch of tests don't have a rooted visual tree.
+            if (container.GetVisualParent() is null)
+                throw new InvalidOperationException(
+                    "Container must be attached to parent before PrepareItemContainer is called.");
+
             var itemContainerTheme = ItemContainerTheme;
 
             if (itemContainerTheme is not null && 
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index b080a9044f..f71a6c8c1b 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -70,10 +70,7 @@ namespace Avalonia.Controls.Presenters
             {
                 var i = index;
                 foreach (var item in items)
-                {
-                    children.Insert(i, CreateContainer(itemsControl, item, i));
-                    ++i;
-                }
+                    InsertContainer(itemsControl, children, item, i++);
 
                 var childCount = children.Count;
                 var delta = i - index;
@@ -124,7 +121,11 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        private static Control CreateContainer(ItemsControl itemsControl, object? item, int index)
+        private static void InsertContainer(
+            ItemsControl itemsControl,
+            Controls children,
+            object? item, 
+            int index)
         {
             var generator = itemsControl.ItemContainerGenerator;
             Control container;
@@ -140,8 +141,8 @@ namespace Avalonia.Controls.Presenters
             }
 
             itemsControl.AddLogicalChild(container);
+            children.Insert(index, container);
             generator.PrepareItemContainer(container, item, index);
-            return container;
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6373d5f3bd..115aff64c8 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -458,9 +458,9 @@ namespace Avalonia.Controls
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
+                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, item, index);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
-                    AddInternalChild(controlItem);
                     return controlItem;
                 }
             }

From 7e1068f4414dac497d54a888d6bded43f85e500d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 11:55:57 +0100
Subject: [PATCH 022/157] Fix test.

---
 tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index 25d93746d5..1eb13439a5 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -66,7 +66,7 @@ namespace Avalonia.Controls.UnitTests
         [Fact]
         public void Container_Should_Have_Theme_Set_To_ItemContainerTheme()
         {
-            var theme = new ControlTheme();
+            var theme = new ControlTheme { TargetType = typeof(ContentPresenter) };
             var target = new ItemsControl
             {
                 ItemContainerTheme = theme,

From 004103a925ebbcf4025d40ba2086ef48d25882d2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 12:26:11 +0100
Subject: [PATCH 023/157] Reimplement DisplayMemberBinding.

Use a slightly different approach to the one that was previously there: create an item template that contains `DisplayMemberBinding`. This is the approach that WPF broadly uses too.
---
 src/Avalonia.Controls/ItemsControl.cs         | 35 +++++++++++++++++--
 .../ItemsControlTests.cs                      | 25 +++++++++++++
 2 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e9c959df6a..a2fb21330c 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -83,6 +83,7 @@ namespace Avalonia.Controls
         private int _itemCount;
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
+        private IDataTemplate? _displayMemberItemTemplate;
 
         /// <summary>
         /// Initializes static members of the <see cref="ItemsControl"/> class.
@@ -291,19 +292,19 @@ namespace Avalonia.Controls
                 else if (item is not Visual)
                     hcc.Header = item;
 
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     hcc.HeaderTemplate = it;
             }
             else if (container is ContentControl cc)
             {
                 cc.Content = item;
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     cc.ContentTemplate = it;
             }
             else if (container is ContentPresenter p)
             {
                 p.Content = item;
-                if (ItemTemplate is { } it)
+                if (GetEffectiveItemTemplate() is { } it)
                     p.ContentTemplate = it;
             }
         }
@@ -431,6 +432,17 @@ namespace Avalonia.Controls
                 throw new NotImplementedException();
                 ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
             }
+            else if (change.Property == ItemTemplateProperty)
+            {
+                if (change.NewValue is not null && DisplayMemberBinding is not null)
+                    throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+            }
+            else if (change.Property == DisplayMemberBindingProperty)
+            {
+                if (change.NewValue is not null && ItemTemplate is not null)
+                    throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+                _displayMemberItemTemplate = null;
+            }
         }
 
         /// <summary>
@@ -568,6 +580,23 @@ namespace Avalonia.Controls
             }
         }
 
+        private IDataTemplate? GetEffectiveItemTemplate()
+        {
+            if (ItemTemplate is { } itemTemplate)
+                return itemTemplate;
+
+            if (_displayMemberItemTemplate is null && DisplayMemberBinding is { } binding)
+            {
+                _displayMemberItemTemplate = new FuncDataTemplate<object?>((_, _) =>
+                    new TextBlock
+                    {
+                        [!TextBlock.TextProperty] = binding,
+                    });
+            }
+
+            return _displayMemberItemTemplate;
+        }
+
         /// <summary>
         /// Called when the <see cref="ItemTemplate"/> changes.
         /// </summary>
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index 1eb13439a5..eeaef3c321 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -708,6 +708,31 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "3");
         }
 
+        [Fact]
+        public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_1()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                DisplayMemberBinding = new Binding("Length")
+            };
+
+            Assert.Throws<InvalidOperationException>(() => 
+                target.ItemTemplate = new FuncDataTemplate<string>((_, _) => new TextBlock()));
+        }
+
+        [Fact]
+        public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_2()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                ItemTemplate = new FuncDataTemplate<string>((_, _) => new TextBlock()),
+            };
+
+            Assert.Throws<InvalidOperationException>(() => target.DisplayMemberBinding = new Binding("Length"));
+        }
+
         private class Item
         {
             public Item(string value)

From a6423b258d2948d6b4074da91ebf4d883b786045 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 12:37:53 +0100
Subject: [PATCH 024/157] Fix failing test.

---
 tests/Avalonia.LeakTests/ControlTests.cs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/tests/Avalonia.LeakTests/ControlTests.cs b/tests/Avalonia.LeakTests/ControlTests.cs
index 4433e25c5a..59cc023509 100644
--- a/tests/Avalonia.LeakTests/ControlTests.cs
+++ b/tests/Avalonia.LeakTests/ControlTests.cs
@@ -713,6 +713,10 @@ namespace Avalonia.LeakTests
         {
             using (Start())
             {
+                // Height of ListBoxItem content + padding.
+                const double ListBoxItemHeight = 12;
+                const double TextBoxHeight = 25;
+
                 var items = new ObservableCollection<int>(Enumerable.Range(0, 10));
                 NameScope ns;
                 TextBox tb;
@@ -721,8 +725,8 @@ namespace Avalonia.LeakTests
                 {
                     [NameScope.NameScopeProperty] = ns = new NameScope(),
                     Width = 100,
-                    Height = 100,
-                    Content = new StackPanel
+                    Height = (items.Count * ListBoxItemHeight) + TextBoxHeight,
+                    Content = new DockPanel
                     {
                         Children =
                         {
@@ -730,6 +734,8 @@ namespace Avalonia.LeakTests
                             {
                                 Name = "tb",
                                 Text = "foo",
+                                Height = TextBoxHeight,
+                                [DockPanel.DockProperty] = Dock.Top,
                             }),
                             (lb = new ListBox
                             {
@@ -745,7 +751,8 @@ namespace Avalonia.LeakTests
                                             Path = "Text",
                                             NameScope = new WeakReference<INameScope>(ns),
                                         }
-                                    })
+                                    }),
+                                Padding = new Thickness(0),
                             }),
                         }
                     }

From 2ae5c9c0fe1cceab04d4296334d16ae48fa8559d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 15:55:03 +0100
Subject: [PATCH 025/157] Reimplement IChildIndexProvider.

---
 src/Avalonia.Controls/ItemsControl.cs         | 39 ++++++-------------
 .../VirtualizingStackPanel.cs                 |  2 +-
 .../Xaml/StyleTests.cs                        |  5 ++-
 3 files changed, 16 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index a2fb21330c..b6d74da06e 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -84,6 +84,7 @@ namespace Avalonia.Controls
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
+        private Tuple<int, Control>? _containerBeingPrepared;
 
         /// <summary>
         /// Initializes static members of the <see cref="ItemsControl"/> class.
@@ -221,19 +222,8 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
         {
-            if (Presenter is IChildIndexProvider oldInnerProvider)
-            {
-                oldInnerProvider.ChildIndexChanged -= PresenterChildIndexChanged;
-            }
-
             Presenter = presenter;
-            ////ItemContainerGenerator?.Clear();
-
-            if (Presenter is IChildIndexProvider innerProvider)
-            {
-                innerProvider.ChildIndexChanged += PresenterChildIndexChanged;
-                _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-            }
+            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
         }
 
         void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
@@ -513,11 +503,16 @@ namespace Avalonia.Controls
                 container.DataContext = item;
 
             PrepareContainerForItemOverride(container, item, index);
+
+            _containerBeingPrepared = new(index, container);
+            _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
+            _containerBeingPrepared = null;
         }
 
         internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
         {
             ContainerIndexChangedOverride(container, oldIndex, newIndex);
+            _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
         }
 
         /// <summary>
@@ -681,27 +676,17 @@ namespace Avalonia.Controls
             }
         }
 
-        private void PresenterChildIndexChanged(object? sender, ChildIndexChangedEventArgs e)
-        {
-            _childIndexChanged?.Invoke(this, e);
-        }
-
         int IChildIndexProvider.GetChildIndex(ILogical child)
         {
-            return Presenter is IChildIndexProvider innerProvider
-                ? innerProvider.GetChildIndex(child) : -1;
+            if (_containerBeingPrepared?.Item2 == child)
+                return _containerBeingPrepared.Item1;
+
+            return child is Control container ? IndexFromContainer(container) : -1;
         }
 
         bool IChildIndexProvider.TryGetTotalCount(out int count)
         {
-            if (Presenter is IChildIndexProvider presenter
-                && presenter.TryGetTotalCount(out count))
-            {
-                return true;
-            }
-
-            count = ItemCount;
-            return true;
+            return Items.TryGetCountFast(out count);
         }
     }
 }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 115aff64c8..f211ec2edb 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -830,7 +830,7 @@ namespace Avalonia.Controls
                     for (var i = start; i < end; ++i)
                     {
                         if (_elements[i] is Control element)
-                            updateElementIndex(element, newIndex - count, newIndex);
+                            updateElementIndex(element, newIndex + count, newIndex);
                         ++newIndex;
                     }
                 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 6361dcdbea..70cf3c8276 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -349,7 +349,6 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             }
         }
 
-
         [Fact]
         public void Style_Can_Use_NthChild_Selector_With_ListBox()
         {
@@ -376,16 +375,18 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
                 window.Show();
 
-                IEnumerable<IBrush> GetColors() => list.Presenter.Panel.Children.Cast<ListBoxItem>().Select(t => t.Background);
+                IEnumerable<IBrush> GetColors() => list.GetRealizedContainers().Cast<ListBoxItem>().Select(t => t.Background);
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Green, Brushes.Transparent }, GetColors());
 
                 collection.Remove(Brushes.Green);
+                window.LayoutManager.ExecuteLayoutPass();
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Blue }, GetColors());
 
                 collection.Add(Brushes.Violet);
                 collection.Add(Brushes.Black);
+                window.LayoutManager.ExecuteLayoutPass();
 
                 Assert.Equal(new[] { Brushes.Transparent, Brushes.Blue, Brushes.Transparent, Brushes.Black }, GetColors());
             }

From 000f393be74a6e9e498a5f86c9f5004e9639879c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:10:48 +0100
Subject: [PATCH 026/157] Refresh containers when relevant property changes.

When `ItemsControl.DisplayMemberBinding` or `ItemTemplate` changes, refresh the containers.
---
 src/Avalonia.Controls/ItemsControl.cs         | 10 ++++
 .../Presenters/ItemsPresenter.cs              |  8 +++
 .../Presenters/PanelContainerGenerator.cs     |  2 +
 src/Avalonia.Controls/VirtualizingPanel.cs    |  4 +-
 .../ItemsControlTests.cs                      | 58 +++++++++++++++++++
 5 files changed, 81 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b6d74da06e..31f8f31875 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -426,12 +426,14 @@ namespace Avalonia.Controls
             {
                 if (change.NewValue is not null && DisplayMemberBinding is not null)
                     throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
+                RefreshContainers();
             }
             else if (change.Property == DisplayMemberBindingProperty)
             {
                 if (change.NewValue is not null && ItemTemplate is not null)
                     throw new InvalidOperationException("Cannot set both DisplayMemberBinding and ItemTemplate.");
                 _displayMemberItemTemplate = null;
+                RefreshContainers();
             }
         }
 
@@ -455,6 +457,14 @@ namespace Avalonia.Controls
             SubscribeToItems(newValue);
         }
 
+        /// <summary>
+        /// Refreshes the containers displayed by the control.
+        /// </summary>
+        /// <remarks>
+        /// Causes all containers to be unrealized and re-realized.
+        /// </remarks>
+        protected void RefreshContainers() => Presenter?.Refresh();
+
         /// <summary>
         /// Called when the <see cref="INotifyCollectionChanged.CollectionChanged"/> event is
         /// raised on <see cref="Items"/>.
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 6f27349cc1..f11d803fc5 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -84,6 +84,14 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
+        internal void Refresh()
+        {
+            if (Panel is VirtualizingPanel v)
+                v.Refresh();
+            else
+                _generator?.Refresh();
+        }
+
         private void ResetState()
         {
             _generator?.Dispose();
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index f71a6c8c1b..8d1e7f0b96 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -45,6 +45,8 @@ namespace Avalonia.Controls.Presenters
             _presenter.Panel?.Children.Clear();
         }
 
+        internal void Refresh() => OnItemsChanged(null, CollectionUtils.ResetEventArgs);
+
         private void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == ItemsControl.ItemsProperty)
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 0b7a183728..0d0abe148d 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -176,6 +176,8 @@ namespace Avalonia.Controls
             Children.Clear();
         }
 
+        internal void Refresh() => OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+
         private ItemsControl EnsureItemsControl()
         {
             if (ItemsControl is null)
@@ -189,7 +191,7 @@ namespace Avalonia.Controls
             {
                 if (e.OldValue is INotifyCollectionChanged inccOld)
                     inccOld.CollectionChanged -= OnItemsControlItemsChanged;
-                OnItemsControlItemsChanged(null, CollectionUtils.ResetEventArgs);
+                Refresh();
                 if (e.NewValue is INotifyCollectionChanged inccNew)
                     inccNew.CollectionChanged += OnItemsControlItemsChanged;
             }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
index eeaef3c321..28e88d1e71 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsControlTests.cs
@@ -35,6 +35,31 @@ namespace Avalonia.Controls.UnitTests
             Assert.IsType<Canvas>(container.Child);
         }
 
+        [Fact]
+        public void ItemTemplate_Can_Be_Changed()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas()),
+            };
+
+            target.Items = new[] { "Foo" };
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.IsType<Canvas>(container.Child);
+
+            target.ItemTemplate = new FuncDataTemplate<string>((_, __) => new Border());
+            container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.IsType<Border>(container.Child);
+        }
+
         [Fact]
         public void Panel_Should_Have_TemplatedParent_Set_To_ItemsControl()
         {
@@ -708,6 +733,32 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "3");
         }
 
+        [Fact]
+        public void DisplayMemberBinding_Can_Be_Changed()
+        {
+            var target = new ItemsControl
+            {
+                Template = GetTemplate(),
+                DisplayMemberBinding = new Binding("Value")
+            };
+
+            target.Items = new[] { new Item("Foo", "Bar") };
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "Bar");
+
+            target.DisplayMemberBinding = new Binding("Caption");
+            
+            container = (ContentPresenter)target.Presenter.Panel.Children[0];
+            container.UpdateChild();
+
+            Assert.Equal(container.Child!.GetValue(TextBlock.TextProperty), "Foo");
+        }
+
         [Fact]
         public void Cannot_Set_Both_DisplayMemberBinding_And_ItemTemplate_1()
         {
@@ -740,6 +791,13 @@ namespace Avalonia.Controls.UnitTests
                 Value = value;
             }
 
+            public Item(string caption, string value)
+            {
+                Caption = caption;
+                Value = value;
+            }
+
+            public string Caption { get; }
             public string Value { get; }
         }
 

From 1950e4b0a3f4c200bc944fd6c07fcbc11351b524 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:12:12 +0100
Subject: [PATCH 027/157] Remove TabControl.HeaderDisplayMemberBinding.

As `DisplayMemberBinding` should select the member for the header (in WPF it's `DisplayMemberPath`). Also set `TabItem.TabStripPlacement`.
---
 .../ControlCatalog/Pages/TabControlPage.xaml  |  2 +-
 src/Avalonia.Controls/TabControl.cs           | 32 ++++++++-----------
 2 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/samples/ControlCatalog/Pages/TabControlPage.xaml b/samples/ControlCatalog/Pages/TabControlPage.xaml
index e289de90f9..a775056ebe 100644
--- a/samples/ControlCatalog/Pages/TabControlPage.xaml
+++ b/samples/ControlCatalog/Pages/TabControlPage.xaml
@@ -53,7 +53,7 @@
                 <TabControl
                     Items="{Binding Tabs}"
                     Margin="0 16"
-                    HeaderDisplayMemberBinding="{Binding Header, x:DataType=viewModels:TabControlPageViewModelItem}"
+                    DisplayMemberBinding="{Binding Header, x:DataType=viewModels:TabControlPageViewModelItem}"
                     TabStripPlacement="{Binding TabPlacement}">
                     <TabControl.ContentTemplate>
                         <DataTemplate x:DataType="viewModels:TabControlPageViewModelItem">
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index 952a9e448c..a6085e53cd 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -57,12 +57,6 @@ namespace Avalonia.Controls
         /// </summary>
         public static readonly StyledProperty<IDataTemplate?> SelectedContentTemplateProperty =
             AvaloniaProperty.Register<TabControl, IDataTemplate?>(nameof(SelectedContentTemplate));
-
-        /// <summary>
-        /// Defines the <see cref="HeaderDisplayMemberBinding" /> property
-        /// </summary>
-        public static readonly StyledProperty<IBinding?> HeaderDisplayMemberBindingProperty =
-            AvaloniaProperty.Register<HeaderedItemsControl, IBinding?>(nameof(HeaderDisplayMemberBinding));
         
         /// <summary>
         /// The default value for the <see cref="ItemsControl.ItemsPanel"/> property.
@@ -141,16 +135,6 @@ namespace Avalonia.Controls
             get { return GetValue(SelectedContentTemplateProperty); }
             internal set { SetValue(SelectedContentTemplateProperty, value); }
         }
-        
-        /// <summary>
-        /// Gets or sets the <see cref="IBinding"/> to use for binding to the display member of each tab-items header.
-        /// </summary>
-        [AssignBinding]
-        public IBinding? HeaderDisplayMemberBinding
-        {
-            get { return GetValue(HeaderDisplayMemberBindingProperty); }
-            set { SetValue(HeaderDisplayMemberBindingProperty, value); }
-        }
 
         internal ItemsPresenter? ItemsPresenterPart { get; private set; }
 
@@ -172,8 +156,12 @@ namespace Avalonia.Controls
         {
             base.PrepareContainerForItemOverride(element, item, index);
             
-            if (element is HeaderedContentControl hcc && ContentTemplate is { } ct)
-                hcc.ContentTemplate = ct;
+            if (element is TabItem tabItem)
+            {
+                if (ContentTemplate is { } ct)
+                    tabItem.ContentTemplate = ct;
+                tabItem.SetValue(TabStripPlacementProperty, TabStripPlacement);
+            }
 
             if (index == SelectedIndex && element is ContentControl container)
             {
@@ -268,5 +256,13 @@ namespace Avalonia.Controls
                 }
             }
         }
+
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == TabStripPlacementProperty)
+                RefreshContainers();
+        }
     }
 }

From 306c0454935d400465c397debf024f4c5b82ed5c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:38:19 +0100
Subject: [PATCH 028/157] Reinstate some commented-out code.

---
 src/Avalonia.Controls/ComboBox.cs     | 17 ++++++++---------
 src/Avalonia.Controls/ItemsControl.cs |  3 +--
 src/Avalonia.Controls/MenuBase.cs     | 11 +----------
 3 files changed, 10 insertions(+), 21 deletions(-)

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index e6af255c29..a573a9d887 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -440,15 +440,14 @@ namespace Avalonia.Controls
 
         private void SelectFocusedItem()
         {
-            throw new NotImplementedException();
-            ////foreach (ItemContainerInfo dropdownItem in ItemContainerGenerator.Containers)
-            ////{
-            ////    if (dropdownItem.ContainerControl.IsFocused)
-            ////    {
-            ////        SelectedIndex = dropdownItem.Index;
-            ////        break;
-            ////    }
-            ////}
+            foreach (var dropdownItem in GetRealizedContainers())
+            {
+                if (dropdownItem.IsFocused)
+                {
+                    SelectedIndex = IndexFromContainer(dropdownItem);
+                    break;
+                }
+            }
         }
 
         private void SelectNext()
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 31f8f31875..e07eea57ef 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -419,8 +419,7 @@ namespace Avalonia.Controls
             }
             else if (change.Property == ItemContainerThemeProperty && _itemContainerGenerator is not null)
             {
-                throw new NotImplementedException();
-                ////_itemContainerGenerator.ItemContainerTheme = change.GetNewValue<ControlTheme?>();
+                RefreshContainers();
             }
             else if (change.Property == ItemTemplateProperty)
             {
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index 3b211d4cc7..3bbd5b7de4 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -95,16 +95,7 @@ namespace Avalonia.Controls
         }
 
         /// <inheritdoc/>
-        IEnumerable<IMenuItem> IMenuElement.SubItems
-        {
-            get
-            {
-                throw new NotImplementedException();
-                ////return ItemContainerGenerator.Containers
-                ////    .Select(x => x.ContainerControl)
-                ////    .OfType<IMenuItem>();
-            }
-        }
+        IEnumerable<IMenuItem> IMenuElement.SubItems => GetRealizedContainers().OfType<IMenuItem>();
 
         /// <summary>
         /// Gets the interaction handler for the menu.

From a7a71034b03e6720e80926b4c3a11a1b997eef5a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 1 Dec 2022 22:38:49 +0100
Subject: [PATCH 029/157] Remove unneeded tests.

---
 .../ItemsPresenterTests_Virtualization.cs     |  374 ------
 ...emsPresenterTests_Virtualization_Simple.cs | 1110 -----------------
 2 files changed, 1484 deletions(-)
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs

diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
deleted file mode 100644
index d0798d469f..0000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization.cs
+++ /dev/null
@@ -1,374 +0,0 @@
-////using System;
-////using System.Collections.Generic;
-////using System.Linq;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Layout;
-////using Avalonia.Platform;
-////using Avalonia.Rendering;
-////using Avalonia.UnitTests;
-////using Avalonia.VisualTree;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class ItemsPresenterTests_Virtualization
-////    {
-////        [Fact]
-////        public void Should_Not_Create_Items_Before_Added_To_Visual_Tree()
-////        {
-////            var items = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var target = new TestItemsPresenter(true)
-////            {
-////                Items = items,
-////                ItemsPanel = VirtualizingPanelTemplate(Orientation.Vertical),
-////                ItemTemplate = ItemTemplate(),
-////                VirtualizationMode = ItemVirtualizationMode.Simple,
-////            };
-
-////            var scroller = new ScrollContentPresenter
-////            {
-////                Content = target,
-////            };
-
-////            scroller.UpdateChild();
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Empty(target.Panel.Children);
-
-////            var root = new TestRoot
-////            {
-////                Child = scroller,
-////            };
-
-////            target.InvalidateMeasure();
-////            target.Panel.InvalidateMeasure();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_Has_No_Virtualizing_Panel()
-////        {
-////            var target = CreateTarget();
-////            target.ClearValue(ItemsPresenter.ItemsPanelProperty);
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_VirtualizationMode_None()
-////        {
-////            var target = CreateTarget(ItemVirtualizationMode.None);
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_False_When_Doesnt_Have_ScrollPresenter_Parent()
-////        {
-////            var target = new ItemsPresenter
-////            {
-////                ItemsPanel = VirtualizingPanelTemplate(),
-////                ItemTemplate = ItemTemplate(),
-////                VirtualizationMode = ItemVirtualizationMode.Simple,
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.False(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Should_Return_IsLogicalScrollEnabled_True()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            Assert.True(((ILogicalScrollable)target).IsLogicalScrollEnabled);
-////        }
-
-////        [Fact]
-////        public void Parent_ScrollContentPresenter_Properties_Should_Be_Set()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var scroll = (ScrollContentPresenter)target.Parent;
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Fill_Panel_With_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            target.Measure(new Size(100, 100));
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Arrange(new Rect(0, 0, 100, 100));
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Only_Create_Enough_Containers_To_Display_All_Items()
-////        {
-////            var target = CreateTarget(itemCount: 2);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(2, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Expand_To_Fit_Containers_When_Flexible_Size()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(Size.Infinity);
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(new Size(10, 200), target.DesiredSize);
-////            Assert.Equal(new Size(10, 200), target.Bounds.Size);
-////            Assert.Equal(20, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Initial_Item_DataContexts_Should_Be_Correct()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Add_New_Items_When_Control_Is_Enlarged()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Measure(new Size(120, 120));
-////            target.Arrange(new Rect(0, 0, 100, 120));
-
-////            Assert.Equal(12, target.Panel.Children.Count);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Not_Create_Virtualizer_Before_Panel()
-////        {
-////            var target = CreateTarget();
-
-////            Assert.Null(target.Panel);
-////            Assert.Null(target.Virtualizer);
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_None_To_Simple_Should_Update_Control()
-////        {
-////            var target = CreateTarget(mode: ItemVirtualizationMode.None);
-////            var scroll = (ScrollContentPresenter)target.Parent;
-
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(20, target.Panel.Children.Count);
-////            Assert.Equal(new Size(100, 200), scroll.Extent);
-////            Assert.Equal(new Size(100, 100), scroll.Viewport);
-
-////            target.VirtualizationMode = ItemVirtualizationMode.Simple;
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_None_To_Simple_Should_Add_Correct_Number_Of_Controls()
-////        {
-////            using (UnitTestApplication.Start(new TestServices()))
-////            {
-////                var target = CreateTarget(mode: ItemVirtualizationMode.None);
-////                var scroll = (TestScroller)target.Parent;
-
-////                scroll.Width = scroll.Height = 100;
-////                scroll.LayoutManager.ExecuteInitialLayoutPass();
-
-////                // Ensure than an intermediate measure pass doesn't add more controls than it
-////                // should. This can happen if target gets measured with Size.Infinity which
-////                // is what the available size should be when VirtualizationMode == None but not
-////                // what it should after VirtualizationMode is changed to Simple.
-////                target.Panel.Children.CollectionChanged += (s, e) =>
-////                {
-////                    Assert.InRange(target.Panel.Children.Count, 0, 10);
-////                };
-
-////                target.VirtualizationMode = ItemVirtualizationMode.Simple;
-////                ((ILayoutRoot)scroll.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
-
-////                Assert.Equal(10, target.Panel.Children.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Changing_VirtualizationMode_Simple_To_None_Should_Update_Control()
-////        {
-////            var target = CreateTarget();
-////            var scroll = (ScrollContentPresenter)target.Parent;
-
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////            Assert.Equal(new Size(10, 20), scroll.Extent);
-////            Assert.Equal(new Size(100, 10), scroll.Viewport);
-
-////            target.VirtualizationMode = ItemVirtualizationMode.None;
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            // Here - unlike changing the other way - we need to do a layout pass on the scroll
-////            // content presenter as non-logical scroll values are only updated on arrange.
-////            scroll.Measure(new Size(100, 100));
-////            scroll.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(20, target.Panel.Children.Count);
-////            Assert.Equal(new Size(100, 200), scroll.Extent);
-////            Assert.Equal(new Size(100, 100), scroll.Viewport);
-////        }
-
-////        private static ItemsPresenter CreateTarget(
-////            ItemVirtualizationMode mode = ItemVirtualizationMode.Simple,
-////            Orientation orientation = Orientation.Vertical,
-////            bool useContainers = true,
-////            int itemCount = 20)
-////        {
-////            ItemsPresenter result;
-////            var items = Enumerable.Range(0, itemCount).Select(x => $"Item {x}").ToList();
-
-////            var scroller = new TestScroller
-////            {
-////                CanHorizontallyScroll = false,
-////                CanVerticallyScroll = true,
-////                Content = result = new TestItemsPresenter(useContainers)
-////                {
-////                    Items = items,
-////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-////                    ItemTemplate = ItemTemplate(),
-////                    VirtualizationMode = mode,
-////                }
-////            };
-
-////            scroller.UpdateChild();
-
-////            return result;
-////        }
-
-////        private static IDataTemplate ItemTemplate()
-////        {
-////            return new FuncDataTemplate<string>((x, _) => new Canvas
-////            {
-////                Width = 10,
-////                Height = 10,
-////            });
-////        }
-
-////        private static ITemplate<Panel> VirtualizingPanelTemplate(
-////            Orientation orientation = Orientation.Vertical)
-////        {
-////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-////            {
-////                Orientation = orientation,
-////            });
-////        }
-
-////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot
-////        {
-////            public TestScroller()
-////            {
-////                LayoutManager = new LayoutManager(this);
-////            }
-
-////            public IRenderer Renderer { get; }
-////            public Size ClientSize { get; }
-////            public double RenderScaling => 1;
-
-////            public Size MaxClientSize => Size.Infinity;
-
-////            public double LayoutScaling => 1;
-
-////            public ILayoutManager LayoutManager { get; }
-
-////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-////            public void Invalidate(Rect rect) => throw new NotImplementedException();
-////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-////        }
-
-////        private class TestItemsPresenter : ItemsPresenter
-////        {
-////            private bool _useContainers;
-
-////            public TestItemsPresenter(bool useContainers)
-////            {
-////                _useContainers = useContainers;
-////            }
-
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return _useContainers ?
-////                    new ItemContainerGenerator<TestContainer>(this, TestContainer.ContentProperty, null) :
-////                    new ItemContainerGenerator(this);
-////            }
-////        }
-
-////        private class TestContainer : ContentControl
-////        {
-////            public TestContainer()
-////            {
-////                Width = 10;
-////                Height = 10;
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
deleted file mode 100644
index 131b86e4b1..0000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
+++ /dev/null
@@ -1,1110 +0,0 @@
-////using System;
-////using System.Collections;
-////using System.Collections.Generic;
-////using System.Collections.ObjectModel;
-////using System.Linq;
-////using Avalonia.Collections;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Primitives;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Input;
-////using Avalonia.Layout;
-////using Avalonia.LogicalTree;
-////using Avalonia.Platform;
-////using Avalonia.Rendering;
-////using Avalonia.Styling;
-////using Avalonia.UnitTests;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class ItemsPresenterTests_Virtualization_Simple
-////    {
-////        [Fact]
-////        public void Should_Return_Items_Count_For_Extent_Vertical()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(new Size(0, 20), ((ILogicalScrollable)target).Extent);
-////        }
-
-////        [Fact]
-////        public void Should_Return_Items_Count_For_Extent_Horizontal()
-////        {
-////            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(new Size(20, 0), ((ILogicalScrollable)target).Extent);
-////        }
-
-////        [Fact]
-////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Vertical()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(new Size(100, 10), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Have_Number_Of_Visible_Items_As_Viewport_Horizontal()
-////        {
-////            var target = CreateTarget(orientation: Orientation.Horizontal);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(new Size(10, 100), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Should_Add_Containers_When_Panel_Is_Not_Full()
-////        {
-////            var target = CreateTarget(itemCount: 5);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(5, target.Panel.Children.Count);
-
-////            items.Add("New Item");
-
-////            Assert.Equal(6, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Remove_Items_When_Control_Is_Shrank()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            target.Measure(new Size(100, 80));
-////            target.Arrange(new Rect(0, 0, 100, 80));
-
-////            Assert.Equal(8, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Add_New_Containers_At_Top_When_Control_Is_Scrolled_To_Bottom_And_Enlarged()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            ((IScrollable)target).Offset = new Vector(0, 10);
-////            target.Measure(new Size(120, 120));
-////            target.Arrange(new Rect(0, 0, 100, 120));
-
-////            Assert.Equal(12, target.Panel.Children.Count);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 8], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Should_Update_Containers_When_Items_Changes()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            target.Items = new[] { "foo", "bar", "baz" };
-
-////            Assert.Equal(3, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Should_Decrease_The_Viewport_Size_By_One_If_There_Is_A_Partial_Item()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            Assert.Equal(new Size(100, 9), ((ILogicalScrollable)target).Viewport);
-////        }
-
-////        [Fact]
-////        public void Moving_To_And_From_The_End_With_Partial_Item_Should_Set_Panel_PixelOffset()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////            var minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////            minIndex = target.ItemContainerGenerator.Containers.Min(x => x.Index);
-////            Assert.Equal(new Vector(0, 11), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(10, minIndex);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-////        }
-
-////        [Fact]
-////        public void Inserting_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Insert(6, "Inserted");
-////            expected.Insert(1, "Inserted");
-////            expected.RemoveAt(expected.Count - 1);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Inserting_Items_Before_Visibile_Containers_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(5, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Insert(0, "Inserted");
-
-////            expected = Enumerable.Range(4, 10).Select(x => $"Item {x}").ToList();
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_First_Materialized_Item_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveAt(0);
-////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_From_Middle_Should_Update_Containers_When_All_Items_Visible()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 200));
-////            target.Arrange(new Rect(0, 0, 100, 200));
-
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(items, actual);
-
-////            items.RemoveAt(2);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(items, actual);
-
-////            items.RemoveAt(items.Count - 2);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(items, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Last_Item_Should_Update_Containers_When_All_Items_Visible()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 200));
-////            target.Arrange(new Rect(0, 0, 100, 200));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 5);
-
-////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Remove(items.Last());
-////            expected.Remove(expected.Last());
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_When_Scrolled_To_End_Should_Recyle_Containers_At_Top()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            var expected = Enumerable.Range(10, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveRange(18, 2);
-////            expected = Enumerable.Range(8, 10).Select(x => $"Item {x}").ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Removing_Items_When_Scrolled_To_Near_End_Should_Recycle_Containers_At_Bottom_And_Top()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 9);
-
-////            var expected = Enumerable.Range(9, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.RemoveRange(15, 3);
-////            expected = Enumerable.Range(7, 8).Select(x => $"Item {x}")
-////                .Concat(Enumerable.Range(18, 2).Select(x => $"Item {x}"))
-////                .ToList();
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Measuring_To_Infinity_When_Scrolled_To_End_Should_Not_Throw()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 10);
-
-////            // Check for issue #589: this should not throw.
-////            target.Measure(Size.Infinity);
-
-////            var expected = Enumerable.Range(0, 20).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Replacing_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items[4] = expected[4] = "Replaced";
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Moving_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            items.Move(4, 8);
-////            var i = expected[4];
-////            expected.RemoveAt(4);
-////            expected.Insert(8, i);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Setting_Items_To_Null_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget();
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            target.Items = null;
-
-////            Assert.Empty(target.Panel.Children);
-////        }
-
-////        [Fact]
-////        public void Reassigning_Items_Should_Create_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 5);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Inserting_Then_Removing_Should_Add_Remove_Containers()
-////        {
-////            var items = new AvaloniaList<string>(Enumerable.Range(0, 5).Select(x => $"Item {x}"));
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"Added Item {x}").ToArray();
-////            var target = new ItemsPresenter
-////            {
-////                VirtualizationMode = ItemVirtualizationMode.None,
-////                Items = items,
-////                ItemTemplate = new FuncDataTemplate<string>((x, _) => new TextBlock { Height = 10 }),
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-////            int addIndex = 1;
-////            foreach (var item in toAdd)
-////            {
-////                items.Insert(addIndex++, item);
-////            }
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-
-////            foreach (var item in toAdd)
-////            {
-////                items.Remove(item);
-////            }
-
-////            Assert.Equal(items.Count, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Reassigning_Items_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 6);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Clearing_Items_And_ReAdding_Should_Remove_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 6);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 6).Select(x => $"Item {x}").ToList();
-////            var items = (ObservableCollection<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            expected = Enumerable.Range(0, 5).Select(x => $"Item {x}").ToList();
-////            target.Items = null;
-////            target.Items = expected;
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Scrolling_To_Partial_Last_Item_Then_Adding_Item_Updates_Containers()
-////        {
-////            var target = CreateTarget(itemCount: 10);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 95));
-////            target.Arrange(new Rect(0, 0, 100, 95));
-
-////            ((ILogicalScrollable)target).Offset = new Vector(0, 1);
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////            Assert.Equal(10, ((IVirtualizingPanel)target.Panel).PixelOffset);
-
-////            items.Add("Item 10");
-
-////            expected = Enumerable.Range(1, 10).Select(x => $"Item {x}").ToList();
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////            Assert.Equal(0, ((IVirtualizingPanel)target.Panel).PixelOffset);
-////        }
-
-////        [Fact]
-////        public void Scrolling_To_Item_In_Zero_Sized_Presenter_Doesnt_Throw()
-////        {
-////            using (UnitTestApplication.Start(new TestServices()))
-////            {
-////                var target = CreateTarget(itemCount: 10);
-////                var items = (IList<string>)target.Items;
-////                target.ApplyTemplate();
-////                target.Measure(Size.Empty);
-////                target.Arrange(Rect.Empty);
-
-////                // Check for issue #591: this should not throw.
-////                target.ScrollIntoView(0);
-////            }
-////        }
-
-////        [Fact]
-////        public void InsertRange_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
-
-////            int index = 1;
-
-////            items.InsertRange(index, toAdd);
-////            expected.InsertRange(index, toAdd);
-////            expected.RemoveRange(10, toAdd.Count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void InsertRange_Items_Before_Last_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 10).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected, actual);
-
-////            var toAdd = Enumerable.Range(0, 3).Select(x => $"New Item {x}").ToList();
-
-////            int index = 8;
-
-////            items.InsertRange(index, toAdd);
-////            expected.InsertRange(index, toAdd);
-////            expected.RemoveRange(10, toAdd.Count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void RemoveRange_Items_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected.Take(10), actual);
-
-////            int index = 5;
-////            int count = 3;
-
-////            items.RemoveRange(index, count);
-////            expected.RemoveRange(index, count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void RemoveRange_Items_Before_Last_Should_Update_Containers()
-////        {
-////            var target = CreateTarget(useAvaloniaList: true);
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var expected = Enumerable.Range(0, 13).Select(x => $"Item {x}").ToList();
-////            var items = (AvaloniaList<string>)target.Items;
-////            var actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            Assert.Equal(expected.Take(10), actual);
-
-////            int index = 8;
-////            int count = 3;
-
-////            items.RemoveRange(index, count);
-////            expected.RemoveRange(index, count);
-
-////            actual = target.Panel.Children.Select(x => x.DataContext).ToList();
-////            Assert.Equal(expected, actual);
-////        }
-
-////        [Fact]
-////        public void Should_Add_Containers_For_Items_After_Clear()
-////        {
-////            var target = CreateTarget(itemCount: 10);
-////            var defaultItems = (IList<string>)target.Items;
-////            var items = new AvaloniaList<string>(defaultItems);
-////            target.Items = items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-
-////            items.Clear();
-
-////            target.Panel.Measure(new Size(100, 100));
-////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
-
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Empty(target.Panel.Children);
-
-////            items.AddRange(defaultItems.Select(s => s + " new"));
-
-////            target.Panel.Measure(new Size(100, 100));
-////            target.Panel.Arrange(new Rect(target.Panel.DesiredSize));
-
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(target.DesiredSize));
-
-////            Assert.Equal(10, target.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Scroll_To_Last_Should_Work()
-////        {
-////            var target = CreateTarget(itemCount: 11);
-////            var scroller = (TestScroller)target.Parent;
-
-////            scroller.Width = scroller.Height = 100;
-////            scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////            var last = (target.Items as IList)[10];
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-////        }
-
-////        [Fact]
-////        public void Second_Scroll_To_Last_Should_Work()
-////        {
-////            var target = CreateTarget(itemCount: 11);
-////            var scroller = (TestScroller)target.Parent;
-
-////            scroller.Width = scroller.Height = 100;
-////            scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////            var last = (target.Items as IList)[10];
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-
-////            target.ScrollIntoView(10);
-
-////            Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////            Assert.Same(target.Panel.Children[9].DataContext, last);
-////        }
-
-////        [Fact]
-////        public void Scrolling_Less_Than_A_Page_Should_Move_Recycled_Items()
-////        {
-////            var target = CreateTarget();
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var containers = target.Panel.Children.ToList();
-////            var scroller = (ScrollContentPresenter)target.Parent;
-
-////            scroller.Offset = new Vector(0, 5);
-
-////            var scrolledContainers = containers
-////                .Skip(5)
-////                .Take(5)
-////                .Concat(containers.Take(5)).ToList();
-
-////            Assert.Equal(new Vector(0, 5), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(scrolledContainers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 5], target.Panel.Children[i].DataContext);
-////            }
-
-////            scroller.Offset = new Vector(0, 0);
-////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            var dcs = target.Panel.Children.Select(x => x.DataContext).ToList();
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        [Fact]
-////        public void Scrolling_More_Than_A_Page_Should_Recycle_Items()
-////        {
-////            var target = CreateTarget(itemCount: 50);
-////            var items = (IList<string>)target.Items;
-
-////            target.ApplyTemplate();
-////            target.Measure(new Size(100, 100));
-////            target.Arrange(new Rect(0, 0, 100, 100));
-
-////            var containers = target.Panel.Children.ToList();
-////            var scroller = (ScrollContentPresenter)target.Parent;
-
-////            scroller.Offset = new Vector(0, 20);
-
-////            Assert.Equal(new Vector(0, 20), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i + 20], target.Panel.Children[i].DataContext);
-////            }
-
-////            scroller.Offset = new Vector(0, 0);
-
-////            Assert.Equal(new Vector(0, 0), ((ILogicalScrollable)target).Offset);
-////            Assert.Equal(containers, target.Panel.Children);
-
-////            for (var i = 0; i < target.Panel.Children.Count; ++i)
-////            {
-////                Assert.Equal(items[i], target.Panel.Children[i].DataContext);
-////            }
-////        }
-
-////        public class Vertical
-////        {
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Return_Existing_Container_If_Materialized()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[5];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Same(target.Panel.Children[6], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Scroll_If_Necessary()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[9];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[9], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Down_Should_Scroll_If_Partially_Visible()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 100;
-////                scroller.Height = 95;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[8];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Down,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 1), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[8], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Up_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-////            {
-////                var target = CreateTarget();
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 100;
-////                scroller.Height = 95;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-////                ((ILogicalScrollable)target).Offset = new Vector(0, 11);
-
-////                var from = target.Panel.Children[1];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Up,
-////                    from);
-
-////                Assert.Equal(new Vector(0, 10), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[0], result);
-////            }
-
-////            [Fact]
-////            public void Should_Return_Horizontal_Extent_And_Viewport()
-////            {
-////                var target = CreateTarget();
-
-////                target.ApplyTemplate();
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                Assert.Equal(new Size(10, 20), ((ILogicalScrollable)target).Extent);
-////                Assert.Equal(new Size(5, 10), ((ILogicalScrollable)target).Viewport);
-////            }
-
-////            [Fact]
-////            public void Horizontal_Scroll_Should_Update_Item_Position()
-////            {
-////                var target = CreateTarget();
-
-////                target.ApplyTemplate();
-
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                ((ILogicalScrollable)target).Offset = new Vector(5, 0);
-
-////                target.Measure(new Size(5, 100));
-////                target.Arrange(new Rect(0, 0, 5, 100));
-
-////                Assert.Equal(new Rect(-5, 0, 10, 10), target.Panel.Children[0].Bounds);
-////            }
-////        }
-
-////        public class Horizontal
-////        {
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Return_Existing_Container_If_Materialized()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[5];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Same(target.Panel.Children[6], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Scroll_If_Necessary()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[9];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[9], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Right_Should_Scroll_If_Partially_Visible()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 95;
-////                scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-
-////                var from = target.Panel.Children[8];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Right,
-////                    from);
-
-////                Assert.Equal(new Vector(1, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[8], result);
-////            }
-
-////            [Fact]
-////            public void GetControlInDirection_Left_Should_Scroll_If_Partially_Visible_Item_Is_Currently_Shown()
-////            {
-////                var target = CreateTarget(orientation: Orientation.Horizontal);
-////                var scroller = (TestScroller)target.Parent;
-
-////                scroller.Width = 95;
-////                scroller.Height = 100;
-////                scroller.LayoutManager.ExecuteInitialLayoutPass();
-////                ((ILogicalScrollable)target).Offset = new Vector(11, 0);
-
-////                var from = target.Panel.Children[1];
-////                var result = ((ILogicalScrollable)target).GetControlInDirection(
-////                    NavigationDirection.Left,
-////                    from);
-
-////                Assert.Equal(new Vector(10, 0), ((ILogicalScrollable)target).Offset);
-////                Assert.Same(target.Panel.Children[0], result);
-////            }
-////        }
-
-////        private static ItemsPresenter CreateTarget(
-////            Orientation orientation = Orientation.Vertical,
-////            int itemCount = 20,
-////            bool useAvaloniaList = false)
-////        {
-////            ItemsPresenter result;
-////            var itemsSource = Enumerable.Range(0, itemCount).Select(x => $"Item {x}");
-////            var items = useAvaloniaList ?
-////                (IEnumerable)new AvaloniaList<string>(itemsSource) :
-////                (IEnumerable)new ObservableCollection<string>(itemsSource);
-
-////            var scroller = new TestScroller
-////            {
-////                CanHorizontallyScroll = true,
-////                CanVerticallyScroll = true,
-////                Content = result = new TestItemsPresenter
-////                {
-////                    Items = items,
-////                    ItemsPanel = VirtualizingPanelTemplate(orientation),
-////                    DataTemplates = { StringDataTemplate() },
-////                    VirtualizationMode = ItemVirtualizationMode.Simple,
-////                }
-////            };
-
-////            scroller.UpdateChild();
-////            return result;
-////        }
-
-////        private static IDataTemplate StringDataTemplate()
-////        {
-////            return new FuncDataTemplate<string>((x, _) => new Canvas
-////            {
-////                Width = 10,
-////                Height = 10,
-////            });
-////        }
-
-////        private static ITemplate<Panel> VirtualizingPanelTemplate(
-////            Orientation orientation = Orientation.Vertical)
-////        {
-////            return new FuncTemplate<Panel>(() => new VirtualizingStackPanel
-////            {
-////                Orientation = orientation,
-////            });
-////        }
-
-////        private class TestScroller : ScrollContentPresenter, IRenderRoot, ILayoutRoot, ILogicalRoot
-////        {
-////            public TestScroller()
-////            {
-////                LayoutManager = new LayoutManager(this);
-////            }
-
-////            public IRenderer Renderer { get; }
-////            public Size ClientSize { get; }
-////            public double RenderScaling => 1;
-
-////            public Size MaxClientSize => Size.Infinity;
-
-////            public double LayoutScaling => 1;
-
-////            public ILayoutManager LayoutManager { get; }
-
-////            public IRenderTarget CreateRenderTarget() => throw new NotImplementedException();
-////            public void Invalidate(Rect rect) => throw new NotImplementedException();
-////            public Point PointToClient(PixelPoint p) => throw new NotImplementedException();
-////            public PixelPoint PointToScreen(Point p) => throw new NotImplementedException();
-////        }
-
-////        private class TestItemsPresenter : ItemsPresenter
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return new ItemContainerGenerator<TestContainer>(
-////                    this,
-////                    TestContainer.ContentProperty,
-////                    null);
-////            }
-////        }
-
-////        private class TestContainer : ContentControl
-////        {
-////            public TestContainer()
-////            {
-////                Template = new FuncControlTemplate<TestContainer>((parent, scope) => new ContentPresenter
-////                {
-////                    Name = "PART_ContentPresenter",
-////                    [~ContentPresenter.ContentProperty] = parent[~ContentControl.ContentProperty],
-////                    [~ContentPresenter.ContentTemplateProperty] = parent[~ContentControl.ContentTemplateProperty],
-////                }.RegisterInNameScope(scope));
-////            }
-////        }
-////    }
-////}

From 6f04196b84ca58f5dfa09676dc2c371c1a5dadb9 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 2 Dec 2022 23:26:36 +0100
Subject: [PATCH 030/157] Made TreeView work again and tests pass.

---
 .../Generators/TreeItemContainerGenerator.cs  |   32 +
 src/Avalonia.Controls/ItemsControl.cs         |   66 +-
 .../Presenters/ItemsPresenter.cs              |    8 +
 .../Primitives/HeaderedItemsControl.cs        |   16 +
 src/Avalonia.Controls/TreeView.cs             |  438 +--
 src/Avalonia.Controls/TreeViewItem.cs         |    5 +
 .../Controls/TreeViewItem.xaml                |    1 +
 .../Controls/TreeViewItem.xaml                |    1 +
 .../TreeViewTests.cs                          | 2866 ++++++++---------
 9 files changed, 1793 insertions(+), 1640 deletions(-)
 create mode 100644 src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs

diff --git a/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
new file mode 100644
index 0000000000..c1cae862a9
--- /dev/null
+++ b/src/Avalonia.Controls/Generators/TreeItemContainerGenerator.cs
@@ -0,0 +1,32 @@
+using System;
+using System.Collections.Generic;
+
+namespace Avalonia.Controls.Generators
+{
+    public class TreeItemContainerGenerator : ItemContainerGenerator
+    {
+        internal TreeItemContainerGenerator(TreeView owner)
+            : base(owner)
+        {
+            Index = new TreeContainerIndex(owner);
+        }
+
+        public TreeContainerIndex Index { get; }
+    }
+
+    public class TreeContainerIndex
+    {
+        private readonly TreeView _owner;
+
+        internal TreeContainerIndex(TreeView owner) => _owner = owner;
+
+        [Obsolete("Use TreeView.GetRealizedTreeContainers")]
+        public IEnumerable<Control> Containers => _owner.GetRealizedTreeContainers();
+
+        [Obsolete("Use TreeView.TreeContainerFromItem")]
+        public Control? ContainerFromItem(object item) => _owner.TreeContainerFromItem(item);
+
+        [Obsolete("Use TreeView.TreeItemFromContainer")]
+        public object? ItemFromContainer(Control container) => _owner.TreeItemFromContainer(container);
+    }
+}
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index e07eea57ef..645abf50b3 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -107,7 +107,12 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets the <see cref="ItemContainerGenerator"/> for the control.
         /// </summary>
-        public ItemContainerGenerator ItemContainerGenerator => _itemContainerGenerator ??= new(this);
+        public ItemContainerGenerator ItemContainerGenerator
+        {
+#pragma warning disable CS0612 // Type or member is obsolete
+            get => _itemContainerGenerator ??= CreateItemContainerGenerator();
+#pragma warning restore CS0612 // Type or member is obsolete
+        }
 
         /// <summary>
         /// Gets or sets the items to display.
@@ -188,7 +193,8 @@ namespace Avalonia.Controls
         /// </returns>
         public Control? ContainerFromItem(object item)
         {
-            throw new NotImplementedException();
+            var index = Items?.IndexOf(item) ?? -1;
+            return index >= 0 ? ContainerFromIndex(index) : null;
         }
 
         /// <summary>
@@ -210,8 +216,8 @@ namespace Avalonia.Controls
         /// </returns>
         public object? ItemFromContainer(Control container)
         {
-            // TODO: Should this throw or return null of container isn't a container?
-            throw new NotImplementedException();
+            var index = IndexFromContainer(container);
+            return index >= 0 && index < ItemCount ? Items!.ElementAt(index) : null;
         }
 
         /// <summary>
@@ -273,6 +279,8 @@ namespace Avalonia.Controls
             if (container == item)
                 return;
 
+            var itemTemplate = GetEffectiveItemTemplate();
+
             if (container is HeaderedContentControl hcc)
             {
                 hcc.Content = item;
@@ -282,20 +290,43 @@ namespace Avalonia.Controls
                 else if (item is not Visual)
                     hcc.Header = item;
 
-                if (GetEffectiveItemTemplate() is { } it)
-                    hcc.HeaderTemplate = it;
+                if (itemTemplate is not null)
+                    hcc.HeaderTemplate = itemTemplate;
             }
             else if (container is ContentControl cc)
             {
                 cc.Content = item;
-                if (GetEffectiveItemTemplate() is { } it)
-                    cc.ContentTemplate = it;
+                if (itemTemplate is not null)
+                    cc.ContentTemplate = itemTemplate;
             }
             else if (container is ContentPresenter p)
             {
                 p.Content = item;
-                if (GetEffectiveItemTemplate() is { } it)
-                    p.ContentTemplate = it;
+                if (itemTemplate is not null)
+                    p.ContentTemplate = itemTemplate;
+            }
+            else if (container is ItemsControl ic)
+            {
+                if (itemTemplate is not null)
+                    ic.ItemTemplate = itemTemplate;
+                if (ItemContainerTheme is { } ict)
+                    ic.ItemContainerTheme = ict;
+            }
+
+            // This condition is separate because HeaderedItemsControl needs to also run the
+            // ItemsControl preparation.
+            if (container is HeaderedItemsControl hic)
+            {
+                hic.Header = item;
+                hic.HeaderTemplate = itemTemplate;
+
+                var treeTemplate = (itemTemplate ?? hic.FindDataTemplate(item)) as ITreeDataTemplate;
+
+                if (treeTemplate is not null)
+                {
+                    if (item is not null && treeTemplate.ItemsSelector(item) is { } itemsBinding)
+                        BindingOperations.Apply(hic, ItemsProperty, itemsBinding, null);
+                }
             }
         }
 
@@ -316,6 +347,7 @@ namespace Avalonia.Controls
         /// <param name="container">The container element.</param>
         protected internal virtual void ClearContainerForItemOverride(Control container)
         {
+            // TODO: Remove HeaderedItemsControl.Items binding.
         }
 
         /// <summary>
@@ -486,6 +518,20 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Creates the <see cref="ItemContainerGenerator"/>
+        /// </summary>
+        /// <remarks>
+        /// This method is only present for backwards compatibility with 0.10.x in order for
+        /// TreeView to be able to create a <see cref="TreeItemContainerGenerator"/>. Can be
+        /// removed in 12.0.
+        /// </remarks>
+        [Obsolete]
+        private protected virtual ItemContainerGenerator CreateItemContainerGenerator()
+        {
+            return new ItemContainerGenerator(this);
+        }
+
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
 
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index f11d803fc5..0091bbd48d 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -3,6 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Reflection;
+using Avalonia.Input;
 
 namespace Avalonia.Controls.Presenters
 {
@@ -19,6 +20,13 @@ namespace Avalonia.Controls.Presenters
 
         private PanelContainerGenerator? _generator;
 
+        static ItemsPresenter()
+        {
+            KeyboardNavigation.TabNavigationProperty.OverrideDefaultValue(
+                typeof(ItemsPresenter),
+                KeyboardNavigationMode.Once);
+        }
+
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
diff --git a/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs b/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
index 2f051c4fda..71ae7a5bf6 100644
--- a/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/HeaderedItemsControl.cs
@@ -1,5 +1,6 @@
 using Avalonia.Collections;
 using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
 using Avalonia.LogicalTree;
 
 namespace Avalonia.Controls.Primitives
@@ -15,6 +16,12 @@ namespace Avalonia.Controls.Primitives
         public static readonly StyledProperty<object?> HeaderProperty =
             HeaderedContentControl.HeaderProperty.AddOwner<HeaderedItemsControl>();
 
+        /// <summary>
+        /// Defines the <see cref="HeaderTemplate"/> property.
+        /// </summary>
+        public static readonly StyledProperty<IDataTemplate?> HeaderTemplateProperty =
+            AvaloniaProperty.Register<HeaderedItemsControl, IDataTemplate?>(nameof(HeaderTemplate));
+
         /// <summary>
         /// Initializes static members of the <see cref="ContentControl"/> class.
         /// </summary>
@@ -32,6 +39,15 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(HeaderProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets the data template used to display the header content of the control.
+        /// </summary>
+        public IDataTemplate? HeaderTemplate
+        {
+            get => GetValue(HeaderTemplateProperty);
+            set => SetValue(HeaderTemplateProperty, value);
+        }
+
         /// <summary>
         /// Gets the header presenter from the control's template.
         /// </summary>
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 6336219fb6..c3e891149a 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -75,6 +75,12 @@ namespace Avalonia.Controls
             remove => RemoveHandler(SelectingItemsControl.SelectionChangedEvent, value);
         }
 
+        /// <summary>
+        /// Gets the <see cref="TreeItemContainerGenerator"/> for the tree view.
+        /// </summary>
+        public new TreeItemContainerGenerator ItemContainerGenerator =>
+            (TreeItemContainerGenerator)base.ItemContainerGenerator;
+
         /// <summary>
         /// Gets or sets a value indicating whether to automatically scroll to newly selected items.
         /// </summary>
@@ -182,8 +188,25 @@ namespace Avalonia.Controls
         /// </remarks>
         public void SelectAll()
         {
-            throw new NotImplementedException();
-            ////SynchronizeItems(SelectedItems, ItemContainerGenerator.Index!.Items);
+            var allItems = new List<object>();
+
+            void AddItems(ItemsControl itemsControl)
+            {
+                if (itemsControl.Items is { } items)
+                {
+                    foreach (var item in items)
+                        allItems.Add(item);
+                }
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl)
+                        AddItems(childItemsControl);
+                }
+            }
+
+            AddItems(this);
+            SynchronizeItems(SelectedItems, allItems);
         }
 
         /// <summary>
@@ -194,6 +217,62 @@ namespace Avalonia.Controls
             SelectedItems.Clear();
         }
 
+        public IEnumerable<Control> GetRealizedTreeContainers()
+        {
+            static IEnumerable<Control> GetRealizedContainers(ItemsControl itemsControl)
+            {
+                foreach (var container in itemsControl.GetRealizedContainers())
+                {
+                    yield return container;
+                    if (container is ItemsControl itemsControlContainer)
+                        foreach (var child in GetRealizedContainers(itemsControlContainer))
+                            yield return child;
+                }
+            }
+
+            return GetRealizedContainers(this);
+        }
+
+        public Control? TreeContainerFromItem(object item)
+        {
+            static Control? TreeContainerFromItem(ItemsControl itemsControl, object item)
+            {
+                if (itemsControl.ContainerFromItem(item) is { } container)
+                    return container;
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl &&
+                        TreeContainerFromItem(childItemsControl, item) is { } childContainer)
+                        return childContainer;
+                }
+
+                return null;
+            }
+
+            return TreeContainerFromItem(this, item);
+        }
+
+        public object? TreeItemFromContainer(Control container)
+        {
+            static object? TreeItemFromContainer(ItemsControl itemsControl, Control container)
+            {
+                if (itemsControl.ItemFromContainer(container) is { } item)
+                    return item;
+
+                foreach (var child in itemsControl.GetRealizedContainers())
+                {
+                    if (child is ItemsControl childItemsControl &&
+                        TreeItemFromContainer(childItemsControl, container) is { } childContainer)
+                        return childContainer;
+                }
+
+                return null;
+            }
+
+            return TreeItemFromContainer(this, container);
+        }
+
         /// <summary>
         /// Subscribes to the <see cref="SelectedItems"/> CollectionChanged event, if any.
         /// </summary>
@@ -277,10 +356,9 @@ namespace Avalonia.Controls
                     break;
                 case NotifyCollectionChangedAction.Reset:
 
-                    foreach (var child in LogicalChildren)
+                    foreach (var container in GetRealizedTreeContainers())
                     {
-                        if (child is Control container && IndexFromContainer(container) != -1)
-                            MarkContainerSelected(container, false);
+                        MarkContainerSelected(container, false);
                     }
 
                     if (SelectedItems.Count > 0)
@@ -333,7 +411,7 @@ namespace Avalonia.Controls
 
         private void MarkItemSelected(object item, bool selected)
         {
-            var container = ContainerFromItem(item)!;
+            var container = TreeContainerFromItem(item)!;
 
             MarkContainerSelected(container, selected);
         }
@@ -366,6 +444,7 @@ namespace Avalonia.Controls
                 incc.CollectionChanged -= SelectedItemsCollectionChanged;
             }
         }
+        
         (bool handled, IInputElement? next) ICustomKeyboardNavigation.GetNext(IInputElement element,
             NavigationDirection direction)
         {
@@ -374,7 +453,7 @@ namespace Avalonia.Controls
                 if (!this.IsVisualAncestorOf((Visual)element))
                 {
                     var result = _selectedItem != null ?
-                        ContainerFromItem(_selectedItem) :
+                        TreeContainerFromItem(_selectedItem) :
                         ContainerFromIndex(0);
                     
                     return (result != null, result); // SelectedItem may not be in the treeview.
@@ -386,6 +465,9 @@ namespace Avalonia.Controls
             return (false, null);
         }
 
+        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -441,54 +523,58 @@ namespace Avalonia.Controls
             NavigationDirection direction,
             bool intoChildren)
         {
-            throw new NotImplementedException();
-            ////IItemContainerGenerator? parentGenerator = GetParentContainerGenerator(from);
-
-            ////if (parentGenerator == null)
-            ////{
-            ////    return null;
-            ////}
-
-            ////var index = from is not null ? parentGenerator.IndexFromContainer(from) : -1;
-            ////var parent = from?.Parent as ItemsControl;
-            ////TreeViewItem? result = null;
-
-            ////switch (direction)
-            ////{
-            ////    case NavigationDirection.Up:
-            ////        if (index > 0)
-            ////        {
-            ////            var previous = (TreeViewItem)parentGenerator.ContainerFromIndex(index - 1)!;
-            ////            result = previous.IsExpanded && previous.ItemCount > 0 ?
-            ////                (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
-            ////                previous;
-            ////        }
-            ////        else
-            ////        {
-            ////            result = from?.Parent as TreeViewItem;
-            ////        }
-
-            ////        break;
-
-            ////    case NavigationDirection.Down:
-            ////    case NavigationDirection.Right:
-            ////        if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
-            ////        {
-            ////            result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
-            ////        }
-            ////        else if (index < parent?.ItemCount - 1)
-            ////        {
-            ////            result = (TreeViewItem)parentGenerator.ContainerFromIndex(index + 1)!;
-            ////        }
-            ////        else if (parent is TreeViewItem parentItem)
-            ////        {
-            ////            return GetContainerInDirection(parentItem, direction, false);
-            ////        }
-
-            ////        break;
-            ////}
-
-            ////return result;
+            var parentItemsControl = from?.Parent switch
+            {
+                TreeView tv => (ItemsControl)tv,
+                TreeViewItem i => i,
+                _ => null
+            };
+
+            if (parentItemsControl == null)
+            {
+                return null;
+            }
+
+            var index = from is not null ? parentItemsControl.IndexFromContainer(from) : -1;
+            var parent = from?.Parent as ItemsControl;
+            TreeViewItem? result = null;
+
+            switch (direction)
+            {
+                case NavigationDirection.Up:
+                    if (index > 0)
+                    {
+                        var previous = (TreeViewItem)parentItemsControl.ContainerFromIndex(index - 1)!;
+                        result = previous.IsExpanded && previous.ItemCount > 0 ?
+                            (TreeViewItem)previous.ItemContainerGenerator.ContainerFromIndex(previous.ItemCount - 1)! :
+                            previous;
+                    }
+                    else
+                    {
+                        result = from?.Parent as TreeViewItem;
+                    }
+
+                    break;
+
+                case NavigationDirection.Down:
+                case NavigationDirection.Right:
+                    if (from?.IsExpanded == true && intoChildren && from.ItemCount > 0)
+                    {
+                        result = (TreeViewItem)from.ItemContainerGenerator.ContainerFromIndex(0)!;
+                    }
+                    else if (index < parent?.ItemCount - 1)
+                    {
+                        result = (TreeViewItem)parentItemsControl.ContainerFromIndex(index + 1)!;
+                    }
+                    else if (parent is TreeViewItem parentItem)
+                    {
+                        return GetContainerInDirection(parentItem, direction, false);
+                    }
+
+                    break;
+            }
+
+            return result;
         }
 
         /// <inheritdoc/>
@@ -527,63 +613,68 @@ namespace Avalonia.Controls
             bool toggleModifier = false,
             bool rightButton = false)
         {
-            throw new NotImplementedException();
-            ////var item = ItemContainerGenerator.Index!.ItemFromContainer(container);
-
-            ////if (item == null)
-            ////{
-            ////    return;
-            ////}
-
-            ////Control? selectedContainer = null;
-
-            ////if (SelectedItem != null)
-            ////{
-            ////    selectedContainer = ItemContainerGenerator.Index!.ContainerFromItem(SelectedItem);
-            ////}
-
-            ////var mode = SelectionMode;
-            ////var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
-            ////var multi = mode.HasAllFlags(SelectionMode.Multiple);
-            ////var range = multi && rangeModifier && selectedContainer != null;
-
-            ////if (rightButton)
-            ////{
-            ////    if (!SelectedItems.Contains(item))
-            ////    {
-            ////        SelectSingleItem(item);
-            ////    }
-            ////}
-            ////else if (!toggle && !range)
-            ////{
-            ////    SelectSingleItem(item);
-            ////}
-            ////else if (multi && range)
-            ////{
-            ////    SynchronizeItems(
-            ////        SelectedItems,
-            ////        GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
-            ////}
-            ////else
-            ////{
-            ////    var i = SelectedItems.IndexOf(item);
-
-            ////    if (i != -1)
-            ////    {
-            ////        SelectedItems.Remove(item);
-            ////    }
-            ////    else
-            ////    {
-            ////        if (multi)
-            ////        {
-            ////            SelectedItems.Add(item);
-            ////        }
-            ////        else
-            ////        {
-            ////            SelectedItem = item;
-            ////        }
-            ////    }
-            ////}
+            var item = TreeItemFromContainer(container);
+
+            if (item == null)
+            {
+                return;
+            }
+
+            Control? selectedContainer = null;
+
+            if (SelectedItem != null)
+            {
+                selectedContainer = TreeContainerFromItem(SelectedItem);
+            }
+
+            var mode = SelectionMode;
+            var toggle = toggleModifier || mode.HasAllFlags(SelectionMode.Toggle);
+            var multi = mode.HasAllFlags(SelectionMode.Multiple);
+            var range = multi && rangeModifier && selectedContainer != null;
+
+            if (rightButton)
+            {
+                if (!SelectedItems.Contains(item))
+                {
+                    SelectSingleItem(item);
+                }
+            }
+            else if (!toggle && !range)
+            {
+                SelectSingleItem(item);
+            }
+            else if (multi && range)
+            {
+                SynchronizeItems(
+                    SelectedItems,
+                    GetItemsInRange(selectedContainer as TreeViewItem, container as TreeViewItem));
+            }
+            else
+            {
+                var i = SelectedItems.IndexOf(item);
+
+                if (i != -1)
+                {
+                    SelectedItems.Remove(item);
+                }
+                else
+                {
+                    if (multi)
+                    {
+                        SelectedItems.Add(item);
+                    }
+                    else
+                    {
+                        SelectedItem = item;
+                    }
+                }
+            }
+        }
+
+        [Obsolete]
+        private protected override ItemContainerGenerator CreateItemContainerGenerator()
+        {
+            return new TreeItemContainerGenerator(this);
         }
 
         /// <summary>
@@ -595,27 +686,24 @@ namespace Avalonia.Controls
         /// <returns>Found first node.</returns>
         private static TreeViewItem? FindFirstNode(TreeView treeView, TreeViewItem nodeA, TreeViewItem nodeB)
         {
-            return FindInContainers(treeView.ItemContainerGenerator, nodeA, nodeB);
+            return FindInContainers(treeView, nodeA, nodeB);
         }
 
-        private static TreeViewItem? FindInContainers(ItemContainerGenerator containerGenerator,
+        private static TreeViewItem? FindInContainers(ItemsControl itemsControl,
             TreeViewItem nodeA,
             TreeViewItem nodeB)
         {
-            throw new NotImplementedException();
-            ////IEnumerable<ItemContainerInfo> containers = containerGenerator.Containers;
-
-            ////foreach (ItemContainerInfo container in containers)
-            ////{
-            ////    TreeViewItem? node = FindFirstNode(container.ContainerControl as TreeViewItem, nodeA, nodeB);
+            foreach (var container in itemsControl.GetRealizedContainers())
+            {
+                TreeViewItem? node = FindFirstNode(container as TreeViewItem, nodeA, nodeB);
 
-            ////    if (node != null)
-            ////    {
-            ////        return node;
-            ////    }
-            ////}
+                if (node != null)
+                {
+                    return node;
+                }
+            }
 
-            ////return null;
+            return null;
         }
 
         private static TreeViewItem? FindFirstNode(TreeViewItem? node, TreeViewItem nodeA, TreeViewItem nodeB)
@@ -632,7 +720,7 @@ namespace Avalonia.Controls
                 return match;
             }
 
-            return FindInContainers(node.ItemContainerGenerator, nodeA, nodeB);
+            return FindInContainers(node, nodeA, nodeB);
         }
 
         /// <summary>
@@ -643,60 +731,59 @@ namespace Avalonia.Controls
         /// <param name="to">To container.</param>
         private List<object> GetItemsInRange(TreeViewItem? from, TreeViewItem? to)
         {
-            throw new NotImplementedException();
-            ////var items = new List<object>();
+            var items = new List<object>();
 
-            ////if (from == null || to == null)
-            ////{
-            ////    return items;
-            ////}
+            if (from == null || to == null)
+            {
+                return items;
+            }
 
-            ////TreeViewItem? firstItem = FindFirstNode(this, from, to);
+            TreeViewItem? firstItem = FindFirstNode(this, from, to);
 
-            ////if (firstItem == null)
-            ////{
-            ////    return items;
-            ////}
+            if (firstItem == null)
+            {
+                return items;
+            }
 
-            ////bool wasReversed = false;
+            bool wasReversed = false;
 
-            ////if (firstItem == to)
-            ////{
-            ////    var temp = from;
+            if (firstItem == to)
+            {
+                var temp = from;
 
-            ////    from = to;
-            ////    to = temp;
+                from = to;
+                to = temp;
 
-            ////    wasReversed = true;
-            ////}
+                wasReversed = true;
+            }
 
-            ////TreeViewItem? node = from;
+            TreeViewItem? node = from;
 
-            ////while (node != to)
-            ////{
-            ////    var item = ItemContainerGenerator.Index!.ItemFromContainer(node);
+            while (node is not null && node != to)
+            {
+                var item = TreeItemFromContainer(node);
 
-            ////    if (item != null)
-            ////    {
-            ////        items.Add(item);
-            ////    }
+                if (item != null)
+                {
+                    items.Add(item);
+                }
 
-            ////    node = GetContainerInDirection(node, NavigationDirection.Down, true);
-            ////}
+                node = GetContainerInDirection(node, NavigationDirection.Down, true);
+            }
 
-            ////var toItem = ItemContainerGenerator.Index!.ItemFromContainer(to);
+            var toItem = TreeItemFromContainer(to);
 
-            ////if (toItem != null)
-            ////{
-            ////    items.Add(toItem);
-            ////}
+            if (toItem != null)
+            {
+                items.Add(toItem);
+            }
 
-            ////if (wasReversed)
-            ////{
-            ////    items.Reverse();
-            ////}
+            if (wasReversed)
+            {
+                items.Reverse();
+            }
 
-            ////return items;
+            return items;
         }
 
         /// <summary>
@@ -737,20 +824,11 @@ namespace Avalonia.Controls
         /// <returns>The container or null if the event did not originate in a container.</returns>
         protected TreeViewItem? GetContainerFromEventSource(object eventSource)
         {
-            throw new NotImplementedException();
-            ////var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
-            ////    .OfType<TreeViewItem>()
-            ////    .FirstOrDefault();
-
-            ////if (item != null)
-            ////{
-            ////    if (item.ItemContainerGenerator.Index == ItemContainerGenerator.Index)
-            ////    {
-            ////        return item;
-            ////    }
-            ////}
+            var item = ((Visual)eventSource).GetSelfAndVisualAncestors()
+                .OfType<TreeViewItem>()
+                .FirstOrDefault();
 
-            ////return null;
+            return item?.TreeViewOwner == this ? item : null;
         }
 
         /// <summary>
@@ -801,7 +879,7 @@ namespace Avalonia.Controls
             }
             else
             {
-                container.Classes.Set(":selected", selected);
+                ((IPseudoClasses)container.Classes).Set(":selected", selected);
             }
         }
 
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 097fe54f42..3ff34a14b1 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -88,6 +88,11 @@ namespace Avalonia.Controls
             private set { SetAndRaise(LevelProperty, ref _level, value); }
         }
 
+        internal TreeView? TreeViewOwner => _treeView;
+
+        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
+
         /// <inheritdoc/>
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
diff --git a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
index 834c2245a8..b2dc8615a9 100644
--- a/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/TreeViewItem.xaml
@@ -88,6 +88,7 @@
                                 Grid.Column="1"
                                 Focusable="False"
                                 Content="{TemplateBinding Header}"
+                                ContentTemplate="{TemplateBinding HeaderTemplate}"
                                 HorizontalAlignment="{TemplateBinding HorizontalAlignment}"
                                 VerticalAlignment="{TemplateBinding VerticalAlignment}"
                                 Margin="{TemplateBinding Padding}" />
diff --git a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
index c36bf4c673..b75da2dd7b 100644
--- a/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/TreeViewItem.xaml
@@ -58,6 +58,7 @@
                                 Padding="{TemplateBinding Padding}"
                                 HorizontalContentAlignment="{TemplateBinding HorizontalAlignment}"
                                 Content="{TemplateBinding Header}"
+                                ContentTemplate="{TemplateBinding HeaderTemplate}"
                                 Focusable="False" />
             </Grid>
           </Border>
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 8ded57956b..b9a6566116 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1,1475 +1,1441 @@
-////using System;
-////using System.Collections;
-////using System.Collections.Generic;
-////using System.Collections.ObjectModel;
-////using System.ComponentModel;
-////using System.Linq;
-////using System.Runtime.CompilerServices;
-////using Avalonia.Collections;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Data;
-////using Avalonia.Data.Core;
-////using Avalonia.Input;
-////using Avalonia.Input.Platform;
-////using Avalonia.Interactivity;
-////using Avalonia.LogicalTree;
-////using Avalonia.Styling;
-////using Avalonia.UnitTests;
-////using JetBrains.Annotations;
-////using Moq;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class TreeViewTests
-////    {
-////        MouseTestHelper _mouse = new MouseTestHelper();
-
-////        [Fact]
-////        public void Items_Should_Be_Created()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = CreateTestTreeData(),
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-////        }
-
-////        [Fact]
-////        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
-////        {
-////            TreeView target;
-
-////            var root = new TestRoot
-////            {
-////                Child = target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = CreateTestTreeData(),
-////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-////                        (_, __) => new Canvas(),
-////                        x => x.Children),
-////                }
-////            };
-
-////            ApplyTemplates(target);
-
-////            var items = target.ItemContainerGenerator.Index.Containers
-////                .OfType<TreeViewItem>()
-////                .ToList();
-
-////            Assert.Equal(5, items.Count);
-////            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
-////        }
-
-////        [Fact]
-////        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
-////        {
-////            TreeView target;
-////            var theme = new ControlTheme(typeof(TreeViewItem));
-
-////            var root = new TestRoot
-////            {
-////                Child = target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = CreateTestTreeData(),
-////                    ItemContainerTheme = theme,
-////                    ItemTemplate = new FuncTreeDataTemplate<Node>(
-////                        (_, __) => new Canvas(),
-////                        x => x.Children),
-////                }
-////            };
-
-////            ApplyTemplates(target);
-
-////            var items = target.ItemContainerGenerator.Index.Containers
-////                .OfType<TreeViewItem>()
-////                .ToList();
-
-////            Assert.Equal(5, items.Count);
-////            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
-////        }
-
-////        [Fact]
-////        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = CreateTestTreeData(),
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var container = (TreeViewItem)target.ItemContainerGenerator.Containers.Single().ContainerControl;
-////            var header = (TextBlock)container.Header;
-////            Assert.Equal("Root", header.Text);
-////        }
-
-////        [Fact]
-////        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
-////            // to be called, which requires an IStyleRoot.
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var container = target.ItemContainerGenerator.Index.ContainerFromItem(
-////                tree[0].Children[1].Children[0]);
-
-////            Assert.NotNull(container);
-
-////            var header = ((TreeViewItem)container).Header;
-////            var headerContent = ((TextBlock)header).Text;
-
-////            Assert.Equal("Grandchild2a", headerContent);
-////        }
-
-////        [Fact]
-////        public void Clicking_Item_Should_Select_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                _mouse.Click(container);
-
-////                Assert.Equal(item, target.SelectedItem);
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                target.SelectedItem = item;
-
-////                Assert.True(container.IsSelected);
-
-////                _mouse.Click(container, modifiers: KeyModifiers.Control);
-
-////                Assert.Null(target.SelectedItem);
-////                Assert.False(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree
-////                };
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.ComponentModel;
+using System.Linq;
+using Avalonia.Collections;
+using Avalonia.Controls.Generators;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Data.Core;
+using Avalonia.Input;
+using Avalonia.Input.Platform;
+using Avalonia.Interactivity;
+using Avalonia.LogicalTree;
+using Avalonia.Styling;
+using Avalonia.UnitTests;
+using Moq;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class TreeViewTests
+    {
+        MouseTestHelper _mouse = new MouseTestHelper();
+
+        [Fact]
+        public void Items_Should_Be_Created()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = CreateTestTreeData(),
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+        }
+
+        [Fact]
+        public void Items_Should_Be_Created_Using_ItemTemplate_If_Present()
+        {
+            TreeView target;
+
+            var root = new TestRoot
+            {
+                Child = target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = CreateTestTreeData(),
+                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+                        (_, __) => new Canvas(),
+                        x => x.Children),
+                }
+            };
+
+            ApplyTemplates(target);
+
+            var items = target.GetRealizedTreeContainers()
+                .OfType<TreeViewItem>()
+                .ToList();
+
+            Assert.Equal(5, items.Count);
+            Assert.All(items, x => Assert.IsType<Canvas>(x.HeaderPresenter.Child));
+        }
+
+        [Fact]
+        public void Items_Should_Be_Created_Using_ItemConatinerTheme_If_Present()
+        {
+            TreeView target;
+            var theme = new ControlTheme(typeof(TreeViewItem));
+
+            var root = new TestRoot
+            {
+                Child = target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = CreateTestTreeData(),
+                    ItemContainerTheme = theme,
+                    ItemTemplate = new FuncTreeDataTemplate<Node>(
+                        (_, __) => new Canvas(),
+                        x => x.Children),
+                }
+            };
+
+            ApplyTemplates(target);
+
+            var items = target.GetRealizedTreeContainers()
+                .OfType<TreeViewItem>()
+                .ToList();
+
+            Assert.Equal(5, items.Count);
+            Assert.All(items, x => Assert.Same(theme, x.ItemContainerTheme));
+        }
+
+        [Fact]
+        public void Root_ItemContainerGenerator_Containers_Should_Be_Root_Containers()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = CreateTestTreeData(),
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var container = (TreeViewItem)target.GetRealizedContainers().Single();
+            var header = (TextBlock)container.HeaderPresenter.Child;
+            Assert.Equal("Root", header.Text);
+        }
+
+        [Fact]
+        public void Root_TreeContainerFromItem_Should_Return_Descendant_Item()
+        {
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            // For TreeViewItem to find its parent TreeView, OnAttachedToLogicalTree needs
+            // to be called, which requires an IStyleRoot.
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var container = target.TreeContainerFromItem(tree[0].Children[1].Children[0]);
+
+            Assert.NotNull(container);
+
+            var header = ((TreeViewItem)container).HeaderPresenter;
+            var headerContent = ((TextBlock)header.Child).Text;
+
+            Assert.Equal("Grandchild2a", headerContent);
+        }
+
+        [Fact]
+        public void Clicking_Item_Should_Select_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                _mouse.Click(container);
+
+                Assert.Equal(item, target.SelectedItem);
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree
+                };
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                target.SelectedItem = item;
+
+                Assert.True(container.IsSelected);
+
+                _mouse.Click(container, modifiers: KeyModifiers.Control);
+
+                Assert.Null(target.SelectedItem);
+                Assert.False(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Not_Selected_Item_Should_Select_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var item1 = tree[0].Children[1].Children[0];
-////                var container1 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                var item2 = tree[0].Children[1];
-////                var container2 = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
+                var item1 = tree[0].Children[1].Children[0];
+                var container1 = (TreeViewItem)target.TreeContainerFromItem(item1);
 
-////                Assert.NotNull(container1);
-////                Assert.NotNull(container2);
-
-////                target.SelectedItem = item1;
-
-////                Assert.True(container1.IsSelected);
-
-////                _mouse.Click(container2, modifiers: KeyModifiers.Control);
-
-////                Assert.Equal(item2, target.SelectedItem);
-////                Assert.False(container1.IsSelected);
-////                Assert.True(container2.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
+                var item2 = tree[0].Children[1];
+                var container2 = (TreeViewItem)target.TreeContainerFromItem(item2);
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+                Assert.NotNull(container1);
+                Assert.NotNull(container2);
+
+                target.SelectedItem = item1;
+
+                Assert.True(container1.IsSelected);
+
+                _mouse.Click(container2, modifiers: KeyModifiers.Control);
+
+                Assert.Equal(item2, target.SelectedItem);
+                Assert.False(container1.IsSelected);
+                Assert.True(container2.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Clicking_WithControlModifier_Selected_Item_Should_Deselect_And_Remove_From_SelectedItems()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var rootNode = tree[0];
-
-////                var item1 = rootNode.Children[0];
-////                var item2 = rootNode.Children.Last();
-
-////                var item1Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item1);
-////                var item2Container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item2);
-
-////                ClickContainer(item1Container, KeyModifiers.Control);
-////                Assert.True(item1Container.IsSelected);
-
-////                ClickContainer(item2Container, KeyModifiers.Control);
-////                Assert.True(item2Container.IsSelected);
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
+                var rootNode = tree[0];
+
+                var item1 = rootNode.Children[0];
+                var item2 = rootNode.Children.Last();
+
+                var item1Container = (TreeViewItem)target.TreeContainerFromItem(item1);
+                var item2Container = (TreeViewItem)target.TreeContainerFromItem(item2);
+
+                ClickContainer(item1Container, KeyModifiers.Control);
+                Assert.True(item1Container.IsSelected);
+
+                ClickContainer(item2Container, KeyModifiers.Control);
+                Assert.True(item2Container.IsSelected);
 
-////                ClickContainer(item1Container, KeyModifiers.Control);
-////                Assert.False(item1Container.IsSelected);
+                Assert.Equal(new[] { item1, item2 }, target.SelectedItems.OfType<Node>());
 
-////                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
-////            }
-////        }
+                ClickContainer(item1Container, KeyModifiers.Control);
+                Assert.False(item1Container.IsSelected);
 
-////        [Fact]
-////        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
+                Assert.DoesNotContain(item1, target.SelectedItems.OfType<Node>());
+            }
+        }
 
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
+        [Fact]
+        public void Clicking_WithShiftModifier_DownDirection_Should_Select_Range_Of_Items()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
 
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
 
-////                var rootNode = tree[0];
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children.Last();
+                var rootNode = tree[0];
 
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
+                var from = rootNode.Children[0];
+                var to = rootNode.Children.Last();
 
-////                ClickContainer(fromContainer, KeyModifiers.None);
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
 
-////                Assert.True(fromContainer.IsSelected);
+                ClickContainer(fromContainer, KeyModifiers.None);
 
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
+                Assert.True(fromContainer.IsSelected);
 
-////        [Fact]
-////        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
 
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
+        [Fact]
+        public void Clicking_WithShiftModifier_UpDirection_Should_Select_Range_Of_Items()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
 
-////                Assert.True(fromContainer.IsSelected);
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
 
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
+                Assert.True(fromContainer.IsSelected);
 
-////        [Fact]
-////        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-////                AssertChildrenSelected(target, rootNode);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-
-////                Assert.True(fromContainer.IsSelected);
-
-////                foreach (var child in rootNode.Children)
-////                {
-////                    if (child == from)
-////                    {
-////                        continue;
-////                    }
-
-////                    var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-////                    Assert.False(container.IsSelected);
-////                }
-////            }
-////        }
-
-////        [Fact]
-////        public void Setting_SelectedItem_Should_Set_Container_Selected()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-////                var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-
-////                Assert.NotNull(container);
-
-////                target.SelectedItem = item;
-
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        [Fact]
-////        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = tree[0].Children[1].Children[0];
-
-////                var called = false;
-////                target.SelectionChanged += (s, e) =>
-////                {
-////                    Assert.Empty(e.RemovedItems);
-////                    Assert.Equal(1, e.AddedItems.Count);
-////                    Assert.Same(item, e.AddedItems[0]);
-////                    called = true;
-////                };
-
-////                target.SelectedItem = item;
-////                Assert.True(called);
-////            }
-////        }
-
-////        [Fact]
-////        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
-////        {
-////            using (Application())
-////            {
-////                var dataContext = new TestDataContext();
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    DataContext = dataContext
-////                };
-
-////                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
-////                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-
-////                var selectedValues = new List<object>();
-
-////                dataContext.PropertyChanged += (_, e) =>
-////                {
-////                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
-////                        selectedValues.Add(dataContext.SelectedItem);
-////                };
-////                selectedValues.Add(dataContext.SelectedItem);
-
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
-
-////                Assert.Equal(3, selectedValues.Count);
-////                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
-////            }
-////        }
-
-////        [Fact]
-////        public void LogicalChildren_Should_Be_Set()
-////        {
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = new[] { "Foo", "Bar", "Baz " },
-////            };
-
-////            ApplyTemplates(target);
-
-////            var result = target.GetLogicalChildren()
-////                .OfType<TreeViewItem>()
-////                .Select(x => x.Header)
-////                .OfType<TextBlock>()
-////                .Select(x => x.Text)
-////                .ToList();
-
-////            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
-////        }
-
-////        [Fact]
-////        public void Removing_Item_Should_Remove_Itself_And_Children_From_Index()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-////            tree[0].Children.RemoveAt(1);
-
-////            Assert.Equal(3, target.ItemContainerGenerator.Index.Containers.Count());
-////        }
-
-////        [Fact]
-////        public void DataContexts_Should_Be_Correctly_Set()
-////        {
-////            var items = new object[]
-////            {
-////                "Foo",
-////                new Node { Value = "Bar" },
-////                new TextBlock { Text = "Baz" },
-////                new TreeViewItem { Header = "Qux" },
-////            };
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                DataContext = "Base",
-////                DataTemplates =
-////                {
-////                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
-////                },
-////                Items = items,
-////            };
-
-////            ApplyTemplates(target);
-
-////            var dataContexts = target.Presenter.Panel.Children
-////                .Cast<Control>()
-////                .Select(x => x.DataContext)
-////                .ToList();
-
-////            Assert.Equal(
-////                new object[] { items[0], items[1], "Base", "Base" },
-////                dataContexts);
-////        }
-
-////        [Fact]
-////        public void Control_Item_Should_Not_Be_NameScope()
-////        {
-////            var items = new object[]
-////            {
-////                new TreeViewItem(),
-////            };
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = items,
-////            };
-
-////            target.ApplyTemplate();
-////            target.Presenter.ApplyTemplate();
-
-////            var item = target.Presenter.Panel.LogicalChildren[0];
-////            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
-////        }
-
-////        [Fact]
-////        public void Should_React_To_Children_Changing()
-////        {
-////            var data = CreateTestTreeData();
-
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = data,
-////            };
-
-////            var root = new TestRoot(target);
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
-////            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
-
-////            // Make sure that the binding to Node.Children does not get collected.
-////            GC.Collect();
-
-////            data[0].Children = new AvaloniaList<Node>
-////            {
-////                new Node
-////                {
-////                    Value = "NewChild1",
-////                }
-////            };
-
-////            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
-////            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
-////        }
-
-////        [Fact]
-////        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
-////        {
-////            using (Application())
-////            {
-////                var focus = FocusManager.Instance;
-////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-////                var data = CreateTestTreeData();
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = data,
-////                };
-
-////                var button = new Button();
-
-////                var root = new TestRoot
-////                {
-////                    Child = new StackPanel
-////                    {
-////                        Children = { target, button },
-////                    }
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = data[0].Children[0];
-////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////                Assert.NotNull(node);
-
-////                target.SelectedItem = item;
-////                node.Focus();
-////                Assert.Same(node, focus.Current);
-
-////                navigation.Move(focus.Current, NavigationDirection.Next);
-////                Assert.Same(button, focus.Current);
-
-////                navigation.Move(focus.Current, NavigationDirection.Next);
-////                Assert.Same(node, focus.Current);
-////            }
-////        }
-
-////        [Fact]
-////        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
-////        {
-////            using (Application())
-////            {
-////                var focus = FocusManager.Instance;
-////                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
-////                var data = CreateTestTreeData();
-
-////                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
-
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = data,
-////                    SelectedItem = selectedNode
-////                };
-
-////                var button = new Button();
-
-////                var root = new TestRoot
-////                {
-////                    Child = new StackPanel
-////                    {
-////                        Children = { target, button },
-////                    }
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var item = data[0].Children[0];
-////                var node = target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////                Assert.NotNull(node);
-
-////                target.SelectedItem = selectedNode;
-////                node.Focus();
-////                Assert.Same(node, focus.Current);
-
-////                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
-////        {
-////            using (UnitTestApplication.Start())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children.Last();
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                ExpandAll(target);
-
-////                var rootNode = tree[0];
-
-////                var from = rootNode.Children.Last();
-////                var to = rootNode.Children[0];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
-////                var selectAllGesture = keymap.SelectAll.First();
-
-////                var keyEvent = new KeyEventArgs
-////                {
-////                    RoutedEvent = InputElement.KeyDownEvent,
-////                    Key = selectAllGesture.Key,
-////                    KeyModifiers = selectAllGesture.KeyModifiers
-////                };
-
-////                target.RaiseEvent(keyEvent);
-
-////                AssertChildrenSelected(target, rootNode);
-////            }
-////        }
-
-////        [Fact]
-////        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
-////        {
-////            using (UnitTestApplication.Start())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-////                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-////                target.SelectAll();
-
-////                AssertChildrenSelected(target, tree[0]);
-////                Assert.Equal(5, target.SelectedItems.Count);
-
-////                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
-
-////                Assert.Equal(5, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var to = rootNode.Children[0];
-////                var then = rootNode.Children[1];
-
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-////                var thenContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(then);
-
-////                ClickContainer(fromContainer, KeyModifiers.None);
-////                ClickContainer(toContainer, KeyModifiers.Shift);
-
-////                Assert.Equal(2, target.SelectedItems.Count);
-
-////                _mouse.Click(thenContainer, MouseButton.Right);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Shift_Right_Click_Should_Not_Select_Multiple()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children[1];
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                _mouse.Click(fromContainer);
-////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
-////        {
-////            using (Application())
-////            {
-////                var tree = CreateTestTreeData();
-////                var target = new TreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    Items = tree,
-////                    SelectionMode = SelectionMode.Multiple,
-////                };
-
-////                var visualRoot = new TestRoot();
-////                visualRoot.Child = target;
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-////                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
-
-////                var rootNode = tree[0];
-////                var from = rootNode.Children[0];
-////                var to = rootNode.Children[1];
-////                var fromContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(from);
-////                var toContainer = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(to);
-
-////                _mouse.Click(fromContainer);
-////                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
-
-////                Assert.Equal(1, target.SelectedItems.Count);
-////            }
-////        }
-
-////        [Fact]
-////        public void TreeViewItems_Level_Should_Be_Set()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(0, GetItem(target, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 1).Level);
-////            Assert.Equal(1, GetItem(target, 0, 2).Level);
-////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-////        }
-
-////        [Fact]
-////        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new DerivedTreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(0, GetItem(target, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 0).Level);
-////            Assert.Equal(1, GetItem(target, 0, 1).Level);
-////            Assert.Equal(1, GetItem(target, 0, 2).Level);
-////            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
-////        }
-
-////        [Fact]
-////        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
-////        {
-////            // Issue #2985
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var visualRoot = new TestRoot();
-////            visualRoot.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            var parent = tree[0];
-////            var node = parent.Children[1];
-
-////            parent.Children.Remove(node);
-////            parent.Children.Add(node);
-
-////            var item = target.ItemContainerGenerator.Index.ContainerFromItem(node);
-////            ApplyTemplates(new[] { item });
-
-////            // #2985 causes ArgumentException here.
-////            node.Children.Add(new Node());
-////        }
-
-////        [Fact]
-////        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
-////        {
-////            // Issue #2980.
-////            using (Application())
-////            {
-////                var target = new DerivedTreeView
-////                {
-////                    Template = CreateTreeViewTemplate(),
-////                    SelectionMode = SelectionMode.Multiple,
-////                    Items = new List<Node>
-////                {
-////                    new Node { Value = "Root1", },
-////                    new Node { Value = "Root2", },
-////                },
-////                };
-
-////                var visualRoot = new TestRoot
-////                {
-////                    Styles =
-////                    {
-////                        new Style(x => x.OfType<TreeViewItem>())
-////                        {
-////                            Setters =
-////                            {
-////                                new Setter(TreeViewItem.IsExpandedProperty, true),
-////                            },
-////                        },
-////                    },
-////                    Child = target,
-////                };
-
-////                CreateNodeDataTemplate(target);
-////                ApplyTemplates(target);
-
-////                _mouse.Click(GetItem(target, 0));
-////                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
-////            }
-////        }
-
-////        [Fact]
-////        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
-////        {
-////            // Issue #3328
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-////            ExpandAll(target);
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-
-////            root.Child = null;
-
-////            Assert.Equal(5, target.ItemContainerGenerator.Index.Containers.Count());
-////            Assert.Equal(1, target.Presenter.Panel.Children.Count);
-
-////            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
-////            Assert.Equal(3, rootNode.ItemContainerGenerator.Containers.Count());
-////            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
-
-////            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
-////            Assert.Equal(1, child2Node.ItemContainerGenerator.Containers.Count());
-////            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
-////        }
-
-////        [Fact]
-////        public void Clearing_TreeView_Items_Clears_Index()
-////        {
-////            // Issue #3551
-////            var tree = CreateTestTreeData();
-////            var target = new TreeView
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            var root = new TestRoot();
-////            root.Child = target;
-
-////            CreateNodeDataTemplate(target);
-////            ApplyTemplates(target);
-
-////            var rootNode = tree[0];
-////            var container = (TreeViewItem)target.ItemContainerGenerator.Index.ContainerFromItem(rootNode);
-
-////            Assert.NotNull(container);
-
-////            root.Child = null;
-
-////            tree.Clear();
-
-////            Assert.Empty(target.ItemContainerGenerator.Index.Containers);
-////        }
-
-////        [Fact]
-////        public void Can_Use_Derived_TreeViewItem()
-////        {
-////            var tree = CreateTestTreeData();
-////            var target = new DerivedTreeViewWithDerivedTreeViewItems
-////            {
-////                Template = CreateTreeViewTemplate(),
-////                Items = tree,
-////            };
-
-////            ApplyTemplates(target);
-
-////            // Verify that all items are DerivedTreeViewItem
-////            VerifyItemType(target.ItemContainerGenerator);
-
-////            void VerifyItemType(ITreeItemContainerGenerator containerGenerator)
-////            {
-////                foreach (var container in containerGenerator.Index.Containers)
-////                {
-////                    var item = Assert.IsType<DerivedTreeViewItem>(container);
-////                    if (item.ItemCount > 0)
-////                    {
-////                        VerifyItemType(item.ItemContainerGenerator);
-////                    }
-////                }
-////            }
-////        }
-
-////        private void ApplyTemplates(TreeView tree)
-////        {
-////            tree.ApplyTemplate();
-////            tree.Presenter.ApplyTemplate();
-////            ApplyTemplates(tree.Presenter.Panel.Children);
-////        }
-
-////        private void ApplyTemplates(IEnumerable<Control> controls)
-////        {
-////            foreach (TreeViewItem control in controls)
-////            {
-////                control.Template = CreateTreeViewItemTemplate();
-////                control.ApplyTemplate();
-////                control.Presenter.ApplyTemplate();
-////                control.HeaderPresenter.ApplyTemplate();
-////                ApplyTemplates(control.Presenter.Panel.Children);
-////            }
-////        }
-
-////        private TreeViewItem GetItem(TreeView target, params int[] indexes)
-////        {
-////            var c = (ItemsControl)target;
-
-////            foreach (var index in indexes)
-////            {
-////                var item = ((IList)c.Items)[index];
-////                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
-////            }
-
-////            return (TreeViewItem)c;
-////        }
-
-////        private IList<Node> CreateTestTreeData()
-////        {
-////            return new AvaloniaList<Node>
-////            {
-////                new Node
-////                {
-////                    Value = "Root",
-////                    Children = new AvaloniaList<Node>
-////                    {
-////                        new Node
-////                        {
-////                            Value = "Child1",
-////                        },
-////                        new Node
-////                        {
-////                            Value = "Child2",
-////                            Children = new AvaloniaList<Node>
-////                            {
-////                                new Node
-////                                {
-////                                    Value = "Grandchild2a",
-////                                },
-////                            },
-////                        },
-////                        new Node
-////                        {
-////                            Value = "Child3",
-////                        }
-////                    }
-////                }
-////            };
-////        }
-
-////        private void CreateNodeDataTemplate(Control control)
-////        {
-////            control.DataTemplates.Add(new TestTreeDataTemplate());
-////        }
-
-////        private IControlTemplate CreateTreeViewTemplate()
-////        {
-////            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
-////            {
-////                Name = "PART_ItemsPresenter",
-////            }.RegisterInNameScope(scope));
-////        }
-
-////        private IControlTemplate CreateTreeViewItemTemplate()
-////        {
-////            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
-////            {
-////                Children =
-////                {
-////                    new ContentPresenter
-////                    {
-////                        Name = "PART_HeaderPresenter",
-////                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
-////                    }.RegisterInNameScope(scope),
-////                    new ItemsPresenter
-////                    {
-////                        Name = "PART_ItemsPresenter",
-////                    }.RegisterInNameScope(scope)
-////                }
-////            });
-////        }
-
-////        private void ExpandAll(TreeView tree)
-////        {
-////            foreach (var i in tree.ItemContainerGenerator.Containers)
-////            {
-////                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
-////            }
-////        }
-
-////        private List<string> ExtractItemHeader(TreeView tree, int level)
-////        {
-////            return ExtractItemContent(tree.Presenter.Panel, 0, level)
-////                .Select(x => x.Header)
-////                .OfType<TextBlock>()
-////                .Select(x => x.Text)
-////                .ToList();
-////        }
-
-////        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
-////        {
-////            foreach (TreeViewItem container in panel.Children)
-////            {
-////                if (container.Template == null)
-////                {
-////                    container.Template = CreateTreeViewItemTemplate();
-////                    container.ApplyTemplate();
-////                }
-
-////                if (currentLevel == level)
-////                {
-////                    yield return container;
-////                }
-////                else
-////                {
-////                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
-////                    {
-////                        yield return child;
-////                    }
-////                }
-////            }
-////        }
-
-////        private void ClickContainer(Control container, KeyModifiers modifiers)
-////        {
-////            _mouse.Click(container, modifiers: modifiers);
-////        }
-
-////        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
-////        {
-////            foreach (var child in rootNode.Children)
-////            {
-////                var container = (TreeViewItem)treeView.ItemContainerGenerator.Index.ContainerFromItem(child);
-
-////                Assert.True(container.IsSelected);
-////            }
-////        }
-
-////        private IDisposable Application()
-////        {
-////            return UnitTestApplication.Start(
-////                TestServices.MockThreadingInterface.With(
-////                    focusManager: new FocusManager(),
-////                    keyboardDevice: () => new KeyboardDevice(),
-////                    keyboardNavigation: new KeyboardNavigationHandler(),
-////                    inputManager: new InputManager()));
-////        }
-
-////        private class Node : NotifyingBase
-////        {
-////            private IAvaloniaList<Node> _children;
-
-////            public string Value { get; set; }
-
-////            public IAvaloniaList<Node> Children
-////            {
-////                get
-////                {
-////                    return _children;
-////                }
-
-////                set
-////                {
-////                    _children = value;
-////                    RaisePropertyChanged(nameof(Children));
-////                }
-////            }
-////        }
-
-////        private class TestTreeDataTemplate : ITreeDataTemplate
-////        {
-////            public Control Build(object param)
-////            {
-////                var node = (Node)param;
-////                return new TextBlock { Text = node.Value };
-////            }
-
-////            public InstancedBinding ItemsSelector(object item)
-////            {
-////                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
-////                return InstancedBinding.OneWay(obs);
-////            }
-
-////            public bool Match(object data)
-////            {
-////                return data is Node;
-////            }
-////        }
-
-////        private class DerivedTreeView : TreeView
-////        {
-////        }
-
-////        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
-////        {
-////            protected override ITreeItemContainerGenerator CreateTreeItemContainerGenerator() =>
-////                CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-////        }
-
-////        private class DerivedTreeViewItem : TreeViewItem
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator() => CreateTreeItemContainerGenerator<DerivedTreeViewItem>();
-////        }
-
-////        private class TestDataContext : INotifyPropertyChanged
-////        {
-////            private string _selectedItem;
-
-////            public TestDataContext()
-////            {
-////                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
-////            }
-
-////            public ObservableCollection<string> Items { get; }
-
-////            public string SelectedItem
-////            {
-////                get { return _selectedItem; }
-////                set
-////                {
-////                    _selectedItem = value;
-////                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
-////                }
-////            }
-
-////            public event PropertyChangedEventHandler PropertyChanged;
-
-////        }
-////    }
-////}
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Clicking_First_Item_Of_SelectedItems_Should_Select_Only_It()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+
+                ClickContainer(toContainer, KeyModifiers.Shift);
+                AssertChildrenSelected(target, rootNode);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+
+                Assert.True(fromContainer.IsSelected);
+
+                foreach (var child in rootNode.Children)
+                {
+                    if (child == from)
+                    {
+                        continue;
+                    }
+
+                    var container = (TreeViewItem)target.TreeContainerFromItem(child);
+
+                    Assert.False(container.IsSelected);
+                }
+            }
+        }
+
+        [Fact]
+        public void Setting_SelectedItem_Should_Set_Container_Selected()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+                var container = (TreeViewItem)target.TreeContainerFromItem(item);
+
+                Assert.NotNull(container);
+
+                target.SelectedItem = item;
+
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        [Fact]
+        public void Setting_SelectedItem_Should_Raise_SelectedItemChanged_Event()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = tree[0].Children[1].Children[0];
+
+                var called = false;
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.RemovedItems);
+                    Assert.Equal(1, e.AddedItems.Count);
+                    Assert.Same(item, e.AddedItems[0]);
+                    called = true;
+                };
+
+                target.SelectedItem = item;
+                Assert.True(called);
+            }
+        }
+
+        [Fact]
+        public void Bound_SelectedItem_Should_Not_Be_Cleared_when_Changing_Selection()
+        {
+            using (Application())
+            {
+                var dataContext = new TestDataContext();
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    DataContext = dataContext
+                };
+
+                target.Bind(TreeView.ItemsProperty, new Binding("Items"));
+                target.Bind(TreeView.SelectedItemProperty, new Binding("SelectedItem"));
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+
+                var selectedValues = new List<object>();
+
+                dataContext.PropertyChanged += (_, e) =>
+                {
+                    if (e.PropertyName == nameof(TestDataContext.SelectedItem))
+                        selectedValues.Add(dataContext.SelectedItem);
+                };
+                selectedValues.Add(dataContext.SelectedItem);
+
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Left);
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[2], MouseButton.Left);
+
+                Assert.Equal(3, selectedValues.Count);
+                Assert.Equal(new[] { null, "Item 0", "Item 2" }, selectedValues.ToArray());
+            }
+        }
+
+        [Fact]
+        public void LogicalChildren_Should_Be_Set()
+        {
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = new[] { "Foo", "Bar", "Baz " },
+            };
+
+            ApplyTemplates(target);
+
+            var result = target.GetLogicalChildren()
+                .OfType<TreeViewItem>()
+                .Select(x => x.HeaderPresenter.Child)
+                .OfType<TextBlock>()
+                .Select(x => x.Text)
+                .ToList();
+
+            Assert.Equal(new[] { "Foo", "Bar", "Baz " }, result);
+        }
+
+        [Fact]
+        public void DataContexts_Should_Be_Correctly_Set()
+        {
+            var items = new object[]
+            {
+                "Foo",
+                new Node { Value = "Bar" },
+                new TextBlock { Text = "Baz" },
+                new TreeViewItem { Header = "Qux" },
+            };
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                DataContext = "Base",
+                DataTemplates =
+                {
+                    new FuncDataTemplate<Node>((x, _) => new Button { Content = x })
+                },
+                Items = items,
+            };
+
+            ApplyTemplates(target);
+
+            var dataContexts = target.Presenter.Panel.Children
+                .Cast<Control>()
+                .Select(x => x.DataContext)
+                .ToList();
+
+            Assert.Equal(
+                new object[] { items[0], items[1], "Base", "Base" },
+                dataContexts);
+        }
+
+        [Fact]
+        public void Control_Item_Should_Not_Be_NameScope()
+        {
+            var items = new object[]
+            {
+                new TreeViewItem(),
+            };
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = items,
+            };
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            var item = target.Presenter.Panel.LogicalChildren[0];
+            Assert.Null(NameScope.GetNameScope((TreeViewItem)item));
+        }
+
+        [Fact]
+        public void Should_React_To_Children_Changing()
+        {
+            var data = CreateTestTreeData();
+
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = data,
+            };
+
+            var root = new TestRoot(target);
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "Child1", "Child2", "Child3" }, ExtractItemHeader(target, 1));
+            Assert.Equal(new[] { "Grandchild2a" }, ExtractItemHeader(target, 2));
+
+            // Make sure that the binding to Node.Children does not get collected.
+            GC.Collect();
+
+            data[0].Children = new AvaloniaList<Node>
+            {
+                new Node
+                {
+                    Value = "NewChild1",
+                }
+            };
+
+            ApplyTemplates(target);
+
+            Assert.Equal(new[] { "Root" }, ExtractItemHeader(target, 0));
+            Assert.Equal(new[] { "NewChild1" }, ExtractItemHeader(target, 1));
+        }
+
+        [Fact]
+        public void Keyboard_Navigation_Should_Move_To_Last_Selected_Node()
+        {
+            using (Application())
+            {
+                var focus = FocusManager.Instance;
+                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+                var data = CreateTestTreeData();
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = data,
+                };
+
+                var button = new Button();
+
+                var root = new TestRoot
+                {
+                    Child = new StackPanel
+                    {
+                        Children = { target, button },
+                    }
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = data[0].Children[0];
+                var node = target.TreeContainerFromItem(item);
+                Assert.NotNull(node);
+
+                target.SelectedItem = item;
+                node.Focus();
+                Assert.Same(node, focus.Current);
+
+                navigation.Move(focus.Current, NavigationDirection.Next);
+                Assert.Same(button, focus.Current);
+
+                navigation.Move(focus.Current, NavigationDirection.Next);
+                Assert.Same(node, focus.Current);
+            }
+        }
+
+        [Fact]
+        public void Keyboard_Navigation_Should_Not_Crash_If_Selected_Item_Is_not_In_Tree()
+        {
+            using (Application())
+            {
+                var focus = FocusManager.Instance;
+                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+                var data = CreateTestTreeData();
+
+                var selectedNode = new Node { Value = "Out of Tree Selected Item" };
+
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = data,
+                    SelectedItem = selectedNode
+                };
+
+                var button = new Button();
+
+                var root = new TestRoot
+                {
+                    Child = new StackPanel
+                    {
+                        Children = { target, button },
+                    }
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var item = data[0].Children[0];
+                var node = target.TreeContainerFromItem(item);
+                Assert.NotNull(node);
+
+                target.SelectedItem = selectedNode;
+                node.Focus();
+                Assert.Same(node, focus.Current);
+
+                var next = KeyboardNavigationHandler.GetNext(node, NavigationDirection.Previous);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_Should_Select_All_Nodes()
+        {
+            using (UnitTestApplication.Start())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_With_Downward_Range_Selected_Should_Select_All_Nodes()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children[0];
+                var to = rootNode.Children.Last();
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Pressing_SelectAll_Gesture_With_Upward_Range_Selected_Should_Select_All_Nodes()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                ExpandAll(target);
+
+                var rootNode = tree[0];
+
+                var from = rootNode.Children.Last();
+                var to = rootNode.Children[0];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var selectAllGesture = keymap.SelectAll.First();
+
+                var keyEvent = new KeyEventArgs
+                {
+                    RoutedEvent = InputElement.KeyDownEvent,
+                    Key = selectAllGesture.Key,
+                    KeyModifiers = selectAllGesture.KeyModifiers
+                };
+
+                target.RaiseEvent(keyEvent);
+
+                AssertChildrenSelected(target, rootNode);
+            }
+        }
+
+        [Fact]
+        public void Right_Click_On_SelectedItem_Should_Not_Clear_Existing_Selection()
+        {
+            using (UnitTestApplication.Start())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+                AvaloniaLocator.CurrentMutable.Bind<PlatformHotkeyConfiguration>().ToConstant(new Mock<PlatformHotkeyConfiguration>().Object);
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+                target.SelectAll();
+
+                AssertChildrenSelected(target, tree[0]);
+                Assert.Equal(5, target.SelectedItems.Count);
+
+                _mouse.Click((Interactive)target.Presenter.Panel.Children[0], MouseButton.Right);
+
+                Assert.Equal(5, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Right_Click_On_UnselectedItem_Should_Clear_Existing_Selection()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var to = rootNode.Children[0];
+                var then = rootNode.Children[1];
+
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(rootNode);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+                var thenContainer = (TreeViewItem)target.TreeContainerFromItem(then);
+
+                ClickContainer(fromContainer, KeyModifiers.None);
+                ClickContainer(toContainer, KeyModifiers.Shift);
+
+                Assert.Equal(2, target.SelectedItems.Count);
+
+                _mouse.Click(thenContainer, MouseButton.Right);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Shift_Right_Click_Should_Not_Select_Multiple()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var from = rootNode.Children[0];
+                var to = rootNode.Children[1];
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                _mouse.Click(fromContainer);
+                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Shift);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void Ctrl_Right_Click_Should_Not_Select_Multiple()
+        {
+            using (Application())
+            {
+                var tree = CreateTestTreeData();
+                var target = new TreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    Items = tree,
+                    SelectionMode = SelectionMode.Multiple,
+                };
+
+                var visualRoot = new TestRoot();
+                visualRoot.Child = target;
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+                target.ExpandSubTree((TreeViewItem)target.Presenter.Panel.Children[0]);
+
+                var rootNode = tree[0];
+                var from = rootNode.Children[0];
+                var to = rootNode.Children[1];
+                var fromContainer = (TreeViewItem)target.TreeContainerFromItem(from);
+                var toContainer = (TreeViewItem)target.TreeContainerFromItem(to);
+
+                _mouse.Click(fromContainer);
+                _mouse.Click(toContainer, MouseButton.Right, modifiers: KeyModifiers.Control);
+
+                Assert.Equal(1, target.SelectedItems.Count);
+            }
+        }
+
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set()
+        {
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
+        {
+            var tree = CreateTestTreeData();
+            var target = new DerivedTreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
+        [Fact]
+        public void Adding_Node_To_Removed_And_ReAdded_Parent_Should_Not_Crash()
+        {
+            // Issue #2985
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            var parent = tree[0];
+            var node = parent.Children[1];
+
+            parent.Children.Remove(node);
+            parent.Children.Add(node);
+
+            var item = target.TreeContainerFromItem(node);
+            ApplyTemplates(new[] { item });
+
+            // #2985 causes ArgumentException here.
+            node.Children.Add(new Node());
+        }
+
+        [Fact]
+        public void Auto_Expanding_In_Style_Should_Not_Break_Range_Selection()
+        {
+            // Issue #2980.
+            using (Application())
+            {
+                var target = new DerivedTreeView
+                {
+                    Template = CreateTreeViewTemplate(),
+                    SelectionMode = SelectionMode.Multiple,
+                    Items = new List<Node>
+                {
+                    new Node { Value = "Root1", },
+                    new Node { Value = "Root2", },
+                },
+                };
+
+                var visualRoot = new TestRoot
+                {
+                    Styles =
+                    {
+                        new Style(x => x.OfType<TreeViewItem>())
+                        {
+                            Setters =
+                            {
+                                new Setter(TreeViewItem.IsExpandedProperty, true),
+                            },
+                        },
+                    },
+                    Child = target,
+                };
+
+                CreateNodeDataTemplate(target);
+                ApplyTemplates(target);
+
+                _mouse.Click(GetItem(target, 0));
+                _mouse.Click(GetItem(target, 1), modifiers: KeyModifiers.Shift);
+            }
+        }
+
+        [Fact]
+        public void Removing_TreeView_From_Root_Should_Preserve_TreeViewItems()
+        {
+            // Issue #3328
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(5, target.GetRealizedTreeContainers().Count());
+
+            root.Child = null;
+
+            Assert.Equal(5, target.GetRealizedTreeContainers().Count());
+            Assert.Equal(1, target.Presenter.Panel.Children.Count);
+
+            var rootNode = Assert.IsType<TreeViewItem>(target.Presenter.Panel.Children[0]);
+            Assert.Equal(3, rootNode.GetRealizedContainers().Count());
+            Assert.Equal(3, rootNode.Presenter.Panel.Children.Count);
+
+            var child2Node = Assert.IsType<TreeViewItem>(rootNode.Presenter.Panel.Children[1]);
+            Assert.Equal(1, child2Node.GetRealizedContainers().Count());
+            Assert.Equal(1, child2Node.Presenter.Panel.Children.Count);
+        }
+
+        [Fact]
+        public void Clearing_TreeView_Items_Clears_Index()
+        {
+            // Issue #3551
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var root = new TestRoot();
+            root.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+
+            var rootNode = tree[0];
+            var container = (TreeViewItem)target.TreeContainerFromItem(rootNode);
+
+            Assert.NotNull(container);
+
+            root.Child = null;
+
+            tree.Clear();
+
+            Assert.Empty(target.GetRealizedContainers());
+        }
+
+        [Fact]
+        public void Can_Use_Derived_TreeViewItem()
+        {
+            var tree = CreateTestTreeData();
+            var target = new DerivedTreeViewWithDerivedTreeViewItems
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            ApplyTemplates(target);
+
+            // Verify that all items are DerivedTreeViewItem
+            foreach (var container in target.GetRealizedTreeContainers())
+            {
+                Assert.IsType<DerivedTreeViewItem>(container);
+            }
+        }
+
+        private void ApplyTemplates(TreeView tree)
+        {
+            tree.ApplyTemplate();
+            tree.Presenter.ApplyTemplate();
+            ApplyTemplates(tree.Presenter.Panel.Children);
+        }
+
+        private void ApplyTemplates(IEnumerable<Control> controls)
+        {
+            foreach (TreeViewItem control in controls)
+            {
+                control.Template = CreateTreeViewItemTemplate();
+                control.ApplyTemplate();
+                control.Presenter.ApplyTemplate();
+                ((ContentPresenter)control.HeaderPresenter).UpdateChild();
+                ApplyTemplates(control.Presenter.Panel.Children);
+            }
+        }
+
+        private TreeViewItem GetItem(TreeView target, params int[] indexes)
+        {
+            var c = (ItemsControl)target;
+
+            foreach (var index in indexes)
+            {
+                var item = ((IList)c.Items)[index];
+                c = (ItemsControl)target.TreeContainerFromItem(item);
+            }
+
+            return (TreeViewItem)c;
+        }
+
+        private IList<Node> CreateTestTreeData()
+        {
+            return new AvaloniaList<Node>
+            {
+                new Node
+                {
+                    Value = "Root",
+                    Children = new AvaloniaList<Node>
+                    {
+                        new Node
+                        {
+                            Value = "Child1",
+                        },
+                        new Node
+                        {
+                            Value = "Child2",
+                            Children = new AvaloniaList<Node>
+                            {
+                                new Node
+                                {
+                                    Value = "Grandchild2a",
+                                },
+                            },
+                        },
+                        new Node
+                        {
+                            Value = "Child3",
+                        }
+                    }
+                }
+            };
+        }
+
+        private void CreateNodeDataTemplate(Control control)
+        {
+            control.DataTemplates.Add(new TestTreeDataTemplate());
+        }
+
+        private IControlTemplate CreateTreeViewTemplate()
+        {
+            return new FuncControlTemplate<TreeView>((parent, scope) => new ItemsPresenter
+            {
+                Name = "PART_ItemsPresenter",
+            }.RegisterInNameScope(scope));
+        }
+
+        private IControlTemplate CreateTreeViewItemTemplate()
+        {
+            return new FuncControlTemplate<TreeViewItem>((parent, scope) => new Panel
+            {
+                Children =
+                {
+                    new ContentPresenter
+                    {
+                        Name = "PART_HeaderPresenter",
+                        [~ContentPresenter.ContentProperty] = parent[~TreeViewItem.HeaderProperty],
+                        [~ContentPresenter.ContentTemplateProperty] = parent[~TreeViewItem.HeaderTemplateProperty],
+                    }.RegisterInNameScope(scope),
+                    new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                    }.RegisterInNameScope(scope)
+                }
+            });
+        }
+
+        private void ExpandAll(TreeView tree)
+        {
+            foreach (var i in tree.GetRealizedContainers())
+            {
+                tree.ExpandSubTree((TreeViewItem)i);
+            }
+        }
+
+        private List<string> ExtractItemHeader(TreeView tree, int level)
+        {
+            return ExtractItemContent(tree.Presenter.Panel, 0, level)
+                .Select(x => x.HeaderPresenter.Child)
+                .OfType<TextBlock>()
+                .Select(x => x.Text)
+                .ToList();
+        }
+
+        private IEnumerable<TreeViewItem> ExtractItemContent(Panel panel, int currentLevel, int level)
+        {
+            foreach (TreeViewItem container in panel.Children)
+            {
+                if (container.Template == null)
+                {
+                    container.Template = CreateTreeViewItemTemplate();
+                    container.ApplyTemplate();
+                }
+
+                if (currentLevel == level)
+                {
+                    yield return container;
+                }
+                else
+                {
+                    foreach (var child in ExtractItemContent(container.Presenter.Panel, currentLevel + 1, level))
+                    {
+                        yield return child;
+                    }
+                }
+            }
+        }
+
+        private void ClickContainer(Control container, KeyModifiers modifiers)
+        {
+            _mouse.Click(container, modifiers: modifiers);
+        }
+
+        private void AssertChildrenSelected(TreeView treeView, Node rootNode)
+        {
+            foreach (var child in rootNode.Children)
+            {
+                var container = (TreeViewItem)treeView.TreeContainerFromItem(child);
+
+                Assert.True(container.IsSelected);
+            }
+        }
+
+        private IDisposable Application()
+        {
+            return UnitTestApplication.Start(
+                TestServices.MockThreadingInterface.With(
+                    focusManager: new FocusManager(),
+                    keyboardDevice: () => new KeyboardDevice(),
+                    keyboardNavigation: new KeyboardNavigationHandler(),
+                    inputManager: new InputManager()));
+        }
+
+        private class Node : NotifyingBase
+        {
+            private IAvaloniaList<Node> _children;
+
+            public string Value { get; set; }
+
+            public IAvaloniaList<Node> Children
+            {
+                get
+                {
+                    return _children;
+                }
+
+                set
+                {
+                    _children = value;
+                    RaisePropertyChanged(nameof(Children));
+                }
+            }
+        }
+
+        private class TestTreeDataTemplate : ITreeDataTemplate
+        {
+            public Control Build(object param)
+            {
+                var node = (Node)param;
+                return new TextBlock { Text = node.Value };
+            }
+
+            public InstancedBinding ItemsSelector(object item)
+            {
+                var obs = ExpressionObserver.Create(item, o => (o as Node).Children);
+                return InstancedBinding.OneWay(obs);
+            }
+
+            public bool Match(object data)
+            {
+                return data is Node;
+            }
+        }
+
+        private class DerivedTreeView : TreeView
+        {
+        }
+
+        private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
+        {
+            protected internal override Control CreateContainerOverride() => new DerivedTreeViewItem();
+        }
+
+        private class DerivedTreeViewItem : TreeViewItem
+        {
+        }
+
+        private class TestDataContext : INotifyPropertyChanged
+        {
+            private string _selectedItem;
+
+            public TestDataContext()
+            {
+                Items = new ObservableCollection<string>(Enumerable.Range(0, 5).Select(i => $"Item {i}"));
+            }
+
+            public ObservableCollection<string> Items { get; }
+
+            public string SelectedItem
+            {
+                get { return _selectedItem; }
+                set
+                {
+                    _selectedItem = value;
+                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(SelectedItem)));
+                }
+            }
+
+            public event PropertyChangedEventHandler PropertyChanged;
+
+        }
+    }
+}

From 4a92fadd3404aed55abd4c92aaaa7a7f0025c33c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 12:15:13 +0100
Subject: [PATCH 031/157] Fix StyleIncludeTests.

Wasn't finding `RelativeSource` type at times.
---
 src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github        | 2 +-
 .../Xaml/StyleIncludeTests.cs                               | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
index 5e498f8bcc..491de981dd 160000
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
@@ -1 +1 @@
-Subproject commit 5e498f8bcca403a34aff5efc825cbb4e12b7fa8e
+Subproject commit 491de981dd4433ee58bc9540e2cd4a5d168f8168
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
index d76e51f419..929529e97a 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleIncludeTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Controls;
+using Avalonia.Data;
 using Avalonia.Markup.Xaml.Styling;
 using Avalonia.Markup.Xaml.XamlIl.Runtime;
 using Avalonia.Media;
@@ -15,6 +16,11 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml;
 
 public class StyleIncludeTests
 {
+    public StyleIncludeTests()
+    {
+        System.Runtime.CompilerServices.RuntimeHelpers.RunClassConstructor(typeof(RelativeSource).TypeHandle);
+    }
+
     [Fact]
     public void StyleInclude_Is_Built()
     {

From 84abb69b61208161336af2a54b523f3f64cf9c53 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 12:23:36 +0100
Subject: [PATCH 032/157] Reinstated DialogsPage.

---
 samples/ControlCatalog/Pages/DialogsPage.xaml |   2 +-
 .../ControlCatalog/Pages/DialogsPage.xaml.cs  | 590 +++++++++---------
 2 files changed, 296 insertions(+), 296 deletions(-)

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml b/samples/ControlCatalog/Pages/DialogsPage.xaml
index cc23ef796a..5325534909 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml
@@ -46,7 +46,7 @@
                Classes="h2"
                IsVisible="False"
                Text="Last picker results:" />
-    <ItemsPresenter x:Name="PickerLastResults" />
+    <ItemsControl x:Name="PickerLastResults" />
 
     <TextBox Name="BookmarkContainer" Watermark="Bookmark" />
     <TextBox Name="OpenedFileContent"
diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 41a5b86ebd..3f1264fd32 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -24,301 +24,301 @@ namespace ControlCatalog.Pages
         {
             this.InitializeComponent();
 
-////            var results = this.Get<ItemsPresenter>("PickerLastResults");
-////            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
-////            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
-////            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
-////            var openMultiple = this.Get<CheckBox>("OpenMultiple");
-
-////            IStorageFolder? lastSelectedDirectory = null;
-
-////            List<FileDialogFilter> GetFilters()
-////            {
-////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-////                    return new List<FileDialogFilter>();
-////                return  new List<FileDialogFilter>
-////                {
-////                    new FileDialogFilter
-////                    {
-////                        Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
-////                    },
-////                    new FileDialogFilter
-////                    {
-////                        Name = "All files",
-////                        Extensions = new List<string> {"*"}
-////                    }
-////                };
-////            }
-
-////            List<FilePickerFileType>? GetFileTypes()
-////            {
-////                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
-////                    return null;
-////                return new List<FilePickerFileType>
-////                {
-////                    FilePickerFileTypes.All,
-////                    FilePickerFileTypes.TextPlain
-////                };
-////            }
-
-////            this.Get<Button>("OpenFile").Click += async delegate
-////            {
-////                // Almost guaranteed to exist
-////                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
-////                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
-////                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
-
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Open file",
-////                    Filters = GetFilters(),
-////                    Directory = initialDirectory,
-////                    InitialFileName = initialFileName
-////                }.ShowAsync(GetWindow());
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("OpenMultipleFiles").Click += async delegate
-////            {
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Open multiple files",
-////                    Filters = GetFilters(),
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    AllowMultiple = true
-////                }.ShowAsync(GetWindow());
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("SaveFile").Click += async delegate
-////            {
-////                var filters = GetFilters();
-////                var result = await new SaveFileDialog()
-////                {
-////                    Title = "Save file",
-////                    Filters = filters,
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    DefaultExtension = filters?.Any() == true ? "txt" : null,
-////                    InitialFileName = "test.txt"
-////                }.ShowAsync(GetWindow());
-////                results.Items = new[] { result };
-////                resultsVisible.IsVisible = result != null;
-////            };
-////            this.Get<Button>("SelectFolder").Click += async delegate
-////            {
-////                var result = await new OpenFolderDialog()
-////                {
-////                    Title = "Select folder",
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
-////                }.ShowAsync(GetWindow());
-////                if (string.IsNullOrEmpty(result))
-////                {
-////                    resultsVisible.IsVisible = false;
-////                }
-////                else
-////                {
-////                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
-////                    results.Items = new[] { result };
-////                    resultsVisible.IsVisible = true;
-////                }
-////            };
-////            this.Get<Button>("OpenBoth").Click += async delegate
-////            {
-////                var result = await new OpenFileDialog()
-////                {
-////                    Title = "Select both",
-////                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
-////                    AllowMultiple = true
-////                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
-////                {
-////                    AllowDirectorySelection = true
-////                });
-////                results.Items = result;
-////                resultsVisible.IsVisible = result?.Any() == true;
-////            };
-////            this.Get<Button>("DecoratedWindow").Click += delegate
-////            {
-////                new DecoratedWindow().Show();
-////            };
-////            this.Get<Button>("DecoratedWindowDialog").Click += delegate
-////            {
-////                _ = new DecoratedWindow().ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("Dialog").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-////                window.Height = 200;
-////                _ = window.ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("DialogNoTaskbar").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-////                window.Height = 200;
-////                window.ShowInTaskbar = false;
-////                _ = window.ShowDialog(GetWindow());
-////            };
-////            this.Get<Button>("OwnedWindow").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-
-////                window.Show(GetWindow());
-////            };
-
-////            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
-////            {
-////                var window = CreateSampleWindow();
-
-////                window.ShowInTaskbar = false;
-
-////                window.Show(GetWindow());
-////            };
-
-////            this.Get<Button>("OpenFilePicker").Click += async delegate
-////            {
-////                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
-////                {
-////                    Title = "Open file",
-////                    FileTypeFilter = GetFileTypes(),
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    AllowMultiple = openMultiple.IsChecked == true
-////                });
-
-////                await SetPickerResult(result);
-////            };
-////            this.Get<Button>("SaveFilePicker").Click += async delegate
-////            {
-////                var fileTypes = GetFileTypes();
-////                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
-////                {
-////                    Title = "Save file",
-////                    FileTypeChoices = fileTypes,
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    SuggestedFileName = "FileName",
-////                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
-////                    ShowOverwritePrompt = false
-////                });
-
-////                if (file is not null && file.CanOpenWrite)
-////                {
-////                    // Sync disposal of StreamWriter is not supported on WASM
-////#if NET6_0_OR_GREATER
-////                    await using var stream = await file.OpenWriteAsync();
-////                    await using var reader = new System.IO.StreamWriter(stream);
-////#else
-////                    using var stream = await file.OpenWriteAsync();
-////                    using var reader = new System.IO.StreamWriter(stream);
-////#endif
-////                    await reader.WriteLineAsync(openedFileContent.Text);
-
-////                    lastSelectedDirectory = await file.GetParentAsync();
-////                }
-
-////                await SetPickerResult(file is null ? null : new [] {file});
-////            };
-////            this.Get<Button>("OpenFolderPicker").Click += async delegate
-////            {
-////                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
-////                {
-////                    Title = "Folder file",
-////                    SuggestedStartLocation = lastSelectedDirectory,
-////                    AllowMultiple = openMultiple.IsChecked == true
-////                });
-
-////                await SetPickerResult(folders);
-
-////                lastSelectedDirectory = folders.FirstOrDefault();
-////            };
-////            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
-////            {
-////                var file = bookmarkContainer.Text is not null
-////                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
-////                    : null;
-
-////                await SetPickerResult(file is null ? null : new[] { file });
-////            };
-////            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
-////            {
-////                var folder = bookmarkContainer.Text is not null
-////                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
-////                    : null;
-
-////                await SetPickerResult(folder is null ? null : new[] { folder });
-                
-////                lastSelectedDirectory = folder;
-////            };
-
-////            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
-////            {
-////                items ??= Array.Empty<IStorageItem>();
-////                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
-////                var mappedResults = new List<string>();
-
-////                if (items.FirstOrDefault() is IStorageItem item)
-////                {
-////                    var resultText = item is IStorageFile ? "File:" : "Folder:";
-////                    resultText += Environment.NewLine;
-
-////                    var props = await item.GetBasicPropertiesAsync();
-////                    resultText += @$"Size: {props.Size}
-////DateCreated: {props.DateCreated}
-////DateModified: {props.DateModified}
-////CanBookmark: {item.CanBookmark}
-////";
-////                    if (item is IStorageFile file)
-////                    {
-////                        resultText += @$"
-////CanOpenRead: {file.CanOpenRead}
-////CanOpenWrite: {file.CanOpenWrite}
-////Content:
-////";
-////                        if (file.CanOpenRead)
-////                        {
-////#if NET6_0_OR_GREATER
-////                            await using var stream = await file.OpenReadAsync();
-////#else
-////                            using var stream = await file.OpenReadAsync();
-////#endif
-////                            using var reader = new System.IO.StreamReader(stream);
-
-////                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
-////                            const int length = 10000;
-////                            var buffer = ArrayPool<char>.Shared.Rent(length);
-////                            try
-////                            {
-////                                var charsRead = await reader.ReadAsync(buffer, 0, length);
-////                                resultText += new string(buffer, 0, charsRead);
-////                            }
-////                            finally
-////                            {
-////                                ArrayPool<char>.Shared.Return(buffer);
-////                            }
-////                        }
-////                    }
-
-////                    openedFileContent.Text = resultText;
-
-////                    lastSelectedDirectory = await item.GetParentAsync();
-////                    if (lastSelectedDirectory is not null)
-////                    {
-////                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
-////                    }
-
-////                    foreach (var selectedItem in items)
-////                    {
-////                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
-////                        if (selectedItem is IStorageFolder folder)
-////                        {
-////                            foreach (var innerItems in await folder.GetItemsAsync())
-////                            {
-////                                mappedResults.Add("++> " + FullPathOrName(innerItems));
-////                            }
-////                        }
-////                    }
-////                }
-
-////                results.Items = mappedResults;
-////                resultsVisible.IsVisible = mappedResults.Any();
-////            }
+            var results = this.Get<ItemsControl>("PickerLastResults");
+            var resultsVisible = this.Get<TextBlock>("PickerLastResultsVisible");
+            var bookmarkContainer = this.Get<TextBox>("BookmarkContainer");
+            var openedFileContent = this.Get<TextBox>("OpenedFileContent");
+            var openMultiple = this.Get<CheckBox>("OpenMultiple");
+
+            IStorageFolder? lastSelectedDirectory = null;
+
+            List<FileDialogFilter> GetFilters()
+            {
+                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+                    return new List<FileDialogFilter>();
+                return new List<FileDialogFilter>
+                            {
+                                new FileDialogFilter
+                                {
+                                    Name = "Text files (.txt)", Extensions = new List<string> {"txt"}
+                                },
+                                new FileDialogFilter
+                                {
+                                    Name = "All files",
+                                    Extensions = new List<string> {"*"}
+                                }
+                            };
+            }
+
+            List<FilePickerFileType>? GetFileTypes()
+            {
+                if (this.Get<CheckBox>("UseFilters").IsChecked != true)
+                    return null;
+                return new List<FilePickerFileType>
+                            {
+                                FilePickerFileTypes.All,
+                                FilePickerFileTypes.TextPlain
+                            };
+            }
+
+            this.Get<Button>("OpenFile").Click += async delegate
+            {
+                // Almost guaranteed to exist
+                var uri = Assembly.GetEntryAssembly()?.GetModules().FirstOrDefault()?.FullyQualifiedName;
+                var initialFileName = uri == null ? null : System.IO.Path.GetFileName(uri);
+                var initialDirectory = uri == null ? null : System.IO.Path.GetDirectoryName(uri);
+
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Open file",
+                    Filters = GetFilters(),
+                    Directory = initialDirectory,
+                    InitialFileName = initialFileName
+                }.ShowAsync(GetWindow());
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("OpenMultipleFiles").Click += async delegate
+            {
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Open multiple files",
+                    Filters = GetFilters(),
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    AllowMultiple = true
+                }.ShowAsync(GetWindow());
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("SaveFile").Click += async delegate
+            {
+                var filters = GetFilters();
+                var result = await new SaveFileDialog()
+                {
+                    Title = "Save file",
+                    Filters = filters,
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    DefaultExtension = filters?.Any() == true ? "txt" : null,
+                    InitialFileName = "test.txt"
+                }.ShowAsync(GetWindow());
+                results.Items = new[] { result };
+                resultsVisible.IsVisible = result != null;
+            };
+            this.Get<Button>("SelectFolder").Click += async delegate
+            {
+                var result = await new OpenFolderDialog()
+                {
+                    Title = "Select folder",
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null
+                }.ShowAsync(GetWindow());
+                if (string.IsNullOrEmpty(result))
+                {
+                    resultsVisible.IsVisible = false;
+                }
+                else
+                {
+                    lastSelectedDirectory = new BclStorageFolder(new System.IO.DirectoryInfo(result));
+                    results.Items = new[] { result };
+                    resultsVisible.IsVisible = true;
+                }
+            };
+            this.Get<Button>("OpenBoth").Click += async delegate
+            {
+                var result = await new OpenFileDialog()
+                {
+                    Title = "Select both",
+                    Directory = lastSelectedDirectory?.TryGetUri(out var path) == true ? path.LocalPath : null,
+                    AllowMultiple = true
+                }.ShowManagedAsync(GetWindow(), new ManagedFileDialogOptions
+                {
+                    AllowDirectorySelection = true
+                });
+                results.Items = result;
+                resultsVisible.IsVisible = result?.Any() == true;
+            };
+            this.Get<Button>("DecoratedWindow").Click += delegate
+            {
+                new DecoratedWindow().Show();
+            };
+            this.Get<Button>("DecoratedWindowDialog").Click += delegate
+            {
+                _ = new DecoratedWindow().ShowDialog(GetWindow());
+            };
+            this.Get<Button>("Dialog").Click += delegate
+            {
+                var window = CreateSampleWindow();
+                window.Height = 200;
+                _ = window.ShowDialog(GetWindow());
+            };
+            this.Get<Button>("DialogNoTaskbar").Click += delegate
+            {
+                var window = CreateSampleWindow();
+                window.Height = 200;
+                window.ShowInTaskbar = false;
+                _ = window.ShowDialog(GetWindow());
+            };
+            this.Get<Button>("OwnedWindow").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.Show(GetWindow());
+            };
+
+            this.Get<Button>("OwnedWindowNoTaskbar").Click += delegate
+            {
+                var window = CreateSampleWindow();
+
+                window.ShowInTaskbar = false;
+
+                window.Show(GetWindow());
+            };
+
+            this.Get<Button>("OpenFilePicker").Click += async delegate
+            {
+                var result = await GetStorageProvider().OpenFilePickerAsync(new FilePickerOpenOptions()
+                {
+                    Title = "Open file",
+                    FileTypeFilter = GetFileTypes(),
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    AllowMultiple = openMultiple.IsChecked == true
+                });
+
+                await SetPickerResult(result);
+            };
+            this.Get<Button>("SaveFilePicker").Click += async delegate
+            {
+                var fileTypes = GetFileTypes();
+                var file = await GetStorageProvider().SaveFilePickerAsync(new FilePickerSaveOptions()
+                {
+                    Title = "Save file",
+                    FileTypeChoices = fileTypes,
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    SuggestedFileName = "FileName",
+                    DefaultExtension = fileTypes?.Any() == true ? "txt" : null,
+                    ShowOverwritePrompt = false
+                });
+
+                if (file is not null && file.CanOpenWrite)
+                {
+                    // Sync disposal of StreamWriter is not supported on WASM
+#if NET6_0_OR_GREATER
+                    await using var stream = await file.OpenWriteAsync();
+                    await using var reader = new System.IO.StreamWriter(stream);
+#else
+                                using var stream = await file.OpenWriteAsync();
+                                using var reader = new System.IO.StreamWriter(stream);
+#endif
+                    await reader.WriteLineAsync(openedFileContent.Text);
+
+                    lastSelectedDirectory = await file.GetParentAsync();
+                }
+
+                await SetPickerResult(file is null ? null : new[] { file });
+            };
+            this.Get<Button>("OpenFolderPicker").Click += async delegate
+            {
+                var folders = await GetStorageProvider().OpenFolderPickerAsync(new FolderPickerOpenOptions()
+                {
+                    Title = "Folder file",
+                    SuggestedStartLocation = lastSelectedDirectory,
+                    AllowMultiple = openMultiple.IsChecked == true
+                });
+
+                await SetPickerResult(folders);
+
+                lastSelectedDirectory = folders.FirstOrDefault();
+            };
+            this.Get<Button>("OpenFileFromBookmark").Click += async delegate
+            {
+                var file = bookmarkContainer.Text is not null
+                    ? await GetStorageProvider().OpenFileBookmarkAsync(bookmarkContainer.Text)
+                    : null;
+
+                await SetPickerResult(file is null ? null : new[] { file });
+            };
+            this.Get<Button>("OpenFolderFromBookmark").Click += async delegate
+            {
+                var folder = bookmarkContainer.Text is not null
+                    ? await GetStorageProvider().OpenFolderBookmarkAsync(bookmarkContainer.Text)
+                    : null;
+
+                await SetPickerResult(folder is null ? null : new[] { folder });
+
+                lastSelectedDirectory = folder;
+            };
+
+            async Task SetPickerResult(IReadOnlyCollection<IStorageItem>? items)
+            {
+                items ??= Array.Empty<IStorageItem>();
+                bookmarkContainer.Text = items.FirstOrDefault(f => f.CanBookmark) is { } f ? await f.SaveBookmarkAsync() : "Can't bookmark";
+                var mappedResults = new List<string>();
+
+                if (items.FirstOrDefault() is IStorageItem item)
+                {
+                    var resultText = item is IStorageFile ? "File:" : "Folder:";
+                    resultText += Environment.NewLine;
+
+                    var props = await item.GetBasicPropertiesAsync();
+                    resultText += @$"Size: {props.Size}
+            DateCreated: {props.DateCreated}
+            DateModified: {props.DateModified}
+            CanBookmark: {item.CanBookmark}
+            ";
+                    if (item is IStorageFile file)
+                    {
+                        resultText += @$"
+            CanOpenRead: {file.CanOpenRead}
+            CanOpenWrite: {file.CanOpenWrite}
+            Content:
+            ";
+                        if (file.CanOpenRead)
+                        {
+#if NET6_0_OR_GREATER
+                            await using var stream = await file.OpenReadAsync();
+#else
+                                        using var stream = await file.OpenReadAsync();
+#endif
+                            using var reader = new System.IO.StreamReader(stream);
+
+                            // 4GB file test, shouldn't load more than 10000 chars into a memory.
+                            const int length = 10000;
+                            var buffer = ArrayPool<char>.Shared.Rent(length);
+                            try
+                            {
+                                var charsRead = await reader.ReadAsync(buffer, 0, length);
+                                resultText += new string(buffer, 0, charsRead);
+                            }
+                            finally
+                            {
+                                ArrayPool<char>.Shared.Return(buffer);
+                            }
+                        }
+                    }
+
+                    openedFileContent.Text = resultText;
+
+                    lastSelectedDirectory = await item.GetParentAsync();
+                    if (lastSelectedDirectory is not null)
+                    {
+                        mappedResults.Add(FullPathOrName(lastSelectedDirectory));
+                    }
+
+                    foreach (var selectedItem in items)
+                    {
+                        mappedResults.Add("+> " + FullPathOrName(selectedItem));
+                        if (selectedItem is IStorageFolder folder)
+                        {
+                            foreach (var innerItems in await folder.GetItemsAsync())
+                            {
+                                mappedResults.Add("++> " + FullPathOrName(innerItems));
+                            }
+                        }
+                    }
+                }
+
+                results.Items = mappedResults;
+                resultsVisible.IsVisible = mappedResults.Any();
+            }
         }
 
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)

From 56db1dbd61ea0af9624b2d30210c2204a82f8a6c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sun, 4 Dec 2022 16:39:51 +0100
Subject: [PATCH 033/157] Remove unneeded change handler.

---
 src/Avalonia.Controls/ItemsControl.cs | 14 --------------
 1 file changed, 14 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 645abf50b3..6bbc608644 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -92,7 +92,6 @@ namespace Avalonia.Controls
         static ItemsControl()
         {
             ItemsProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemsChanged(e));
-            ItemTemplateProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemTemplateChanged(e));
         }
 
         /// <summary>
@@ -647,19 +646,6 @@ namespace Avalonia.Controls
             return _displayMemberItemTemplate;
         }
 
-        /// <summary>
-        /// Called when the <see cref="ItemTemplate"/> changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private void ItemTemplateChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (_itemContainerGenerator != null)
-            {
-                ////_itemContainerGenerator.ItemTemplate = (IDataTemplate?)e.NewValue;
-                // TODO: Rebuild the item containers.
-            }
-        }
-
         private void UpdateItemCount()
         {
             if (Items == null)

From c99307c6fa99f6930e55285f3ec20af947f9e961 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 09:41:31 +0100
Subject: [PATCH 034/157] Use more consistent naming.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 2 +-
 src/Avalonia.Controls/ItemsControl.cs                      | 2 +-
 src/Avalonia.Controls/ListBox.cs                           | 2 +-
 src/Avalonia.Controls/TabControl.cs                        | 2 +-
 src/Avalonia.Controls/TreeView.cs                          | 2 +-
 src/Avalonia.Controls/TreeViewItem.cs                      | 2 +-
 tests/Avalonia.Controls.UnitTests/TreeViewTests.cs         | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index 1cf40d335f..fe8dda3b98 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -27,7 +27,7 @@ namespace Avalonia.Controls.Generators
         /// calling this method, <see cref="PrepareItemContainer(Control, object, int)"/> should
         /// be called to prepare the container to display the specified item.
         /// </remarks>
-        public Control CreateContainer() => _owner.CreateContainerOverride();
+        public Control CreateContainer() => _owner.CreateContainerForItemOverride();
 
         /// <summary>
         /// Determines whether the specified item is (or is eligible to be) its own container.
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6bbc608644..b512d3583c 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -265,7 +265,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Creates or a container that can be used to display an item.
         /// </summary>
-        protected internal virtual Control CreateContainerOverride() => new ContentPresenter();
+        protected internal virtual Control CreateContainerForItemOverride() => new ContentPresenter();
 
         /// <summary>
         /// Prepares the specified element to display the specified item.
diff --git a/src/Avalonia.Controls/ListBox.cs b/src/Avalonia.Controls/ListBox.cs
index 78a2d5d990..8b1a307182 100644
--- a/src/Avalonia.Controls/ListBox.cs
+++ b/src/Avalonia.Controls/ListBox.cs
@@ -103,7 +103,7 @@ namespace Avalonia.Controls
         /// </summary>
         public void UnselectAll() => Selection.Clear();
 
-        protected internal override Control CreateContainerOverride() => new ListBoxItem();
+        protected internal override Control CreateContainerForItemOverride() => new ListBoxItem();
 
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
diff --git a/src/Avalonia.Controls/TabControl.cs b/src/Avalonia.Controls/TabControl.cs
index a6085e53cd..33089344e8 100644
--- a/src/Avalonia.Controls/TabControl.cs
+++ b/src/Avalonia.Controls/TabControl.cs
@@ -149,7 +149,7 @@ namespace Avalonia.Controls
             return RegisterContentPresenter(presenter);
         }
 
-        protected internal override Control CreateContainerOverride() => new TabItem();
+        protected internal override Control CreateContainerForItemOverride() => new TabItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabItem;
 
         protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index c3e891149a..a1cf3cdb53 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -465,7 +465,7 @@ namespace Avalonia.Controls
             return (false, null);
         }
 
-        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
         /// <inheritdoc/>
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 3ff34a14b1..6081fef4e6 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -90,7 +90,7 @@ namespace Avalonia.Controls
 
         internal TreeView? TreeViewOwner => _treeView;
 
-        protected internal override Control CreateContainerOverride() => new TreeViewItem();
+        protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
         /// <inheritdoc/>
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index b9a6566116..bcf719d2bb 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1406,7 +1406,7 @@ namespace Avalonia.Controls.UnitTests
 
         private class DerivedTreeViewWithDerivedTreeViewItems : TreeView
         {
-            protected internal override Control CreateContainerOverride() => new DerivedTreeViewItem();
+            protected internal override Control CreateContainerForItemOverride() => new DerivedTreeViewItem();
         }
 
         private class DerivedTreeViewItem : TreeViewItem

From be2da5cc21e6d45322408376bc1897f5dcfd3e4b Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 09:50:44 +0100
Subject: [PATCH 035/157] Reimplemented commented-out code.

---
 src/Avalonia.Controls/TreeView.cs | 42 +++++++++----------------------
 1 file changed, 12 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index a1cf3cdb53..0c0de9d544 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -468,6 +468,18 @@ namespace Avalonia.Controls
         protected internal override Control CreateContainerForItemOverride() => new TreeViewItem();
         protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TreeViewItem;
 
+        protected internal override void PrepareContainerForItemOverride(Control container, object? item, int index)
+        {
+            base.PrepareContainerForItemOverride(container, item, index);
+
+            if (item == SelectedItem)
+            {
+                MarkContainerSelected(container, true);
+                if (AutoScrollToSelectedItem)
+                    Dispatcher.UIThread.Post(container.BringIntoView);
+            }
+        }
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {
@@ -831,36 +843,6 @@ namespace Avalonia.Controls
             return item?.TreeViewOwner == this ? item : null;
         }
 
-        /// <summary>
-        /// Called when a new item container is materialized, to set its selected state.
-        /// </summary>
-        /// <param name="sender">The event sender.</param>
-        /// <param name="e">The event args.</param>
-        ////private void ContainerMaterialized(object? sender, ItemContainerEventArgs e)
-        ////{
-        ////    var selectedItem = SelectedItem;
-
-        ////    if (selectedItem == null)
-        ////    {
-        ////        return;
-        ////    }
-
-        ////    foreach (var container in e.Containers)
-        ////    {
-        ////        if (container.Item == selectedItem)
-        ////        {
-        ////            ((TreeViewItem)container.ContainerControl).IsSelected = true;
-
-        ////            if (AutoScrollToSelectedItem)
-        ////            {
-        ////                Dispatcher.UIThread.Post(container.ContainerControl.BringIntoView);
-        ////            }
-
-        ////            break;
-        ////        }
-        ////    }
-        ////}
-
         /// <summary>
         /// Sets a container's 'selected' class or <see cref="ISelectable.IsSelected"/>.
         /// </summary>

From e7f3b23725354a8f4c43b317976888e922fd93af Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 11:13:22 +0100
Subject: [PATCH 036/157] Implement ILogicalScrollable on ItemsPresenter.

---
 .../Presenters/ItemsPresenter.cs              | 68 ++++++++++++++++++-
 1 file changed, 65 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 0091bbd48d..8297922664 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -1,8 +1,7 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Reflection;
+using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 
 namespace Avalonia.Controls.Presenters
@@ -10,7 +9,7 @@ namespace Avalonia.Controls.Presenters
     /// <summary>
     /// Presents items inside an <see cref="Avalonia.Controls.ItemsControl"/>.
     /// </summary>
-    public class ItemsPresenter : Control
+    public class ItemsPresenter : Control, ILogicalScrollable
     {
         /// <summary>
         /// Defines the <see cref="ItemsPanel"/> property.
@@ -19,6 +18,8 @@ namespace Avalonia.Controls.Presenters
             ItemsControl.ItemsPanelProperty.AddOwner<ItemsPresenter>();
 
         private PanelContainerGenerator? _generator;
+        private ILogicalScrollable? _logicalScrollable;
+        private EventHandler? _scrollInvalidated;
 
         static ItemsPresenter()
         {
@@ -27,6 +28,12 @@ namespace Avalonia.Controls.Presenters
                 KeyboardNavigationMode.Once);
         }
 
+        event EventHandler? ILogicalScrollable.ScrollInvalidated
+        {
+            add => _scrollInvalidated += value;
+            remove => _scrollInvalidated -= value;
+        }
+
         /// <summary>
         /// Gets or sets a template which creates the <see cref="Panel"/> used to display the items.
         /// </summary>
@@ -45,11 +52,52 @@ namespace Avalonia.Controls.Presenters
         /// Gets the owner <see cref="ItemsControl"/>.
         /// </summary>
         internal ItemsControl? ItemsControl { get; private set; }
+        
+        bool ILogicalScrollable.CanHorizontallyScroll 
+        {
+            get => _logicalScrollable?.CanHorizontallyScroll ?? false;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.CanHorizontallyScroll = value;
+            }
+        }
+
+        bool ILogicalScrollable.CanVerticallyScroll 
+        {
+            get => _logicalScrollable?.CanVerticallyScroll ?? false;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.CanVerticallyScroll = value;
+            }
+        }
+
+        Vector IScrollable.Offset 
+        {
+            get => _logicalScrollable?.Offset ?? default;
+            set
+            {
+                if (_logicalScrollable is not null)
+                    _logicalScrollable.Offset = value;
+            }
+        }
+
+        bool ILogicalScrollable.IsLogicalScrollEnabled => _logicalScrollable?.IsLogicalScrollEnabled ?? false;
+        Size ILogicalScrollable.ScrollSize => _logicalScrollable?.ScrollSize ?? default;
+        Size ILogicalScrollable.PageScrollSize => _logicalScrollable?.PageScrollSize ?? default;
+        Size IScrollable.Extent => _logicalScrollable?.Extent ?? default;
+        Size IScrollable.Viewport => _logicalScrollable?.Viewport ?? default;
 
         public override sealed void ApplyTemplate()
         {
             if (Panel is null && ItemsControl is not null)
             {
+                if (_logicalScrollable is not null)
+                {
+                    _logicalScrollable.ScrollInvalidated -= OnLogicalScrollInvalidated;
+                }
+
                 Panel = ItemsPanel.Build();
                 Panel.SetValue(TemplatedParentProperty, TemplatedParent);
                 LogicalChildren.Add(Panel);
@@ -59,9 +107,22 @@ namespace Avalonia.Controls.Presenters
                     v.Attach(ItemsControl);
                 else
                     CreateSimplePanelGenerator();
+
+                _logicalScrollable = Panel as ILogicalScrollable;
+
+                if (_logicalScrollable is not null)
+                {
+                    _logicalScrollable.ScrollInvalidated += OnLogicalScrollInvalidated;
+                }
             }
         }
 
+        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect) =>
+            _logicalScrollable?.BringIntoView(target, targetRect) ?? false;
+        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from) =>
+            _logicalScrollable?.GetControlInDirection(direction, from);
+        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e) => _scrollInvalidated?.Invoke(this, e);
+
         internal void ScrollIntoView(int index)
         {
             if (Panel is VirtualizingPanel v)
@@ -142,5 +203,6 @@ namespace Avalonia.Controls.Presenters
             return Panel?.Children.IndexOf(container) ?? -1;
         }
 
+        private void OnLogicalScrollInvalidated(object? sender, EventArgs e) => _scrollInvalidated?.Invoke(this, e);
     }
 }

From 08f90dcad6d1064030ebbc21182a2447f5bf8537 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Wed, 7 Dec 2022 12:39:44 +0100
Subject: [PATCH 037/157] Make logic a bit clearer.

---
 .../VirtualizingStackPanel.cs                 | 27 ++++++++++++-------
 1 file changed, 18 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index f211ec2edb..22526fa29c 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -428,7 +428,8 @@ namespace Avalonia.Controls
 
         private Control GetOrCreateElement(IList items, int index)
         {
-            var e = GetRealizedElement(index) ?? 
+            var e = GetRealizedElement(index) ??
+                GetItemIsOwnContainer(items, index) ??
                 GetRecycledElement(items, index) ??
                 CreateElement(items, index);
             InvalidateHack(e);
@@ -442,15 +443,12 @@ namespace Avalonia.Controls
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetItemIsOwnContainer(IList items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
-
-            var generator = ItemsControl!.ItemContainerGenerator;
-            var item = items[index];
-
-            if (item is Control controlItem)
+            if (items[index] is Control controlItem)
             {
+                var generator = ItemsControl!.ItemContainerGenerator;
+
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
@@ -459,12 +457,23 @@ namespace Avalonia.Controls
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
                     AddInternalChild(controlItem);
-                    generator.PrepareItemContainer(controlItem, item, index);
+                    generator.PrepareItemContainer(controlItem, controlItem, index);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
                     return controlItem;
                 }
             }
 
+            return null;
+        }
+
+        private Control? GetRecycledElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();

From f0c89a614e1c79bb0e68026f20f931c2fd314091 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 09:49:57 +0100
Subject: [PATCH 038/157] Reimplemented Carousel.

Only `VirtualizingCarouselPanel` currently implemented.
---
 .../ControlCatalog/Pages/CarouselPage.xaml    |   4 +-
 src/Avalonia.Controls/Carousel.cs             |  50 +-
 .../Presenters/CarouselPresenter.cs           | 276 -------
 .../VirtualizingCarouselPanel.cs              | 351 +++++++++
 .../Controls/Carousel.xaml                    |  20 +-
 .../Controls/Carousel.xaml                    |  23 +-
 .../CarouselTests.cs                          | 652 ++++++++--------
 .../Presenters/CarouselPresenterTests.cs      | 732 ------------------
 .../VirtualizingCarouselPanelTests.cs         | 271 +++++++
 .../UnitTestSynchronizationContext.cs         |   5 +-
 10 files changed, 993 insertions(+), 1391 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/CarouselPresenter.cs
 create mode 100644 src/Avalonia.Controls/VirtualizingCarouselPanel.cs
 delete mode 100644 tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
 create mode 100644 tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
 rename tests/{Avalonia.Base.UnitTests/Data => Avalonia.UnitTests}/UnitTestSynchronizationContext.cs (91%)

diff --git a/samples/ControlCatalog/Pages/CarouselPage.xaml b/samples/ControlCatalog/Pages/CarouselPage.xaml
index 1c2d768966..352fa32e30 100644
--- a/samples/ControlCatalog/Pages/CarouselPage.xaml
+++ b/samples/ControlCatalog/Pages/CarouselPage.xaml
@@ -12,7 +12,7 @@
       </Button>
       <Carousel Name="carousel" Grid.Column="1">
         <Carousel.PageTransition>
-          <PageSlide Duration="0.25" Orientation="Vertical" />
+          <PageSlide Duration="0.25" Orientation="Horizontal" />
         </Carousel.PageTransition>
         <Image Source="/Assets/delicate-arch-896885_640.jpg"/>
         <Image Source="/Assets/hirsch-899118_640.jpg"/>
@@ -35,7 +35,7 @@
 
     <StackPanel Orientation="Horizontal" Spacing="4">
       <TextBlock VerticalAlignment="Center">Orientation</TextBlock>
-      <ComboBox Name="orientation" SelectedIndex="1" VerticalAlignment="Center">
+      <ComboBox Name="orientation" SelectedIndex="0" VerticalAlignment="Center">
         <ComboBoxItem>Horizontal</ComboBoxItem>
         <ComboBoxItem>Vertical</ComboBoxItem>
       </ComboBox>
diff --git a/src/Avalonia.Controls/Carousel.cs b/src/Avalonia.Controls/Carousel.cs
index 572ec5a3d5..a9ffb2119a 100644
--- a/src/Avalonia.Controls/Carousel.cs
+++ b/src/Avalonia.Controls/Carousel.cs
@@ -2,7 +2,6 @@ using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Controls.Utils;
-using Avalonia.Input;
 
 namespace Avalonia.Controls
 {
@@ -11,12 +10,6 @@ namespace Avalonia.Controls
     /// </summary>
     public class Carousel : SelectingItemsControl
     {
-        /// <summary>
-        /// Defines the <see cref="IsVirtualized"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsVirtualizedProperty =
-            AvaloniaProperty.Register<Carousel, bool>(nameof(IsVirtualized), true);
-
         /// <summary>
         /// Defines the <see cref="PageTransition"/> property.
         /// </summary>
@@ -28,7 +21,9 @@ namespace Avalonia.Controls
         /// <see cref="Carousel"/>.
         /// </summary>
         private static readonly ITemplate<Panel> PanelTemplate =
-            new FuncTemplate<Panel>(() => new Panel());
+            new FuncTemplate<Panel>(() => new VirtualizingCarouselPanel());
+
+        private IScrollable? _scroller;
 
         /// <summary>
         /// Initializes static members of the <see cref="Carousel"/> class.
@@ -38,18 +33,6 @@ namespace Avalonia.Controls
             SelectionModeProperty.OverrideDefaultValue<Carousel>(SelectionMode.AlwaysSelected);
             ItemsPanelProperty.OverrideDefaultValue<Carousel>(PanelTemplate);
         }
-        
-        /// <summary>
-        /// Gets or sets a value indicating whether the items in the carousel are virtualized.
-        /// </summary>
-        /// <remarks>
-        /// When the carousel is virtualized, only the active page is held in memory.
-        /// </remarks>
-        public bool IsVirtualized
-        {
-            get { return GetValue(IsVirtualizedProperty); }
-            set { SetValue(IsVirtualizedProperty, value); }
-        }
 
         /// <summary>
         /// Gets or sets the transition to use when moving between pages.
@@ -81,5 +64,32 @@ namespace Avalonia.Controls
                 --SelectedIndex;
             }
         }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var result = base.ArrangeOverride(finalSize);
+
+            if (_scroller is not null)
+                _scroller.Offset = new(SelectedIndex, 0);
+
+            return result;
+        }
+
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+            _scroller = e.NameScope.Find<IScrollable>("PART_ScrollViewer");
+        }
+
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == SelectedIndexProperty && _scroller is not null)
+            {
+                var value = change.GetNewValue<int>();
+                _scroller.Offset = new(value, 0);
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
deleted file mode 100644
index d5b89a1bdc..0000000000
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ /dev/null
@@ -1,276 +0,0 @@
-using System.Collections.Specialized;
-using System.Linq;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Animation;
-using Avalonia.Controls.Primitives;
-using Avalonia.Controls.Utils;
-using Avalonia.Data;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Displays pages inside an <see cref="ItemsControl"/>.
-    /// </summary>
-    public class CarouselPresenter : ItemsPresenter
-    {
-        /// <summary>
-        /// Defines the <see cref="IsVirtualized"/> property.
-        /// </summary>
-        public static readonly StyledProperty<bool> IsVirtualizedProperty =
-            Carousel.IsVirtualizedProperty.AddOwner<CarouselPresenter>();
-
-        /// <summary>
-        /// Defines the <see cref="SelectedIndex"/> property.
-        /// </summary>
-        public static readonly DirectProperty<CarouselPresenter, int> SelectedIndexProperty =
-            SelectingItemsControl.SelectedIndexProperty.AddOwner<CarouselPresenter>(
-                o => o.SelectedIndex,
-                (o, v) => o.SelectedIndex = v);
-
-        /// <summary>
-        /// Defines the <see cref="PageTransition"/> property.
-        /// </summary>
-        public static readonly StyledProperty<IPageTransition?> PageTransitionProperty =
-            Carousel.PageTransitionProperty.AddOwner<CarouselPresenter>();
-
-        private int _selectedIndex = -1;
-        private Task? _currentTransition;
-        private int _queuedTransitionIndex = -1;
-
-        /// <summary>
-        /// Initializes static members of the <see cref="CarouselPresenter"/> class.
-        /// </summary>
-        static CarouselPresenter()
-        {
-            ////IsVirtualizedProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.IsVirtualizedChanged(e));
-            ////SelectedIndexProperty.Changed.AddClassHandler<CarouselPresenter>((x, e) => x.SelectedIndexChanged(e));
-        }
-
-        /// <summary>
-        /// Gets or sets a value indicating whether the items in the carousel are virtualized.
-        /// </summary>
-        /// <remarks>
-        /// When the carousel is virtualized, only the active page is held in memory.
-        /// </remarks>
-        public bool IsVirtualized
-        {
-            get { return GetValue(IsVirtualizedProperty); }
-            set { SetValue(IsVirtualizedProperty, value); }
-        }
-
-        /// <summary>
-        /// Gets or sets the index of the selected page.
-        /// </summary>
-        public int SelectedIndex
-        {
-            get
-            {
-                return _selectedIndex;
-            }
-
-            set
-            {
-                ////var old = SelectedIndex;
-                ////var effective = (value >= 0 && value < Items?.Cast<object>().Count()) ? value : -1;
-
-                ////if (old != effective)
-                ////{
-                ////    _selectedIndex = effective;
-                ////    RaisePropertyChanged(SelectedIndexProperty, old, effective, BindingPriority.LocalValue);
-                ////}
-            }
-        }
-
-        /// <summary>
-        /// Gets or sets a transition to use when switching pages.
-        /// </summary>
-        public IPageTransition? PageTransition
-        {
-            get { return GetValue(PageTransitionProperty); }
-            set { SetValue(PageTransitionProperty, value); }
-        }
-
-        /// <inheritdoc/>
-        ////protected override void ItemsChanged(NotifyCollectionChangedEventArgs e)
-        ////{
-        ////    if (!IsVirtualized)
-        ////    {
-        ////        base.ItemsChanged(e);
-
-        ////        if (Items == null || SelectedIndex >= Items.Count())
-        ////        {
-        ////            SelectedIndex = Items.Count() - 1;
-        ////        }
-
-        ////        foreach (var c in ItemContainerGenerator.Containers)
-        ////        {
-        ////            c.ContainerControl.IsVisible = c.Index == SelectedIndex;
-        ////        }
-        ////    }
-        ////    else if (SelectedIndex != -1 && Panel != null)
-        ////    {
-        ////        switch (e.Action)
-        ////        {
-        ////            case NotifyCollectionChangedAction.Add:
-        ////                if (e.NewStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Remove:
-        ////                if (e.OldStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Replace:
-        ////                if (e.OldStartingIndex > SelectedIndex ||
-        ////                    e.OldStartingIndex + e.OldItems!.Count - 1 < SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////            case NotifyCollectionChangedAction.Move:
-        ////                if (e.OldStartingIndex > SelectedIndex &&
-        ////                    e.NewStartingIndex > SelectedIndex)
-        ////                {
-        ////                    return;
-        ////                }
-        ////                break;
-        ////        }
-
-        ////        if (Items == null || SelectedIndex >= Items.Count())
-        ////        {
-        ////            SelectedIndex = Items.Count() - 1;
-        ////        }
-
-        ////        Panel.Children.Clear();
-        ////        ItemContainerGenerator.Clear();
-
-        ////        if (SelectedIndex != -1)
-        ////        {
-        ////            GetOrCreateContainer(SelectedIndex);
-        ////        }
-        ////    }
-        ////}
-
-        ////protected override void PanelCreated(Panel panel)
-        ////{
-        ////    ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        ////}
-
-        /////// <summary>
-        /////// Moves to the selected page, animating if a <see cref="PageTransition"/> is set.
-        /////// </summary>
-        /////// <param name="fromIndex">The index of the old page.</param>
-        /////// <param name="toIndex">The index of the new page.</param>
-        /////// <returns>A task tracking the animation.</returns>
-        ////private async Task MoveToPage(int fromIndex, int toIndex)
-        ////{
-        ////    if (fromIndex != toIndex)
-        ////    {
-        ////        var generator = ItemContainerGenerator;
-        ////        Control? from = null;
-        ////        Control? to = null;
-
-        ////        if (fromIndex != -1)
-        ////        {
-        ////            from = generator.ContainerFromIndex(fromIndex);
-        ////        }
-
-        ////        if (toIndex != -1)
-        ////        {
-        ////            to = GetOrCreateContainer(toIndex);
-        ////        }
-
-        ////        if (PageTransition != null && (from != null || to != null))
-        ////        {
-        ////            await PageTransition.Start((Visual?)from, (Visual?)to, fromIndex < toIndex, default);
-        ////        }
-        ////        else if (to != null)
-        ////        {
-        ////            to.IsVisible = true;
-        ////        }
-
-        ////        if (from != null)
-        ////        {
-        ////            if (IsVirtualized)
-        ////            {
-        ////                Panel!.Children.Remove(from);
-        ////                generator.Dematerialize(fromIndex, 1);
-        ////            }
-        ////            else
-        ////            {
-        ////                from.IsVisible = false;
-        ////            }
-        ////        }
-        ////    }
-        ////}
-
-        ////private Control? GetOrCreateContainer(int index)
-        ////{
-        ////    var container = ItemContainerGenerator.ContainerFromIndex(index);
-
-        ////    if (container == null && IsVirtualized)
-        ////    {
-        ////        var item = Items!.Cast<object>().ElementAt(index);
-        ////        var materialized = ItemContainerGenerator.Materialize(index, item);
-        ////        Panel!.Children.Add(materialized.ContainerControl);
-        ////        container = materialized.ContainerControl;
-        ////    }
-
-        ////    return container;
-        ////}
-
-        /////// <summary>
-        /////// Called when the <see cref="IsVirtualized"/> property changes.
-        /////// </summary>
-        /////// <param name="e">The event args.</param>
-        ////private void IsVirtualizedChanged(AvaloniaPropertyChangedEventArgs e)
-        ////{
-        ////    if (Panel != null)
-        ////    {
-        ////        ItemsChanged(new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
-        ////    }
-        ////}
-
-        /////// <summary>
-        /////// Called when the <see cref="SelectedIndex"/> property changes.
-        /////// </summary>
-        /////// <param name="e">The event args.</param>
-        ////private async void SelectedIndexChanged(AvaloniaPropertyChangedEventArgs e)
-        ////{
-        ////    if (Panel != null)
-        ////    {
-        ////        if (_currentTransition == null)
-        ////        {
-        ////            int fromIndex = (int)e.OldValue!;
-        ////            int toIndex = (int)e.NewValue!;
-
-        ////            for (;;)
-        ////            {
-        ////                _currentTransition = MoveToPage(fromIndex, toIndex);
-        ////                await _currentTransition;
-
-        ////                if (_queuedTransitionIndex != -1)
-        ////                {
-        ////                    fromIndex = toIndex;
-        ////                    toIndex = _queuedTransitionIndex;
-        ////                    _queuedTransitionIndex = -1;
-        ////                }
-        ////                else
-        ////                {
-        ////                    _currentTransition = null;
-        ////                    break;
-        ////                }
-        ////            }
-        ////        }
-        ////        else
-        ////        {
-        ////            _queuedTransitionIndex = (int)e.NewValue!;
-        ////        }
-        ////    }
-        ////}
-    }
-}
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
new file mode 100644
index 0000000000..7ea175fc18
--- /dev/null
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -0,0 +1,351 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.Specialized;
+using System.Diagnostics;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Animation;
+using Avalonia.Controls.Primitives;
+using Avalonia.Input;
+
+namespace Avalonia.Controls
+{
+    /// <summary>
+    /// A panel used by <see cref="Carousel"/> to display the current item.
+    /// </summary>
+    public class VirtualizingCarouselPanel : VirtualizingPanel, ILogicalScrollable
+    {
+        private static readonly AttachedProperty<bool> ItemIsOwnContainerProperty =
+            AvaloniaProperty.RegisterAttached<VirtualizingCarouselPanel, Control, bool>("ItemIsOwnContainer");
+
+        private Size _extent;
+        private Vector _offset;
+        private Size _viewport;
+        private Stack<Control>? _recyclePool;
+        private Control? _realized;
+        private int _realizedIndex = -1;
+        private Control? _transitionFrom;
+        private int _transitionFromIndex = -1;
+        private CancellationTokenSource? _transition;
+        private EventHandler? _scrollInvalidated;
+
+        bool ILogicalScrollable.CanHorizontallyScroll { get; set; }
+        bool ILogicalScrollable.CanVerticallyScroll { get; set; }
+        bool ILogicalScrollable.IsLogicalScrollEnabled => true;
+        Size ILogicalScrollable.ScrollSize => new(1, 1);
+        Size ILogicalScrollable.PageScrollSize => new(1, 1);
+        Size IScrollable.Extent => Extent;
+        Size IScrollable.Viewport => Viewport;
+
+        Vector IScrollable.Offset 
+        {
+            get => _offset;
+            set
+            {
+                if ((int)_offset.X != value.X)
+                    InvalidateMeasure();
+                _offset = value;
+            }
+        }
+
+        private Size Extent
+        {
+            get => _extent;
+            set
+            {
+                if (_extent != value)
+                {
+                    _extent = value;
+                    _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+                }
+            }
+        }
+
+        private Size Viewport
+        {
+            get => _viewport;
+            set
+            {
+                if (_viewport != value)
+                {
+                    _viewport = value;
+                    _scrollInvalidated?.Invoke(this, EventArgs.Empty);
+                }
+            }
+        }
+
+        event EventHandler? ILogicalScrollable.ScrollInvalidated
+        {
+            add => _scrollInvalidated += value;
+            remove => _scrollInvalidated -= value;
+        }
+
+        bool ILogicalScrollable.BringIntoView(Control target, Rect targetRect)
+        {
+            throw new NotImplementedException();
+        }
+
+        Control? ILogicalScrollable.GetControlInDirection(NavigationDirection direction, Control? from)
+        {
+            throw new NotImplementedException();
+        }
+
+        void ILogicalScrollable.RaiseScrollInvalidated(EventArgs e) => _scrollInvalidated?.Invoke(this, e);
+
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            var items = ItemsControl?.Items as IList ?? Array.Empty<object?>();
+            var index = (int)_offset.X;
+
+            if (index != _realizedIndex)
+            {
+                if (_realized is not null)
+                {
+                    var cancelTransition = _transition is not null;
+
+                    // Cancel any already running transition, and recycle the element we're transitioning from.
+                    if (cancelTransition)
+                    {
+                        _transition!.Cancel();
+                        _transition = null;
+                        if (_transitionFrom is not null)
+                            RecycleElement(_transitionFrom);
+                        _transitionFrom = null;
+                        _transitionFromIndex = -1;
+                    }
+
+                    if (cancelTransition || GetTransition() is null)
+                    {
+                        // If don't have a transition or we've just canceled a transition then recycle the element
+                        // we're moving from.
+                        RecycleElement(_realized);
+                    }
+                    else
+                    {
+                        // We have a transition to do: record the current element as the element we're transitioning
+                        // from and we'll start the transition in the arrange pass.
+                        _transitionFrom = _realized;
+                        _transitionFromIndex = _realizedIndex;
+                    }
+
+                    _realized = null;
+                    _realizedIndex = -1;
+                }
+                
+                // Get or create an element for the new item.
+                if (index >= 0 && index < items.Count)
+                {
+                    _realized = GetOrCreateElement(items, index);
+                    _realizedIndex = index;
+                }
+            }
+
+            if (_realized is null)
+            {
+                Extent = Viewport = new(0, 0);
+                _transitionFrom = null;
+                _transitionFromIndex = -1;
+                return default;
+            }
+
+            _realized.Measure(availableSize);
+            Extent = new(items.Count, 1);
+            Viewport = new(1, 1);
+
+            return _realized.DesiredSize;
+        }
+
+        protected override Size ArrangeOverride(Size finalSize)
+        {
+            var result = base.ArrangeOverride(finalSize);
+
+            if (_transition is null &&
+                _transitionFrom is not null &&
+                _realized is { } to &&
+                GetTransition() is { } transition)
+            {
+                _transition = new CancellationTokenSource();
+                transition.Start(_transitionFrom, to, _realizedIndex > _transitionFromIndex, _transition.Token)
+                    .ContinueWith(TransitionFinished, TaskScheduler.FromCurrentSynchronizationContext());
+            }
+
+            return result;
+        }
+
+        protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap) => null;
+
+        protected internal override Control? ContainerFromIndex(int index)
+        {
+            return index == _realizedIndex ? _realized : null;
+        }
+
+        protected internal override IEnumerable<Control>? GetRealizedContainers()
+        {
+            return _realized is not null ? new[] { _realized } : null;
+        }
+
+        protected internal override int IndexFromContainer(Control container)
+        {
+            return container == _realized ? _realizedIndex : -1;
+        }
+
+        protected internal override Control? ScrollIntoView(int index)
+        {
+            return null;
+        }
+
+        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        {
+            base.OnItemsChanged(items, e);
+
+            void Add(int index, int count)
+            {
+                if (index <= _realizedIndex)
+                    _realizedIndex += count;
+            }
+
+            void Remove(int index, int count)
+            {
+                var end = index + (count - 1);
+
+                if (_realized is not null && index <= _realizedIndex && end >= _realizedIndex)
+                {
+                    RecycleElement(_realized);
+                    _realized = null;
+                    _realizedIndex = -1;
+                }
+                else if (index < _realizedIndex)
+                {
+                    _realizedIndex -= count;
+                }
+            }
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Add:
+                    Add(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Remove:
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
+                    Remove(e.OldStartingIndex, e.OldItems!.Count);
+                    Add(e.NewStartingIndex, e.NewItems!.Count);
+                    break;
+                case NotifyCollectionChangedAction.Reset:
+                    if (_realized is not null)
+                    {
+                        RecycleElement(_realized);
+                        _realized = null;
+                        _realizedIndex = -1;
+                    }
+                    break;
+            }
+
+            InvalidateMeasure();
+        }
+
+        private Control GetOrCreateElement(IList items, int index)
+        {
+            return GetRealizedElement(index) ??
+                GetItemIsOwnContainer(items, index) ??
+                GetRecycledElement(items, index) ??
+                CreateElement(items, index);
+        }
+
+        private Control? GetRealizedElement(int index)
+        {
+            return _realizedIndex == index ? _realized : null;
+        }
+
+        private Control? GetItemIsOwnContainer(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            if (items[index] is Control controlItem)
+            {
+                var generator = ItemsControl!.ItemContainerGenerator;
+
+                if (controlItem.IsSet(ItemIsOwnContainerProperty))
+                {
+                    controlItem.IsVisible = true;
+                    return controlItem;
+                }
+                else if (generator.IsItemItsOwnContainer(controlItem))
+                {
+                    AddInternalChild(controlItem);
+                    generator.PrepareItemContainer(controlItem, controlItem, index);
+                    controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    return controlItem;
+                }
+            }
+
+            return null;
+        }
+
+        private Control? GetRecycledElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+
+            if (_recyclePool?.Count > 0)
+            {
+                var recycled = _recyclePool.Pop();
+                recycled.IsVisible = true;
+                generator.PrepareItemContainer(recycled, item, index);
+                return recycled;
+            }
+
+            return null;
+        }
+
+        private Control CreateElement(IList items, int index)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            var generator = ItemsControl!.ItemContainerGenerator;
+            var item = items[index];
+            var container = generator.CreateContainer();
+
+            AddInternalChild(container);
+            generator.PrepareItemContainer(container, item, index);
+
+            return container;
+        }
+
+        private void RecycleElement(Control element)
+        {
+            Debug.Assert(ItemsControl is not null);
+
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                element.IsVisible = false;
+            }
+            else
+            {
+                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+            }
+        }
+
+        private IPageTransition? GetTransition() => (ItemsControl as Carousel)?.PageTransition;
+
+        private void TransitionFinished(Task task)
+        {
+            if (task.IsCanceled)
+                return;
+
+            if (_transitionFrom is not null)
+                RecycleElement(_transitionFrom);
+            _transition = null;
+            _transitionFrom = null;
+            _transitionFromIndex = -1;
+        }
+    }
+}
diff --git a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
index 1dab50052d..91e331693e 100644
--- a/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Fluent/Controls/Carousel.xaml
@@ -3,16 +3,16 @@
   <ControlTheme x:Key="{x:Type Carousel}" TargetType="Carousel">
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}"
-                BorderBrush="{TemplateBinding BorderBrush}"
-                BorderThickness="{TemplateBinding BorderThickness}"
-                CornerRadius="{TemplateBinding CornerRadius}">
-          <CarouselPresenter IsVirtualized="{TemplateBinding IsVirtualized}"
-                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                             Margin="{TemplateBinding Padding}"
-                             SelectedIndex="{TemplateBinding SelectedIndex}"
-                             PageTransition="{TemplateBinding PageTransition}"/>
-        </Border>
+        <ScrollViewer Name="PART_ScrollViewer"
+                      Background="{TemplateBinding Background}"
+                      BorderBrush="{TemplateBinding BorderBrush}"
+                      BorderThickness="{TemplateBinding BorderThickness}"
+                      HorizontalScrollBarVisibility="Hidden"
+                      VerticalScrollBarVisibility="Hidden">
+          <ItemsPresenter Name="PART_ItemsPresenter"
+                          ItemsPanel="{TemplateBinding ItemsPanel}"
+                          Margin="{TemplateBinding Padding}"/>
+        </ScrollViewer>
       </ControlTemplate>
     </Setter>
   </ControlTheme>
diff --git a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
index 66a4a1866a..91e331693e 100644
--- a/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
+++ b/src/Avalonia.Themes.Simple/Controls/Carousel.xaml
@@ -1,19 +1,18 @@
 <ResourceDictionary xmlns="https://github.com/avaloniaui"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
-  <ControlTheme x:Key="{x:Type Carousel}"
-                TargetType="Carousel">
+  <ControlTheme x:Key="{x:Type Carousel}" TargetType="Carousel">
     <Setter Property="Template">
       <ControlTemplate>
-        <Border Background="{TemplateBinding Background}"
-                BorderBrush="{TemplateBinding BorderBrush}"
-                BorderThickness="{TemplateBinding BorderThickness}"
-                CornerRadius="{TemplateBinding CornerRadius}">
-          <CarouselPresenter Margin="{TemplateBinding Padding}"
-                             IsVirtualized="{TemplateBinding IsVirtualized}"
-                             ItemsPanel="{TemplateBinding ItemsPanel}"
-                             PageTransition="{TemplateBinding PageTransition}"
-                             SelectedIndex="{TemplateBinding SelectedIndex}" />
-        </Border>
+        <ScrollViewer Name="PART_ScrollViewer"
+                      Background="{TemplateBinding Background}"
+                      BorderBrush="{TemplateBinding BorderBrush}"
+                      BorderThickness="{TemplateBinding BorderThickness}"
+                      HorizontalScrollBarVisibility="Hidden"
+                      VerticalScrollBarVisibility="Hidden">
+          <ItemsPresenter Name="PART_ItemsPresenter"
+                          ItemsPanel="{TemplateBinding ItemsPanel}"
+                          Margin="{TemplateBinding Padding}"/>
+        </ScrollViewer>
       </ControlTemplate>
     </Setter>
   </ControlTheme>
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index ddf471e513..2b043e0e48 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -1,341 +1,321 @@
-////using System.Collections.ObjectModel;
-////using System.Linq;
-////using System.Reactive.Subjects;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Avalonia.Data;
-////using Avalonia.LogicalTree;
-////using Avalonia.UnitTests;
-////using Avalonia.VisualTree;
-////using Xunit;
-
-////namespace Avalonia.Controls.UnitTests
-////{
-////    public class CarouselTests
-////    {
-////        [Fact]
-////        public void First_Item_Should_Be_Selected_By_Default()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[]
-////                {
-////                    "Foo",
-////                    "Bar"
-////                }
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Equal("Foo", target.SelectedItem);
-////        }
-
-////        [Fact]
-////        public void LogicalChild_Should_Be_Selected_Item()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[]
-////                {
-////                    "Foo",
-////                    "Bar"
-////                }
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.GetLogicalChildren());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Foo", child.Text);
-////        }
-
-////        [Fact]
-////        public void Should_Remove_NonCurrent_Page_When_IsVirtualized_True()
-////        {
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = new[] { "foo", "bar" },
-////                IsVirtualized = true,
-////                SelectedIndex = 0,
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.ItemContainerGenerator.Containers);
-////            target.SelectedIndex = 1;
-////            Assert.Single(target.ItemContainerGenerator.Containers);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            var newItems = items.ToList();
-////            newItems.RemoveAt(0);
-
-////            target.Items = newItems;
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Bar", child.Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes_And_Virtualized()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = true,
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Single(target.GetLogicalChildren());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            var newItems = items.ToList();
-////            newItems.RemoveAt(0);
-
-////            target.Items = newItems;
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().Single());
-
-////            Assert.Equal("Bar", child.Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
-////        {
-////            var items = new ObservableCollection<string>();
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
+using System;
+using System.Collections.ObjectModel;
+using System.Linq;
+using System.Reactive.Subjects;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Data;
+using Avalonia.Layout;
+using Avalonia.LogicalTree;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Xunit;
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class CarouselTests
+    {
+        [Fact]
+        public void First_Item_Should_Be_Selected_By_Default()
+        {
+            using var app = Start();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = new[]
+                {
+                    "Foo",
+                    "Bar"
+                }
+            };
+
+            Prepare(target);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal("Foo", target.SelectedItem);
+        }
+
+        [Fact]
+        public void LogicalChild_Should_Be_Selected_Item()
+        {
+            using var app = Start();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = new[]
+                {
+                    "Foo",
+                    "Bar"
+                }
+            };
+
+            Prepare(target);
+
+            Assert.Single(target.GetRealizedContainers());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Foo", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_When_Items_Property_Changes()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Single(target.GetRealizedContainers());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Foo", child.Text);
+
+            var newItems = items.ToList();
+            newItems.RemoveAt(0);
+            Layout(target);
+
+            target.Items = newItems;
+            Layout(target);
+
+            child = GetContainerTextBlock(target.GetRealizedContainers().Single());
+
+            Assert.Equal("Bar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>();
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.Empty(target.GetRealizedContainers());
+
+            items.Add("Foo");
+            Layout(target);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Single(target.GetRealizedContainers());
+        }
+
+        [Fact]
+        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            Assert.Equal(1, target.GetRealizedContainers().Count());
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.Equal("Foo", child.Text);
+
+            target.Items = null;
+            Layout(target);
+
+            var numChildren = target.GetRealizedContainers().Count();
 
-////            Assert.Equal(-1, target.SelectedIndex);
-////            Assert.Empty(target.GetLogicalChildren());
+            Assert.Equal(-1, target.SelectedIndex);
+        }
 
-////            items.Add("Foo");
+        [Fact]
+        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+                SelectedIndex = 2
+            };
 
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Single(target.GetLogicalChildren());
-////        }
+            Prepare(target);
+
+            Assert.Equal("FooBar", target.SelectedItem);
 
-////        [Fact]
-////        public void Selected_Index_Changes_To_None_When_Items_Assigned_Null()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
+            var child = GetContainerTextBlock(target.GetRealizedContainers().LastOrDefault());
 
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            target.Items = null;
-
-////            var numChildren = target.GetLogicalChildren().Count();
-
-////            Assert.Equal(0, numChildren);
-////            Assert.Equal(-1, target.SelectedIndex);
-////        }
-
-////        [Fact]
-////        public void Selected_Index_Is_Maintained_Carousel_Created_With_Non_Zero_SelectedIndex()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false,
-////                SelectedIndex = 2
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal("FooBar", target.SelectedItem);
-
-////            var child = GetContainerTextBlock(target.GetVisualDescendants().LastOrDefault());
-
-////            Assert.IsType<TextBlock>(child);
-////            Assert.Equal("FooBar", ((TextBlock)child).Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            Assert.Equal(3, target.GetLogicalChildren().Count());
-
-////            var child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.Equal("Foo", child.Text);
-
-////            items.RemoveAt(0);
-
-////            child = GetContainerTextBlock(target.GetLogicalChildren().First());
-
-////            Assert.IsType<TextBlock>(child);
-////            Assert.Equal("Bar", ((TextBlock)child).Text);
-////        }
-
-////        [Fact]
-////        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
-////        {
-////            var items = new ObservableCollection<string>
-////            {
-////                "Foo",
-////                "Bar",
-////                "FooBar"
-////            };
-
-////            var target = new Carousel
-////            {
-////                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                Items = items,
-////                IsVirtualized = false
-////            };
-
-////            target.ApplyTemplate();
-////            ((Control)target.Presenter).ApplyTemplate();
-
-////            target.SelectedIndex = 1;
-
-////            items.RemoveAt(1);
-
-////            Assert.Equal(0, target.SelectedIndex);
-////            Assert.Equal("Foo", target.SelectedItem);
-////        }
-
-////        private Control CreateTemplate(Carousel control, INameScope scope)
-////        {
-////            return new CarouselPresenter
-////            {
-////                Name = "PART_ItemsPresenter",
-////                [~CarouselPresenter.IsVirtualizedProperty] = control[~Carousel.IsVirtualizedProperty],
-////                [~CarouselPresenter.ItemsPanelProperty] = control[~Carousel.ItemsPanelProperty],
-////                [~CarouselPresenter.SelectedIndexProperty] = control[~Carousel.SelectedIndexProperty],
-////                [~CarouselPresenter.PageTransitionProperty] = control[~Carousel.PageTransitionProperty],
-////            }.RegisterInNameScope(scope);
-////        }
-
-////        private static TextBlock GetContainerTextBlock(object control)
-////        {
-////            var contentPresenter = Assert.IsType<ContentPresenter>(control);
-////            contentPresenter.UpdateChild();
-////            return Assert.IsType<TextBlock>(contentPresenter.Child);
-////        }
-
-////        [Fact]
-////        public void SelectedItem_Validation()
-////        {
-////            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
-////            {
-////                var target = new Carousel
-////                {
-////                    Template = new FuncControlTemplate<Carousel>(CreateTemplate),
-////                    IsVirtualized = false
-////                };
-
-////                target.ApplyTemplate();
-////                ((Control)target.Presenter).ApplyTemplate();
-
-////                var exception = new System.InvalidCastException("failed validation");
-////                var textObservable =
-////                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
-////                        BindingErrorType.DataValidationError));
-////                target.Bind(ComboBox.SelectedItemProperty, textObservable);
-
-////                Assert.True(DataValidationErrors.GetHasErrors(target));
-////                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
-////            }
-////        }
-////    }
-////}
+            Assert.Equal("FooBar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_Next_First_Item_When_Item_Removed_From_Beggining_Of_List()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            var child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.Equal("Foo", child.Text);
+
+            items.RemoveAt(0);
+            Layout(target);
+
+            child = GetContainerTextBlock(target.GetRealizedContainers().First());
+
+            Assert.IsType<TextBlock>(child);
+            Assert.Equal("Bar", child.Text);
+        }
+
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_If_SelectedItem_Is_Removed_From_Middle()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string>
+            {
+                "Foo",
+                "Bar",
+                "FooBar"
+            };
+
+            var target = new Carousel
+            {
+                Template = CarouselTemplate(),
+                Items = items,
+            };
+
+            Prepare(target);
+
+            target.SelectedIndex = 1;
+
+            items.RemoveAt(1);
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Equal("Foo", target.SelectedItem);
+        }
+
+        [Fact]
+        public void SelectedItem_Validation()
+        {
+            using (UnitTestApplication.Start(TestServices.MockThreadingInterface))
+            {
+                var target = new Carousel
+                {
+                    Template = CarouselTemplate(),
+                };
+
+                Prepare(target);
+
+                var exception = new System.InvalidCastException("failed validation");
+                var textObservable =
+                    new BehaviorSubject<BindingNotification>(new BindingNotification(exception,
+                        BindingErrorType.DataValidationError));
+                target.Bind(ComboBox.SelectedItemProperty, textObservable);
+
+                Assert.True(DataValidationErrors.GetHasErrors(target));
+                Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
+            }
+        }
+
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
+
+        private static void Prepare(Carousel target)
+        {
+            var root = new TestRoot(target);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+        }
+
+        private static void Layout(Carousel target)
+        {
+            ((ILayoutRoot)target.GetVisualRoot()).LayoutManager.ExecuteLayoutPass();
+        }
+
+        private static IControlTemplate CarouselTemplate()
+        {
+            return new FuncControlTemplate((c, ns) =>
+                new ScrollViewer
+                {
+                    Name = "PART_ScrollViewer",
+                    Template = ScrollViewerTemplate(),
+                    HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    VerticalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    Content = new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                        [~ItemsPresenter.ItemsPanelProperty] = c[~ItemsControl.ItemsPanelProperty],
+                    }.RegisterInNameScope(ns)
+                }.RegisterInNameScope(ns));
+        }
+
+        private static FuncControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((parent, scope) =>
+                new Panel
+                {
+                    Children =
+                    {
+                        new ScrollContentPresenter
+                        {
+                            Name = "PART_ContentPresenter",
+                            [~ScrollContentPresenter.ContentProperty] = parent.GetObservable(ScrollViewer.ContentProperty).ToBinding(),
+                            [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
+                            [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
+                            [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
+                        }.RegisterInNameScope(scope),
+                    }
+                });
+        }
+
+        private static TextBlock GetContainerTextBlock(object control)
+        {
+            var contentPresenter = Assert.IsType<ContentPresenter>(control);
+            return Assert.IsType<TextBlock>(contentPresenter.Child);
+        }
+    }
+}
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
deleted file mode 100644
index f5094accb5..0000000000
--- a/tests/Avalonia.Controls.UnitTests/Presenters/CarouselPresenterTests.cs
+++ /dev/null
@@ -1,732 +0,0 @@
-////using System.Linq;
-////using Moq;
-////using Avalonia.Controls.Generators;
-////using Avalonia.Controls.Presenters;
-////using Avalonia.Controls.Templates;
-////using Xunit;
-////using System.Collections.ObjectModel;
-////using System.Collections;
-
-////namespace Avalonia.Controls.UnitTests.Presenters
-////{
-////    public class CarouselPresenterTests
-////    {
-////        [Fact]
-////        public void Should_Register_With_Host_When_TemplatedParent_Set()
-////        {
-////            var host = new Carousel();
-////            var target = new CarouselPresenter();
-
-////            Assert.Null(host.Presenter);
-
-////            target.SetValue(Control.TemplatedParentProperty, host);
-
-////            Assert.Same(target, host.Presenter);
-////        }
-
-////        [Fact]
-////        public void ApplyTemplate_Should_Create_Panel()
-////        {
-////            var target = new CarouselPresenter
-////            {
-////                ItemsPanel = new FuncTemplate<Panel>(() => new Panel()),
-////            };
-
-////            target.ApplyTemplate();
-
-////            Assert.IsType<Panel>(target.Panel);
-////        }
-
-////        [Fact]
-////        public void ItemContainerGenerator_Should_Be_Picked_Up_From_TemplatedControl()
-////        {
-////            var parent = new TestItemsControl();
-////            var target = new CarouselPresenter
-////            {
-////                [StyledElement.TemplatedParentProperty] = parent,
-////            };
-
-////            Assert.IsType<ItemContainerGenerator<TestItem>>(target.ItemContainerGenerator);
-////        }
-
-////        public class Virtualized
-////        {
-////            [Fact]
-////            public void Should_Initially_Materialize_Selected_Container()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Initially_Materialize_Nothing_If_No_Selected_Container()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Switching_To_Virtualized_Should_Reset_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                target.IsVirtualized = true;
-
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Changing_SelectedIndex_Should_Show_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertSingle(target);
-
-////                target.SelectedIndex = 1;
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Remove_NonCurrent_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = true,
-////                    SelectedIndex = 0,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertSingle(target);
-
-////                target.SelectedIndex = 1;
-////                AssertSingle(target);
-
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Inserting_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items.Insert(2, "after");
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(1);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Removing_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items.RemoveAt(2);
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(2);
-////                Assert.Equal(1, target.SelectedIndex);
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Last_Item()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Replacing_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items[1] = "replaced";
-////                AssertSingle(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Nothing_When_Replacing_Non_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                var child = AssertSingle(target);
-////                items[0] = "replaced";
-////                Assert.Same(child, AssertSingle(target));
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Moving_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Move(1, 0);
-////                AssertSingle(target);
-////            }
-
-////            private static Control AssertSingle(CarouselPresenter target)
-////            {
-////                var items = (IList)target.Items;
-////                var index = target.SelectedIndex;
-////                var content = items[index];
-////                var child = Assert.Single(target.Panel.Children);
-////                var presenter = Assert.IsType<ContentPresenter>(child);
-////                var container = Assert.Single(target.ItemContainerGenerator.Containers);
-////                var visible = Assert.Single(target.Panel.Children.Where(x => x.IsVisible));
-
-////                Assert.Same(child, container.ContainerControl);
-////                Assert.Same(child, visible);
-////                Assert.Equal(content, presenter.Content);
-////                Assert.Equal(content, container.Item);
-////                Assert.Equal(index, container.Index);
-
-////                return child;
-////            }
-////        }
-
-////        public class NonVirtualized
-////        {
-////            [Fact]
-////            public void Should_Initially_Materialize_All_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Initially_Show_Selected_Item()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Switching_To_Non_Virtualized_Should_Reset_Containers()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = true,
-////                };
-
-////                target.ApplyTemplate();
-////                target.IsVirtualized = false;
-
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Changing_SelectedIndex_Should_Show_Page()
-////            {
-////                var target = new CarouselPresenter
-////                {
-////                    Items = new[] { "foo", "bar" },
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                AssertAll(target);
-
-////                target.SelectedIndex = 1;
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Inserting_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Insert(1, "item1a");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Do_Handle_Inserting_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                items.Insert(2, "after");
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_At_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(1);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_Before_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Item_After_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-////                items.RemoveAt(2);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_SelectedItem_When_Its_Last()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 2,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(2);
-////                Assert.Equal(1, target.SelectedIndex);
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Removing_Last_Item()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 0,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.RemoveAt(0);
-////                Assert.Empty(target.Panel.Children);
-////                Assert.Empty(target.ItemContainerGenerator.Containers);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Replacing_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items[1] = "replaced";
-////                AssertAll(target);
-////            }
-
-////            [Fact]
-////            public void Should_Handle_Moving_SelectedItem()
-////            {
-////                var items = new ObservableCollection<string>
-////                {
-////                    "item0",
-////                    "item1",
-////                    "item2",
-////                };
-
-////                var target = new CarouselPresenter
-////                {
-////                    Items = items,
-////                    SelectedIndex = 1,
-////                    IsVirtualized = false,
-////                };
-
-////                target.ApplyTemplate();
-
-////                items.Move(1, 0);
-////                AssertAll(target);
-////            }
-
-////            private static void AssertAll(CarouselPresenter target)
-////            {
-////                var items = (IList)target.Items;
-
-////                Assert.Equal(items?.Count ?? 0, target.Panel.Children.Count);
-////                Assert.Equal(items?.Count ?? 0, target.ItemContainerGenerator.Containers.Count());
-
-////                for (var i = 0; i < items?.Count; ++i)
-////                {
-////                    var content = items[i];
-////                    var child = target.Panel.Children[i];
-////                    var presenter = Assert.IsType<ContentPresenter>(child);
-////                    var container = target.ItemContainerGenerator.ContainerFromIndex(i);
-
-////                    Assert.Same(child, container);
-////                    Assert.Equal(i == target.SelectedIndex, child.IsVisible);
-////                    Assert.Equal(content, presenter.Content);
-////                    Assert.Equal(i, target.ItemContainerGenerator.IndexFromContainer(container));
-////                }
-////            }
-////        }
-
-////        private class TestItem : ContentControl
-////        {
-////        }
-
-////        private class TestItemsControl : ItemsControl
-////        {
-////            protected override IItemContainerGenerator CreateItemContainerGenerator()
-////            {
-////                return new ItemContainerGenerator<TestItem>(this, TestItem.ContentProperty, null);
-////            }
-////        }
-////    }
-////}
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
new file mode 100644
index 0000000000..ea6b9367cf
--- /dev/null
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingCarouselPanelTests.cs
@@ -0,0 +1,271 @@
+using System;
+using System.Collections;
+using System.Collections.ObjectModel;
+using System.Threading;
+using System.Threading.Tasks;
+using Avalonia.Animation;
+using Avalonia.Controls.Presenters;
+using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
+using Avalonia.Layout;
+using Avalonia.UnitTests;
+using Avalonia.VisualTree;
+using Moq;
+using Xunit;
+
+#nullable enable
+
+namespace Avalonia.Controls.UnitTests
+{
+    public class VirtualizingCarouselPanelTests
+    {
+        [Fact]
+        public void Initial_Item_Is_Displayed()
+        {
+            using var app = Start();
+            var items = new[] { "foo", "bar" };
+            var (target, _) = CreateTarget(items);
+
+            Assert.Single(target.Children);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+            Assert.Equal("foo", container.Content);
+        }
+
+        [Fact]
+        public void Displays_Next_Item()
+        {
+            using var app = Start();
+            var items = new[] { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+
+            carousel.SelectedIndex = 1;
+            Layout(target);
+
+            Assert.Single(target.Children);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Inserted_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.Insert(0, "baz");
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("foo", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Removed_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.RemoveAt(0);
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Replaced_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items[0] = "baz";
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("baz", container.Content);
+        }
+
+        [Fact]
+        public void Handles_Moved_Item()
+        {
+            using var app = Start();
+            var items = new ObservableCollection<string> { "foo", "bar" };
+            var (target, carousel) = CreateTarget(items);
+            var container = Assert.IsType<ContentPresenter>(target.Children[0]);
+
+            items.Move(0, 1);
+            Layout(target);
+
+            Assert.Single(target.Children);
+            Assert.Same(container, target.Children[0]);
+            Assert.Equal("bar", container.Content);
+        }
+
+        public class Transitions
+        {
+            [Fact]
+            public void Initial_Item_Does_Not_Start_Transition()
+            {
+                using var app = Start();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, _) = CreateTarget(items, transition.Object);
+
+                transition.Verify(x => x.Start(
+                        It.IsAny<Visual>(),
+                        It.IsAny<Visual>(),
+                        It.IsAny<bool>(),
+                        It.IsAny<CancellationToken>()),
+                    Times.Never);
+            }
+
+            [Fact]
+            public void Changing_SelectedIndex_Starts_Transition()
+            {
+                using var app = Start();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                transition.Verify(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()),
+                    Times.Once);
+            }
+
+            [Fact]
+            public void TransitionFrom_Control_Is_Recycled_When_Transition_Completes()
+            {
+                using var app = Start();
+                using var sync = UnitTestSynchronizationContext.Begin();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+                var transitionTask = new TaskCompletionSource();
+
+                transition.Setup(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()))
+                    .Returns(() => transitionTask.Task);
+                
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                Assert.Equal(items, target.Children);
+                Assert.All(items, x => Assert.True(x.IsVisible));
+                
+                transitionTask.SetResult();
+                sync.ExecutePostedCallbacks();
+
+                Assert.Equal(items, target.Children);
+                Assert.False(items[0].IsVisible);
+                Assert.True(items[1].IsVisible);
+            }
+
+            [Fact]
+            public void Existing_Transition_Is_Canceled_If_Interrupted()
+            {
+                using var app = Start();
+                using var sync = UnitTestSynchronizationContext.Begin();
+                var items = new Control[] { new Button(), new Canvas() };
+                var transition = new Mock<IPageTransition>();
+                var (target, carousel) = CreateTarget(items, transition.Object);
+                var transitionTask = new TaskCompletionSource();
+                CancellationToken? cancelationToken = null;
+
+                transition.Setup(x => x.Start(
+                        items[0],
+                        items[1],
+                        true,
+                        It.IsAny<CancellationToken>()))
+                    .Callback<Visual, Visual, bool, CancellationToken>((_, _, _, c) => cancelationToken = c)
+                    .Returns(() => transitionTask.Task);
+
+                carousel.SelectedIndex = 1;
+                Layout(target);
+
+                Assert.NotNull(cancelationToken);
+                Assert.False(cancelationToken!.Value.IsCancellationRequested);
+
+                carousel.SelectedIndex = 0;
+                Layout(target);
+
+                Assert.True(cancelationToken!.Value.IsCancellationRequested);
+            }
+        }
+
+        private static IDisposable Start() => UnitTestApplication.Start(TestServices.MockPlatformRenderInterface);
+
+        private static (VirtualizingCarouselPanel, Carousel) CreateTarget(
+            IEnumerable items,
+            IPageTransition? transition = null)
+        {
+            var carousel = new Carousel
+            {
+                Items = items,
+                Template = CarouselTemplate(),
+                PageTransition = transition,
+            };
+
+            var root = new TestRoot(carousel);
+            root.LayoutManager.ExecuteInitialLayoutPass();
+            return ((VirtualizingCarouselPanel)carousel.Presenter!.Panel!, carousel);
+        }
+
+        private static IControlTemplate CarouselTemplate()
+        {
+            return new FuncControlTemplate((c, ns) =>
+                new ScrollViewer
+                {
+                    Name = "PART_ScrollViewer",
+                    Template = ScrollViewerTemplate(),
+                    HorizontalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    VerticalScrollBarVisibility = ScrollBarVisibility.Hidden,
+                    Content = new ItemsPresenter
+                    {
+                        Name = "PART_ItemsPresenter",
+                        [~ItemsPresenter.ItemsPanelProperty] = c[~ItemsControl.ItemsPanelProperty],
+                    }.RegisterInNameScope(ns)
+                }.RegisterInNameScope(ns));
+        }
+
+        private static FuncControlTemplate ScrollViewerTemplate()
+        {
+            return new FuncControlTemplate<ScrollViewer>((parent, scope) =>
+                new Panel
+                {
+                    Children =
+                    {
+                        new ScrollContentPresenter
+                        {
+                            Name = "PART_ContentPresenter",
+                            [~ScrollContentPresenter.ContentProperty] = parent.GetObservable(ScrollViewer.ContentProperty).ToBinding(),
+                            [~~ScrollContentPresenter.ExtentProperty] = parent[~~ScrollViewer.ExtentProperty],
+                            [~~ScrollContentPresenter.OffsetProperty] = parent[~~ScrollViewer.OffsetProperty],
+                            [~~ScrollContentPresenter.ViewportProperty] = parent[~~ScrollViewer.ViewportProperty],
+                            [~ScrollContentPresenter.CanHorizontallyScrollProperty] = parent[~ScrollViewer.CanHorizontallyScrollProperty],
+                            [~ScrollContentPresenter.CanVerticallyScrollProperty] = parent[~ScrollViewer.CanVerticallyScrollProperty],
+                        }.RegisterInNameScope(scope),
+                    }
+                });
+        }
+
+        private static void Layout(Control c) => ((ILayoutRoot)c.GetVisualRoot()!).LayoutManager.ExecuteLayoutPass();
+    }
+}
diff --git a/tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs b/tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
similarity index 91%
rename from tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs
rename to tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
index 71eed38a4c..23cea7ad4f 100644
--- a/tests/Avalonia.Base.UnitTests/Data/UnitTestSynchronizationContext.cs
+++ b/tests/Avalonia.UnitTests/UnitTestSynchronizationContext.cs
@@ -1,11 +1,10 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Threading;
 
-namespace Avalonia.Base.UnitTests.Data
+namespace Avalonia.UnitTests
 {
-    internal sealed class UnitTestSynchronizationContext : SynchronizationContext
+    public sealed class UnitTestSynchronizationContext : SynchronizationContext
     {
         readonly List<Tuple<SendOrPostCallback, object>> _postedCallbacks =
             new List<Tuple<SendOrPostCallback, object>>();

From c54e466db127478127b98983c8bc4037a77e6670 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 09:50:46 +0100
Subject: [PATCH 039/157] Remove `FillMode` on transitions.

Now that containers are being recycled, the state of the control following the animation needs to be the same as before the animation.
---
 src/Avalonia.Base/Animation/PageSlide.cs                      | 2 --
 src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs | 2 --
 2 files changed, 4 deletions(-)

diff --git a/src/Avalonia.Base/Animation/PageSlide.cs b/src/Avalonia.Base/Animation/PageSlide.cs
index 609441ae8c..f388de5794 100644
--- a/src/Avalonia.Base/Animation/PageSlide.cs
+++ b/src/Avalonia.Base/Animation/PageSlide.cs
@@ -79,7 +79,6 @@ namespace Avalonia.Animation
                 var animation = new Animation
                 {
                     Easing = SlideOutEasing,
-                    FillMode = FillMode.Forward,
                     Children =
                     {
                         new KeyFrame
@@ -110,7 +109,6 @@ namespace Avalonia.Animation
                 to.IsVisible = true;
                 var animation = new Animation
                 {
-                    FillMode = FillMode.Forward,
                     Easing = SlideInEasing,
                     Children =
                     {
diff --git a/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs b/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
index 239f3aea08..b4a1f02f09 100644
--- a/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
+++ b/src/Avalonia.Base/Animation/Transitions/Rotate3DTransition.cs
@@ -71,7 +71,6 @@ public class Rotate3DTransition: PageSlide
             {
                 Easing = SlideOutEasing,
                 Duration = Duration,
-                FillMode = FillMode.Forward,
                 Children =
                 {
                     CreateKeyFrame(0d, 0d, 2),
@@ -90,7 +89,6 @@ public class Rotate3DTransition: PageSlide
             {
                 Easing = SlideInEasing,
                 Duration = Duration,
-                FillMode = FillMode.Forward,
                 Children =
                 {
                     CreateKeyFrame(0d, 90d * (forward ? 1 : -1), 1),

From 06de4bb8ab9e7862befba4cb053def32d30e4332 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 10:10:30 +0100
Subject: [PATCH 040/157] Update comment.

---
 src/Avalonia.Controls/ItemsControl.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b512d3583c..3d70c4975c 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -346,7 +346,8 @@ namespace Avalonia.Controls
         /// <param name="container">The container element.</param>
         protected internal virtual void ClearContainerForItemOverride(Control container)
         {
-            // TODO: Remove HeaderedItemsControl.Items binding.
+            // Feels like we should be clearing the HeaderedItemsControl.Items binding here, but looking at
+            // the WPF source it seems that this isn't done there.
         }
 
         /// <summary>

From 627d9c5d058206d2a11d4fb1aad3eed9b8fb34e6 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 11:11:19 +0100
Subject: [PATCH 041/157] Make VirtualizationDemo compile again.

---
 samples/VirtualizationDemo/MainWindow.xaml             |  3 ---
 .../ViewModels/MainWindowViewModel.cs                  | 10 ----------
 2 files changed, 13 deletions(-)

diff --git a/samples/VirtualizationDemo/MainWindow.xaml b/samples/VirtualizationDemo/MainWindow.xaml
index 4e8a5c386b..7748ebcc03 100644
--- a/samples/VirtualizationDemo/MainWindow.xaml
+++ b/samples/VirtualizationDemo/MainWindow.xaml
@@ -11,8 +11,6 @@
                     Margin="16 0 0 0" 
                     MinWidth="150"
                     Spacing="4">
-            <ComboBox Items="{Binding VirtualizationModes}"
-                      SelectedItem="{Binding VirtualizationMode}"/>
             <ComboBox Items="{Binding Orientations}"
                       SelectedItem="{Binding Orientation}"/>
             <TextBox Watermark="Item Count"
@@ -49,7 +47,6 @@
                  Items="{Binding Items}" 
                  Selection="{Binding Selection}"
                  SelectionMode="Multiple"
-                 VirtualizationMode="{Binding VirtualizationMode}"
                  ScrollViewer.HorizontalScrollBarVisibility="{Binding HorizontalScrollBarVisibility, Mode=TwoWay}"
                  ScrollViewer.VerticalScrollBarVisibility="{Binding VerticalScrollBarVisibility, Mode=TwoWay}">
             <ListBox.ItemsPanel>
diff --git a/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs b/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
index 514df691ae..96dbbc1a83 100644
--- a/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
+++ b/samples/VirtualizationDemo/ViewModels/MainWindowViewModel.cs
@@ -21,7 +21,6 @@ namespace VirtualizationDemo.ViewModels
         private ScrollBarVisibility _horizontalScrollBarVisibility = ScrollBarVisibility.Auto;
         private ScrollBarVisibility _verticalScrollBarVisibility = ScrollBarVisibility.Auto;
         private Orientation _orientation = Orientation.Vertical;
-        private ItemVirtualizationMode _virtualizationMode = ItemVirtualizationMode.Simple;
 
         public MainWindowViewModel()
         {
@@ -81,15 +80,6 @@ namespace VirtualizationDemo.ViewModels
         public IEnumerable<ScrollBarVisibility> ScrollBarVisibilities =>
             Enum.GetValues(typeof(ScrollBarVisibility)).Cast<ScrollBarVisibility>();
 
-        public ItemVirtualizationMode VirtualizationMode
-        {
-            get { return _virtualizationMode; }
-            set { this.RaiseAndSetIfChanged(ref _virtualizationMode, value); }
-        }
-
-        public IEnumerable<ItemVirtualizationMode> VirtualizationModes => 
-            Enum.GetValues(typeof(ItemVirtualizationMode)).Cast<ItemVirtualizationMode>();
-
         public MiniCommand AddItemCommand { get; private set; }
         public MiniCommand RecreateCommand { get; private set; }
         public MiniCommand RemoveItemCommand { get; private set; }

From 3195df0910a7c1b44a770624b5eb5e461485f205 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 13:55:21 +0100
Subject: [PATCH 042/157] Use ItemsSourceView in ItemsControl.

Fixes #54.
---
 src/Avalonia.Controls/Carousel.cs             |   2 +-
 src/Avalonia.Controls/ItemsControl.cs         | 221 +++++-----------
 src/Avalonia.Controls/ItemsSourceView.cs      | 240 ++++++++++--------
 src/Avalonia.Controls/MenuItem.cs             |   2 +-
 .../Presenters/PanelContainerGenerator.cs     |  11 +-
 .../Primitives/SelectingItemsControl.cs       |   2 +-
 .../Repeater/ItemsRepeater.cs                 |   1 -
 .../Selection/SelectionNodeBase.cs            |   6 +-
 src/Avalonia.Controls/TreeView.cs             |   9 +-
 src/Avalonia.Controls/TreeViewItem.cs         |   4 +-
 .../VirtualizingCarouselPanel.cs              |  12 +-
 src/Avalonia.Controls/VirtualizingPanel.cs    |  22 +-
 .../VirtualizingStackPanel.cs                 |  25 +-
 13 files changed, 244 insertions(+), 313 deletions(-)

diff --git a/src/Avalonia.Controls/Carousel.cs b/src/Avalonia.Controls/Carousel.cs
index a9ffb2119a..84601e8690 100644
--- a/src/Avalonia.Controls/Carousel.cs
+++ b/src/Avalonia.Controls/Carousel.cs
@@ -48,7 +48,7 @@ namespace Avalonia.Controls
         /// </summary>
         public void Next()
         {
-            if (SelectedIndex < Items.Count() - 1)
+            if (SelectedIndex < ItemCount - 1)
             {
                 ++SelectedIndex;
             }
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 3d70c4975c..b797ae8295 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -2,7 +2,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
-using System.Linq;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Automation.Peers;
 using Avalonia.Collections;
 using Avalonia.Controls.Generators;
@@ -10,7 +10,6 @@ using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
-using Avalonia.Controls.Utils;
 using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.LogicalTree;
@@ -24,7 +23,7 @@ namespace Avalonia.Controls
     /// Displays a collection of items.
     /// </summary>
     [PseudoClasses(":empty", ":singleitem")]
-    public class ItemsControl : TemplatedControl, IItemsPresenterHost, ICollectionChangedListener, IChildIndexProvider
+    public class ItemsControl : TemplatedControl, IItemsPresenterHost, IChildIndexProvider
     {
         /// <summary>
         /// The default value for the <see cref="ItemsPanel"/> property.
@@ -62,6 +61,11 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IDataTemplate?> ItemTemplateProperty =
             AvaloniaProperty.Register<ItemsControl, IDataTemplate?>(nameof(ItemTemplate));
 
+        /// <summary>
+        /// Defines the <see cref="ItemsView"/> property.
+        /// </summary>
+        public static readonly DirectProperty<ItemsControl, ItemsSourceView> ItemsViewProperty =
+            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(Items), o => o.ItemsView);
 
         /// <summary>
         /// Defines the <see cref="DisplayMemberBinding" /> property
@@ -80,27 +84,21 @@ namespace Avalonia.Controls
         }
         
         private IEnumerable? _items = new AvaloniaList<object>();
+        private ItemsSourceView _itemsView;
         private int _itemCount;
         private ItemContainerGenerator? _itemContainerGenerator;
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
         private Tuple<int, Control>? _containerBeingPrepared;
 
-        /// <summary>
-        /// Initializes static members of the <see cref="ItemsControl"/> class.
-        /// </summary>
-        static ItemsControl()
-        {
-            ItemsProperty.Changed.AddClassHandler<ItemsControl>((x, e) => x.ItemsChanged(e));
-        }
-
         /// <summary>
         /// Initializes a new instance of the <see cref="ItemsControl"/> class.
         /// </summary>
         public ItemsControl()
         {
+            _itemsView = new(_items);
+            _itemsView.PostCollectionChanged += ItemsCollectionChanged;
             UpdatePseudoClasses(0);
-            SubscribeToItems(_items);
         }
 
         /// <summary>
@@ -164,6 +162,33 @@ namespace Avalonia.Controls
         /// </summary>
         public ItemsPresenter? Presenter { get; private set; }
 
+        /// <summary>
+        /// Gets a standardized view over <see cref="Items"/>.
+        /// </summary>
+        /// <remarks>
+        /// The <see cref="Items"/> property may be an enumerable which does not implement
+        /// <see cref="IList"/> or may be null. This view can be used to provide a standardized
+        /// view of the current items regardless of the type of the concrete collection, and
+        /// without having to deal with null values.
+        /// </remarks>
+        public ItemsSourceView ItemsView 
+        {
+            get => _itemsView;
+            private set
+            {
+                if (ReferenceEquals(_itemsView, value))
+                    return;
+
+                var oldValue = _itemsView;
+                RemoveControlItemsFromLogicalChildren(_itemsView);
+                _itemsView.PostCollectionChanged -= ItemsCollectionChanged;
+                _itemsView = value;
+                _itemsView.PostCollectionChanged += ItemsCollectionChanged;
+                AddControlItemsToLogicalChildren(_itemsView);
+                RaisePropertyChanged(ItemsViewProperty, oldValue, _itemsView);
+            }
+        }
+
         private protected bool WrapFocus { get; set; }
 
         event EventHandler<ChildIndexChangedEventArgs>? IChildIndexProvider.ChildIndexChanged
@@ -192,7 +217,7 @@ namespace Avalonia.Controls
         /// </returns>
         public Control? ContainerFromItem(object item)
         {
-            var index = Items?.IndexOf(item) ?? -1;
+            var index = ItemsView.IndexOf(item);
             return index >= 0 ? ContainerFromIndex(index) : null;
         }
 
@@ -216,7 +241,7 @@ namespace Avalonia.Controls
         public object? ItemFromContainer(Control container)
         {
             var index = IndexFromContainer(container);
-            return index >= 0 && index < ItemCount ? Items!.ElementAt(index) : null;
+            return index >= 0 && index < ItemsView.Count ? ItemsView[index] : null;
         }
 
         /// <summary>
@@ -231,37 +256,6 @@ namespace Avalonia.Controls
             _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
         }
 
-        void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-        }
-
-        void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-        }
-
-        void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
-        {
-            ItemsCollectionChanged(sender, e);
-        }
-
-        /// <summary>
-        /// Gets the item at the specified index in a collection.
-        /// </summary>
-        /// <param name="items">The collection.</param>
-        /// <param name="index">The index.</param>
-        /// <returns>The item at the given index or null if the index is out of bounds.</returns>
-        protected static object? ElementAt(IEnumerable? items, int index)
-        {
-            if (index != -1 && index < items.Count())
-            {
-                return items!.ElementAt(index) ?? null;
-            }
-            else
-            {
-                return null;
-            }
-        }
-
         /// <summary>
         /// Creates or a container that can be used to display an item.
         /// </summary>
@@ -350,41 +344,6 @@ namespace Avalonia.Controls
             // the WPF source it seems that this isn't done there.
         }
 
-        /// <summary>
-        /// Gets the index of an item in a collection.
-        /// </summary>
-        /// <param name="items">The collection.</param>
-        /// <param name="item">The item.</param>
-        /// <returns>The index of the item or -1 if the item was not found.</returns>
-        protected static int IndexOf(IEnumerable? items, object item)
-        {
-            if (items != null && item != null)
-            {
-                var list = items as IList;
-
-                if (list != null)
-                {
-                    return list.IndexOf(item);
-                }
-                else
-                {
-                    int index = 0;
-
-                    foreach (var i in items)
-                    {
-                        if (Equals(i, item))
-                        {
-                            return index;
-                        }
-
-                        ++index;
-                    }
-                }
-            }
-
-            return -1;
-        }
-
         /// <summary>
         /// Determines whether the specified item is (or is eligible to be) its own container.
         /// </summary>
@@ -445,7 +404,12 @@ namespace Avalonia.Controls
         {
             base.OnPropertyChanged(change);
 
-            if (change.Property == ItemCountProperty)
+            if (change.Property == ItemsProperty)
+            {
+                ItemsView = ItemsSourceView.GetOrCreate(change.GetNewValue<IEnumerable?>());
+                ItemCount = ItemsView.Count;
+            }
+            else if (change.Property == ItemCountProperty)
             {
                 UpdatePseudoClasses(change.GetNewValue<int>());
             }
@@ -468,26 +432,6 @@ namespace Avalonia.Controls
             }
         }
 
-        /// <summary>
-        /// Called when the <see cref="Items"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        protected virtual void ItemsChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            var oldValue = e.OldValue as IEnumerable;
-            var newValue = e.NewValue as IEnumerable;
-
-            if (oldValue is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.RemoveListener(incc, this);
-            }
-
-            UpdateItemCount();
-            RemoveControlItemsFromLogicalChildren(oldValue);
-            AddControlItemsToLogicalChildren(newValue);
-            SubscribeToItems(newValue);
-        }
-
         /// <summary>
         /// Refreshes the containers displayed by the control.
         /// </summary>
@@ -502,9 +446,9 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="sender">The event sender.</param>
         /// <param name="e">The event args.</param>
-        protected virtual void ItemsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        protected virtual void ItemsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            UpdateItemCount();
+            ItemCount = _itemsView.Count;
 
             switch (e.Action)
             {
@@ -576,22 +520,22 @@ namespace Avalonia.Controls
         /// <param name="items">The items.</param>
         private void AddControlItemsToLogicalChildren(IEnumerable? items)
         {
-            var toAdd = new List<ILogical>();
+            if (items is null)
+                return;
 
-            if (items != null)
+            List<ILogical>? toAdd = null;
+
+            foreach (var i in items)
             {
-                foreach (var i in items)
+                if (i is Control control && !LogicalChildren.Contains(control))
                 {
-                    var control = i as Control;
-
-                    if (control != null && !LogicalChildren.Contains(control))
-                    {
-                        toAdd.Add(control);
-                    }
+                    toAdd ??= new();
+                    toAdd.Add(control);
                 }
             }
 
-            LogicalChildren.AddRange(toAdd);
+            if (toAdd is not null)
+                LogicalChildren.AddRange(toAdd);
         }
 
         /// <summary>
@@ -600,34 +544,22 @@ namespace Avalonia.Controls
         /// <param name="items">The items.</param>
         private void RemoveControlItemsFromLogicalChildren(IEnumerable? items)
         {
-            var toRemove = new List<ILogical>();
+            if (items is null)
+                return;
 
-            if (items != null)
+            List<ILogical>? toRemove = null;
+
+            foreach (var i in items)
             {
-                foreach (var i in items)
+                if (i is Control control)
                 {
-                    var control = i as Control;
-
-                    if (control != null)
-                    {
-                        toRemove.Add(control);
-                    }
+                    toRemove ??= new();
+                    toRemove.Add(control);
                 }
             }
 
-            LogicalChildren.RemoveAll(toRemove);
-        }
-
-        /// <summary>
-        /// Subscribes to an <see cref="Items"/> collection.
-        /// </summary>
-        /// <param name="items">The items collection.</param>
-        private void SubscribeToItems(IEnumerable? items)
-        {
-            if (items is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.AddListener(incc, this);
-            }
+            if (toRemove is not null)
+                LogicalChildren.RemoveAll(toRemove);
         }
 
         private IDataTemplate? GetEffectiveItemTemplate()
@@ -647,22 +579,6 @@ namespace Avalonia.Controls
             return _displayMemberItemTemplate;
         }
 
-        private void UpdateItemCount()
-        {
-            if (Items == null)
-            {
-                ItemCount = 0;
-            }
-            else if (Items is IList list)
-            {
-                ItemCount = list.Count;
-            }
-            else
-            {
-                ItemCount = Items.Count();
-            }
-        }
-
         private void UpdatePseudoClasses(int itemCount)
         {
             PseudoClasses.Set(":empty", itemCount == 0);
@@ -728,7 +644,8 @@ namespace Avalonia.Controls
 
         bool IChildIndexProvider.TryGetTotalCount(out int count)
         {
-            return Items.TryGetCountFast(out count);
+            count = ItemsView.Count;
+            return true;
         }
     }
 }
diff --git a/src/Avalonia.Controls/ItemsSourceView.cs b/src/Avalonia.Controls/ItemsSourceView.cs
index 945035ab5e..27fa7cbe48 100644
--- a/src/Avalonia.Controls/ItemsSourceView.cs
+++ b/src/Avalonia.Controls/ItemsSourceView.cs
@@ -13,24 +13,22 @@ using Avalonia.Controls.Utils;
 namespace Avalonia.Controls
 {
     /// <summary>
-    /// Represents a standardized view of the supported interactions between a given ItemsSource
-    /// object and an <see cref="ItemsRepeater"/> control.
+    /// Represents a standardized view of the supported interactions between an items collection
+    /// and an items control.
     /// </summary>
-    /// <remarks>
-    /// Components written to work with ItemsRepeater should consume the
-    /// <see cref="ItemsRepeater.Items"/> via ItemsSourceView since this provides a normalized
-    /// view of the Items. That way, each component does not need to know if the source is an
-    /// IEnumerable, an IList, or something else.
-    /// </remarks>
-    public class ItemsSourceView : INotifyCollectionChanged, IDisposable
+    public class ItemsSourceView : IReadOnlyList<object?>,
+        INotifyCollectionChanged,
+        ICollectionChangedListener
     {
         /// <summary>
         ///  Gets an empty <see cref="ItemsSourceView"/>
         /// </summary>
         public static ItemsSourceView Empty { get; } = new ItemsSourceView(Array.Empty<object>());
 
-        private IList? _inner;
+        private readonly IList _inner;
         private NotifyCollectionChangedEventHandler? _collectionChanged;
+        private NotifyCollectionChangedEventHandler? _postCollectionChanged;
+        private bool _listening;
 
         /// <summary>
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
@@ -38,15 +36,15 @@ namespace Avalonia.Controls
         /// <param name="source">The data source.</param>
         public ItemsSourceView(IEnumerable source)
         {
-            source = source ?? throw new ArgumentNullException(nameof(source));
             _inner = source switch
             {
-                ItemsSourceView _ => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)),
+                ItemsSourceView => throw new ArgumentException("Cannot wrap an existing ItemsSourceView.", nameof(source)),
                 IList list => list,
-                INotifyCollectionChanged _ => throw new ArgumentException(
-                    "Collection implements INotifyCollectionChanged by not IList.",
+                INotifyCollectionChanged => throw new ArgumentException(
+                    "Collection implements INotifyCollectionChanged but not IList.",
                     nameof(source)),
                 IEnumerable<object> iObj => new List<object>(iObj),
+                null => throw new ArgumentNullException(nameof(source)),
                 _ => new List<object>(source.Cast<object>())
             };
         }
@@ -56,26 +54,10 @@ namespace Avalonia.Controls
         /// </summary>
         public int Count => Inner.Count;
 
-        /// <summary>
-        /// Gets a value that indicates whether the items source can provide a unique key for each item.
-        /// </summary>
-        /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
-        /// </remarks>
-        public bool HasKeyIndexMapping => false;
-
         /// <summary>
         /// Gets the inner collection.
         /// </summary>
-        public IList Inner
-        {
-            get
-            {
-                if (_inner is null)
-                    ThrowDisposed();
-                return _inner!;
-            }
-        }
+        public IList Inner => _inner;
 
         /// <summary>
         /// Retrieves the item at the specified index.
@@ -84,6 +66,14 @@ namespace Avalonia.Controls
         /// <returns>The item.</returns>
         public object? this[int index] => GetAt(index);
 
+        /// <summary>
+        /// Gets a value that indicates whether the items source can provide a unique key for each item.
+        /// </summary>
+        /// <remarks>
+        /// TODO: Not yet implemented in Avalonia.
+        /// </remarks>
+        internal bool HasKeyIndexMapping => false;
+
         /// <summary>
         /// Occurs when the collection has changed to indicate the reason for the change and which items changed.
         /// </summary>
@@ -91,114 +81,133 @@ namespace Avalonia.Controls
         {
             add
             {
-                if (_collectionChanged is null && Inner is INotifyCollectionChanged incc)
-                {
-                    incc.CollectionChanged += OnCollectionChanged;
-                }
-
+                AddListenerIfNecessary();
                 _collectionChanged += value;
             }
 
             remove
             {
                 _collectionChanged -= value;
-
-                if (_collectionChanged is null && Inner is INotifyCollectionChanged incc)
-                {
-                    incc.CollectionChanged -= OnCollectionChanged;
-                }
+                RemoveListenerIfNecessary();
             }
         }
 
-        /// <inheritdoc/>
-        public void Dispose()
+        /// <summary>
+        /// Occurs when a collection has finished changing and all <see cref="CollectionChanged"/>
+        /// event handlers have been notified.
+        /// </summary>
+        internal event NotifyCollectionChangedEventHandler? PostCollectionChanged
         {
-            if (_inner is INotifyCollectionChanged incc)
+            add
             {
-                incc.CollectionChanged -= OnCollectionChanged;
+                AddListenerIfNecessary();
+                _postCollectionChanged += value;
             }
 
-            _inner = null;
+            remove
+            {
+                _postCollectionChanged -= value;
+                RemoveListenerIfNecessary();
+            }
         }
 
-        /// <summary>
-        /// Retrieves the item at the specified index.
-        /// </summary>
-        /// <param name="index">The index.</param>
-        /// <returns>The item.</returns>
-        public object? GetAt(int index) => Inner[index];
-
-        public int IndexOf(object? item) => Inner.IndexOf(item);
-
-        public static ItemsSourceView GetOrCreate(IEnumerable? items)
+        private void AddListenerIfNecessary()
         {
-            if (items is ItemsSourceView isv)
+            if (!_listening)
             {
-                return isv;
+                if (_inner is INotifyCollectionChanged incc)
+                    CollectionChangedEventManager.Instance.AddListener(incc, this);
+                _listening = true;
             }
-            else if (items is null)
-            {
-                return Empty;
-            }
-            else
+        }
+
+        private void RemoveListenerIfNecessary()
+        {
+            if (_listening && _collectionChanged is null && _postCollectionChanged is null)
             {
-                return new ItemsSourceView(items);
+                if (_inner is INotifyCollectionChanged incc)
+                    CollectionChangedEventManager.Instance.RemoveListener(incc, this);
+                _listening = false;
             }
         }
 
         /// <summary>
-        /// Retrieves the index of the item that has the specified unique identifier (key).
+        /// Retrieves the item at the specified index.
         /// </summary>
         /// <param name="index">The index.</param>
-        /// <returns>The key</returns>
-        /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
-        /// </remarks>
-        public string KeyFromIndex(int index)
-        {
-            throw new NotImplementedException();
-        }
+        /// <returns>The item.</returns>
+        public object? GetAt(int index) => Inner[index];
+
+        /// <summary>
+        /// Determines the index of a specific item in the collection.
+        /// </summary>
+        /// <param name="item">The object to locate in the collection.</param>
+        /// <returns>The index of value if found in the list; otherwise, -1.</returns>
+        public int IndexOf(object? item) => Inner.IndexOf(item);
 
         /// <summary>
-        /// Retrieves the unique identifier (key) for the item at the specified index.
+        /// Gets or creates an <see cref="ItemsSourceView"/> for the specified enumerable.
         /// </summary>
-        /// <param name="key">The key.</param>
-        /// <returns>The index.</returns>
+        /// <param name="items">The enumerable.</param>
         /// <remarks>
-        /// TODO: Not yet implemented in Avalonia.
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
         /// </remarks>
-        public int IndexFromKey(string key)
+        public static ItemsSourceView GetOrCreate(IEnumerable? items)
         {
-            throw new NotImplementedException();
+            return items switch
+            {
+                ItemsSourceView isv => isv,
+                null => Empty,
+                _ => new ItemsSourceView(items)
+            };
         }
 
-        internal void AddListener(ICollectionChangedListener listener)
+        public IEnumerator<object?> GetEnumerator()
         {
-            if (Inner is INotifyCollectionChanged incc)
+            static IEnumerator<object> EnumerateItems(IList list)
             {
-                CollectionChangedEventManager.Instance.AddListener(incc, listener);
+                foreach (var o in list)
+                    yield return o;
             }
+
+            var inner = Inner;
+
+            return inner switch
+            {
+                IEnumerable<object> e => e.GetEnumerator(),
+                _ => EnumerateItems(inner),
+            };
         }
 
-        internal void RemoveListener(ICollectionChangedListener listener)
+        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
+
+        void ICollectionChangedListener.PreChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            if (Inner is INotifyCollectionChanged incc)
-            {
-                CollectionChangedEventManager.Instance.RemoveListener(incc, listener);
-            }
         }
 
-        protected void OnItemsSourceChanged(NotifyCollectionChangedEventArgs args)
+        void ICollectionChangedListener.Changed(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            _collectionChanged?.Invoke(this, args);
+            _collectionChanged?.Invoke(this, e);
         }
 
-        private void OnCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
+        void ICollectionChangedListener.PostChanged(INotifyCollectionChanged sender, NotifyCollectionChangedEventArgs e)
         {
-            OnItemsSourceChanged(e);
+            _postCollectionChanged?.Invoke(this, e);
         }
 
-        private void ThrowDisposed() => throw new ObjectDisposedException(nameof(ItemsSourceView));
+        /// <summary>
+        /// Retrieves the index of the item that has the specified unique identifier (key).
+        /// </summary>
+        /// <param name="index">The index.</param>
+        /// <returns>The key</returns>
+        /// <remarks>
+        /// TODO: Not yet implemented in Avalonia.
+        /// </remarks>
+        internal string KeyFromIndex(int index) => throw new NotImplementedException();
     }
 
     public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
@@ -227,9 +236,7 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="index">The index.</param>
         /// <returns>The item.</returns>
-#pragma warning disable CS8603
         public new T this[int index] => GetAt(index);
-#pragma warning restore CS8603
 
         /// <summary>
         /// Retrieves the item at the specified index.
@@ -238,23 +245,44 @@ namespace Avalonia.Controls
         /// <returns>The item.</returns>
         public new T GetAt(int index) => (T)Inner[index]!;
 
-        public IEnumerator<T> GetEnumerator() => Inner.Cast<T>().GetEnumerator();
-        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
-
-        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
+        public new IEnumerator<T> GetEnumerator()
         {
-            if (items is ItemsSourceView<T> isv)
+            static IEnumerator<T> EnumerateItems(IList list)
             {
-                return isv;
+                foreach (var o in list)
+                    yield return (T)o;
             }
-            else if (items is null)
+
+            var inner = Inner;
+
+            return inner switch
             {
-                return Empty;
-            }
-            else
+                IEnumerable<T> e => e.GetEnumerator(),
+                _ => EnumerateItems(inner),
+            };
+        }
+
+        IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
+
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
+        {
+            return items switch
             {
-                return new ItemsSourceView<T>(items);
-            }
+                ItemsSourceView<T> isv => isv,
+                null => Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
         }
     }
 }
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index dd336974ca..594a1c0f62 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -659,7 +659,7 @@ namespace Avalonia.Controls
 
             if (value)
             {
-                foreach (var item in Items!.OfType<MenuItem>())
+                foreach (var item in ItemsView.OfType<MenuItem>())
                 {
                     item.TryUpdateCanExecute();
                 }
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 8d1e7f0b96..9b38c261e7 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -23,9 +23,7 @@ namespace Avalonia.Controls.Presenters
             
             _presenter = presenter;
             _presenter.ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
-
-            if (_presenter.ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged += OnItemsChanged;
+            _presenter.ItemsControl.ItemsView.PostCollectionChanged += OnItemsChanged;
 
             OnItemsChanged(null, CollectionUtils.ResetEventArgs);
         }
@@ -35,9 +33,7 @@ namespace Avalonia.Controls.Presenters
             if (_presenter.ItemsControl is { } itemsControl)
             {
                 itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
-
-                if (itemsControl.Items is INotifyCollectionChanged incc)
-                    incc.CollectionChanged -= OnItemsChanged;
+                itemsControl.ItemsView.PostCollectionChanged -= OnItemsChanged;
 
                 ClearItemsControlLogicalChildren();
             }
@@ -117,8 +113,7 @@ namespace Avalonia.Controls.Presenters
                 case NotifyCollectionChangedAction.Reset:
                     ClearItemsControlLogicalChildren();
                     children.Clear();
-                    if (_presenter.ItemsControl?.Items is { } items)
-                        Add(0, items);
+                    Add(0, _presenter.ItemsControl.ItemsView);
                     break;
             }
         }
diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 253726c5aa..bc304e24e7 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -380,7 +380,7 @@ namespace Avalonia.Controls.Primitives
         /// Scrolls the specified item into view.
         /// </summary>
         /// <param name="item">The item.</param>
-        public void ScrollIntoView(object item) => ScrollIntoView(IndexOf(Items, item));
+        public void ScrollIntoView(object item) => ScrollIntoView(ItemsView.IndexOf(item));
 
         /// <summary>
         /// Tries to get the container that was the source of an event.
diff --git a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
index 41a0dc384f..b82637b667 100644
--- a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
+++ b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
@@ -628,7 +628,6 @@ namespace Avalonia.Controls
                 oldValue.CollectionChanged -= OnItemsSourceViewChanged;
             }
 
-            ItemsSourceView?.Dispose();
             ItemsSourceView = newValue;
 
             if (newValue != null)
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index 33a5525acc..c5a1a6a7ce 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -21,10 +21,12 @@ namespace Avalonia.Controls.Selection
             {
                 if (_source != value)
                 {
-                    ItemsView?.RemoveListener(this);
+                    if (ItemsView?.Inner is INotifyCollectionChanged inccOld)
+                        CollectionChangedEventManager.Instance.RemoveListener(inccOld, this);
                     _source = value;
                     ItemsView = value is object ? ItemsSourceView<T>.GetOrCreate(value) : null;
-                    ItemsView?.AddListener(this);
+                    if (ItemsView?.Inner is INotifyCollectionChanged inccNew)
+                        CollectionChangedEventManager.Instance.AddListener(inccNew, this);
                 }
             }
         }
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index 0c0de9d544..90e8a60828 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -192,11 +192,8 @@ namespace Avalonia.Controls
 
             void AddItems(ItemsControl itemsControl)
             {
-                if (itemsControl.Items is { } items)
-                {
-                    foreach (var item in items)
-                        allItems.Add(item);
-                }
+                foreach (var item in itemsControl.ItemsView)
+                    allItems.Add(item!);
 
                 foreach (var child in itemsControl.GetRealizedContainers())
                 {
@@ -513,7 +510,7 @@ namespace Avalonia.Controls
                 }
                 else
                 {
-                    SelectedItem = ElementAt(Items, 0);
+                    SelectedItem = ItemsView[0];
                 }
             }
 
diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index 6081fef4e6..538e91053f 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -150,7 +150,7 @@ namespace Avalonia.Controls
                 switch (e.Key)
                 {
                     case Key.Right:
-                        if (Items != null && Items.Cast<object>().Any() && !IsExpanded)
+                        if (ItemsView.Count > 0 && !IsExpanded)
                         {
                             IsExpanded = true;
                             e.Handled = true;
@@ -158,7 +158,7 @@ namespace Avalonia.Controls
                         break;
 
                     case Key.Left:
-                        if (Items is not null && Items.Cast<object>().Any() && IsExpanded)
+                        if (ItemsView.Count > 0 && IsExpanded)
                         {
                             if (IsFocused)
                             {
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index 7ea175fc18..d21959ff8b 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -95,7 +95,7 @@ namespace Avalonia.Controls
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            var items = ItemsControl?.Items as IList ?? Array.Empty<object?>();
+            var items = ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
             var index = (int)_offset.X;
 
             if (index != _realizedIndex)
@@ -195,7 +195,7 @@ namespace Avalonia.Controls
             return null;
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
             base.OnItemsChanged(items, e);
 
@@ -247,7 +247,7 @@ namespace Avalonia.Controls
             InvalidateMeasure();
         }
 
-        private Control GetOrCreateElement(IList items, int index)
+        private Control GetOrCreateElement(ItemsSourceView items, int index)
         {
             return GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -260,7 +260,7 @@ namespace Avalonia.Controls
             return _realizedIndex == index ? _realized : null;
         }
 
-        private Control? GetItemIsOwnContainer(IList items, int index)
+        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -285,7 +285,7 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetRecycledElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -303,7 +303,7 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control CreateElement(IList items, int index)
+        private Control CreateElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 0d0abe148d..59146656e6 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -99,7 +99,7 @@ namespace Avalonia.Controls
         /// new collection, in which case the <see cref="NotifyCollectionChangedAction"/> will
         /// be <see cref="NotifyCollectionChangedAction.Reset"/>.
         /// </remarks>
-        protected virtual void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected virtual void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
         }
 
@@ -158,9 +158,7 @@ namespace Avalonia.Controls
 
             ItemsControl = itemsControl;
             ItemsControl.PropertyChanged += OnItemsControlPropertyChanged;
-
-            if (ItemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged += OnItemsControlItemsChanged;
+            ItemsControl.ItemsView.PostCollectionChanged += OnItemsControlItemsChanged;
         }
 
         internal void Detach()
@@ -168,9 +166,7 @@ namespace Avalonia.Controls
             var itemsControl = EnsureItemsControl();
 
             itemsControl.PropertyChanged -= OnItemsControlPropertyChanged;
-
-            if (itemsControl.Items is INotifyCollectionChanged incc)
-                incc.CollectionChanged -= OnItemsControlItemsChanged;
+            itemsControl.ItemsView.PostCollectionChanged -= OnItemsControlItemsChanged;
 
             ItemsControl = null;
             Children.Clear();
@@ -187,20 +183,18 @@ namespace Avalonia.Controls
 
         private protected virtual void OnItemsControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
-            if (e.Property == ItemsControl.ItemsProperty)
+            if (e.Property == ItemsControl.ItemsViewProperty)
             {
-                if (e.OldValue is INotifyCollectionChanged inccOld)
-                    inccOld.CollectionChanged -= OnItemsControlItemsChanged;
+                var (oldValue, newValue) = e.GetOldAndNewValue<ItemsSourceView>();
+                oldValue.PostCollectionChanged -= OnItemsControlItemsChanged;
                 Refresh();
-                if (e.NewValue is INotifyCollectionChanged inccNew)
-                    inccNew.CollectionChanged += OnItemsControlItemsChanged;
+                newValue.PostCollectionChanged += OnItemsControlItemsChanged;
             }
         }
 
         private void OnItemsControlItemsChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
-            if (_itemsControl?.Items is IList items)
-                OnItemsChanged(items, e);
+            OnItemsChanged(_itemsControl?.ItemsView ?? ItemsSourceView.Empty, e);
         }
 
         [DoesNotReturn]
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 22526fa29c..8f42372179 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics;
@@ -65,7 +64,7 @@ namespace Avalonia.Controls
 
             try
             {
-                var items = ItemsControl?.Items as IList;
+                var items = ItemsControl?.ItemsView;
 
                 if (items is null || items.Count == 0)
                 {
@@ -149,7 +148,7 @@ namespace Avalonia.Controls
             }
         }
 
-        protected override void OnItemsChanged(IList items, NotifyCollectionChangedEventArgs e)
+        protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
             if (_realizedElements is null)
                 return;
@@ -172,7 +171,7 @@ namespace Avalonia.Controls
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
         {
-            var count = (ItemsControl?.Items as IList)?.Count ?? 0;
+            var count = ItemsControl?.ItemsView.Count ?? 0;
 
             if (count == 0 || from is not Control fromControl)
                 return null;
@@ -239,7 +238,7 @@ namespace Avalonia.Controls
 
         protected internal override Control? ScrollIntoView(int index)
         {
-            var items = ItemsControl?.Items as IList;
+            var items = ItemsControl?.ItemsView;
 
             if (_isInLayout || items is null || index < 0 || index >= items.Count)
                 return null;
@@ -296,7 +295,7 @@ namespace Avalonia.Controls
             return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        private MeasureViewport CalculateMeasureViewport(IList items)
+        private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
         {
             Debug.Assert(_realizedElements is not null);
 
@@ -337,7 +336,7 @@ namespace Avalonia.Controls
             };
         }
 
-        private Size CalculateDesiredSize(Orientation orientation, IList items, double sizeV)
+        private Size CalculateDesiredSize(Orientation orientation, ItemsSourceView items, double sizeV)
         {
             var sizeU = EstimateElementSizeU() * items.Count;
 
@@ -402,10 +401,10 @@ namespace Avalonia.Controls
 
         private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            Debug.Assert(ItemsControl?.Items is IList);
+            Debug.Assert(ItemsControl is not null);
             Debug.Assert(_measureElements is not null);
 
-            var items = (IList)ItemsControl!.Items;
+            var items = ItemsControl!.ItemsView;
             var horizontal = Orientation == Orientation.Horizontal;
             var index = viewport.firstIndex;
             var u = viewport.startU;
@@ -426,7 +425,7 @@ namespace Avalonia.Controls
             } while (u < viewport.viewportUEnd && index < items.Count);
         }
 
-        private Control GetOrCreateElement(IList items, int index)
+        private Control GetOrCreateElement(ItemsSourceView items, int index)
         {
             var e = GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -443,7 +442,7 @@ namespace Avalonia.Controls
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetItemIsOwnContainer(IList items, int index)
+        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
             if (items[index] is Control controlItem)
             {
@@ -466,7 +465,7 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control? GetRecycledElement(IList items, int index)
+        private Control? GetRecycledElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 
@@ -485,7 +484,7 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control CreateElement(IList items, int index)
+        private Control CreateElement(ItemsSourceView items, int index)
         {
             Debug.Assert(ItemsControl is not null);
 

From b678339b5dab399489e82f9d288e7473eb16e6ae Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 14:47:17 +0100
Subject: [PATCH 043/157] TreeNodeCollection needs to implement IList now.

---
 .../ViewModels/TreeNodeCollection.cs          | 21 ++++++++++++++++++-
 1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
index 953afa280b..0988fd2891 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
@@ -8,7 +8,7 @@ using Avalonia.Collections;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
-    internal abstract class TreeNodeCollection : IAvaloniaReadOnlyList<TreeNode>, IDisposable
+    internal abstract class TreeNodeCollection : IAvaloniaReadOnlyList<TreeNode>, IList, IDisposable
     {
         private class EmptyTreeNodeCollection : TreeNodeCollection
         {
@@ -33,6 +33,16 @@ namespace Avalonia.Diagnostics.ViewModels
         public int Count => EnsureInitialized().Count;
 
         protected TreeNode Owner { get; }
+        bool IList.IsFixedSize => false;
+        bool IList.IsReadOnly => true;
+        bool ICollection.IsSynchronized => false;
+        object ICollection.SyncRoot => this;
+
+        object? IList.this[int index] 
+        {
+            get => this[index];
+            set => throw new NotImplementedException();
+        }
 
         public event NotifyCollectionChangedEventHandler? CollectionChanged
         {
@@ -75,5 +85,14 @@ namespace Avalonia.Diagnostics.ViewModels
             }
             return _inner;
         }
+
+        int IList.Add(object? value) => throw new NotImplementedException();
+        void IList.Clear() => throw new NotImplementedException();
+        bool IList.Contains(object? value) => throw new NotImplementedException();
+        int IList.IndexOf(object? value) => throw new NotImplementedException();
+        void IList.Insert(int index, object? value) => throw new NotImplementedException();
+        void IList.Remove(object? value) => throw new NotImplementedException();
+        void IList.RemoveAt(int index) => throw new NotImplementedException();
+        void ICollection.CopyTo(Array array, int index) => throw new NotImplementedException();
     }
 }

From 518391b37db2ff1e442f5369a4f2c789039924c2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 14:48:41 +0100
Subject: [PATCH 044/157] Make ItemsSourceView ctors private.

So in future we could have different `ItemSourceView` concrete implementations that e.g. have an inner `IReadOnlyList<T>` in order to address #8764.
---
 src/Avalonia.Controls/ItemsControl.cs         |  2 +-
 src/Avalonia.Controls/ItemsSourceView.cs      | 71 ++++++++++++-------
 .../Repeater/ItemsRepeater.cs                 |  2 +-
 .../Selection/SelectionNodeBase.cs            |  2 +-
 .../ItemsSourceViewTests.cs                   | 11 +--
 5 files changed, 51 insertions(+), 37 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index b797ae8295..f8aa38670f 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -96,7 +96,7 @@ namespace Avalonia.Controls
         /// </summary>
         public ItemsControl()
         {
-            _itemsView = new(_items);
+            _itemsView = ItemsSourceView.GetOrCreate(_items);
             _itemsView.PostCollectionChanged += ItemsCollectionChanged;
             UpdatePseudoClasses(0);
         }
diff --git a/src/Avalonia.Controls/ItemsSourceView.cs b/src/Avalonia.Controls/ItemsSourceView.cs
index 27fa7cbe48..c8fc76255c 100644
--- a/src/Avalonia.Controls/ItemsSourceView.cs
+++ b/src/Avalonia.Controls/ItemsSourceView.cs
@@ -34,7 +34,7 @@ namespace Avalonia.Controls
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
         /// </summary>
         /// <param name="source">The data source.</param>
-        public ItemsSourceView(IEnumerable source)
+        private protected ItemsSourceView(IEnumerable source)
         {
             _inner = source switch
             {
@@ -166,6 +166,48 @@ namespace Avalonia.Controls
             };
         }
 
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static ItemsSourceView<T> GetOrCreate<T>(IEnumerable? items)
+        {
+            return items switch
+            {
+                ItemsSourceView<T> isv => isv,
+                null => ItemsSourceView<T>.Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
+        }
+
+        /// <summary>
+        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
+        /// </summary>
+        /// <param name="items">The enumerable.</param>
+        /// <remarks>
+        /// This method handles the following three cases:
+        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
+        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
+        ///   <see cref="ItemsSourceView"/>
+        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
+        /// </remarks>
+        public static ItemsSourceView<T> GetOrCreate<T>(IEnumerable<T>? items)
+        {
+            return items switch
+            {
+                ItemsSourceView<T> isv => isv,
+                null => ItemsSourceView<T>.Empty,
+                _ => new ItemsSourceView<T>(items)
+            };
+        }
+
         public IEnumerator<object?> GetEnumerator()
         {
             static IEnumerator<object> EnumerateItems(IList list)
@@ -210,7 +252,7 @@ namespace Avalonia.Controls
         internal string KeyFromIndex(int index) => throw new NotImplementedException();
     }
 
-    public class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
+    public sealed class ItemsSourceView<T> : ItemsSourceView, IReadOnlyList<T>
     {
         /// <summary>
         ///  Gets an empty <see cref="ItemsSourceView"/>
@@ -221,12 +263,12 @@ namespace Avalonia.Controls
         /// Initializes a new instance of the ItemsSourceView class for the specified data source.
         /// </summary>
         /// <param name="source">The data source.</param>
-        public ItemsSourceView(IEnumerable<T> source)
+        internal ItemsSourceView(IEnumerable<T> source)
             : base(source)
         {
         }
 
-        private ItemsSourceView(IEnumerable source)
+        internal ItemsSourceView(IEnumerable source)
             : base(source)
         {
         }
@@ -263,26 +305,5 @@ namespace Avalonia.Controls
         }
 
         IEnumerator IEnumerable.GetEnumerator() => Inner.GetEnumerator();
-
-        /// <summary>
-        /// Gets or creates an <see cref="ItemsSourceView{T}"/> for the specified enumerable.
-        /// </summary>
-        /// <param name="items">The enumerable.</param>
-        /// <remarks>
-        /// This method handles the following three cases:
-        /// - If <paramref name="items"/> is null, returns <see cref="Empty"/>
-        /// - If <paramref name="items"/> is an <see cref="ItemsSourceView"/> returns the existing
-        ///   <see cref="ItemsSourceView"/>
-        /// - Otherwise creates a new <see cref="ItemsSourceView"/>
-        /// </remarks>
-        public static new ItemsSourceView<T> GetOrCreate(IEnumerable? items)
-        {
-            return items switch
-            {
-                ItemsSourceView<T> isv => isv,
-                null => Empty,
-                _ => new ItemsSourceView<T>(items)
-            };
-        }
     }
 }
diff --git a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
index b82637b667..4de6a5188d 100644
--- a/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
+++ b/src/Avalonia.Controls/Repeater/ItemsRepeater.cs
@@ -442,7 +442,7 @@ namespace Avalonia.Controls
                     var newDataSource = newEnumerable as ItemsSourceView;
                     if (newEnumerable != null && newDataSource == null)
                     {
-                        newDataSource = new ItemsSourceView(newEnumerable);
+                        newDataSource = ItemsSourceView.GetOrCreate(newEnumerable);
                     }
 
                     OnDataSourcePropertyChanged(ItemsSourceView, newDataSource);
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index c5a1a6a7ce..01b89325af 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -24,7 +24,7 @@ namespace Avalonia.Controls.Selection
                     if (ItemsView?.Inner is INotifyCollectionChanged inccOld)
                         CollectionChangedEventManager.Instance.RemoveListener(inccOld, this);
                     _source = value;
-                    ItemsView = value is object ? ItemsSourceView<T>.GetOrCreate(value) : null;
+                    ItemsView = value is object ? ItemsSourceView.GetOrCreate<T>(value) : null;
                     if (ItemsView?.Inner is INotifyCollectionChanged inccNew)
                         CollectionChangedEventManager.Instance.AddListener(inccNew, this);
                 }
diff --git a/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs b/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
index 22a9b28648..df842b21a7 100644
--- a/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ItemsSourceViewTests.cs
@@ -15,7 +15,7 @@ namespace Avalonia.Controls.UnitTests
         public void Only_Subscribes_To_Source_CollectionChanged_When_CollectionChanged_Subscribed()
         {
             var source = new AvaloniaList<string>();
-            var target = new ItemsSourceView<string>(source);
+            var target = ItemsSourceView.GetOrCreate(source);
             var debug = (INotifyCollectionChangedDebug)source;
 
             Assert.Null(debug.GetCollectionChangedSubscribers());
@@ -31,18 +31,11 @@ namespace Avalonia.Controls.UnitTests
             Assert.Null(debug.GetCollectionChangedSubscribers());
         }
 
-        [Fact]
-        public void Cannot_Wrap_An_ItemsSourceView_In_Another()
-        {
-            var source = new ItemsSourceView<string>(new string[0]);
-            Assert.Throws<ArgumentException>(() => new ItemsSourceView<string>(source));
-        }
-
         [Fact]
         public void Cannot_Create_ItemsSourceView_With_Collection_That_Implements_INCC_But_Not_List()
         {
             var source = new InvalidCollection();
-            Assert.Throws<ArgumentException>(() => new ItemsSourceView<string>(source));
+            Assert.Throws<ArgumentException>(() => ItemsSourceView.GetOrCreate(source));
         }
 
         private class InvalidCollection : INotifyCollectionChanged, IEnumerable<string>

From f042127290dcbf6ff1e9de1d903731aff426d1cc Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:42:29 +0100
Subject: [PATCH 045/157] Implement a few required members.

---
 .../Diagnostics/ViewModels/TreeNodeCollection.cs              | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
index 0988fd2891..77a3697ec1 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNodeCollection.cs
@@ -88,8 +88,8 @@ namespace Avalonia.Diagnostics.ViewModels
 
         int IList.Add(object? value) => throw new NotImplementedException();
         void IList.Clear() => throw new NotImplementedException();
-        bool IList.Contains(object? value) => throw new NotImplementedException();
-        int IList.IndexOf(object? value) => throw new NotImplementedException();
+        bool IList.Contains(object? value) => EnsureInitialized().Contains((TreeNode)value!);
+        int IList.IndexOf(object? value) => EnsureInitialized().IndexOf((TreeNode)value!);
         void IList.Insert(int index, object? value) => throw new NotImplementedException();
         void IList.Remove(object? value) => throw new NotImplementedException();
         void IList.RemoveAt(int index) => throw new NotImplementedException();

From d4a8b98b37b71f25fd41d14fd351bee5ddb1a89a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:43:19 +0100
Subject: [PATCH 046/157] Invalidate measure less.

Only invalidate the measure when the viewport changes in the direction of scroll.
---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 8f42372179..7e5a00e6f7 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -528,9 +528,21 @@ namespace Avalonia.Controls
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
         {
+            var vertical = Orientation == Orientation.Vertical;
+            var oldViewportStart = vertical ? _viewport.Top : _viewport.Left;
+            var oldViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+
             _viewport = e.EffectiveViewport;
             _isWaitingForViewportUpdate = false;
-            InvalidateMeasure();
+
+            var newViewportStart = vertical ? _viewport.Top : _viewport.Left;
+            var newViewportEnd = vertical ? _viewport.Bottom : _viewport.Right;
+
+            if (!MathUtilities.AreClose(oldViewportStart, newViewportStart) ||
+                !MathUtilities.AreClose(oldViewportEnd, newViewportEnd))
+            {
+                InvalidateMeasure();
+            }
         }
 
         private static void InvalidateHack(Control c)

From bcb3a6d5ca55e541c19837fc66a9e6727fcdb5fb Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 15:43:55 +0100
Subject: [PATCH 047/157] Fix side panel width.

Variable width was causing the panel to flicker around as the values change.
---
 samples/VirtualizationDemo/MainWindow.xaml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/VirtualizationDemo/MainWindow.xaml b/samples/VirtualizationDemo/MainWindow.xaml
index 7748ebcc03..235f3ef2cc 100644
--- a/samples/VirtualizationDemo/MainWindow.xaml
+++ b/samples/VirtualizationDemo/MainWindow.xaml
@@ -9,7 +9,7 @@
     <DockPanel LastChildFill="True" Margin="16">
         <StackPanel DockPanel.Dock="Right" 
                     Margin="16 0 0 0" 
-                    MinWidth="150"
+                    Width="150"
                     Spacing="4">
             <ComboBox Items="{Binding Orientations}"
                       SelectedItem="{Binding Orientation}"/>

From 395a90d9207d30f81faa9d01f18ce8e2463c17b8 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 16:11:46 +0100
Subject: [PATCH 048/157] Create containers for remaining ItemsControls.

---
 src/Avalonia.Controls/ComboBox.cs            | 3 +++
 src/Avalonia.Controls/MenuBase.cs            | 3 +++
 src/Avalonia.Controls/MenuItem.cs            | 3 +++
 src/Avalonia.Controls/Primitives/TabStrip.cs | 3 +++
 4 files changed, 12 insertions(+)

diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index a573a9d887..c7ef0d136c 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -170,6 +170,9 @@ namespace Avalonia.Controls
             UpdateFlowDirection();
         }
 
+        protected internal override Control CreateContainerForItemOverride() => new ComboBoxItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is ComboBoxItem;
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuBase.cs b/src/Avalonia.Controls/MenuBase.cs
index 3bbd5b7de4..1918964bc8 100644
--- a/src/Avalonia.Controls/MenuBase.cs
+++ b/src/Avalonia.Controls/MenuBase.cs
@@ -133,6 +133,9 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         bool IMenuElement.MoveSelection(NavigationDirection direction, bool wrap) => MoveSelection(direction, wrap);
 
+        protected internal override Control CreateContainerForItemOverride() => new MenuItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is MenuItem or Separator;
+
         /// <inheritdoc/>
         protected override void OnKeyDown(KeyEventArgs e)
         {
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index 594a1c0f62..49e423aac8 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -349,6 +349,9 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         void IMenuItem.RaiseClick() => RaiseEvent(new RoutedEventArgs(ClickEvent));
 
+        protected internal override Control CreateContainerForItemOverride() => new MenuItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is MenuItem or Separator;
+
         protected override void OnPointerReleased(PointerReleasedEventArgs e)
         {
             base.OnPointerReleased(e);
diff --git a/src/Avalonia.Controls/Primitives/TabStrip.cs b/src/Avalonia.Controls/Primitives/TabStrip.cs
index a6a6f4cec8..b8790d2a44 100644
--- a/src/Avalonia.Controls/Primitives/TabStrip.cs
+++ b/src/Avalonia.Controls/Primitives/TabStrip.cs
@@ -18,6 +18,9 @@ namespace Avalonia.Controls.Primitives
             ItemsPanelProperty.OverrideDefaultValue<TabStrip>(DefaultPanel);
         }
 
+        protected internal override Control CreateContainerForItemOverride() => new TabStripItem();
+        protected internal override bool IsItemItsOwnContainerOverride(Control item) => item is TabStripItem;
+
         /// <inheritdoc/>
         protected override void OnGotFocus(GotFocusEventArgs e)
         {

From 0b3aa3a84bca63c77344a424acbb3a2de7d367a8 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 22:55:08 +0100
Subject: [PATCH 049/157] Prepare new containers before adding to tree.

Prevents compiled bindings failing because the `DataContext` is not yet set and is still inheriting the parent `DataContext`.
---
 src/Avalonia.Controls/ItemsControl.cs                | 12 ++----------
 .../Presenters/PanelContainerGenerator.cs            |  2 +-
 src/Avalonia.Controls/VirtualizingCarouselPanel.cs   |  4 ++--
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index f8aa38670f..a082f8cdec 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -313,9 +313,9 @@ namespace Avalonia.Controls
                 hic.Header = item;
                 hic.HeaderTemplate = itemTemplate;
 
-                var treeTemplate = (itemTemplate ?? hic.FindDataTemplate(item)) as ITreeDataTemplate;
+                itemTemplate ??= hic.FindDataTemplate(item) ?? this.FindDataTemplate(item);
 
-                if (treeTemplate is not null)
+                if (itemTemplate is ITreeDataTemplate treeTemplate)
                 {
                     if (item is not null && treeTemplate.ItemsSelector(item) is { } itemsBinding)
                         BindingOperations.Apply(hic, ItemsProperty, itemsBinding, null);
@@ -481,14 +481,6 @@ namespace Avalonia.Controls
 
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
-            // Putting this precondition in place in case we want to raise an event when a
-            // container is realized. If we want to do that, then the event subscriber will expect
-            // the container to be attached to the tree. Not using IsAttachedToVisualTree here
-            // because a bunch of tests don't have a rooted visual tree.
-            if (container.GetVisualParent() is null)
-                throw new InvalidOperationException(
-                    "Container must be attached to parent before PrepareItemContainer is called.");
-
             var itemContainerTheme = ItemContainerTheme;
 
             if (itemContainerTheme is not null && 
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 9b38c261e7..9ebff9ac7b 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -137,9 +137,9 @@ namespace Avalonia.Controls.Presenters
                 container = generator.CreateContainer();
             }
 
+            generator.PrepareItemContainer(container, item, index);
             itemsControl.AddLogicalChild(container);
             children.Insert(index, container);
-            generator.PrepareItemContainer(container, item, index);
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index d21959ff8b..7f0c0da065 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -275,8 +275,8 @@ namespace Avalonia.Controls
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
-                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, controlItem, index);
+                    AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
                     return controlItem;
                 }
@@ -311,8 +311,8 @@ namespace Avalonia.Controls
             var item = items[index];
             var container = generator.CreateContainer();
 
-            AddInternalChild(container);
             generator.PrepareItemContainer(container, item, index);
+            AddInternalChild(container);
 
             return container;
         }

From 67d200c1000e1d975807aff7e67d3cac9e021433 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 9 Dec 2022 23:43:49 +0100
Subject: [PATCH 050/157] Fix menu theming.

Don't allow child menus to inherit the top level `Menu`'s `ItemContainerTheme` as that is specific to top-level menu items.
---
 src/Avalonia.Controls/ItemsControl.cs |  2 +-
 src/Avalonia.Controls/Menu.cs         | 10 ++++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index a082f8cdec..6b51c3d7f0 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -302,7 +302,7 @@ namespace Avalonia.Controls
             {
                 if (itemTemplate is not null)
                     ic.ItemTemplate = itemTemplate;
-                if (ItemContainerTheme is { } ict)
+                if (ItemContainerTheme is { } ict && !ict.IsSet(ItemContainerThemeProperty))
                     ic.ItemContainerTheme = ict;
             }
 
diff --git a/src/Avalonia.Controls/Menu.cs b/src/Avalonia.Controls/Menu.cs
index c50cce9589..dbdcad8217 100644
--- a/src/Avalonia.Controls/Menu.cs
+++ b/src/Avalonia.Controls/Menu.cs
@@ -93,5 +93,15 @@ namespace Avalonia.Controls
                 inputRoot.AccessKeyHandler.MainMenu = this;
             }
         }
+
+        protected internal override void PrepareContainerForItemOverride(Control element, object? item, int index)
+        {
+            base.PrepareContainerForItemOverride(element, item, index);
+
+            // Child menu items should not inherit the menu's ItemContainerTheme as that is specific
+            // for top-level menu items.
+            if ((element as MenuItem)?.ItemContainerTheme == ItemContainerTheme)
+                element.ClearValue(ItemContainerThemeProperty);
+        }
     }
 }

From 14df77a89735473eaa75605414f5b8a72bcdf250 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 00:22:55 +0100
Subject: [PATCH 051/157] Improve support for variable-sized items.

---
 .../VirtualizingStackPanel.cs                 | 119 ++++++++++++------
 1 file changed, 78 insertions(+), 41 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 7e5a00e6f7..7dde543c2a 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -92,7 +92,7 @@ namespace Avalonia.Controls
 
                 // Recycle elements outside of the expected range.
                 _realizedElements.RecycleElementsBefore(viewport.firstIndex, _recycleElement);
-                _realizedElements.RecycleElementsAfter(viewport.estimatedLastIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(viewport.lastIndex, _recycleElement);
 
                 // Do the measure, creating/recycling elements as necessary to fill the viewport. Don't
                 // write to _realizedElements yet, only _measureElements.
@@ -307,8 +307,8 @@ namespace Avalonia.Controls
             var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
             var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
 
-            var (firstIndex, firstIndexU) = _realizedElements!.GetElementAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetElementAt(viewportEnd);
+            var (firstIndex, firstIndexU) = _realizedElements.GetModelIndexAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetModelIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
 
@@ -329,7 +329,7 @@ namespace Avalonia.Controls
             return new MeasureViewport
             {
                 firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                estimatedLastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                lastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
                 viewportUStart = viewportStart,
                 viewportUEnd = viewportEnd,
                 startU = firstIndexU,
@@ -353,23 +353,9 @@ namespace Avalonia.Controls
             if (_realizedElements is null)
                 return _lastEstimatedElementSizeU;
 
-            var count = _realizedElements.Count;
-            var divisor = 0.0;
-            var total = 0.0;
-
-            for (var i = 0; i < count; ++i)
-            {
-                if (_realizedElements.Elements[i] is object)
-                {
-                    total += _realizedElements.SizeU[i];
-                    ++divisor;
-                }
-            }
-
-            if (divisor == 0 || total == 0)
-                return _lastEstimatedElementSizeU;
-
-            _lastEstimatedElementSizeU = total / divisor;
+            var result = _realizedElements.EstimateElementSizeU();
+            if (result >= 0)
+                _lastEstimatedElementSizeU = result;
             return _lastEstimatedElementSizeU;
         }
 
@@ -409,6 +395,10 @@ namespace Avalonia.Controls
             var index = viewport.firstIndex;
             var u = viewport.startU;
 
+            // The layout is likely invalid. Don't create any elements and instead rely on our previous
+            // element size estimates to calculate a new desired size and trigger a new layout pass.
+            if (index >= items.Count)
+                return;
             do
             {
                 var e = GetOrCreateElement(items, index);
@@ -587,6 +577,7 @@ namespace Avalonia.Controls
             private List<Control?>? _elements;
             private List<double>? _sizes;
             private double _startU;
+            private bool _startUUnstable;
 
             /// <summary>
             /// Gets the number of realized elements.
@@ -671,6 +662,38 @@ namespace Avalonia.Controls
                 return null;
             }
 
+            /// <summary>
+            /// Gets the model index and start U position of the element at the specified U position.
+            /// </summary>
+            /// <param name="u">The U position.</param>
+            /// <returns>
+            /// A tuple containing:
+            /// - The index of the item at the specified U position, or -1 if the item could not be
+            ///   determined
+            /// - The U position of the start of the item, if determined
+            /// </returns>
+            public (int index, double position) GetModelIndexAt(double u)
+            {
+                if (_elements is null || _sizes is null || _startU > u || _startUUnstable)
+                    return (-1, 0);
+
+                var index = 0;
+                var position = _startU;
+
+                while (index < _elements.Count)
+                {
+                    var size = _sizes[index];
+                    if (double.IsNaN(size))
+                        break;
+                    if (u >= position && u < position + size)
+                        return (index + FirstModelIndex, position);
+                    position += size;
+                    ++index;
+                }
+
+                return (-1, 0);
+            }
+
             /// <summary>
             /// Gets the element at the specified position on the primary axis, if realized.
             /// </summary>
@@ -700,33 +723,42 @@ namespace Avalonia.Controls
             }
 
             /// <summary>
-            /// Gets the position of an element on the primary axis, if realized.
+            /// Estimates the average U size of all elements in the source collection based on the
+            /// realized elements.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element.</param>
-            /// <param name="position">
-            /// When the method exits, contains the element's position on the primary axis, if 
-            /// the element is realized.
-            /// </param>
             /// <returns>
-            /// True if the requested element was found, otherwise false.
+            /// The estimated U size of an element, or -1 if not enough information is present to make
+            /// an estimate.
             /// </returns>
-            public bool TryGetElementU(int modelIndex, out double position)
+            public double EstimateElementSizeU()
             {
-                if (_sizes is null || modelIndex < FirstModelIndex || modelIndex > LastModelIndex)
+                var total = 0.0;
+                var divisor = 0.0;
+
+                // Start by averaging the size of the elements before the first realized element.
+                if (FirstModelIndex >= 0 && !_startUUnstable)
                 {
-                    position = double.NaN;
-                    return false;
+                    total += _startU;
+                    divisor += FirstModelIndex;
                 }
 
-                var index = modelIndex - FirstModelIndex;
-                position = StartU;
-
-                for (var i = 0; i < index; ++i)
+                // Average the size of the realized elements.
+                if (_sizes is not null)
                 {
-                    position += _sizes[i];
+                    foreach (var size in _sizes)
+                    {
+                        if (double.IsNaN(size))
+                            continue;
+                        total += size;
+                        ++divisor;
+                    }
                 }
 
-                return true;
+                // We don't have any elements on which to base our estimate.
+                if (divisor == 0 || total == 0)
+                    return -1;
+
+                return total / divisor;
             }
 
             /// <summary>
@@ -781,7 +813,7 @@ namespace Avalonia.Controls
                         // The insertion point was within the realized elements, insert an empty space
                         // in _elements and _sizes.
                         _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, 0.0, count);
+                        _sizes!.InsertMany(index, double.NaN, count);
                     }
                 }
             }
@@ -840,9 +872,13 @@ namespace Avalonia.Controls
                     _sizes!.RemoveRange(start, end - start);
 
                     // If the remove started before and ended within our realized elements, then our new
-                    // first index will be the index where the remove started.
+                    // first index will be the index where the remove started. Mark StartU as unstable
+                    // because we can't rely on it now to estimate element heights.
                     if (startIndex <= 0 && end < last)
+                    {
                         _firstIndex = first = modelIndex;
+                        _startUUnstable = true;
+                    }
 
                     // Update the indexes of the elements after the removed range.
                     end = _elements.Count;
@@ -942,6 +978,7 @@ namespace Avalonia.Controls
             public void ResetForReuse()
             {
                 _startU = _firstIndex = 0;
+                _startUUnstable = false;
                 _elements?.Clear();
                 _sizes?.Clear();
             }
@@ -950,7 +987,7 @@ namespace Avalonia.Controls
         private struct MeasureViewport
         {
             public int firstIndex;
-            public int estimatedLastIndex;
+            public int lastIndex;
             public double viewportUStart;
             public double viewportUEnd;
             public double measuredV;

From 6d267f9d2036047d0a6a1a4ab99ec678c69afba3 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 01:16:11 +0100
Subject: [PATCH 052/157] Add scroll anchoring support to ItemsControl.

This necessitated adding another stage to the container preparation lifecycle that will be called after the container is added to the logical and visual trees: `ItemContainerPrepared`. Such a method is going to be necessary anyway if we ever want to expose events for container realization so will probably be worth having regardless.
---
 .../Generators/ItemContainerGenerator.cs      | 20 +++++++++++++++++--
 src/Avalonia.Controls/ItemsControl.cs         | 18 +++++++++++++++++
 .../Presenters/PanelContainerGenerator.cs     |  1 +
 .../VirtualizingCarouselPanel.cs              | 10 +++++++++-
 .../VirtualizingStackPanel.cs                 | 12 ++++++++---
 5 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index fe8dda3b98..b5dc4903bf 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -56,6 +56,22 @@ namespace Avalonia.Controls.Generators
         public void PrepareItemContainer(Control container, object? item, int index) => 
             _owner.PrepareItemContainer(container, item, index);
 
+        /// <summary>
+        /// Notifies the <see cref="ItemsControl"/> that a container has been fully prepared to
+        /// display an item.
+        /// </summary>
+        /// <param name="container">The container control.</param>
+        /// <param name="item">The item being displayed.</param>
+        /// <param name="index">The index of the item being displayed.</param>
+        /// <remarks>
+        /// This method should be called when a container has been fully prepared and added
+        /// to the logical and visual trees, but may be called before a layout pass has completed.
+        /// It should be called regardless of the result of
+        /// <see cref="IsItemItsOwnContainer(Control)"/>.
+        /// </remarks>
+        public void ItemContainerPrepared(Control container, object? item, int index) =>
+            _owner.ItemContainerPrepared(container, item, index);
+
         /// <summary>
         /// Called when the index for a container changes due to an insertion or removal in the
         /// items collection.
@@ -69,8 +85,8 @@ namespace Avalonia.Controls.Generators
         /// <summary>
         /// Undoes the effects of the <see cref="PrepareItemContainer(Control, object, int)"/> method.
         /// </summary>
-        /// <param name="container">The element that's used to display the specified item.</param>
-        public void ClearItemContainer(Control container) => _owner.ClearContainerForItemOverride(container);
+        /// <param name="container">The container control.</param>
+        public void ClearItemContainer(Control container) => _owner.ClearItemContainer(container);
 
         public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
         public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6b51c3d7f0..6dad539efc 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -90,6 +90,7 @@ namespace Avalonia.Controls
         private EventHandler<ChildIndexChangedEventArgs>? _childIndexChanged;
         private IDataTemplate? _displayMemberItemTemplate;
         private Tuple<int, Control>? _containerBeingPrepared;
+        private ScrollViewer? _scrollViewer;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="ItemsControl"/> class.
@@ -351,6 +352,12 @@ namespace Avalonia.Controls
         /// <returns>true if the item is (or is eligible to be) its own container; otherwise, false.</returns>
         protected internal virtual bool IsItemItsOwnContainerOverride(Control item) => true;
 
+        protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
+        {
+            base.OnApplyTemplate(e);
+            _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+        }
+
         /// <summary>
         /// Handles directional navigation within the <see cref="ItemsControl"/>.
         /// </summary>
@@ -494,10 +501,15 @@ namespace Avalonia.Controls
                 container.DataContext = item;
 
             PrepareContainerForItemOverride(container, item, index);
+        }
 
+        internal void ItemContainerPrepared(Control container, object? item, int index)
+        {
             _containerBeingPrepared = new(index, container);
             _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
             _containerBeingPrepared = null;
+
+            _scrollViewer?.RegisterAnchorCandidate(container);
         }
 
         internal void ItemContainerIndexChanged(Control container, int oldIndex, int newIndex)
@@ -506,6 +518,12 @@ namespace Avalonia.Controls
             _childIndexChanged?.Invoke(this, new ChildIndexChangedEventArgs(container));
         }
 
+        internal void ClearItemContainer(Control container)
+        {
+            _scrollViewer?.UnregisterAnchorCandidate(container);
+            ClearContainerForItemOverride(container);
+        }
+
         /// <summary>
         /// Given a collection of items, adds those that are controls to the logical children.
         /// </summary>
diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 9ebff9ac7b..1c94c29a35 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -140,6 +140,7 @@ namespace Avalonia.Controls.Presenters
             generator.PrepareItemContainer(container, item, index);
             itemsControl.AddLogicalChild(container);
             children.Insert(index, container);
+            generator.ItemContainerPrepared(container, item, index);
         }
 
         private void ClearItemsControlLogicalChildren()
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index 7f0c0da065..b12be377c4 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -2,9 +2,11 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
+using System.ComponentModel;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
+using System.Xml.Linq;
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -264,13 +266,16 @@ namespace Avalonia.Controls
         {
             Debug.Assert(ItemsControl is not null);
 
-            if (items[index] is Control controlItem)
+            var item = items[index];
+
+            if (item is Control controlItem)
             {
                 var generator = ItemsControl!.ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
@@ -278,6 +283,7 @@ namespace Avalonia.Controls
                     generator.PrepareItemContainer(controlItem, controlItem, index);
                     AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
             }
@@ -297,6 +303,7 @@ namespace Avalonia.Controls
                 var recycled = _recyclePool.Pop();
                 recycled.IsVisible = true;
                 generator.PrepareItemContainer(recycled, item, index);
+                generator.ItemContainerPrepared(recycled, item, index);
                 return recycled;
             }
 
@@ -313,6 +320,7 @@ namespace Avalonia.Controls
 
             generator.PrepareItemContainer(container, item, index);
             AddInternalChild(container);
+            generator.ItemContainerPrepared(container, item, index);
 
             return container;
         }
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 7dde543c2a..e88b10dceb 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -434,20 +434,24 @@ namespace Avalonia.Controls
 
         private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
         {
-            if (items[index] is Control controlItem)
+            var item = items[index];
+
+            if (item is Control controlItem)
             {
                 var generator = ItemsControl!.ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
                     controlItem.IsVisible = true;
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
                 else if (generator.IsItemItsOwnContainer(controlItem))
                 {
-                    AddInternalChild(controlItem);
                     generator.PrepareItemContainer(controlItem, controlItem, index);
+                    AddInternalChild(controlItem);
                     controlItem.SetValue(ItemIsOwnContainerProperty, true);
+                    generator.ItemContainerPrepared(controlItem, item, index);
                     return controlItem;
                 }
             }
@@ -468,6 +472,7 @@ namespace Avalonia.Controls
                 var recycled = _recyclePool.Pop();
                 recycled.IsVisible = true;
                 generator.PrepareItemContainer(recycled, item, index);
+                generator.ItemContainerPrepared(recycled, item, index);
                 return recycled;
             }
 
@@ -482,8 +487,9 @@ namespace Avalonia.Controls
             var item = items[index];
             var container = generator.CreateContainer();
 
-            AddInternalChild(container);
             generator.PrepareItemContainer(container, item, index);
+            AddInternalChild(container);
+            generator.ItemContainerPrepared(container, item, index);
 
             return container;
         }

From 95e854ab136279faee4619ccad98b0a4a966b558 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 17:17:25 +0100
Subject: [PATCH 053/157] Mark methods obsolete.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index b5dc4903bf..d362ea24f1 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -88,7 +88,10 @@ namespace Avalonia.Controls.Generators
         /// <param name="container">The container control.</param>
         public void ClearItemContainer(Control container) => _owner.ClearItemContainer(container);
 
+        [Obsolete("Use ItemsControl.ContainerFromIndex")]
         public Control? ContainerFromIndex(int index) => _owner.ContainerFromIndex(index);
+
+        [Obsolete("Use ItemsControl.IndexFromContainer")]
         public int IndexFromContainer(Control container) => _owner.IndexFromContainer(container);
     }
 }

From d7201d28e6c9c396a13ffdaff9bf0ed53da2b70c Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 17:26:53 +0100
Subject: [PATCH 054/157] Removed IItemsPresenterHost.

---
 src/Avalonia.Controls/ItemsControl.cs         | 23 +++++++++++-----
 .../Presenters/IItemsPresenterHost.cs         | 26 -------------------
 .../Presenters/ItemsPresenter.cs              |  2 +-
 ...valoniaXamlIlDataContextTypeTransformer.cs |  2 +-
 .../AvaloniaXamlIlWellKnownTypes.cs           |  4 +--
 5 files changed, 20 insertions(+), 37 deletions(-)
 delete mode 100644 src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 6dad539efc..4e89c2da17 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -23,7 +23,7 @@ namespace Avalonia.Controls
     /// Displays a collection of items.
     /// </summary>
     [PseudoClasses(":empty", ":singleitem")]
-    public class ItemsControl : TemplatedControl, IItemsPresenterHost, IChildIndexProvider
+    public class ItemsControl : TemplatedControl, IChildIndexProvider
     {
         /// <summary>
         /// The default value for the <see cref="ItemsPanel"/> property.
@@ -250,12 +250,6 @@ namespace Avalonia.Controls
         /// </summary>
         public IEnumerable<Control> GetRealizedContainers() => Presenter?.GetRealizedContainers() ?? Array.Empty<Control>();
 
-        /// <inheritdoc/>
-        void IItemsPresenterHost.RegisterItemsPresenter(ItemsPresenter presenter)
-        {
-            Presenter = presenter;
-            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
-        }
 
         /// <summary>
         /// Creates or a container that can be used to display an item.
@@ -486,6 +480,21 @@ namespace Avalonia.Controls
         internal void AddLogicalChild(Control c) => LogicalChildren.Add(c);
         internal void RemoveLogicalChild(Control c) => LogicalChildren.Remove(c);
 
+        /// <summary>
+        /// Called by <see cref="ItemsPresenter"/> to register with the <see cref="ItemsControl"/>.
+        /// </summary>
+        /// <param name="presenter">The items presenter.</param>
+        /// <remarks>
+        /// ItemsPresenters can be within nested templates or in popups and so are not necessarily
+        /// created immediately when the ItemsControl control's template is instantiated. Instead
+        /// they register themselves using this method.
+        /// </remarks>
+        internal void RegisterItemsPresenter(ItemsPresenter presenter)
+        {
+            Presenter = presenter;
+            _childIndexChanged?.Invoke(this, ChildIndexChangedEventArgs.Empty);
+        }
+
         internal void PrepareItemContainer(Control container, object? item, int index)
         {
             var itemContainerTheme = ItemContainerTheme;
diff --git a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs b/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
deleted file mode 100644
index 8bf190dbda..0000000000
--- a/src/Avalonia.Controls/Presenters/IItemsPresenterHost.cs
+++ /dev/null
@@ -1,26 +0,0 @@
-using Avalonia.Metadata;
-using Avalonia.Styling;
-
-namespace Avalonia.Controls.Presenters
-{
-    /// <summary>
-    /// Represents a control which hosts an items presenter.
-    /// </summary>
-    /// <remarks>
-    /// This interface is implemented by <see cref="ItemsControl"/> which usually contains an
-    /// <see cref="ItemsPresenter"/> and exposes it through its 
-    /// <see cref="ItemsControl.Presenter"/> property. ItemsPresenters can be within
-    /// nested templates or in popups and so are not necessarily created immediately when the
-    /// parent control's template is instantiated so they register themselves using this 
-    /// interface.
-    /// </remarks>
-    [NotClientImplementable]
-    public interface IItemsPresenterHost
-    {
-        /// <summary>
-        /// Registers an <see cref="ItemsPresenter"/> with a host control.
-        /// </summary>
-        /// <param name="presenter">The items presenter.</param>
-        void RegisterItemsPresenter(ItemsPresenter presenter);
-    }
-}
diff --git a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
index 8297922664..e0252feed5 100644
--- a/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ItemsPresenter.cs
@@ -143,7 +143,7 @@ namespace Avalonia.Controls.Presenters
                 if (change.NewValue is ItemsControl itemsControl)
                 {
                     ItemsControl = itemsControl;
-                    ((IItemsPresenterHost)itemsControl)?.RegisterItemsPresenter(this);
+                    ItemsControl.RegisterItemsPresenter(this);
                 }
             }
             else if (change.Property == ItemsPanelProperty)
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
index d4dfcf9c4b..574d46e737 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlDataContextTypeTransformer.cs
@@ -79,7 +79,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                         {
                             var parentType = parentObject.Type.GetClrType();
 
-                            if (context.GetAvaloniaTypes().IItemsPresenterHost.IsDirectlyAssignableFrom(parentType)
+                            if (context.GetAvaloniaTypes().ItemsControl.IsDirectlyAssignableFrom(parentType)
                                 || context.GetAvaloniaTypes().ItemsRepeater.IsDirectlyAssignableFrom(parentType))
                             {
                                 inferredDataContextTypeNode = InferDataContextOfPresentedItem(context, on, parentObject);
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
index 87a037c16a..c5bfdd8687 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlWellKnownTypes.cs
@@ -54,7 +54,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
 
         public IXamlType DataTemplate { get; }
         public IXamlType IDataTemplate { get; }
-        public IXamlType IItemsPresenterHost { get; }
+        public IXamlType ItemsControl { get; }
         public IXamlType ItemsRepeater { get; }
         public IXamlType ReflectionBindingExtension { get; }
 
@@ -177,7 +177,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
             ResolveByNameExtension = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.MarkupExtensions.ResolveByNameExtension");
             DataTemplate = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.Templates.DataTemplate");
             IDataTemplate = cfg.TypeSystem.GetType("Avalonia.Controls.Templates.IDataTemplate");
-            IItemsPresenterHost = cfg.TypeSystem.GetType("Avalonia.Controls.Presenters.IItemsPresenterHost");
+            ItemsControl = cfg.TypeSystem.GetType("Avalonia.Controls.ItemsControl");
             ItemsRepeater = cfg.TypeSystem.GetType("Avalonia.Controls.ItemsRepeater");
             ReflectionBindingExtension = cfg.TypeSystem.GetType("Avalonia.Markup.Xaml.MarkupExtensions.ReflectionBindingExtension");
             RelativeSource = cfg.TypeSystem.GetType("Avalonia.Data.RelativeSource");

From d5a585d7225c6f4ae1d371db8f1e6b40ccf33870 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 21:29:49 +0100
Subject: [PATCH 055/157] Tweaked VirtualizingPanel API.

And added some more doc comments.
---
 .../Generators/ItemContainerGenerator.cs      | 18 ++++++-
 .../VirtualizingCarouselPanel.cs              | 29 +++++------
 src/Avalonia.Controls/VirtualizingPanel.cs    | 28 ++++++++++-
 .../VirtualizingStackPanel.cs                 | 48 ++++++++++---------
 4 files changed, 82 insertions(+), 41 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index d362ea24f1..b6f54d51eb 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -6,7 +6,23 @@ namespace Avalonia.Controls.Generators
     /// Generates containers for an <see cref="ItemsControl"/>.
     /// </summary>
     /// <remarks>
-    /// Although this class is similar to that found in WPF/UWP, in Avalonia this class only
+    /// When creating a container for an item from a <see cref="VirtualizingPanel"/>, the following
+    /// method order should be followed:
+    /// 
+    /// - <see cref="IsItemItsOwnContainer(Control)"/> should first be called if the item is
+    ///   derived from the <see cref="Control"/> class. If this method returns true then the
+    ///   item itself should be used as the container.
+    /// - If <see cref="IsItemItsOwnContainer(Control)"/> returns false then
+    ///   <see cref="CreateContainer"/> should be called to create a new container.
+    /// - <see cref="PrepareItemContainer(Control, object?, int)"/> method should be called for the
+    ///   container.
+    /// - The container should then be added to the panel using 
+    ///   <see cref="VirtualizingPanel.AddInternalChild(Control)"/>
+    /// - Finally, <see cref="ItemContainerPrepared(Control, object?, int)"/> should be called.
+    /// - When the item is ready to be recycled, <see cref="ClearItemContainer(Control)"/> should
+    ///   be called if <see cref="IsItemItsOwnContainer(Control)"/> returned false.
+    /// 
+    /// NOTE: Although this class is similar to that found in WPF/UWP, in Avalonia this class only
     /// concerns itself with generating and clearing item containers; it does not maintain a
     /// record of the currently realized containers, that responsibility is delegated to the
     /// items panel.
diff --git a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
index b12be377c4..f655fd18d4 100644
--- a/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingCarouselPanel.cs
@@ -1,12 +1,9 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
-using System.ComponentModel;
 using System.Diagnostics;
 using System.Threading;
 using System.Threading.Tasks;
-using System.Xml.Linq;
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
@@ -97,7 +94,7 @@ namespace Avalonia.Controls
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            var items = ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
+            var items = Items;
             var index = (int)_offset.X;
 
             if (index != _realizedIndex)
@@ -249,7 +246,7 @@ namespace Avalonia.Controls
             InvalidateMeasure();
         }
 
-        private Control GetOrCreateElement(ItemsSourceView items, int index)
+        private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
         {
             return GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -262,15 +259,15 @@ namespace Avalonia.Controls
             return _realizedIndex == index ? _realized : null;
         }
 
-        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
+        private Control? GetItemIsOwnContainer(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
             var item = items[index];
 
             if (item is Control controlItem)
             {
-                var generator = ItemsControl!.ItemContainerGenerator;
+                var generator = ItemContainerGenerator;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
@@ -291,11 +288,11 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control? GetRecycledElement(ItemsSourceView items, int index)
+        private Control? GetRecycledElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator;
             var item = items[index];
 
             if (_recyclePool?.Count > 0)
@@ -310,11 +307,11 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control CreateElement(ItemsSourceView items, int index)
+        private Control CreateElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator;
             var item = items[index];
             var container = generator.CreateContainer();
 
@@ -327,7 +324,7 @@ namespace Avalonia.Controls
 
         private void RecycleElement(Control element)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
             if (element.IsSet(ItemIsOwnContainerProperty))
             {
@@ -335,7 +332,7 @@ namespace Avalonia.Controls
             }
             else
             {
-                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                ItemContainerGenerator.ClearItemContainer(element);
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 59146656e6..62918c3d35 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -1,20 +1,44 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.Diagnostics.CodeAnalysis;
+using Avalonia.Controls.Generators;
+using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
+using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
     /// <summary>
-    /// Base class for panels that can be used to virtualize items.
+    /// Base class for panels that can be used to virtualize items for an <see cref="ItemsControl"/>.
     /// </summary>
+    /// <remarks>
+    /// Panels should implement the abstract members of this class to provide virtualization of
+    /// items in a <see cref="ItemsControl"/>. Derived panels can manage scrolling by implementing
+    /// <see cref="ILogicalScrollable"/> or by listening to the 
+    /// <see cref="Layoutable.EffectiveViewportChanged"/> event.
+    /// 
+    /// The methods on the <see cref="ItemContainerGenerator"/> should be used to create, prepare and
+    /// clear containers for items.
+    /// </remarks>
     public abstract class VirtualizingPanel : Panel, INavigableContainer
     {
         private ItemsControl? _itemsControl;
 
+        /// <summary>
+        /// Gets the <see cref="ItemContainerGenerator"/> for this <see cref="VirtualizingPanel"/>.
+        /// </summary>
+        public ItemContainerGenerator? ItemContainerGenerator => _itemsControl?.ItemContainerGenerator;
+
+        /// <summary>
+        /// Gets the items to display.
+        /// </summary>
+        protected IReadOnlyList<object?> Items => ItemsControl?.ItemsView ?? ItemsSourceView.Empty;
+
+        /// <summary>
+        /// Gets the <see cref="ItemsControl"/> that the panel is displaying items for.
+        /// </summary>
         protected ItemsControl? ItemsControl 
         {
             get => _itemsControl;
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index e88b10dceb..8471595a46 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -11,6 +11,9 @@ using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
 {
+    /// <summary>
+    /// Arranges and virtualizes content on a single line that is oriented either horizontally or vertically.
+    /// </summary>
     public class VirtualizingStackPanel : VirtualizingPanel
     {
         /// <summary>
@@ -64,9 +67,9 @@ namespace Avalonia.Controls
 
             try
             {
-                var items = ItemsControl?.ItemsView;
+                var items = Items;
 
-                if (items is null || items.Count == 0)
+                if (items.Count == 0)
                 {
                     RemoveInternalChildRange(0, Children.Count);
                     return default;
@@ -171,7 +174,7 @@ namespace Avalonia.Controls
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
         {
-            var count = ItemsControl?.ItemsView.Count ?? 0;
+            var count = Items.Count;
 
             if (count == 0 || from is not Control fromControl)
                 return null;
@@ -238,9 +241,9 @@ namespace Avalonia.Controls
 
         protected internal override Control? ScrollIntoView(int index)
         {
-            var items = ItemsControl?.ItemsView;
+            var items = Items;
 
-            if (_isInLayout || items is null || index < 0 || index >= items.Count)
+            if (_isInLayout || index < 0 || index >= items.Count)
                 return null;
 
             if (GetRealizedElement(index) is Control element)
@@ -295,7 +298,7 @@ namespace Avalonia.Controls
             return _realizedElements?.Elements ?? Array.Empty<Control>();
         }
 
-        private MeasureViewport CalculateMeasureViewport(ItemsSourceView items)
+        private MeasureViewport CalculateMeasureViewport(IReadOnlyList<object?> items)
         {
             Debug.Assert(_realizedElements is not null);
 
@@ -336,7 +339,7 @@ namespace Avalonia.Controls
             };
         }
 
-        private Size CalculateDesiredSize(Orientation orientation, ItemsSourceView items, double sizeV)
+        private Size CalculateDesiredSize(Orientation orientation, IReadOnlyList<object?> items, double sizeV)
         {
             var sizeU = EstimateElementSizeU() * items.Count;
 
@@ -387,10 +390,9 @@ namespace Avalonia.Controls
 
         private void GenerateElements(Size availableSize, ref MeasureViewport viewport)
         {
-            Debug.Assert(ItemsControl is not null);
             Debug.Assert(_measureElements is not null);
 
-            var items = ItemsControl!.ItemsView;
+            var items = Items;
             var horizontal = Orientation == Orientation.Horizontal;
             var index = viewport.firstIndex;
             var u = viewport.startU;
@@ -415,7 +417,7 @@ namespace Avalonia.Controls
             } while (u < viewport.viewportUEnd && index < items.Count);
         }
 
-        private Control GetOrCreateElement(ItemsSourceView items, int index)
+        private Control GetOrCreateElement(IReadOnlyList<object?> items, int index)
         {
             var e = GetRealizedElement(index) ??
                 GetItemIsOwnContainer(items, index) ??
@@ -432,13 +434,13 @@ namespace Avalonia.Controls
             return _realizedElements?.GetElement(index);
         }
 
-        private Control? GetItemIsOwnContainer(ItemsSourceView items, int index)
+        private Control? GetItemIsOwnContainer(IReadOnlyList<object?> items, int index)
         {
             var item = items[index];
 
             if (item is Control controlItem)
             {
-                var generator = ItemsControl!.ItemContainerGenerator;
+                var generator = ItemContainerGenerator!;
 
                 if (controlItem.IsSet(ItemIsOwnContainerProperty))
                 {
@@ -459,11 +461,11 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control? GetRecycledElement(ItemsSourceView items, int index)
+        private Control? GetRecycledElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator!;
             var item = items[index];
 
 
@@ -479,11 +481,11 @@ namespace Avalonia.Controls
             return null;
         }
 
-        private Control CreateElement(ItemsSourceView items, int index)
+        private Control CreateElement(IReadOnlyList<object?> items, int index)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
 
-            var generator = ItemsControl!.ItemContainerGenerator;
+            var generator = ItemContainerGenerator!;
             var item = items[index];
             var container = generator.CreateContainer();
 
@@ -502,7 +504,7 @@ namespace Avalonia.Controls
 
         private void RecycleElement(Control element)
         {
-            Debug.Assert(ItemsControl is not null);
+            Debug.Assert(ItemContainerGenerator is not null);
             
             if (element.IsSet(ItemIsOwnContainerProperty))
             {
@@ -510,7 +512,7 @@ namespace Avalonia.Controls
             }
             else
             {
-                ItemsControl!.ItemContainerGenerator.ClearItemContainer(element);
+                ItemContainerGenerator!.ClearItemContainer(element);
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
@@ -519,7 +521,9 @@ namespace Avalonia.Controls
 
         private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
-            ItemsControl!.ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
+            Debug.Assert(ItemContainerGenerator is not null);
+
+            ItemContainerGenerator.ItemContainerIndexChanged(element, oldIndex, newIndex);
         }
 
         private void OnEffectiveViewportChanged(object? sender, EffectiveViewportChangedEventArgs e)
@@ -575,7 +579,7 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/> in smooth mode.
+        /// Stores the realized element state for a <see cref="VirtualizingStackPanel"/>.
         /// </summary>
         internal class RealizedElementList
         {

From 9610c80bd3a868e42409d6266f1ee9f39679d845 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Sat, 10 Dec 2022 21:34:10 +0100
Subject: [PATCH 056/157] Remove references to "model index".

It's a TreeDataGrid concept (which is where this code was adapted from).
---
 .../VirtualizingStackPanel.cs                 | 120 +++++++++---------
 1 file changed, 60 insertions(+), 60 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 8471595a46..a02d963ff8 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -102,7 +102,7 @@ namespace Avalonia.Controls
                 GenerateElements(availableSize, ref viewport);
 
                 // Now we know what definitely fits, recycle anything left over.
-                _realizedElements.RecycleElementsAfter(_measureElements.LastModelIndex, _recycleElement);
+                _realizedElements.RecycleElementsAfter(_measureElements.LastIndex, _recycleElement);
 
                 // And swap the measureElements and realizedElements collection.
                 (_measureElements, _realizedElements) = (_realizedElements, _measureElements);
@@ -310,8 +310,8 @@ namespace Avalonia.Controls
             var viewportStart = Orientation == Orientation.Horizontal ? viewport.X : viewport.Y;
             var viewportEnd = Orientation == Orientation.Horizontal ? viewport.Right : viewport.Bottom;
 
-            var (firstIndex, firstIndexU) = _realizedElements.GetModelIndexAt(viewportStart);
-            var (lastIndex, _) = _realizedElements.GetModelIndexAt(viewportEnd);
+            var (firstIndex, firstIndexU) = _realizedElements.GetIndexAt(viewportStart);
+            var (lastIndex, _) = _realizedElements.GetIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
 
@@ -595,14 +595,14 @@ namespace Avalonia.Controls
             public int Count => _elements?.Count ?? 0;
 
             /// <summary>
-            /// Gets the model index of the first realized element, or -1 if no elements are realized.
+            /// Gets the index of the first realized element, or -1 if no elements are realized.
             /// </summary>
-            public int FirstModelIndex => _elements?.Count > 0 ? _firstIndex : -1;
+            public int FirstIndex => _elements?.Count > 0 ? _firstIndex : -1;
 
             /// <summary>
-            /// Gets the model index of the last realized element, or -1 if no elements are realized.
+            /// Gets the index of the last realized element, or -1 if no elements are realized.
             /// </summary>
-            public int LastModelIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
+            public int LastIndex => _elements?.Count > 0 ? _firstIndex + _elements.Count - 1 : -1;
 
             /// <summary>
             /// Gets the elements.
@@ -622,14 +622,14 @@ namespace Avalonia.Controls
             /// <summary>
             /// Adds a newly realized element to the collection.
             /// </summary>
-            /// <param name="modelIndex">The model index of the element.</param>
+            /// <param name="index">The index of the element.</param>
             /// <param name="element">The element.</param>
             /// <param name="u">The position of the elemnt on the primary axis.</param>
             /// <param name="sizeU">The size of the element on the primary axis.</param>
-            public void Add(int modelIndex, Control element, double u, double sizeU)
+            public void Add(int index, Control element, double u, double sizeU)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
 
                 _elements ??= new List<Control?>();
                 _sizes ??= new List<double>();
@@ -639,14 +639,14 @@ namespace Avalonia.Controls
                     _elements.Add(element);
                     _sizes.Add(sizeU);
                     _startU = u;
-                    _firstIndex = modelIndex;
+                    _firstIndex = index;
                 }
-                else if (modelIndex == LastModelIndex + 1)
+                else if (index == LastIndex + 1)
                 {
                     _elements.Add(element);
                     _sizes.Add(sizeU);
                 }
-                else if (modelIndex == FirstModelIndex - 1)
+                else if (index == FirstIndex - 1)
                 {
                     --_firstIndex;
                     _elements.Insert(0, element);
@@ -660,20 +660,20 @@ namespace Avalonia.Controls
             }
 
             /// <summary>
-            /// Gets the element at the specified model index, if realized.
+            /// Gets the element at the specified index, if realized.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the element to get.</param>
+            /// <param name="index">The index in the source collection of the element to get.</param>
             /// <returns>The element if realized; otherwise null.</returns>
-            public Control? GetElement(int modelIndex)
+            public Control? GetElement(int index)
             {
-                var index = modelIndex - FirstModelIndex;
-                if (index >= 0 && index < _elements?.Count)
-                    return _elements[index];
+                var i = index - FirstIndex;
+                if (i >= 0 && i < _elements?.Count)
+                    return _elements[i];
                 return null;
             }
 
             /// <summary>
-            /// Gets the model index and start U position of the element at the specified U position.
+            /// Gets the index and start U position of the element at the specified U position.
             /// </summary>
             /// <param name="u">The U position.</param>
             /// <returns>
@@ -682,7 +682,7 @@ namespace Avalonia.Controls
             ///   determined
             /// - The U position of the start of the item, if determined
             /// </returns>
-            public (int index, double position) GetModelIndexAt(double u)
+            public (int index, double position) GetIndexAt(double u)
             {
                 if (_elements is null || _sizes is null || _startU > u || _startUUnstable)
                     return (-1, 0);
@@ -696,7 +696,7 @@ namespace Avalonia.Controls
                     if (double.IsNaN(size))
                         break;
                     if (u >= position && u < position + size)
-                        return (index + FirstModelIndex, position);
+                        return (index + FirstIndex, position);
                     position += size;
                     ++index;
                 }
@@ -718,7 +718,7 @@ namespace Avalonia.Controls
                     return (-1, 0);
 
                 var u = StartU;
-                var i = FirstModelIndex;
+                var i = FirstIndex;
 
                 foreach (var size in _sizes)
                 {
@@ -746,10 +746,10 @@ namespace Avalonia.Controls
                 var divisor = 0.0;
 
                 // Start by averaging the size of the elements before the first realized element.
-                if (FirstModelIndex >= 0 && !_startUUnstable)
+                if (FirstIndex >= 0 && !_startUUnstable)
                 {
                     total += _startU;
-                    divisor += FirstModelIndex;
+                    divisor += FirstIndex;
                 }
 
                 // Average the size of the realized elements.
@@ -772,38 +772,38 @@ namespace Avalonia.Controls
             }
 
             /// <summary>
-            /// Gets the model index of the specified element.
+            /// Gets the index of the specified element.
             /// </summary>
             /// <param name="element">The element.</param>
-            /// <returns>The model index or -1 if the element is not present in the collection.</returns>
+            /// <returns>The index or -1 if the element is not present in the collection.</returns>
             public int GetIndex(Control element)
             {
-                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstModelIndex : -1;
+                return _elements?.IndexOf(element) is int index && index >= 0 ? index + FirstIndex : -1;
             }
 
             /// <summary>
             /// Updates the elements in response to items being inserted into the source collection.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the insert.</param>
+            /// <param name="index">The index in the source collection of the insert.</param>
             /// <param name="count">The number of items inserted.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
-            public void ItemsInserted(int modelIndex, int count, Action<Control, int, int> updateElementIndex)
+            public void ItemsInserted(int index, int count, Action<Control, int, int> updateElementIndex)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
                 if (_elements is null || _elements.Count == 0)
                     return;
 
                 // Get the index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var index = modelIndex - first;
+                var first = FirstIndex;
+                var realizedIndex = index - first;
 
-                if (index < Count)
+                if (realizedIndex < Count)
                 {
                     // The insertion point affects the realized elements. Update the index of the
                     // elements after the insertion point.
                     var elementCount = _elements.Count;
-                    var start = Math.Max(index, 0);
+                    var start = Math.Max(realizedIndex, 0);
                     var newIndex = first + count;
 
                     for (var i = start; i < elementCount; ++i)
@@ -813,7 +813,7 @@ namespace Avalonia.Controls
                         ++newIndex;
                     }
 
-                    if (index <= 0)
+                    if (realizedIndex <= 0)
                     {
                         // The insertion point was before the first element, update the first index.
                         _firstIndex += count;
@@ -822,8 +822,8 @@ namespace Avalonia.Controls
                     {
                         // The insertion point was within the realized elements, insert an empty space
                         // in _elements and _sizes.
-                        _elements!.InsertMany(index, null, count);
-                        _sizes!.InsertMany(index, double.NaN, count);
+                        _elements!.InsertMany(realizedIndex, null, count);
+                        _sizes!.InsertMany(realizedIndex, double.NaN, count);
                     }
                 }
             }
@@ -831,26 +831,26 @@ namespace Avalonia.Controls
             /// <summary>
             /// Updates the elements in response to items being removed from the source collection.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of the remove.</param>
+            /// <param name="index">The index in the source collection of the remove.</param>
             /// <param name="count">The number of items removed.</param>
             /// <param name="updateElementIndex">A method used to update the element indexes.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
             public void ItemsRemoved(
-                int modelIndex,
+                int index,
                 int count,
                 Action<Control, int, int> updateElementIndex,
                 Action<Control> recycleElement)
             {
-                if (modelIndex < 0)
-                    throw new ArgumentOutOfRangeException(nameof(modelIndex));
+                if (index < 0)
+                    throw new ArgumentOutOfRangeException(nameof(index));
                 if (_elements is null || _elements.Count == 0)
                     return;
 
                 // Get the removal start and end index within the realized _elements collection.
-                var first = FirstModelIndex;
-                var last = LastModelIndex;
-                var startIndex = modelIndex - first;
-                var endIndex = (modelIndex + count) - first;
+                var first = FirstIndex;
+                var last = LastIndex;
+                var startIndex = index - first;
+                var endIndex = (index + count) - first;
 
                 if (endIndex < 0)
                 {
@@ -886,7 +886,7 @@ namespace Avalonia.Controls
                     // because we can't rely on it now to estimate element heights.
                     if (startIndex <= 0 && end < last)
                     {
-                        _firstIndex = first = modelIndex;
+                        _firstIndex = first = index;
                         _startUUnstable = true;
                     }
 
@@ -905,20 +905,20 @@ namespace Avalonia.Controls
             /// <summary>
             /// Recycles elements before a specific index.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new first element.</param>
+            /// <param name="index">The index in the source collection of new first element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int modelIndex, Action<Control> recycleElement)
+            public void RecycleElementsBefore(int index, Action<Control> recycleElement)
             {
-                if (modelIndex <= FirstModelIndex || _elements is null || _elements.Count == 0)
+                if (index <= FirstIndex || _elements is null || _elements.Count == 0)
                     return;
 
-                if (modelIndex > LastModelIndex)
+                if (index > LastIndex)
                 {
                     RecycleAllElements(recycleElement);
                 }
                 else
                 {
-                    var endIndex = modelIndex - FirstModelIndex;
+                    var endIndex = index - FirstIndex;
 
                     for (var i = 0; i < endIndex; ++i)
                     {
@@ -928,27 +928,27 @@ namespace Avalonia.Controls
 
                     _elements.RemoveRange(0, endIndex);
                     _sizes!.RemoveRange(0, endIndex);
-                    _firstIndex = modelIndex;
+                    _firstIndex = index;
                 }
             }
 
             /// <summary>
             /// Recycles elements after a specific index.
             /// </summary>
-            /// <param name="modelIndex">The index in the source collection of new last element.</param>
+            /// <param name="index">The index in the source collection of new last element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int modelIndex, Action<Control> recycleElement)
+            public void RecycleElementsAfter(int index, Action<Control> recycleElement)
             {
-                if (modelIndex >= LastModelIndex || _elements is null || _elements.Count == 0)
+                if (index >= LastIndex || _elements is null || _elements.Count == 0)
                     return;
 
-                if (modelIndex < FirstModelIndex)
+                if (index < FirstIndex)
                 {
                     RecycleAllElements(recycleElement);
                 }
                 else
                 {
-                    var startIndex = (modelIndex + 1) - FirstModelIndex;
+                    var startIndex = (index + 1) - FirstIndex;
                     var count = _elements.Count;
 
                     for (var i = startIndex; i < count; ++i)

From f371f1887051dbef75155c59c8cf846c5a3b5216 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 11:48:43 +0100
Subject: [PATCH 057/157] Use correct submodule commit.

Somehow got changed to an older commit.
---
 src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
index 491de981dd..5e498f8bcc 160000
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/xamlil.github
@@ -1 +1 @@
-Subproject commit 491de981dd4433ee58bc9540e2cd4a5d168f8168
+Subproject commit 5e498f8bcca403a34aff5efc825cbb4e12b7fa8e

From 9781a13256db78b92dfc120b33d603a9ac0d1832 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 15:33:27 +0100
Subject: [PATCH 058/157] Remove Smooth suffix.

`VirtualizingStackPanel` only does smooth scrolling now.
---
 ...StackPanelTests_Smooth.cs => VirtualizingStackPanelTests.cs} | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 rename tests/Avalonia.Controls.UnitTests/{VirtualizingStackPanelTests_Smooth.cs => VirtualizingStackPanelTests.cs} (99%)

diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
similarity index 99%
rename from tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
rename to tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 54b76b1931..5f21a7a882 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests_Smooth.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -14,7 +14,7 @@ using Xunit;
 
 namespace Avalonia.Controls.UnitTests
 {
-    public class VirtualizingStackPanelTests_Smooth
+    public class VirtualizingStackPanelTests
     {
         [Fact]
         public void Creates_Initial_Items()

From c55b7a9000c3d208bb870761ab059d43dec58de2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 16:36:45 +0100
Subject: [PATCH 059/157] Correctly handle control items being removed.

---
 src/Avalonia.Controls/VirtualizingPanel.cs    | 11 +++
 .../VirtualizingStackPanel.cs                 | 41 +++++---
 .../VirtualizingStackPanelTests.cs            | 97 ++++++++++++++++---
 3 files changed, 119 insertions(+), 30 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingPanel.cs b/src/Avalonia.Controls/VirtualizingPanel.cs
index 62918c3d35..7780843eb5 100644
--- a/src/Avalonia.Controls/VirtualizingPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingPanel.cs
@@ -154,6 +154,17 @@ namespace Avalonia.Controls
             Children.Insert(index, control);
         }
 
+        /// <summary>
+        /// Removes a child element from the <see cref="Panel.Children"/> collection.
+        /// </summary>
+        /// <param name="child">The child to remove/</param>
+        protected void RemoveInternalChild(Control child)
+        {
+            var itemsControl = EnsureItemsControl();
+            itemsControl.RemoveLogicalChild(child);
+            Children.Remove(child);
+        }
+
         /// <summary>
         /// Removes child elements from the <see cref="Panel.Children"/> collection.
         /// </summary>
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index a02d963ff8..dba45b1505 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -27,6 +27,7 @@ namespace Avalonia.Controls
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
         private readonly Action<Control> _recycleElement;
+        private readonly Action<Control> _recycleElementOnItemRemoved;
         private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
         private Control? _anchorElement;
@@ -41,6 +42,7 @@ namespace Avalonia.Controls
         public VirtualizingStackPanel()
         {
             _recycleElement = RecycleElement;
+            _recycleElementOnItemRemoved = RecycleElementOnItemRemoved;
             _updateElementIndex = UpdateElementIndex;
             EffectiveViewportChanged += OnEffectiveViewportChanged;
         }
@@ -68,13 +70,6 @@ namespace Avalonia.Controls
             try
             {
                 var items = Items;
-
-                if (items.Count == 0)
-                {
-                    RemoveInternalChildRange(0, Children.Count);
-                    return default;
-                }
-
                 var orientation = Orientation;
 
                 _realizedElements ??= new();
@@ -153,6 +148,8 @@ namespace Avalonia.Controls
 
         protected override void OnItemsChanged(IReadOnlyList<object?> items, NotifyCollectionChangedEventArgs e)
         {
+            InvalidateMeasure();
+
             if (_realizedElements is null)
                 return;
 
@@ -162,14 +159,12 @@ namespace Avalonia.Controls
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElement);
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    _realizedElements.RecycleAllElements(_recycleElement);
+                    _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
                     break;
             }
-
-            InvalidateMeasure();
         }
 
         protected override IInputElement? GetControl(NavigationDirection direction, IInputElement? from, bool wrap)
@@ -314,6 +309,7 @@ namespace Avalonia.Controls
             var (lastIndex, _) = _realizedElements.GetIndexAt(viewportEnd);
             var estimatedElementSize = -1.0;
             var itemCount = items?.Count ?? 0;
+            var maxIndex = Math.Max(itemCount - 1, 0);
 
             if (firstIndex == -1)
             {
@@ -331,8 +327,8 @@ namespace Avalonia.Controls
 
             return new MeasureViewport
             {
-                firstIndex = MathUtilities.Clamp(firstIndex, 0, itemCount - 1),
-                lastIndex = MathUtilities.Clamp(lastIndex, 0, itemCount - 1),
+                firstIndex = MathUtilities.Clamp(firstIndex, 0, maxIndex),
+                lastIndex = MathUtilities.Clamp(lastIndex, 0, maxIndex),
                 viewportUStart = viewportStart,
                 viewportUEnd = viewportEnd,
                 startU = firstIndexU,
@@ -468,7 +464,6 @@ namespace Avalonia.Controls
             var generator = ItemContainerGenerator!;
             var item = items[index];
 
-
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();
@@ -519,6 +514,24 @@ namespace Avalonia.Controls
             }
         }
 
+        private void RecycleElementOnItemRemoved(Control element)
+        {
+            Debug.Assert(ItemContainerGenerator is not null);
+
+            if (element.IsSet(ItemIsOwnContainerProperty))
+            {
+                RemoveInternalChild(element);
+            }
+            else
+            {
+                ItemContainerGenerator!.ClearItemContainer(element);
+                _recyclePool ??= new();
+                _recyclePool.Push(element);
+                element.IsVisible = false;
+                element.GetObservable(Visual.VisualParentProperty).Subscribe(x => { });
+            }
+        }
+
         private void UpdateElementIndex(Control element, int oldIndex, int newIndex)
         {
             Debug.Assert(ItemContainerGenerator is not null);
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 5f21a7a882..10cb5f8c6b 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -12,6 +12,8 @@ using Avalonia.UnitTests;
 using Avalonia.VisualTree;
 using Xunit;
 
+#nullable enable
+
 namespace Avalonia.Controls.UnitTests
 {
     public class VirtualizingStackPanelTests
@@ -20,7 +22,6 @@ namespace Avalonia.Controls.UnitTests
         public void Creates_Initial_Items()
         {
             using var app = App();
-
             var (target, scroll, itemsControl) = CreateTarget();
 
             Assert.Equal(1000, scroll.Extent.Height);
@@ -29,10 +30,35 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Scrolls_Down_One_Item()
+        public void Initializes_Initial_Control_Items()
+        {
+            using var app = App();
+            var items = Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10});
+            var (target, scroll, itemsControl) = CreateTarget(items: items, useItemTemplate: false);
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            AssertRealizedControlItems<Button>(target, itemsControl, 0, 10);
+        }
+
+        [Fact]
+        public void Creates_Reassigned_Items()
         {
             using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget(items: Array.Empty<object>());
+
+            Assert.Empty(itemsControl.GetRealizedContainers());
 
+            itemsControl.Items = new[] { "foo", "bar" };
+            Layout(target);
+
+            AssertRealizedItems(target, itemsControl, 0, 2);
+        }
+
+        [Fact]
+        public void Scrolls_Down_One_Item()
+        {
+            using var app = App();
             var (target, scroll, itemsControl) = CreateTarget();
 
             scroll.Offset = new Vector(0, 10);
@@ -45,7 +71,6 @@ namespace Avalonia.Controls.UnitTests
         public void Scrolls_Down_More_Than_A_Page()
         {
             using var app = App();
-
             var (target, scroll, itemsControl) = CreateTarget();
 
             scroll.Offset = new Vector(0, 200);
@@ -55,12 +80,11 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Creates_Elements_For_Inserted_Item()
+        public void Creates_Elements_On_Item_Insert()
         {
             using var app = App();
-
             var (target, _, itemsControl) = CreateTarget();
-            var items = (IList)itemsControl.Items;
+            var items = (IList)itemsControl.Items!;
 
             Assert.Equal(10, target.GetRealizedElements().Count);
 
@@ -88,12 +112,11 @@ namespace Avalonia.Controls.UnitTests
         }
 
         [Fact]
-        public void Updates_Elements_On_Removed_Row()
+        public void Updates_Elements_On_Item_Remove()
         {
             using var app = App();
-
             var (target, _, itemsControl) = CreateTarget();
-            var items = (IList)itemsControl.Items;
+            var items = (IList)itemsControl.Items!;
 
             Assert.Equal(10, target.GetRealizedElements().Count);
 
@@ -118,10 +141,26 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(elements, target.GetRealizedElements());
         }
 
+        [Fact]
+        public void Removes_Control_Items_From_Panel_On_Item_Remove()
+        {
+            using var app = App();
+            var items = new ObservableCollection<Button>(Enumerable.Range(0, 100).Select(x => new Button { Width = 25, Height = 10 }));
+            var (target, scroll, itemsControl) = CreateTarget(items: items, useItemTemplate: false);
+
+            Assert.Equal(1000, scroll.Extent.Height);
+
+            var removed = items[1];
+            items.RemoveAt(1);
+
+            Assert.Null(removed.Parent);
+            Assert.Null(removed.VisualParent);
+        }
+
         private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
         {
             return target.GetRealizedElements()
-                .Select(x => x is null ? -1 : itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+                .Select(x => x is null ? -1 : itemsControl.IndexFromContainer((Control)x))
                 .ToList();
         }
 
@@ -131,19 +170,43 @@ namespace Avalonia.Controls.UnitTests
             int firstIndex,
             int count)
         {
-            var childIndexes = target.GetLogicalChildren()
-                .Select(x => itemsControl.ItemContainerGenerator.IndexFromContainer((Control)x))
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(target, x.VisualParent));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(itemsControl, x.Parent));
+
+            var childIndexes = target.GetRealizedContainers()?
+                .Select(x => itemsControl.IndexFromContainer(x))
+                .Where(x => x >= 0)
+                .OrderBy(x => x)
+                .ToList();
+            Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
+        }
+
+        private static void AssertRealizedControlItems<TContainer>(
+            VirtualizingStackPanel target,
+            ItemsControl itemsControl,
+            int firstIndex,
+            int count)
+        {
+            Assert.All(target.GetRealizedContainers(), x => Assert.IsType<TContainer>(x));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(target, x.VisualParent));
+            Assert.All(target.GetRealizedContainers(), x => Assert.Same(itemsControl, x.Parent));
+
+            var childIndexes = target.GetRealizedContainers()?
+                .Select(x => itemsControl.IndexFromContainer(x))
                 .Where(x => x >= 0)
                 .OrderBy(x => x)
                 .ToList();
             Assert.Equal(Enumerable.Range(firstIndex, count), childIndexes);
         }
 
-        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(int itemCount = 100)
+        private static (VirtualizingStackPanel, ScrollViewer, ItemsControl) CreateTarget(
+            IEnumerable<object>? items = null,
+            bool useItemTemplate = true)
         {
-            var items = new ObservableCollection<string>(Enumerable.Range(0, itemCount).Select(x => $"Item {x}"));
             var target = new VirtualizingStackPanel();
-            
+
+            items ??= new ObservableCollection<string>(Enumerable.Range(0, 100).Select(x => $"Item {x}"));
+
             var presenter = new ItemsPresenter
             {
                 [~ItemsPresenter.ItemsPanelProperty] = new TemplateBinding(ItemsPresenter.ItemsPanelProperty),
@@ -160,9 +223,11 @@ namespace Avalonia.Controls.UnitTests
                 Items = items,
                 Template = new FuncControlTemplate<ItemsControl>((_, _) => scroll),
                 ItemsPanel = new FuncTemplate<Panel>(() => target),
-                ItemTemplate = new FuncDataTemplate<string>((x, _) => new Canvas { Width = 100, Height = 10 }),
             };
 
+            if (useItemTemplate)
+                itemsControl.ItemTemplate = new FuncDataTemplate<object>((x, _) => new Canvas { Width = 100, Height = 10 });
+
             var root = new TestRoot(true, itemsControl);
             root.ClientSize = new(100, 100);
             root.LayoutManager.ExecuteInitialLayoutPass();

From 76b51cf2a90e85338bb6cefdf1f3551b1882862a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 12 Dec 2022 17:15:56 +0100
Subject: [PATCH 060/157] Fix property name.

---
 src/Avalonia.Controls/ItemsControl.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index 4e89c2da17..f413cb4972 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -65,7 +65,7 @@ namespace Avalonia.Controls
         /// Defines the <see cref="ItemsView"/> property.
         /// </summary>
         public static readonly DirectProperty<ItemsControl, ItemsSourceView> ItemsViewProperty =
-            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(Items), o => o.ItemsView);
+            AvaloniaProperty.RegisterDirect<ItemsControl, ItemsSourceView>(nameof(ItemsView), o => o.ItemsView);
 
         /// <summary>
         /// Defines the <see cref="DisplayMemberBinding" /> property

From 54bc9ddeeb87cfd3ad0164728b52633a9bba7b37 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 11:03:03 +0100
Subject: [PATCH 061/157] Fix adorners in DevTools.

---
 .../Diagnostics/Views/TreePageView.xaml       |  4 ++-
 .../Diagnostics/Views/TreePageView.xaml.cs    | 26 -------------------
 2 files changed, 3 insertions(+), 27 deletions(-)

diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
index 36bb880a14..3ca3d0b60e 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml
@@ -11,7 +11,9 @@
       <TreeView.DataTemplates>
         <TreeDataTemplate DataType="vm:TreeNode"
                           ItemsSource="{Binding Children}">
-          <StackPanel Orientation="Horizontal" Spacing="8">
+          <StackPanel Orientation="Horizontal" Spacing="8"
+                      PointerEntered="AddAdorner"
+                      PointerExited="RemoveAdorner">
             <TextBlock Text="{Binding Type}" FontWeight="{Binding FontWeight}"/>
             <TextBlock Text="{Binding Classes}"/>
             <TextBlock Foreground="Gray" Text="{Binding ElementName}"/>
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
index d8feb579f0..1a4bb6170a 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/TreePageView.xaml.cs
@@ -21,7 +21,6 @@ namespace Avalonia.Diagnostics.Views
         {
             InitializeComponent();
             _tree = this.GetControl<TreeView>("tree");
-            ////_tree.ItemContainerGenerator.Index!.Materialized += TreeViewItemMaterialized;
 
             _adorner = new Panel
             {
@@ -102,30 +101,5 @@ namespace Avalonia.Diagnostics.Views
         {
             AvaloniaXamlLoader.Load(this);
         }
-
-        ////private void TreeViewItemMaterialized(object? sender, ItemContainerEventArgs e)
-        ////{
-        ////    var item = (TreeViewItem)e.Containers[0].ContainerControl;
-        ////    item.TemplateApplied += TreeViewItemTemplateApplied;
-        ////}
-
-        private void TreeViewItemTemplateApplied(object? sender, TemplateAppliedEventArgs e)
-        {
-            var item = (TreeViewItem)sender!;
-
-            // This depends on the default tree item template.
-            // We want to handle events in the item header but exclude events coming from children.
-            var header = item.FindDescendantOfType<Border>();
-
-            Debug.Assert(header != null);
-
-            if (header != null)
-            {
-                header.PointerEntered += AddAdorner;
-                header.PointerExited += RemoveAdorner;
-            }
-
-            item.TemplateApplied -= TreeViewItemTemplateApplied;
-        }
     }
 }

From 039fb905ad6b18ab939e5863b00f4ebed9939d4d Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 13:04:32 +0100
Subject: [PATCH 062/157] Handle item move and replace.

---
 .../VirtualizingStackPanel.cs                 |  5 ++
 .../VirtualizingStackPanelTests.cs            | 58 +++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index dba45b1505..6dec8c6327 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -161,6 +161,11 @@ namespace Avalonia.Controls
                 case NotifyCollectionChangedAction.Remove:
                     _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
                     break;
+                case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
+                    _realizedElements.ItemsRemoved(e.OldStartingIndex, e.OldItems!.Count, _updateElementIndex, _recycleElementOnItemRemoved);
+                    _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
+                    break;
                 case NotifyCollectionChangedAction.Reset:
                     _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
                     break;
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index 10cb5f8c6b..c20d4fa41a 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -141,6 +141,64 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(elements, target.GetRealizedElements());
         }
 
+        [Fact]
+        public void Updates_Elements_On_Item_Replace()
+        {
+            using var app = App();
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (ObservableCollection<string>)itemsControl.Items!;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toReplace = target.GetRealizedElements().ElementAt(2);
+            items[2] = "new";
+
+            // Container being replaced should have been recycled.
+            Assert.DoesNotContain(toReplace, target.GetRealizedElements());
+            Assert.False(toReplace!.IsVisible);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements at old position and space inserted at new position.
+            Assert.Equal(new[] { 0, 1, -1, 3, 4, 5, 6, 7, 8, 9 }, indexes);
+
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout the missing container should have been created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+        }
+
+        [Fact]
+        public void Updates_Elements_On_Item_Move()
+        {
+            using var app = App();
+            var (target, _, itemsControl) = CreateTarget();
+            var items = (ObservableCollection<string>)itemsControl.Items!;
+
+            Assert.Equal(10, target.GetRealizedElements().Count);
+
+            var toMove = target.GetRealizedElements().ElementAt(2);
+            items.Move(2, 6);
+
+            // Container being moved should have been recycled.
+            Assert.DoesNotContain(toMove, target.GetRealizedElements());
+            Assert.False(toMove!.IsVisible);
+
+            var indexes = GetRealizedIndexes(target, itemsControl);
+
+            // Item removed from realized elements at old position and space inserted at new position.
+            Assert.Equal(new[] { 0, 1, 2, 3, 4, 5, -1, 7, 8, 9 }, indexes);
+
+            Layout(target);
+
+            indexes = GetRealizedIndexes(target, itemsControl);
+
+            // After layout the missing container should have been created.
+            Assert.Equal(Enumerable.Range(0, 10), indexes);
+        }
+
         [Fact]
         public void Removes_Control_Items_From_Panel_On_Item_Remove()
         {

From 17f7541fdd39943e705975d766be480a558117b7 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 14:34:32 +0100
Subject: [PATCH 063/157] Fix selection in combination with move.

---
 .../Presenters/PanelContainerGenerator.cs     |  7 +-
 .../Selection/SelectionModel.cs               |  1 +
 .../Selection/SelectionNodeBase.cs            |  1 +
 .../Primitives/SelectingItemsControlTests.cs  | 72 +++++++++++++++++++
 .../Selection/SelectionModelTests_Multiple.cs | 50 +++++++++++++
 .../Selection/SelectionModelTests_Single.cs   | 46 ++++++++++++
 6 files changed, 173 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
index 1c94c29a35..a2df8c3e5f 100644
--- a/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
+++ b/src/Avalonia.Controls/Presenters/PanelContainerGenerator.cs
@@ -81,9 +81,11 @@ namespace Avalonia.Controls.Presenters
             {
                 for (var i = 0; i < count; ++i)
                 {
-                    var c = children[i];
+                    var c = children[index + i];
                     if (!c.IsSet(ItemIsOwnContainerProperty))
                         itemsControl.RemoveLogicalChild(children[i + index]);
+                    else
+                        generator.ClearItemContainer(c);
                 }
 
                 children.RemoveRange(index, count);
@@ -103,9 +105,6 @@ namespace Avalonia.Controls.Presenters
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     break;
                 case NotifyCollectionChangedAction.Replace:
-                    Remove(e.OldStartingIndex, e.OldItems!.Count);
-                    Add(e.NewStartingIndex, e.NewItems!);
-                    break;
                 case NotifyCollectionChangedAction.Move:
                     Remove(e.OldStartingIndex, e.OldItems!.Count);
                     Add(e.NewStartingIndex, e.NewItems!);
diff --git a/src/Avalonia.Controls/Selection/SelectionModel.cs b/src/Avalonia.Controls/Selection/SelectionModel.cs
index 9bbddfcbb2..affe762ea7 100644
--- a/src/Avalonia.Controls/Selection/SelectionModel.cs
+++ b/src/Avalonia.Controls/Selection/SelectionModel.cs
@@ -439,6 +439,7 @@ namespace Avalonia.Controls.Selection
 
             if ((e.Action == NotifyCollectionChangedAction.Remove && e.OldStartingIndex <= oldSelectedIndex) ||
                 (e.Action == NotifyCollectionChangedAction.Replace && e.OldStartingIndex == oldSelectedIndex) ||
+                (e.Action == NotifyCollectionChangedAction.Move && e.OldStartingIndex == oldSelectedIndex) ||
                 e.Action == NotifyCollectionChangedAction.Reset)
             {
                 RaisePropertyChanged(nameof(SelectedItem));
diff --git a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
index 01b89325af..69a651aca6 100644
--- a/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
+++ b/src/Avalonia.Controls/Selection/SelectionNodeBase.cs
@@ -256,6 +256,7 @@ namespace Avalonia.Controls.Selection
                         break;
                     }
                 case NotifyCollectionChangedAction.Replace:
+                case NotifyCollectionChangedAction.Move:
                     {
                         var removeChange = OnItemsRemoved(e.OldStartingIndex, e.OldItems!);
                         var addChange = OnItemsAdded(e.NewStartingIndex, e.NewItems!);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index dbea9f79b8..1775d7ef70 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -637,6 +637,78 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.False(items.Single().IsSelected);
         }
 
+        [Fact]
+        public void Replacing_Selected_Item_Should_Clear_Selection()
+        {
+            var items = new AvaloniaList<Item>
+            {
+                new Item(),
+                new Item(),
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            Prepare(target);
+            target.SelectedIndex = 1;
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+
+            SelectionChangedEventArgs receivedArgs = null;
+
+            target.SelectionChanged += (_, args) => receivedArgs = args;
+
+            var removed = items[1];
+            items[1] = new Item();
+
+            Assert.Null(target.SelectedItem);
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.NotNull(receivedArgs);
+            Assert.Empty(receivedArgs.AddedItems);
+            Assert.Equal(new[] { removed }, receivedArgs.RemovedItems);
+            Assert.All(items, x => Assert.False(x.IsSelected));
+        }
+
+        [Fact]
+        public void Moving_Selected_Item_Should_Clear_Selection()
+        {
+            var items = new AvaloniaList<Item>
+            {
+                new Item(),
+                new Item(),
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            Prepare(target);
+            target.SelectedIndex = 1;
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+
+            SelectionChangedEventArgs receivedArgs = null;
+
+            target.SelectionChanged += (_, args) => receivedArgs = args;
+
+            var removed = items[1];
+            items.Move(1, 0);
+
+            Assert.Null(target.SelectedItem);
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.NotNull(receivedArgs);
+            Assert.Empty(receivedArgs.AddedItems);
+            Assert.Equal(new[] { removed }, receivedArgs.RemovedItems);
+            Assert.All(items, x => Assert.False(x.IsSelected));
+        }
+
         [Fact]
         public void Resetting_Items_Collection_Should_Clear_Selection()
         {
diff --git a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
index 68bdbe51e8..dbbff91fcc 100644
--- a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Multiple.cs
@@ -1259,6 +1259,56 @@ namespace Avalonia.Controls.UnitTests.Selection
                 Assert.Equal(0, indexesChangedRaised);
             }
 
+            [Fact]
+            public void Moving_Selected_Item_Updates_State()
+            {
+                var target = CreateTarget();
+                var data = (AvaloniaList<string>)target.Source!;
+                var selectionChangedRaised = 0;
+                var selectedIndexRaised = 0;
+                var selectedItemRaised = 0;
+                var indexesChangedRaised = 0;
+
+                target.Source = data;
+                target.SelectRange(1, 4);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    if (e.PropertyName == nameof(target.SelectedIndex))
+                    {
+                        ++selectedIndexRaised;
+                    }
+
+                    if (e.PropertyName == nameof(target.SelectedItem))
+                    {
+                        ++selectedItemRaised;
+                    }
+                };
+
+                target.IndexesChanged += (s, e) => ++indexesChangedRaised;
+
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.DeselectedIndexes);
+                    Assert.Equal(new[] { "bar" }, e.DeselectedItems);
+                    Assert.Empty(e.SelectedIndexes);
+                    Assert.Empty(e.SelectedItems);
+                    ++selectionChangedRaised;
+                };
+
+                data.Move(1, 0);
+
+                Assert.Equal(2, target.SelectedIndex);
+                Assert.Equal(new[] { 2, 3, 4 }, target.SelectedIndexes);
+                Assert.Equal("baz", target.SelectedItem);
+                Assert.Equal(new[] { "baz", "qux", "quux" }, target.SelectedItems);
+                Assert.Equal(2, target.AnchorIndex);
+                Assert.Equal(1, selectionChangedRaised);
+                Assert.Equal(1, selectedIndexRaised);
+                Assert.Equal(1, selectedItemRaised);
+                Assert.Equal(0, indexesChangedRaised);
+            }
+
             [Fact]
             public void Resetting_Source_Updates_State()
             {
diff --git a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
index 668af3b5d7..c5370f0749 100644
--- a/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
+++ b/tests/Avalonia.Controls.UnitTests/Selection/SelectionModelTests_Single.cs
@@ -1079,6 +1079,52 @@ namespace Avalonia.Controls.UnitTests.Selection
                 Assert.Equal(1, selectedItemRaised);
             }
 
+            [Fact]
+            public void Moving_Selected_Item_Updates_State()
+            {
+                var target = CreateTarget();
+                var data = (AvaloniaList<string>)target.Source!;
+                var selectionChangedRaised = 0;
+                var selectedIndexRaised = 0;
+                var selectedItemRaised = 0;
+
+                target.Source = data;
+                target.Select(1);
+
+                target.PropertyChanged += (s, e) =>
+                {
+                    if (e.PropertyName == nameof(target.SelectedIndex))
+                    {
+                        ++selectedIndexRaised;
+                    }
+
+                    if (e.PropertyName == nameof(target.SelectedItem))
+                    {
+                        ++selectedItemRaised;
+                    }
+                };
+
+                target.SelectionChanged += (s, e) =>
+                {
+                    Assert.Empty(e.DeselectedIndexes);
+                    Assert.Equal(new[] { "bar" }, e.DeselectedItems);
+                    Assert.Empty(e.SelectedIndexes);
+                    Assert.Empty(e.SelectedItems);
+                    ++selectionChangedRaised;
+                };
+
+                data.Move(1, 0);
+
+                Assert.Equal(-1, target.SelectedIndex);
+                Assert.Empty(target.SelectedIndexes);
+                Assert.Null(target.SelectedItem);
+                Assert.Empty(target.SelectedItems);
+                Assert.Equal(-1, target.AnchorIndex);
+                Assert.Equal(1, selectionChangedRaised);
+                Assert.Equal(1, selectedIndexRaised);
+                Assert.Equal(1, selectedItemRaised);
+            }
+
             [Fact]
             public void Resetting_Source_Updates_State()
             {

From 2b02afce36deb0747aca8b1a331fab5d99a984fb Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 13 Dec 2022 17:43:05 +0100
Subject: [PATCH 064/157] Added ItemsPanelRoot for WPF/UWP compat.

---
 src/Avalonia.Controls/ItemsControl.cs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/Avalonia.Controls/ItemsControl.cs b/src/Avalonia.Controls/ItemsControl.cs
index f413cb4972..d19a04eb21 100644
--- a/src/Avalonia.Controls/ItemsControl.cs
+++ b/src/Avalonia.Controls/ItemsControl.cs
@@ -163,6 +163,11 @@ namespace Avalonia.Controls
         /// </summary>
         public ItemsPresenter? Presenter { get; private set; }
 
+        /// <summary>
+        /// Gets the <see cref="Panel"/> specified by <see cref="ItemsPanel"/>.
+        /// </summary>
+        public Panel? ItemsPanelRoot => Presenter?.Panel;
+
         /// <summary>
         /// Gets a standardized view over <see cref="Items"/>.
         /// </summary>

From 7eb95255cb1055c7d981b6ff20b86a014c9dc570 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 15 Dec 2022 14:16:04 +0100
Subject: [PATCH 065/157] Don't mark all owned windows as dialogs.

This was preventing owner windows of non-modal dialogs from receiving key window status, meaning that input was broken in combination with embedding (Avalonia controls did work however because the routing was carried out internal to Avalonia).
---
 native/Avalonia.Native/src/OSX/WindowImpl.mm | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/native/Avalonia.Native/src/OSX/WindowImpl.mm b/native/Avalonia.Native/src/OSX/WindowImpl.mm
index b6dacb6ce4..bbf419bccd 100644
--- a/native/Avalonia.Native/src/OSX/WindowImpl.mm
+++ b/native/Avalonia.Native/src/OSX/WindowImpl.mm
@@ -63,7 +63,7 @@ HRESULT WindowImpl::Show(bool activate, bool isDialog) {
     START_COM_CALL;
 
     @autoreleasepool {
-        _isDialog = isDialog || _parent != nullptr;
+        _isDialog = isDialog;
 
         WindowBaseImpl::Show(activate, isDialog);
 

From 102b1b351bce7a75be28c51ac70e19d50f786126 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Thu, 15 Dec 2022 14:17:19 +0100
Subject: [PATCH 066/157] Add null check,

Customer was seeing a crash in this method, don't have a repro but other uses of `_parent` are surrounded by a null check so this makes sense I think.
---
 native/Avalonia.Native/src/OSX/AvnWindow.mm | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/native/Avalonia.Native/src/OSX/AvnWindow.mm b/native/Avalonia.Native/src/OSX/AvnWindow.mm
index 6611dcc73f..42c500716c 100644
--- a/native/Avalonia.Native/src/OSX/AvnWindow.mm
+++ b/native/Avalonia.Native/src/OSX/AvnWindow.mm
@@ -281,6 +281,9 @@
 
 - (void)windowDidBecomeKey:(NSNotification *_Nonnull)notification
 {
+    if (_parent == nullptr)
+        return;
+        
     _parent->BringToFront();
     
     dispatch_async(dispatch_get_main_queue(), ^{

From 872eca05b2df322077c273be1922201381520e12 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 16 Dec 2022 09:01:15 +0100
Subject: [PATCH 067/157] Disable minimize button on owned windows again.

7eb95255c regressed disabling the minimize button on owned windows. Split what was previously `IsDialog` into two flags: `IsModal` and `IsOwned` and use `IsOwned` to control the disabled state of the minimize button.
---
 native/Avalonia.Native/src/OSX/AvnWindow.mm    |  2 +-
 .../Avalonia.Native/src/OSX/WindowBaseImpl.h   |  2 +-
 .../Avalonia.Native/src/OSX/WindowBaseImpl.mm  |  2 +-
 native/Avalonia.Native/src/OSX/WindowImpl.h    |  6 ++++--
 native/Avalonia.Native/src/OSX/WindowImpl.mm   | 18 +++++++++++-------
 5 files changed, 18 insertions(+), 12 deletions(-)

diff --git a/native/Avalonia.Native/src/OSX/AvnWindow.mm b/native/Avalonia.Native/src/OSX/AvnWindow.mm
index 42c500716c..d3b7b4ede6 100644
--- a/native/Avalonia.Native/src/OSX/AvnWindow.mm
+++ b/native/Avalonia.Native/src/OSX/AvnWindow.mm
@@ -44,7 +44,7 @@
 
 -(bool) isDialog
 {
-    return _parent->IsDialog();
+    return _parent->IsModal();
 }
 
 -(double) getExtendedTitleBarHeight
diff --git a/native/Avalonia.Native/src/OSX/WindowBaseImpl.h b/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
index 7fb002e54f..bb8d5fae75 100644
--- a/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
+++ b/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
@@ -96,7 +96,7 @@ BEGIN_INTERFACE_MAP()
             IAvnClipboard *clipboard, IAvnDndResultCallback *cb,
             void *sourceHandle) override;
 
-    virtual bool IsDialog();
+    virtual bool IsModal();
 
     id<AvnWindowProtocol> GetWindowProtocol ();
                            
diff --git a/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm b/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
index 9946ad9b10..9650290fbb 100644
--- a/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
+++ b/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
@@ -542,7 +542,7 @@ HRESULT WindowBaseImpl::BeginDragAndDropOperation(AvnDragDropEffects effects, Av
     return S_OK;
 }
 
-bool WindowBaseImpl::IsDialog() {
+bool WindowBaseImpl::IsModal() {
     return false;
 }
 
diff --git a/native/Avalonia.Native/src/OSX/WindowImpl.h b/native/Avalonia.Native/src/OSX/WindowImpl.h
index b4b1d4e70b..3861aaf170 100644
--- a/native/Avalonia.Native/src/OSX/WindowImpl.h
+++ b/native/Avalonia.Native/src/OSX/WindowImpl.h
@@ -23,7 +23,7 @@ private:
     NSRect _preZoomSize;
     bool _transitioningWindowState;
     bool _isClientAreaExtended;
-    bool _isDialog;
+    bool _isModal;
     WindowImpl* _parent;
     std::list<WindowImpl*> _children;
     AvnExtendClientAreaChromeHints _extendClientHints;
@@ -91,7 +91,9 @@ BEGIN_INTERFACE_MAP()
 
     virtual HRESULT SetWindowState (AvnWindowState state) override;
 
-    virtual bool IsDialog() override;
+    virtual bool IsModal() override;
+    
+    bool IsOwned();
     
     virtual void BringToFront () override;
     
diff --git a/native/Avalonia.Native/src/OSX/WindowImpl.mm b/native/Avalonia.Native/src/OSX/WindowImpl.mm
index bbf419bccd..f345043f61 100644
--- a/native/Avalonia.Native/src/OSX/WindowImpl.mm
+++ b/native/Avalonia.Native/src/OSX/WindowImpl.mm
@@ -63,7 +63,7 @@ HRESULT WindowImpl::Show(bool activate, bool isDialog) {
     START_COM_CALL;
 
     @autoreleasepool {
-        _isDialog = isDialog;
+        _isModal = isDialog;
 
         WindowBaseImpl::Show(activate, isDialog);
 
@@ -97,7 +97,7 @@ HRESULT WindowImpl::SetParent(IAvnWindow *parent) {
         
         _parent = cparent;
 
-        _isDialog = _parent != nullptr;
+        _isModal = _parent != nullptr;
         
         if(_parent != nullptr && Window != nullptr){
             // If one tries to show a child window with a minimized parent window, then the parent window will be
@@ -123,7 +123,7 @@ void WindowImpl::BringToFront()
     {
         if ([Window isVisible] && ![Window isMiniaturized])
         {
-            if(IsDialog())
+            if(IsModal())
             {
                 Activate();
             }
@@ -150,7 +150,7 @@ bool WindowImpl::CanBecomeKeyWindow()
 {
     for(auto iterator = _children.begin(); iterator != _children.end(); iterator++)
     {
-        if((*iterator)->IsDialog())
+        if((*iterator)->IsModal())
         {
             return false;
         }
@@ -569,8 +569,12 @@ HRESULT WindowImpl::SetWindowState(AvnWindowState state) {
     }
 }
 
-bool WindowImpl::IsDialog() {
-    return _isDialog;
+bool WindowImpl::IsModal() {
+    return _isModal;
+}
+
+bool WindowImpl::IsOwned() {
+    return _parent != nullptr;
 }
 
 NSWindowStyleMask WindowImpl::GetStyle() {
@@ -599,7 +603,7 @@ NSWindowStyleMask WindowImpl::GetStyle() {
             break;
     }
 
-    if (!IsDialog()) {
+    if (!IsOwned()) {
         s |= NSWindowStyleMaskMiniaturizable;
     }
 

From 59d7874b1dc397987c65ac159a40dfbccfe93679 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Tue, 20 Dec 2022 21:42:36 -0500
Subject: [PATCH 068/157] Replace System.Reactive with internal extensions

---
 build/Base.props                              |   1 +
 src/Avalonia.Base/Animation/Animation.cs      |   3 +-
 .../Animation/AnimationInstance`1.cs          |   5 +-
 .../Animation/AnimatorKeyFrame.cs             |   2 +-
 .../Animation/Animators/Animator`1.cs         |   2 -
 .../Animation/Animators/ColorAnimator.cs      |   2 +-
 .../Animation/Animators/TransformAnimator.cs  |   2 +-
 src/Avalonia.Base/Animation/Clock.cs          |   1 +
 src/Avalonia.Base/Animation/CrossFade.cs      |   4 +-
 src/Avalonia.Base/Avalonia.Base.csproj        |   7 +-
 src/Avalonia.Base/AvaloniaObjectExtensions.cs | 176 +++-----
 src/Avalonia.Base/AvaloniaProperty`1.cs       |   6 +-
 src/Avalonia.Base/ClassBindingManager.cs      |   1 +
 .../Collections/AvaloniaListExtensions.cs     |   2 +-
 .../NotifyCollectionChangedExtensions.cs      |   1 -
 .../Controls/NameScopeLocator.cs              |   2 +-
 src/Avalonia.Base/Data/BindingOperations.cs   |  11 +-
 .../Data/Core/AvaloniaPropertyAccessorNode.cs |   1 -
 .../Data/Core/BindingExpression.cs            |   6 +-
 .../Data/Core/ExpressionObserver.cs           |  17 +-
 .../Data/Core/IndexerNodeBase.cs              |  61 ++-
 .../Core/Plugins/ObservableStreamPlugin.cs    |  65 +--
 .../Data/Core/Plugins/TaskStreamPlugin.cs     |   5 +-
 src/Avalonia.Base/Data/Core/StreamNode.cs     |   2 +-
 src/Avalonia.Base/Data/IndexerBinding.cs      |   9 +-
 src/Avalonia.Base/Data/IndexerDescriptor.cs   |   5 +-
 src/Avalonia.Base/Data/InstancedBinding.cs    |  52 +--
 src/Avalonia.Base/Input/Gestures.cs           |   1 +
 src/Avalonia.Base/Input/InputElement.cs       |   1 +
 src/Avalonia.Base/Input/InputManager.cs       |   8 +-
 src/Avalonia.Base/Input/MouseDevice.cs        |   1 +
 .../Input/TextInput/InputMethodManager.cs     |   2 +-
 .../Interactivity/InteractiveExtensions.cs    |   3 +-
 .../Interactivity/RoutedEvent.cs              |   6 +-
 src/Avalonia.Base/Layout/Layoutable.cs        |   2 +-
 src/Avalonia.Base/Media/Brush.cs              |   1 +
 src/Avalonia.Base/Media/DashStyle.cs          |   1 +
 .../Media/ExperimentalAcrylicMaterial.cs      |   1 +
 src/Avalonia.Base/Media/Geometry.cs           |   1 +
 src/Avalonia.Base/Media/GradientBrush.cs      |   1 +
 src/Avalonia.Base/Media/MatrixTransform.cs    |   1 +
 src/Avalonia.Base/Media/RotateTransform.cs    |   1 +
 src/Avalonia.Base/Media/ScaleTransform.cs     |   1 +
 src/Avalonia.Base/Media/SkewTransform.cs      |   1 +
 src/Avalonia.Base/Media/TranslateTransform.cs |   1 +
 .../PropertyStore/BindingEntryBase.cs         |   2 +-
 .../Reactive/AnonymousObserver.cs             |  62 +++
 src/Avalonia.Base/Reactive/CombinedSubject.cs |  23 +
 .../Reactive/CompositeDisposable.cs           | 427 ++++++++++++++++++
 src/Avalonia.Base/Reactive/Disposable.cs      |  98 ++++
 src/Avalonia.Base/Reactive/DisposableMixin.cs |  37 ++
 .../Reactive/IAvaloniaSubject.cs              |   8 +
 .../Reactive/LightweightObservableBase.cs     |   8 +-
 .../Reactive/LightweightSubject.cs            |  30 ++
 src/Avalonia.Base/Reactive/Observable.cs      | 238 ++++++++++
 src/Avalonia.Base/Reactive/ObservableEx.cs    |  37 --
 .../Reactive/Operators/CombineLatest.cs       | 374 +++++++++++++++
 src/Avalonia.Base/Reactive/Operators/Sink.cs  | 109 +++++
 .../Reactive/Operators/Switch.cs              | 144 ++++++
 .../PlatformRenderInterfaceContextManager.cs  |   2 +-
 .../Rendering/SceneGraph/VisualNode.cs        |   2 +-
 .../Rendering/UiThreadRenderTimer.cs          |   2 +-
 src/Avalonia.Base/Styling/StyleInstance.cs    |   6 +-
 .../Threading/DispatcherTimer.cs              |   2 +-
 .../Utilities/IWeakSubscriber.cs              |  18 -
 src/Avalonia.Base/Utilities/WeakObservable.cs |  60 ---
 src/Avalonia.Base/Visual.cs                   |  75 +--
 .../Avalonia.Controls.ColorPicker.csproj      |   1 -
 .../ColorSpectrum/ColorSpectrum.cs            |   1 +
 .../Avalonia.Controls.DataGrid.csproj         |   1 -
 src/Avalonia.Controls.DataGrid/DataGrid.cs    |   1 +
 .../DataGridBoundColumn.cs                    |   5 -
 src/Avalonia.Controls.DataGrid/DataGridRow.cs |  11 +-
 .../DataGridRowGroupHeader.cs                 |   2 +-
 .../Utils/CellEditBinding.cs                  |  14 +-
 src/Avalonia.Controls/Application.cs          |   3 -
 .../AutoCompleteBox/AutoCompleteBox.cs        |   2 +-
 .../Avalonia.Controls.csproj                  |   1 -
 src/Avalonia.Controls/Button.cs               |   1 +
 src/Avalonia.Controls/ButtonSpinner.cs        |   3 +-
 .../CalendarDatePicker/CalendarDatePicker.cs  |   2 +-
 src/Avalonia.Controls/Canvas.cs               |   3 -
 .../Chrome/CaptionButtons.cs                  |  11 +-
 src/Avalonia.Controls/Chrome/TitleBar.cs      |   4 +-
 src/Avalonia.Controls/ComboBox.cs             |   2 +-
 src/Avalonia.Controls/ComboBoxItem.cs         |  13 +-
 src/Avalonia.Controls/ContextMenu.cs          |   1 +
 src/Avalonia.Controls/ControlExtensions.cs    |   5 +-
 src/Avalonia.Controls/DataValidationErrors.cs |   2 +-
 src/Avalonia.Controls/DefinitionBase.cs       |   1 +
 .../ExperimentalAcrylicBorder.cs              |   1 +
 src/Avalonia.Controls/Flyouts/FlyoutBase.cs   |   1 +
 src/Avalonia.Controls/HotkeyManager.cs        |   1 +
 .../LayoutTransformControl.cs                 |   6 +-
 src/Avalonia.Controls/MenuItem.cs             |   7 +-
 .../Mixins/DisposableMixin.cs                 |  38 --
 .../Mixins/SelectableMixin.cs                 |   2 +-
 src/Avalonia.Controls/NativeMenu.Export.cs    |   3 +-
 src/Avalonia.Controls/NativeMenuBar.cs        |   1 +
 src/Avalonia.Controls/NativeMenuItem.cs       |   1 +
 .../Notifications/NotificationCard.cs         |  41 +-
 .../WindowNotificationManager.cs              |   2 +-
 .../NumericUpDown/NumericUpDown.cs            |   1 +
 src/Avalonia.Controls/Panel.cs                |   1 +
 .../Platform/DefaultMenuInteractionHandler.cs |   2 +-
 .../Platform/InProcessDragSource.cs           |  28 +-
 .../Platform/PlatformManager.cs               |   2 +-
 .../Presenters/CarouselPresenter.cs           |   2 +-
 .../Presenters/ItemVirtualizer.cs             |   2 +-
 .../Presenters/ScrollContentPresenter.cs      |   4 +-
 .../Primitives/AccessText.cs                  |   3 +-
 .../Primitives/AdornerLayer.cs                |   1 +
 .../Primitives/OverlayPopupHost.cs            |   2 +-
 src/Avalonia.Controls/Primitives/Popup.cs     |   2 +-
 src/Avalonia.Controls/ProgressBar.cs          |   1 +
 .../PullToRefresh/RefreshContainer.cs         |   1 +
 .../PullToRefresh/RefreshVisualizer.cs        |   2 +-
 src/Avalonia.Controls/RadioButton.cs          |   1 +
 .../Repeater/ViewportManager.cs               |   8 -
 src/Avalonia.Controls/ScrollViewer.cs         |   2 +-
 src/Avalonia.Controls/Shapes/Shape.cs         |   1 +
 src/Avalonia.Controls/Spinner.cs              |   1 +
 .../SplitButton/SplitButton.cs                |   1 +
 src/Avalonia.Controls/SplitView.cs            |   1 +
 .../Templates/FuncDataTemplate.cs             |   2 +-
 src/Avalonia.Controls/TextBox.cs              |   2 +-
 src/Avalonia.Controls/ToolTip.cs              |   1 +
 src/Avalonia.Controls/TopLevel.cs             |   2 +-
 src/Avalonia.Controls/TrayIcon.cs             |   2 +-
 src/Avalonia.Controls/TreeView.cs             |   2 +-
 src/Avalonia.Controls/Utils/AncestorFinder.cs |  18 +-
 src/Avalonia.Controls/Window.cs               |   4 +-
 src/Avalonia.Controls/WindowBase.cs           |   5 -
 .../Avalonia.DesignerSupport.csproj           |   1 -
 src/Avalonia.DesignerSupport/Remote/Stubs.cs  |   2 +-
 .../Diagnostics/DevTools.cs                   |   4 +-
 .../Diagnostics/ViewModels/LogicalTreeNode.cs |   2 +-
 .../Diagnostics/ViewModels/VisualTreeNode.cs  |   2 +-
 .../Internal/ManagedFileChooserViewModel.cs   |   9 +-
 .../DBusIme/Fcitx/FcitxX11TextInputMethod.cs  |   1 -
 src/Avalonia.FreeDesktop/DBusMenuExporter.cs  |   2 +-
 src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs  |   2 +-
 .../LinuxMountedVolumeInfoListener.cs         |  22 +-
 .../AvaloniaHeadlessPlatform.cs               |   2 +-
 .../HeadlessPlatformThreadingInterface.cs     |   2 +-
 src/Avalonia.Native/IAvnMenu.cs               |   2 +-
 src/Avalonia.Native/IAvnMenuItem.cs           |   2 +-
 .../MacOSMountedVolumeInfoProvider.cs         |  21 +-
 src/Avalonia.OpenGL/Egl/EglContext.cs         |   2 +-
 src/Avalonia.OpenGL/Egl/EglDisplay.cs         |   2 +-
 src/Avalonia.OpenGL/Egl/EglDisplayUtils.cs    |   3 +-
 src/Avalonia.ReactiveUI/Attributes.cs         |   1 -
 src/Avalonia.ReactiveUI/AutoSuspendHelper.cs  |   2 +-
 .../AvaloniaObjectReactiveExtensions.cs       | 110 +++++
 .../AvaloniaScheduler.cs                      |   3 +-
 .../Avalonia.Themes.Fluent.csproj             |   1 -
 .../Avalonia.Themes.Simple.csproj             |   1 -
 src/Avalonia.X11/Glx/GlxContext.cs            |   2 +-
 src/Avalonia.X11/X11Window.cs                 |   1 +
 .../Avalonia.Markup.Xaml.csproj               |   1 -
 .../FindVisualAncestorNode.cs                 |   1 +
 .../ObservableStreamPlugin.cs                 |   2 +-
 .../PropertyInfoAccessorFactory.cs            |   1 +
 .../CompiledBindings/TaskStreamPlugin.cs      |   5 +-
 .../Templates/TemplateContent.cs              |   1 -
 .../Avalonia.Markup/Avalonia.Markup.csproj    |   1 -
 src/Markup/Avalonia.Markup/Data/Binding.cs    |   7 -
 .../Avalonia.Markup/Data/BindingBase.cs       |  10 +-
 .../Avalonia.Markup/Data/MultiBinding.cs      |   2 +-
 .../Avalonia.Markup/Data/TemplateBinding.cs   |   3 +-
 .../Parsers/ExpressionObserverBuilder.cs      |   3 +-
 .../Markup/Parsers/Nodes/ElementNameNode.cs   |   1 +
 .../Markup/Parsers/Nodes/FindAncestorNode.cs  |   1 +
 .../Markup/Parsers/Nodes/StringIndexerNode.cs |   2 +-
 .../Avalonia.Skia/FramebufferRenderTarget.cs  |   2 +-
 .../Gpu/OpenGl/GlRenderTarget.cs              |   2 +-
 src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs |   2 +-
 .../Avalonia.Direct2D1.csproj                 |   1 -
 src/Windows/Avalonia.Win32/ClipboardImpl.cs   |   2 +-
 .../Avalonia.Win32/OpenGl/WglContext.cs       |   2 +-
 .../Win32NativeToManagedMenuExporter.cs       |   2 +-
 src/Windows/Avalonia.Win32/Win32Platform.cs   |   2 +-
 .../Composition/WinUiCompositedWindow.cs      |   2 +-
 .../WindowsMountedVolumeInfoListener.cs       |  22 +-
 .../AvaloniaObjectTests_Binding.cs            |   3 +-
 .../Core/ExpressionObserverTests_Lifetime.cs  |   6 +-
 .../Core/ExpressionObserverTests_Property.cs  |   6 +-
 .../Styling/StyleActivatorExtensions.cs       |   5 +-
 .../Avalonia.IntegrationTests.Appium.csproj   |   1 +
 .../Data/BindingTests.cs                      |   6 +-
 .../Data/BindingTests_DataValidation.cs       |   6 +-
 .../Data/MultiBindingTests.cs                 |   4 +
 .../AvaloniaObjectTests_GetSubject.cs         |   3 +-
 tests/Avalonia.UnitTests/TestServices.cs      |   4 -
 .../Avalonia.UnitTests/UnitTestApplication.cs |   1 -
 195 files changed, 2144 insertions(+), 735 deletions(-)
 create mode 100644 src/Avalonia.Base/Reactive/AnonymousObserver.cs
 create mode 100644 src/Avalonia.Base/Reactive/CombinedSubject.cs
 create mode 100644 src/Avalonia.Base/Reactive/CompositeDisposable.cs
 create mode 100644 src/Avalonia.Base/Reactive/Disposable.cs
 create mode 100644 src/Avalonia.Base/Reactive/DisposableMixin.cs
 create mode 100644 src/Avalonia.Base/Reactive/IAvaloniaSubject.cs
 create mode 100644 src/Avalonia.Base/Reactive/LightweightSubject.cs
 create mode 100644 src/Avalonia.Base/Reactive/Observable.cs
 delete mode 100644 src/Avalonia.Base/Reactive/ObservableEx.cs
 create mode 100644 src/Avalonia.Base/Reactive/Operators/CombineLatest.cs
 create mode 100644 src/Avalonia.Base/Reactive/Operators/Sink.cs
 create mode 100644 src/Avalonia.Base/Reactive/Operators/Switch.cs
 delete mode 100644 src/Avalonia.Base/Utilities/IWeakSubscriber.cs
 delete mode 100644 src/Avalonia.Base/Utilities/WeakObservable.cs
 delete mode 100644 src/Avalonia.Controls/Mixins/DisposableMixin.cs
 create mode 100644 src/Avalonia.ReactiveUI/AvaloniaObjectReactiveExtensions.cs
 rename src/{Avalonia.Base/Threading => Avalonia.ReactiveUI}/AvaloniaScheduler.cs (98%)
 rename tests/{Avalonia.Base.UnitTests => Avalonia.ReactiveUI.UnitTests}/AvaloniaObjectTests_GetSubject.cs (95%)

diff --git a/build/Base.props b/build/Base.props
index 100c9088cd..588da8433a 100644
--- a/build/Base.props
+++ b/build/Base.props
@@ -1,6 +1,7 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
     <PackageReference Include="System.ValueTuple" Version="4.5.0" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Version="4.5.4" />
     <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="4.6.0" />
   </ItemGroup>
 </Project>
diff --git a/src/Avalonia.Base/Animation/Animation.cs b/src/Avalonia.Base/Animation/Animation.cs
index 06087cdd6a..d62acc0d52 100644
--- a/src/Avalonia.Base/Animation/Animation.cs
+++ b/src/Avalonia.Base/Animation/Animation.cs
@@ -2,8 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading;
 using System.Threading.Tasks;
 
diff --git a/src/Avalonia.Base/Animation/AnimationInstance`1.cs b/src/Avalonia.Base/Animation/AnimationInstance`1.cs
index 0881fde988..682629c801 100644
--- a/src/Avalonia.Base/Animation/AnimationInstance`1.cs
+++ b/src/Avalonia.Base/Animation/AnimationInstance`1.cs
@@ -1,11 +1,8 @@
 using System;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Animation.Animators;
-using Avalonia.Animation.Utils;
 using Avalonia.Data;
-using Avalonia.Reactive;
-using JetBrains.Annotations;
 
 namespace Avalonia.Animation
 {
diff --git a/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs b/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
index 3168a67d79..dcce75b31c 100644
--- a/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
+++ b/src/Avalonia.Base/Animation/AnimatorKeyFrame.cs
@@ -63,7 +63,7 @@ namespace Avalonia.Animation
             }
             else
             {
-                return this.Bind(ValueProperty, ObservableEx.SingleValue(value).ToBinding(), targetControl);
+                return this.Bind(ValueProperty, Observable.SingleValue(value).ToBinding(), targetControl);
             }
         }
 
diff --git a/src/Avalonia.Base/Animation/Animators/Animator`1.cs b/src/Avalonia.Base/Animation/Animators/Animator`1.cs
index b5d1feb4a7..2db890bd0a 100644
--- a/src/Avalonia.Base/Animation/Animators/Animator`1.cs
+++ b/src/Avalonia.Base/Animation/Animators/Animator`1.cs
@@ -1,8 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
 using Avalonia.Animation.Utils;
 using Avalonia.Collections;
 using Avalonia.Data;
diff --git a/src/Avalonia.Base/Animation/Animators/ColorAnimator.cs b/src/Avalonia.Base/Animation/Animators/ColorAnimator.cs
index 72add21d69..7be974b9e5 100644
--- a/src/Avalonia.Base/Animation/Animators/ColorAnimator.cs
+++ b/src/Avalonia.Base/Animation/Animators/ColorAnimator.cs
@@ -2,7 +2,7 @@
 // and adopted from LottieSharp Project (https://github.com/ascora/LottieSharp).
 
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Logging;
 using Avalonia.Media;
 
diff --git a/src/Avalonia.Base/Animation/Animators/TransformAnimator.cs b/src/Avalonia.Base/Animation/Animators/TransformAnimator.cs
index e12ca722f9..8040fb595b 100644
--- a/src/Avalonia.Base/Animation/Animators/TransformAnimator.cs
+++ b/src/Avalonia.Base/Animation/Animators/TransformAnimator.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Logging;
 using Avalonia.Media;
 using Avalonia.Media.Transformation;
diff --git a/src/Avalonia.Base/Animation/Clock.cs b/src/Avalonia.Base/Animation/Clock.cs
index 5afd2ae705..f2bce9d3a5 100644
--- a/src/Avalonia.Base/Animation/Clock.cs
+++ b/src/Avalonia.Base/Animation/Clock.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 
 namespace Avalonia.Animation
 {
diff --git a/src/Avalonia.Base/Animation/CrossFade.cs b/src/Avalonia.Base/Animation/CrossFade.cs
index a229bc7ce6..640d6456a3 100644
--- a/src/Avalonia.Base/Animation/CrossFade.cs
+++ b/src/Avalonia.Base/Animation/CrossFade.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Animation.Easings;
@@ -108,7 +108,7 @@ namespace Avalonia.Animation
             }
 
             var tasks = new List<Task>();
-            using (var disposables = new CompositeDisposable())
+            using (var disposables = new CompositeDisposable(1))
             {
                 if (to != null)
                 {
diff --git a/src/Avalonia.Base/Avalonia.Base.csproj b/src/Avalonia.Base/Avalonia.Base.csproj
index 0d3da66f7a..d40fe1e6f8 100644
--- a/src/Avalonia.Base/Avalonia.Base.csproj
+++ b/src/Avalonia.Base/Avalonia.Base.csproj
@@ -14,7 +14,6 @@
   </ItemGroup>
   <Import Project="..\..\build\Base.props" />
   <Import Project="..\..\build\Binding.props" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
   <Import Project="..\..\build\System.Memory.props" />
   <Import Project="..\..\build\ApiDiff.props" />
@@ -35,6 +34,12 @@
     <InternalsVisibleTo Include="Avalonia.Markup.Xaml, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.ColorPicker, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.DataGrid, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Headless, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Native, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.FreeDesktop, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.X11, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.OpenGL, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Skia, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.UnitTests, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.DesignerSupport, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Direct2D1.RenderTests, PublicKey=$(AvaloniaPublicKey)" />
diff --git a/src/Avalonia.Base/AvaloniaObjectExtensions.cs b/src/Avalonia.Base/AvaloniaObjectExtensions.cs
index 867d6215a5..7b17b9152d 100644
--- a/src/Avalonia.Base/AvaloniaObjectExtensions.cs
+++ b/src/Avalonia.Base/AvaloniaObjectExtensions.cs
@@ -1,10 +1,6 @@
 using System;
-using System.Reactive;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
-using Avalonia.Data;
 using Avalonia.Reactive;
+using Avalonia.Data;
 
 namespace Avalonia
 {
@@ -127,108 +123,6 @@ namespace Avalonia
                 property ?? throw new ArgumentNullException(nameof(property)));
         }
 
-        /// <summary>
-        /// Gets a subject for an <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{Object}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<object?> GetSubject(
-            this AvaloniaObject o,
-            AvaloniaProperty property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<object?>(
-                Observer.Create<object?>(x => o.SetValue(property, x, priority)),
-                o.GetObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for an <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <typeparam name="T">The property type.</typeparam>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<T> GetSubject<T>(
-            this AvaloniaObject o,
-            AvaloniaProperty<T> property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<T>(
-                Observer.Create<T>(x => o.SetValue(property, x, priority)),
-                o.GetObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for a <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{Object}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<BindingValue<object?>> GetBindingSubject(
-            this AvaloniaObject o,
-            AvaloniaProperty property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<BindingValue<object?>>(
-                Observer.Create<BindingValue<object?>>(x =>
-                {
-                    if (x.HasValue)
-                    {
-                        o.SetValue(property, x.Value, priority);
-                    }
-                }),
-                o.GetBindingObservable(property));
-        }
-
-        /// <summary>
-        /// Gets a subject for a <see cref="AvaloniaProperty"/>.
-        /// </summary>
-        /// <typeparam name="T">The property type.</typeparam>
-        /// <param name="o">The object.</param>
-        /// <param name="property">The property.</param>
-        /// <param name="priority">
-        /// The priority with which binding values are written to the object.
-        /// </param>
-        /// <returns>
-        /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
-        /// property.
-        /// </returns>
-        public static ISubject<BindingValue<T>> GetBindingSubject<T>(
-            this AvaloniaObject o,
-            AvaloniaProperty<T> property,
-            BindingPriority priority = BindingPriority.LocalValue)
-        {
-            return Subject.Create<BindingValue<T>>(
-                Observer.Create<BindingValue<T>>(x =>
-                {
-                    if (x.HasValue)
-                    {
-                        o.SetValue(property, x.Value, priority);
-                    }
-                }),
-                o.GetBindingObservable(property));
-        }
-
         /// <summary>
         /// Binds an <see cref="AvaloniaProperty"/> to an observable.
         /// </summary>
@@ -407,13 +301,7 @@ namespace Avalonia
             Action<TTarget, AvaloniaPropertyChangedEventArgs> action)
             where TTarget : AvaloniaObject
         {
-            return observable.Subscribe(e =>
-            {
-                if (e.Sender is TTarget target)
-                {
-                    action(target, e);
-                }
-            });
+            return observable.Subscribe(new ClassHandlerObserver<TTarget>(action));
         }
 
         /// <summary>
@@ -431,13 +319,7 @@ namespace Avalonia
             this IObservable<AvaloniaPropertyChangedEventArgs<TValue>> observable,
             Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> action) where TTarget : AvaloniaObject
         {
-            return observable.Subscribe(e =>
-            {
-                if (e.Sender is TTarget target)
-                {
-                    action(target, e);
-                }
-            });
+            return observable.Subscribe(new ClassHandlerObserver<TTarget, TValue>(action));
         }
 
         private class BindingAdaptor : IBinding
@@ -458,5 +340,57 @@ namespace Avalonia
                 return InstancedBinding.OneWay(_source);
             }
         }
+        
+        private class ClassHandlerObserver<TTarget, TValue> : IObserver<AvaloniaPropertyChangedEventArgs<TValue>>
+        {
+            private readonly Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> _action;
+
+            public ClassHandlerObserver(Action<TTarget, AvaloniaPropertyChangedEventArgs<TValue>> action)
+            {
+                _action = action;
+            }
+
+            public void OnCompleted()
+            {
+            }
+
+            public void OnError(Exception error)
+            {
+            }
+
+            public void OnNext(AvaloniaPropertyChangedEventArgs<TValue> value)
+            {
+                if (value.Sender is TTarget target)
+                {
+                    _action(target, value);
+                }
+            }
+        }
+
+        private class ClassHandlerObserver<TTarget> : IObserver<AvaloniaPropertyChangedEventArgs>
+        {
+            private readonly Action<TTarget, AvaloniaPropertyChangedEventArgs> _action;
+
+            public ClassHandlerObserver(Action<TTarget, AvaloniaPropertyChangedEventArgs> action)
+            {
+                _action = action;
+            }
+
+            public void OnCompleted()
+            {
+            }
+
+            public void OnError(Exception error)
+            {
+            }
+
+            public void OnNext(AvaloniaPropertyChangedEventArgs value)
+            {
+                if (value.Sender is TTarget target)
+                {
+                    _action(target, value);
+                }
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Base/AvaloniaProperty`1.cs b/src/Avalonia.Base/AvaloniaProperty`1.cs
index 53444ee475..f8c062a176 100644
--- a/src/Avalonia.Base/AvaloniaProperty`1.cs
+++ b/src/Avalonia.Base/AvaloniaProperty`1.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Subjects;
 using Avalonia.Data;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia
@@ -12,7 +12,7 @@ namespace Avalonia
     /// <typeparam name="TValue">The value type of the property.</typeparam>
     public abstract class AvaloniaProperty<TValue> : AvaloniaProperty
     {
-        private readonly Subject<AvaloniaPropertyChangedEventArgs<TValue>> _changed;
+        private readonly LightweightSubject<AvaloniaPropertyChangedEventArgs<TValue>> _changed;
 
         /// <summary>
         /// Initializes a new instance of the <see cref="AvaloniaProperty{TValue}"/> class.
@@ -28,7 +28,7 @@ namespace Avalonia
             Action<AvaloniaObject, bool>? notifying = null)
             : base(name, typeof(TValue), ownerType, metadata, notifying)
         {
-            _changed = new Subject<AvaloniaPropertyChangedEventArgs<TValue>>();
+            _changed = new LightweightSubject<AvaloniaPropertyChangedEventArgs<TValue>>();
         }
 
         /// <summary>
diff --git a/src/Avalonia.Base/ClassBindingManager.cs b/src/Avalonia.Base/ClassBindingManager.cs
index 589b9b2d01..a9726cb86e 100644
--- a/src/Avalonia.Base/ClassBindingManager.cs
+++ b/src/Avalonia.Base/ClassBindingManager.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Data;
+using Avalonia.Reactive;
 
 namespace Avalonia
 {
diff --git a/src/Avalonia.Base/Collections/AvaloniaListExtensions.cs b/src/Avalonia.Base/Collections/AvaloniaListExtensions.cs
index c4684960d6..2178577eb7 100644
--- a/src/Avalonia.Base/Collections/AvaloniaListExtensions.cs
+++ b/src/Avalonia.Base/Collections/AvaloniaListExtensions.cs
@@ -3,7 +3,7 @@ using System.Collections;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 
 namespace Avalonia.Collections
 {
diff --git a/src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs b/src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs
index 689fcc89a4..68863ea257 100644
--- a/src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs
+++ b/src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Specialized;
-using System.Reactive.Linq;
 using Avalonia.Reactive;
 using Avalonia.Utilities;
 
diff --git a/src/Avalonia.Base/Controls/NameScopeLocator.cs b/src/Avalonia.Base/Controls/NameScopeLocator.cs
index f0ce7f8a5b..371931f971 100644
--- a/src/Avalonia.Base/Controls/NameScopeLocator.cs
+++ b/src/Avalonia.Base/Controls/NameScopeLocator.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia.Controls
diff --git a/src/Avalonia.Base/Data/BindingOperations.cs b/src/Avalonia.Base/Data/BindingOperations.cs
index ceb3f71285..0b737dd959 100644
--- a/src/Avalonia.Base/Data/BindingOperations.cs
+++ b/src/Avalonia.Base/Data/BindingOperations.cs
@@ -1,6 +1,5 @@
 using System;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 
 namespace Avalonia.Data
 {
@@ -46,15 +45,15 @@ namespace Avalonia.Data
                         throw new InvalidOperationException("InstancedBinding does not contain an observable.");
                     return target.Bind(property, binding.Observable, binding.Priority);
                 case BindingMode.TwoWay:
+                    if (binding.Observable is null)
+                        throw new InvalidOperationException("InstancedBinding does not contain an observable.");
                     if (binding.Subject is null)
                         throw new InvalidOperationException("InstancedBinding does not contain a subject.");
                     return new TwoWayBindingDisposable(
-                        target.Bind(property, binding.Subject, binding.Priority),
+                        target.Bind(property, binding.Observable, binding.Priority),
                         target.GetObservable(property).Subscribe(binding.Subject));
                 case BindingMode.OneTime:
-                    var source = binding.Subject ?? binding.Observable;
-
-                    if (source != null)
+                    if (binding.Observable is {} source)
                     {
                         // Perf: Avoid allocating closure in the outer scope.
                         var targetCopy = target;
diff --git a/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
index e340966983..536c14dcf9 100644
--- a/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
+++ b/src/Avalonia.Base/Data/Core/AvaloniaPropertyAccessorNode.cs
@@ -1,5 +1,4 @@
 using System;
-using System.Reactive.Linq;
 using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core
diff --git a/src/Avalonia.Base/Data/Core/BindingExpression.cs b/src/Avalonia.Base/Data/Core/BindingExpression.cs
index f60b4722d9..55caf8070e 100644
--- a/src/Avalonia.Base/Data/Core/BindingExpression.cs
+++ b/src/Avalonia.Base/Data/Core/BindingExpression.cs
@@ -1,11 +1,9 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
+using Avalonia.Reactive;
 using Avalonia.Data.Converters;
 using Avalonia.Logging;
-using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia.Data.Core
@@ -15,7 +13,7 @@ namespace Avalonia.Data.Core
     /// that are sent and received.
     /// </summary>
     [RequiresUnreferencedCode(TrimmingMessages.TypeConvertionRequiresUnreferencedCodeMessage)]
-    public class BindingExpression : LightweightObservableBase<object?>, ISubject<object?>, IDescription
+    public class BindingExpression : LightweightObservableBase<object?>, IAvaloniaSubject<object?>, IDescription
     {
         private readonly ExpressionObserver _inner;
         private readonly Type _targetType;
diff --git a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
index 2151c100e5..d1d7b98562 100644
--- a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
+++ b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
@@ -2,8 +2,6 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq.Expressions;
-using System.Reactive;
-using System.Reactive.Linq;
 using Avalonia.Data.Core.Parsers;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Reactive;
@@ -99,14 +97,14 @@ namespace Avalonia.Data.Core
         /// </summary>
         /// <param name="rootGetter">A function which gets the root object.</param>
         /// <param name="node">The expression.</param>
-        /// <param name="update">An observable which triggers a re-read of the getter.</param>
+        /// <param name="update">An observable which triggers a re-read of the getter. Generic argument value is not used.</param>
         /// <param name="description">
         /// A description of the expression.
         /// </param>
         public ExpressionObserver(
             Func<object?> rootGetter,
             ExpressionNode node,
-            IObservable<Unit> update,
+            IObservable<object> update,
             string? description)
         {
             Description = description;
@@ -164,7 +162,7 @@ namespace Avalonia.Data.Core
         /// </summary>
         /// <param name="rootGetter">A function which gets the root object.</param>
         /// <param name="expression">The expression.</param>
-        /// <param name="update">An observable which triggers a re-read of the getter.</param>
+        /// <param name="update">An observable which triggers a re-read of the getter. Generic argument value is not used.</param>
         /// <param name="enableDataValidation">Whether or not to track data validation</param>
         /// <param name="description">
         /// A description of the expression. If null, <paramref name="expression"/>'s string representation will be used.
@@ -173,7 +171,7 @@ namespace Avalonia.Data.Core
         public static ExpressionObserver Create<T, U>(
             Func<T> rootGetter,
             Expression<Func<T, U>> expression,
-            IObservable<Unit> update,
+            IObservable<object> update,
             bool enableDataValidation = false,
             string? description = null)
         {
@@ -296,9 +294,10 @@ namespace Avalonia.Data.Core
             if (_root is IObservable<object> observable)
             {
                 _rootSubscription = observable.Subscribe(
-                    x => _node.Target = new WeakReference<object?>(x != AvaloniaProperty.UnsetValue ? x : null),
-                    x => PublishCompleted(),
-                    () => PublishCompleted());
+                    new AnonymousObserver<object>(
+                        x => _node.Target = new WeakReference<object?>(x != AvaloniaProperty.UnsetValue ? x : null),
+                        x => PublishCompleted(),
+                        PublishCompleted));
             }
             else
             {
diff --git a/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs b/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
index a808827896..2fad96701d 100644
--- a/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
+++ b/src/Avalonia.Base/Data/Core/IndexerNodeBase.cs
@@ -1,48 +1,47 @@
 using System;
 using System.Collections;
-using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
-using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia.Data.Core
 {
-    public abstract class IndexerNodeBase : SettableNode
+    public abstract class IndexerNodeBase : SettableNode,
+        IWeakEventSubscriber<NotifyCollectionChangedEventArgs>,
+        IWeakEventSubscriber<PropertyChangedEventArgs>
     {
-        private IDisposable? _subscription;
-        
         protected override void StartListeningCore(WeakReference<object?> reference)
         {
             reference.TryGetTarget(out var target);
 
-            var incc = target as INotifyCollectionChanged;
-            var inpc = target as INotifyPropertyChanged;
-            var inputs = new List<IObservable<object?>>();
-
-            if (incc != null)
+            if (target is INotifyCollectionChanged incc)
             {
-                inputs.Add(WeakObservable.FromEventPattern(
-                    incc, WeakEvents.CollectionChanged)
-                    .Where(x => ShouldUpdate(x.Sender, x.EventArgs))
-                    .Select(_ => GetValue(target)));
+                WeakEvents.CollectionChanged.Subscribe(incc, this);
             }
 
-            if (inpc != null)
+            if (target is INotifyPropertyChanged inpc)
             {
-                inputs.Add(WeakObservable.FromEventPattern(
-                    inpc, WeakEvents.PropertyChanged)
-                    .Where(x => ShouldUpdate(x.Sender, x.EventArgs))
-                    .Select(_ => GetValue(target)));
+                WeakEvents.PropertyChanged.Subscribe(inpc, this);
             }
-
-            _subscription = Observable.Merge(inputs).StartWith(GetValue(target)).Subscribe(ValueChanged);
+            
+            ValueChanged(GetValue(target));
         }
 
         protected override void StopListeningCore()
         {
-            _subscription?.Dispose();
+            if (Target.TryGetTarget(out var target))
+            {
+                if (target is INotifyCollectionChanged incc)
+                {
+                    WeakEvents.CollectionChanged.Unsubscribe(incc, this);
+                }
+
+                if (target is INotifyPropertyChanged inpc)
+                {
+                    WeakEvents.PropertyChanged.Unsubscribe(inpc, this);
+                }
+            }
         }
 
         protected abstract object? GetValue(object? target);
@@ -83,5 +82,21 @@ namespace Avalonia.Data.Core
         }
 
         protected abstract bool ShouldUpdate(object? sender, PropertyChangedEventArgs e);
+
+        void IWeakEventSubscriber<NotifyCollectionChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, NotifyCollectionChangedEventArgs e)
+        {
+            if (ShouldUpdate(sender, e))
+            {
+                ValueChanged(GetValue(sender));
+            }
+        }
+
+        void IWeakEventSubscriber<PropertyChangedEventArgs>.OnEvent(object? sender, WeakEvent ev, PropertyChangedEventArgs e)
+        {
+            if (ShouldUpdate(sender, e))
+            {
+                ValueChanged(GetValue(sender));
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
index ebee4586db..b40628fd35 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/ObservableStreamPlugin.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Reflection;
 
 namespace Avalonia.Data.Core.Plugins
@@ -12,8 +12,15 @@ namespace Avalonia.Data.Core.Plugins
     [UnconditionalSuppressMessage("Trimming", "IL3050", Justification = TrimmingMessages.IgnoreNativeAotSupressWarningMessage)]
     public class ObservableStreamPlugin : IStreamPlugin
     {
-        static MethodInfo? observableSelect;
+        private static MethodInfo? s_observableGeneric;
+        private static MethodInfo? s_observableSelect;
 
+        [DynamicDependency(DynamicallyAccessedMemberTypes.NonPublicProperties, "Avalonia.Data.Core.Plugins.ObservableStreamPlugin", "Avalonia.Base")]
+        public ObservableStreamPlugin()
+        {
+            
+        }
+        
         /// <summary>
         /// Checks whether this plugin handles the specified value.
         /// </summary>
@@ -54,56 +61,32 @@ namespace Avalonia.Data.Core.Plugins
                   x.IsGenericType &&
                   x.GetGenericTypeDefinition() == typeof(IObservable<>)).GetGenericArguments()[0];
 
-            // Get the Observable.Select method.
-            var select = GetObservableSelect(sourceType);
-
-            // Make a Box<> delegate of the correct type.
-            var funcType = typeof(Func<,>).MakeGenericType(sourceType, typeof(object));
-            var box = GetType().GetMethod(nameof(Box), BindingFlags.Static | BindingFlags.NonPublic)!
-                .MakeGenericMethod(sourceType)
-                .CreateDelegate(funcType);
+            // Get the BoxObservable<T> method.
+            var select = GetBoxObservable(sourceType);
 
-            // Call Observable.Select(target, box);
+            // Call BoxObservable(target);
             return (IObservable<object?>)select.Invoke(
                 null,
-                new object[] { target, box })!;
+                new[] { target })!;
         }
 
         [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
-        private static MethodInfo GetObservableSelect(Type source)
+        private static MethodInfo GetBoxObservable(Type source)
         {
-            return GetObservableSelect().MakeGenericMethod(source, typeof(object));
+            return (s_observableGeneric ??= GetBoxObservable()).MakeGenericMethod(source);
         }
 
-        private static MethodInfo GetObservableSelect()
+        [RequiresUnreferencedCode(TrimmingMessages.StreamPluginRequiresUnreferencedCodeMessage)]
+        private static MethodInfo GetBoxObservable()
         {
-            if (observableSelect == null)
-            {
-                observableSelect = typeof(Observable).GetRuntimeMethods().First(x =>
-                {
-                    if (x.Name == nameof(Observable.Select) &&
-                        x.ContainsGenericParameters &&
-                        x.GetGenericArguments().Length == 2)
-                    {
-                        var parameters = x.GetParameters();
-
-                        if (parameters.Length == 2 &&
-                            parameters[0].ParameterType.IsConstructedGenericType &&
-                            parameters[0].ParameterType.GetGenericTypeDefinition() == typeof(IObservable<>) &&
-                            parameters[1].ParameterType.IsConstructedGenericType &&
-                            parameters[1].ParameterType.GetGenericTypeDefinition() == typeof(Func<,>))
-                        {
-                            return true;
-                        }
-                    }
-
-                    return false;
-                });
-            }
-
-            return observableSelect;
+            return s_observableSelect
+               ??= typeof(ObservableStreamPlugin).GetMethod(nameof(BoxObservable), BindingFlags.Static | BindingFlags.NonPublic)
+               ?? throw new InvalidOperationException("BoxObservable method was not found.");
         }
 
-        private static object? Box<T>(T value) => (object?)value;
+        private static IObservable<object?> BoxObservable<T>(IObservable<T> source)
+        {
+            return source.Select(v => (object?)v);
+        }
     }
 }
diff --git a/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
index 5203aa9f57..715f4604cf 100644
--- a/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
+++ b/src/Avalonia.Base/Data/Core/Plugins/TaskStreamPlugin.cs
@@ -1,9 +1,8 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
 using System.Reflection;
 using System.Threading.Tasks;
+using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core.Plugins
 {
@@ -50,7 +49,7 @@ namespace Avalonia.Data.Core.Plugins
                         case TaskStatus.Faulted:
                             return HandleCompleted(task);
                         default:
-                            var subject = new Subject<object?>();
+                            var subject = new LightweightSubject<object?>();
                             task.ContinueWith(
                                     x => HandleCompleted(task).Subscribe(subject),
                                     TaskScheduler.FromCurrentSynchronizationContext())
diff --git a/src/Avalonia.Base/Data/Core/StreamNode.cs b/src/Avalonia.Base/Data/Core/StreamNode.cs
index 6dc6d07184..ba18a2173b 100644
--- a/src/Avalonia.Base/Data/Core/StreamNode.cs
+++ b/src/Avalonia.Base/Data/Core/StreamNode.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Linq;
 using Avalonia.Data.Core.Plugins;
+using Avalonia.Reactive;
 
 namespace Avalonia.Data.Core
 {
diff --git a/src/Avalonia.Base/Data/IndexerBinding.cs b/src/Avalonia.Base/Data/IndexerBinding.cs
index fcd179b9b2..83ef8f76b4 100644
--- a/src/Avalonia.Base/Data/IndexerBinding.cs
+++ b/src/Avalonia.Base/Data/IndexerBinding.cs
@@ -1,4 +1,6 @@
-namespace Avalonia.Data
+using Avalonia.Reactive;
+
+namespace Avalonia.Data
 {
     public class IndexerBinding : IBinding
     {
@@ -22,7 +24,10 @@
             object? anchor = null,
             bool enableDataValidation = false)
         {
-            return new InstancedBinding(Source.GetSubject(Property), Mode, BindingPriority.LocalValue);
+            var subject = new CombinedSubject<object?>(
+                new AnonymousObserver<object?>(x => Source.SetValue(Property, x, BindingPriority.LocalValue)),
+                Source.GetObservable(Property));
+            return new InstancedBinding(subject, Mode, BindingPriority.LocalValue);
         }
     }
 }
diff --git a/src/Avalonia.Base/Data/IndexerDescriptor.cs b/src/Avalonia.Base/Data/IndexerDescriptor.cs
index c823630d3c..3eb5a6ef12 100644
--- a/src/Avalonia.Base/Data/IndexerDescriptor.cs
+++ b/src/Avalonia.Base/Data/IndexerDescriptor.cs
@@ -1,12 +1,11 @@
 using System;
-using System.Reactive;
 
 namespace Avalonia.Data
 {
     /// <summary>
     /// Holds a description of a binding for <see cref="AvaloniaObject"/>'s [] operator.
     /// </summary>
-    public class IndexerDescriptor : ObservableBase<object?>, IDescription
+    public class IndexerDescriptor : IObservable<object?>, IDescription
     {
         /// <summary>
         /// Gets or sets the binding mode.
@@ -104,7 +103,7 @@ namespace Avalonia.Data
         }
 
         /// <inheritdoc/>
-        protected override IDisposable SubscribeCore(IObserver<object?> observer)
+        public IDisposable Subscribe(IObserver<object?> observer)
         {
             if (SourceObservable is null && Source is null)
                 throw new InvalidOperationException("Cannot subscribe to IndexerDescriptor.");
diff --git a/src/Avalonia.Base/Data/InstancedBinding.cs b/src/Avalonia.Base/Data/InstancedBinding.cs
index a349486bf8..a60c1d72ec 100644
--- a/src/Avalonia.Base/Data/InstancedBinding.cs
+++ b/src/Avalonia.Base/Data/InstancedBinding.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Subjects;
+using Avalonia.Reactive;
 
 namespace Avalonia.Data
 {
@@ -14,28 +14,7 @@ namespace Avalonia.Data
     /// </remarks>
     public class InstancedBinding
     {
-        /// <summary>
-        /// Initializes a new instance of the <see cref="InstancedBinding"/> class.
-        /// </summary>
-        /// <param name="subject">The binding source.</param>
-        /// <param name="mode">The binding mode.</param>
-        /// <param name="priority">The priority of the binding.</param>
-        /// <remarks>
-        /// This constructor can be used to create any type of binding and as such requires an
-        /// <see cref="ISubject{Object}"/> as the binding source because this is the only binding
-        /// source which can be used for all binding modes. If you wish to create an instance with
-        /// something other than a subject, use one of the static creation methods on this class.
-        /// </remarks>
-        public InstancedBinding(ISubject<object?> subject, BindingMode mode, BindingPriority priority)
-        {
-            Contract.Requires<ArgumentNullException>(subject != null);
-
-            Mode = mode;
-            Priority = priority;
-            Value = subject;
-        }
-
-        private InstancedBinding(object? value, BindingMode mode, BindingPriority priority)
+        internal InstancedBinding(object? value, BindingMode mode, BindingPriority priority)
         {
             Mode = mode;
             Priority = priority;
@@ -63,9 +42,14 @@ namespace Avalonia.Data
         public IObservable<object?>? Observable => Value as IObservable<object?>;
 
         /// <summary>
-        /// Gets the <see cref="Value"/> as a subject.
+        /// Gets the <see cref="Value"/> as an observer.
         /// </summary>
-        public ISubject<object?>? Subject => Value as ISubject<object?>;
+        public IObserver<object?>? Observer => Value as IObserver<object?>;
+
+        /// <summary>
+        /// Gets the <see cref="Subject"/> as an subject.
+        /// </summary>
+        internal IAvaloniaSubject<object?>? Subject => Value as IAvaloniaSubject<object?>;
 
         /// <summary>
         /// Creates a new one-time binding with a fixed value.
@@ -113,30 +97,34 @@ namespace Avalonia.Data
         /// <summary>
         /// Creates a new one-way to source binding.
         /// </summary>
-        /// <param name="subject">The binding source.</param>
+        /// <param name="observer">The binding source.</param>
         /// <param name="priority">The priority of the binding.</param>
         /// <returns>An <see cref="InstancedBinding"/> instance.</returns>
         public static InstancedBinding OneWayToSource(
-            ISubject<object?> subject,
+            IObserver<object?> observer,
             BindingPriority priority = BindingPriority.LocalValue)
         {
-            _ = subject ?? throw new ArgumentNullException(nameof(subject));
+            _ = observer ?? throw new ArgumentNullException(nameof(observer));
 
-            return new InstancedBinding(subject, BindingMode.OneWayToSource, priority);
+            return new InstancedBinding(observer, BindingMode.OneWayToSource, priority);
         }
 
         /// <summary>
         /// Creates a new two-way binding.
         /// </summary>
-        /// <param name="subject">The binding source.</param>
+        /// <param name="observable">The binding source.</param>
+        /// <param name="observer">The binding source.</param>
         /// <param name="priority">The priority of the binding.</param>
         /// <returns>An <see cref="InstancedBinding"/> instance.</returns>
         public static InstancedBinding TwoWay(
-            ISubject<object?> subject,
+            IObservable<object?> observable,
+            IObserver<object?> observer,
             BindingPriority priority = BindingPriority.LocalValue)
         {
-            _ = subject ?? throw new ArgumentNullException(nameof(subject));
+            _ = observable ?? throw new ArgumentNullException(nameof(observable));
+            _ = observer ?? throw new ArgumentNullException(nameof(observer));
 
+            var subject = new CombinedSubject<object?>(observer, observable);
             return new InstancedBinding(subject, BindingMode.TwoWay, priority);
         }
 
diff --git a/src/Avalonia.Base/Input/Gestures.cs b/src/Avalonia.Base/Input/Gestures.cs
index 1ea88fe824..8de0afbc1f 100644
--- a/src/Avalonia.Base/Input/Gestures.cs
+++ b/src/Avalonia.Base/Input/Gestures.cs
@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Interactivity;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Input
diff --git a/src/Avalonia.Base/Input/InputElement.cs b/src/Avalonia.Base/Input/InputElement.cs
index fa755277cc..59b45cec48 100644
--- a/src/Avalonia.Base/Input/InputElement.cs
+++ b/src/Avalonia.Base/Input/InputElement.cs
@@ -7,6 +7,7 @@ using Avalonia.Data;
 using Avalonia.Input.GestureRecognizers;
 using Avalonia.Input.TextInput;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 #nullable enable
diff --git a/src/Avalonia.Base/Input/InputManager.cs b/src/Avalonia.Base/Input/InputManager.cs
index f604ff8e74..e87665fd54 100644
--- a/src/Avalonia.Base/Input/InputManager.cs
+++ b/src/Avalonia.Base/Input/InputManager.cs
@@ -1,6 +1,6 @@
 using System;
-using System.Reactive.Subjects;
 using Avalonia.Input.Raw;
+using Avalonia.Reactive;
 
 namespace Avalonia.Input
 {
@@ -10,9 +10,9 @@ namespace Avalonia.Input
     /// </summary>
     public class InputManager : IInputManager
     {
-        private readonly Subject<RawInputEventArgs> _preProcess = new Subject<RawInputEventArgs>();
-        private readonly Subject<RawInputEventArgs> _process = new Subject<RawInputEventArgs>();
-        private readonly Subject<RawInputEventArgs> _postProcess = new Subject<RawInputEventArgs>();
+        private readonly LightweightSubject<RawInputEventArgs> _preProcess = new();
+        private readonly LightweightSubject<RawInputEventArgs> _process = new();
+        private readonly LightweightSubject<RawInputEventArgs> _postProcess = new();
 
         /// <summary>
         /// Gets the global instance of the input manager.
diff --git a/src/Avalonia.Base/Input/MouseDevice.cs b/src/Avalonia.Base/Input/MouseDevice.cs
index 9b17e336d3..e1c42c4ead 100644
--- a/src/Avalonia.Base/Input/MouseDevice.cs
+++ b/src/Avalonia.Base/Input/MouseDevice.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using Avalonia.Reactive;
 using Avalonia.Input.Raw;
 using Avalonia.Platform;
 using Avalonia.Utilities;
diff --git a/src/Avalonia.Base/Input/TextInput/InputMethodManager.cs b/src/Avalonia.Base/Input/TextInput/InputMethodManager.cs
index 8a3f5b968e..9b5668bf98 100644
--- a/src/Avalonia.Base/Input/TextInput/InputMethodManager.cs
+++ b/src/Avalonia.Base/Input/TextInput/InputMethodManager.cs
@@ -1,5 +1,5 @@
 using System;
-using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Input.TextInput
 {
diff --git a/src/Avalonia.Base/Interactivity/InteractiveExtensions.cs b/src/Avalonia.Base/Interactivity/InteractiveExtensions.cs
index b12cf64fdf..5264b96679 100644
--- a/src/Avalonia.Base/Interactivity/InteractiveExtensions.cs
+++ b/src/Avalonia.Base/Interactivity/InteractiveExtensions.cs
@@ -1,6 +1,5 @@
 using System;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 
 namespace Avalonia.Interactivity
 {
diff --git a/src/Avalonia.Base/Interactivity/RoutedEvent.cs b/src/Avalonia.Base/Interactivity/RoutedEvent.cs
index 7046871538..79a4dc60e4 100644
--- a/src/Avalonia.Base/Interactivity/RoutedEvent.cs
+++ b/src/Avalonia.Base/Interactivity/RoutedEvent.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Subjects;
+using Avalonia.Reactive;
 
 namespace Avalonia.Interactivity
 {
@@ -13,8 +13,8 @@ namespace Avalonia.Interactivity
 
     public class RoutedEvent
     {
-        private readonly Subject<(object, RoutedEventArgs)> _raised = new Subject<(object, RoutedEventArgs)>();
-        private readonly Subject<RoutedEventArgs> _routeFinished = new Subject<RoutedEventArgs>();
+        private readonly LightweightSubject<(object, RoutedEventArgs)> _raised = new();
+        private readonly LightweightSubject<RoutedEventArgs> _routeFinished = new();
 
         public RoutedEvent(
             string name,
diff --git a/src/Avalonia.Base/Layout/Layoutable.cs b/src/Avalonia.Base/Layout/Layoutable.cs
index d185148894..9a899ba084 100644
--- a/src/Avalonia.Base/Layout/Layoutable.cs
+++ b/src/Avalonia.Base/Layout/Layoutable.cs
@@ -1,6 +1,6 @@
 using System;
 using Avalonia.Logging;
-using Avalonia.Styling;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 #nullable enable
diff --git a/src/Avalonia.Base/Media/Brush.cs b/src/Avalonia.Base/Media/Brush.cs
index 4138f1c891..a1afb458c6 100644
--- a/src/Avalonia.Base/Media/Brush.cs
+++ b/src/Avalonia.Base/Media/Brush.cs
@@ -3,6 +3,7 @@ using System.ComponentModel;
 using Avalonia.Animation;
 using Avalonia.Animation.Animators;
 using Avalonia.Media.Immutable;
+using Avalonia.Reactive;
 
 namespace Avalonia.Media
 {
diff --git a/src/Avalonia.Base/Media/DashStyle.cs b/src/Avalonia.Base/Media/DashStyle.cs
index 9c30b6f872..92b07191e6 100644
--- a/src/Avalonia.Base/Media/DashStyle.cs
+++ b/src/Avalonia.Base/Media/DashStyle.cs
@@ -4,6 +4,7 @@ using System.Collections.Specialized;
 using Avalonia.Animation;
 using Avalonia.Collections;
 using Avalonia.Media.Immutable;
+using Avalonia.Reactive;
 
 #nullable enable
 
diff --git a/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs b/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
index 0e485d0db8..b7a186dde4 100644
--- a/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
+++ b/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 
 namespace Avalonia.Media
 {
diff --git a/src/Avalonia.Base/Media/Geometry.cs b/src/Avalonia.Base/Media/Geometry.cs
index 2019f54c70..dd162c1e71 100644
--- a/src/Avalonia.Base/Media/Geometry.cs
+++ b/src/Avalonia.Base/Media/Geometry.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 
 namespace Avalonia.Media
 {
diff --git a/src/Avalonia.Base/Media/GradientBrush.cs b/src/Avalonia.Base/Media/GradientBrush.cs
index 83cdaa1694..e1654a01b2 100644
--- a/src/Avalonia.Base/Media/GradientBrush.cs
+++ b/src/Avalonia.Base/Media/GradientBrush.cs
@@ -6,6 +6,7 @@ using System.ComponentModel;
 using Avalonia.Animation.Animators;
 using Avalonia.Collections;
 using Avalonia.Metadata;
+using Avalonia.Reactive;
 
 namespace Avalonia.Media
 {
diff --git a/src/Avalonia.Base/Media/MatrixTransform.cs b/src/Avalonia.Base/Media/MatrixTransform.cs
index c61acb730c..22f39b1ee2 100644
--- a/src/Avalonia.Base/Media/MatrixTransform.cs
+++ b/src/Avalonia.Base/Media/MatrixTransform.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Media
diff --git a/src/Avalonia.Base/Media/RotateTransform.cs b/src/Avalonia.Base/Media/RotateTransform.cs
index 3bd409149c..ab3ea6770f 100644
--- a/src/Avalonia.Base/Media/RotateTransform.cs
+++ b/src/Avalonia.Base/Media/RotateTransform.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Media
diff --git a/src/Avalonia.Base/Media/ScaleTransform.cs b/src/Avalonia.Base/Media/ScaleTransform.cs
index d4c1a7f993..86163df471 100644
--- a/src/Avalonia.Base/Media/ScaleTransform.cs
+++ b/src/Avalonia.Base/Media/ScaleTransform.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Media
diff --git a/src/Avalonia.Base/Media/SkewTransform.cs b/src/Avalonia.Base/Media/SkewTransform.cs
index 066f5371c3..2de2d734c5 100644
--- a/src/Avalonia.Base/Media/SkewTransform.cs
+++ b/src/Avalonia.Base/Media/SkewTransform.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Media
diff --git a/src/Avalonia.Base/Media/TranslateTransform.cs b/src/Avalonia.Base/Media/TranslateTransform.cs
index 0f910f3600..75528a4261 100644
--- a/src/Avalonia.Base/Media/TranslateTransform.cs
+++ b/src/Avalonia.Base/Media/TranslateTransform.cs
@@ -1,4 +1,5 @@
 using System;
+using Avalonia.Reactive;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Media
diff --git a/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs b/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
index b5ac5c817d..11dc80ef8f 100644
--- a/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
+++ b/src/Avalonia.Base/PropertyStore/BindingEntryBase.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Data;
 using Avalonia.Threading;
 
diff --git a/src/Avalonia.Base/Reactive/AnonymousObserver.cs b/src/Avalonia.Base/Reactive/AnonymousObserver.cs
new file mode 100644
index 0000000000..c2e02ae879
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/AnonymousObserver.cs
@@ -0,0 +1,62 @@
+using System;
+using System.Threading.Tasks;
+
+namespace Avalonia.Reactive;
+
+internal class AnonymousObserver<T> : IObserver<T>
+{
+    private static readonly Action<Exception> ThrowsOnError = ex => throw ex;
+    private static readonly Action NoOpCompleted = () => { };  
+    private readonly Action<T> _onNext;
+    private readonly Action<Exception> _onError;
+    private readonly Action _onCompleted;
+
+    public AnonymousObserver(TaskCompletionSource<T> tcs)
+    {
+        if (tcs is null)
+        {
+            throw new ArgumentNullException(nameof(tcs));
+        }
+
+        _onNext = tcs.SetResult;
+        _onError = tcs.SetException;
+        _onCompleted = NoOpCompleted;
+    }
+    
+    public AnonymousObserver(Action<T> onNext, Action<Exception> onError, Action onCompleted)
+    {
+        _onNext = onNext ?? throw new ArgumentNullException(nameof(onNext));
+        _onError = onError ?? throw new ArgumentNullException(nameof(onError));
+        _onCompleted = onCompleted ?? throw new ArgumentNullException(nameof(onCompleted));
+    }
+
+    public AnonymousObserver(Action<T> onNext)
+        : this(onNext, ThrowsOnError, NoOpCompleted)
+    {
+    }
+
+    public AnonymousObserver(Action<T> onNext, Action<Exception> onError)
+        : this(onNext, onError, NoOpCompleted)
+    {
+    }
+
+    public AnonymousObserver(Action<T> onNext, Action onCompleted)
+        : this(onNext, ThrowsOnError, onCompleted)
+    {
+    }
+
+    public void OnCompleted()
+    {
+        _onCompleted.Invoke();
+    }
+
+    public void OnError(Exception error)
+    {
+        _onError.Invoke(error);
+    }
+
+    public void OnNext(T value)
+    {
+        _onNext.Invoke(value);
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/CombinedSubject.cs b/src/Avalonia.Base/Reactive/CombinedSubject.cs
new file mode 100644
index 0000000000..dc6153133d
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/CombinedSubject.cs
@@ -0,0 +1,23 @@
+using System;
+
+namespace Avalonia.Reactive;
+
+internal class CombinedSubject<T> : IAvaloniaSubject<T>
+{
+    private readonly IObserver<T> _observer;
+    private readonly IObservable<T> _observable;
+
+    public CombinedSubject(IObserver<T> observer, IObservable<T> observable)
+    {
+        _observer = observer;
+        _observable = observable;
+    }
+
+    public void OnCompleted() => _observer.OnCompleted();
+
+    public void OnError(Exception error) => _observer.OnError(error);
+
+    public void OnNext(T value) => _observer.OnNext(value);
+
+    public IDisposable Subscribe(IObserver<T> observer) => _observable.Subscribe(observer);
+}
diff --git a/src/Avalonia.Base/Reactive/CompositeDisposable.cs b/src/Avalonia.Base/Reactive/CompositeDisposable.cs
new file mode 100644
index 0000000000..4952686ad8
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/CompositeDisposable.cs
@@ -0,0 +1,427 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Threading;
+
+namespace Avalonia.Reactive;
+
+internal sealed class CompositeDisposable : ICollection<IDisposable>, IDisposable
+{
+    private readonly object _gate = new object();
+    private bool _disposed;
+    private List<IDisposable?> _disposables;
+    private int _count;
+    private const int ShrinkThreshold = 64;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CompositeDisposable"/> class with the specified number of disposables.
+    /// </summary>
+    /// <param name="capacity">The number of disposables that the new CompositeDisposable can initially store.</param>
+    /// <exception cref="ArgumentOutOfRangeException"><paramref name="capacity"/> is less than zero.</exception>
+    public CompositeDisposable(int capacity)
+    {
+        if (capacity < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(capacity));
+        }
+
+        _disposables = new List<IDisposable?>(capacity);
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CompositeDisposable"/> class from a group of disposables.
+    /// </summary>
+    /// <param name="disposables">Disposables that will be disposed together.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="disposables"/> is <c>null</c>.</exception>
+    /// <exception cref="ArgumentException">Any of the disposables in the <paramref name="disposables"/> collection is <c>null</c>.</exception>
+    public CompositeDisposable(params IDisposable[] disposables)
+    {
+        if (disposables == null)
+        {
+            throw new ArgumentNullException(nameof(disposables));
+        }
+
+        _disposables = ToList(disposables);
+
+        // _count can be read by other threads and thus should be properly visible
+        // also releases the _disposables contents so it becomes thread-safe
+        Volatile.Write(ref _count, _disposables.Count);
+    }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="CompositeDisposable"/> class from a group of disposables.
+    /// </summary>
+    /// <param name="disposables">Disposables that will be disposed together.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="disposables"/> is <c>null</c>.</exception>
+    /// <exception cref="ArgumentException">Any of the disposables in the <paramref name="disposables"/> collection is <c>null</c>.</exception>
+    public CompositeDisposable(IList<IDisposable> disposables)
+    {
+        if (disposables == null)
+        {
+            throw new ArgumentNullException(nameof(disposables));
+        }
+
+        _disposables = ToList(disposables);
+
+        // _count can be read by other threads and thus should be properly visible
+        // also releases the _disposables contents so it becomes thread-safe
+        Volatile.Write(ref _count, _disposables.Count);
+    }
+
+    private static List<IDisposable?> ToList(IEnumerable<IDisposable> disposables)
+    {
+        var capacity = disposables switch
+        {
+            IDisposable[] a => a.Length,
+            ICollection<IDisposable> c => c.Count,
+            _ => 12
+        };
+
+        var list = new List<IDisposable?>(capacity);
+
+        // do the copy and null-check in one step to avoid a
+        // second loop for just checking for null items
+        foreach (var d in disposables)
+        {
+            if (d == null)
+            {
+                throw new ArgumentException("Disposables can't contain null", nameof(disposables));
+            }
+
+            list.Add(d);
+        }
+
+        return list;
+    }
+
+    /// <summary>
+    /// Gets the number of disposables contained in the <see cref="CompositeDisposable"/>.
+    /// </summary>
+    public int Count => Volatile.Read(ref _count);
+
+    /// <summary>
+    /// Adds a disposable to the <see cref="CompositeDisposable"/> or disposes the disposable if the <see cref="CompositeDisposable"/> is disposed.
+    /// </summary>
+    /// <param name="item">Disposable to add.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="item"/> is <c>null</c>.</exception>
+    public void Add(IDisposable item)
+    {
+        if (item == null)
+        {
+            throw new ArgumentNullException(nameof(item));
+        }
+
+        lock (_gate)
+        {
+            if (!_disposed)
+            {
+                _disposables.Add(item);
+
+                // If read atomically outside the lock, it should be written atomically inside
+                // the plain read on _count is fine here because manipulation always happens
+                // from inside a lock.
+                Volatile.Write(ref _count, _count + 1);
+                return;
+            }
+        }
+
+        item.Dispose();
+    }
+
+    /// <summary>
+    /// Removes and disposes the first occurrence of a disposable from the <see cref="CompositeDisposable"/>.
+    /// </summary>
+    /// <param name="item">Disposable to remove.</param>
+    /// <returns>true if found; false otherwise.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="item"/> is <c>null</c>.</exception>
+    public bool Remove(IDisposable item)
+    {
+        if (item == null)
+        {
+            throw new ArgumentNullException(nameof(item));
+        }
+
+        lock (_gate)
+        {
+            // this composite was already disposed and if the item was in there
+            // it has been already removed/disposed
+            if (_disposed)
+            {
+                return false;
+            }
+
+            //
+            // List<T> doesn't shrink the size of the underlying array but does collapse the array
+            // by copying the tail one position to the left of the removal index. We don't need
+            // index-based lookup but only ordering for sequential disposal. So, instead of spending
+            // cycles on the Array.Copy imposed by Remove, we use a null sentinel value. We also
+            // do manual Swiss cheese detection to shrink the list if there's a lot of holes in it.
+            //
+
+            // read fields as infrequently as possible
+            var current = _disposables;
+
+            var i = current.IndexOf(item);
+            if (i < 0)
+            {
+                // not found, just return
+                return false;
+            }
+
+            current[i] = null;
+
+            if (current.Capacity > ShrinkThreshold && _count < current.Capacity / 2)
+            {
+                var fresh = new List<IDisposable?>(current.Capacity / 2);
+
+                foreach (var d in current)
+                {
+                    if (d != null)
+                    {
+                        fresh.Add(d);
+                    }
+                }
+
+                _disposables = fresh;
+            }
+
+            // make sure the Count property sees an atomic update
+            Volatile.Write(ref _count, _count - 1);
+        }
+
+        // if we get here, the item was found and removed from the list
+        // just dispose it and report success
+
+        item.Dispose();
+
+        return true;
+    }
+
+    /// <summary>
+    /// Disposes all disposables in the group and removes them from the group.
+    /// </summary>
+    public void Dispose()
+    {
+        List<IDisposable?>? currentDisposables = null;
+
+        lock (_gate)
+        {
+            if (!_disposed)
+            {
+                currentDisposables = _disposables;
+
+                // nulling out the reference is faster no risk to
+                // future Add/Remove because _disposed will be true
+                // and thus _disposables won't be touched again.
+                _disposables = null!; // NB: All accesses are guarded by _disposed checks.
+
+                Volatile.Write(ref _count, 0);
+                Volatile.Write(ref _disposed, true);
+            }
+        }
+
+        if (currentDisposables != null)
+        {
+            foreach (var d in currentDisposables)
+            {
+                d?.Dispose();
+            }
+        }
+    }
+
+    /// <summary>
+    /// Removes and disposes all disposables from the <see cref="CompositeDisposable"/>, but does not dispose the <see cref="CompositeDisposable"/>.
+    /// </summary>
+    public void Clear()
+    {
+        IDisposable?[] previousDisposables;
+
+        lock (_gate)
+        {
+            // disposed composites are always clear
+            if (_disposed)
+            {
+                return;
+            }
+
+            var current = _disposables;
+
+            previousDisposables = current.ToArray();
+            current.Clear();
+
+            Volatile.Write(ref _count, 0);
+        }
+
+        foreach (var d in previousDisposables)
+        {
+            d?.Dispose();
+        }
+    }
+
+    /// <summary>
+    /// Determines whether the <see cref="CompositeDisposable"/> contains a specific disposable.
+    /// </summary>
+    /// <param name="item">Disposable to search for.</param>
+    /// <returns>true if the disposable was found; otherwise, false.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="item"/> is <c>null</c>.</exception>
+    public bool Contains(IDisposable item)
+    {
+        if (item == null)
+        {
+            throw new ArgumentNullException(nameof(item));
+        }
+
+        lock (_gate)
+        {
+            if (_disposed)
+            {
+                return false;
+            }
+
+            return _disposables.Contains(item);
+        }
+    }
+
+    /// <summary>
+    /// Copies the disposables contained in the <see cref="CompositeDisposable"/> to an array, starting at a particular array index.
+    /// </summary>
+    /// <param name="array">Array to copy the contained disposables to.</param>
+    /// <param name="arrayIndex">Target index at which to copy the first disposable of the group.</param>
+    /// <exception cref="ArgumentNullException"><paramref name="array"/> is <c>null</c>.</exception>
+    /// <exception cref="ArgumentOutOfRangeException"><paramref name="arrayIndex"/> is less than zero. -or - <paramref name="arrayIndex"/> is larger than or equal to the array length.</exception>
+    public void CopyTo(IDisposable[] array, int arrayIndex)
+    {
+        if (array == null)
+        {
+            throw new ArgumentNullException(nameof(array));
+        }
+
+        if (arrayIndex < 0 || arrayIndex >= array.Length)
+        {
+            throw new ArgumentOutOfRangeException(nameof(arrayIndex));
+        }
+
+        lock (_gate)
+        {
+            // disposed composites are always empty
+            if (_disposed)
+            {
+                return;
+            }
+
+            if (arrayIndex + _count > array.Length)
+            {
+                // there is not enough space beyond arrayIndex 
+                // to accommodate all _count disposables in this composite
+                throw new ArgumentOutOfRangeException(nameof(arrayIndex));
+            }
+
+            var i = arrayIndex;
+
+            foreach (var d in _disposables)
+            {
+                if (d != null)
+                {
+                    array[i++] = d;
+                }
+            }
+        }
+    }
+
+    /// <summary>
+    /// Always returns false.
+    /// </summary>
+    public bool IsReadOnly => false;
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the <see cref="CompositeDisposable"/>.
+    /// </summary>
+    /// <returns>An enumerator to iterate over the disposables.</returns>
+    public IEnumerator<IDisposable> GetEnumerator()
+    {
+        lock (_gate)
+        {
+            if (_disposed || _count == 0)
+            {
+                return EmptyEnumerator;
+            }
+
+            // the copy is unavoidable but the creation
+            // of an outer IEnumerable is avoidable
+            return new CompositeEnumerator(_disposables.ToArray());
+        }
+    }
+
+    /// <summary>
+    /// Returns an enumerator that iterates through the <see cref="CompositeDisposable"/>.
+    /// </summary>
+    /// <returns>An enumerator to iterate over the disposables.</returns>
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    /// <summary>
+    /// Gets a value that indicates whether the object is disposed.
+    /// </summary>
+    public bool IsDisposed => Volatile.Read(ref _disposed);
+
+    /// <summary>
+    /// An empty enumerator for the <see cref="GetEnumerator"/>
+    /// method to avoid allocation on disposed or empty composites.
+    /// </summary>
+    private static readonly CompositeEnumerator EmptyEnumerator =
+        new CompositeEnumerator(Array.Empty<IDisposable?>());
+
+    /// <summary>
+    /// An enumerator for an array of disposables.
+    /// </summary>
+    private sealed class CompositeEnumerator : IEnumerator<IDisposable>
+    {
+        private readonly IDisposable?[] _disposables;
+        private int _index;
+
+        public CompositeEnumerator(IDisposable?[] disposables)
+        {
+            _disposables = disposables;
+            _index = -1;
+        }
+
+        public IDisposable Current => _disposables[_index]!; // NB: _index is only advanced to non-null positions.
+
+        object IEnumerator.Current => _disposables[_index]!;
+
+        public void Dispose()
+        {
+            // Avoid retention of the referenced disposables
+            // beyond the lifecycle of the enumerator.
+            // Not sure if this happens by default to
+            // generic array enumerators though.
+            var disposables = _disposables;
+            Array.Clear(disposables, 0, disposables.Length);
+        }
+
+        public bool MoveNext()
+        {
+            var disposables = _disposables;
+
+            for (;;)
+            {
+                var idx = ++_index;
+
+                if (idx >= disposables.Length)
+                {
+                    return false;
+                }
+
+                // inlined that filter for null elements
+                if (disposables[idx] != null)
+                {
+                    return true;
+                }
+            }
+        }
+
+        public void Reset()
+        {
+            _index = -1;
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/Disposable.cs b/src/Avalonia.Base/Reactive/Disposable.cs
new file mode 100644
index 0000000000..17b0d01db5
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/Disposable.cs
@@ -0,0 +1,98 @@
+using System;
+using System.Threading;
+
+namespace Avalonia.Reactive;
+
+/// <summary>
+/// Provides a set of static methods for creating <see cref="IDisposable"/> objects.
+/// </summary>
+internal static class Disposable
+{
+    /// <summary>
+    /// Represents a disposable that does nothing on disposal.
+    /// </summary>
+    private sealed class EmptyDisposable : IDisposable
+    {
+        public static readonly EmptyDisposable Instance = new();
+
+        private EmptyDisposable()
+        {
+        }
+
+        public void Dispose()
+        {
+            // no op
+        }
+    }
+    
+    internal sealed class AnonymousDisposable : IDisposable
+    {
+        private volatile Action? _dispose;
+        public AnonymousDisposable(Action dispose)
+        {
+            _dispose = dispose;
+        }
+        public bool IsDisposed => _dispose == null;
+        public void Dispose()
+        {
+            Interlocked.Exchange(ref _dispose, null)?.Invoke();
+        }
+    }
+
+    internal sealed class AnonymousDisposable<TState> : IDisposable
+    {
+        private TState _state;
+        private volatile Action<TState>? _dispose;
+
+        public AnonymousDisposable(TState state, Action<TState> dispose)
+        {
+            _state = state;
+            _dispose = dispose;
+        }
+
+        public bool IsDisposed => _dispose == null;
+        public void Dispose()
+        {
+            Interlocked.Exchange(ref _dispose, null)?.Invoke(_state);
+            _state = default!;
+        }
+    }
+
+    /// <summary>
+    /// Gets the disposable that does nothing when disposed.
+    /// </summary>
+    public static IDisposable Empty => EmptyDisposable.Instance;
+
+    /// <summary>
+    /// Creates a disposable object that invokes the specified action when disposed.
+    /// </summary>
+    /// <param name="dispose">Action to run during the first call to <see cref="IDisposable.Dispose"/>. The action is guaranteed to be run at most once.</param>
+    /// <returns>The disposable object that runs the given action upon disposal.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="dispose"/> is <c>null</c>.</exception>
+    public static IDisposable Create(Action dispose)
+    {
+        if (dispose == null)
+        {
+            throw new ArgumentNullException(nameof(dispose));
+        }
+
+        return new AnonymousDisposable(dispose);
+    }
+
+    /// <summary>
+    /// Creates a disposable object that invokes the specified action when disposed.
+    /// </summary>
+    /// <param name="state">The state to be passed to the action.</param>
+    /// <param name="dispose">Action to run during the first call to <see cref="IDisposable.Dispose"/>. The action is guaranteed to be run at most once.</param>
+    /// <returns>The disposable object that runs the given action upon disposal.</returns>
+    /// <exception cref="ArgumentNullException"><paramref name="dispose"/> is <c>null</c>.</exception>
+    public static IDisposable Create<TState>(TState state, Action<TState> dispose)
+    {
+        if (dispose == null)
+        {
+            throw new ArgumentNullException(nameof(dispose));
+        }
+
+        return new AnonymousDisposable<TState>(state, dispose);
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/DisposableMixin.cs b/src/Avalonia.Base/Reactive/DisposableMixin.cs
new file mode 100644
index 0000000000..478312fa47
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/DisposableMixin.cs
@@ -0,0 +1,37 @@
+using System;
+using Avalonia.Reactive;
+
+namespace Avalonia.Reactive;
+
+/// <summary>
+/// Extension methods associated with the IDisposable interface.
+/// </summary>
+internal static class DisposableMixin
+{
+    /// <summary>
+    /// Ensures the provided disposable is disposed with the specified <see cref="CompositeDisposable"/>.
+    /// </summary>
+    /// <typeparam name="T">
+    /// The type of the disposable.
+    /// </typeparam>
+    /// <param name="item">
+    /// The disposable we are going to want to be disposed by the CompositeDisposable.
+    /// </param>
+    /// <param name="compositeDisposable">
+    /// The <see cref="CompositeDisposable"/> to which <paramref name="item"/> will be added.
+    /// </param>
+    /// <returns>
+    /// The disposable.
+    /// </returns>
+    public static T DisposeWith<T>(this T item, CompositeDisposable compositeDisposable)
+        where T : IDisposable
+    {
+        if (compositeDisposable is null)
+        {
+            throw new ArgumentNullException(nameof(compositeDisposable));
+        }
+
+        compositeDisposable.Add(item);
+        return item;
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/IAvaloniaSubject.cs b/src/Avalonia.Base/Reactive/IAvaloniaSubject.cs
new file mode 100644
index 0000000000..272e2190b8
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/IAvaloniaSubject.cs
@@ -0,0 +1,8 @@
+using System;
+
+namespace Avalonia.Reactive;
+
+internal interface IAvaloniaSubject<T> : IObserver<T>, IObservable<T> /*, ISubject<T> */
+{
+    
+}
diff --git a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
index 9a3ab89b62..263109972f 100644
--- a/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
+++ b/src/Avalonia.Base/Reactive/LightweightObservableBase.cs
@@ -1,7 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive;
-using System.Reactive.Disposables;
 using System.Threading;
 using Avalonia.Threading;
 
@@ -12,7 +10,7 @@ namespace Avalonia.Reactive
     /// </summary>
     /// <typeparam name="T">The observable type.</typeparam>
     /// <remarks>
-    /// <see cref="ObservableBase{T}"/> is rather heavyweight in terms of allocations and memory
+    /// ObservableBase{T} is rather heavyweight in terms of allocations and memory
     /// usage. This class provides a more lightweight base for some internal observable types
     /// in the Avalonia framework.
     /// </remarks>
@@ -21,11 +19,13 @@ namespace Avalonia.Reactive
         private Exception? _error;
         private List<IObserver<T>>? _observers = new List<IObserver<T>>();
 
+        public bool HasObservers => _observers?.Count > 0;
+        
         public IDisposable Subscribe(IObserver<T> observer)
         {
             _ = observer ?? throw new ArgumentNullException(nameof(observer));
 
-            Dispatcher.UIThread.VerifyAccess();
+            //Dispatcher.UIThread.VerifyAccess();
 
             var first = false;
 
diff --git a/src/Avalonia.Base/Reactive/LightweightSubject.cs b/src/Avalonia.Base/Reactive/LightweightSubject.cs
new file mode 100644
index 0000000000..5663fd66d3
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/LightweightSubject.cs
@@ -0,0 +1,30 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Runtime.InteropServices;
+using System.Threading;
+using Avalonia.Threading;
+
+namespace Avalonia.Reactive;
+
+internal class LightweightSubject<T> : LightweightObservableBase<T>, IAvaloniaSubject<T>
+{
+    public void OnCompleted()
+    {
+        PublishCompleted();
+    }
+
+    public void OnError(Exception error)
+    {
+        PublishError(error);
+    }
+
+    public void OnNext(T value)
+    {
+        PublishNext(value);
+    }
+
+    protected override void Initialize() { }
+
+    protected override void Deinitialize() { }
+}
diff --git a/src/Avalonia.Base/Reactive/Observable.cs b/src/Avalonia.Base/Reactive/Observable.cs
new file mode 100644
index 0000000000..5191efa910
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/Observable.cs
@@ -0,0 +1,238 @@
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using Avalonia.Reactive.Operators;
+using Avalonia.Threading;
+
+namespace Avalonia.Reactive;
+
+/// <summary>
+/// Provides common observable methods as a replacement for the Rx framework.
+/// </summary>
+internal static class Observable
+{
+    public static IObservable<TSource> Create<TSource>(Func<IObserver<TSource>, IDisposable> subscribe)
+    {
+        return new CreateWithDisposableObservable<TSource>(subscribe);
+    }
+
+    public static IDisposable Subscribe<T>(this IObservable<T> source, Action<T> action)
+    {
+        return source.Subscribe(new AnonymousObserver<T>(action));
+    }
+
+    public static IObservable<TResult> Select<TSource, TResult>(this IObservable<TSource> source, Func<TSource, TResult> selector)
+    {
+        return Create<TResult>(obs =>
+        {
+            return source.Subscribe(new AnonymousObserver<TSource>(
+                input =>
+                {
+                    TResult value;
+                    try
+                    {
+                        value = selector(input);
+                    }
+                    catch (Exception ex)
+                    {
+                        obs.OnError(ex);
+                        return;
+                    }
+
+                    obs.OnNext(value);
+                }, obs.OnError, obs.OnCompleted));
+        });
+    }
+    
+    public static IObservable<TSource> Where<TSource>(this IObservable<TSource> source, Func<TSource, bool> predicate)
+    {
+        return Create<TSource>(obs =>
+        {
+            return source.Subscribe(new AnonymousObserver<TSource>(
+                input =>
+                {
+                    bool shouldRun;
+                    try
+                    {
+                        shouldRun = predicate(input);
+                    }
+                    catch (Exception ex)
+                    {
+                        obs.OnError(ex);
+                        return;
+                    }
+                    if (shouldRun)
+                    {
+                        obs.OnNext(input);
+                    }
+                }, obs.OnError, obs.OnCompleted));
+        });
+    }
+
+    public static IObservable<TSource> Switch<TSource>(
+        this IObservable<IObservable<TSource>> sources)
+    {
+        return new Switch<TSource>(sources);
+    }
+
+    public static IObservable<TResult> CombineLatest<TFirst, TSecond, TResult>(
+        this IObservable<TFirst> first, IObservable<TSecond> second,
+        Func<TFirst, TSecond, TResult> resultSelector)
+    {
+        return new CombineLatest<TFirst, TSecond, TResult>(first, second, resultSelector);
+    }
+    
+    public static IObservable<TInput[]> CombineLatest<TInput>(
+        this IEnumerable<IObservable<TInput>> inputs)
+    {
+        return new CombineLatest<TInput, TInput[]>(inputs, items => items);
+    }
+
+    public static IObservable<T> Skip<T>(this IObservable<T> source, int skipCount)
+    {
+        if (skipCount <= 0)
+        {
+            throw new ArgumentException("Skip count must be bigger than zero", nameof(skipCount));
+        }
+
+        return Create<T>(obs =>
+        {
+            var remaining = skipCount;
+            return source.Subscribe(new AnonymousObserver<T>(
+                input =>
+                {
+                    if (remaining <= 0)
+                    {
+                        obs.OnNext(input);
+                    }
+                    else
+                    {
+                        remaining--;
+                    }
+                }, obs.OnError, obs.OnCompleted));
+        });
+    }
+    
+    public static IObservable<T> Take<T>(this IObservable<T> source, int takeCount)
+    {
+        if (takeCount <= 0)
+        {
+            return Empty<T>();
+        }
+
+        return Create<T>(obs =>
+        {
+            var remaining = takeCount;
+            IDisposable? sub = null;
+            sub = source.Subscribe(new AnonymousObserver<T>(
+                input =>
+                {
+                    if (remaining > 0)
+                    {
+                        --remaining;
+                        obs.OnNext(input);
+
+                        if (remaining == 0)
+                        {
+                            sub?.Dispose();
+                            obs.OnCompleted();
+                        }
+                    }
+                }, obs.OnError, obs.OnCompleted));
+            return sub;
+        });
+    }
+
+    public static IObservable<EventArgs> FromEventPattern(Action<EventHandler> addHandler, Action<EventHandler> removeHandler)
+    {
+        return Create<EventArgs>(observer =>
+        {
+            var handler = new Action<EventArgs>(observer.OnNext);
+            var converted = new EventHandler((_, args) => handler(args));
+            addHandler(converted);
+
+            return Disposable.Create(() => removeHandler(converted));
+        });
+    }
+    
+    public static IObservable<T> Return<T>(T value)
+    {
+        return new ReturnImpl<T>(value);
+    }
+    
+    public static IObservable<T> Empty<T>()
+    {
+        return EmptyImpl<T>.Instance;
+    }
+        
+    /// <summary>
+    /// Returns an observable that fires once with the specified value and never completes.
+    /// </summary>
+    /// <typeparam name="T">The type of the value.</typeparam>
+    /// <param name="value">The value.</param>
+    /// <returns>The observable.</returns>
+    public static IObservable<T> SingleValue<T>(T value)
+    {
+        return new SingleValueImpl<T>(value);
+    }
+ 
+    private sealed class SingleValueImpl<T> : IObservable<T>
+    {
+        private readonly T _value;
+
+        public SingleValueImpl(T value)
+        {
+            _value = value;
+        }
+        public IDisposable Subscribe(IObserver<T> observer)
+        {
+            observer.OnNext(_value);
+            return Disposable.Empty;
+        }
+    }
+    
+    private sealed class ReturnImpl<T> : IObservable<T>
+    {
+        private readonly T _value;
+
+        public ReturnImpl(T value)
+        {
+            _value = value;
+        }
+        public IDisposable Subscribe(IObserver<T> observer)
+        {
+            observer.OnNext(_value);
+            observer.OnCompleted();
+            return Disposable.Empty;
+        }
+    }
+    
+    internal sealed class EmptyImpl<TResult> : IObservable<TResult>
+    {
+        internal static readonly IObservable<TResult> Instance = new EmptyImpl<TResult>();
+
+        private EmptyImpl() { }
+
+        public IDisposable Subscribe(IObserver<TResult> observer)
+        {
+            observer.OnCompleted();
+            return Disposable.Empty;
+        }
+    }
+    
+    private sealed class CreateWithDisposableObservable<TSource> : IObservable<TSource>
+    {
+        private readonly Func<IObserver<TSource>, IDisposable> _subscribe;
+
+        public CreateWithDisposableObservable(Func<IObserver<TSource>, IDisposable> subscribe)
+        {
+            _subscribe = subscribe;
+        }
+
+        public IDisposable Subscribe(IObserver<TSource> observer)
+        {
+            return _subscribe(observer);
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/ObservableEx.cs b/src/Avalonia.Base/Reactive/ObservableEx.cs
deleted file mode 100644
index 1cea568c88..0000000000
--- a/src/Avalonia.Base/Reactive/ObservableEx.cs
+++ /dev/null
@@ -1,37 +0,0 @@
-using System;
-using System.Reactive.Disposables;
-
-namespace Avalonia.Reactive
-{
-    /// <summary>
-    /// Provides common observable methods not found in standard Rx framework.
-    /// </summary>
-    public static class ObservableEx
-    {
-        /// <summary>
-        /// Returns an observable that fires once with the specified value and never completes.
-        /// </summary>
-        /// <typeparam name="T">The type of the value.</typeparam>
-        /// <param name="value">The value.</param>
-        /// <returns>The observable.</returns>
-        public static IObservable<T> SingleValue<T>(T value)
-        {
-            return new SingleValueImpl<T>(value);
-        }
- 
-        private class SingleValueImpl<T> : IObservable<T>
-        {
-            private T _value;
-
-            public SingleValueImpl(T value)
-            {
-                _value = value;
-            }
-            public IDisposable Subscribe(IObserver<T> observer)
-            {
-                observer.OnNext(_value);
-                return Disposable.Empty;
-            }
-        }
-    }
-}
diff --git a/src/Avalonia.Base/Reactive/Operators/CombineLatest.cs b/src/Avalonia.Base/Reactive/Operators/CombineLatest.cs
new file mode 100644
index 0000000000..aa95ceec35
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/Operators/CombineLatest.cs
@@ -0,0 +1,374 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Linq;
+
+namespace Avalonia.Reactive.Operators;
+
+// Code based on https://github.com/dotnet/reactive/blob/main/Rx.NET/Source/src/System.Reactive/Linq/Observable/CombineLatest.cs
+
+internal sealed class CombineLatest<TFirst, TSecond, TResult> : IObservable<TResult>
+{
+    private readonly IObservable<TFirst> _first;
+    private readonly IObservable<TSecond> _second;
+    private readonly Func<TFirst, TSecond, TResult> _resultSelector;
+
+    public CombineLatest(IObservable<TFirst> first, IObservable<TSecond> second,
+        Func<TFirst, TSecond, TResult> resultSelector)
+    {
+        _first = first;
+        _second = second;
+        _resultSelector = resultSelector;
+    }
+
+    public IDisposable Subscribe(IObserver<TResult> observer)
+    {
+        var sink = new _(_resultSelector, observer);
+        sink.Run(_first, _second);
+        return sink;
+    }
+
+    internal sealed class _ : IdentitySink<TResult>
+    {
+        private readonly Func<TFirst, TSecond, TResult> _resultSelector;
+        private readonly object _gate = new object();
+
+        public _(Func<TFirst, TSecond, TResult> resultSelector, IObserver<TResult> observer)
+            : base(observer)
+        {
+            _resultSelector = resultSelector;
+            _firstDisposable = null!;
+            _secondDisposable = null!;
+        }
+
+        private IDisposable _firstDisposable;
+        private IDisposable _secondDisposable;
+
+        public void Run(IObservable<TFirst> first, IObservable<TSecond> second)
+        {
+            var fstO = new FirstObserver(this);
+            var sndO = new SecondObserver(this);
+
+            fstO.SetOther(sndO);
+            sndO.SetOther(fstO);
+
+            _firstDisposable = first.Subscribe(fstO);
+            _secondDisposable = second.Subscribe(sndO);
+        }
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _firstDisposable.Dispose();
+                _secondDisposable.Dispose();
+            }
+
+            base.Dispose(disposing);
+        }
+
+        private sealed class FirstObserver : IObserver<TFirst>
+        {
+            private readonly _ _parent;
+            private SecondObserver _other;
+
+            public FirstObserver(_ parent)
+            {
+                _parent = parent;
+                _other = default!; // NB: Will be set by SetOther.
+            }
+
+            public void SetOther(SecondObserver other) { _other = other; }
+
+            public bool HasValue { get; private set; }
+            public TFirst? Value { get; private set; }
+            public bool Done { get; private set; }
+
+            public void OnNext(TFirst value)
+            {
+                lock (_parent._gate)
+                {
+                    HasValue = true;
+                    Value = value;
+
+                    if (_other.HasValue)
+                    {
+                        TResult res;
+                        try
+                        {
+                            res = _parent._resultSelector(value, _other.Value!);
+                        }
+                        catch (Exception ex)
+                        {
+                            _parent.ForwardOnError(ex);
+                            return;
+                        }
+
+                        _parent.ForwardOnNext(res);
+                    }
+                    else if (_other.Done)
+                    {
+                        _parent.ForwardOnCompleted();
+                    }
+                }
+            }
+
+            public void OnError(Exception error)
+            {
+                lock (_parent._gate)
+                {
+                    _parent.ForwardOnError(error);
+                }
+            }
+
+            public void OnCompleted()
+            {
+                lock (_parent._gate)
+                {
+                    Done = true;
+
+                    if (_other.Done)
+                    {
+                        _parent.ForwardOnCompleted();
+                    }
+                    else
+                    {
+                        _parent._firstDisposable.Dispose();
+                    }
+                }
+            }
+        }
+
+        private sealed class SecondObserver : IObserver<TSecond>
+        {
+            private readonly _ _parent;
+            private FirstObserver _other;
+
+            public SecondObserver(_ parent)
+            {
+                _parent = parent;
+                _other = default!; // NB: Will be set by SetOther.
+            }
+
+            public void SetOther(FirstObserver other) { _other = other; }
+
+            public bool HasValue { get; private set; }
+            public TSecond? Value { get; private set; }
+            public bool Done { get; private set; }
+
+            public void OnNext(TSecond value)
+            {
+                lock (_parent._gate)
+                {
+                    HasValue = true;
+                    Value = value;
+
+                    if (_other.HasValue)
+                    {
+                        TResult res;
+                        try
+                        {
+                            res = _parent._resultSelector(_other.Value!, value);
+                        }
+                        catch (Exception ex)
+                        {
+                            _parent.ForwardOnError(ex);
+                            return;
+                        }
+
+                        _parent.ForwardOnNext(res);
+                    }
+                    else if (_other.Done)
+                    {
+                        _parent.ForwardOnCompleted();
+                    }
+                }
+            }
+
+            public void OnError(Exception error)
+            {
+                lock (_parent._gate)
+                {
+                    _parent.ForwardOnError(error);
+                }
+            }
+
+            public void OnCompleted()
+            {
+                lock (_parent._gate)
+                {
+                    Done = true;
+
+                    if (_other.Done)
+                    {
+                        _parent.ForwardOnCompleted();
+                    }
+                    else
+                    {
+                        _parent._secondDisposable.Dispose();
+                    }
+                }
+            }
+        }
+    }
+}
+
+internal sealed class CombineLatest<TSource, TResult> : IObservable<TResult>
+{
+    private readonly IEnumerable<IObservable<TSource>> _sources;
+    private readonly Func<TSource[], TResult> _resultSelector;
+
+    public CombineLatest(IEnumerable<IObservable<TSource>> sources, Func<TSource[], TResult> resultSelector)
+    {
+        _sources = sources;
+        _resultSelector = resultSelector;
+    }
+
+    public IDisposable Subscribe(IObserver<TResult> observer)
+    {
+        var sink = new _(_resultSelector, observer);
+        sink.Run(_sources);
+        return sink;
+    }
+
+    internal sealed class _ : IdentitySink<TResult>
+    {
+        private readonly object _gate = new object();
+        private readonly Func<TSource[], TResult> _resultSelector;
+
+        public _(Func<TSource[], TResult> resultSelector, IObserver<TResult> observer)
+            : base(observer)
+        {
+            _resultSelector = resultSelector;
+
+            // NB: These will be set in Run before getting used.
+            _hasValue = null!;
+            _values = null!;
+            _isDone = null!;
+            _subscriptions = null!;
+        }
+
+        private bool[] _hasValue;
+        private bool _hasValueAll;
+        private TSource[] _values;
+        private bool[] _isDone;
+        private IDisposable[] _subscriptions;
+
+        public void Run(IEnumerable<IObservable<TSource>> sources)
+        {
+            var srcs = sources.ToArray();
+
+            var N = srcs.Length;
+
+            _hasValue = new bool[N];
+            _hasValueAll = false;
+
+            _values = new TSource[N];
+
+            _isDone = new bool[N];
+
+            _subscriptions = new IDisposable[N];
+
+            for (var i = 0; i < N; i++)
+            {
+                var j = i;
+
+                var o = new SourceObserver(this, j);
+                _subscriptions[j] = o;
+
+                o.Disposable = srcs[j].Subscribe(o);
+            }
+
+            SetUpstream(new CompositeDisposable(_subscriptions));
+        }
+
+        private void OnNext(int index, TSource value)
+        {
+            lock (_gate)
+            {
+                _values[index] = value;
+
+                _hasValue[index] = true;
+
+                if (_hasValueAll || (_hasValueAll = _hasValue.All(v => v)))
+                {
+                    TResult res;
+                    try
+                    {
+                        res = _resultSelector(_values);
+                    }
+                    catch (Exception ex)
+                    {
+                        ForwardOnError(ex);
+                        return;
+                    }
+
+                    ForwardOnNext(res);
+                }
+                else if (_isDone.Where((_, i) => i != index).All(d => d))
+                {
+                    ForwardOnCompleted();
+                }
+            }
+        }
+
+        private new void OnError(Exception error)
+        {
+            lock (_gate)
+            {
+                ForwardOnError(error);
+            }
+        }
+
+        private void OnCompleted(int index)
+        {
+            lock (_gate)
+            {
+                _isDone[index] = true;
+
+                if (_isDone.All(d => d))
+                {
+                    ForwardOnCompleted();
+                }
+                else
+                {
+                    _subscriptions[index].Dispose();
+                }
+            }
+        }
+
+        private sealed class SourceObserver : IObserver<TSource>, IDisposable
+        {
+            private readonly _ _parent;
+            private readonly int _index;
+
+            public SourceObserver(_ parent, int index)
+            {
+                _parent = parent;
+                _index = index;
+            }
+
+            public IDisposable? Disposable { get; set; }
+
+            public void OnNext(TSource value)
+            {
+                _parent.OnNext(_index, value);
+            }
+
+            public void OnError(Exception error)
+            {
+                _parent.OnError(error);
+            }
+
+            public void OnCompleted()
+            {
+                _parent.OnCompleted(_index);
+            }
+
+            public void Dispose()
+            {
+                Disposable?.Dispose();
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/Operators/Sink.cs b/src/Avalonia.Base/Reactive/Operators/Sink.cs
new file mode 100644
index 0000000000..7a5d39788e
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/Operators/Sink.cs
@@ -0,0 +1,109 @@
+using System;
+using System.Threading;
+
+namespace Avalonia.Reactive.Operators;
+
+internal abstract class Sink<TTarget> : IDisposable
+{
+    private IDisposable? _upstream;
+    private volatile IObserver<TTarget> _observer;
+
+    protected Sink(IObserver<TTarget> observer)
+    {
+        _observer = observer;
+    }
+
+    public void Dispose()
+    {
+        Dispose(true);
+    }
+
+    /// <summary>
+    /// Override this method to dispose additional resources.
+    /// The method is guaranteed to be called at most once.
+    /// </summary>
+    /// <param name="disposing">If true, the method was called from <see cref="Dispose()"/>.</param>
+    protected virtual void Dispose(bool disposing)
+    {
+        //Calling base.Dispose(true) is not a proper disposal, so we can omit the assignment here.
+        //Sink is internal so this can pretty much be enforced.
+        //_observer = NopObserver<TTarget>.Instance;
+
+        _upstream?.Dispose();
+    }
+
+    public void ForwardOnNext(TTarget value)
+    {
+        _observer.OnNext(value);
+    }
+
+    public void ForwardOnCompleted()
+    {
+        _observer.OnCompleted();
+        Dispose();
+    }
+
+    public void ForwardOnError(Exception error)
+    {
+        _observer.OnError(error);
+        Dispose();
+    }
+
+    protected void SetUpstream(IDisposable upstream)
+    {
+        _upstream = upstream;
+    }
+
+    protected void DisposeUpstream()
+    {
+        _upstream?.Dispose();
+    }
+}
+
+internal abstract class Sink<TSource, TTarget> : Sink<TTarget>, IObserver<TSource>
+{
+    protected Sink(IObserver<TTarget> observer) : base(observer)
+    {
+    }
+
+    public virtual void Run(IObservable<TSource> source)
+    {
+        SetUpstream(source.Subscribe(this));
+    }
+
+    public abstract void OnNext(TSource value);
+
+    public virtual void OnError(Exception error) => ForwardOnError(error);
+
+    public virtual void OnCompleted() => ForwardOnCompleted();
+
+    public IObserver<TTarget> GetForwarder() => new _(this);
+
+    private sealed class _ : IObserver<TTarget>
+    {
+        private readonly Sink<TSource, TTarget> _forward;
+
+        public _(Sink<TSource, TTarget> forward)
+        {
+            _forward = forward;
+        }
+
+        public void OnNext(TTarget value) => _forward.ForwardOnNext(value);
+
+        public void OnError(Exception error) => _forward.ForwardOnError(error);
+
+        public void OnCompleted() => _forward.ForwardOnCompleted();
+    }
+}
+
+internal abstract class IdentitySink<T> : Sink<T, T>
+{
+    protected IdentitySink(IObserver<T> observer) : base(observer)
+    {
+    }
+
+    public override void OnNext(T value)
+    {
+        ForwardOnNext(value);
+    }
+}
diff --git a/src/Avalonia.Base/Reactive/Operators/Switch.cs b/src/Avalonia.Base/Reactive/Operators/Switch.cs
new file mode 100644
index 0000000000..bc849c499c
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/Operators/Switch.cs
@@ -0,0 +1,144 @@
+using System;
+
+namespace Avalonia.Reactive.Operators;
+
+// Code based on https://github.com/dotnet/reactive/blob/main/Rx.NET/Source/src/System.Reactive/Linq/Observable/Switch.cs
+
+internal sealed class Switch<TSource> : IObservable<TSource>
+{
+    private readonly IObservable<IObservable<TSource>> _sources;
+
+    public Switch(IObservable<IObservable<TSource>> sources)
+    {
+        _sources = sources;
+    }
+
+    public IDisposable Subscribe(IObserver<TSource> observer)
+    {
+        return _sources.Subscribe(new _(observer));
+    }
+
+    internal sealed class _ : Sink<IObservable<TSource>, TSource>
+    {
+        private readonly object _gate = new object();
+
+        public _(IObserver<TSource> observer)
+            : base(observer)
+        {
+        }
+
+        private IDisposable? _innerSerialDisposable;
+        private bool _isStopped;
+        private ulong _latest;
+        private bool _hasLatest;
+
+        protected override void Dispose(bool disposing)
+        {
+            if (disposing)
+            {
+                _innerSerialDisposable?.Dispose();
+            }
+
+            base.Dispose(disposing);
+        }
+
+        public override void OnNext(IObservable<TSource> value)
+        {
+            ulong id;
+
+            lock (_gate)
+            {
+                id = unchecked(++_latest);
+                _hasLatest = true;
+            }
+
+            var innerObserver = new InnerObserver(this, id);
+
+            _innerSerialDisposable = innerObserver;
+            innerObserver.Disposable = value.Subscribe(innerObserver);
+        }
+
+        public override void OnError(Exception error)
+        {
+            lock (_gate)
+            {
+                ForwardOnError(error);
+            }
+        }
+
+        public override void OnCompleted()
+        {
+            lock (_gate)
+            {
+                DisposeUpstream();
+
+                _isStopped = true;
+                if (!_hasLatest)
+                {
+                    ForwardOnCompleted();
+                }
+            }
+        }
+
+        private sealed class InnerObserver : IObserver<TSource>, IDisposable
+        {
+            private readonly _ _parent;
+            private readonly ulong _id;
+
+            public InnerObserver(_ parent, ulong id)
+            {
+                _parent = parent;
+                _id = id;
+            }
+
+            public IDisposable? Disposable { get; set; }
+
+            public void OnNext(TSource value)
+            {
+                lock (_parent._gate)
+                {
+                    if (_parent._latest == _id)
+                    {
+                        _parent.ForwardOnNext(value);
+                    }
+                }
+            }
+
+            public void OnError(Exception error)
+            {
+                lock (_parent._gate)
+                {
+                    Dispose();
+
+                    if (_parent._latest == _id)
+                    {
+                        _parent.ForwardOnError(error);
+                    }
+                }
+            }
+
+            public void OnCompleted()
+            {
+                lock (_parent._gate)
+                {
+                    Dispose();
+
+                    if (_parent._latest == _id)
+                    {
+                        _parent._hasLatest = false;
+
+                        if (_parent._isStopped)
+                        {
+                            _parent.ForwardOnCompleted();
+                        }
+                    }
+                }
+            }
+
+            public void Dispose()
+            {
+                Disposable?.Dispose();
+            }
+        }
+    }
+}
diff --git a/src/Avalonia.Base/Rendering/PlatformRenderInterfaceContextManager.cs b/src/Avalonia.Base/Rendering/PlatformRenderInterfaceContextManager.cs
index 198b36564a..261a39fa09 100644
--- a/src/Avalonia.Base/Rendering/PlatformRenderInterfaceContextManager.cs
+++ b/src/Avalonia.Base/Rendering/PlatformRenderInterfaceContextManager.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using Avalonia.Metadata;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 
 namespace Avalonia.Rendering;
 
diff --git a/src/Avalonia.Base/Rendering/SceneGraph/VisualNode.cs b/src/Avalonia.Base/Rendering/SceneGraph/VisualNode.cs
index a991f2f657..6e05bf8631 100644
--- a/src/Avalonia.Base/Rendering/SceneGraph/VisualNode.cs
+++ b/src/Avalonia.Base/Rendering/SceneGraph/VisualNode.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Utilities;
diff --git a/src/Avalonia.Base/Rendering/UiThreadRenderTimer.cs b/src/Avalonia.Base/Rendering/UiThreadRenderTimer.cs
index dd6cf7ad15..1bbf804b5f 100644
--- a/src/Avalonia.Base/Rendering/UiThreadRenderTimer.cs
+++ b/src/Avalonia.Base/Rendering/UiThreadRenderTimer.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Diagnostics;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Threading;
 
 namespace Avalonia.Rendering
diff --git a/src/Avalonia.Base/Styling/StyleInstance.cs b/src/Avalonia.Base/Styling/StyleInstance.cs
index ca602167c0..61cb31c6d0 100644
--- a/src/Avalonia.Base/Styling/StyleInstance.cs
+++ b/src/Avalonia.Base/Styling/StyleInstance.cs
@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Subjects;
 using Avalonia.Animation;
 using Avalonia.Data;
 using Avalonia.PropertyStore;
+using Avalonia.Reactive;
 using Avalonia.Styling.Activators;
 
 namespace Avalonia.Styling
@@ -24,7 +24,7 @@ namespace Avalonia.Styling
         private bool _isActive;
         private List<ISetterInstance>? _setters;
         private List<IAnimation>? _animations;
-        private Subject<bool>? _animationTrigger;
+        private LightweightSubject<bool>? _animationTrigger;
 
         public StyleInstance(
             IStyle style,
@@ -67,7 +67,7 @@ namespace Avalonia.Styling
         {
             if (_animations is not null && control is Animatable animatable)
             {
-                _animationTrigger ??= new Subject<bool>();
+                _animationTrigger ??= new LightweightSubject<bool>();
                 foreach (var animation in _animations)
                     animation.Apply(animatable, null, _animationTrigger);
 
diff --git a/src/Avalonia.Base/Threading/DispatcherTimer.cs b/src/Avalonia.Base/Threading/DispatcherTimer.cs
index 0c25d89722..f83e4e860e 100644
--- a/src/Avalonia.Base/Threading/DispatcherTimer.cs
+++ b/src/Avalonia.Base/Threading/DispatcherTimer.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Platform;
 
 namespace Avalonia.Threading
diff --git a/src/Avalonia.Base/Utilities/IWeakSubscriber.cs b/src/Avalonia.Base/Utilities/IWeakSubscriber.cs
deleted file mode 100644
index 2a5b8d39c5..0000000000
--- a/src/Avalonia.Base/Utilities/IWeakSubscriber.cs
+++ /dev/null
@@ -1,18 +0,0 @@
-using System;
-
-namespace Avalonia.Utilities
-{
-    /// <summary>
-    /// Defines a listener to a event subscribed vis the <see cref="WeakObservable"/>.
-    /// </summary>
-    /// <typeparam name="T">The type of the event arguments.</typeparam>
-    public interface IWeakSubscriber<T> where T : EventArgs
-    {
-        /// <summary>
-        /// Invoked when the subscribed event is raised.
-        /// </summary>
-        /// <param name="sender">The event sender.</param>
-        /// <param name="e">The event arguments.</param>
-        void OnEvent(object? sender, T e);
-    }
-}
diff --git a/src/Avalonia.Base/Utilities/WeakObservable.cs b/src/Avalonia.Base/Utilities/WeakObservable.cs
deleted file mode 100644
index e1c350d539..0000000000
--- a/src/Avalonia.Base/Utilities/WeakObservable.cs
+++ /dev/null
@@ -1,60 +0,0 @@
-using System;
-using System.Reactive;
-using System.Reactive.Linq;
-
-namespace Avalonia.Utilities
-{
-    /// <summary>
-    /// Provides extension methods for working with weak event handlers.
-    /// </summary>
-    public static class WeakObservable
-    {
-
-        private class Handler<TEventArgs> 
-            : IWeakSubscriber<TEventArgs>,
-                IWeakEventSubscriber<TEventArgs> where TEventArgs : EventArgs
-        {
-            private IObserver<EventPattern<object, TEventArgs>> _observer;
-
-            public Handler(IObserver<EventPattern<object, TEventArgs>> observer)
-            {
-                _observer = observer;
-            }
-
-            public void OnEvent(object? sender, TEventArgs e)
-            {
-                _observer.OnNext(new EventPattern<object, TEventArgs>(sender, e));
-            }
-
-            public void OnEvent(object? sender, WeakEvent ev, TEventArgs e)
-            {
-                _observer.OnNext(new EventPattern<object, TEventArgs>(sender, e));
-            }
-        }
-        
-        /// <summary>
-        /// Converts a WeakEvent conforming to the standard .NET event pattern into an observable
-        /// sequence, subscribing weakly.
-        /// </summary>
-        /// <typeparam name="TTarget">The type of target.</typeparam>
-        /// <typeparam name="TEventArgs">The type of the event args.</typeparam>
-        /// <param name="target">Object instance that exposes the event to convert.</param>
-        /// <param name="ev">The weak event to convert.</param>
-        /// <returns></returns>
-        public static IObservable<EventPattern<object, TEventArgs>> FromEventPattern<TTarget, TEventArgs>(
-            TTarget target, WeakEvent<TTarget, TEventArgs> ev)
-            where TEventArgs : EventArgs where TTarget : class
-        {
-            _ = target ?? throw new ArgumentNullException(nameof(target));
-            _ = ev ?? throw new ArgumentNullException(nameof(ev));
-
-            return Observable.Create<EventPattern<object, TEventArgs>>(observer =>
-            {
-                var handler = new Handler<TEventArgs>(observer);
-                ev.Subscribe(target, handler);
-                return () => ev.Unsubscribe(target, handler);
-            }).Publish().RefCount();
-        }
-
-    }
-}
diff --git a/src/Avalonia.Base/Visual.cs b/src/Avalonia.Base/Visual.cs
index ddaea01b05..5ff887e339 100644
--- a/src/Avalonia.Base/Visual.cs
+++ b/src/Avalonia.Base/Visual.cs
@@ -11,6 +11,7 @@ using Avalonia.Logging;
 using Avalonia.LogicalTree;
 using Avalonia.Media;
 using Avalonia.Metadata;
+using Avalonia.Reactive;
 using Avalonia.Rendering;
 using Avalonia.Rendering.Composition;
 using Avalonia.Rendering.Composition.Server;
@@ -384,52 +385,55 @@ namespace Avalonia
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : Visual
         {
-            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                if (e.Sender is T sender)
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e =>
                 {
-                    sender.InvalidateVisual();
-                }
-            }
-
-            static void InvalidateAndSubscribe(AvaloniaPropertyChangedEventArgs e)
-            {
-                if (e.Sender is T sender)
+                    if (e.Sender is T sender)
+                    {
+                        sender.InvalidateVisual();
+                    }
+                });
+            
+            
+            var invalidateAndSubscribeObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e =>
                 {
-                    if (e.OldValue is IAffectsRender oldValue)
+                    if (e.Sender is T sender)
                     {
-                        if (sender._affectsRenderWeakSubscriber != null)
+                        if (e.OldValue is IAffectsRender oldValue)
                         {
-                            InvalidatedWeakEvent.Unsubscribe(oldValue, sender._affectsRenderWeakSubscriber);
+                            if (sender._affectsRenderWeakSubscriber != null)
+                            {
+                                InvalidatedWeakEvent.Unsubscribe(oldValue, sender._affectsRenderWeakSubscriber);
+                            }
                         }
-                    }
 
-                    if (e.NewValue is IAffectsRender newValue)
-                    {
-                        if (sender._affectsRenderWeakSubscriber == null)
+                        if (e.NewValue is IAffectsRender newValue)
                         {
-                            sender._affectsRenderWeakSubscriber = new TargetWeakEventSubscriber<Visual, EventArgs>(
-                                sender, static (target, _, _, _) =>
-                                {
-                                    target.InvalidateVisual();
-                                });
+                            if (sender._affectsRenderWeakSubscriber == null)
+                            {
+                                sender._affectsRenderWeakSubscriber = new TargetWeakEventSubscriber<Visual, EventArgs>(
+                                    sender, static (target, _, _, _) =>
+                                    {
+                                        target.InvalidateVisual();
+                                    });
+                            }
+                            InvalidatedWeakEvent.Subscribe(newValue, sender._affectsRenderWeakSubscriber);
                         }
-                        InvalidatedWeakEvent.Subscribe(newValue, sender._affectsRenderWeakSubscriber);
-                    }
 
-                    sender.InvalidateVisual();
-                }
-            }
+                        sender.InvalidateVisual();
+                    }
+                });
 
             foreach (var property in properties)
             {
                 if (property.CanValueAffectRender())
                 {
-                    property.Changed.Subscribe(e => InvalidateAndSubscribe(e));
+                    property.Changed.Subscribe(invalidateAndSubscribeObserver);
                 }
                 else
                 {
-                    property.Changed.Subscribe(e => Invalidate(e));
+                    property.Changed.Subscribe(invalidateObserver);
                 }
             }
         }
@@ -616,23 +620,22 @@ namespace Avalonia
         /// Called when a visual's <see cref="RenderTransform"/> changes.
         /// </summary>
         /// <param name="e">The event args.</param>
-        private static void RenderTransformChanged(AvaloniaPropertyChangedEventArgs e)
+        private static void RenderTransformChanged(AvaloniaPropertyChangedEventArgs<ITransform?> e)
         {
             var sender = e.Sender as Visual;
 
             if (sender?.VisualRoot != null)
             {
-                var oldValue = e.OldValue as Transform;
-                var newValue = e.NewValue as Transform;
+                var (oldValue, newValue) = e.GetOldAndNewValue<ITransform?>();
 
-                if (oldValue != null)
+                if (oldValue is Transform oldTransform)
                 {
-                    oldValue.Changed -= sender.RenderTransformChanged;
+                    oldTransform.Changed -= sender.RenderTransformChanged;
                 }
 
-                if (newValue != null)
+                if (newValue is Transform newTransform)
                 {
-                    newValue.Changed += sender.RenderTransformChanged;
+                    newTransform.Changed += sender.RenderTransformChanged;
                 }
                 
                 sender.InvalidateVisual();
diff --git a/src/Avalonia.Controls.ColorPicker/Avalonia.Controls.ColorPicker.csproj b/src/Avalonia.Controls.ColorPicker/Avalonia.Controls.ColorPicker.csproj
index f3f8e4c82c..c79468b48d 100644
--- a/src/Avalonia.Controls.ColorPicker/Avalonia.Controls.ColorPicker.csproj
+++ b/src/Avalonia.Controls.ColorPicker/Avalonia.Controls.ColorPicker.csproj
@@ -15,7 +15,6 @@
     <!-- Compatibility with old apps -->
     <EmbeddedResource Include="Themes\**\*.xaml" />
   </ItemGroup>
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\EmbedXaml.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
diff --git a/src/Avalonia.Controls.ColorPicker/ColorSpectrum/ColorSpectrum.cs b/src/Avalonia.Controls.ColorPicker/ColorSpectrum/ColorSpectrum.cs
index 2df46889a9..6f4c0003a8 100644
--- a/src/Avalonia.Controls.ColorPicker/ColorSpectrum/ColorSpectrum.cs
+++ b/src/Avalonia.Controls.ColorPicker/ColorSpectrum/ColorSpectrum.cs
@@ -15,6 +15,7 @@ using Avalonia.Media;
 using Avalonia.Media.Imaging;
 using Avalonia.Threading;
 using Avalonia.Utilities;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Primitives
 {
diff --git a/src/Avalonia.Controls.DataGrid/Avalonia.Controls.DataGrid.csproj b/src/Avalonia.Controls.DataGrid/Avalonia.Controls.DataGrid.csproj
index 6369961f0f..c3135cefce 100644
--- a/src/Avalonia.Controls.DataGrid/Avalonia.Controls.DataGrid.csproj
+++ b/src/Avalonia.Controls.DataGrid/Avalonia.Controls.DataGrid.csproj
@@ -12,7 +12,6 @@
     <!-- Compatibility with old apps -->
     <EmbeddedResource Include="Themes\**\*.xaml" />
   </ItemGroup>
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\EmbedXaml.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
diff --git a/src/Avalonia.Controls.DataGrid/DataGrid.cs b/src/Avalonia.Controls.DataGrid/DataGrid.cs
index 5dcad83601..b7546a4625 100644
--- a/src/Avalonia.Controls.DataGrid/DataGrid.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGrid.cs
@@ -27,6 +27,7 @@ using Avalonia.Layout;
 using Avalonia.Controls.Metadata;
 using Avalonia.Input.GestureRecognizers;
 using Avalonia.Styling;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs
index ce74604f70..e859a6e725 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridBoundColumn.cs
@@ -4,12 +4,7 @@
 // All other rights reserved. 
 
 using Avalonia.Data;
-using Avalonia.Utilities;
 using System;
-using System.Reactive.Disposables;
-using System.Reactive.Subjects;
-using Avalonia.Reactive;
-using System.Diagnostics;
 using Avalonia.Controls.Utils;
 using Avalonia.Markup.Xaml.MarkupExtensions;
 
diff --git a/src/Avalonia.Controls.DataGrid/DataGridRow.cs b/src/Avalonia.Controls.DataGrid/DataGridRow.cs
index dfa6ea2e46..c4010487af 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridRow.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridRow.cs
@@ -15,6 +15,7 @@ using Avalonia.Utilities;
 using Avalonia.VisualTree;
 using System;
 using System.Diagnostics;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
@@ -1021,11 +1022,11 @@ namespace Avalonia.Controls
                         {
                             layoutableContent.LayoutUpdated += DetailsContent_LayoutUpdated;
 
-                            _detailsContentSizeSubscription =
-                                System.Reactive.Disposables.StableCompositeDisposable.Create(
-                                    System.Reactive.Disposables.Disposable.Create(() => layoutableContent.LayoutUpdated -= DetailsContent_LayoutUpdated),
-                                    _detailsContent.GetObservable(MarginProperty)
-                                                   .Subscribe(DetailsContent_MarginChanged));
+                            _detailsContentSizeSubscription = new CompositeDisposable(2)
+                            {
+                                Disposable.Create(() => layoutableContent.LayoutUpdated -= DetailsContent_LayoutUpdated),
+                                _detailsContent.GetObservable(MarginProperty).Subscribe(DetailsContent_MarginChanged)
+                            };
 
 
                         }
diff --git a/src/Avalonia.Controls.DataGrid/DataGridRowGroupHeader.cs b/src/Avalonia.Controls.DataGrid/DataGridRowGroupHeader.cs
index c746b19cc7..10efded58a 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridRowGroupHeader.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridRowGroupHeader.cs
@@ -10,7 +10,7 @@ using Avalonia.Input;
 using Avalonia.Media;
 using System;
 using System.Diagnostics;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs b/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
index 1d1a595ccf..d6c46bb1e0 100644
--- a/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
+++ b/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
@@ -2,7 +2,7 @@
 using Avalonia.Reactive;
 using System;
 using System.Collections.Generic;
-using System.Reactive.Subjects;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Utils
 {
@@ -16,16 +16,16 @@ namespace Avalonia.Controls.Utils
 
     internal class CellEditBinding : ICellEditBinding
     {
-        private readonly Subject<bool> _changedSubject = new Subject<bool>();
+        private readonly LightweightSubject<bool> _changedSubject = new();
         private readonly List<Exception> _validationErrors = new List<Exception>();
         private readonly SubjectWrapper _inner;
 
         public bool IsValid => _validationErrors.Count <= 0;
         public IEnumerable<Exception> ValidationErrors => _validationErrors;
         public IObservable<bool> ValidationChanged => _changedSubject;
-        public ISubject<object> InternalSubject => _inner;
+        public IAvaloniaSubject<object> InternalSubject => _inner;
 
-        public CellEditBinding(ISubject<object> bindingSourceSubject)
+        public CellEditBinding(IAvaloniaSubject<object> bindingSourceSubject)
         {
             _inner = new SubjectWrapper(bindingSourceSubject, this);
         }
@@ -48,16 +48,16 @@ namespace Avalonia.Controls.Utils
             return IsValid;
         }
 
-        class SubjectWrapper : LightweightObservableBase<object>, ISubject<object>, IDisposable
+        class SubjectWrapper : LightweightObservableBase<object>, IAvaloniaSubject<object>, IDisposable
         {
-            private readonly ISubject<object> _sourceSubject;
+            private readonly IAvaloniaSubject<object> _sourceSubject;
             private readonly CellEditBinding _editBinding;
             private IDisposable _subscription;
             private object _controlValue;
             private bool _isControlValueSet = false;
             private bool _settingSourceValue = false;
 
-            public SubjectWrapper(ISubject<object> bindingSourceSubject, CellEditBinding editBinding)
+            public SubjectWrapper(IAvaloniaSubject<object> bindingSourceSubject, CellEditBinding editBinding)
             {
                 _sourceSubject = bindingSourceSubject;
                 _editBinding = editBinding;
diff --git a/src/Avalonia.Controls/Application.cs b/src/Avalonia.Controls/Application.cs
index dc9a0207ad..5b652cce19 100644
--- a/src/Avalonia.Controls/Application.cs
+++ b/src/Avalonia.Controls/Application.cs
@@ -1,7 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Concurrency;
-using System.Threading;
 using Avalonia.Animation;
 using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
@@ -231,7 +229,6 @@ namespace Avalonia
                 .Bind<IFocusManager>().ToConstant(FocusManager)
                 .Bind<IInputManager>().ToConstant(InputManager)
                 .Bind<IKeyboardNavigationHandler>().ToTransient<KeyboardNavigationHandler>()
-                .Bind<IScheduler>().ToConstant(AvaloniaScheduler.Instance)
                 .Bind<IDragDropDevice>().ToConstant(DragDropDevice.Instance);
             
             // TODO: Fix this, for now we keep this behavior since someone might be relying on it in 0.9.x
diff --git a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
index e0d986f2b4..c84e96ed6d 100644
--- a/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
+++ b/src/Avalonia.Controls/AutoCompleteBox/AutoCompleteBox.cs
@@ -10,7 +10,7 @@ using System.Collections.ObjectModel;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading;
 using System.Threading.Tasks;
 using Avalonia.Collections;
diff --git a/src/Avalonia.Controls/Avalonia.Controls.csproj b/src/Avalonia.Controls/Avalonia.Controls.csproj
index 2710ac5cc2..20ecb15079 100644
--- a/src/Avalonia.Controls/Avalonia.Controls.csproj
+++ b/src/Avalonia.Controls/Avalonia.Controls.csproj
@@ -6,7 +6,6 @@
     <ProjectReference Include="..\Avalonia.Base\Avalonia.Base.csproj" />
     <ProjectReference Include="..\Avalonia.Remote.Protocol\Avalonia.Remote.Protocol.csproj" />
   </ItemGroup>
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\JetBrains.Annotations.props" />
   <Import Project="..\..\build\ApiDiff.props" />
   <Import Project="..\..\build\NullableEnable.props" />
diff --git a/src/Avalonia.Controls/Button.cs b/src/Avalonia.Controls/Button.cs
index 8e5d4e1e06..1ec6f8dabc 100644
--- a/src/Avalonia.Controls/Button.cs
+++ b/src/Avalonia.Controls/Button.cs
@@ -5,6 +5,7 @@ using System.Windows.Input;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
+using Avalonia.Controls.Templates;
 using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Interactivity;
diff --git a/src/Avalonia.Controls/ButtonSpinner.cs b/src/Avalonia.Controls/ButtonSpinner.cs
index e455c6c6f3..4b2997f431 100644
--- a/src/Avalonia.Controls/ButtonSpinner.cs
+++ b/src/Avalonia.Controls/ButtonSpinner.cs
@@ -1,7 +1,6 @@
-using System;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
-using Avalonia.Data;
+using Avalonia.Reactive;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 
diff --git a/src/Avalonia.Controls/CalendarDatePicker/CalendarDatePicker.cs b/src/Avalonia.Controls/CalendarDatePicker/CalendarDatePicker.cs
index ec1273ca98..b17648f5bb 100644
--- a/src/Avalonia.Controls/CalendarDatePicker/CalendarDatePicker.cs
+++ b/src/Avalonia.Controls/CalendarDatePicker/CalendarDatePicker.cs
@@ -7,7 +7,7 @@ using System;
 using System.Collections.ObjectModel;
 using System.Diagnostics;
 using System.Globalization;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 using Avalonia.Data;
diff --git a/src/Avalonia.Controls/Canvas.cs b/src/Avalonia.Controls/Canvas.cs
index adee7d4d90..cd81c6e59b 100644
--- a/src/Avalonia.Controls/Canvas.cs
+++ b/src/Avalonia.Controls/Canvas.cs
@@ -1,7 +1,4 @@
-using System;
-using System.Reactive.Concurrency;
 using Avalonia.Input;
-using Avalonia.Layout;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/Chrome/CaptionButtons.cs b/src/Avalonia.Controls/Chrome/CaptionButtons.cs
index 6d7e542bb2..f5fcbed9fb 100644
--- a/src/Avalonia.Controls/Chrome/CaptionButtons.cs
+++ b/src/Avalonia.Controls/Chrome/CaptionButtons.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 
@@ -15,7 +15,7 @@ namespace Avalonia.Controls.Chrome
     [PseudoClasses(":minimized", ":normal", ":maximized", ":fullscreen")]
     public class CaptionButtons : TemplatedControl
     {
-        private CompositeDisposable? _disposables;
+        private IDisposable? _disposables;
 
         /// <summary>
         /// Currently attached window.
@@ -28,17 +28,14 @@ namespace Avalonia.Controls.Chrome
             {
                 HostWindow = hostWindow;
 
-                _disposables = new CompositeDisposable
-                {
-                    HostWindow.GetObservable(Window.WindowStateProperty)
+                _disposables = HostWindow.GetObservable(Window.WindowStateProperty)
                     .Subscribe(x =>
                     {
                         PseudoClasses.Set(":minimized", x == WindowState.Minimized);
                         PseudoClasses.Set(":normal", x == WindowState.Normal);
                         PseudoClasses.Set(":maximized", x == WindowState.Maximized);
                         PseudoClasses.Set(":fullscreen", x == WindowState.FullScreen);
-                    })
-                };
+                    });
             }
         }
 
diff --git a/src/Avalonia.Controls/Chrome/TitleBar.cs b/src/Avalonia.Controls/Chrome/TitleBar.cs
index 1bf13111a9..47b0bb6e2d 100644
--- a/src/Avalonia.Controls/Chrome/TitleBar.cs
+++ b/src/Avalonia.Controls/Chrome/TitleBar.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
 
@@ -61,7 +61,7 @@ namespace Avalonia.Controls.Chrome
 
             if (VisualRoot is Window window)
             {
-                _disposables = new CompositeDisposable
+                _disposables = new CompositeDisposable(6)
                 {
                     window.GetObservable(Window.WindowDecorationMarginProperty)
                         .Subscribe(x => UpdateSize(window)),
diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index a0085c92ca..839a3e3ba0 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Linq;
 using Avalonia.Automation.Peers;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Presenters;
diff --git a/src/Avalonia.Controls/ComboBoxItem.cs b/src/Avalonia.Controls/ComboBoxItem.cs
index 83057d139f..7db713d692 100644
--- a/src/Avalonia.Controls/ComboBoxItem.cs
+++ b/src/Avalonia.Controls/ComboBoxItem.cs
@@ -1,5 +1,4 @@
-using System;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Automation;
 using Avalonia.Automation.Peers;
 
@@ -12,8 +11,14 @@ namespace Avalonia.Controls
     {
         public ComboBoxItem()
         {
-            this.GetObservable(ComboBoxItem.IsFocusedProperty).Where(focused => focused)
-                .Subscribe(_ => (Parent as ComboBox)?.ItemFocused(this));
+            this.GetObservable(ComboBoxItem.IsFocusedProperty)
+                .Subscribe(focused =>
+                {
+                    if (focused)
+                    {
+                        (Parent as ComboBox)?.ItemFocused(this);
+                    }
+                });
         }
 
         static ComboBoxItem()
diff --git a/src/Avalonia.Controls/ContextMenu.cs b/src/Avalonia.Controls/ContextMenu.cs
index 020a6de539..b7ff75339d 100644
--- a/src/Avalonia.Controls/ContextMenu.cs
+++ b/src/Avalonia.Controls/ContextMenu.cs
@@ -15,6 +15,7 @@ using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Styling;
 using Avalonia.Automation;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/ControlExtensions.cs b/src/Avalonia.Controls/ControlExtensions.cs
index bceeb58adb..889a4cc79f 100644
--- a/src/Avalonia.Controls/ControlExtensions.cs
+++ b/src/Avalonia.Controls/ControlExtensions.cs
@@ -1,8 +1,5 @@
 using System;
-using System.Linq;
-using Avalonia.Data;
-using Avalonia.LogicalTree;
-using Avalonia.Styling;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/DataValidationErrors.cs b/src/Avalonia.Controls/DataValidationErrors.cs
index 00a06101c5..b082909807 100644
--- a/src/Avalonia.Controls/DataValidationErrors.cs
+++ b/src/Avalonia.Controls/DataValidationErrors.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Templates;
 using Avalonia.Data;
diff --git a/src/Avalonia.Controls/DefinitionBase.cs b/src/Avalonia.Controls/DefinitionBase.cs
index 64a02ccb46..f93f613583 100644
--- a/src/Avalonia.Controls/DefinitionBase.cs
+++ b/src/Avalonia.Controls/DefinitionBase.cs
@@ -7,6 +7,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
+using Avalonia.Reactive;
 using Avalonia.Utilities;
 
 namespace Avalonia.Controls
diff --git a/src/Avalonia.Controls/ExperimentalAcrylicBorder.cs b/src/Avalonia.Controls/ExperimentalAcrylicBorder.cs
index 30bdb4c60e..e4487d29fa 100644
--- a/src/Avalonia.Controls/ExperimentalAcrylicBorder.cs
+++ b/src/Avalonia.Controls/ExperimentalAcrylicBorder.cs
@@ -3,6 +3,7 @@ using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Platform;
 using System;
+using Avalonia.Reactive;
 using Avalonia.Media.Immutable;
 
 namespace Avalonia.Controls
diff --git a/src/Avalonia.Controls/Flyouts/FlyoutBase.cs b/src/Avalonia.Controls/Flyouts/FlyoutBase.cs
index 8455495830..9d4abec549 100644
--- a/src/Avalonia.Controls/Flyouts/FlyoutBase.cs
+++ b/src/Avalonia.Controls/Flyouts/FlyoutBase.cs
@@ -7,6 +7,7 @@ using Avalonia.Input.Platform;
 using Avalonia.Input.Raw;
 using Avalonia.Layout;
 using Avalonia.Logging;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Primitives
 {
diff --git a/src/Avalonia.Controls/HotkeyManager.cs b/src/Avalonia.Controls/HotkeyManager.cs
index dc3c621db4..de753f0bd0 100644
--- a/src/Avalonia.Controls/HotkeyManager.cs
+++ b/src/Avalonia.Controls/HotkeyManager.cs
@@ -2,6 +2,7 @@ using System;
 using System.Windows.Input;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/LayoutTransformControl.cs b/src/Avalonia.Controls/LayoutTransformControl.cs
index 766a712c88..ce254684b7 100644
--- a/src/Avalonia.Controls/LayoutTransformControl.cs
+++ b/src/Avalonia.Controls/LayoutTransformControl.cs
@@ -4,7 +4,7 @@
 
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Media;
 
 namespace Avalonia.Controls
@@ -424,9 +424,9 @@ namespace Avalonia.Controls
 
             if (newTransform != null)
             {
-                _transformChangedEvent = Observable.FromEventPattern<EventHandler, EventArgs>(
+                _transformChangedEvent = Observable.FromEventPattern(
                                         v => newTransform.Changed += v, v => newTransform.Changed -= v)
-                                        .Subscribe(onNext: v => ApplyLayoutTransform());
+                                        .Subscribe(_ => ApplyLayoutTransform());
             }
 
             ApplyLayoutTransform();
diff --git a/src/Avalonia.Controls/MenuItem.cs b/src/Avalonia.Controls/MenuItem.cs
index 3e00cea430..40941d00be 100644
--- a/src/Avalonia.Controls/MenuItem.cs
+++ b/src/Avalonia.Controls/MenuItem.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Windows.Input;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls.Generators;
@@ -159,12 +159,13 @@ namespace Avalonia.Controls
             // menu layout.
 
             var parentSharedSizeScope = this.GetObservable(VisualParentProperty)
-                .SelectMany(x =>
+                .Select(x =>
                 {
                     var parent = x as Control;
                     return parent?.GetObservable(DefinitionBase.PrivateSharedSizeScopeProperty) ??
                            Observable.Return<DefinitionBase.SharedSizeScope?>(null);
-                });
+                })
+                .Switch();
 
             this.Bind(DefinitionBase.PrivateSharedSizeScopeProperty, parentSharedSizeScope);
         }
diff --git a/src/Avalonia.Controls/Mixins/DisposableMixin.cs b/src/Avalonia.Controls/Mixins/DisposableMixin.cs
deleted file mode 100644
index 9b30b4ba4c..0000000000
--- a/src/Avalonia.Controls/Mixins/DisposableMixin.cs
+++ /dev/null
@@ -1,38 +0,0 @@
-using System;
-using System.Reactive.Disposables;
-
-namespace Avalonia.Controls.Mixins
-{
-    /// <summary>
-    /// Extension methods associated with the IDisposable interface.
-    /// </summary>
-    public static class DisposableMixin
-    {
-        /// <summary>
-        /// Ensures the provided disposable is disposed with the specified <see cref="CompositeDisposable"/>.
-        /// </summary>
-        /// <typeparam name="T">
-        /// The type of the disposable.
-        /// </typeparam>
-        /// <param name="item">
-        /// The disposable we are going to want to be disposed by the CompositeDisposable.
-        /// </param>
-        /// <param name="compositeDisposable">
-        /// The <see cref="CompositeDisposable"/> to which <paramref name="item"/> will be added.
-        /// </param>
-        /// <returns>
-        /// The disposable.
-        /// </returns>
-        public static T DisposeWith<T>(this T item, CompositeDisposable compositeDisposable)
-            where T : IDisposable
-        {
-            if (compositeDisposable is null)
-            {
-                throw new ArgumentNullException(nameof(compositeDisposable));
-            }
-
-            compositeDisposable.Add(item);
-            return item;
-        }
-    }
-}
diff --git a/src/Avalonia.Controls/Mixins/SelectableMixin.cs b/src/Avalonia.Controls/Mixins/SelectableMixin.cs
index a04a741e3e..2a8fe7b976 100644
--- a/src/Avalonia.Controls/Mixins/SelectableMixin.cs
+++ b/src/Avalonia.Controls/Mixins/SelectableMixin.cs
@@ -1,7 +1,7 @@
 using System;
 using Avalonia.Interactivity;
 using Avalonia.Controls.Primitives;
-using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Mixins
 {
diff --git a/src/Avalonia.Controls/NativeMenu.Export.cs b/src/Avalonia.Controls/NativeMenu.Export.cs
index fe650ab41e..c556ce7b02 100644
--- a/src/Avalonia.Controls/NativeMenu.Export.cs
+++ b/src/Avalonia.Controls/NativeMenu.Export.cs
@@ -1,7 +1,6 @@
 using System;
-using System.Collections.Generic;
 using Avalonia.Controls.Platform;
-using Avalonia.Data;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/NativeMenuBar.cs b/src/Avalonia.Controls/NativeMenuBar.cs
index ac7a45a547..3953de8165 100644
--- a/src/Avalonia.Controls/NativeMenuBar.cs
+++ b/src/Avalonia.Controls/NativeMenuBar.cs
@@ -2,6 +2,7 @@ using System;
 using System.Diagnostics.CodeAnalysis;
 using Avalonia.Controls.Primitives;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/NativeMenuItem.cs b/src/Avalonia.Controls/NativeMenuItem.cs
index d22fdb2f84..526eff0f12 100644
--- a/src/Avalonia.Controls/NativeMenuItem.cs
+++ b/src/Avalonia.Controls/NativeMenuItem.cs
@@ -4,6 +4,7 @@ using Avalonia.Input;
 using Avalonia.Media.Imaging;
 using Avalonia.Metadata;
 using Avalonia.Utilities;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/Notifications/NotificationCard.cs b/src/Avalonia.Controls/Notifications/NotificationCard.cs
index a103adf185..663bd3358a 100644
--- a/src/Avalonia.Controls/Notifications/NotificationCard.cs
+++ b/src/Avalonia.Controls/Notifications/NotificationCard.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Interactivity;
 using Avalonia.LogicalTree;
@@ -37,30 +37,29 @@ namespace Avalonia.Controls.Notifications
                     RaiseEvent(new RoutedEventArgs(NotificationClosedEvent));
                 });
 
-            // Disabling nullable checking because of https://github.com/dotnet/reactive/issues/1525
-#pragma warning disable CS8620
             this.GetObservable(ContentProperty)
-                .OfType<Notification>()
-#pragma warning restore CS8620
                 .Subscribe(x =>
                 {
-                    switch (x.Type)
+                    if (x is Notification notification)
                     {
-                        case NotificationType.Error:
-                            PseudoClasses.Add(":error");
-                            break;
-
-                        case NotificationType.Information:
-                            PseudoClasses.Add(":information");
-                            break;
-
-                        case NotificationType.Success:
-                            PseudoClasses.Add(":success");
-                            break;
-
-                        case NotificationType.Warning:
-                            PseudoClasses.Add(":warning");
-                            break;
+                        switch (notification.Type)
+                        {
+                            case NotificationType.Error:
+                                PseudoClasses.Add(":error");
+                                break;
+
+                            case NotificationType.Information:
+                                PseudoClasses.Add(":information");
+                                break;
+
+                            case NotificationType.Success:
+                                PseudoClasses.Add(":success");
+                                break;
+
+                            case NotificationType.Warning:
+                                PseudoClasses.Add(":warning");
+                                break;
+                        }
                     }
                 });
         }
diff --git a/src/Avalonia.Controls/Notifications/WindowNotificationManager.cs b/src/Avalonia.Controls/Notifications/WindowNotificationManager.cs
index 46c772f3b1..3ccddf4155 100644
--- a/src/Avalonia.Controls/Notifications/WindowNotificationManager.cs
+++ b/src/Avalonia.Controls/Notifications/WindowNotificationManager.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
diff --git a/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs b/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
index 8ed6abd52b..ac4f699313 100644
--- a/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
+++ b/src/Avalonia.Controls/NumericUpDown/NumericUpDown.cs
@@ -9,6 +9,7 @@ using Avalonia.Data.Converters;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Layout;
+using Avalonia.Reactive;
 using Avalonia.Threading;
 using Avalonia.Utilities;
 
diff --git a/src/Avalonia.Controls/Panel.cs b/src/Avalonia.Controls/Panel.cs
index 7134e1b9e7..a643edc420 100644
--- a/src/Avalonia.Controls/Panel.cs
+++ b/src/Avalonia.Controls/Panel.cs
@@ -5,6 +5,7 @@ using System.Linq;
 using Avalonia.LogicalTree;
 using Avalonia.Media;
 using Avalonia.Metadata;
+using Avalonia.Reactive;
 using Avalonia.Styling;
 
 namespace Avalonia.Controls
diff --git a/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs b/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
index 6d525da150..e09da02f17 100644
--- a/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
+++ b/src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs
@@ -6,9 +6,9 @@ using Avalonia.Interactivity;
 using Avalonia.LogicalTree;
 using Avalonia.Metadata;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using Avalonia.Rendering;
 using Avalonia.Threading;
-using Avalonia.VisualTree;
 
 namespace Avalonia.Controls.Platform
 {
diff --git a/src/Avalonia.Controls/Platform/InProcessDragSource.cs b/src/Avalonia.Controls/Platform/InProcessDragSource.cs
index 5b2356a7ce..1a262aa493 100644
--- a/src/Avalonia.Controls/Platform/InProcessDragSource.cs
+++ b/src/Avalonia.Controls/Platform/InProcessDragSource.cs
@@ -1,7 +1,5 @@
-using System;
-using System.Linq;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
+using System.Linq;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Input;
@@ -17,7 +15,7 @@ namespace Avalonia.Platform
         private const RawInputModifiers MOUSE_INPUTMODIFIERS = RawInputModifiers.LeftMouseButton|RawInputModifiers.MiddleMouseButton|RawInputModifiers.RightMouseButton;
         private readonly IDragDropDevice _dragDrop;
         private readonly IInputManager _inputManager;
-        private readonly Subject<DragDropEffects> _result = new Subject<DragDropEffects>();
+        private readonly LightweightSubject<DragDropEffects> _result = new();
 
         private DragDropEffects _allowedEffects;
         private IDataObject? _draggedData;
@@ -44,11 +42,25 @@ namespace Avalonia.Platform
                 _lastPosition = default(Point);
                 _allowedEffects = allowedEffects;
 
-                using (_inputManager.PreProcess.OfType<RawPointerEventArgs>().Subscribe(ProcessMouseEvents))
+                var inputObserver = new AnonymousObserver<RawInputEventArgs>(arg =>
                 {
-                    using (_inputManager.PreProcess.OfType<RawKeyEventArgs>().Subscribe(ProcessKeyEvents))
+                    switch (arg)
                     {
-                        var effect = await _result.FirstAsync();
+                        case RawPointerEventArgs pointerEventArgs:
+                            ProcessMouseEvents(pointerEventArgs);
+                            break;
+                        case RawKeyEventArgs keyEventArgs:
+                            ProcessKeyEvents(keyEventArgs);
+                            break;
+                    }
+                }); 
+                
+                using (_inputManager.PreProcess.Subscribe(inputObserver))
+                {
+                    var tcs = new TaskCompletionSource<DragDropEffects>();
+                    using (_result.Subscribe(new AnonymousObserver<DragDropEffects>(tcs)))
+                    {
+                        var effect = await tcs.Task;
                         return effect;
                     }
                 }
diff --git a/src/Avalonia.Controls/Platform/PlatformManager.cs b/src/Avalonia.Controls/Platform/PlatformManager.cs
index de7708e869..d678911e1f 100644
--- a/src/Avalonia.Controls/Platform/PlatformManager.cs
+++ b/src/Avalonia.Controls/Platform/PlatformManager.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Metadata;
 using Avalonia.Platform;
 
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
index 7b435e287d..0e283c3c4b 100644
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
@@ -1,6 +1,6 @@
 using System.Collections.Specialized;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Animation;
 using Avalonia.Controls.Primitives;
diff --git a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
index 1f0f2a2f67..b9f856cf39 100644
--- a/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
+++ b/src/Avalonia.Controls/Presenters/ItemVirtualizer.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections;
 using System.Collections.Specialized;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Utils;
 using Avalonia.Input;
diff --git a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
index 328facba0b..254515755d 100644
--- a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
@@ -1,8 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Utilities;
diff --git a/src/Avalonia.Controls/Primitives/AccessText.cs b/src/Avalonia.Controls/Primitives/AccessText.cs
index 7e5b34acd9..49e76d0728 100644
--- a/src/Avalonia.Controls/Primitives/AccessText.cs
+++ b/src/Avalonia.Controls/Primitives/AccessText.cs
@@ -1,7 +1,6 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
 using Avalonia.Automation.Peers;
 using Avalonia.Input;
+using Avalonia.Reactive;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 
diff --git a/src/Avalonia.Controls/Primitives/AdornerLayer.cs b/src/Avalonia.Controls/Primitives/AdornerLayer.cs
index 89abe1cdaa..c9585d50ae 100644
--- a/src/Avalonia.Controls/Primitives/AdornerLayer.cs
+++ b/src/Avalonia.Controls/Primitives/AdornerLayer.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Specialized;
 using Avalonia.Media;
+using Avalonia.Reactive;
 using Avalonia.Rendering;
 using Avalonia.VisualTree;
 
diff --git a/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs b/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
index cd26ea4f6e..e0f72cae54 100644
--- a/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
+++ b/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Primitives.PopupPositioning;
 using Avalonia.Interactivity;
 using Avalonia.Media;
diff --git a/src/Avalonia.Controls/Primitives/Popup.cs b/src/Avalonia.Controls/Primitives/Popup.cs
index 3c329a9a3e..bf79198939 100644
--- a/src/Avalonia.Controls/Primitives/Popup.cs
+++ b/src/Avalonia.Controls/Primitives/Popup.cs
@@ -1,6 +1,6 @@
 using System;
 using System.ComponentModel;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls.Mixins;
 using Avalonia.Controls.Diagnostics;
diff --git a/src/Avalonia.Controls/ProgressBar.cs b/src/Avalonia.Controls/ProgressBar.cs
index 165bec3a95..7e0d695264 100644
--- a/src/Avalonia.Controls/ProgressBar.cs
+++ b/src/Avalonia.Controls/ProgressBar.cs
@@ -4,6 +4,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Data;
 using Avalonia.Layout;
 using Avalonia.Media;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/PullToRefresh/RefreshContainer.cs b/src/Avalonia.Controls/PullToRefresh/RefreshContainer.cs
index d0b8178add..2c29b19d48 100644
--- a/src/Avalonia.Controls/PullToRefresh/RefreshContainer.cs
+++ b/src/Avalonia.Controls/PullToRefresh/RefreshContainer.cs
@@ -3,6 +3,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Controls.PullToRefresh;
 using Avalonia.Input;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs b/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
index f2f735aaa9..8723304f8f 100644
--- a/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
+++ b/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
@@ -1,12 +1,12 @@
 using System;
 using System.Numerics;
-using System.Reactive.Linq;
 using Avalonia.Animation.Easings;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.PullToRefresh;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.Media;
+using Avalonia.Reactive;
 using Avalonia.Rendering.Composition;
 using Avalonia.Rendering.Composition.Animations;
 
diff --git a/src/Avalonia.Controls/RadioButton.cs b/src/Avalonia.Controls/RadioButton.cs
index 9dbc5f040e..68da24d79f 100644
--- a/src/Avalonia.Controls/RadioButton.cs
+++ b/src/Avalonia.Controls/RadioButton.cs
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using Avalonia.Controls.Primitives;
+using Avalonia.Reactive;
 using Avalonia.Rendering;
 using Avalonia.VisualTree;
 
diff --git a/src/Avalonia.Controls/Repeater/ViewportManager.cs b/src/Avalonia.Controls/Repeater/ViewportManager.cs
index 10e3dd57a0..d7f24ec537 100644
--- a/src/Avalonia.Controls/Repeater/ViewportManager.cs
+++ b/src/Avalonia.Controls/Repeater/ViewportManager.cs
@@ -4,16 +4,8 @@
 // Licensed to The Avalonia Project under MIT License, courtesy of The .NET Foundation.
 
 using System;
-using System.Collections.Generic;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using System.Threading.Tasks;
-using Avalonia.Controls.Presenters;
-using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Logging;
-using Avalonia.Media;
-using Avalonia.Reactive;
 using Avalonia.Threading;
 using Avalonia.VisualTree;
 
diff --git a/src/Avalonia.Controls/ScrollViewer.cs b/src/Avalonia.Controls/ScrollViewer.cs
index 12fb9ba5c5..503187e2d3 100644
--- a/src/Avalonia.Controls/ScrollViewer.cs
+++ b/src/Avalonia.Controls/ScrollViewer.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
diff --git a/src/Avalonia.Controls/Shapes/Shape.cs b/src/Avalonia.Controls/Shapes/Shape.cs
index e2a13512a5..c8bf95b3f7 100644
--- a/src/Avalonia.Controls/Shapes/Shape.cs
+++ b/src/Avalonia.Controls/Shapes/Shape.cs
@@ -2,6 +2,7 @@ using System;
 using Avalonia.Collections;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Shapes
 {
diff --git a/src/Avalonia.Controls/Spinner.cs b/src/Avalonia.Controls/Spinner.cs
index cfcf0ee376..bf6ed060bd 100644
--- a/src/Avalonia.Controls/Spinner.cs
+++ b/src/Avalonia.Controls/Spinner.cs
@@ -1,5 +1,6 @@
 using System;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/SplitButton/SplitButton.cs b/src/Avalonia.Controls/SplitButton/SplitButton.cs
index f39064435d..1d2bab8d27 100644
--- a/src/Avalonia.Controls/SplitButton/SplitButton.cs
+++ b/src/Avalonia.Controls/SplitButton/SplitButton.cs
@@ -5,6 +5,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Interactivity;
 using Avalonia.LogicalTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/SplitView.cs b/src/Avalonia.Controls/SplitView.cs
index fcadafaab5..35b135e152 100644
--- a/src/Avalonia.Controls/SplitView.cs
+++ b/src/Avalonia.Controls/SplitView.cs
@@ -6,6 +6,7 @@ using Avalonia.Media;
 using Avalonia.Metadata;
 using Avalonia.VisualTree;
 using System;
+using Avalonia.Reactive;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
 using Avalonia.LogicalTree;
diff --git a/src/Avalonia.Controls/Templates/FuncDataTemplate.cs b/src/Avalonia.Controls/Templates/FuncDataTemplate.cs
index cfd4234a27..6fedf2b1cd 100644
--- a/src/Avalonia.Controls/Templates/FuncDataTemplate.cs
+++ b/src/Avalonia.Controls/Templates/FuncDataTemplate.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Primitives;
 
 namespace Avalonia.Controls.Templates
diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index 1bdec878d9..6938027510 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -2,7 +2,7 @@ using Avalonia.Input.Platform;
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Utils;
diff --git a/src/Avalonia.Controls/ToolTip.cs b/src/Avalonia.Controls/ToolTip.cs
index bb18bf4c64..d3339e3edf 100644
--- a/src/Avalonia.Controls/ToolTip.cs
+++ b/src/Avalonia.Controls/ToolTip.cs
@@ -2,6 +2,7 @@ using System;
 using Avalonia.Controls.Diagnostics;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Primitives;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 2cd55dc3ab..1f5b8f80d2 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Notifications;
 using Avalonia.Controls.Platform;
diff --git a/src/Avalonia.Controls/TrayIcon.cs b/src/Avalonia.Controls/TrayIcon.cs
index 41a1abd838..d1a7a1f727 100644
--- a/src/Avalonia.Controls/TrayIcon.cs
+++ b/src/Avalonia.Controls/TrayIcon.cs
@@ -6,7 +6,7 @@ using Avalonia.Collections;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Platform;
 using Avalonia.Platform;
-using Avalonia.Utilities;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index ffdd32f95c..f98bab7d40 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -5,7 +5,7 @@ using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Collections;
 using Avalonia.Controls.Generators;
 using Avalonia.Controls.Primitives;
diff --git a/src/Avalonia.Controls/Utils/AncestorFinder.cs b/src/Avalonia.Controls/Utils/AncestorFinder.cs
index d2e3feb55a..f8e06ba35d 100644
--- a/src/Avalonia.Controls/Utils/AncestorFinder.cs
+++ b/src/Avalonia.Controls/Utils/AncestorFinder.cs
@@ -1,8 +1,5 @@
 using System;
-using System.Reactive;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
+using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Utils
 {
@@ -13,7 +10,7 @@ namespace Avalonia.Controls.Utils
             private readonly StyledElement _control;
             private readonly Type _ancestorType;
             public IObservable<StyledElement?> Observable => _subject;
-            private readonly Subject<StyledElement?> _subject = new Subject<StyledElement?>();
+            private readonly LightweightSubject<StyledElement?> _subject = new();
 
             private FinderNode? _child;
             private IDisposable? _disposable;
@@ -31,24 +28,21 @@ namespace Avalonia.Controls.Utils
 
             private void OnValueChanged(StyledElement? next)
             {
-                if (next == null || _ancestorType.IsAssignableFrom(next.GetType()))
+                if (next == null || _ancestorType.IsInstanceOfType(next))
                     _subject.OnNext(next);
                 else
                 {
                     _child?.Dispose();
                     _child = new FinderNode(next, _ancestorType);
-                    _child.Observable.Subscribe(OnChildValueChanged);
+                    _child.Observable.Subscribe(_subject);
                     _child.Init();
                 }
             }
 
-            private void OnChildValueChanged(StyledElement? control) => _subject.OnNext(control);
-
-
             public void Dispose()
             {
                 _child?.Dispose();
-                _subject.Dispose();
+                _subject.OnCompleted();
                 _disposable?.Dispose();
             }
         }
@@ -61,7 +55,7 @@ namespace Avalonia.Controls.Utils
 
         public static IObservable<StyledElement?> Create(StyledElement control, Type ancestorType)
         {
-            return new AnonymousObservable<StyledElement?>(observer =>
+            return Observable.Create<StyledElement?>(observer =>
             {
                 var finder = new FinderNode(control, ancestorType);
                 var subscription = finder.Observable.Subscribe(observer);
diff --git a/src/Avalonia.Controls/Window.cs b/src/Avalonia.Controls/Window.cs
index 88f3b520ce..a20b4eee58 100644
--- a/src/Avalonia.Controls/Window.cs
+++ b/src/Avalonia.Controls/Window.cs
@@ -2,7 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls.Platform;
@@ -800,7 +800,7 @@ namespace Avalonia.Controls
 
                 Renderer?.Start();
 
-                Observable.FromEventPattern<EventHandler, EventArgs>(
+                Observable.FromEventPattern(
                         x => Closed += x,
                         x => Closed -= x)
                     .Take(1)
diff --git a/src/Avalonia.Controls/WindowBase.cs b/src/Avalonia.Controls/WindowBase.cs
index b71dc6df44..aad0482b50 100644
--- a/src/Avalonia.Controls/WindowBase.cs
+++ b/src/Avalonia.Controls/WindowBase.cs
@@ -1,14 +1,9 @@
 using System;
 using System.ComponentModel;
-using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using Avalonia.Automation.Peers;
 using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Platform;
-using JetBrains.Annotations;
 
 namespace Avalonia.Controls
 {
diff --git a/src/Avalonia.DesignerSupport/Avalonia.DesignerSupport.csproj b/src/Avalonia.DesignerSupport/Avalonia.DesignerSupport.csproj
index 867c94b126..c5255b22cd 100644
--- a/src/Avalonia.DesignerSupport/Avalonia.DesignerSupport.csproj
+++ b/src/Avalonia.DesignerSupport/Avalonia.DesignerSupport.csproj
@@ -19,6 +19,5 @@
     <ProjectReference Include="..\Avalonia.Base\Avalonia.Base.csproj" />
     <ProjectReference Include="..\Avalonia.Controls\Avalonia.Controls.csproj" />
   </ItemGroup>
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\ApiDiff.props" />
 </Project>
diff --git a/src/Avalonia.DesignerSupport/Remote/Stubs.cs b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
index 94679e8ade..3238b394fc 100644
--- a/src/Avalonia.DesignerSupport/Remote/Stubs.cs
+++ b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Automation.Peers;
 using Avalonia.Controls;
diff --git a/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs b/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
index 8eadcee6f9..9b4e13959b 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
@@ -1,12 +1,12 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Views;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
 using Avalonia.Interactivity;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics
 {
@@ -90,7 +90,7 @@ namespace Avalonia.Diagnostics
                 {
                     s_attachedToApplication = true;
 
-                    application.InputManager.PreProcess.OfType<RawKeyEventArgs>().Subscribe(e =>
+                    ObservableExtensions.Subscribe(application.InputManager.PreProcess.OfType<RawKeyEventArgs>(), e =>
                     {
                         if (options.Gesture.Matches(e))
                         {
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
index e71f0bcaec..7c6246701a 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
@@ -84,7 +84,7 @@ namespace Avalonia.Diagnostics.ViewModels
                         }
                         nodes.Add(new LogicalTreeNode(window, Owner));
                     }
-                    _subscriptions = new System.Reactive.Disposables.CompositeDisposable()
+                    _subscriptions = new CompositeDisposable(2)
                     {
                         Window.WindowOpenedEvent.AddClassHandler(typeof(Window), (s,e)=>
                             {
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
index a1cd01c78b..e44b852372 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
@@ -188,7 +188,7 @@ namespace Avalonia.Diagnostics.ViewModels
                         }
                         nodes.Add(new VisualTreeNode(window, Owner));
                     }
-                    _subscriptions = new System.Reactive.Disposables.CompositeDisposable()
+                    _subscriptions = new CompositeDisposable(2)
                     {
                         Window.WindowOpenedEvent.AddClassHandler(typeof(Window), (s,e)=>
                             {
diff --git a/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs b/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
index 7d0072c6ea..a2f8af0575 100644
--- a/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
+++ b/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
@@ -2,8 +2,7 @@ using System;
 using System.Collections.Specialized;
 using System.IO;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Runtime.InteropServices;
 using Avalonia.Collections;
 using Avalonia.Controls;
@@ -120,10 +119,8 @@ namespace Avalonia.Dialogs.Internal
                                       .GetService<IMountedVolumeInfoProvider>()
                                       .Listen(ManagedFileChooserSources.MountedVolumes);
 
-            var sub2 = Observable.FromEventPattern(ManagedFileChooserSources.MountedVolumes,
-                                            nameof(ManagedFileChooserSources.MountedVolumes.CollectionChanged))
-                                 .ObserveOn(AvaloniaScheduler.Instance)
-                                 .Subscribe(x => RefreshQuickLinks(quickSources));
+            var sub2 = ManagedFileChooserSources.MountedVolumes.GetWeakCollectionChangedObservable()
+                .Subscribe(x => Dispatcher.UIThread.Post(() => RefreshQuickLinks(quickSources)));
 
             _disposables.Add(sub1);
             _disposables.Add(sub2);
diff --git a/src/Avalonia.FreeDesktop/DBusIme/Fcitx/FcitxX11TextInputMethod.cs b/src/Avalonia.FreeDesktop/DBusIme/Fcitx/FcitxX11TextInputMethod.cs
index 791431dfa7..0f499c6066 100644
--- a/src/Avalonia.FreeDesktop/DBusIme/Fcitx/FcitxX11TextInputMethod.cs
+++ b/src/Avalonia.FreeDesktop/DBusIme/Fcitx/FcitxX11TextInputMethod.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Diagnostics;
-using System.Reactive.Concurrency;
 using System.Reflection;
 using System.Threading.Tasks;
 using Avalonia.Input;
diff --git a/src/Avalonia.FreeDesktop/DBusMenuExporter.cs b/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
index 657e324010..560d6fc252 100644
--- a/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
+++ b/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
@@ -2,7 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
 using System.IO;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
diff --git a/src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs b/src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs
index e37067d05c..b44762161b 100644
--- a/src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs
+++ b/src/Avalonia.FreeDesktop/DBusTrayIconImpl.cs
@@ -2,7 +2,7 @@
 
 using System;
 using System.Diagnostics;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Runtime.CompilerServices;
 using System.Threading.Tasks;
 using Avalonia.Controls.Platform;
diff --git a/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs b/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
index 34c1506a67..9f6b056d30 100644
--- a/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
+++ b/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
@@ -4,11 +4,12 @@ using System.Linq;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using Avalonia.Controls.Platform;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
+using Avalonia.Reactive;
 using System.Text.RegularExpressions;
 using System.Runtime.InteropServices;
 using System.Text;
+using Avalonia.Threading;
 
 namespace Avalonia.FreeDesktop
 {
@@ -17,21 +18,17 @@ namespace Avalonia.FreeDesktop
         private const string DevByLabelDir = "/dev/disk/by-label/";
         private const string ProcPartitionsDir = "/proc/partitions";
         private const string ProcMountsDir = "/proc/mounts";
-        private CompositeDisposable _disposables;
+        private IDisposable _disposable;
         private ObservableCollection<MountedVolumeInfo> _targetObs;
         private bool _beenDisposed = false;
 
         public LinuxMountedVolumeInfoListener(ref ObservableCollection<MountedVolumeInfo> target)
         {
-            _disposables = new CompositeDisposable();
             this._targetObs = target;
 
-            var pollTimer = Observable.Interval(TimeSpan.FromSeconds(1))
-                                      .Subscribe(Poll);
+            _disposable = DispatcherTimer.Run(Poll, TimeSpan.FromSeconds(1));
 
-            _disposables.Add(pollTimer);
-
-            Poll(0);
+            Poll();
         }
 
         private static string GetSymlinkTarget(string x) => Path.GetFullPath(Path.Combine(DevByLabelDir, NativeMethods.ReadLink(x)));
@@ -43,7 +40,7 @@ namespace Avalonia.FreeDesktop
 
         private static string UnescapeDeviceLabel(string input) => UnescapeString(input, @"\\x([0-9a-f]{2})", 16);
 
-        private void Poll(long _)
+        private bool Poll()
         {
             var fProcPartitions = File.ReadAllLines(ProcPartitionsDir)
                                       .Skip(1)
@@ -77,13 +74,14 @@ namespace Avalonia.FreeDesktop
             var mountVolInfos = q1.ToArray();
 
             if (_targetObs.SequenceEqual(mountVolInfos))
-                return;
+                return true;
             else
             {
                 _targetObs.Clear();
 
                 foreach (var i in mountVolInfos)
                     _targetObs.Add(i);
+                return true;
             }
         }
 
@@ -93,7 +91,7 @@ namespace Avalonia.FreeDesktop
             {
                 if (disposing)
                 {
-                    _disposables.Dispose();
+                    _disposable.Dispose();
                     _targetObs.Clear();
                 }
 
diff --git a/src/Avalonia.Headless/AvaloniaHeadlessPlatform.cs b/src/Avalonia.Headless/AvaloniaHeadlessPlatform.cs
index 8da10fa59b..e846309c24 100644
--- a/src/Avalonia.Headless/AvaloniaHeadlessPlatform.cs
+++ b/src/Avalonia.Headless/AvaloniaHeadlessPlatform.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Diagnostics;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
diff --git a/src/Avalonia.Headless/HeadlessPlatformThreadingInterface.cs b/src/Avalonia.Headless/HeadlessPlatformThreadingInterface.cs
index b233b46dd0..046e4645e3 100644
--- a/src/Avalonia.Headless/HeadlessPlatformThreadingInterface.cs
+++ b/src/Avalonia.Headless/HeadlessPlatformThreadingInterface.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Threading;
 using Avalonia.Platform;
 using Avalonia.Threading;
diff --git a/src/Avalonia.Native/IAvnMenu.cs b/src/Avalonia.Native/IAvnMenu.cs
index e6a5a371d0..515835a3bd 100644
--- a/src/Avalonia.Native/IAvnMenu.cs
+++ b/src/Avalonia.Native/IAvnMenu.cs
@@ -1,7 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Collections.Specialized;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls;
 
 namespace Avalonia.Native.Interop
diff --git a/src/Avalonia.Native/IAvnMenuItem.cs b/src/Avalonia.Native/IAvnMenuItem.cs
index de3be6142e..424d2c7310 100644
--- a/src/Avalonia.Native/IAvnMenuItem.cs
+++ b/src/Avalonia.Native/IAvnMenuItem.cs
@@ -1,6 +1,6 @@
 using System;
 using System.IO;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls;
 using Avalonia.Media.Imaging;
 using Avalonia.Platform.Interop;
diff --git a/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs b/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
index 92b2915e2e..59e14758ef 100644
--- a/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
+++ b/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
@@ -2,15 +2,16 @@ using System;
 using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
+using Avalonia.Reactive;
 using Avalonia.Controls.Platform;
+using Avalonia.Threading;
 
 namespace Avalonia.Native
 {
     internal class MacOSMountedVolumeInfoListener : IDisposable
     {
-        private readonly CompositeDisposable _disposables;
+        private readonly IDisposable _disposable;
         private bool _beenDisposed = false;
         private ObservableCollection<MountedVolumeInfo> mountedDrives;
 
@@ -18,17 +19,12 @@ namespace Avalonia.Native
         {
             this.mountedDrives = mountedDrives;
 
-            _disposables = new CompositeDisposable();
+            _disposable = DispatcherTimer.Run(Poll, TimeSpan.FromSeconds(1));
 
-            var pollTimer = Observable.Interval(TimeSpan.FromSeconds(1))
-                                      .Subscribe(Poll);
-
-            _disposables.Add(pollTimer);
-
-            Poll(0);
+            Poll();
         }
 
-        private void Poll(long _)
+        private bool Poll()
         {
             var mountVolInfos = Directory.GetDirectories("/Volumes/")
                                 .Where(p=> p != null)
@@ -41,13 +37,14 @@ namespace Avalonia.Native
                                 .ToArray();
                                 
             if (mountedDrives.SequenceEqual(mountVolInfos))
-                return;
+                return true;
             else
             {
                 mountedDrives.Clear();
 
                 foreach (var i in mountVolInfos)
                     mountedDrives.Add(i);
+                return true;
             }
         }
 
diff --git a/src/Avalonia.OpenGL/Egl/EglContext.cs b/src/Avalonia.OpenGL/Egl/EglContext.cs
index 4d75a776c3..0b4b7d26a1 100644
--- a/src/Avalonia.OpenGL/Egl/EglContext.cs
+++ b/src/Avalonia.OpenGL/Egl/EglContext.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Threading;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using static Avalonia.OpenGL.Egl.EglConsts;
 
 namespace Avalonia.OpenGL.Egl
diff --git a/src/Avalonia.OpenGL/Egl/EglDisplay.cs b/src/Avalonia.OpenGL/Egl/EglDisplay.cs
index eea2587587..c67d7674a8 100644
--- a/src/Avalonia.OpenGL/Egl/EglDisplay.cs
+++ b/src/Avalonia.OpenGL/Egl/EglDisplay.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Disposables;
 using System.Threading;
+using Avalonia.Reactive;
 using static Avalonia.OpenGL.Egl.EglConsts;
 
 namespace Avalonia.OpenGL.Egl
diff --git a/src/Avalonia.OpenGL/Egl/EglDisplayUtils.cs b/src/Avalonia.OpenGL/Egl/EglDisplayUtils.cs
index fbfaf1bd3d..5573eb39fa 100644
--- a/src/Avalonia.OpenGL/Egl/EglDisplayUtils.cs
+++ b/src/Avalonia.OpenGL/Egl/EglDisplayUtils.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Disposables;
 using System.Threading;
 using static Avalonia.OpenGL.Egl.EglConsts;
 namespace Avalonia.OpenGL.Egl;
@@ -132,4 +131,4 @@ class EglConfigInfo
         SampleCount = sampleCount;
         StencilSize = stencilSize;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Avalonia.ReactiveUI/Attributes.cs b/src/Avalonia.ReactiveUI/Attributes.cs
index 31c374392f..1b85cd2f47 100644
--- a/src/Avalonia.ReactiveUI/Attributes.cs
+++ b/src/Avalonia.ReactiveUI/Attributes.cs
@@ -1,5 +1,4 @@
 using System.Reflection;
-using System.Runtime.CompilerServices;
 using Avalonia.Metadata;
 
 [assembly: XmlnsDefinition("http://reactiveui.net", "Avalonia.ReactiveUI")]
\ No newline at end of file
diff --git a/src/Avalonia.ReactiveUI/AutoSuspendHelper.cs b/src/Avalonia.ReactiveUI/AutoSuspendHelper.cs
index bd21503a58..ae9a8787bc 100644
--- a/src/Avalonia.ReactiveUI/AutoSuspendHelper.cs
+++ b/src/Avalonia.ReactiveUI/AutoSuspendHelper.cs
@@ -2,10 +2,10 @@ using Avalonia;
 using Avalonia.VisualTree;
 using Avalonia.Controls;
 using System.Threading;
+using System.Reactive;
 using System.Reactive.Disposables;
 using System.Reactive.Subjects;
 using System.Reactive.Linq;
-using System.Reactive;
 using ReactiveUI;
 using System;
 using Avalonia.Controls.ApplicationLifetimes;
diff --git a/src/Avalonia.ReactiveUI/AvaloniaObjectReactiveExtensions.cs b/src/Avalonia.ReactiveUI/AvaloniaObjectReactiveExtensions.cs
new file mode 100644
index 0000000000..4cd329beb6
--- /dev/null
+++ b/src/Avalonia.ReactiveUI/AvaloniaObjectReactiveExtensions.cs
@@ -0,0 +1,110 @@
+using System.Reactive;
+using System.Reactive.Subjects;
+using Avalonia.Data;
+
+namespace Avalonia.ReactiveUI;
+
+public static class AvaloniaObjectReactiveExtensions
+{
+    /// <summary>
+    /// Gets a subject for an <see cref="AvaloniaProperty"/>.
+    /// </summary>
+    /// <param name="o">The object.</param>
+    /// <param name="property">The property.</param>
+    /// <param name="priority">
+    /// The priority with which binding values are written to the object.
+    /// </param>
+    /// <returns>
+    /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
+    /// property.
+    /// </returns>
+    public static ISubject<object?> GetSubject(
+        this AvaloniaObject o,
+        AvaloniaProperty property,
+        BindingPriority priority = BindingPriority.LocalValue)
+    {
+        return Subject.Create<object?>(
+            Observer.Create<object?>(x => o.SetValue(property, x, priority)),
+            o.GetObservable(property));
+    }
+
+    /// <summary>
+    /// Gets a subject for an <see cref="AvaloniaProperty"/>.
+    /// </summary>
+    /// <typeparam name="T">The property type.</typeparam>
+    /// <param name="o">The object.</param>
+    /// <param name="property">The property.</param>
+    /// <param name="priority">
+    /// The priority with which binding values are written to the object.
+    /// </param>
+    /// <returns>
+    /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
+    /// property.
+    /// </returns>
+    public static ISubject<T> GetSubject<T>(
+        this AvaloniaObject o,
+        AvaloniaProperty<T> property,
+        BindingPriority priority = BindingPriority.LocalValue)
+    {
+        return Subject.Create<T>(
+            Observer.Create<T>(x => o.SetValue(property, x, priority)),
+            o.GetObservable(property));
+    }
+
+    /// <summary>
+    /// Gets a subject for a <see cref="AvaloniaProperty"/>.
+    /// </summary>
+    /// <param name="o">The object.</param>
+    /// <param name="property">The property.</param>
+    /// <param name="priority">
+    /// The priority with which binding values are written to the object.
+    /// </param>
+    /// <returns>
+    /// An <see cref="ISubject{Object}"/> which can be used for two-way binding to/from the 
+    /// property.
+    /// </returns>
+    public static ISubject<BindingValue<object?>> GetBindingSubject(
+        this AvaloniaObject o,
+        AvaloniaProperty property,
+        BindingPriority priority = BindingPriority.LocalValue)
+    {
+        return Subject.Create<BindingValue<object?>>(
+            Observer.Create<BindingValue<object?>>(x =>
+            {
+                if (x.HasValue)
+                {
+                    o.SetValue(property, x.Value, priority);
+                }
+            }),
+            o.GetBindingObservable(property));
+    }
+
+    /// <summary>
+    /// Gets a subject for a <see cref="AvaloniaProperty"/>.
+    /// </summary>
+    /// <typeparam name="T">The property type.</typeparam>
+    /// <param name="o">The object.</param>
+    /// <param name="property">The property.</param>
+    /// <param name="priority">
+    /// The priority with which binding values are written to the object.
+    /// </param>
+    /// <returns>
+    /// An <see cref="ISubject{T}"/> which can be used for two-way binding to/from the 
+    /// property.
+    /// </returns>
+    public static ISubject<BindingValue<T>> GetBindingSubject<T>(
+        this AvaloniaObject o,
+        AvaloniaProperty<T> property,
+        BindingPriority priority = BindingPriority.LocalValue)
+    {
+        return Subject.Create<BindingValue<T>>(
+            Observer.Create<BindingValue<T>>(x =>
+            {
+                if (x.HasValue)
+                {
+                    o.SetValue(property, x.Value, priority);
+                }
+            }),
+            o.GetBindingObservable(property));
+    }
+}
diff --git a/src/Avalonia.Base/Threading/AvaloniaScheduler.cs b/src/Avalonia.ReactiveUI/AvaloniaScheduler.cs
similarity index 98%
rename from src/Avalonia.Base/Threading/AvaloniaScheduler.cs
rename to src/Avalonia.ReactiveUI/AvaloniaScheduler.cs
index 6423d86e7c..61c503e7a5 100644
--- a/src/Avalonia.Base/Threading/AvaloniaScheduler.cs
+++ b/src/Avalonia.ReactiveUI/AvaloniaScheduler.cs
@@ -1,8 +1,9 @@
 using System;
 using System.Reactive.Concurrency;
 using System.Reactive.Disposables;
+using Avalonia.Threading;
 
-namespace Avalonia.Threading
+namespace Avalonia.ReactiveUI
 {
     /// <summary>
     /// A reactive scheduler that uses Avalonia's <see cref="Dispatcher"/>.
diff --git a/src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj b/src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj
index ab543703d9..fb52b3b147 100644
--- a/src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj
+++ b/src/Avalonia.Themes.Fluent/Avalonia.Themes.Fluent.csproj
@@ -14,7 +14,6 @@
   </ItemGroup>
   <Import Project="..\..\build\NullableEnable.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\ApiDiff.props" />
   <Import Project="..\..\build\TrimmingEnable.props" />
 </Project>
diff --git a/src/Avalonia.Themes.Simple/Avalonia.Themes.Simple.csproj b/src/Avalonia.Themes.Simple/Avalonia.Themes.Simple.csproj
index 1dd6426b39..4aa6b66743 100644
--- a/src/Avalonia.Themes.Simple/Avalonia.Themes.Simple.csproj
+++ b/src/Avalonia.Themes.Simple/Avalonia.Themes.Simple.csproj
@@ -13,7 +13,6 @@
   </ItemGroup>
   <Import Project="..\..\build\NullableEnable.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\ApiDiff.props" />
   <Import Project="..\..\build\TrimmingEnable.props" />
 </Project>
diff --git a/src/Avalonia.X11/Glx/GlxContext.cs b/src/Avalonia.X11/Glx/GlxContext.cs
index def5228e94..88006f0b47 100644
--- a/src/Avalonia.X11/Glx/GlxContext.cs
+++ b/src/Avalonia.X11/Glx/GlxContext.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Threading;
 using Avalonia.OpenGL;
+using Avalonia.Reactive;
 namespace Avalonia.X11.Glx
 {
     class GlxContext : IGlContext
diff --git a/src/Avalonia.X11/X11Window.cs b/src/Avalonia.X11/X11Window.cs
index 810a806c8a..5bbcf3af8c 100644
--- a/src/Avalonia.X11/X11Window.cs
+++ b/src/Avalonia.X11/X11Window.cs
@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using Avalonia.Reactive;
 using System.Text;
 using System.Threading.Tasks;
 using System.Threading;
diff --git a/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj b/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
index 267bd2520e..da739c754c 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
+++ b/src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj
@@ -66,7 +66,6 @@
     <ProjectReference Include="..\..\Avalonia.Controls\Avalonia.Controls.csproj" />
     <ProjectReference Include="..\Avalonia.Markup\Avalonia.Markup.csproj" />
   </ItemGroup>
-  <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\ApiDiff.props" />
   <Import Project="..\..\..\build\DevAnalyzers.props" />
   <Import Project="..\..\..\build\TrimmingEnable.props" />
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
index 45e23db84f..170a31fd64 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/FindVisualAncestorNode.cs
@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Data.Core;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
index 77ffa24687..cb21df0507 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/ObservableStreamPlugin.cs
@@ -1,9 +1,9 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Linq;
 using System.Text;
 using Avalonia.Data.Core.Plugins;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
index ef11b06369..138e8ec671 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/PropertyInfoAccessorFactory.cs
@@ -5,6 +5,7 @@ using Avalonia.Data;
 using Avalonia.Data.Core;
 using Avalonia.Data.Core.Plugins;
 using Avalonia.Utilities;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
index 8489dd9d19..7c9f7559c6 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/CompiledBindings/TaskStreamPlugin.cs
@@ -1,10 +1,9 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Linq;
-using System.Reactive.Subjects;
 using System.Threading.Tasks;
 using Avalonia.Data;
 using Avalonia.Data.Core.Plugins;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
 {
@@ -30,7 +29,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions.CompiledBindings
                 case TaskStatus.Faulted:
                     return HandleCompleted(task);
                 default:
-                    var subject = new Subject<object>();
+                    var subject = new LightweightSubject<object>();
                     task.ContinueWith(
                             x => HandleCompleted(task).Subscribe(subject),
                             TaskScheduler.FromCurrentSynchronizationContext())
diff --git a/src/Markup/Avalonia.Markup.Xaml/Templates/TemplateContent.cs b/src/Markup/Avalonia.Markup.Xaml/Templates/TemplateContent.cs
index 07c79d7077..23166170db 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Templates/TemplateContent.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/Templates/TemplateContent.cs
@@ -7,7 +7,6 @@ namespace Avalonia.Markup.Xaml.Templates
     public static class TemplateContent
     {
         public static ControlTemplateResult Load(object templateContent)
-
         {
             if (templateContent is Func<IServiceProvider, object> direct)
             {
diff --git a/src/Markup/Avalonia.Markup/Avalonia.Markup.csproj b/src/Markup/Avalonia.Markup/Avalonia.Markup.csproj
index 753d577105..e3878b5bc6 100644
--- a/src/Markup/Avalonia.Markup/Avalonia.Markup.csproj
+++ b/src/Markup/Avalonia.Markup/Avalonia.Markup.csproj
@@ -12,7 +12,6 @@
   <ItemGroup>
     <ProjectReference Include="..\..\Avalonia.Base\Avalonia.Base.csproj" />
   </ItemGroup>
-  <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\System.Memory.props" />
   <Import Project="..\..\..\build\ApiDiff.props" />
   <Import Project="..\..\..\build\NullableEnable.props" />
diff --git a/src/Markup/Avalonia.Markup/Data/Binding.cs b/src/Markup/Avalonia.Markup/Data/Binding.cs
index 6f836a799a..66907f33d0 100644
--- a/src/Markup/Avalonia.Markup/Data/Binding.cs
+++ b/src/Markup/Avalonia.Markup/Data/Binding.cs
@@ -1,15 +1,8 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Reactive;
-using System.Reactive.Linq;
 using Avalonia.Controls;
-using Avalonia.Data.Converters;
 using Avalonia.Data.Core;
-using Avalonia.LogicalTree;
 using Avalonia.Markup.Parsers;
-using Avalonia.Reactive;
-using Avalonia.VisualTree;
 
 namespace Avalonia.Data
 {
diff --git a/src/Markup/Avalonia.Markup/Data/BindingBase.cs b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
index c035f0b05d..56aa930869 100644
--- a/src/Markup/Avalonia.Markup/Data/BindingBase.cs
+++ b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
@@ -1,9 +1,5 @@
-
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Linq;
-using System.Reactive;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Data.Converters;
 using Avalonia.Data.Core;
@@ -247,6 +243,7 @@ namespace Avalonia.Data
             // Content property is bound to a value which becomes the ContentPresenter's 
             // DataContext - it is from this that the child hosted by the ContentPresenter needs to
             // inherit its DataContext.
+
             return target.GetObservable(Visual.VisualParentProperty)
                 .Select(x =>
                 {
@@ -255,8 +252,9 @@ namespace Avalonia.Data
                 }).Switch();
         }
 
-        private class UpdateSignal : SingleSubscriberObservableBase<Unit>
+        private class UpdateSignal : SingleSubscriberObservableBase<object>
         {
+            private static readonly object s_val = new(); 
             private readonly AvaloniaObject _target;
             private readonly AvaloniaProperty _property;
 
@@ -280,7 +278,7 @@ namespace Avalonia.Data
             {
                 if (e.Property == _property)
                 {
-                    PublishNext(Unit.Default);
+                    PublishNext(s_val);
                 }
             }
         }
diff --git a/src/Markup/Avalonia.Markup/Data/MultiBinding.cs b/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
index 4693b0c617..1515ff2c90 100644
--- a/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
+++ b/src/Markup/Avalonia.Markup/Data/MultiBinding.cs
@@ -2,7 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Data.Converters;
 using Avalonia.Metadata;
 
diff --git a/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs b/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs
index 4dcdfb3c0e..4270063f87 100644
--- a/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs
+++ b/src/Markup/Avalonia.Markup/Data/TemplateBinding.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Globalization;
-using System.Reactive.Subjects;
 using Avalonia.Data.Converters;
 using Avalonia.Reactive;
 using Avalonia.Styling;
@@ -13,7 +12,7 @@ namespace Avalonia.Data
     public class TemplateBinding : SingleSubscriberObservableBase<object?>,
         IBinding,
         IDescription,
-        ISubject<object?>,
+        IAvaloniaSubject<object?>,
         ISetterValue
     {
         private bool _isSetterValue;
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
index 6e6a163989..a478af570a 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive;
 using Avalonia.Controls;
 using Avalonia.Data.Core;
 using Avalonia.Utilities;
@@ -64,7 +63,7 @@ namespace Avalonia.Markup.Parsers
         public static ExpressionObserver Build(
             Func<object> rootGetter,
             string expression,
-            IObservable<Unit> update,
+            IObservable<object> update,
             bool enableDataValidation = false,
             string? description = null,
             Func<string, string, Type>? typeResolver = null)
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
index f9a3a61736..4fc17e440b 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/ElementNameNode.cs
@@ -2,6 +2,7 @@
 using Avalonia.Controls;
 using Avalonia.Data.Core;
 using Avalonia.LogicalTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Parsers.Nodes
 {
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
index 697612ca12..ffbd34d492 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/FindAncestorNode.cs
@@ -1,6 +1,7 @@
 using System;
 using Avalonia.Data.Core;
 using Avalonia.LogicalTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Markup.Parsers.Nodes
 {
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
index c420a9df8d..ba1c1edffe 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/Nodes/StringIndexerNode.cs
@@ -5,7 +5,7 @@ using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Linq;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using System.Reflection;
 using Avalonia.Data;
 using Avalonia.Data.Core;
diff --git a/src/Skia/Avalonia.Skia/FramebufferRenderTarget.cs b/src/Skia/Avalonia.Skia/FramebufferRenderTarget.cs
index 1ae47c8b7a..05fad25f1b 100644
--- a/src/Skia/Avalonia.Skia/FramebufferRenderTarget.cs
+++ b/src/Skia/Avalonia.Skia/FramebufferRenderTarget.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Controls.Platform.Surfaces;
 using Avalonia.Platform;
 using Avalonia.Rendering;
diff --git a/src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs b/src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs
index 5bf1272c2f..4b3c7a016d 100644
--- a/src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs
+++ b/src/Skia/Avalonia.Skia/Gpu/OpenGl/GlRenderTarget.cs
@@ -1,5 +1,5 @@
 using System;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.OpenGL;
 using Avalonia.OpenGL.Surfaces;
 using Avalonia.Platform;
diff --git a/src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs b/src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs
index a7998353d9..e5fb182a3b 100644
--- a/src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs
+++ b/src/Skia/Avalonia.Skia/SurfaceRenderTarget.cs
@@ -1,6 +1,6 @@
 using System;
 using System.IO;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using Avalonia.Media;
 using Avalonia.Platform;
 using Avalonia.Rendering;
diff --git a/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj b/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
index fb7831415d..c61c276956 100644
--- a/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
+++ b/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
@@ -14,7 +14,6 @@
     <ProjectReference Include="..\..\..\packages\Avalonia\Avalonia.csproj" />
     <ProjectReference Include="..\Avalonia.Win32\Avalonia.Win32.csproj" />
   </ItemGroup>
-  <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\SharpDX.props" />
   <Import Project="..\..\..\build\HarfBuzzSharp.props" />
   <Import Project="..\..\..\build\JetBrains.Annotations.props" />
diff --git a/src/Windows/Avalonia.Win32/ClipboardImpl.cs b/src/Windows/Avalonia.Win32/ClipboardImpl.cs
index 6153c7c75c..82fd1109f4 100644
--- a/src/Windows/Avalonia.Win32/ClipboardImpl.cs
+++ b/src/Windows/Avalonia.Win32/ClipboardImpl.cs
@@ -1,6 +1,6 @@
 using System;
 using System.Linq;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Runtime.InteropServices;
 using System.Threading.Tasks;
 using Avalonia.Input;
diff --git a/src/Windows/Avalonia.Win32/OpenGl/WglContext.cs b/src/Windows/Avalonia.Win32/OpenGl/WglContext.cs
index d535efc5b7..b4002d8bc7 100644
--- a/src/Windows/Avalonia.Win32/OpenGl/WglContext.cs
+++ b/src/Windows/Avalonia.Win32/OpenGl/WglContext.cs
@@ -1,10 +1,10 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Disposables;
 using System.Threading;
 using Avalonia.OpenGL;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 using static Avalonia.Win32.OpenGl.WglConsts;
diff --git a/src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs b/src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs
index 2b8bf6f8bf..fdf36206d0 100644
--- a/src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs
+++ b/src/Windows/Avalonia.Win32/Win32NativeToManagedMenuExporter.cs
@@ -1,5 +1,5 @@
 using System.Collections.Generic;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Platform;
diff --git a/src/Windows/Avalonia.Win32/Win32Platform.cs b/src/Windows/Avalonia.Win32/Win32Platform.cs
index 3f220f0f09..a1af5fa82a 100644
--- a/src/Windows/Avalonia.Win32/Win32Platform.cs
+++ b/src/Windows/Avalonia.Win32/Win32Platform.cs
@@ -3,7 +3,7 @@ using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
-using System.Reactive.Disposables;
+using Avalonia.Reactive;
 using System.Runtime.InteropServices;
 using System.Threading;
 using Avalonia.Controls;
diff --git a/src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindow.cs b/src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindow.cs
index 32019f4c15..5be25a3d4b 100644
--- a/src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindow.cs
+++ b/src/Windows/Avalonia.Win32/WinRT/Composition/WinUiCompositedWindow.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Numerics;
-using System.Reactive.Disposables;
 using System.Threading;
 using Avalonia.OpenGL.Egl;
+using Avalonia.Reactive;
 using Avalonia.Win32.Interop;
 using MicroCom.Runtime;
 
diff --git a/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs b/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
index ba1bfda949..94e9c0c814 100644
--- a/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
+++ b/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
@@ -2,33 +2,30 @@ using System;
 using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
+using Avalonia.Reactive;
+using Avalonia.Reactive;
 using Avalonia.Controls.Platform;
 using Avalonia.Logging;
+using Avalonia.Threading;
 
 namespace Avalonia.Win32
 {
     internal class WindowsMountedVolumeInfoListener : IDisposable
     {
-        private readonly CompositeDisposable _disposables;
+        private readonly IDisposable _disposable;
         private bool _beenDisposed = false;
         private ObservableCollection<MountedVolumeInfo> mountedDrives;
 
         public WindowsMountedVolumeInfoListener(ObservableCollection<MountedVolumeInfo> mountedDrives)
         {
             this.mountedDrives = mountedDrives;
-            _disposables = new CompositeDisposable();
 
-            var pollTimer = Observable.Interval(TimeSpan.FromSeconds(1))
-                                      .Subscribe(Poll);
+            _disposable = DispatcherTimer.Run(Poll, TimeSpan.FromSeconds(1));
 
-            _disposables.Add(pollTimer);
-
-            Poll(0);
+            Poll();
         }
 
-        private void Poll(long _)
+        private bool Poll()
         {
             var allDrives = DriveInfo.GetDrives();
 
@@ -56,13 +53,14 @@ namespace Avalonia.Win32
                                 .ToArray();
 
             if (mountedDrives.SequenceEqual(mountVolInfos))
-                return;
+                return true;
             else
             {
                 mountedDrives.Clear();
 
                 foreach (var i in mountVolInfos)
                     mountedDrives.Add(i);
+                return true;
             }
         }
 
@@ -72,7 +70,7 @@ namespace Avalonia.Win32
             {
                 if (disposing)
                 {
-
+                    _disposable.Dispose();
                 }
                 _beenDisposed = true;
             }
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
index 547b2cb176..030d6ba215 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
@@ -1036,7 +1036,7 @@ namespace Avalonia.Base.UnitTests
         }
 
         [Fact]
-        public async Task Bind_With_Scheduler_Executes_On_Scheduler()
+        public async Task Bind_With_Scheduler_Executes_On_UI_Thread()
         {
             var target = new Class1();
             var source = new Subject<double>();
@@ -1047,7 +1047,6 @@ namespace Avalonia.Base.UnitTests
                 .Returns(() => Thread.CurrentThread.ManagedThreadId == currentThreadId);
 
             var services = new TestServices(
-                scheduler: AvaloniaScheduler.Instance,
                 threadingInterface: threadingInterfaceMock.Object);
 
             using (UnitTestApplication.Start(services))
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
index 435980bd9a..e6864e6806 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
@@ -41,7 +41,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Completes()
         {
-            var update = new Subject<Unit>();
+            var update = new Subject<object>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -54,7 +54,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Errors()
         {
-            var update = new Subject<Unit>();
+            var update = new Subject<object>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -87,7 +87,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Should_Unsubscribe_From_Update_Observable()
         {
             var scheduler = new TestScheduler();
-            var update = scheduler.CreateColdObservable<Unit>();
+            var update = scheduler.CreateColdObservable<object>();
             var data = new { Foo = "foo" };
             var target = ExpressionObserver.Create(() => data, o => o.Foo, update);
             var result = new List<object>();
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
index 144d9e6668..6554be2e89 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
@@ -359,7 +359,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Empty_Expression_Should_Track_Root()
         {
             var data = new Class1 { Foo = "foo" };
-            var update = new Subject<Unit>();
+            var update = new Subject<object>();
             var target = ExpressionObserver.Create(() => data.Foo, o => o, update);
             var result = new List<object>();
 
@@ -533,7 +533,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
             var first = new Class1 { Foo = "foo" };
             var second = new Class1 { Foo = "bar" };
             var root = first;
-            var update = new Subject<Unit>();
+            var update = new Subject<object>();
             var target = ExpressionObserver.Create(() => root, o => o.Foo, update);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));
@@ -640,7 +640,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void RootGetter_Is_Reevaluated_On_Subscribe()
         {
             var data = "foo";
-            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<Unit>(), null);
+            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<object>(), null);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));
 
diff --git a/tests/Avalonia.Base.UnitTests/Styling/StyleActivatorExtensions.cs b/tests/Avalonia.Base.UnitTests/Styling/StyleActivatorExtensions.cs
index e69eae43f0..9f7d9854fd 100644
--- a/tests/Avalonia.Base.UnitTests/Styling/StyleActivatorExtensions.cs
+++ b/tests/Avalonia.Base.UnitTests/Styling/StyleActivatorExtensions.cs
@@ -3,6 +3,7 @@ using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Reactive;
 using Avalonia.Styling.Activators;
+using Observable = Avalonia.Reactive.Observable;
 
 namespace Avalonia.Base.UnitTests.Styling
 {
@@ -10,12 +11,12 @@ namespace Avalonia.Base.UnitTests.Styling
     {
         public static IDisposable Subscribe(this IStyleActivator activator, Action<bool> action)
         {
-            return activator.ToObservable().Subscribe(action);
+            return Observable.Subscribe(activator.ToObservable(), action);
         }
 
         public static async Task<bool> Take(this IStyleActivator activator, int value)
         {
-            return await activator.ToObservable().Take(value);
+            return await System.Reactive.Linq.Observable.Take(activator.ToObservable(), value);
         }
 
         public static IObservable<bool> ToObservable(this IStyleActivator activator)
diff --git a/tests/Avalonia.IntegrationTests.Appium/Avalonia.IntegrationTests.Appium.csproj b/tests/Avalonia.IntegrationTests.Appium/Avalonia.IntegrationTests.Appium.csproj
index 03d9332051..57338a1e08 100644
--- a/tests/Avalonia.IntegrationTests.Appium/Avalonia.IntegrationTests.Appium.csproj
+++ b/tests/Avalonia.IntegrationTests.Appium/Avalonia.IntegrationTests.Appium.csproj
@@ -15,4 +15,5 @@
   </ItemGroup>
 
   <Import Project="..\..\build\XUnit.props" />
+  <Import Project="..\..\build\Rx.props" />
 </Project>
diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
index 53c186111d..656c2cbbbc 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests.cs
@@ -334,7 +334,7 @@ namespace Avalonia.Markup.UnitTests.Data
                 Path = "Foo",
             };
 
-            var result = binding.Initiate(target, TextBox.TextProperty).Subject;
+            var result = binding.Initiate(target, TextBox.TextProperty).Value;
 
             Assert.IsType<DefaultValueConverter>(((BindingExpression)result).Converter);
         }
@@ -350,7 +350,7 @@ namespace Avalonia.Markup.UnitTests.Data
                 Path = "Foo",
             };
 
-            var result = binding.Initiate(target, TextBox.TextProperty).Subject;
+            var result = binding.Initiate(target, TextBox.TextProperty).Value;
 
             Assert.Same(converter.Object, ((BindingExpression)result).Converter);
         }
@@ -367,7 +367,7 @@ namespace Avalonia.Markup.UnitTests.Data
                 Path = "Bar",
             };
 
-            var result = binding.Initiate(target, TextBox.TextProperty).Subject;
+            var result = binding.Initiate(target, TextBox.TextProperty).Value;
 
             Assert.Same("foo", ((BindingExpression)result).ConverterParameter);
         }
diff --git a/tests/Avalonia.Markup.UnitTests/Data/BindingTests_DataValidation.cs b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_DataValidation.cs
index 44829aae1e..45deb97f51 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/BindingTests_DataValidation.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/BindingTests_DataValidation.cs
@@ -20,7 +20,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             var target = new Binding(nameof(Class1.Foo));
             var instanced = target.Initiate(textBlock, TextBlock.TextProperty, enableDataValidation: false);
-            var subject = (BindingExpression)instanced.Subject;
+            var subject = (BindingExpression)instanced.Value;
             object result = null;
 
             subject.Subscribe(x => result = x);
@@ -38,7 +38,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             var target = new Binding(nameof(Class1.Foo));
             var instanced = target.Initiate(textBlock, TextBlock.TextProperty, enableDataValidation: true);
-            var subject = (BindingExpression)instanced.Subject;
+            var subject = (BindingExpression)instanced.Value;
             object result = null;
 
             subject.Subscribe(x => result = x);
@@ -56,7 +56,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             var target = new Binding(nameof(Class1.Foo)) { Priority = BindingPriority.Template };
             var instanced = target.Initiate(textBlock, TextBlock.TextProperty, enableDataValidation: true);
-            var subject = (BindingExpression)instanced.Subject;
+            var subject = (BindingExpression)instanced.Value;
             object result = null;
 
             subject.Subscribe(x => result = x);
diff --git a/tests/Avalonia.Markup.UnitTests/Data/MultiBindingTests.cs b/tests/Avalonia.Markup.UnitTests/Data/MultiBindingTests.cs
index cb5c625c35..a7ef2c4e4d 100644
--- a/tests/Avalonia.Markup.UnitTests/Data/MultiBindingTests.cs
+++ b/tests/Avalonia.Markup.UnitTests/Data/MultiBindingTests.cs
@@ -84,6 +84,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             target.Bind(TextBlock.TextProperty, binding);
 
+            Assert.NotNull(target.Text);
             Assert.Equal("fallback", target.Text);
         }
 
@@ -106,6 +107,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             target.Bind(TextBlock.TextProperty, binding);
 
+            Assert.NotNull(target.Text);
             Assert.Equal("(null)", target.Text);
         }
 
@@ -128,6 +130,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             target.Bind(TextBlock.TextProperty, binding);
 
+            Assert.NotNull(target.Text);
             Assert.Equal("1,2,(unset)", target.Text);
         }
 
@@ -150,6 +153,7 @@ namespace Avalonia.Markup.UnitTests.Data
 
             target.Bind(TextBlock.TextProperty, binding);
 
+            Assert.NotNull(target.Text);
             Assert.Equal("1,2,Fallback", target.Text);
         }
 
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_GetSubject.cs b/tests/Avalonia.ReactiveUI.UnitTests/AvaloniaObjectTests_GetSubject.cs
similarity index 95%
rename from tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_GetSubject.cs
rename to tests/Avalonia.ReactiveUI.UnitTests/AvaloniaObjectTests_GetSubject.cs
index 0f2e8ebc21..81f04dc53e 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_GetSubject.cs
+++ b/tests/Avalonia.ReactiveUI.UnitTests/AvaloniaObjectTests_GetSubject.cs
@@ -1,9 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Linq;
 using Xunit;
 
-namespace Avalonia.Base.UnitTests
+namespace Avalonia.ReactiveUI.UnitTests
 {
     public class AvaloniaObjectTests_GetSubject
     {
diff --git a/tests/Avalonia.UnitTests/TestServices.cs b/tests/Avalonia.UnitTests/TestServices.cs
index c421adaf21..2eaa8bf1e5 100644
--- a/tests/Avalonia.UnitTests/TestServices.cs
+++ b/tests/Avalonia.UnitTests/TestServices.cs
@@ -71,7 +71,6 @@ namespace Avalonia.UnitTests
             IRuntimePlatform platform = null,
             IPlatformRenderInterface renderInterface = null,
             IRenderTimer renderLoop = null,
-            IScheduler scheduler = null,
             ICursorFactory standardCursorFactory = null,
             Func<IStyle> theme = null,
             IPlatformThreadingInterface threadingInterface = null,
@@ -91,7 +90,6 @@ namespace Avalonia.UnitTests
             RenderInterface = renderInterface;
             FontManagerImpl = fontManagerImpl;
             TextShaperImpl = textShaperImpl;
-            Scheduler = scheduler;
             StandardCursorFactory = standardCursorFactory;
             Theme = theme;
             ThreadingInterface = threadingInterface;
@@ -110,7 +108,6 @@ namespace Avalonia.UnitTests
         public IPlatformRenderInterface RenderInterface { get; }
         public IFontManagerImpl FontManagerImpl { get; }
         public ITextShaperImpl TextShaperImpl { get; }
-        public IScheduler Scheduler { get; }
         public ICursorFactory StandardCursorFactory { get; }
         public Func<IStyle> Theme { get; }
         public IPlatformThreadingInterface ThreadingInterface { get; }
@@ -149,7 +146,6 @@ namespace Avalonia.UnitTests
                 renderInterface: renderInterface ?? RenderInterface,
                 fontManagerImpl: fontManagerImpl ?? FontManagerImpl,
                 textShaperImpl: textShaperImpl ?? TextShaperImpl,
-                scheduler: scheduler ?? Scheduler,
                 standardCursorFactory: standardCursorFactory ?? StandardCursorFactory,
                 theme: theme ?? Theme,
                 threadingInterface: threadingInterface ?? ThreadingInterface,
diff --git a/tests/Avalonia.UnitTests/UnitTestApplication.cs b/tests/Avalonia.UnitTests/UnitTestApplication.cs
index 03e19359c3..82626877d0 100644
--- a/tests/Avalonia.UnitTests/UnitTestApplication.cs
+++ b/tests/Avalonia.UnitTests/UnitTestApplication.cs
@@ -66,7 +66,6 @@ namespace Avalonia.UnitTests
                 .Bind<IFontManagerImpl>().ToConstant(Services.FontManagerImpl)
                 .Bind<ITextShaperImpl>().ToConstant(Services.TextShaperImpl)
                 .Bind<IPlatformThreadingInterface>().ToConstant(Services.ThreadingInterface)
-                .Bind<IScheduler>().ToConstant(Services.Scheduler)
                 .Bind<ICursorFactory>().ToConstant(Services.StandardCursorFactory)
                 .Bind<IWindowingPlatform>().ToConstant(Services.WindowingPlatform)
                 .Bind<PlatformHotkeyConfiguration>().ToSingleton<PlatformHotkeyConfiguration>();

From ccffa6acab883f7ad7d59bf256f1b229627d481e Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Tue, 20 Dec 2022 21:44:58 -0500
Subject: [PATCH 069/157] Reuse observer instance where possible

---
 src/Avalonia.Base/Layout/Layoutable.cs           | 16 ++++++----------
 src/Avalonia.Base/Media/Brush.cs                 |  8 +++-----
 src/Avalonia.Base/Media/DashStyle.cs             | 10 ++++------
 .../Media/ExperimentalAcrylicMaterial.cs         |  8 +++-----
 src/Avalonia.Base/Media/Geometry.cs              |  3 ++-
 src/Avalonia.Base/Media/ScaleTransform.cs        | 12 ++++++++++--
 src/Avalonia.Base/Media/SkewTransform.cs         | 12 ++++++++++--
 src/Avalonia.Base/Media/TranslateTransform.cs    | 12 ++++++++++--
 src/Avalonia.Controls/DefinitionBase.cs          |  8 +++-----
 src/Avalonia.Controls/Panel.cs                   |  8 ++++++--
 10 files changed, 57 insertions(+), 40 deletions(-)

diff --git a/src/Avalonia.Base/Layout/Layoutable.cs b/src/Avalonia.Base/Layout/Layoutable.cs
index 9a899ba084..775b8adddd 100644
--- a/src/Avalonia.Base/Layout/Layoutable.cs
+++ b/src/Avalonia.Base/Layout/Layoutable.cs
@@ -470,14 +470,12 @@ namespace Avalonia.Layout
         protected static void AffectsMeasure<T>(params AvaloniaProperty[] properties)
             where T : Layoutable
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                (e.Sender as T)?.InvalidateMeasure();
-            }
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => (e.Sender as T)?.InvalidateMeasure());
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 
@@ -493,14 +491,12 @@ namespace Avalonia.Layout
         protected static void AffectsArrange<T>(params AvaloniaProperty[] properties)
             where T : Layoutable
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                (e.Sender as T)?.InvalidateArrange();
-            }
+            var invalidate = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => (e.Sender as T)?.InvalidateArrange());
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                property.Changed.Subscribe(invalidate);
             }
         }
 
diff --git a/src/Avalonia.Base/Media/Brush.cs b/src/Avalonia.Base/Media/Brush.cs
index a1afb458c6..b9a560ad8f 100644
--- a/src/Avalonia.Base/Media/Brush.cs
+++ b/src/Avalonia.Base/Media/Brush.cs
@@ -104,14 +104,12 @@ namespace Avalonia.Media
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : Brush
         {
-            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                (e.Sender as T)?.RaiseInvalidated(EventArgs.Empty);
-            }
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => (e.Sender as T)?.RaiseInvalidated(EventArgs.Empty));
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(e => Invalidate(e));
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 
diff --git a/src/Avalonia.Base/Media/DashStyle.cs b/src/Avalonia.Base/Media/DashStyle.cs
index 92b07191e6..4749bfa401 100644
--- a/src/Avalonia.Base/Media/DashStyle.cs
+++ b/src/Avalonia.Base/Media/DashStyle.cs
@@ -52,13 +52,11 @@ namespace Avalonia.Media
 
         static DashStyle()
         {
-            void RaiseInvalidated(AvaloniaPropertyChangedEventArgs e)
-            {
-                ((DashStyle)e.Sender).Invalidated?.Invoke(e.Sender, EventArgs.Empty);
-            }
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => ((DashStyle)e.Sender).Invalidated?.Invoke(e.Sender, EventArgs.Empty));
 
-            DashesProperty.Changed.Subscribe(RaiseInvalidated);
-            OffsetProperty.Changed.Subscribe(RaiseInvalidated);
+            DashesProperty.Changed.Subscribe(invalidateObserver);
+            OffsetProperty.Changed.Subscribe(invalidateObserver);
         }
 
         /// <summary>
diff --git a/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs b/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
index b7a186dde4..22d5a29870 100644
--- a/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
+++ b/src/Avalonia.Base/Media/ExperimentalAcrylicMaterial.cs
@@ -275,14 +275,12 @@ namespace Avalonia.Media
         protected static void AffectsRender<T>(params AvaloniaProperty[] properties)
             where T : ExperimentalAcrylicMaterial
         {
-            static void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                (e.Sender as T)?.RaiseInvalidated(EventArgs.Empty);
-            }
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => (e.Sender as T)?.RaiseInvalidated(EventArgs.Empty));
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(e => Invalidate(e));
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 
diff --git a/src/Avalonia.Base/Media/Geometry.cs b/src/Avalonia.Base/Media/Geometry.cs
index dd162c1e71..9ef32c7d09 100644
--- a/src/Avalonia.Base/Media/Geometry.cs
+++ b/src/Avalonia.Base/Media/Geometry.cs
@@ -118,9 +118,10 @@ namespace Avalonia.Media
         /// </remarks>
         protected static void AffectsGeometry(params AvaloniaProperty[] properties)
         {
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(AffectsGeometryInvalidate);
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(AffectsGeometryInvalidate);
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 
diff --git a/src/Avalonia.Base/Media/ScaleTransform.cs b/src/Avalonia.Base/Media/ScaleTransform.cs
index 86163df471..fca2f4bf2a 100644
--- a/src/Avalonia.Base/Media/ScaleTransform.cs
+++ b/src/Avalonia.Base/Media/ScaleTransform.cs
@@ -26,8 +26,6 @@ namespace Avalonia.Media
         /// </summary>
         public ScaleTransform()
         {
-            this.GetObservable(ScaleXProperty).Subscribe(_ => RaiseChanged());
-            this.GetObservable(ScaleYProperty).Subscribe(_ => RaiseChanged());
         }
 
         /// <summary>
@@ -64,5 +62,15 @@ namespace Avalonia.Media
         /// Gets the transform's <see cref="Matrix"/>.
         /// </summary>
         public override Matrix Value => Matrix.CreateScale(ScaleX, ScaleY);
+        
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == ScaleXProperty || change.Property == ScaleYProperty)
+            {
+                RaiseChanged();
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Base/Media/SkewTransform.cs b/src/Avalonia.Base/Media/SkewTransform.cs
index 2de2d734c5..d268bee778 100644
--- a/src/Avalonia.Base/Media/SkewTransform.cs
+++ b/src/Avalonia.Base/Media/SkewTransform.cs
@@ -26,8 +26,6 @@ namespace Avalonia.Media
         /// </summary>
         public SkewTransform()
         {
-            this.GetObservable(AngleXProperty).Subscribe(_ => RaiseChanged());
-            this.GetObservable(AngleYProperty).Subscribe(_ => RaiseChanged());
         }
 
         /// <summary>
@@ -63,5 +61,15 @@ namespace Avalonia.Media
         /// Gets the transform's <see cref="Matrix"/>.
         /// </summary>
         public override Matrix Value => Matrix.CreateSkew(Matrix.ToRadians(AngleX), Matrix.ToRadians(AngleY));
+        
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == AngleXProperty || change.Property == AngleYProperty)
+            {
+                RaiseChanged();
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Base/Media/TranslateTransform.cs b/src/Avalonia.Base/Media/TranslateTransform.cs
index 75528a4261..1d0169a62c 100644
--- a/src/Avalonia.Base/Media/TranslateTransform.cs
+++ b/src/Avalonia.Base/Media/TranslateTransform.cs
@@ -26,8 +26,6 @@ namespace Avalonia.Media
         /// </summary>
         public TranslateTransform()
         {
-            this.GetObservable(XProperty).Subscribe(_ => RaiseChanged());
-            this.GetObservable(YProperty).Subscribe(_ => RaiseChanged());
         }
 
         /// <summary>
@@ -64,5 +62,15 @@ namespace Avalonia.Media
         /// Gets the transform's <see cref="Matrix"/>.
         /// </summary>
         public override Matrix Value => Matrix.CreateTranslation(X, Y);
+        
+        protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs change)
+        {
+            base.OnPropertyChanged(change);
+
+            if (change.Property == XProperty || change.Property == YProperty)
+            {
+                RaiseChanged();
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Controls/DefinitionBase.cs b/src/Avalonia.Controls/DefinitionBase.cs
index f93f613583..5c35a09f1c 100644
--- a/src/Avalonia.Controls/DefinitionBase.cs
+++ b/src/Avalonia.Controls/DefinitionBase.cs
@@ -806,14 +806,12 @@ namespace Avalonia.Controls
         /// <param name="properties">The properties.</param>
         protected static void AffectsParentMeasure(params AvaloniaProperty[] properties)
         {
-            void Invalidate(AvaloniaPropertyChangedEventArgs e)
-            {
-                (e.Sender as DefinitionBase)?.Parent?.InvalidateMeasure();
-            }
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => (e.Sender as DefinitionBase)?.Parent?.InvalidateMeasure());
 
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(Invalidate);
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
     }
diff --git a/src/Avalonia.Controls/Panel.cs b/src/Avalonia.Controls/Panel.cs
index a643edc420..007d18c813 100644
--- a/src/Avalonia.Controls/Panel.cs
+++ b/src/Avalonia.Controls/Panel.cs
@@ -87,9 +87,11 @@ namespace Avalonia.Controls
         protected static void AffectsParentArrange<TPanel>(params AvaloniaProperty[] properties)
             where TPanel : Panel
         {
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => AffectsParentArrangeInvalidate<TPanel>(e));
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(AffectsParentArrangeInvalidate<TPanel>);
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 
@@ -100,9 +102,11 @@ namespace Avalonia.Controls
         protected static void AffectsParentMeasure<TPanel>(params AvaloniaProperty[] properties)
             where TPanel : Panel
         {
+            var invalidateObserver = new AnonymousObserver<AvaloniaPropertyChangedEventArgs>(
+                static e => AffectsParentMeasureInvalidate<TPanel>(e));
             foreach (var property in properties)
             {
-                property.Changed.Subscribe(AffectsParentMeasureInvalidate<TPanel>);
+                property.Changed.Subscribe(invalidateObserver);
             }
         }
 

From adbb7dc7c920ed211727b9bad8bdb1d031d20a4b Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Tue, 20 Dec 2022 22:09:54 -0500
Subject: [PATCH 070/157] Fix reactive references in missed projects

---
 samples/PlatformSanityChecks/PlatformSanityChecks.csproj | 1 +
 samples/Previewer/Previewer.csproj                       | 3 ++-
 src/Avalonia.Base/Avalonia.Base.csproj                   | 1 +
 src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs      | 2 +-
 4 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/samples/PlatformSanityChecks/PlatformSanityChecks.csproj b/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
index 5c743aabdb..5f61a08f3c 100644
--- a/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
+++ b/samples/PlatformSanityChecks/PlatformSanityChecks.csproj
@@ -11,4 +11,5 @@
     <ProjectReference Include="..\..\src\Avalonia.X11\Avalonia.X11.csproj" />
   </ItemGroup>
 
+  <Import Project="..\..\build\Rx.props" />
 </Project>
diff --git a/samples/Previewer/Previewer.csproj b/samples/Previewer/Previewer.csproj
index 2cc84168dc..76c1ba7b69 100644
--- a/samples/Previewer/Previewer.csproj
+++ b/samples/Previewer/Previewer.csproj
@@ -12,7 +12,8 @@
   <ItemGroup>
     <ProjectReference Include="..\..\src\Avalonia.Themes.Simple\Avalonia.Themes.Simple.csproj" />
   </ItemGroup>
-  
+
+  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\SampleApp.props" />
   <Import Project="..\..\build\ReferenceCoreLibraries.props" />
 </Project>
diff --git a/src/Avalonia.Base/Avalonia.Base.csproj b/src/Avalonia.Base/Avalonia.Base.csproj
index d40fe1e6f8..e6c13d251f 100644
--- a/src/Avalonia.Base/Avalonia.Base.csproj
+++ b/src/Avalonia.Base/Avalonia.Base.csproj
@@ -38,6 +38,7 @@
     <InternalsVisibleTo Include="Avalonia.Native, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.FreeDesktop, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.X11, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Browser, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.OpenGL, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Skia, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Controls.UnitTests, PublicKey=$(AvaloniaPublicKey)" />
diff --git a/src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs b/src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs
index e56efdb4a8..4d3d8dcd97 100644
--- a/src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs
+++ b/src/Browser/Avalonia.Browser/Skia/BrowserSkiaGpu.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using Avalonia.Platform;
 using Avalonia.Skia;
+using Avalonia.Reactive;
 
 namespace Avalonia.Browser.Skia
 {

From bfdd66ac5e89fbf3e12488492ea99cc9d5546fdd Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Tue, 20 Dec 2022 23:25:36 -0500
Subject: [PATCH 071/157] Remove System.Reactive from Diagnostics package as
 well

---
 src/Avalonia.Base/Reactive/Observable.cs      |  9 ++++
 .../Reactive/SerialDisposableValue.cs         | 35 ++++++++++++
 .../Avalonia.Diagnostics.csproj               |  1 -
 .../Diagnostics/DevTools.cs                   | 17 +++---
 .../Diagnostics/ViewModels/EventTreeNode.cs   |  1 +
 .../Diagnostics/ViewModels/LogicalTreeNode.cs |  2 +-
 .../Diagnostics/ViewModels/MainViewModel.cs   | 14 ++---
 .../Diagnostics/ViewModels/TreeNode.cs        | 18 ++-----
 .../Diagnostics/ViewModels/VisualTreeNode.cs  | 54 +++++++++++--------
 .../Views/LayoutExplorerView.axaml.cs         |  1 +
 .../Diagnostics/Views/MainWindow.xaml.cs      | 30 ++++++-----
 11 files changed, 118 insertions(+), 64 deletions(-)
 create mode 100644 src/Avalonia.Base/Reactive/SerialDisposableValue.cs

diff --git a/src/Avalonia.Base/Reactive/Observable.cs b/src/Avalonia.Base/Reactive/Observable.cs
index 5191efa910..1009829429 100644
--- a/src/Avalonia.Base/Reactive/Observable.cs
+++ b/src/Avalonia.Base/Reactive/Observable.cs
@@ -44,6 +44,15 @@ internal static class Observable
                 }, obs.OnError, obs.OnCompleted));
         });
     }
+
+    public static IObservable<TSource> StartWith<TSource>(this IObservable<TSource> source, TSource value)
+    {
+        return Create<TSource>(obs =>
+        {
+            obs.OnNext(value);
+            return source.Subscribe(obs);
+        });
+    }
     
     public static IObservable<TSource> Where<TSource>(this IObservable<TSource> source, Func<TSource, bool> predicate)
     {
diff --git a/src/Avalonia.Base/Reactive/SerialDisposableValue.cs b/src/Avalonia.Base/Reactive/SerialDisposableValue.cs
new file mode 100644
index 0000000000..9eaf6343bf
--- /dev/null
+++ b/src/Avalonia.Base/Reactive/SerialDisposableValue.cs
@@ -0,0 +1,35 @@
+using System;
+using System.Threading;
+
+namespace Avalonia.Reactive;
+
+/// <summary>
+/// Represents a disposable resource whose underlying disposable resource can be replaced by another disposable resource, causing automatic disposal of the previous underlying disposable resource.
+/// </summary>
+internal sealed class SerialDisposableValue : IDisposable
+{
+    private IDisposable? _current;
+    private bool _disposed;
+    
+    public IDisposable? Disposable
+    {
+        get => _current;
+        set
+        {
+            _current?.Dispose();
+            _current = value;
+            
+            if (_disposed)
+            {
+                _current?.Dispose();
+                _current = null;
+            }
+        }
+    }
+
+    public void Dispose()
+    {
+        _disposed = true;
+        _current?.Dispose();
+    }
+}
diff --git a/src/Avalonia.Diagnostics/Avalonia.Diagnostics.csproj b/src/Avalonia.Diagnostics/Avalonia.Diagnostics.csproj
index fe694b5730..65d1bea298 100644
--- a/src/Avalonia.Diagnostics/Avalonia.Diagnostics.csproj
+++ b/src/Avalonia.Diagnostics/Avalonia.Diagnostics.csproj
@@ -23,7 +23,6 @@
     <PackageReference Include="Microsoft.CodeAnalysis.Common" Version="3.8.0" />
   </ItemGroup>
   <Import Project="..\..\build\EmbedXaml.props" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
   <Import Project="..\..\build\ApiDiff.props" />
   <Import Project="..\..\build\NullableEnable.props" />
diff --git a/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs b/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
index 9b4e13959b..e8cdcfa37b 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/DevTools.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Views;
 using Avalonia.Input;
@@ -72,7 +71,11 @@ namespace Avalonia.Diagnostics
             {
                 throw new ArgumentNullException(nameof(application));
             }
-            var result = Disposable.Empty;
+
+            var openedDisposable = new SerialDisposableValue();
+            var result = new CompositeDisposable(2);
+            result.Add(openedDisposable);
+            
             // Skip if call on Design Mode
             if (!Avalonia.Controls.Design.IsDesignMode
                 && !s_attachedToApplication)
@@ -90,13 +93,15 @@ namespace Avalonia.Diagnostics
                 {
                     s_attachedToApplication = true;
 
-                    ObservableExtensions.Subscribe(application.InputManager.PreProcess.OfType<RawKeyEventArgs>(), e =>
+                    result.Add(application.InputManager.PreProcess.Subscribe(e =>
                     {
-                        if (options.Gesture.Matches(e))
+                        if (e is RawKeyEventArgs keyEventArgs
+                            && keyEventArgs.Type == RawKeyEventType.KeyUp
+                            && options.Gesture.Matches(keyEventArgs))
                         {
-                          result =  Open(application, options, owner);
+                            openedDisposable.Disposable = Open(application, options, owner);
                         }
-                    });
+                    }));
 
                 }
             }
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/EventTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/EventTreeNode.cs
index 7da43a51b7..0140281d50 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/EventTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/EventTreeNode.cs
@@ -4,6 +4,7 @@ using Avalonia.Diagnostics.Views;
 using Avalonia.Interactivity;
 using Avalonia.Threading;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
index 7c6246701a..3048431af9 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/LogicalTreeNode.cs
@@ -1,10 +1,10 @@
 using System;
-using System.Reactive.Disposables;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.LogicalTree;
 using Lifetimes = Avalonia.Controls.ApplicationLifetimes;
 using System.Linq;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
index 52535aa991..3870cad7c5 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/MainViewModel.cs
@@ -1,11 +1,11 @@
 using System;
 using System.ComponentModel;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Diagnostics.Models;
 using Avalonia.Input;
 using Avalonia.Metadata;
 using Avalonia.Threading;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -50,15 +50,15 @@ namespace Avalonia.Diagnostics.ViewModels
             }
             else
             {
-#nullable disable
-                _pointerOverSubscription = InputManager.Instance.PreProcess
-                    .OfType<Input.Raw.RawPointerEventArgs>()
+                _pointerOverSubscription = InputManager.Instance!.PreProcess
                     .Subscribe(e =>
                         {
-                            PointerOverRoot = e.Root;
-                            PointerOverElement = e.Root.InputHitTest(e.Position);
+                            if (e is Input.Raw.RawPointerEventArgs pointerEventArgs)
+                            {
+                                PointerOverRoot = pointerEventArgs.Root;
+                                PointerOverElement = pointerEventArgs.Root.InputHitTest(pointerEventArgs.Position);
+                            }
                         });
-#nullable restore
             }
             Console = new ConsoleViewModel(UpdateConsoleContext);
         }
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNode.cs
index 65bfd7fc36..aafaa096e3 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/TreeNode.cs
@@ -1,11 +1,11 @@
 using System;
 using System.Collections.Specialized;
-using System.Reactive;
-using System.Reactive.Linq;
+using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Primitives;
 using Avalonia.LogicalTree;
 using Avalonia.Media;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.ViewModels
 {
@@ -28,18 +28,8 @@ namespace Avalonia.Diagnostics.ViewModels
             {
                 ElementName = control.Name;
 
-                var removed = Observable.FromEventPattern<LogicalTreeAttachmentEventArgs>(
-                    x => control.DetachedFromLogicalTree += x,
-                    x => control.DetachedFromLogicalTree -= x);
-                var classesChanged = Observable.FromEventPattern<
-                        NotifyCollectionChangedEventHandler,
-                        NotifyCollectionChangedEventArgs>(
-                        x => control.Classes.CollectionChanged += x,
-                        x => control.Classes.CollectionChanged -= x)
-                    .TakeUntil(removed);
-
-                _classesSubscription = classesChanged.Select(_ => Unit.Default)
-                    .StartWith(Unit.Default)
+                _classesSubscription = ((IObservable<object?>)control.Classes.GetWeakCollectionChangedObservable())
+                    .StartWith(null)
                     .Subscribe(_ =>
                     {
                         if (control.Classes.Count > 0)
diff --git a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
index e44b852372..f9fb0d18ef 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/ViewModels/VisualTreeNode.cs
@@ -1,12 +1,11 @@
 using System;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
 using Avalonia.Collections;
 using Avalonia.Controls;
 using Avalonia.Controls.Diagnostics;
 using Avalonia.Controls.Primitives;
 using Avalonia.Styling;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 using Lifetimes = Avalonia.Controls.ApplicationLifetimes;
 using System.Linq;
 
@@ -61,9 +60,12 @@ namespace Avalonia.Diagnostics.ViewModels
                     IPopupHostProvider popupHostProvider,
                     string? providerName = null)
                 {
-                    return Observable.FromEvent<IPopupHost?>(
-                            x => popupHostProvider.PopupHostChanged += x,
-                            x => popupHostProvider.PopupHostChanged -= x)
+                    return Observable.Create<IPopupHost?>(observer =>
+                        {
+                            void Handler(IPopupHost? args) => observer.OnNext(args);
+                            popupHostProvider.PopupHostChanged += Handler;
+                            return Disposable.Create(() => popupHostProvider.PopupHostChanged -= Handler);
+                        })
                         .StartWith(popupHostProvider.PopupHost)
                         .Select(popupHost =>
                         {
@@ -80,29 +82,39 @@ namespace Avalonia.Diagnostics.ViewModels
                 {
                     Popup p => GetPopupHostObservable(p),
                     Control c => Observable.CombineLatest(
-                            c.GetObservable(Control.ContextFlyoutProperty),
-                            c.GetObservable(Control.ContextMenuProperty),
-                            c.GetObservable(FlyoutBase.AttachedFlyoutProperty),
-                            c.GetObservable(ToolTipDiagnostics.ToolTipProperty),
-                            c.GetObservable(Button.FlyoutProperty),
-                            (ContextFlyout, ContextMenu, AttachedFlyout, ToolTip, ButtonFlyout) =>
+                            new IObservable<IPopupHostProvider?>[]
+                            {
+                                c.GetObservable(Control.ContextFlyoutProperty),
+                                c.GetObservable(Control.ContextMenuProperty),
+                                c.GetObservable(FlyoutBase.AttachedFlyoutProperty),
+                                c.GetObservable(ToolTipDiagnostics.ToolTipProperty),
+                                c.GetObservable(Button.FlyoutProperty)
+                            })
+                        .Select(
+                            items =>
                             {
-                                if (ContextMenu != null)
+                                var contextFlyout = items[0];
+                                var contextMenu = (ContextMenu?)items[1];
+                                var attachedFlyout = items[2];
+                                var toolTip = items[3];
+                                var buttonFlyout = items[4];
+
+                                if (contextMenu != null)
                                     //Note: ContextMenus are special since all the items are added as visual children.
                                     //So we don't need to go via Popup
-                                    return Observable.Return<PopupRoot?>(new PopupRoot(ContextMenu));
+                                    return Observable.Return<PopupRoot?>(new PopupRoot(contextMenu));
 
-                                if (ContextFlyout != null)
-                                    return GetPopupHostObservable(ContextFlyout, "ContextFlyout");
+                                if (contextFlyout != null)
+                                    return GetPopupHostObservable(contextFlyout, "ContextFlyout");
 
-                                if (AttachedFlyout != null)
-                                    return GetPopupHostObservable(AttachedFlyout, "AttachedFlyout");
+                                if (attachedFlyout != null)
+                                    return GetPopupHostObservable(attachedFlyout, "AttachedFlyout");
 
-                                if (ToolTip != null)
-                                    return GetPopupHostObservable(ToolTip, "ToolTip");
+                                if (toolTip != null)
+                                    return GetPopupHostObservable(toolTip, "ToolTip");
 
-                                if (ButtonFlyout != null)
-                                    return GetPopupHostObservable(ButtonFlyout, "Flyout");
+                                if (buttonFlyout != null)
+                                    return GetPopupHostObservable(buttonFlyout, "Flyout");
 
                                 return Observable.Return<PopupRoot?>(null);
                             })
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml.cs
index c81e3cadf4..56d8737d79 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/LayoutExplorerView.axaml.cs
@@ -4,6 +4,7 @@ using Avalonia.Controls.Shapes;
 using Avalonia.Diagnostics.Controls;
 using Avalonia.Markup.Xaml;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.Views
 {
diff --git a/src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs b/src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs
index 13b8cf5e8a..dbc4c98f78 100644
--- a/src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs
+++ b/src/Avalonia.Diagnostics/Diagnostics/Views/MainWindow.xaml.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 using Avalonia.Controls;
 using Avalonia.Controls.Diagnostics;
 using Avalonia.Controls.Primitives;
@@ -13,13 +12,13 @@ using Avalonia.Markup.Xaml;
 using Avalonia.Styling;
 using Avalonia.Themes.Simple;
 using Avalonia.VisualTree;
+using Avalonia.Reactive;
 
 namespace Avalonia.Diagnostics.Views
 {
     internal class MainWindow : Window, IStyleHost
     {
-        private readonly IDisposable? _keySubscription;
-        private readonly IDisposable? _pointerSubscription;
+        private readonly IDisposable? _inputSubscription;
         private readonly Dictionary<Popup, IDisposable> _frozenPopupStates;
         private AvaloniaObject? _root;
         private PixelPoint _lastPointerPosition;
@@ -33,15 +32,19 @@ namespace Avalonia.Diagnostics.Views
             if (Theme is null && this.FindResource(typeof(Window)) is ControlTheme windowTheme)
                 Theme = windowTheme;
 
-            _keySubscription = InputManager.Instance?.Process
-                .OfType<RawKeyEventArgs>()
-                .Where(x => x.Type == RawKeyEventType.KeyDown)
-                .Subscribe(RawKeyDown);
-            _pointerSubscription = InputManager.Instance?.Process
-                .OfType<RawPointerEventArgs>()
-                .Subscribe(x => _lastPointerPosition = ((Visual)x.Root).PointToScreen(x.Position));
-
-
+            _inputSubscription = InputManager.Instance?.Process
+                .Subscribe(x =>
+                {
+                    if (x is RawPointerEventArgs pointerEventArgs)
+                    {
+                        _lastPointerPosition = ((Visual)x.Root).PointToScreen(pointerEventArgs.Position);
+                    }
+                    else if (x is RawKeyEventArgs keyEventArgs && keyEventArgs.Type == RawKeyEventType.KeyDown)
+                    {
+                        RawKeyDown(keyEventArgs);
+                    }
+                });
+            
             _frozenPopupStates = new Dictionary<Popup, IDisposable>();
 
             EventHandler? lh = default;
@@ -94,8 +97,7 @@ namespace Avalonia.Diagnostics.Views
         protected override void OnClosed(EventArgs e)
         {
             base.OnClosed(e);
-            _keySubscription?.Dispose();
-            _pointerSubscription?.Dispose();
+            _inputSubscription?.Dispose();
 
             foreach (var state in _frozenPopupStates)
             {

From e0e82960c22809c1c9ff58620704e5294d84b156 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Wed, 21 Dec 2022 17:09:21 -0500
Subject: [PATCH 072/157] Fix iOS and Android

---
 src/Android/Avalonia.Android/AndroidThreadingInterface.cs | 2 +-
 src/Android/Avalonia.Android/ChoreographerTimer.cs        | 2 +-
 src/Avalonia.Base/Avalonia.Base.csproj                    | 2 ++
 src/iOS/Avalonia.iOS/EaglDisplay.cs                       | 2 +-
 4 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
index de9149e9a1..152076013f 100644
--- a/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
+++ b/src/Android/Avalonia.Android/AndroidThreadingInterface.cs
@@ -1,10 +1,10 @@
 using System;
-using System.Reactive.Disposables;
 using System.Threading;
 
 using Android.OS;
 
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using Avalonia.Threading;
 
 using App = Android.App.Application;
diff --git a/src/Android/Avalonia.Android/ChoreographerTimer.cs b/src/Android/Avalonia.Android/ChoreographerTimer.cs
index 19dc7b4ab6..3545ae8fe1 100644
--- a/src/Android/Avalonia.Android/ChoreographerTimer.cs
+++ b/src/Android/Avalonia.Android/ChoreographerTimer.cs
@@ -1,11 +1,11 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using System.Threading.Tasks;
 
 using Android.OS;
 using Android.Views;
 
+using Avalonia.Reactive;
 using Avalonia.Rendering;
 
 using Java.Lang;
diff --git a/src/Avalonia.Base/Avalonia.Base.csproj b/src/Avalonia.Base/Avalonia.Base.csproj
index e6c13d251f..777a338b8c 100644
--- a/src/Avalonia.Base/Avalonia.Base.csproj
+++ b/src/Avalonia.Base/Avalonia.Base.csproj
@@ -52,6 +52,8 @@
     <InternalsVisibleTo Include="Avalonia.Benchmarks, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.X11, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Win32, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.Android, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="Avalonia.iOS, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Dialogs, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Diagnostics, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7" />
diff --git a/src/iOS/Avalonia.iOS/EaglDisplay.cs b/src/iOS/Avalonia.iOS/EaglDisplay.cs
index 7a5e1a496d..8f7c1f3308 100644
--- a/src/iOS/Avalonia.iOS/EaglDisplay.cs
+++ b/src/iOS/Avalonia.iOS/EaglDisplay.cs
@@ -1,8 +1,8 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive.Disposables;
 using Avalonia.OpenGL;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using OpenGLES;
 
 namespace Avalonia.iOS

From 9f309415c1219228ffb56e5259d17ac8927673a0 Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Fri, 23 Dec 2022 09:26:43 +0100
Subject: [PATCH 073/157] Allow to process non text TextRuns Add TextEndOfLine
 to a TextLine's TextRuns

---
 .../TextCollapsingProperties.cs               |   2 +-
 .../TextFormatting/TextEllipsisHelper.cs      |  23 +--
 .../Media/TextFormatting/TextFormatterImpl.cs |  68 +++++----
 .../Media/TextFormatting/TextLayout.cs        |   7 +-
 .../TextLeadingPrefixCharacterEllipsis.cs     | 133 ++++++++++--------
 .../Media/TextFormatting/TextLineBreak.cs     |   4 +-
 .../Media/TextFormatting/TextLineImpl.cs      | 106 ++++++++++----
 .../Media/TextFormatting/TextRun.cs           |   2 +-
 .../TextTrailingCharacterEllipsis.cs          |   2 +-
 .../TextTrailingWordEllipsis.cs               |   2 +-
 src/Avalonia.Controls/Documents/Run.cs        |   5 +
 .../TextFormatting/MultiBufferTextSource.cs   |   4 +-
 .../TextFormatting/TextFormatterTests.cs      |  63 +++++++++
 .../Media/TextFormatting/TextLineTests.cs     |   4 +-
 14 files changed, 283 insertions(+), 142 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextCollapsingProperties.cs b/src/Avalonia.Base/Media/TextFormatting/TextCollapsingProperties.cs
index f677617b14..01804e1ce3 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextCollapsingProperties.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextCollapsingProperties.cs
@@ -21,6 +21,6 @@ namespace Avalonia.Media.TextFormatting
         /// Collapses given text line.
         /// </summary>
         /// <param name="textLine">Text line to collapse.</param>
-        public abstract List<DrawableTextRun>? Collapse(TextLine textLine);
+        public abstract List<TextRun>? Collapse(TextLine textLine);
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs b/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
index a1b8985b43..574f92568c 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
@@ -5,9 +5,11 @@ namespace Avalonia.Media.TextFormatting
 {
     internal static class TextEllipsisHelper
     {
-        public static List<DrawableTextRun>? Collapse(TextLine textLine, TextCollapsingProperties properties, bool isWordEllipsis)
+        public static List<TextRun>? Collapse(TextLine textLine, TextCollapsingProperties properties, bool isWordEllipsis)
         {
-            if (textLine.TextRuns is not List<DrawableTextRun> textRuns || textRuns.Count == 0)
+            var textRuns = textLine.TextRuns;
+
+            if (textRuns == null || textRuns.Count == 0)
             {
                 return null;
             }
@@ -20,7 +22,7 @@ namespace Avalonia.Media.TextFormatting
             if (properties.Width < shapedSymbol.GlyphRun.Size.Width)
             {
                 //Not enough space to fit in the symbol
-                return new List<DrawableTextRun>(0);
+                return new List<TextRun>(0);
             }
 
             var availableWidth = properties.Width - shapedSymbol.Size.Width;
@@ -70,11 +72,11 @@ namespace Avalonia.Media.TextFormatting
 
                                 collapsedLength += measuredLength;
 
-                                var collapsedRuns = new List<DrawableTextRun>(textRuns.Count);
+                                var collapsedRuns = new List<TextRun>(textRuns.Count);
 
                                 if (collapsedLength > 0)
                                 {
-                                    var splitResult = TextFormatterImpl.SplitDrawableRuns(textRuns, collapsedLength);
+                                    var splitResult = TextFormatterImpl.SplitTextRuns(textRuns, collapsedLength);
 
                                     collapsedRuns.AddRange(splitResult.First);
                                 }
@@ -84,22 +86,21 @@ namespace Avalonia.Media.TextFormatting
                                 return collapsedRuns;
                             }
 
-                            availableWidth -= currentRun.Size.Width;
-
+                            availableWidth -= shapedRun.Size.Width;
 
                             break;
                         }
 
-                    case { } drawableRun:
+                    case DrawableTextRun drawableRun:
                         {
                             //The whole run needs to fit into available space
                             if (currentWidth + drawableRun.Size.Width > availableWidth)
                             {
-                                var collapsedRuns = new List<DrawableTextRun>(textRuns.Count);
+                                var collapsedRuns = new List<TextRun>(textRuns.Count);
 
                                 if (collapsedLength > 0)
                                 {
-                                    var splitResult = TextFormatterImpl.SplitDrawableRuns(textRuns, collapsedLength);
+                                    var splitResult = TextFormatterImpl.SplitTextRuns(textRuns, collapsedLength);
 
                                     collapsedRuns.AddRange(splitResult.First);
                                 }
@@ -109,6 +110,8 @@ namespace Avalonia.Media.TextFormatting
                                 return collapsedRuns;
                             }
 
+                            availableWidth -= drawableRun.Size.Width;
+
                             break;
                         }
                 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
index 93eb4811b9..07aa5e1550 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Linq;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Utilities;
 
@@ -17,20 +16,20 @@ namespace Avalonia.Media.TextFormatting
             var textWrapping = paragraphProperties.TextWrapping;
             FlowDirection resolvedFlowDirection;
             TextLineBreak? nextLineBreak = null;
-            List<DrawableTextRun> drawableTextRuns;
+            IReadOnlyList<TextRun> textRuns;
 
-            var textRuns = FetchTextRuns(textSource, firstTextSourceIndex,
+            var fetchedRuns = FetchTextRuns(textSource, firstTextSourceIndex,
                 out var textEndOfLine, out var textSourceLength);
 
             if (previousLineBreak?.RemainingRuns != null)
             {
                 resolvedFlowDirection = previousLineBreak.FlowDirection;
-                drawableTextRuns = previousLineBreak.RemainingRuns.ToList();
+                textRuns = previousLineBreak.RemainingRuns;
                 nextLineBreak = previousLineBreak;
             }
             else
             {
-                drawableTextRuns = ShapeTextRuns(textRuns, paragraphProperties, out resolvedFlowDirection);
+                textRuns = ShapeTextRuns(fetchedRuns, paragraphProperties, out resolvedFlowDirection);
 
                 if (nextLineBreak == null && textEndOfLine != null)
                 {
@@ -44,7 +43,7 @@ namespace Avalonia.Media.TextFormatting
             {
                 case TextWrapping.NoWrap:
                     {
-                        textLine = new TextLineImpl(drawableTextRuns, firstTextSourceIndex, textSourceLength,
+                        textLine = new TextLineImpl(textRuns, firstTextSourceIndex, textSourceLength,
                             paragraphWidth, paragraphProperties, resolvedFlowDirection, nextLineBreak);
 
                         textLine.FinalizeLine();
@@ -54,7 +53,7 @@ namespace Avalonia.Media.TextFormatting
                 case TextWrapping.WrapWithOverflow:
                 case TextWrapping.Wrap:
                     {
-                        textLine = PerformTextWrapping(drawableTextRuns, firstTextSourceIndex, paragraphWidth, paragraphProperties,
+                        textLine = PerformTextWrapping(textRuns, firstTextSourceIndex, paragraphWidth, paragraphProperties,
                             resolvedFlowDirection, nextLineBreak);
                         break;
                     }
@@ -71,7 +70,7 @@ namespace Avalonia.Media.TextFormatting
         /// <param name="textRuns">The text run's.</param>
         /// <param name="length">The length to split at.</param>
         /// <returns>The split text runs.</returns>
-        internal static SplitResult<List<DrawableTextRun>> SplitDrawableRuns(List<DrawableTextRun> textRuns, int length)
+        internal static SplitResult<IReadOnlyList<TextRun>> SplitTextRuns(IReadOnlyList<TextRun> textRuns, int length)
         {
             var currentLength = 0;
 
@@ -88,7 +87,7 @@ namespace Avalonia.Media.TextFormatting
 
                 var firstCount = currentRun.Length >= 1 ? i + 1 : i;
 
-                var first = new List<DrawableTextRun>(firstCount);
+                var first = new List<TextRun>(firstCount);
 
                 if (firstCount > 1)
                 {
@@ -102,7 +101,7 @@ namespace Avalonia.Media.TextFormatting
 
                 if (currentLength + currentRun.Length == length)
                 {
-                    var second = secondCount > 0 ? new List<DrawableTextRun>(secondCount) : null;
+                    var second = secondCount > 0 ? new List<TextRun>(secondCount) : null;
 
                     if (second != null)
                     {
@@ -116,13 +115,13 @@ namespace Avalonia.Media.TextFormatting
 
                     first.Add(currentRun);
 
-                    return new SplitResult<List<DrawableTextRun>>(first, second);
+                    return new SplitResult<IReadOnlyList<TextRun>>(first, second);
                 }
                 else
                 {
                     secondCount++;
 
-                    var second = new List<DrawableTextRun>(secondCount);
+                    var second = new List<TextRun>(secondCount);
 
                     if (currentRun is ShapedTextCharacters shapedTextCharacters)
                     {
@@ -138,11 +137,11 @@ namespace Avalonia.Media.TextFormatting
                         second.Add(textRuns[i + j]);
                     }
 
-                    return new SplitResult<List<DrawableTextRun>>(first, second);
+                    return new SplitResult<IReadOnlyList<TextRun>>(first, second);
                 }
             }
 
-            return new SplitResult<List<DrawableTextRun>>(textRuns, null);
+            return new SplitResult<IReadOnlyList<TextRun>>(textRuns, null);
         }
 
         /// <summary>
@@ -154,11 +153,11 @@ namespace Avalonia.Media.TextFormatting
         /// <returns>
         /// A list of shaped text characters.
         /// </returns>
-        private static List<DrawableTextRun> ShapeTextRuns(List<TextRun> textRuns, TextParagraphProperties paragraphProperties,
+        private static List<TextRun> ShapeTextRuns(List<TextRun> textRuns, TextParagraphProperties paragraphProperties,
             out FlowDirection resolvedFlowDirection)
         {
             var flowDirection = paragraphProperties.FlowDirection;
-            var drawableTextRuns = new List<DrawableTextRun>();
+            var shapedRuns = new List<TextRun>();
             var biDiData = new BidiData((sbyte)flowDirection);
 
             foreach (var textRun in textRuns)
@@ -199,13 +198,6 @@ namespace Avalonia.Media.TextFormatting
 
                 switch (currentRun)
                 {
-                    case DrawableTextRun drawableRun:
-                        {
-                            drawableTextRuns.Add(drawableRun);
-
-                            break;
-                        }
-
                     case ShapeableTextCharacters shapeableRun:
                         {
                             var groupedRuns = new List<ShapeableTextCharacters>(2) { shapeableRun };
@@ -248,14 +240,20 @@ namespace Avalonia.Media.TextFormatting
                                          shapeableRun.BidiLevel, currentRun.Properties.CultureInfo, 
                                          paragraphProperties.DefaultIncrementalTab, paragraphProperties.LetterSpacing);
 
-                            drawableTextRuns.AddRange(ShapeTogether(groupedRuns, characterBufferReference, length, shaperOptions));
+                            shapedRuns.AddRange(ShapeTogether(groupedRuns, characterBufferReference, length, shaperOptions));
+
+                            break;
+                        }
+                    default:
+                        {
+                            shapedRuns.Add(currentRun);
 
                             break;
                         }
                 }
             }
 
-            return drawableTextRuns;
+            return shapedRuns;
         }
 
         private static IReadOnlyList<ShapedTextCharacters> ShapeTogether(
@@ -390,6 +388,10 @@ namespace Avalonia.Media.TextFormatting
 
                 if (textRun == null)
                 {
+                    textRuns.Add(new TextEndOfParagraph());
+
+                    textSourceLength += TextRun.DefaultTextSourceLength;
+
                     break;
                 }
 
@@ -465,7 +467,7 @@ namespace Avalonia.Media.TextFormatting
             return false;
         }
 
-        private static bool TryMeasureLength(IReadOnlyList<DrawableTextRun> textRuns, double paragraphWidth, out int measuredLength)
+        private static bool TryMeasureLength(IReadOnlyList<TextRun> textRuns, double paragraphWidth, out int measuredLength)
         {
             measuredLength = 0;
             var currentWidth = 0.0;
@@ -502,7 +504,7 @@ namespace Avalonia.Media.TextFormatting
                             break;
                         }
 
-                    case { } drawableTextRun:
+                    case DrawableTextRun drawableTextRun:
                         {
                             if (currentWidth + drawableTextRun.Size.Width >= paragraphWidth)
                             {
@@ -510,7 +512,13 @@ namespace Avalonia.Media.TextFormatting
                             }
 
                             measuredLength += currentRun.Length;
-                            currentWidth += currentRun.Size.Width;
+                            currentWidth += drawableTextRun.Size.Width;
+
+                            break;
+                        }
+                    default:
+                        {
+                            measuredLength += currentRun.Length;
 
                             break;
                         }
@@ -553,7 +561,7 @@ namespace Avalonia.Media.TextFormatting
         /// <param name="resolvedFlowDirection"></param>
         /// <param name="currentLineBreak">The current line break if the line was explicitly broken.</param>
         /// <returns>The wrapped text line.</returns>
-        private static TextLineImpl PerformTextWrapping(List<DrawableTextRun> textRuns, int firstTextSourceIndex,
+        private static TextLineImpl PerformTextWrapping(IReadOnlyList<TextRun> textRuns, int firstTextSourceIndex,
             double paragraphWidth, TextParagraphProperties paragraphProperties, FlowDirection resolvedFlowDirection,
             TextLineBreak? currentLineBreak)
         {
@@ -681,7 +689,7 @@ namespace Avalonia.Media.TextFormatting
                 break;
             }
 
-            var splitResult = SplitDrawableRuns(textRuns, measuredLength);
+            var splitResult = SplitTextRuns(textRuns, measuredLength);
 
             var remainingCharacters = splitResult.Second;
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs b/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
index f803001481..ef0c726793 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
@@ -448,7 +448,7 @@ namespace Avalonia.Media.TextFormatting
                 var textLine = TextFormatter.Current.FormatLine(_textSource, _textSourceLength, MaxWidth,
                     _paragraphProperties, previousLine?.TextLineBreak);
 
-                if (textLine == null || textLine.Length == 0 || textLine.TextRuns.Count == 0 && textLine.TextLineBreak?.TextEndOfLine is TextEndOfParagraph)
+                if(textLine == null || textLine.Length == 0)
                 {
                     if (previousLine != null && previousLine.NewLineLength > 0)
                     {
@@ -501,6 +501,11 @@ namespace Avalonia.Media.TextFormatting
 
                     break;
                 }
+
+                if (textLine.TextLineBreak?.TextEndOfLine is TextEndOfParagraph)
+                {
+                    break;
+                }
             }
 
             //Make sure the TextLayout always contains at least on empty line
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs b/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
index 2752af8f0c..9c085eba17 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
@@ -39,9 +39,11 @@ namespace Avalonia.Media.TextFormatting
         /// <inheritdoc/>
         public override TextRun Symbol { get; }
 
-        public override List<DrawableTextRun>? Collapse(TextLine textLine)
+        public override List<TextRun>? Collapse(TextLine textLine)
         {
-            if (textLine.TextRuns is not List<DrawableTextRun> textRuns || textRuns.Count == 0)
+            var textRuns = textLine.TextRuns;
+
+            if (textRuns == null || textRuns.Count == 0)
             {
                 return null;
             }
@@ -52,7 +54,7 @@ namespace Avalonia.Media.TextFormatting
 
             if (Width < shapedSymbol.GlyphRun.Size.Width)
             {
-                return new List<DrawableTextRun>(0);
+                return new List<TextRun>(0);
             }
 
             // Overview of ellipsis structure
@@ -66,92 +68,101 @@ namespace Avalonia.Media.TextFormatting
                 switch (currentRun)
                 {
                     case ShapedTextCharacters shapedRun:
-                    {
-                        currentWidth += currentRun.Size.Width;
-
-                        if (currentWidth > availableWidth)
                         {
-                            shapedRun.TryMeasureCharacters(availableWidth, out var measuredLength);
-
-                            var collapsedRuns = new List<DrawableTextRun>(textRuns.Count);
+                            currentWidth += shapedRun.Size.Width;
 
-                            if (measuredLength > 0)
+                            if (currentWidth > availableWidth)
                             {
-                                List<DrawableTextRun>? preSplitRuns = null;
-                                List<DrawableTextRun>? postSplitRuns;
-
-                                if (_prefixLength > 0)
-                                {
-                                    var splitResult = TextFormatterImpl.SplitDrawableRuns(textRuns,
-                                        Math.Min(_prefixLength, measuredLength));
+                                shapedRun.TryMeasureCharacters(availableWidth, out var measuredLength);
 
-                                    collapsedRuns.AddRange(splitResult.First);
+                                var collapsedRuns = new List<TextRun>(textRuns.Count);
 
-                                    preSplitRuns = splitResult.First;
-                                    postSplitRuns = splitResult.Second;
-                                }
-                                else
+                                if (measuredLength > 0)
                                 {
-                                    postSplitRuns = textRuns;
-                                }
+                                    IReadOnlyList<TextRun>? preSplitRuns = null;
+                                    IReadOnlyList<TextRun>? postSplitRuns;
 
-                                collapsedRuns.Add(shapedSymbol);
+                                    if (_prefixLength > 0)
+                                    {
+                                        var splitResult = TextFormatterImpl.SplitTextRuns(textRuns,
+                                            Math.Min(_prefixLength, measuredLength));
 
-                                if (measuredLength <= _prefixLength || postSplitRuns is null)
-                                {
-                                    return collapsedRuns;
-                                }
+                                        collapsedRuns.AddRange(splitResult.First);
 
-                                var availableSuffixWidth = availableWidth;
+                                        preSplitRuns = splitResult.First;
+                                        postSplitRuns = splitResult.Second;
+                                    }
+                                    else
+                                    {
+                                        postSplitRuns = textRuns;
+                                    }
 
-                                if (preSplitRuns is not null)
-                                {
-                                    foreach (var run in preSplitRuns)
+                                    collapsedRuns.Add(shapedSymbol);
+
+                                    if (measuredLength <= _prefixLength || postSplitRuns is null)
                                     {
-                                        availableSuffixWidth -= run.Size.Width;
+                                        return collapsedRuns;
                                     }
-                                }
 
-                                for (var i = postSplitRuns.Count - 1; i >= 0; i--)
-                                {
-                                    var run = postSplitRuns[i];
+                                    var availableSuffixWidth = availableWidth;
 
-                                    switch (run)
+                                    if (preSplitRuns is not null)
                                     {
-                                        case ShapedTextCharacters endShapedRun:
+                                        foreach (var run in preSplitRuns)
                                         {
-                                            if (endShapedRun.TryMeasureCharactersBackwards(availableSuffixWidth,
-                                                    out var suffixCount, out var suffixWidth))
+                                            if (run is DrawableTextRun drawableTextRun)
                                             {
-                                                availableSuffixWidth -= suffixWidth;
+                                                availableSuffixWidth -= drawableTextRun.Size.Width;
+                                            }
+                                        }
+                                    }
 
-                                                if (suffixCount > 0)
+                                    for (var i = postSplitRuns.Count - 1; i >= 0; i--)
+                                    {
+                                        var run = postSplitRuns[i];
+
+                                        switch (run)
+                                        {
+                                            case ShapedTextCharacters endShapedRun:
                                                 {
-                                                    var splitSuffix =
-                                                        endShapedRun.Split(run.Length - suffixCount);
+                                                    if (endShapedRun.TryMeasureCharactersBackwards(availableSuffixWidth,
+                                                            out var suffixCount, out var suffixWidth))
+                                                    {
+                                                        availableSuffixWidth -= suffixWidth;
 
-                                                    collapsedRuns.Add(splitSuffix.Second!);
-                                                }
-                                            }
+                                                        if (suffixCount > 0)
+                                                        {
+                                                            var splitSuffix =
+                                                                endShapedRun.Split(run.Length - suffixCount);
+
+                                                            collapsedRuns.Add(splitSuffix.Second!);
+                                                        }
+                                                    }
 
-                                            break;
+                                                    break;
+                                                }
                                         }
                                     }
                                 }
-                            }
-                            else
-                            {
-                                collapsedRuns.Add(shapedSymbol);
+                                else
+                                {
+                                    collapsedRuns.Add(shapedSymbol);
+                                }
+
+                                return collapsedRuns;
                             }
 
-                            return collapsedRuns;
-                        }
+                            availableWidth -= shapedRun.Size.Width;
 
-                        break;
-                    }
-                }
+                            break;
+                        }
+                    case DrawableTextRun drawableTextRun:
+                        {
+                            availableWidth -= drawableTextRun.Size.Width;
 
-                availableWidth -= currentRun.Size.Width;
+                            break;
+                        }
+                }            
 
                 runIndex++;
             }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineBreak.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineBreak.cs
index ce35e47fbd..bf26ac5df4 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineBreak.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineBreak.cs
@@ -5,7 +5,7 @@ namespace Avalonia.Media.TextFormatting
     public class TextLineBreak
     {
         public TextLineBreak(TextEndOfLine? textEndOfLine = null, FlowDirection flowDirection = FlowDirection.LeftToRight, 
-            IReadOnlyList<DrawableTextRun>? remainingRuns = null)
+            IReadOnlyList<TextRun>? remainingRuns = null)
         {
             TextEndOfLine = textEndOfLine;
             FlowDirection = flowDirection;
@@ -25,6 +25,6 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Get the remaining runs that were split up by the <see cref="TextFormatter"/> during the formatting process.
         /// </summary>
-        public IReadOnlyList<DrawableTextRun>? RemainingRuns { get; }
+        public IReadOnlyList<TextRun>? RemainingRuns { get; }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index 3241dfd12b..48f5fec2c0 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -6,13 +6,13 @@ namespace Avalonia.Media.TextFormatting
 {
     internal class TextLineImpl : TextLine
     {
-        private readonly List<DrawableTextRun> _textRuns;
+        private IReadOnlyList<TextRun> _textRuns;
         private readonly double _paragraphWidth;
         private readonly TextParagraphProperties _paragraphProperties;
         private TextLineMetrics _textLineMetrics;
         private readonly FlowDirection _resolvedFlowDirection;
 
-        public TextLineImpl(List<DrawableTextRun> textRuns, int firstTextSourceIndex, int length, double paragraphWidth,
+        public TextLineImpl(IReadOnlyList<TextRun> textRuns, int firstTextSourceIndex, int length, double paragraphWidth,
             TextParagraphProperties paragraphProperties, FlowDirection resolvedFlowDirection = FlowDirection.LeftToRight,
             TextLineBreak? lineBreak = null, bool hasCollapsed = false)
         {
@@ -86,11 +86,14 @@ namespace Avalonia.Media.TextFormatting
 
             foreach (var textRun in _textRuns)
             {
-                var offsetY = GetBaselineOffset(this, textRun);
+                if (textRun is DrawableTextRun drawable)
+                {
+                    var offsetY = GetBaselineOffset(this, drawable);
 
-                textRun.Draw(drawingContext, new Point(currentX, currentY + offsetY));
+                    drawable.Draw(drawingContext, new Point(currentX, currentY + offsetY));
 
-                currentX += textRun.Size.Width;
+                    currentX += drawable.Size.Width;
+                }
             }
         }
 
@@ -180,7 +183,14 @@ namespace Avalonia.Media.TextFormatting
             {
                 var lastRun = _textRuns[_textRuns.Count - 1];
 
-                return GetRunCharacterHit(lastRun, FirstTextSourceIndex + Length - lastRun.Length, lastRun.Size.Width);
+                var size = 0.0;
+
+                if (lastRun is DrawableTextRun drawableTextRun)
+                {
+                    size = drawableTextRun.Size.Width;
+                }
+
+                return GetRunCharacterHit(lastRun, FirstTextSourceIndex + Length - lastRun.Length, size);
             }
 
             // process hit that happens within the line
@@ -220,9 +230,16 @@ namespace Avalonia.Media.TextFormatting
 
                         currentRun = _textRuns[j];
 
-                        if (currentDistance + currentRun.Size.Width <= distance)
+                        if(currentRun is not ShapedTextCharacters)
+                        {
+                            continue;
+                        }
+
+                        shapedRun = (ShapedTextCharacters)currentRun;
+
+                        if (currentDistance + shapedRun.Size.Width <= distance)
                         {
-                            currentDistance += currentRun.Size.Width;
+                            currentDistance += shapedRun.Size.Width;
                             currentPosition -= currentRun.Length;
 
                             continue;
@@ -234,12 +251,19 @@ namespace Avalonia.Media.TextFormatting
 
                 characterHit = GetRunCharacterHit(currentRun, currentPosition, distance - currentDistance);
 
-                if (i < _textRuns.Count - 1 && currentDistance + currentRun.Size.Width < distance)
+                if (currentRun is DrawableTextRun drawableTextRun)
                 {
-                    currentDistance += currentRun.Size.Width;
+                    if (i < _textRuns.Count - 1 && currentDistance + drawableTextRun.Size.Width < distance)
+                    {
+                        currentDistance += drawableTextRun.Size.Width;
 
-                    currentPosition += currentRun.Length;
+                        currentPosition += currentRun.Length;
 
+                        continue;
+                    }
+                }
+                else
+                {
                     continue;
                 }
 
@@ -249,7 +273,7 @@ namespace Avalonia.Media.TextFormatting
             return characterHit;
         }
 
-        private static CharacterHit GetRunCharacterHit(DrawableTextRun run, int currentPosition, double distance)
+        private static CharacterHit GetRunCharacterHit(TextRun run, int currentPosition, double distance)
         {
             CharacterHit characterHit;
 
@@ -270,9 +294,9 @@ namespace Avalonia.Media.TextFormatting
 
                         break;
                     }
-                default:
+                case DrawableTextRun drawableTextRun:
                     {
-                        if (distance < run.Size.Width / 2)
+                        if (distance < drawableTextRun.Size.Width / 2)
                         {
                             characterHit = new CharacterHit(currentPosition);
                         }
@@ -282,6 +306,10 @@ namespace Avalonia.Media.TextFormatting
                         }
                         break;
                     }
+                default:
+                    characterHit = new CharacterHit(currentPosition, run.Length);
+
+                    break;
             }
 
             return characterHit;
@@ -307,7 +335,7 @@ namespace Avalonia.Media.TextFormatting
                     {
                         var i = index;
 
-                        var rightToLeftWidth = currentRun.Size.Width;
+                        var rightToLeftWidth = shapedRun.Size.Width;
 
                         while (i + 1 <= _textRuns.Count - 1)
                         {
@@ -317,7 +345,7 @@ namespace Avalonia.Media.TextFormatting
                             {
                                 i++;
 
-                                rightToLeftWidth += nextRun.Size.Width;
+                                rightToLeftWidth += nextShapedRun.Size.Width;
 
                                 continue;
                             }
@@ -331,7 +359,10 @@ namespace Avalonia.Media.TextFormatting
                             {
                                 currentRun = _textRuns[i];
 
-                                rightToLeftWidth -= currentRun.Size.Width;
+                                if (currentRun is DrawableTextRun drawable)
+                                {
+                                    rightToLeftWidth -= drawable.Size.Width;
+                                }
 
                                 if (currentPosition + currentRun.Length >= characterIndex)
                                 {
@@ -355,8 +386,13 @@ namespace Avalonia.Media.TextFormatting
                         return Math.Max(0, currentDistance + distance);
                     }
 
+                    if (currentRun is DrawableTextRun drawableTextRun)
+                    {
+                        currentDistance += drawableTextRun.Size.Width;
+                    }
+
                     //No hit hit found so we add the full width
-                    currentDistance += currentRun.Size.Width;
+
                     currentPosition += currentRun.Length;
                     remainingLength -= currentRun.Length;
                 }
@@ -380,8 +416,12 @@ namespace Avalonia.Media.TextFormatting
                         return Math.Max(0, currentDistance - distance);
                     }
 
+                    if (currentRun is DrawableTextRun drawableTextRun)
+                    {
+                        currentDistance -= drawableTextRun.Size.Width;
+                    }
+
                     //No hit hit found so we add the full width
-                    currentDistance -= currentRun.Size.Width;
                     currentPosition += currentRun.Length;
                     remainingLength -= currentRun.Length;
                 }
@@ -391,7 +431,7 @@ namespace Avalonia.Media.TextFormatting
         }
 
         private static bool TryGetDistanceFromCharacterHit(
-            DrawableTextRun currentRun,
+            TextRun currentRun,
             CharacterHit characterHit,
             int currentPosition,
             int remainingLength,
@@ -432,7 +472,7 @@ namespace Avalonia.Media.TextFormatting
 
                         break;
                     }
-                default:
+                case DrawableTextRun drawableTextRun:
                     {
                         if (characterIndex == currentPosition)
                         {
@@ -441,7 +481,7 @@ namespace Avalonia.Media.TextFormatting
 
                         if (characterIndex == currentPosition + currentRun.Length)
                         {
-                            distance = currentRun.Size.Width;
+                            distance = drawableTextRun.Size.Width;
 
                             return true;
 
@@ -449,6 +489,10 @@ namespace Avalonia.Media.TextFormatting
 
                         break;
                     }
+                default:
+                    {
+                        return false;
+                    }
             }
 
             return false;
@@ -943,7 +987,7 @@ namespace Avalonia.Media.TextFormatting
             return this;
         }
 
-        private static sbyte GetRunBidiLevel(DrawableTextRun run, FlowDirection flowDirection)
+        private static sbyte GetRunBidiLevel(TextRun run, FlowDirection flowDirection)
         {
             if (run is ShapedTextCharacters shapedTextCharacters)
             {
@@ -1039,16 +1083,18 @@ namespace Avalonia.Media.TextFormatting
                 minLevelToReverse--;
             }
 
-            _textRuns.Clear();
+            var textRuns = new List<TextRun>(_textRuns.Count);
 
             current = orderedRun;
 
             while (current != null)
             {
-                _textRuns.Add(current.Run);
+                textRuns.Add(current.Run);
 
                 current = current.Next;
             }
+
+            _textRuns = textRuns;
         }
 
         /// <summary>
@@ -1286,7 +1332,7 @@ namespace Avalonia.Media.TextFormatting
         {
             var runIndex = 0;
             textPosition = FirstTextSourceIndex;
-            DrawableTextRun? previousRun = null;
+            TextRun? previousRun = null;
 
             while (runIndex < _textRuns.Count)
             {
@@ -1346,7 +1392,6 @@ namespace Avalonia.Media.TextFormatting
 
                             break;
                         }
-
                     default:
                         {
                             if (codepointIndex == textPosition)
@@ -1363,6 +1408,7 @@ namespace Avalonia.Media.TextFormatting
 
                             break;
                         }
+
                 }
 
                 runIndex++;
@@ -1436,7 +1482,7 @@ namespace Avalonia.Media.TextFormatting
                             break;
                         }
 
-                    case { } drawableTextRun:
+                    case DrawableTextRun drawableTextRun:
                         {
                             widthIncludingWhitespace += drawableTextRun.Size.Width;
 
@@ -1558,7 +1604,7 @@ namespace Avalonia.Media.TextFormatting
 
         private sealed class OrderedBidiRun
         {
-            public OrderedBidiRun(DrawableTextRun run, sbyte level)
+            public OrderedBidiRun(TextRun run, sbyte level)
             {
                 Run = run;
                 Level = level;
@@ -1566,7 +1612,7 @@ namespace Avalonia.Media.TextFormatting
 
             public sbyte Level { get; }
 
-            public DrawableTextRun Run { get; }
+            public TextRun Run { get; }
 
             public OrderedBidiRun? Next { get; set; }
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
index 0306054767..b55a0d627b 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
@@ -40,7 +40,7 @@ namespace Avalonia.Media.TextFormatting
                 {
                     unsafe
                     {
-                        var characterBuffer = _textRun.CharacterBufferReference.CharacterBuffer;
+                        var characterBuffer = new CharacterBufferRange(_textRun.CharacterBufferReference, _textRun.Length);
 
                         fixed (char* charsPtr = characterBuffer.Span)
                         {
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextTrailingCharacterEllipsis.cs b/src/Avalonia.Base/Media/TextFormatting/TextTrailingCharacterEllipsis.cs
index 1de04ad061..deecbbe476 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextTrailingCharacterEllipsis.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextTrailingCharacterEllipsis.cs
@@ -26,7 +26,7 @@ namespace Avalonia.Media.TextFormatting
         /// <inheritdoc/>
         public override TextRun Symbol { get; }
 
-        public override List<DrawableTextRun>? Collapse(TextLine textLine)
+        public override List<TextRun>? Collapse(TextLine textLine)
         {
             return TextEllipsisHelper.Collapse(textLine, this, false);
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextTrailingWordEllipsis.cs b/src/Avalonia.Base/Media/TextFormatting/TextTrailingWordEllipsis.cs
index 7c94715aa4..c291e1dfb9 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextTrailingWordEllipsis.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextTrailingWordEllipsis.cs
@@ -31,7 +31,7 @@ namespace Avalonia.Media.TextFormatting
         /// <inheritdoc/>
         public override TextRun Symbol { get; }
 
-        public override List<DrawableTextRun>? Collapse(TextLine textLine)
+        public override List<TextRun>? Collapse(TextLine textLine)
         {
             return TextEllipsisHelper.Collapse(textLine, this, true);
         }
diff --git a/src/Avalonia.Controls/Documents/Run.cs b/src/Avalonia.Controls/Documents/Run.cs
index 5d7b8998e6..f64cf79127 100644
--- a/src/Avalonia.Controls/Documents/Run.cs
+++ b/src/Avalonia.Controls/Documents/Run.cs
@@ -54,6 +54,11 @@ namespace Avalonia.Controls.Documents
         {
             var text = Text ?? "";
 
+            if (string.IsNullOrEmpty(text))
+            {
+                return;
+            }
+
             var textRunProperties = CreateTextRunProperties();           
 
             var textCharacters = new TextCharacters(text, textRunProperties);
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/MultiBufferTextSource.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/MultiBufferTextSource.cs
index aa499bb135..81d7b1854b 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/MultiBufferTextSource.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/MultiBufferTextSource.cs
@@ -1,6 +1,4 @@
-using System;
-using Avalonia.Media.TextFormatting;
-using Avalonia.Utilities;
+using Avalonia.Media.TextFormatting;
 
 namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 {
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
index 33d4fba5f1..643bf513d9 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
@@ -62,6 +62,69 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+        private class TextSourceWithDummyRuns : ITextSource
+        {
+            private readonly TextRunProperties _properties;
+            private readonly List<ValueSpan<TextRun>> _textRuns;
+
+            public TextSourceWithDummyRuns(TextRunProperties properties)
+            {
+                _properties = properties;
+
+                _textRuns = new List<ValueSpan<TextRun>>
+                {
+                    new ValueSpan<TextRun>(0, 5, new TextCharacters("Hello", _properties)),
+                    new ValueSpan<TextRun>(5, 1, new DummyRun()),
+                    new ValueSpan<TextRun>(6, 1, new DummyRun()),
+                    new ValueSpan<TextRun>(7, 6, new TextCharacters(" World", _properties))
+                };
+            }
+
+            public TextRun GetTextRun(int textSourceIndex)
+            {
+                foreach (var run in _textRuns)
+                {
+                    if (textSourceIndex < run.Start + run.Length)
+                    {
+                        return run.Value;
+                    }
+                }
+
+                return new TextEndOfParagraph();
+            }
+
+            private class DummyRun : TextRun
+            {
+                public DummyRun()
+                {
+                    Length = DefaultTextSourceLength;
+                }
+
+                public override int Length { get; }
+            }
+        }
+
+        [Fact]
+        public void Should_Format_TextLine_With_Non_Text_TextRuns()
+        {
+            using (Start())
+            {
+                var defaultProperties =
+                    new GenericTextRunProperties(Typeface.Default, 12, foregroundBrush: Brushes.Black);
+
+                var textSource = new TextSourceWithDummyRuns(defaultProperties);
+
+                var formatter = new TextFormatterImpl();
+
+                var textLine = formatter.FormatLine(textSource, 0, double.PositiveInfinity,
+                    new GenericTextParagraphProperties(defaultProperties));
+
+                Assert.Equal(5, textLine.TextRuns.Count);
+
+                Assert.Equal(14, textLine.Length);
+            }
+        }
+
         [Fact]
         public void Should_Format_TextRuns_With_TextRunStyles()
         {
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
index d6257a0de8..f8e287d0a7 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
@@ -326,7 +326,9 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                     }
                 }
 
-                Assert.Equal(currentDistance, textLine.GetDistanceFromCharacterHit(new CharacterHit(s_multiLineText.Length)));
+                var actualDistance = textLine.GetDistanceFromCharacterHit(new CharacterHit(s_multiLineText.Length));
+
+                Assert.Equal(currentDistance, actualDistance);
             }
         }
 

From 05d8b84ce3e4f30c6c5c643ce6cbf841c24121d5 Mon Sep 17 00:00:00 2001
From: rabbitism <popmessiah@hotmail.com>
Date: Tue, 3 Jan 2023 23:21:53 +0800
Subject: [PATCH 074/157] feat: Add GeometryConverter

---
 src/Avalonia.Base/Media/Geometry.cs | 33 ++++++++++++++++++++++++++++-
 1 file changed, 32 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Media/Geometry.cs b/src/Avalonia.Base/Media/Geometry.cs
index 2019f54c70..b1fea53289 100644
--- a/src/Avalonia.Base/Media/Geometry.cs
+++ b/src/Avalonia.Base/Media/Geometry.cs
@@ -1,11 +1,14 @@
 using System;
 using Avalonia.Platform;
+using System.ComponentModel;
+using System.Globalization;
 
 namespace Avalonia.Media
 {
     /// <summary>
     /// Defines a geometric shape.
-    /// </summary>    
+    /// </summary>
+    [TypeConverter(typeof(GeometryConverter))]
     public abstract class Geometry : AvaloniaObject
     {
         /// <summary>
@@ -199,4 +202,32 @@ namespace Avalonia.Media
             return new CombinedGeometry(combineMode, geometry1, geometry2, transform);
         }
     }
+
+    public class GeometryConverter : TypeConverter
+    {
+        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
+        {
+            if (sourceType == typeof(string))
+            {
+                return true;
+            }
+            return base.CanConvertFrom(context, sourceType);
+        }
+
+        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
+        {
+            if (value is null)
+            {
+                throw GetConvertFromException(value);
+            }
+            string source = value as string;
+
+            if (source != null)
+            {
+                return Geometry.Parse(source);
+            }
+
+            return base.ConvertFrom(context, culture, value);
+        }
+    }
 }

From 6e1311c75d16547920b05812fcffa225da2d2893 Mon Sep 17 00:00:00 2001
From: rabbitism <popmessiah@hotmail.com>
Date: Wed, 4 Jan 2023 00:09:51 +0800
Subject: [PATCH 075/157] fix: fix nullable issue.

---
 src/Avalonia.Base/Media/Geometry.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Base/Media/Geometry.cs b/src/Avalonia.Base/Media/Geometry.cs
index b1fea53289..e2b345df1a 100644
--- a/src/Avalonia.Base/Media/Geometry.cs
+++ b/src/Avalonia.Base/Media/Geometry.cs
@@ -214,13 +214,13 @@ namespace Avalonia.Media
             return base.CanConvertFrom(context, sourceType);
         }
 
-        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
+        public override object? ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
         {
             if (value is null)
             {
                 throw GetConvertFromException(value);
             }
-            string source = value as string;
+            string? source = value as string;
 
             if (source != null)
             {

From 876fa088124941aeb60e81f00bdb2bf3a26b882a Mon Sep 17 00:00:00 2001
From: Simon <simon.cropp@gmail.com>
Date: Wed, 4 Jan 2023 10:18:35 +1100
Subject: [PATCH 076/157] move to a consistent langversion of 11

---
 Directory.Build.props                                            | 1 +
 build/SharedVersion.props                                        | 1 -
 src/Browser/Avalonia.Browser/Avalonia.Browser.csproj             | 1 -
 src/tools/DevAnalyzers/DevAnalyzers.csproj                       | 1 -
 src/tools/DevGenerators/DevGenerators.csproj                     | 1 -
 tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj     | 1 -
 .../Avalonia.Controls.DataGrid.UnitTests.csproj                  | 1 -
 .../Avalonia.Controls.UnitTests.csproj                           | 1 -
 .../Avalonia.Markup.Xaml.UnitTests.csproj                        | 1 -
 tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj     | 1 -
 tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj               | 1 -
 11 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/Directory.Build.props b/Directory.Build.props
index 42daa2df7f..c19a55e8ea 100644
--- a/Directory.Build.props
+++ b/Directory.Build.props
@@ -7,5 +7,6 @@
       <AddSyntheticProjectReferencesForSolutionDependencies>false</AddSyntheticProjectReferencesForSolutionDependencies>
       <MSBuildEnableWorkloadResolver>false</MSBuildEnableWorkloadResolver>
       <RunApiCompat>False</RunApiCompat>
+      <LangVersion>11</LangVersion>
   </PropertyGroup>
 </Project>
diff --git a/build/SharedVersion.props b/build/SharedVersion.props
index e9c3d65b41..eca3ba37b0 100644
--- a/build/SharedVersion.props
+++ b/build/SharedVersion.props
@@ -8,7 +8,6 @@
     <RepositoryUrl>https://github.com/AvaloniaUI/Avalonia/</RepositoryUrl>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <NoWarn>$(NoWarn);CS1591</NoWarn>
-    <LangVersion>preview</LangVersion>
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <PackageIcon>Icon.png</PackageIcon>
     <PackageDescription>Avalonia is a cross-platform UI framework for .NET providing a flexible styling system and supporting a wide range of Operating Systems such as Windows, Linux, macOS and with experimental support for Android, iOS and WebAssembly.</PackageDescription>
diff --git a/src/Browser/Avalonia.Browser/Avalonia.Browser.csproj b/src/Browser/Avalonia.Browser/Avalonia.Browser.csproj
index 014d387cb2..2fc3cc885a 100644
--- a/src/Browser/Avalonia.Browser/Avalonia.Browser.csproj
+++ b/src/Browser/Avalonia.Browser/Avalonia.Browser.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>net7.0</TargetFramework>
-    <LangVersion>preview</LangVersion>
     <Nullable>enable</Nullable>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
   </PropertyGroup>
diff --git a/src/tools/DevAnalyzers/DevAnalyzers.csproj b/src/tools/DevAnalyzers/DevAnalyzers.csproj
index 53e3e74e76..e5c2fc6cf6 100644
--- a/src/tools/DevAnalyzers/DevAnalyzers.csproj
+++ b/src/tools/DevAnalyzers/DevAnalyzers.csproj
@@ -2,7 +2,6 @@
 
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
-    <LangVersion>10</LangVersion>
     <Nullable>enable</Nullable>
   </PropertyGroup>
 
diff --git a/src/tools/DevGenerators/DevGenerators.csproj b/src/tools/DevGenerators/DevGenerators.csproj
index 069ff159fc..30da940514 100644
--- a/src/tools/DevGenerators/DevGenerators.csproj
+++ b/src/tools/DevGenerators/DevGenerators.csproj
@@ -4,7 +4,6 @@
     <TargetFramework>netstandard2.0</TargetFramework>
     <Nullable>enable</Nullable>
     <IsPackable>false</IsPackable>
-    <LangVersion>10</LangVersion>
   </PropertyGroup>
 
   <ItemGroup>
diff --git a/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj b/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
index 0162f53f5e..4cdce8df26 100644
--- a/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
+++ b/tests/Avalonia.Base.UnitTests/Avalonia.Base.UnitTests.csproj
@@ -3,7 +3,6 @@
     <TargetFramework>net6.0</TargetFramework>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
-    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\UnitTests.NetFX.props" />
diff --git a/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj b/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
index eb1bf24d0c..20c2f711ad 100644
--- a/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
+++ b/tests/Avalonia.Controls.DataGrid.UnitTests/Avalonia.Controls.DataGrid.UnitTests.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
-    <LangVersion>latest</LangVersion>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj b/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
index 12eb290fde..471f19f948 100644
--- a/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
+++ b/tests/Avalonia.Controls.UnitTests/Avalonia.Controls.UnitTests.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
-    <LangVersion>latest</LangVersion>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
   </PropertyGroup>
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj b/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
index 6dce5eaab5..fa4957c24c 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Avalonia.Markup.Xaml.UnitTests.csproj
@@ -3,7 +3,6 @@
     <TargetFrameworks>net6.0;net47</TargetFrameworks>
     <OutputType>Library</OutputType>
     <IsTestProject>true</IsTestProject>
-    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\UnitTests.NetFX.props" />
diff --git a/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj b/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
index ccde66a50e..ea91b8c196 100644
--- a/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
+++ b/tests/Avalonia.Skia.UnitTests/Avalonia.Skia.UnitTests.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk" ToolsVersion="15.0">
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
-    <LangVersion>latest</LangVersion>
   </PropertyGroup>
   <Import Project="..\..\build\UnitTests.NetCore.targets" />
   <Import Project="..\..\build\Moq.props" />
diff --git a/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj b/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
index cb6884cad8..b9c2a619d9 100644
--- a/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
+++ b/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
@@ -1,7 +1,6 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>netstandard2.0</TargetFrameworks>
-    <LangVersion>latest</LangVersion>
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <OutputType>Library</OutputType>
     <IsPackable>false</IsPackable>

From e049313e7a563b3ab65ad679980309aca34af14a Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Thu, 5 Jan 2023 20:50:34 +1100
Subject: [PATCH 077/157] Microsoft.Build.Traversal 3.2.0

---
 global.json | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/global.json b/global.json
index e4a0cc20c2..8536535b51 100644
--- a/global.json
+++ b/global.json
@@ -4,6 +4,6 @@
         "rollForward": "latestFeature"
     },
     "msbuild-sdks": {
-        "Microsoft.Build.Traversal": "1.0.43"
+        "Microsoft.Build.Traversal": "3.2.0"
     }
 }

From dba476c11c0f3c92be8b3356c6a02ea393c52cc2 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Thu, 5 Jan 2023 22:19:57 +1100
Subject: [PATCH 078/157] fix more typos

---
 samples/ControlCatalog/Models/StateData.cs           |  6 +++---
 src/Avalonia.FreeDesktop/DBusMenuExporter.cs         |  4 ++--
 .../AvaloniaXamlIlSelectorTransformer.cs             |  6 +++---
 .../AvaloniaObjectTests_SetValue.cs                  |  8 ++++----
 .../Core/ExpressionObserverTests_DataValidation.cs   |  2 +-
 .../Core/ExpressionObserverTests_ExpressionTree.cs   |  2 +-
 tests/Avalonia.Base.UnitTests/Input/GesturesTests.cs |  2 +-
 tests/Avalonia.Base.UnitTests/VisualTests.cs         |  4 ++--
 tests/Avalonia.Controls.UnitTests/WindowTests.cs     | 12 ++++++------
 .../Xaml/BasicTests.cs                               |  4 ++--
 .../Xaml/ControlTemplateTests.cs                     |  6 +++---
 .../Xaml/StyleTests.cs                               |  4 ++--
 .../Avalonia.RenderTests/Controls/TextBlockTests.cs  |  4 ++--
 .../Media/TextFormatting/TextLayoutTests.cs          |  2 +-
 tests/Avalonia.RenderTests/OpacityMaskTests.cs       |  2 +-
 15 files changed, 34 insertions(+), 34 deletions(-)

diff --git a/samples/ControlCatalog/Models/StateData.cs b/samples/ControlCatalog/Models/StateData.cs
index bd6d186252..a7ea655cd2 100644
--- a/samples/ControlCatalog/Models/StateData.cs
+++ b/samples/ControlCatalog/Models/StateData.cs
@@ -6,10 +6,10 @@ public class StateData
     public string Abbreviation { get; private set; }
     public string Capital { get; private set; }
 
-    public StateData(string name, string abbreviatoin, string capital)
+    public StateData(string name, string abbreviation, string capital)
     {
         Name = name;
-        Abbreviation = abbreviatoin;
+        Abbreviation = abbreviation;
         Capital = capital;
     }
 
@@ -17,4 +17,4 @@ public class StateData
     {
         return Name;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Avalonia.FreeDesktop/DBusMenuExporter.cs b/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
index 657e324010..4466b938cf 100644
--- a/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
+++ b/src/Avalonia.FreeDesktop/DBusMenuExporter.cs
@@ -25,9 +25,9 @@ namespace Avalonia.FreeDesktop
             return new DBusMenuExporterImpl(DBusHelper.Connection, xid);
         }
         
-        public static INativeMenuExporter TryCreateDetachedNativeMenu(ObjectPath path, Connection currentConection)
+        public static INativeMenuExporter TryCreateDetachedNativeMenu(ObjectPath path, Connection currentConnection)
         {
-            return new DBusMenuExporterImpl(currentConection, path);
+            return new DBusMenuExporterImpl(currentConnection, path);
         }
 
         public static ObjectPath GenerateDBusMenuObjPath => "/net/avaloniaui/dbusmenu/"
diff --git a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
index ba0da4fbe0..078e23bc02 100644
--- a/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
+++ b/src/Markup/Avalonia.Markup.Xaml.Loader/CompilerExtensions/Transformers/AvaloniaXamlIlSelectorTransformer.cs
@@ -124,7 +124,7 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
                                             $"Cannot convert '{attachedProperty.Value}' to '{targetPropertyType.GetFqn()}",
                                             node);
 
-                                result = new XamlIlAttacchedPropertyEqualsSelector(result, targetPropertyField, typedValue);
+                                result = new XamlIlAttachedPropertyEqualsSelector(result, targetPropertyField, typedValue);
                                 break;
                             }
                         case SelectorGrammar.ChildSyntax child:
@@ -414,9 +414,9 @@ namespace Avalonia.Markup.Xaml.XamlIl.CompilerExtensions.Transformers
     }
 
 
-    class XamlIlAttacchedPropertyEqualsSelector : XamlIlSelectorNode
+    class XamlIlAttachedPropertyEqualsSelector : XamlIlSelectorNode
     {
-        public XamlIlAttacchedPropertyEqualsSelector(XamlIlSelectorNode previous,
+        public XamlIlAttachedPropertyEqualsSelector(XamlIlSelectorNode previous,
             IXamlField propertyFiled,
             IXamlAstValueNode value)
             : base(previous)
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_SetValue.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_SetValue.cs
index f878977cf2..99c4ac3d86 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_SetValue.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_SetValue.cs
@@ -227,7 +227,7 @@ namespace Avalonia.Base.UnitTests
         {
             Class2 target = new Class2();
 
-            target.SetValue((AvaloniaProperty)Class2.FlobProperty, new ImplictDouble(4));
+            target.SetValue((AvaloniaProperty)Class2.FlobProperty, new ImplicitDouble(4));
 
             var value = target.GetValue(Class2.FlobProperty);
             Assert.IsType<double>(value);
@@ -393,16 +393,16 @@ namespace Avalonia.Base.UnitTests
                 AvaloniaProperty.RegisterAttached<AttachedOwner, Class2, string>("Attached");
         }
 
-        private class ImplictDouble
+        private class ImplicitDouble
         {
-            public ImplictDouble(double value)
+            public ImplicitDouble(double value)
             {
                 Value = value;
             }
 
             public double Value { get; }
 
-            public static implicit operator double (ImplictDouble v)
+            public static implicit operator double (ImplicitDouble v)
             {
                 return v.Value;
             }
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
index 43192584af..2a8bbaae79 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_DataValidation.cs
@@ -49,7 +49,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         ////}
 
         [Fact]
-        public void Indei_Validation_Does_Not_Subscribe_When_DataValidatation_Not_Enabled()
+        public void Indei_Validation_Does_Not_Subscribe_When_DataValidation_Not_Enabled()
         {
             var data = new IndeiTest { MustBePositive = 5 };
             var observer = ExpressionObserver.Create(data, o => o.MustBePositive, false);
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
index 9b587d7679..6cd757331b 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_ExpressionTree.cs
@@ -42,7 +42,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         }
 
         [Fact]
-        public void Property_Acccess_Expression_Can_Set_Property()
+        public void Property_Access_Expression_Can_Set_Property()
         {
             var data = new Class1();
             var target = ExpressionObserver.Create(data, o => o.Foo);
diff --git a/tests/Avalonia.Base.UnitTests/Input/GesturesTests.cs b/tests/Avalonia.Base.UnitTests/Input/GesturesTests.cs
index 84ee35ba61..d466f6a4a5 100644
--- a/tests/Avalonia.Base.UnitTests/Input/GesturesTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Input/GesturesTests.cs
@@ -506,7 +506,7 @@ namespace Avalonia.Base.UnitTests.Input
         }
 
         [Fact]
-        public void Scrolling_Should_Start_After_Start_Distance_Is_Exceded()
+        public void Scrolling_Should_Start_After_Start_Distance_Is_Exceeded()
         {
             Border border = new Border()
             {
diff --git a/tests/Avalonia.Base.UnitTests/VisualTests.cs b/tests/Avalonia.Base.UnitTests/VisualTests.cs
index 973893af2d..fb214a6b34 100644
--- a/tests/Avalonia.Base.UnitTests/VisualTests.cs
+++ b/tests/Avalonia.Base.UnitTests/VisualTests.cs
@@ -126,7 +126,7 @@ namespace Avalonia.Base.UnitTests
         }
 
         [Fact]
-        public void Root_Should_Retun_Self_As_VisualRoot()
+        public void Root_Should_Return_Self_As_VisualRoot()
         {
             var root = new TestRoot();
 
@@ -134,7 +134,7 @@ namespace Avalonia.Base.UnitTests
         }
 
         [Fact]
-        public void Descendants_Should_RetunVisualRoot()
+        public void Descendants_Should_ReturnVisualRoot()
         {
             var root = new TestRoot();
             var child1 = new Decorator();
diff --git a/tests/Avalonia.Controls.UnitTests/WindowTests.cs b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
index 9dc0cb95bd..ca245005c2 100644
--- a/tests/Avalonia.Controls.UnitTests/WindowTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/WindowTests.cs
@@ -140,7 +140,7 @@ namespace Avalonia.Controls.UnitTests
         [Theory]
         [InlineData(true)]
         [InlineData(false)]
-        public void Child_windows_should_be_closed_before_parent(bool programaticClose)
+        public void Child_windows_should_be_closed_before_parent(bool programmaticClose)
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
@@ -156,7 +156,7 @@ namespace Avalonia.Controls.UnitTests
                 window.Closing += (sender, e) =>
                 {
                     Assert.Equal(WindowCloseReason.WindowClosing, e.CloseReason);
-                    Assert.Equal(programaticClose, e.IsProgrammatic);
+                    Assert.Equal(programmaticClose, e.IsProgrammatic);
                     count++;
                     windowClosing = count;
                 };
@@ -164,7 +164,7 @@ namespace Avalonia.Controls.UnitTests
                 child.Closing += (sender, e) =>
                 {
                     Assert.Equal(WindowCloseReason.OwnerWindowClosing, e.CloseReason);
-                    Assert.Equal(programaticClose, e.IsProgrammatic);
+                    Assert.Equal(programmaticClose, e.IsProgrammatic);
                     count++;
                     childClosing = count;
                 };
@@ -184,7 +184,7 @@ namespace Avalonia.Controls.UnitTests
                 window.Show();
                 child.Show(window);
 
-                if (programaticClose)
+                if (programmaticClose)
                 {
                     window.Close();
                 }
@@ -205,7 +205,7 @@ namespace Avalonia.Controls.UnitTests
         [Theory]
         [InlineData(true)]
         [InlineData(false)]
-        public void Child_windows_must_not_close_before_parent_has_chance_to_Cancel_OSCloseButton(bool programaticClose)
+        public void Child_windows_must_not_close_before_parent_has_chance_to_Cancel_OSCloseButton(bool programmaticClose)
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
@@ -246,7 +246,7 @@ namespace Avalonia.Controls.UnitTests
                 window.Show();
                 child.Show(window);
                 
-                if (programaticClose)
+                if (programmaticClose)
                 {
                     window.Close();
                 }
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs
index 18a6dd9803..0cdc9ee3b1 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BasicTests.cs
@@ -59,7 +59,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         }
 
         [Fact]
-        public void Attached_Property_Is_Set_On_Control_Outside_Avalonia_Namspace()
+        public void Attached_Property_Is_Set_On_Control_Outside_Avalonia_Namespace()
         {
             // Test for issue #1548
             var xaml =
@@ -729,7 +729,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         }
 
         [Fact]
-        public void DeferedXamlLoader_Should_Preserve_NamespacesContext()
+        public void DeferredXamlLoader_Should_Preserve_NamespacesContext()
         {
             var xaml =
 @"<ContentControl xmlns='https://github.com/avaloniaui'
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
index ccf44aaee2..6c29707dcd 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
@@ -41,7 +41,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
 
                 window.ApplyTemplate();
                 button.ApplyTemplate();
-                var listBoxHierarchyLine = button.GetVisualChildren().ElementAt(0) as ListBoxHierachyLine;
+                var listBoxHierarchyLine = button.GetVisualChildren().ElementAt(0) as ListBoxHierarchyLine;
                 Assert.Equal(1, listBoxHierarchyLine.LineDashStyle.Offset);
                 Assert.Equal(2, listBoxHierarchyLine.LineDashStyle.Dashes.Count);
                 Assert.Equal(2, listBoxHierarchyLine.LineDashStyle.Dashes[0]);
@@ -309,10 +309,10 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
             Assert.Equal("Bar", bar.Name);
         }
     }
-    public class ListBoxHierachyLine : Panel
+    public class ListBoxHierarchyLine : Panel
     {
         public static readonly StyledProperty<DashStyle> LineDashStyleProperty =
-        AvaloniaProperty.Register<ListBoxHierachyLine, DashStyle>(nameof(LineDashStyle));
+        AvaloniaProperty.Register<ListBoxHierarchyLine, DashStyle>(nameof(LineDashStyle));
 
         public DashStyle LineDashStyle
         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
index 70a5295008..ae1b12572e 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/StyleTests.cs
@@ -272,7 +272,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         }
 
         [Fact]
-        public void Style_Can_Use_NthChild_Selector_After_Reoder()
+        public void Style_Can_Use_NthChild_Selector_After_Reorder()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
@@ -311,7 +311,7 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
         }
 
         [Fact]
-        public void Style_Can_Use_NthLastChild_Selector_After_Reoder()
+        public void Style_Can_Use_NthLastChild_Selector_After_Reorder()
         {
             using (UnitTestApplication.Start(TestServices.StyledWindow))
             {
diff --git a/tests/Avalonia.RenderTests/Controls/TextBlockTests.cs b/tests/Avalonia.RenderTests/Controls/TextBlockTests.cs
index bddde3c3c6..c11bd2b816 100644
--- a/tests/Avalonia.RenderTests/Controls/TextBlockTests.cs
+++ b/tests/Avalonia.RenderTests/Controls/TextBlockTests.cs
@@ -45,7 +45,7 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
         [Win32Fact("Has text")]
         public async Task RestrictedHeight_VerticalAlign()
         {
-            Control text(VerticalAlignment verticalAlingnment, bool clip = true, bool restrictHeight = true)
+            Control text(VerticalAlignment verticalAlignment, bool clip = true, bool restrictHeight = true)
             {
                 return new Border()
                 {
@@ -62,7 +62,7 @@ namespace Avalonia.Direct2D1.RenderTests.Controls
                         FontSize = 24,
                         Foreground = Brushes.Black,
                         Text = "L",
-                        VerticalAlignment = verticalAlingnment,
+                        VerticalAlignment = verticalAlignment,
                         ClipToBounds = clip
                     }
                 };
diff --git a/tests/Avalonia.RenderTests/Media/TextFormatting/TextLayoutTests.cs b/tests/Avalonia.RenderTests/Media/TextFormatting/TextLayoutTests.cs
index f921d9fa64..6f47aa58d8 100644
--- a/tests/Avalonia.RenderTests/Media/TextFormatting/TextLayoutTests.cs
+++ b/tests/Avalonia.RenderTests/Media/TextFormatting/TextLayoutTests.cs
@@ -186,7 +186,7 @@ namespace Avalonia.Direct2D1.RenderTests.Media
         [InlineData("x", 0, 200, 200 - 7.20, 0, 7.20, FontSizeHeight)]
         [InlineData(stringword, 0, 200, 171.20, 0, 7.20, FontSizeHeight)]
         [InlineData(stringword, 3, 200, 200 - 7.20, 0, 7.20, FontSizeHeight)]
-        public void Should_HitTestPosition_RigthAlign_Correctly(
+        public void Should_HitTestPosition_RightAlign_Correctly(
                                                     string input, int index, double widthConstraint,
                                                     double x, double y, double width, double height)
         {
diff --git a/tests/Avalonia.RenderTests/OpacityMaskTests.cs b/tests/Avalonia.RenderTests/OpacityMaskTests.cs
index 2f01b03db6..6ce7e72df1 100644
--- a/tests/Avalonia.RenderTests/OpacityMaskTests.cs
+++ b/tests/Avalonia.RenderTests/OpacityMaskTests.cs
@@ -57,7 +57,7 @@ namespace Avalonia.Direct2D1.RenderTests
         }
 
         [Fact]
-        public async Task RenderTansform_Applies_To_Opacity_Mask()
+        public async Task RenderTransform_Applies_To_Opacity_Mask()
         {
             var target = new Canvas
             {

From 490c9b1ffe6a69037dee03b723bc1ba80b0ba0b2 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Fri, 6 Jan 2023 00:58:20 +0300
Subject: [PATCH 079/157] [Text] fix tab width. It's too long

---
 samples/ControlCatalog/Pages/TextBoxPage.xaml              | 2 +-
 .../Media/TextFormatting/TextParagraphProperties.cs        | 7 ++-----
 2 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/samples/ControlCatalog/Pages/TextBoxPage.xaml b/samples/ControlCatalog/Pages/TextBoxPage.xaml
index 6a4d9b7d0e..7408399873 100644
--- a/samples/ControlCatalog/Pages/TextBoxPage.xaml
+++ b/samples/ControlCatalog/Pages/TextBoxPage.xaml
@@ -38,7 +38,7 @@
                  UseFloatingWatermark="True"
                  PasswordChar="*"
                  Text="Password" />
-        <TextBox Width="200" Text="Left aligned text" TextAlignment="Left" />
+        <TextBox Width="200" Text="Left aligned text" TextAlignment="Left" AcceptsTab="True" />
         <TextBox Width="200" Text="Center aligned text" TextAlignment="Center" />
         <TextBox Width="200" Text="Right aligned text" TextAlignment="Right" />
         <TextBox Width="200" Text="Custom selection brush"
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextParagraphProperties.cs b/src/Avalonia.Base/Media/TextFormatting/TextParagraphProperties.cs
index 5691dd8ad0..27515738a4 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextParagraphProperties.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextParagraphProperties.cs
@@ -63,14 +63,11 @@
         {
             get { return 0; }
         }
-        
+
         /// <summary>
         /// Gets the default incremental tab width.
         /// </summary>
-        public virtual double DefaultIncrementalTab
-        {
-            get { return 4 * DefaultTextRunProperties.FontRenderingEmSize; }
-        }
+        public virtual double DefaultIncrementalTab => 0;
 
         /// <summary>
         /// Gets the letter spacing.

From 209861d9d405999c0e485a85637a61cfb2c1cb64 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:31:08 +1100
Subject: [PATCH 080/157] .

---
 ...rTransform_Applies_To_Opacity_Mask.expected.png} | Bin
 ...rTransform_Applies_To_Opacity_Mask.expected.png} | Bin
 2 files changed, 0 insertions(+), 0 deletions(-)
 rename tests/TestFiles/Direct2D1/OpacityMask/{RenderTansform_Applies_To_Opacity_Mask.expected.png => RenderTransform_Applies_To_Opacity_Mask.expected.png} (100%)
 rename tests/TestFiles/Skia/OpacityMask/{RenderTansform_Applies_To_Opacity_Mask.expected.png => RenderTransform_Applies_To_Opacity_Mask.expected.png} (100%)

diff --git a/tests/TestFiles/Direct2D1/OpacityMask/RenderTansform_Applies_To_Opacity_Mask.expected.png b/tests/TestFiles/Direct2D1/OpacityMask/RenderTransform_Applies_To_Opacity_Mask.expected.png
similarity index 100%
rename from tests/TestFiles/Direct2D1/OpacityMask/RenderTansform_Applies_To_Opacity_Mask.expected.png
rename to tests/TestFiles/Direct2D1/OpacityMask/RenderTransform_Applies_To_Opacity_Mask.expected.png
diff --git a/tests/TestFiles/Skia/OpacityMask/RenderTansform_Applies_To_Opacity_Mask.expected.png b/tests/TestFiles/Skia/OpacityMask/RenderTransform_Applies_To_Opacity_Mask.expected.png
similarity index 100%
rename from tests/TestFiles/Skia/OpacityMask/RenderTansform_Applies_To_Opacity_Mask.expected.png
rename to tests/TestFiles/Skia/OpacityMask/RenderTransform_Applies_To_Opacity_Mask.expected.png

From fb37ab1e7725deef8b54a69d21a17f92ba361c8d Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:46:29 +1100
Subject: [PATCH 081/157] leverage GetRequiredService

---
 samples/ControlCatalog.Desktop/Program.cs           |  2 +-
 samples/ControlCatalog/Pages/TabControlPage.xaml.cs |  2 +-
 .../ViewModels/CursorPageViewModel.cs               |  2 +-
 .../TransitioningContentControlPageViewModel.cs     |  2 +-
 src/Avalonia.Base/Input/Cursor.cs                   |  3 +--
 src/Avalonia.Base/Media/FontManager.cs              |  5 +----
 .../Media/TextFormatting/TextShaper.cs              |  5 +----
 src/Avalonia.Base/Rendering/RenderLoop.cs           |  3 +--
 src/Avalonia.Base/Threading/DispatcherTimer.cs      |  8 +-------
 src/Avalonia.Controls/Platform/PlatformManager.cs   | 13 +++----------
 src/Avalonia.DesignerSupport/DesignWindowLoader.cs  |  5 +----
 .../Internal/ManagedFileChooserViewModel.cs         |  2 +-
 src/Avalonia.OpenGL/Egl/EglInterface.cs             |  2 +-
 src/Avalonia.X11/X11Framebuffer.cs                  |  2 +-
 src/Avalonia.X11/X11Platform.cs                     |  2 +-
 .../Converters/BitmapTypeConverter.cs               |  2 +-
 .../Converters/IconTypeConverter.cs                 |  2 +-
 src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs |  2 +-
 src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs       |  6 +++---
 .../Media/DWriteResourceFontLoader.cs               |  2 +-
 .../Avalonia.Direct2D1/Media/DrawingContextImpl.cs  |  2 +-
 .../Wpf/Direct2DImageSurface.cs                     |  2 +-
 .../Media/Fonts/FontFamilyLoaderTests.cs            |  2 +-
 .../Avalonia.Controls.UnitTests/ContextMenuTests.cs |  2 +-
 tests/Avalonia.Controls.UnitTests/FlyoutTests.cs    |  2 +-
 .../MaskedTextBoxTests.cs                           |  2 +-
 .../Primitives/PopupTests.cs                        |  2 +-
 tests/Avalonia.Controls.UnitTests/TextBoxTests.cs   |  4 ++--
 tests/Avalonia.Controls.UnitTests/TreeViewTests.cs  |  9 ++++-----
 .../AutoSuspendHelperTest.cs                        |  6 +++---
 tests/Avalonia.RenderTests/TestBase.cs              |  2 +-
 tests/Avalonia.UnitTests/HarfBuzzFontManagerImpl.cs |  7 +------
 32 files changed, 42 insertions(+), 72 deletions(-)

diff --git a/samples/ControlCatalog.Desktop/Program.cs b/samples/ControlCatalog.Desktop/Program.cs
index 7b8b27fff7..4d28f15e2c 100644
--- a/samples/ControlCatalog.Desktop/Program.cs
+++ b/samples/ControlCatalog.Desktop/Program.cs
@@ -23,7 +23,7 @@ namespace ControlCatalog
         private static void ConfigureAssetAssembly(AppBuilder builder)
         {
             AvaloniaLocator.CurrentMutable
-                .GetService<IAssetLoader>()
+                .GetRequiredService<IAssetLoader>()
                 .SetDefaultAssembly(typeof(App).Assembly);
         }
     }
diff --git a/samples/ControlCatalog/Pages/TabControlPage.xaml.cs b/samples/ControlCatalog/Pages/TabControlPage.xaml.cs
index 413b6e1c75..f3f4bf6e93 100644
--- a/samples/ControlCatalog/Pages/TabControlPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/TabControlPage.xaml.cs
@@ -51,7 +51,7 @@ namespace ControlCatalog.Pages
 
         private static IBitmap LoadBitmap(string uri)
         {
-            var assets = AvaloniaLocator.Current!.GetService<IAssetLoader>()!;
+            var assets = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
             return new Bitmap(assets.Open(new Uri(uri)));
         }
     }
diff --git a/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs b/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
index 8a3f0ba947..12ca6af4f5 100644
--- a/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
@@ -18,7 +18,7 @@ namespace ControlCatalog.ViewModels
                 .Select(x => new StandardCursorModel(x))
                 .ToList();
 
-            var loader = AvaloniaLocator.Current!.GetService<IAssetLoader>()!;
+            var loader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>()!;
             var s = loader.Open(new Uri("avares://ControlCatalog/Assets/avalonia-32.png"));
             var bitmap = new Bitmap(s);
             CustomCursor = new Cursor(bitmap, new PixelPoint(16, 16));
diff --git a/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs b/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
index 93857fd899..f4e0bc8912 100644
--- a/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
@@ -19,7 +19,7 @@ namespace ControlCatalog.ViewModels
     {
         public TransitioningContentControlPageViewModel()
         {
-            var assetLoader = AvaloniaLocator.Current?.GetService<IAssetLoader>()!;
+            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>()!;
 
             var images = new string[] 
             { 
diff --git a/src/Avalonia.Base/Input/Cursor.cs b/src/Avalonia.Base/Input/Cursor.cs
index 8e79206f93..c555087879 100644
--- a/src/Avalonia.Base/Input/Cursor.cs
+++ b/src/Avalonia.Base/Input/Cursor.cs
@@ -71,8 +71,7 @@ namespace Avalonia.Input
 
         private static ICursorFactory GetCursorFactory()
         {
-            return AvaloniaLocator.Current.GetService<ICursorFactory>() ??
-                throw new Exception("Could not create Cursor: ICursorFactory not registered.");
+            return AvaloniaLocator.Current.GetRequiredService<ICursorFactory>();
         }
     }
 }
diff --git a/src/Avalonia.Base/Media/FontManager.cs b/src/Avalonia.Base/Media/FontManager.cs
index d92d003c2a..e82d5b7ba5 100644
--- a/src/Avalonia.Base/Media/FontManager.cs
+++ b/src/Avalonia.Base/Media/FontManager.cs
@@ -47,10 +47,7 @@ namespace Avalonia.Media
                     return current;
                 }
 
-                var fontManagerImpl = AvaloniaLocator.Current.GetService<IFontManagerImpl>();
-
-                if (fontManagerImpl == null)
-                    throw new InvalidOperationException("No font manager implementation was registered.");
+                var fontManagerImpl = AvaloniaLocator.Current.GetRequiredService<IFontManagerImpl>();
 
                 current = new FontManager(fontManagerImpl);
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs b/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
index 4aacec7c48..c161b08d20 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
@@ -29,10 +29,7 @@ namespace Avalonia.Media.TextFormatting
                     return current;
                 }
 
-                var textShaperImpl = AvaloniaLocator.Current.GetService<ITextShaperImpl>();
-
-                if (textShaperImpl == null)
-                    throw new InvalidOperationException("No text shaper implementation was registered.");
+                var textShaperImpl = AvaloniaLocator.Current.GetRequiredService<ITextShaperImpl>();
 
                 current = new TextShaper(textShaperImpl);
 
diff --git a/src/Avalonia.Base/Rendering/RenderLoop.cs b/src/Avalonia.Base/Rendering/RenderLoop.cs
index 5a08bfc6a1..1f58ca3827 100644
--- a/src/Avalonia.Base/Rendering/RenderLoop.cs
+++ b/src/Avalonia.Base/Rendering/RenderLoop.cs
@@ -50,8 +50,7 @@ namespace Avalonia.Rendering
         {
             get
             {
-                return _timer ??= AvaloniaLocator.Current.GetService<IRenderTimer>() ??
-                    throw new InvalidOperationException("Cannot locate IRenderTimer.");
+                return _timer ??= AvaloniaLocator.Current.GetRequiredService<IRenderTimer>();
             }
         }
 
diff --git a/src/Avalonia.Base/Threading/DispatcherTimer.cs b/src/Avalonia.Base/Threading/DispatcherTimer.cs
index 0c25d89722..8fc91a02d8 100644
--- a/src/Avalonia.Base/Threading/DispatcherTimer.cs
+++ b/src/Avalonia.Base/Threading/DispatcherTimer.cs
@@ -176,13 +176,7 @@ namespace Avalonia.Threading
         {
             if (!IsEnabled)
             {
-                var threading = AvaloniaLocator.Current.GetService<IPlatformThreadingInterface>();
-
-                if (threading == null)
-                {
-                    throw new Exception("Could not start timer: IPlatformThreadingInterface is not registered.");
-                }
-
+                var threading = AvaloniaLocator.Current.GetRequiredService<IPlatformThreadingInterface>();
                 _timer = threading.StartTimer(_priority, Interval, InternalTick);
             }
         }
diff --git a/src/Avalonia.Controls/Platform/PlatformManager.cs b/src/Avalonia.Controls/Platform/PlatformManager.cs
index de7708e869..b01fc28831 100644
--- a/src/Avalonia.Controls/Platform/PlatformManager.cs
+++ b/src/Avalonia.Controls/Platform/PlatformManager.cs
@@ -21,26 +21,19 @@ namespace Avalonia.Controls.Platform
         }
 
         public static ITrayIconImpl? CreateTrayIcon() =>
-            s_designerMode ? null : AvaloniaLocator.Current.GetService<IWindowingPlatform>()?.CreateTrayIcon();
+            s_designerMode ? null : AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>().CreateTrayIcon();
 
 
         public static IWindowImpl CreateWindow()
         {
-            var platform = AvaloniaLocator.Current.GetService<IWindowingPlatform>();
-            
-            if (platform == null)
-            {
-                throw new Exception("Could not CreateWindow(): IWindowingPlatform is not registered.");
-            }
+            var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
 
             return s_designerMode ? platform.CreateEmbeddableWindow() : platform.CreateWindow();
         }
 
         public static IWindowImpl CreateEmbeddableWindow()
         {
-            var platform = AvaloniaLocator.Current.GetService<IWindowingPlatform>();
-            if (platform == null)
-                throw new Exception("Could not CreateEmbeddableWindow(): IWindowingPlatform is not registered.");
+            var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
             return platform.CreateEmbeddableWindow();
         }
     }
diff --git a/src/Avalonia.DesignerSupport/DesignWindowLoader.cs b/src/Avalonia.DesignerSupport/DesignWindowLoader.cs
index b4cfffcdca..eff190c39e 100644
--- a/src/Avalonia.DesignerSupport/DesignWindowLoader.cs
+++ b/src/Avalonia.DesignerSupport/DesignWindowLoader.cs
@@ -18,12 +18,9 @@ namespace Avalonia.DesignerSupport
             Control control;
             using (PlatformManager.DesignerMode())
             {
-                var loader = AvaloniaLocator.Current.GetService<AvaloniaXamlLoader.IRuntimeXamlLoader>();
+                var loader = AvaloniaLocator.Current.GetRequiredService<AvaloniaXamlLoader.IRuntimeXamlLoader>();
                 var stream = new MemoryStream(Encoding.UTF8.GetBytes(xaml));
 
-                if (loader == null)
-                    throw new XamlLoadException("Runtime XAML loader is not registered");
-                
                 Uri baseUri = null;
                 if (assemblyPath != null)
                 {
diff --git a/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs b/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
index 7d0072c6ea..3de79927b2 100644
--- a/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
+++ b/src/Avalonia.Dialogs/Internal/ManagedFileChooserViewModel.cs
@@ -117,7 +117,7 @@ namespace Avalonia.Dialogs.Internal
                                               ?? new ManagedFileChooserSources();
 
             var sub1 = AvaloniaLocator.Current
-                                      .GetService<IMountedVolumeInfoProvider>()
+                                      .GetRequiredService<IMountedVolumeInfoProvider>()
                                       .Listen(ManagedFileChooserSources.MountedVolumes);
 
             var sub2 = Observable.FromEventPattern(ManagedFileChooserSources.MountedVolumes,
diff --git a/src/Avalonia.OpenGL/Egl/EglInterface.cs b/src/Avalonia.OpenGL/Egl/EglInterface.cs
index a913c05996..06aafb4f57 100644
--- a/src/Avalonia.OpenGL/Egl/EglInterface.cs
+++ b/src/Avalonia.OpenGL/Egl/EglInterface.cs
@@ -35,7 +35,7 @@ namespace Avalonia.OpenGL.Egl
 
         static Func<string, IntPtr> Load(string library)
         {
-            var dyn = AvaloniaLocator.Current.GetService<IDynamicLibraryLoader>();
+            var dyn = AvaloniaLocator.Current.GetRequiredService<IDynamicLibraryLoader>();
             var lib = dyn.LoadLibrary(library);
             return (s) => dyn.GetProcAddress(lib, s, true);
         }
diff --git a/src/Avalonia.X11/X11Framebuffer.cs b/src/Avalonia.X11/X11Framebuffer.cs
index 94f930e9ec..a9fedff8b5 100644
--- a/src/Avalonia.X11/X11Framebuffer.cs
+++ b/src/Avalonia.X11/X11Framebuffer.cs
@@ -25,7 +25,7 @@ namespace Avalonia.X11
             RowBytes = width * 4;
             Dpi = new Vector(96, 96) * factor;
             Format = PixelFormat.Bgra8888;
-            _blob = AvaloniaLocator.Current.GetService<IRuntimePlatform>().AllocBlob(RowBytes * height);
+            _blob = AvaloniaLocator.Current.GetRequiredService<IRuntimePlatform>().AllocBlob(RowBytes * height);
             Address = _blob.Address;
         }
         
diff --git a/src/Avalonia.X11/X11Platform.cs b/src/Avalonia.X11/X11Platform.cs
index 9692e0a384..0f9ef72a3f 100644
--- a/src/Avalonia.X11/X11Platform.cs
+++ b/src/Avalonia.X11/X11Platform.cs
@@ -105,7 +105,7 @@ namespace Avalonia.X11
             var gl = AvaloniaLocator.Current.GetService<IPlatformGraphics>();
             
             if (options.UseCompositor)
-                Compositor = new Compositor(AvaloniaLocator.Current.GetService<IRenderLoop>()!, gl);
+                Compositor = new Compositor(AvaloniaLocator.Current.GetRequiredService<IRenderLoop>(), gl);
             else
                 RenderInterface = new(gl);
 
diff --git a/src/Markup/Avalonia.Markup.Xaml/Converters/BitmapTypeConverter.cs b/src/Markup/Avalonia.Markup.Xaml/Converters/BitmapTypeConverter.cs
index dcd60f7a79..fc6a8557f3 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Converters/BitmapTypeConverter.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/Converters/BitmapTypeConverter.cs
@@ -24,7 +24,7 @@ namespace Avalonia.Markup.Xaml.Converters
             if(uri.IsAbsoluteUri && uri.IsFile)
                 return new Bitmap(uri.LocalPath);
 
-            var assets = AvaloniaLocator.Current.GetService<IAssetLoader>();
+            var assets = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
             return new Bitmap(assets.Open(uri, context.GetContextBaseUri()));
         }
     }
diff --git a/src/Markup/Avalonia.Markup.Xaml/Converters/IconTypeConverter.cs b/src/Markup/Avalonia.Markup.Xaml/Converters/IconTypeConverter.cs
index 24b690b6f1..698f5a9327 100644
--- a/src/Markup/Avalonia.Markup.Xaml/Converters/IconTypeConverter.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/Converters/IconTypeConverter.cs
@@ -40,7 +40,7 @@ namespace Avalonia.Markup.Xaml.Converters
             
             if(uri.IsAbsoluteUri && uri.IsFile)
                 return new WindowIcon(uri.LocalPath);
-            var assets = AvaloniaLocator.Current.GetService<IAssetLoader>();
+            var assets = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
             return new WindowIcon(assets.Open(uri, context.GetContextBaseUri()));
         }
     }
diff --git a/src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs b/src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs
index 5ca7f40d17..f7a86c11ff 100644
--- a/src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs
+++ b/src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs
@@ -37,7 +37,7 @@ namespace Avalonia.Skia
 
             var typeFaceCollection = new SKTypefaceCollection();
 
-            var assetLoader = AvaloniaLocator.Current.GetService<IAssetLoader>();
+            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
             foreach (var asset in fontAssets)
             {
diff --git a/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs b/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
index dcb267b2a3..12d9471204 100644
--- a/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
+++ b/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
@@ -96,9 +96,9 @@ namespace Avalonia.Skia
 
             SKColorType colorType = format.ToSkColorType();
             SKAlphaType alphaType = alphaFormat.ToSkAlphaType();
-            
-            var runtimePlatform = AvaloniaLocator.Current?.GetService<IRuntimePlatform>();
-            
+
+            var runtimePlatform = AvaloniaLocator.Current.GetRequiredService<IRuntimePlatform>();
+
             if (runtimePlatform != null)
             {
                 _bitmap = new SKBitmap();
diff --git a/src/Windows/Avalonia.Direct2D1/Media/DWriteResourceFontLoader.cs b/src/Windows/Avalonia.Direct2D1/Media/DWriteResourceFontLoader.cs
index e5f87e71a2..4663a6561f 100644
--- a/src/Windows/Avalonia.Direct2D1/Media/DWriteResourceFontLoader.cs
+++ b/src/Windows/Avalonia.Direct2D1/Media/DWriteResourceFontLoader.cs
@@ -22,7 +22,7 @@ namespace Avalonia.Direct2D1.Media
         {
             var factory1 = factory;
 
-            var assetLoader = AvaloniaLocator.Current.GetService<IAssetLoader>();
+            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
             foreach (var asset in fontAssets)
             {
diff --git a/src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs b/src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs
index 180ae491b3..3f2298eb22 100644
--- a/src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs
+++ b/src/Windows/Avalonia.Direct2D1/Media/DrawingContextImpl.cs
@@ -409,7 +409,7 @@ namespace Avalonia.Direct2D1.Media
             }
             else
             {
-                var platform = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
+                var platform = AvaloniaLocator.Current.GetRequiredService<IPlatformRenderInterface>();
                 var dpi = new Vector(_deviceContext.DotsPerInch.Width, _deviceContext.DotsPerInch.Height);
                 var pixelSize = PixelSize.FromSizeWithDpi(size, dpi);
                 return (IDrawingContextLayerImpl)platform.CreateRenderTargetBitmap(pixelSize, dpi);
diff --git a/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs b/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
index a5474803a1..e607e255a5 100644
--- a/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
+++ b/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
@@ -127,7 +127,7 @@ namespace Avalonia.Win32.Interop.Wpf
                 DeviceWindowHandle = GetDesktopWindow(),
                 PresentationInterval = PresentInterval.Default
             };
-            s_dxDevice = s_dxDevice ?? AvaloniaLocator.Current.GetService<SharpDX.DXGI.Device>()
+            s_dxDevice = s_dxDevice ?? AvaloniaLocator.Current.GetRequiredService<SharpDX.DXGI.Device>()
                              .QueryInterface<SharpDX.Direct3D11.Device>();
             s_d3DDevice = new DeviceEx(s_d3DContext, 0, DeviceType.Hardware, IntPtr.Zero, CreateFlags.HardwareVertexProcessing | CreateFlags.Multithreaded | CreateFlags.FpuPreserve, presentparams);
 
diff --git a/tests/Avalonia.Base.UnitTests/Media/Fonts/FontFamilyLoaderTests.cs b/tests/Avalonia.Base.UnitTests/Media/Fonts/FontFamilyLoaderTests.cs
index aa042ffec8..afc25ab88e 100644
--- a/tests/Avalonia.Base.UnitTests/Media/Fonts/FontFamilyLoaderTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Media/Fonts/FontFamilyLoaderTests.cs
@@ -97,7 +97,7 @@ namespace Avalonia.Base.UnitTests.Media.Fonts
         {
             using (UnitTestApplication.Start(TestServices.MockPlatformRenderInterface))
             {
-                var assetLoader = AvaloniaLocator.Current.GetService<IAssetLoader>();
+                var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
                 var fontFamily = new FontFamily("resm:Avalonia.Base.UnitTests.Assets?assembly=Avalonia.Base.UnitTests#Noto Mono");
 
diff --git a/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs b/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
index d6c521decd..baf933bd66 100644
--- a/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ContextMenuTests.cs
@@ -596,7 +596,7 @@ namespace Avalonia.Controls.UnitTests
         private static Window PreparedWindow(object content = null)
         {
             var renderer = new Mock<IRenderer>();
-            var platform = AvaloniaLocator.Current.GetService<IWindowingPlatform>();
+            var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
             var windowImpl = Mock.Get(platform.CreateWindow());
             windowImpl.Setup(x => x.CreateRenderer(It.IsAny<IRenderRoot>())).Returns(renderer.Object);
 
diff --git a/tests/Avalonia.Controls.UnitTests/FlyoutTests.cs b/tests/Avalonia.Controls.UnitTests/FlyoutTests.cs
index 496b5bc1b6..02767a21eb 100644
--- a/tests/Avalonia.Controls.UnitTests/FlyoutTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/FlyoutTests.cs
@@ -570,7 +570,7 @@ namespace Avalonia.Controls.UnitTests
         private static Window PreparedWindow(object content = null)
         {
             var renderer = new Mock<IRenderer>();
-            var platform = AvaloniaLocator.Current.GetService<IWindowingPlatform>();
+            var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
             var windowImpl = Mock.Get(platform.CreateWindow());
             windowImpl.Setup(x => x.CreateRenderer(It.IsAny<IRenderRoot>())).Returns(renderer.Object);
 
diff --git a/tests/Avalonia.Controls.UnitTests/MaskedTextBoxTests.cs b/tests/Avalonia.Controls.UnitTests/MaskedTextBoxTests.cs
index 90c6fd3b21..c1d9fad6f4 100644
--- a/tests/Avalonia.Controls.UnitTests/MaskedTextBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/MaskedTextBoxTests.cs
@@ -827,7 +827,7 @@ namespace Avalonia.Controls.UnitTests
                 {
                     AvaloniaLocator.CurrentMutable.Bind<IClipboard>().ToSingleton<ClipboardStub>();
 
-                    var clipboard = AvaloniaLocator.CurrentMutable.GetService<IClipboard>();
+                    var clipboard = AvaloniaLocator.CurrentMutable.GetRequiredService<IClipboard>();
                     clipboard.SetTextAsync(textInput).GetAwaiter().GetResult();
 
                     RaiseKeyEvent(target, Key.V, KeyModifiers.Control);
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
index d4193d33ee..65957fda6d 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/PopupTests.cs
@@ -564,7 +564,7 @@ namespace Avalonia.Controls.UnitTests.Primitives
             using (CreateServices())
             {
                 var renderer = new Mock<IRenderer>();
-                var platform = AvaloniaLocator.Current.GetService<IWindowingPlatform>();
+                var platform = AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>();
                 var windowImpl = Mock.Get(platform.CreateWindow());
                 windowImpl.Setup(x => x.CreateRenderer(It.IsAny<IRenderRoot>())).Returns(renderer.Object);
 
diff --git a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
index bd6d5d55e2..531a2869cd 100644
--- a/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TextBoxTests.cs
@@ -767,7 +767,7 @@ namespace Avalonia.Controls.UnitTests
                 {
                     AvaloniaLocator.CurrentMutable.Bind<IClipboard>().ToSingleton<ClipboardStub>();
                     
-                    var clipboard = AvaloniaLocator.CurrentMutable.GetService<IClipboard>();
+                    var clipboard = AvaloniaLocator.CurrentMutable.GetRequiredService<IClipboard>();
                     clipboard.SetTextAsync(textInput).GetAwaiter().GetResult();
 
                     RaiseKeyEvent(target, Key.V, KeyModifiers.Control);
@@ -876,7 +876,7 @@ namespace Avalonia.Controls.UnitTests
 
                 AvaloniaLocator.CurrentMutable.Bind<IClipboard>().ToSingleton<ClipboardStub>();
 
-                var clipboard = AvaloniaLocator.CurrentMutable.GetService<IClipboard>();
+                var clipboard = AvaloniaLocator.CurrentMutable.GetRequiredService<IClipboard>();
                 clipboard.SetTextAsync(Environment.NewLine).GetAwaiter().GetResult();
 
                 RaiseKeyEvent(target, Key.V, KeyModifiers.Control);
diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index 81936711ef..f526465b9b 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -1248,7 +1248,7 @@ namespace Avalonia.Controls.UnitTests
             using (Application())
             {
                 var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
+                var navigation = AvaloniaLocator.Current.GetRequiredService<IKeyboardNavigationHandler>();
                 var data = CreateTestTreeData();
 
                 var target = new TreeView
@@ -1293,7 +1293,6 @@ namespace Avalonia.Controls.UnitTests
             using (Application())
             {
                 var focus = FocusManager.Instance;
-                var navigation = AvaloniaLocator.Current.GetService<IKeyboardNavigationHandler>();
                 var data = CreateTestTreeData();
 
                 var selectedNode = new Node { Value = "Out of Tree Selected Item" };
@@ -1353,7 +1352,7 @@ namespace Avalonia.Controls.UnitTests
 
                 var rootNode = tree[0];
 
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var keymap = AvaloniaLocator.Current.GetRequiredService<PlatformHotkeyConfiguration>();
                 var selectAllGesture = keymap.SelectAll.First();
 
                 var keyEvent = new KeyEventArgs
@@ -1400,7 +1399,7 @@ namespace Avalonia.Controls.UnitTests
                 ClickContainer(fromContainer, KeyModifiers.None);
                 ClickContainer(toContainer, KeyModifiers.Shift);
 
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var keymap = AvaloniaLocator.Current.GetRequiredService<PlatformHotkeyConfiguration>();
                 var selectAllGesture = keymap.SelectAll.First();
 
                 var keyEvent = new KeyEventArgs
@@ -1447,7 +1446,7 @@ namespace Avalonia.Controls.UnitTests
                 ClickContainer(fromContainer, KeyModifiers.None);
                 ClickContainer(toContainer, KeyModifiers.Shift);
 
-                var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+                var keymap = AvaloniaLocator.Current.GetRequiredService<PlatformHotkeyConfiguration>();
                 var selectAllGesture = keymap.SelectAll.First();
 
                 var keyEvent = new KeyEventArgs
diff --git a/tests/Avalonia.ReactiveUI.UnitTests/AutoSuspendHelperTest.cs b/tests/Avalonia.ReactiveUI.UnitTests/AutoSuspendHelperTest.cs
index 196375fb40..30326adba5 100644
--- a/tests/Avalonia.ReactiveUI.UnitTests/AutoSuspendHelperTest.cs
+++ b/tests/Avalonia.ReactiveUI.UnitTests/AutoSuspendHelperTest.cs
@@ -47,7 +47,7 @@ namespace Avalonia.ReactiveUI.UnitTests
             using (var lifetime = new ClassicDesktopStyleApplicationLifetime())
             {
                 var isLaunchingReceived = false;
-                var application = AvaloniaLocator.Current.GetService<Application>();
+                var application = AvaloniaLocator.Current.GetRequiredService<Application>();
                 application.ApplicationLifetime = lifetime;
 
                 // Initialize ReactiveUI Suspension as in real-world scenario.
@@ -65,7 +65,7 @@ namespace Avalonia.ReactiveUI.UnitTests
             using (UnitTestApplication.Start(TestServices.MockWindowingPlatform))
             using (var lifetime = new ExoticApplicationLifetimeWithoutLifecycleEvents()) 
             {
-                var application = AvaloniaLocator.Current.GetService<Application>();
+                var application = AvaloniaLocator.Current.GetRequiredService<Application>();
                 application.ApplicationLifetime = lifetime;
                 Assert.Throws<NotSupportedException>(() => new AutoSuspendHelper(application.ApplicationLifetime));
             }
@@ -88,7 +88,7 @@ namespace Avalonia.ReactiveUI.UnitTests
             using (var lifetime = new ClassicDesktopStyleApplicationLifetime()) 
             {
                 var shouldPersistReceived = false;
-                var application = AvaloniaLocator.Current.GetService<Application>();
+                var application = AvaloniaLocator.Current.GetRequiredService<Application>();
                 application.ApplicationLifetime = lifetime;
 
                 // Initialize ReactiveUI Suspension as in real-world scenario.
diff --git a/tests/Avalonia.RenderTests/TestBase.cs b/tests/Avalonia.RenderTests/TestBase.cs
index 313281d6c6..edde62f041 100644
--- a/tests/Avalonia.RenderTests/TestBase.cs
+++ b/tests/Avalonia.RenderTests/TestBase.cs
@@ -91,7 +91,7 @@ namespace Avalonia.Direct2D1.RenderTests
             var immediatePath = Path.Combine(OutputPath, testName + ".immediate.out.png");
             var deferredPath = Path.Combine(OutputPath, testName + ".deferred.out.png");
             var compositedPath = Path.Combine(OutputPath, testName + ".composited.out.png");
-            var factory = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
+            var factory = AvaloniaLocator.Current.GetRequiredService<IPlatformRenderInterface>();
             var pixelSize = new PixelSize((int)target.Width, (int)target.Height);
             var size = new Size(target.Width, target.Height);
             var dpiVector = new Vector(dpi, dpi);
diff --git a/tests/Avalonia.UnitTests/HarfBuzzFontManagerImpl.cs b/tests/Avalonia.UnitTests/HarfBuzzFontManagerImpl.cs
index 2b1685f358..55ac16054d 100644
--- a/tests/Avalonia.UnitTests/HarfBuzzFontManagerImpl.cs
+++ b/tests/Avalonia.UnitTests/HarfBuzzFontManagerImpl.cs
@@ -76,13 +76,8 @@ namespace Avalonia.UnitTests
 
             var asset = fontAssets.First();
             
-            var assetLoader = AvaloniaLocator.Current.GetService<IAssetLoader>();
+            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
-            if (assetLoader == null)
-            {
-                throw new NotSupportedException("IAssetLoader is not registered.");
-            }
-            
             var stream = assetLoader.Open(asset);
             
             return new HarfBuzzGlyphTypefaceImpl(stream);

From 698977d2836e41bc6bb4083f14bf1ced746bb2fb Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:47:27 +1100
Subject: [PATCH 082/157] .

---
 samples/ControlCatalog/ViewModels/CursorPageViewModel.cs        | 2 +-
 .../ViewModels/TransitioningContentControlPageViewModel.cs      | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs b/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
index 12ca6af4f5..f44d927801 100644
--- a/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/CursorPageViewModel.cs
@@ -18,7 +18,7 @@ namespace ControlCatalog.ViewModels
                 .Select(x => new StandardCursorModel(x))
                 .ToList();
 
-            var loader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>()!;
+            var loader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
             var s = loader.Open(new Uri("avares://ControlCatalog/Assets/avalonia-32.png"));
             var bitmap = new Bitmap(s);
             CustomCursor = new Cursor(bitmap, new PixelPoint(16, 16));
diff --git a/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs b/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
index f4e0bc8912..4505c11e95 100644
--- a/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/TransitioningContentControlPageViewModel.cs
@@ -19,7 +19,7 @@ namespace ControlCatalog.ViewModels
     {
         public TransitioningContentControlPageViewModel()
         {
-            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>()!;
+            var assetLoader = AvaloniaLocator.Current.GetRequiredService<IAssetLoader>();
 
             var images = new string[] 
             { 

From 16ffe2f6f99d41adab83e58b9f0f927daaf92bae Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:50:23 +1100
Subject: [PATCH 083/157] use default literal

---
 .../Data/Converters/FuncMultiValueConverter.cs            | 2 +-
 src/Avalonia.Base/Layout/WrapLayout/UvMeasure.cs          | 2 +-
 src/Avalonia.Base/Media/DrawingContext.cs                 | 2 +-
 src/Avalonia.Base/Media/DrawingGroup.cs                   | 4 ++--
 src/Avalonia.Base/Media/ImmediateDrawingContext.cs        | 2 +-
 .../Composition/Expressions/ExpressionVariant.cs          | 2 +-
 src/Avalonia.Base/Rendering/ImmediateRenderer.cs          | 6 +++---
 .../Rendering/Utilities/TileBrushCalculator.cs            | 2 +-
 src/Avalonia.Base/Utilities/SingleOrDictionary.cs         | 2 +-
 src/Avalonia.Base/Utilities/StringTokenizer.cs            | 4 ++--
 src/Avalonia.Controls.DataGrid/DataGrid.cs                | 4 ++--
 src/Avalonia.Controls.DataGrid/IndexToValueTable.cs       | 2 +-
 src/Avalonia.Controls/Platform/InProcessDragSource.cs     | 2 +-
 .../Presenters/ScrollContentPresenter.cs                  | 4 ++--
 src/Avalonia.Controls/Utils/UndoRedoHelper.cs             | 2 +-
 src/Avalonia.FreeDesktop/DBusMenu.cs                      | 8 ++++----
 .../Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs  | 2 +-
 src/Skia/Avalonia.Skia/DrawingContextImpl.cs              | 4 ++--
 src/Skia/Avalonia.Skia/GeometryImpl.cs                    | 2 +-
 .../Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs    | 4 ++--
 src/Windows/Avalonia.Win32/DataObject.cs                  | 2 +-
 src/Windows/Avalonia.Win32/OleDropTarget.cs               | 2 +-
 .../ItemsPresenterTests_Virtualization_Simple.cs          | 2 +-
 23 files changed, 34 insertions(+), 34 deletions(-)

diff --git a/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs b/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
index 2577cac743..5084d8e822 100644
--- a/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
+++ b/src/Avalonia.Base/Data/Converters/FuncMultiValueConverter.cs
@@ -38,7 +38,7 @@ namespace Avalonia.Data.Converters
                     }
                     else if (Equals(obj, default(TIn)))
                     {
-                        yield return default(TIn);
+                        yield return default;
                     }
                 }
             }
diff --git a/src/Avalonia.Base/Layout/WrapLayout/UvMeasure.cs b/src/Avalonia.Base/Layout/WrapLayout/UvMeasure.cs
index 91fa459acb..fa298b53a3 100644
--- a/src/Avalonia.Base/Layout/WrapLayout/UvMeasure.cs
+++ b/src/Avalonia.Base/Layout/WrapLayout/UvMeasure.cs
@@ -7,7 +7,7 @@ namespace Avalonia.Layout
 {    
     internal struct UvMeasure
     {
-        internal static readonly UvMeasure Zero = default(UvMeasure);
+        internal static readonly UvMeasure Zero = default;
 
         internal double U { get; set; }
 
diff --git a/src/Avalonia.Base/Media/DrawingContext.cs b/src/Avalonia.Base/Media/DrawingContext.cs
index eabd7c8274..077816c645 100644
--- a/src/Avalonia.Base/Media/DrawingContext.cs
+++ b/src/Avalonia.Base/Media/DrawingContext.cs
@@ -279,7 +279,7 @@ namespace Avalonia.Media
                 OpacityMask,
             }
 
-            public PushedState(DrawingContext context, PushedStateType type, Matrix matrix = default(Matrix))
+            public PushedState(DrawingContext context, PushedStateType type, Matrix matrix = default)
             {
                 if (context._states is null)
                     throw new ObjectDisposedException(nameof(DrawingContext));
diff --git a/src/Avalonia.Base/Media/DrawingGroup.cs b/src/Avalonia.Base/Media/DrawingGroup.cs
index 4a46d89153..7d3b4c056e 100644
--- a/src/Avalonia.Base/Media/DrawingGroup.cs
+++ b/src/Avalonia.Base/Media/DrawingGroup.cs
@@ -76,8 +76,8 @@ namespace Avalonia.Media
         {
             using (context.PushPreTransform(Transform?.Value ?? Matrix.Identity))
             using (context.PushOpacity(Opacity))
-            using (ClipGeometry != null ? context.PushGeometryClip(ClipGeometry) : default(DrawingContext.PushedState))
-            using (OpacityMask != null ? context.PushOpacityMask(OpacityMask, GetBounds()) : default(DrawingContext.PushedState))
+            using (ClipGeometry != null ? context.PushGeometryClip(ClipGeometry) : default)
+            using (OpacityMask != null ? context.PushOpacityMask(OpacityMask, GetBounds()) : default)
             {
                 foreach (var drawing in Children)
                 {
diff --git a/src/Avalonia.Base/Media/ImmediateDrawingContext.cs b/src/Avalonia.Base/Media/ImmediateDrawingContext.cs
index 1e1a73437d..eb6f105680 100644
--- a/src/Avalonia.Base/Media/ImmediateDrawingContext.cs
+++ b/src/Avalonia.Base/Media/ImmediateDrawingContext.cs
@@ -218,7 +218,7 @@ namespace Avalonia.Media
                 OpacityMask,
             }
 
-            internal PushedState(ImmediateDrawingContext context, PushedStateType type, Matrix matrix = default(Matrix))
+            internal PushedState(ImmediateDrawingContext context, PushedStateType type, Matrix matrix = default)
             {
                 if (context._states is null)
                     throw new ObjectDisposedException(nameof(ImmediateDrawingContext));
diff --git a/src/Avalonia.Base/Rendering/Composition/Expressions/ExpressionVariant.cs b/src/Avalonia.Base/Rendering/Composition/Expressions/ExpressionVariant.cs
index 6e53a138cd..21f14283b5 100644
--- a/src/Avalonia.Base/Rendering/Composition/Expressions/ExpressionVariant.cs
+++ b/src/Avalonia.Base/Rendering/Composition/Expressions/ExpressionVariant.cs
@@ -654,7 +654,7 @@ namespace Avalonia.Rendering.Composition.Expressions
                 }
             }
 
-            res = default(T);
+            res = default;
             return false;
         }
 
diff --git a/src/Avalonia.Base/Rendering/ImmediateRenderer.cs b/src/Avalonia.Base/Rendering/ImmediateRenderer.cs
index 4909c78ed1..60b144e806 100644
--- a/src/Avalonia.Base/Rendering/ImmediateRenderer.cs
+++ b/src/Avalonia.Base/Rendering/ImmediateRenderer.cs
@@ -330,11 +330,11 @@ namespace Avalonia.Rendering
                     ? visual is IVisualWithRoundRectClip roundClipVisual
                         ? context.PushClip(new RoundedRect(bounds, roundClipVisual.ClipToBoundsRadius))
                         : context.PushClip(bounds) 
-                    : default(DrawingContext.PushedState))
+                    : default)
 #pragma warning restore CS0618 // Type or member is obsolete
 
-                using (visual.Clip != null ? context.PushGeometryClip(visual.Clip) : default(DrawingContext.PushedState))
-                using (visual.OpacityMask != null ? context.PushOpacityMask(visual.OpacityMask, bounds) : default(DrawingContext.PushedState))
+                using (visual.Clip != null ? context.PushGeometryClip(visual.Clip) : default)
+                using (visual.OpacityMask != null ? context.PushOpacityMask(visual.OpacityMask, bounds) : default)
                 using (context.PushTransformContainer())
                 {
                     visual.Render(context);
diff --git a/src/Avalonia.Base/Rendering/Utilities/TileBrushCalculator.cs b/src/Avalonia.Base/Rendering/Utilities/TileBrushCalculator.cs
index af2c7f71dc..6b34b44337 100644
--- a/src/Avalonia.Base/Rendering/Utilities/TileBrushCalculator.cs
+++ b/src/Avalonia.Base/Rendering/Utilities/TileBrushCalculator.cs
@@ -109,7 +109,7 @@ namespace Avalonia.Rendering.Utilities
             {
                 if (IntermediateTransform != Matrix.Identity)
                     return true;
-                if (SourceRect.Position != default(Point))
+                if (SourceRect.Position != default)
                     return true;
                 if (SourceRect.Size.AspectRatio == _imageSize.AspectRatio)
                     return false;
diff --git a/src/Avalonia.Base/Utilities/SingleOrDictionary.cs b/src/Avalonia.Base/Utilities/SingleOrDictionary.cs
index 00cc5864f5..0eb7ae2e31 100644
--- a/src/Avalonia.Base/Utilities/SingleOrDictionary.cs
+++ b/src/Avalonia.Base/Utilities/SingleOrDictionary.cs
@@ -42,7 +42,7 @@ namespace Avalonia.Utilities
             {
                 if (!_singleValue.HasValue || !EqualityComparer<TKey>.Default.Equals(_singleValue.Value.Key, key))
                 {
-                    value = default(TValue);
+                    value = default;
                     return false;
                 }
                 else
diff --git a/src/Avalonia.Base/Utilities/StringTokenizer.cs b/src/Avalonia.Base/Utilities/StringTokenizer.cs
index 726c9735ef..aad742e02b 100644
--- a/src/Avalonia.Base/Utilities/StringTokenizer.cs
+++ b/src/Avalonia.Base/Utilities/StringTokenizer.cs
@@ -63,7 +63,7 @@ namespace Avalonia.Utilities
             }
             else
             {
-                result = default(Int32);
+                result = default;
                 return false;
             }
         }
@@ -87,7 +87,7 @@ namespace Avalonia.Utilities
             }
             else
             {
-                result = default(double);
+                result = default;
                 return false;
             }
         }
diff --git a/src/Avalonia.Controls.DataGrid/DataGrid.cs b/src/Avalonia.Controls.DataGrid/DataGrid.cs
index 78de00078e..83a0dd3ce1 100644
--- a/src/Avalonia.Controls.DataGrid/DataGrid.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGrid.cs
@@ -1118,7 +1118,7 @@ namespace Avalonia.Controls
                     EnsureColumnHeadersVisibility();
                     if (!newValueCols)
                     {
-                        _columnHeadersPresenter.Measure(default(Size));
+                        _columnHeadersPresenter.Measure(default);
                     }
                     else
                     {
@@ -1159,7 +1159,7 @@ namespace Avalonia.Controls
                 _topLeftCornerHeader.IsVisible = newValueRows && newValueCols;
                 if (_topLeftCornerHeader.IsVisible)
                 {
-                    _topLeftCornerHeader.Measure(default(Size));
+                    _topLeftCornerHeader.Measure(default);
                 }
             }
 
diff --git a/src/Avalonia.Controls.DataGrid/IndexToValueTable.cs b/src/Avalonia.Controls.DataGrid/IndexToValueTable.cs
index 65c3af344c..68a2fc562f 100644
--- a/src/Avalonia.Controls.DataGrid/IndexToValueTable.cs
+++ b/src/Avalonia.Controls.DataGrid/IndexToValueTable.cs
@@ -422,7 +422,7 @@ namespace Avalonia.Controls
             else
             {
                 found = false;
-                return default(T);
+                return default;
             }
         }
 
diff --git a/src/Avalonia.Controls/Platform/InProcessDragSource.cs b/src/Avalonia.Controls/Platform/InProcessDragSource.cs
index 5b2356a7ce..196fd898cf 100644
--- a/src/Avalonia.Controls/Platform/InProcessDragSource.cs
+++ b/src/Avalonia.Controls/Platform/InProcessDragSource.cs
@@ -41,7 +41,7 @@ namespace Avalonia.Platform
             {
                 _draggedData = data;
                 _lastRoot = null;
-                _lastPosition = default(Point);
+                _lastPosition = default;
                 _allowedEffects = allowedEffects;
 
                 using (_inputManager.PreProcess.OfType<RawPointerEventArgs>().Subscribe(ProcessMouseEvents))
diff --git a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
index 328facba0b..51f85a3e3d 100644
--- a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
@@ -500,7 +500,7 @@ namespace Avalonia.Controls.Presenters
 
             if (e.OldValue != null)
             {
-                Offset = default(Vector);
+                Offset = default;
             }
         }
 
@@ -542,7 +542,7 @@ namespace Avalonia.Controls.Presenters
             if (logicalScroll != scrollable.IsLogicalScrollEnabled)
             {
                 UpdateScrollableSubscription(Child);
-                Offset = default(Vector);
+                Offset = default;
                 InvalidateMeasure();
             }
             else if (scrollable.IsLogicalScrollEnabled)
diff --git a/src/Avalonia.Controls/Utils/UndoRedoHelper.cs b/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
index 6ff72751a6..7b663dd017 100644
--- a/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
+++ b/src/Avalonia.Controls/Utils/UndoRedoHelper.cs
@@ -49,7 +49,7 @@ namespace Avalonia.Controls.Utils
 
         public bool TryGetLastState(out TState? _state)
         {
-            _state = default(TState);
+            _state = default;
             if (!IsLastState)
                 return false;
 
diff --git a/src/Avalonia.FreeDesktop/DBusMenu.cs b/src/Avalonia.FreeDesktop/DBusMenu.cs
index 3a1c65e7c9..7e22988270 100644
--- a/src/Avalonia.FreeDesktop/DBusMenu.cs
+++ b/src/Avalonia.FreeDesktop/DBusMenu.cs
@@ -36,10 +36,10 @@ namespace Avalonia.FreeDesktop.DBusMenu
     [Dictionary]
     class DBusMenuProperties
     {
-        public uint Version { get; set; } = default (uint);
-        public string? TextDirection { get; set; } = default (string);
-        public string? Status { get; set; } = default (string);
-        public string[]? IconThemePath { get; set; } = default (string[]);
+        public uint Version { get; set; } = default;
+        public string? TextDirection { get; set; } = default;
+        public string? Status { get; set; } = default;
+        public string[]? IconThemePath { get; set; } = default;
     }
 
 
diff --git a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
index ac54365f51..6032f3a92c 100644
--- a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
+++ b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
@@ -25,7 +25,7 @@ namespace Avalonia.LinuxFramebuffer
 
             Surfaces = new object[] { _outputBackend };
 
-            Invalidate(default(Rect));
+            Invalidate(default);
             _inputBackend.Initialize(this, e => Input?.Invoke(e));
         }
 
diff --git a/src/Skia/Avalonia.Skia/DrawingContextImpl.cs b/src/Skia/Avalonia.Skia/DrawingContextImpl.cs
index 48e8c761eb..8b71f4e17e 100644
--- a/src/Skia/Avalonia.Skia/DrawingContextImpl.cs
+++ b/src/Skia/Avalonia.Skia/DrawingContextImpl.cs
@@ -224,9 +224,9 @@ namespace Avalonia.Skia
             var impl = (GeometryImpl) geometry;
             var size = geometry.Bounds.Size;
 
-            using (var fill = brush != null ? CreatePaint(_fillPaint, brush, size) : default(PaintWrapper))
+            using (var fill = brush != null ? CreatePaint(_fillPaint, brush, size) : default)
             using (var stroke = pen?.Brush != null ? CreatePaint(_strokePaint, pen, 
-                size.Inflate(new Thickness(pen?.Thickness / 2 ?? 0))) : default(PaintWrapper))
+                size.Inflate(new Thickness(pen?.Thickness / 2 ?? 0))) : default)
             {
                 if (fill.Paint != null)
                 {
diff --git a/src/Skia/Avalonia.Skia/GeometryImpl.cs b/src/Skia/Avalonia.Skia/GeometryImpl.cs
index 1141763097..15a3ebff40 100644
--- a/src/Skia/Avalonia.Skia/GeometryImpl.cs
+++ b/src/Skia/Avalonia.Skia/GeometryImpl.cs
@@ -245,7 +245,7 @@ namespace Avalonia.Skia
             {
                 CachedStrokePath?.Dispose();
                 CachedGeometryRenderBounds = default;
-                _cachedStrokeWidth = default(float);
+                _cachedStrokeWidth = default;
             }
         }
     }
diff --git a/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs b/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
index a5474803a1..5526ee69ac 100644
--- a/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
+++ b/src/Windows/Avalonia.Win32.Interop/Wpf/Direct2DImageSurface.cs
@@ -156,7 +156,7 @@ namespace Avalonia.Win32.Interop.Wpf
             _impl.ImageSource = _image;
 
             RemoveAndDispose(ref _backBuffer);
-            if (size == default(IntSize))
+            if (size == default)
             {
                 _image.Lock();
                 _image.SetBackBuffer(D3DResourceType.IDirect3DSurface9, IntPtr.Zero);
@@ -171,7 +171,7 @@ namespace Avalonia.Win32.Interop.Wpf
         static void RemoveAndDispose<T>(ref T d) where T : IDisposable
         {
             d?.Dispose();
-            d = default(T);
+            d = default;
         }
 
         void Swap()
diff --git a/src/Windows/Avalonia.Win32/DataObject.cs b/src/Windows/Avalonia.Win32/DataObject.cs
index b7a567ea97..7d22e57a30 100644
--- a/src/Windows/Avalonia.Win32/DataObject.cs
+++ b/src/Windows/Avalonia.Win32/DataObject.cs
@@ -205,7 +205,7 @@ namespace Avalonia.Win32
             if (string.IsNullOrEmpty(fmt) || !_wrapped.Contains(fmt))
                 return DV_E_FORMATETC;
 
-            * medium = default(Interop.STGMEDIUM);
+            * medium = default;
             medium->tymed = TYMED.TYMED_HGLOBAL;
             return WriteDataToHGlobal(fmt, ref medium->unionmember);
         }
diff --git a/src/Windows/Avalonia.Win32/OleDropTarget.cs b/src/Windows/Avalonia.Win32/OleDropTarget.cs
index b4eb6d8851..8bbdfe5fd9 100644
--- a/src/Windows/Avalonia.Win32/OleDropTarget.cs
+++ b/src/Windows/Avalonia.Win32/OleDropTarget.cs
@@ -121,7 +121,7 @@ namespace Avalonia.Win32
                     _dragDevice,
                     RawDragEventType.DragLeave,
                     _target,
-                    default(Point),
+                    default,
                     null,
                     DragDropEffects.None,
                     RawInputModifiers.None
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
index 2d1dad6be0..469bcecfb9 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/ItemsPresenterTests_Virtualization_Simple.cs
@@ -569,7 +569,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
                 var target = CreateTarget(itemCount: 10);
                 var items = (IList<string>)target.Items;
                 target.ApplyTemplate();
-                target.Measure(default(Size));
+                target.Measure(default);
                 target.Arrange(default);
 
                 // Check for issue #591: this should not throw.

From 208b0264c64e25282870c036e02c7794daf173ee Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:54:22 +1100
Subject: [PATCH 084/157] broken GetRequiredService for _useGL

---
 src/Browser/Avalonia.Browser/AvaloniaView.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Browser/Avalonia.Browser/AvaloniaView.cs b/src/Browser/Avalonia.Browser/AvaloniaView.cs
index 153a8c6c1d..294216ee03 100644
--- a/src/Browser/Avalonia.Browser/AvaloniaView.cs
+++ b/src/Browser/Avalonia.Browser/AvaloniaView.cs
@@ -106,7 +106,7 @@ namespace Avalonia.Browser
 
             _dpi = DomHelper.ObserveDpi(OnDpiChanged);
 
-            _useGL = AvaloniaLocator.Current.GetRequiredService<IPlatformGraphics>() != null;
+            _useGL = AvaloniaLocator.Current.GetService<IPlatformGraphics>() != null;
 
             if (_useGL)
             {

From 9ea174ce0af7f1f9f89c0bc5492d74cb177b1f9d Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 10:58:47 +1100
Subject: [PATCH 085/157] Storage/getItem can be null

https://developer.mozilla.org/en-US/docs/Web/API/Storage/getItem
---
 src/Browser/Avalonia.Browser/Interop/StorageHelper.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Browser/Avalonia.Browser/Interop/StorageHelper.cs b/src/Browser/Avalonia.Browser/Interop/StorageHelper.cs
index c44af810d1..e50f8790ef 100644
--- a/src/Browser/Avalonia.Browser/Interop/StorageHelper.cs
+++ b/src/Browser/Avalonia.Browser/Interop/StorageHelper.cs
@@ -45,7 +45,7 @@ internal static partial class StorageHelper
 
     [JSImport("StorageItem.getItems", AvaloniaModule.StorageModuleName)]
     [return: JSMarshalAs<JSType.Promise<JSType.Object>>]
-    public static partial Task<JSObject> GetItems(JSObject item);
+    public static partial Task<JSObject?> GetItems(JSObject item);
 
     [JSImport("StorageItems.itemsArray", AvaloniaModule.StorageModuleName)]
     public static partial JSObject[] ItemsArray(JSObject item);

From d53ce9a0e9e2004d447df81311d862e90c96ec98 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:04:20 +1100
Subject: [PATCH 086/157] Update BrowserStorageProvider.cs

---
 .../Storage/BrowserStorageProvider.cs                | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/Browser/Avalonia.Browser/Storage/BrowserStorageProvider.cs b/src/Browser/Avalonia.Browser/Storage/BrowserStorageProvider.cs
index dc580f0fcb..0bebcb9f63 100644
--- a/src/Browser/Avalonia.Browser/Storage/BrowserStorageProvider.cs
+++ b/src/Browser/Avalonia.Browser/Storage/BrowserStorageProvider.cs
@@ -29,11 +29,11 @@ internal class BrowserStorageProvider : IStorageProvider
         await _lazyModule.Value;
         var startIn = (options.SuggestedStartLocation as JSStorageItem)?.FileHandle;
 
-        var (types, exludeAll) = ConvertFileTypes(options.FileTypeFilter);
+        var (types, excludeAll) = ConvertFileTypes(options.FileTypeFilter);
 
         try
         {
-            using var items = await StorageHelper.OpenFileDialog(startIn, options.AllowMultiple, types, exludeAll);
+            using var items = await StorageHelper.OpenFileDialog(startIn, options.AllowMultiple, types, excludeAll);
             if (items is null)
             {
                 return Array.Empty<IStorageFile>();
@@ -63,11 +63,11 @@ internal class BrowserStorageProvider : IStorageProvider
         await _lazyModule.Value;
         var startIn = (options.SuggestedStartLocation as JSStorageItem)?.FileHandle;
 
-        var (types, exludeAll) = ConvertFileTypes(options.FileTypeChoices);
+        var (types, excludeAll) = ConvertFileTypes(options.FileTypeChoices);
 
         try
         {
-            var item = await StorageHelper.SaveFileDialog(startIn, options.SuggestedFileName, types, exludeAll);
+            var item = await StorageHelper.SaveFileDialog(startIn, options.SuggestedFileName, types, excludeAll);
             return item is not null ? new JSStorageFile(item) : null;
         }
         catch (JSException ex) when (ex.Message.Contains(PickerCancelMessage, StringComparison.Ordinal))
@@ -127,9 +127,9 @@ internal class BrowserStorageProvider : IStorageProvider
             types = null;
         }
 
-        var inlcudeAll = input?.Contains(FilePickerFileTypes.All) == true || types is null;
+        var includeAll = input?.Contains(FilePickerFileTypes.All) == true || types is null;
 
-        return (types, !inlcudeAll);
+        return (types, !includeAll);
     }
 }
 

From 54c96bc89469708dfbf0687d6dc6e2f9bd382464 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:05:31 +1100
Subject: [PATCH 087/157] Update IOSStorageProvider.cs

---
 src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs b/src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs
index 834418437b..5fdb7ecce1 100644
--- a/src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs
+++ b/src/iOS/Avalonia.iOS/Storage/IOSStorageProvider.cs
@@ -34,7 +34,7 @@ internal class IOSStorageProvider : IStorageProvider
         UIDocumentPickerViewController documentPicker;
         if (OperatingSystem.IsIOSVersionAtLeast(14))
         {
-            var allowedUtis = options.FileTypeFilter?.SelectMany(f =>
+            var allowedUtils = options.FileTypeFilter?.SelectMany(f =>
                 {
                     // We check for OS version outside of the lambda, it's safe.
 #pragma warning disable CA1416
@@ -56,18 +56,18 @@ internal class IOSStorageProvider : IStorageProvider
                 UTTypes.Item,
                 UTTypes.Data
             };
-            documentPicker = new UIDocumentPickerViewController(allowedUtis!, false);
+            documentPicker = new UIDocumentPickerViewController(allowedUtils!, false);
         }
         else
         {
-            var allowedUtis = options.FileTypeFilter?.SelectMany(f => f.AppleUniformTypeIdentifiers ?? Array.Empty<string>())
+            var allowedUtils = options.FileTypeFilter?.SelectMany(f => f.AppleUniformTypeIdentifiers ?? Array.Empty<string>())
                 .ToArray() ?? new[]
             {
                 UTTypeLegacy.Content,
                 UTTypeLegacy.Item,
                 "public.data"
             };
-            documentPicker = new UIDocumentPickerViewController(allowedUtis, UIDocumentPickerMode.Open);
+            documentPicker = new UIDocumentPickerViewController(allowedUtils, UIDocumentPickerMode.Open);
         }
 
         using (documentPicker)

From 4b1a5a28b16d19aafa3155d33914a2e4535a3206 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:06:47 +1100
Subject: [PATCH 088/157] OpenFilePickerAsync cant return null

---
 samples/ControlCatalog/ViewModels/ContextPageViewModel.cs | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs b/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
index 4cfb00625e..4a5462a58b 100644
--- a/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
@@ -56,12 +56,9 @@ namespace ControlCatalog.ViewModels
 
             var result = await window.StorageProvider.OpenFilePickerAsync(new Avalonia.Platform.Storage.FilePickerOpenOptions() { AllowMultiple = true });
 
-            if (result != null)
+            foreach (var file in result)
             {
-                foreach (var file in result)
-                {
-                    System.Diagnostics.Debug.WriteLine($"Opened: {file.Name}");
-                }
+                System.Diagnostics.Debug.WriteLine($"Opened: {file.Name}");
             }
         }
 

From 374c0c4e3bd596d7166e3634c1ae0e146f894210 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:08:04 +1100
Subject: [PATCH 089/157] screens in ScreenPage sampel cant be null

---
 samples/ControlCatalog/Pages/ScreenPage.cs | 58 +++++++++++-----------
 1 file changed, 29 insertions(+), 29 deletions(-)

diff --git a/samples/ControlCatalog/Pages/ScreenPage.cs b/samples/ControlCatalog/Pages/ScreenPage.cs
index 6af4cf353e..b5b80fb147 100644
--- a/samples/ControlCatalog/Pages/ScreenPage.cs
+++ b/samples/ControlCatalog/Pages/ScreenPage.cs
@@ -36,44 +36,44 @@ namespace ControlCatalog.Pages
 
             var drawBrush = Brushes.Black;
             Pen p = new Pen(drawBrush);
-            if (screens != null)
-                foreach (Screen screen in screens)
+
+            foreach (Screen screen in screens)
+            {
+                if (screen.Bounds.X / 10f < _leftMost)
                 {
-                    if (screen.Bounds.X / 10f < _leftMost)
-                    {
-                        _leftMost = screen.Bounds.X / 10f;
-                        Dispatcher.UIThread.Post(InvalidateVisual, DispatcherPriority.Background);
-                        return;
-                    }
+                    _leftMost = screen.Bounds.X / 10f;
+                    Dispatcher.UIThread.Post(InvalidateVisual, DispatcherPriority.Background);
+                    return;
+                }
 
-                    Rect boundsRect = new Rect(screen.Bounds.X / 10f + Math.Abs(_leftMost), screen.Bounds.Y / 10f, screen.Bounds.Width / 10f,
-                                      screen.Bounds.Height / 10f);
-                    Rect workingAreaRect = new Rect(screen.WorkingArea.X / 10f + Math.Abs(_leftMost), screen.WorkingArea.Y / 10f, screen.WorkingArea.Width / 10f,
-                                       screen.WorkingArea.Height / 10f);
-                    
-                    context.DrawRectangle(p, boundsRect);
-                    context.DrawRectangle(p, workingAreaRect);
+                Rect boundsRect = new Rect(screen.Bounds.X / 10f + Math.Abs(_leftMost), screen.Bounds.Y / 10f, screen.Bounds.Width / 10f,
+                                  screen.Bounds.Height / 10f);
+                Rect workingAreaRect = new Rect(screen.WorkingArea.X / 10f + Math.Abs(_leftMost), screen.WorkingArea.Y / 10f, screen.WorkingArea.Width / 10f,
+                                   screen.WorkingArea.Height / 10f);
 
+                context.DrawRectangle(p, boundsRect);
+                context.DrawRectangle(p, workingAreaRect);
 
-                    var formattedText = CreateFormattedText($"Bounds: {screen.Bounds.Width}:{screen.Bounds.Height}");
-                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height));
 
-                    formattedText =
-                        CreateFormattedText($"WorkArea: {screen.WorkingArea.Width}:{screen.WorkingArea.Height}");
-                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 20));
+                var formattedText = CreateFormattedText($"Bounds: {screen.Bounds.Width}:{screen.Bounds.Height}");
+                context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height));
 
-                    formattedText = CreateFormattedText($"Scaling: {screen.Scaling * 100}%");
-                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 40));
+                formattedText =
+                    CreateFormattedText($"WorkArea: {screen.WorkingArea.Width}:{screen.WorkingArea.Height}");
+                context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 20));
 
-                    formattedText = CreateFormattedText($"IsPrimary: {screen.IsPrimary}");
+                formattedText = CreateFormattedText($"Scaling: {screen.Scaling * 100}%");
+                context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 40));
 
-                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 60));
+                formattedText = CreateFormattedText($"IsPrimary: {screen.IsPrimary}");
 
-                    formattedText =
-                        CreateFormattedText(
-                            $"Current: {screen.Equals(w.Screens.ScreenFromBounds(new PixelRect(w.Position, PixelSize.FromSize(w.Bounds.Size, scaling))))}");
-                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 80));
-                }
+                context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 60));
+
+                formattedText =
+                    CreateFormattedText(
+                        $"Current: {screen.Equals(w.Screens.ScreenFromBounds(new PixelRect(w.Position, PixelSize.FromSize(w.Bounds.Size, scaling))))}");
+                context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 80));
+            }
 
             context.DrawRectangle(p, new Rect(w.Position.X / 10f + Math.Abs(_leftMost), w.Position.Y / 10f, w.Bounds.Width / 10, w.Bounds.Height / 10));
         }

From 887153b3e829e41f1cd704c3200782ee88ce1076 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Thu, 5 Jan 2023 19:09:06 -0500
Subject: [PATCH 090/157] Restore RaisePropertyChanged

---
 src/Avalonia.Base/AvaloniaObject.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/AvaloniaObject.cs b/src/Avalonia.Base/AvaloniaObject.cs
index a3a732428e..dc94dfba40 100644
--- a/src/Avalonia.Base/AvaloniaObject.cs
+++ b/src/Avalonia.Base/AvaloniaObject.cs
@@ -621,7 +621,7 @@ namespace Avalonia
         /// <param name="oldValue">The old property value.</param>
         /// <param name="newValue">The new property value.</param>
         /// <param name="priority">The priority of the binding that produced the value.</param>
-        private protected void RaisePropertyChanged<T>(
+        protected void RaisePropertyChanged<T>(
             DirectPropertyBase<T> property,
             Optional<T> oldValue,
             BindingValue<T> newValue,

From 1b71714b76938278b744d475eb64b08d9156c187 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:09:22 +1100
Subject: [PATCH 091/157] brush in cataloge sample can be null

---
 samples/ControlCatalog/Pages/PointerCanvas.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/Pages/PointerCanvas.cs b/samples/ControlCatalog/Pages/PointerCanvas.cs
index 7d26da8603..da1ff5442d 100644
--- a/samples/ControlCatalog/Pages/PointerCanvas.cs
+++ b/samples/ControlCatalog/Pages/PointerCanvas.cs
@@ -24,7 +24,7 @@ public class PointerCanvas : Control
     {
         struct CanvasPoint
         {
-            public IBrush Brush;
+            public IBrush? Brush;
             public Point Point;
             public double Radius;
             public double? Pressure;

From 81c06203676899fd45135e9390aeb002f155de61 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:24:35 +1100
Subject: [PATCH 092/157] Update
 src/Avalonia.Controls/Platform/PlatformManager.cs

Co-authored-by: Max Katz <maxkatz6@outlook.com>
---
 src/Avalonia.Controls/Platform/PlatformManager.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Platform/PlatformManager.cs b/src/Avalonia.Controls/Platform/PlatformManager.cs
index b01fc28831..79ace0b329 100644
--- a/src/Avalonia.Controls/Platform/PlatformManager.cs
+++ b/src/Avalonia.Controls/Platform/PlatformManager.cs
@@ -21,7 +21,7 @@ namespace Avalonia.Controls.Platform
         }
 
         public static ITrayIconImpl? CreateTrayIcon() =>
-            s_designerMode ? null : AvaloniaLocator.Current.GetRequiredService<IWindowingPlatform>().CreateTrayIcon();
+            s_designerMode ? null : AvaloniaLocator.Current.GetService<IWindowingPlatform>()?.CreateTrayIcon();
 
 
         public static IWindowImpl CreateWindow()

From cc6f0d1af15cf4a37e16f0ea9469c4171d740f8f Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 11:28:59 +1100
Subject: [PATCH 093/157] should GetLayoutVisibleWindowDiscardAnchor be used?

---
 .../Repeater/ViewportManager.cs                  | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/src/Avalonia.Controls/Repeater/ViewportManager.cs b/src/Avalonia.Controls/Repeater/ViewportManager.cs
index 10e3dd57a0..28d6911350 100644
--- a/src/Avalonia.Controls/Repeater/ViewportManager.cs
+++ b/src/Avalonia.Controls/Repeater/ViewportManager.cs
@@ -124,22 +124,6 @@ namespace Avalonia.Controls
                 }
             }
         }
-        
-        private Rect GetLayoutVisibleWindowDiscardAnchor()
-        {
-            var visibleWindow = _visibleWindow;
-
-            if (HasScroller)
-            {
-                visibleWindow = new Rect(
-                    visibleWindow.X + _layoutExtent.X + _expectedViewportShift.X + _unshiftableShift.X,
-                    visibleWindow.Y + _layoutExtent.Y + _expectedViewportShift.Y + _unshiftableShift.Y,
-                    visibleWindow.Width,
-                    visibleWindow.Height);
-            }
-
-            return visibleWindow;
-        }
 
         public Rect GetLayoutVisibleWindow()
         {

From fd7c89b611f3cb18d92cf06d726689fd00eaf804 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:01:55 -0500
Subject: [PATCH 094/157] Initial API design for the PlatformColorValues

---
 .../Platform/DefaultPlatformSettings.cs       | 24 ++++++++---
 .../Platform/IPlatformSettings.cs             | 15 ++++++-
 .../Platform/PlatformColorValues.cs           | 42 +++++++++++++++++++
 3 files changed, 74 insertions(+), 7 deletions(-)
 create mode 100644 src/Avalonia.Base/Platform/PlatformColorValues.cs

diff --git a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
index d0b27b057f..98f2367819 100644
--- a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
@@ -1,15 +1,15 @@
 using System;
 using Avalonia.Input;
+using Avalonia.Media;
 
 namespace Avalonia.Platform
 {
     /// <summary>
-    /// A default implementation of <see cref="IPlatformSettings"/> for platforms which don't have
-    /// an OS-specific implementation.
+    /// A default implementation of <see cref="IPlatformSettings"/> for platforms.
     /// </summary>
     public class DefaultPlatformSettings : IPlatformSettings
     {
-        public Size GetTapSize(PointerType type)
+        public virtual Size GetTapSize(PointerType type)
         {
             return type switch
             {
@@ -17,7 +17,7 @@ namespace Avalonia.Platform
                 _ => new(4, 4),
             };
         }
-        public Size GetDoubleTapSize(PointerType type)
+        public virtual Size GetDoubleTapSize(PointerType type)
         {
             return type switch
             {
@@ -25,8 +25,20 @@ namespace Avalonia.Platform
                 _ => new(4, 4),
             };
         }
-        public TimeSpan GetDoubleTapTime(PointerType type) => TimeSpan.FromMilliseconds(500);
+        public virtual TimeSpan GetDoubleTapTime(PointerType type) => TimeSpan.FromMilliseconds(500);
 
-        public TimeSpan HoldWaitDuration { get; set; } = TimeSpan.FromMilliseconds(300);
+        public virtual TimeSpan HoldWaitDuration => TimeSpan.FromMilliseconds(300);
+        
+        public virtual PlatformColorValues GetColorValues()
+        {
+            return new PlatformColorValues(PlatformThemeVariant.Light);
+        }
+
+        public event EventHandler<PlatformColorValues>? ColorValuesChanged;
+
+        protected void OnColorValuesChanged(PlatformColorValues colorValues)
+        {
+            ColorValuesChanged?.Invoke(this, colorValues);
+        }
     }
 }
diff --git a/src/Avalonia.Base/Platform/IPlatformSettings.cs b/src/Avalonia.Base/Platform/IPlatformSettings.cs
index 7c4c1420eb..b167cf0edc 100644
--- a/src/Avalonia.Base/Platform/IPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/IPlatformSettings.cs
@@ -28,6 +28,19 @@ namespace Avalonia.Platform
         /// </summary>
         TimeSpan GetDoubleTapTime(PointerType type);
 
-        TimeSpan HoldWaitDuration { get; set; }
+        /// <summary>
+        /// Holding duration between pointer press and when event is fired.
+        /// </summary>
+        TimeSpan HoldWaitDuration { get; }
+        
+        /// <summary>
+        /// Gets current system color values including dark mode and accent colors.
+        /// </summary>
+        PlatformColorValues GetColorValues();
+
+        /// <summary>
+        /// Raises when current system color values are changed. Including changing of a dark mode and accent colors.
+        /// </summary>
+        event EventHandler<PlatformColorValues>? ColorValuesChanged;
     }
 }
diff --git a/src/Avalonia.Base/Platform/PlatformColorValues.cs b/src/Avalonia.Base/Platform/PlatformColorValues.cs
new file mode 100644
index 0000000000..3071cc217f
--- /dev/null
+++ b/src/Avalonia.Base/Platform/PlatformColorValues.cs
@@ -0,0 +1,42 @@
+using Avalonia.Media;
+
+namespace Avalonia.Platform;
+
+/// <summary>
+/// System theme variant or mode.
+/// </summary>
+public enum PlatformThemeVariant
+{
+    Light,
+    Dark
+}
+
+/// <summary>
+/// Information about current system color values, including information about dark mode and accent colors.
+/// </summary>
+/// <param name="ThemeVariant">System theme variant or mode.</param>
+/// <param name="AccentColor1">Primary system accent color.</param>
+/// <param name="AccentColor2">Secondary system accent color. On some platforms can return the same value as AccentColor1.</param>
+/// <param name="AccentColor3">Tertiary system accent color. On some platforms can return the same value as AccentColor1.</param>
+public record struct PlatformColorValues(
+    PlatformThemeVariant ThemeVariant,
+    Color AccentColor1,
+    Color AccentColor2,
+    Color AccentColor3)
+{
+    public PlatformColorValues(
+        PlatformThemeVariant ThemeVariant,
+        Color AccentColor1)
+        : this(ThemeVariant, AccentColor1, AccentColor1, AccentColor1)
+    {
+            
+    }
+        
+    public PlatformColorValues(PlatformThemeVariant ThemeVariant)
+        : this(ThemeVariant, DefaultAccent)
+    {
+
+    }
+        
+    private static Color DefaultAccent => new(255, 0, 120, 215);
+}

From ad4005ef05ba4b4a6fa0679ea0e4132119c12216 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:02:12 -0500
Subject: [PATCH 095/157] Use PlatformColorValues in the control catalog

---
 samples/ControlCatalog/MainView.xaml.cs | 73 ++++++++++++++++++++++++-
 1 file changed, 72 insertions(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/MainView.xaml.cs b/samples/ControlCatalog/MainView.xaml.cs
index f3c1a68e72..ecd9d0bf52 100644
--- a/samples/ControlCatalog/MainView.xaml.cs
+++ b/samples/ControlCatalog/MainView.xaml.cs
@@ -3,9 +3,12 @@ using System.Collections;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
+using Avalonia.LogicalTree;
 using Avalonia.Markup.Xaml;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
+using Avalonia.Platform;
+using Avalonia.Styling;
 using Avalonia.VisualTree;
 using ControlCatalog.Models;
 using ControlCatalog.Pages;
@@ -14,10 +17,14 @@ namespace ControlCatalog
 {
     public class MainView : UserControl
     {
+        private readonly IPlatformSettings _platformSettings;
+
         public MainView()
         {
             AvaloniaXamlLoader.Load(this);
-
+            _platformSettings = AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>();
+            PlatformSettingsOnColorValuesChanged(_platformSettings, _platformSettings.GetColorValues());
+            
             var sideBar = this.Get<TabControl>("Sidebar");
 
             if (Application.Current?.ApplicationLifetime is IClassicDesktopStyleApplicationLifetime)
@@ -37,6 +44,15 @@ namespace ControlCatalog
                 if (themes.SelectedItem is CatalogTheme theme)
                 {
                     App.SetThemeVariant(theme);
+                    
+                    ((TopLevel?)this.GetVisualRoot())?.PlatformImpl?.SetFrameThemeVariant(theme switch
+                    {
+                        CatalogTheme.FluentLight => PlatformThemeVariant.Light,
+                        CatalogTheme.FluentDark => PlatformThemeVariant.Dark,
+                        CatalogTheme.SimpleLight => PlatformThemeVariant.Light,
+                        CatalogTheme.SimpleDark => PlatformThemeVariant.Dark,
+                        _ => throw new ArgumentOutOfRangeException()
+                    });
                 }
             };
 
@@ -89,6 +105,61 @@ namespace ControlCatalog
             var decorations = this.Get<ComboBox>("Decorations");
             if (VisualRoot is Window window)
                 decorations.SelectedIndex = (int)window.SystemDecorations;
+            
+            _platformSettings.ColorValuesChanged += PlatformSettingsOnColorValuesChanged;
+        }
+
+        protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromLogicalTree(e);
+            
+            _platformSettings.ColorValuesChanged -= PlatformSettingsOnColorValuesChanged;
+        }
+
+        private void PlatformSettingsOnColorValuesChanged(object? sender, PlatformColorValues e)
+        {
+            var themes = this.Get<ComboBox>("Themes");
+            var currentTheme = (CatalogTheme?)themes.SelectedItem ?? CatalogTheme.FluentLight;
+            var newTheme = (currentTheme, e.ThemeVariant) switch
+            {
+                (CatalogTheme.FluentDark, PlatformThemeVariant.Light) => CatalogTheme.FluentLight,
+                (CatalogTheme.FluentLight, PlatformThemeVariant.Dark) => CatalogTheme.FluentDark,
+                (CatalogTheme.SimpleDark, PlatformThemeVariant.Light) => CatalogTheme.SimpleLight,
+                (CatalogTheme.SimpleLight, PlatformThemeVariant.Dark) => CatalogTheme.SimpleDark,
+                _ => currentTheme
+            };
+            themes.SelectedItem = newTheme;
+
+            Application.Current!.Resources["SystemAccentColor"] = e.AccentColor1;
+            Application.Current.Resources["SystemAccentColorDark1"] = ChangeColorLuminosity(e.AccentColor1, -0.3);
+            Application.Current.Resources["SystemAccentColorDark2"] = ChangeColorLuminosity(e.AccentColor1, -0.5);
+            Application.Current.Resources["SystemAccentColorDark3"] = ChangeColorLuminosity(e.AccentColor1, -0.7);
+            Application.Current.Resources["SystemAccentColorLight1"] = ChangeColorLuminosity(e.AccentColor1, -0.3);
+            Application.Current.Resources["SystemAccentColorLight2"] = ChangeColorLuminosity(e.AccentColor1, -0.5);
+            Application.Current.Resources["SystemAccentColorLight3"] = ChangeColorLuminosity(e.AccentColor1, -0.7);
+
+            static Color ChangeColorLuminosity(Color color, double luminosityFactor)
+            {
+                var red = (double)color.R;
+                var green = (double)color.G;
+                var blue = (double)color.B;
+
+                if (luminosityFactor < 0)
+                {
+                    luminosityFactor = 1 + luminosityFactor;
+                    red *= luminosityFactor;
+                    green *= luminosityFactor;
+                    blue *= luminosityFactor;
+                }
+                else if (luminosityFactor >= 0)
+                {
+                    red = (255 - red) * luminosityFactor + red;
+                    green = (255 - green) * luminosityFactor + green;
+                    blue = (255 - blue) * luminosityFactor + blue;
+                }
+
+                return new Color(color.A, (byte)red, (byte)green, (byte)blue);
+            }
         }
     }
 }

From 36f93ae7bc71fd2f54cc36b78706546e0d9ca501 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:14:16 -0500
Subject: [PATCH 096/157] Update tests and designer

---
 .../Offscreen/OffscreenTopLevelImpl.cs        |    2 +
 .../Platform/ITopLevelImpl.cs                 |    6 +
 src/Avalonia.DesignerSupport/Remote/Stubs.cs  |    4 +-
 src/Avalonia.Headless/HeadlessWindowImpl.cs   |    5 +
 .../Rendering/CompositorTestsBase.cs          |    2 +
 .../HtmlTransport/webapp/package-lock.json    | 2665 ++++++++++++++++-
 6 files changed, 2682 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs b/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs
index 4a227a0c00..64f96b6987 100644
--- a/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs
+++ b/src/Avalonia.Controls/Embedding/Offscreen/OffscreenTopLevelImpl.cs
@@ -58,6 +58,8 @@ namespace Avalonia.Controls.Embedding.Offscreen
 
         public Action<WindowTransparencyLevel>? TransparencyLevelChanged { get; set; }
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         /// <inheritdoc/>
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
 
diff --git a/src/Avalonia.Controls/Platform/ITopLevelImpl.cs b/src/Avalonia.Controls/Platform/ITopLevelImpl.cs
index 6bb94c6070..bf74e0f8f4 100644
--- a/src/Avalonia.Controls/Platform/ITopLevelImpl.cs
+++ b/src/Avalonia.Controls/Platform/ITopLevelImpl.cs
@@ -163,6 +163,12 @@ namespace Avalonia.Platform
         /// </summary>
         WindowTransparencyLevel TransparencyLevel { get; }
 
+        /// <summary>
+        /// Sets the <see cref="PlatformThemeVariant"/> on the frame if it should be dark or light.
+        /// Also applies for the mobile status bar.
+        /// </summary>
+        void SetFrameThemeVariant(PlatformThemeVariant themeVariant);
+        
         /// <summary>
         /// Gets the <see cref="AcrylicPlatformCompensationLevels"/> for the platform.        
         /// </summary>
diff --git a/src/Avalonia.DesignerSupport/Remote/Stubs.cs b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
index 94679e8ade..4bb98c0267 100644
--- a/src/Avalonia.DesignerSupport/Remote/Stubs.cs
+++ b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
@@ -182,7 +182,9 @@ namespace Avalonia.DesignerSupport.Remote
         public bool IsClientAreaExtendedToDecorations { get; }
 
         public bool NeedsManagedDecorations => false;
-        
+
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
     }
 
diff --git a/src/Avalonia.Headless/HeadlessWindowImpl.cs b/src/Avalonia.Headless/HeadlessWindowImpl.cs
index 8eafce208b..195328cd65 100644
--- a/src/Avalonia.Headless/HeadlessWindowImpl.cs
+++ b/src/Avalonia.Headless/HeadlessWindowImpl.cs
@@ -345,5 +345,10 @@ namespace Avalonia.Headless
         {
             
         }
+        
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        {
+            
+        }
     }
 }
diff --git a/tests/Avalonia.Base.UnitTests/Rendering/CompositorTestsBase.cs b/tests/Avalonia.Base.UnitTests/Rendering/CompositorTestsBase.cs
index 7f4e160000..12db249f04 100644
--- a/tests/Avalonia.Base.UnitTests/Rendering/CompositorTestsBase.cs
+++ b/tests/Avalonia.Base.UnitTests/Rendering/CompositorTestsBase.cs
@@ -104,6 +104,8 @@ public class CompositorTestsBase
         }
 
         public WindowTransparencyLevel TransparencyLevel { get; }
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; }
     }
 
diff --git a/tests/Avalonia.DesignerSupport.Tests/Remote/HtmlTransport/webapp/package-lock.json b/tests/Avalonia.DesignerSupport.Tests/Remote/HtmlTransport/webapp/package-lock.json
index 0c0857b680..0b92805712 100644
--- a/tests/Avalonia.DesignerSupport.Tests/Remote/HtmlTransport/webapp/package-lock.json
+++ b/tests/Avalonia.DesignerSupport.Tests/Remote/HtmlTransport/webapp/package-lock.json
@@ -1,8 +1,2671 @@
 {
   "name": "simple-test",
   "version": "1.0.0",
-  "lockfileVersion": 1,
+  "lockfileVersion": 2,
   "requires": true,
+  "packages": {
+    "": {
+      "name": "simple-test",
+      "version": "1.0.0",
+      "license": "MIT",
+      "devDependencies": {
+        "@types/chai": "4.2.12",
+        "@types/mocha": "8.0.3",
+        "@types/react": "^16.3.14",
+        "chai": "^4.2.0",
+        "mocha": "^10.2.0",
+        "moq.ts": "^6.4.0",
+        "nyc": "^15.1.0",
+        "react": "^16.3.2",
+        "ts-node": "^9.0.0",
+        "typescript": "^4.0.2"
+      }
+    },
+    "node_modules/@babel/code-frame": {
+      "version": "7.10.4",
+      "resolved": "https://registry.npmjs.org/@babel/code-frame/-/code-frame-7.10.4.tgz",
+      "integrity": "sha512-vG6SvB6oYEhvgisZNFRmRCUkLz11c7rp+tbNTynGqc6mS1d5ATd/sGyV6W0KZZnXRKMTzZDRgQT3Ou9jhpAfUg==",
+      "dev": true,
+      "dependencies": {
+        "@babel/highlight": "^7.10.4"
+      }
+    },
+    "node_modules/@babel/core": {
+      "version": "7.11.6",
+      "resolved": "https://registry.npmjs.org/@babel/core/-/core-7.11.6.tgz",
+      "integrity": "sha512-Wpcv03AGnmkgm6uS6k8iwhIwTrcP0m17TL1n1sy7qD0qelDu4XNeW0dN0mHfa+Gei211yDaLoEe/VlbXQzM4Bg==",
+      "dev": true,
+      "dependencies": {
+        "@babel/code-frame": "^7.10.4",
+        "@babel/generator": "^7.11.6",
+        "@babel/helper-module-transforms": "^7.11.0",
+        "@babel/helpers": "^7.10.4",
+        "@babel/parser": "^7.11.5",
+        "@babel/template": "^7.10.4",
+        "@babel/traverse": "^7.11.5",
+        "@babel/types": "^7.11.5",
+        "convert-source-map": "^1.7.0",
+        "debug": "^4.1.0",
+        "gensync": "^1.0.0-beta.1",
+        "json5": "^2.1.2",
+        "lodash": "^4.17.19",
+        "resolve": "^1.3.2",
+        "semver": "^5.4.1",
+        "source-map": "^0.5.0"
+      },
+      "engines": {
+        "node": ">=6.9.0"
+      },
+      "funding": {
+        "type": "opencollective",
+        "url": "https://opencollective.com/babel"
+      }
+    },
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From 4105bb09c95491c510b1c0e050480d00e3daf87f Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:14:45 -0500
Subject: [PATCH 097/157] Windows implementation

---
 .../Wpf/WpfTopLevelImpl.cs                    |  2 +
 src/Windows/Avalonia.Win32/Win32Platform.cs   | 29 ++-------
 .../Avalonia.Win32/Win32PlatformSettings.cs   | 62 +++++++++++++++++++
 .../Avalonia.Win32/WinRT/WinRTColor.cs        |  3 +
 src/Windows/Avalonia.Win32/WinRT/winrt.idl    | 20 ++++++
 .../Avalonia.Win32/WindowImpl.AppWndProc.cs   |  8 +++
 src/Windows/Avalonia.Win32/WindowImpl.cs      | 13 ++++
 7 files changed, 113 insertions(+), 24 deletions(-)
 create mode 100644 src/Windows/Avalonia.Win32/Win32PlatformSettings.cs

diff --git a/src/Windows/Avalonia.Win32.Interop/Wpf/WpfTopLevelImpl.cs b/src/Windows/Avalonia.Win32.Interop/Wpf/WpfTopLevelImpl.cs
index 16a20c855f..76fc4fa21d 100644
--- a/src/Windows/Avalonia.Win32.Interop/Wpf/WpfTopLevelImpl.cs
+++ b/src/Windows/Avalonia.Win32.Interop/Wpf/WpfTopLevelImpl.cs
@@ -258,6 +258,8 @@ namespace Avalonia.Win32.Interop.Wpf
 
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
     }
 }
diff --git a/src/Windows/Avalonia.Win32/Win32Platform.cs b/src/Windows/Avalonia.Win32/Win32Platform.cs
index 585a9cdf19..c0a0ce4da0 100644
--- a/src/Windows/Avalonia.Win32/Win32Platform.cs
+++ b/src/Windows/Avalonia.Win32/Win32Platform.cs
@@ -11,6 +11,7 @@ using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Platform;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
+using Avalonia.Media;
 using Avalonia.OpenGL;
 using Avalonia.Platform;
 using Avalonia.Rendering;
@@ -19,6 +20,7 @@ using Avalonia.Threading;
 using Avalonia.Utilities;
 using Avalonia.Win32.Input;
 using Avalonia.Win32.Interop;
+using Avalonia.Win32.WinRT;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
 
 namespace Avalonia
@@ -111,7 +113,7 @@ namespace Avalonia
 
 namespace Avalonia.Win32
 {
-    public class Win32Platform : IPlatformThreadingInterface, IPlatformSettings, IWindowingPlatform, IPlatformIconLoader, IPlatformLifetimeEventsImpl
+    public class Win32Platform : IPlatformThreadingInterface, IWindowingPlatform, IPlatformIconLoader, IPlatformLifetimeEventsImpl
     {
         private static readonly Win32Platform s_instance = new Win32Platform();
         private static Thread _uiThread;
@@ -126,6 +128,7 @@ namespace Avalonia.Win32
         }
 
         internal static Win32Platform Instance => s_instance;
+        internal static IPlatformSettings PlatformSettings => AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>();
 
         internal IntPtr Handle => _hwnd;
 
@@ -153,7 +156,7 @@ namespace Avalonia.Win32
                 .Bind<IClipboard>().ToSingleton<ClipboardImpl>()
                 .Bind<ICursorFactory>().ToConstant(CursorFactory.Instance)
                 .Bind<IKeyboardDevice>().ToConstant(WindowsKeyboardDevice.Instance)
-                .Bind<IPlatformSettings>().ToConstant(s_instance)
+                .Bind<IPlatformSettings>().ToSingleton<Win32PlatformSettings>()
                 .Bind<IPlatformThreadingInterface>().ToConstant(s_instance)
                 .Bind<IRenderLoop>().ToConstant(new RenderLoop())
                 .Bind<IRenderTimer>().ToConstant(new DefaultRenderTimer(60))
@@ -258,8 +261,6 @@ namespace Avalonia.Win32
 
         public bool CurrentThreadIsLoopThread => _uiThread == Thread.CurrentThread;
 
-        public TimeSpan HoldWaitDuration { get; set; } = TimeSpan.FromMilliseconds(300);
-
         public event Action<DispatcherPriority?> Signaled;
 
         public event EventHandler<ShutdownRequestedEventArgs> ShutdownRequested;
@@ -403,25 +404,5 @@ namespace Avalonia.Win32
 
             SetProcessDPIAware();
         }
-
-        Size IPlatformSettings.GetTapSize(PointerType type)
-        {
-            return type switch
-            {
-                PointerType.Touch => new(10, 10),
-                _ => new(GetSystemMetrics(SystemMetric.SM_CXDRAG), GetSystemMetrics(SystemMetric.SM_CYDRAG)),
-            };
-        }
-
-        Size IPlatformSettings.GetDoubleTapSize(PointerType type)
-        {
-            return type switch
-            {
-                PointerType.Touch => new(16, 16),
-                _ => new(GetSystemMetrics(SystemMetric.SM_CXDOUBLECLK), GetSystemMetrics(SystemMetric.SM_CYDOUBLECLK)),
-            };
-        }
-
-        TimeSpan IPlatformSettings.GetDoubleTapTime(PointerType type) => TimeSpan.FromMilliseconds(GetDoubleClickTime());
     }
 }
diff --git a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
new file mode 100644
index 0000000000..73ac5bf5a9
--- /dev/null
+++ b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
@@ -0,0 +1,62 @@
+using System;
+using Avalonia.Input;
+using Avalonia.Platform;
+using Avalonia.Win32.Interop;
+using Avalonia.Win32.WinRT;
+using static Avalonia.Win32.Interop.UnmanagedMethods;
+
+namespace Avalonia.Win32;
+
+internal class Win32PlatformSettings : DefaultPlatformSettings
+{
+    private PlatformColorValues _lastColorValues;
+
+    public override Size GetTapSize(PointerType type)
+    {
+        return type switch
+        {
+            PointerType.Touch => new(10, 10),
+            _ => new(GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CXDRAG), GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDRAG)),
+        };
+    }
+
+    public override Size GetDoubleTapSize(PointerType type)
+    {
+        return type switch
+        {
+            PointerType.Touch => new(16, 16),
+            _ => new(GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CXDOUBLECLK), GetSystemMetrics(UnmanagedMethods.SystemMetric.SM_CYDOUBLECLK)),
+        };
+    }
+
+    public override TimeSpan GetDoubleTapTime(PointerType type) => TimeSpan.FromMilliseconds(GetDoubleClickTime());
+    
+    public override PlatformColorValues GetColorValues()
+    {
+        if (Win32Platform.WindowsVersion.Major < 10)
+        {
+            return base.GetColorValues();
+        }
+
+        var settings = NativeWinRTMethods.CreateInstance<IUISettings3>("Windows.UI.ViewManagement.UISettings");
+        var accent = settings.GetColorValue(UIColorType.Accent).ToAvalonia();
+        var background = settings.GetColorValue(UIColorType.Background).ToAvalonia();
+
+        return _lastColorValues = new PlatformColorValues(
+            background.R + background.G + background.B < (255 * 3 - background.R - background.G - background.B)
+                ? PlatformThemeVariant.Dark
+                : PlatformThemeVariant.Light,
+            accent, accent, accent);
+    }
+    
+    internal void OnColorValuesChanged(IntPtr handle)
+    {
+        var oldColorValues = _lastColorValues;
+        var colorValues = GetColorValues();
+
+        if (oldColorValues != colorValues)
+        {
+            OnColorValuesChanged(colorValues);
+        }
+    }
+}
diff --git a/src/Windows/Avalonia.Win32/WinRT/WinRTColor.cs b/src/Windows/Avalonia.Win32/WinRT/WinRTColor.cs
index 35f0737d5f..90b2022054 100644
--- a/src/Windows/Avalonia.Win32/WinRT/WinRTColor.cs
+++ b/src/Windows/Avalonia.Win32/WinRT/WinRTColor.cs
@@ -1,4 +1,5 @@
 using System.Runtime.InteropServices;
+using Avalonia.Media;
 
 namespace Avalonia.Win32.WinRT
 {
@@ -14,5 +15,7 @@ namespace Avalonia.Win32.WinRT
         {
             A = a, R = r, G = g, B = b
         };
+
+        public Color ToAvalonia() => new(A, R, G, B);
     }
 }
diff --git a/src/Windows/Avalonia.Win32/WinRT/winrt.idl b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
index ffb98fafc8..8dee275d50 100644
--- a/src/Windows/Avalonia.Win32/WinRT/winrt.idl
+++ b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
@@ -844,3 +844,23 @@ interface ICompositor6 : IInspectable
     [overload("CreateGeometricClip")] HRESULT CreateGeometricClip([out] [retval] ICompositionGeometricClip** result);
     [overload("CreateGeometricClip")] HRESULT CreateGeometricClipWithGeometry([in] ICompositionGeometry* geometry, [out] [retval] ICompositionGeometricClip** result); 
 }
+
+enum UIColorType
+{
+    Background = 0,
+    Foreground = 1,
+    AccentDark3 = 2,
+    AccentDark2 = 3,
+    AccentDark1 = 4,
+    Accent = 5,
+    AccentLight1 = 6,
+    AccentLight2 = 7,
+    AccentLight3 = 8,
+    Complement = 9
+}
+
+[uuid(03021BE4-5254-4781-8194-5168F7D06D7B)]
+interface IUISettings3 : IInspectable
+{
+    HRESULT GetColorValue([in] UIColorType desiredColor, [out][retval] Color* value);
+}
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
index 8c362b0c29..af634fd760 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
@@ -732,6 +732,14 @@ namespace Avalonia.Win32
                         var node = AutomationNode.GetOrCreate(peer);
                         return UiaCoreProviderApi.UiaReturnRawElementProvider(_hwnd, wParam, lParam, node);
                     }
+                    break;
+                case WindowsMessage.WM_SETTINGCHANGE:
+                    if (Marshal.PtrToStringAuto(lParam) == "ImmersiveColorSet"
+                        && Win32Platform.PlatformSettings is Win32PlatformSettings win32PlatformSettings)
+                    {
+                        win32PlatformSettings.OnColorValuesChanged(_hwnd);
+                    }
+
                     break;
             }
 
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index dbcc31c5f5..a7741477e5 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -805,6 +805,19 @@ namespace Avalonia.Win32
             _topmost = value;
         }
 
+        public unsafe void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        {
+            if (Win32Platform.WindowsVersion.Build >= 22000)
+            {
+                var pvUseBackdropBrush = themeVariant == PlatformThemeVariant.Dark ? 1 : 0;
+                DwmSetWindowAttribute(
+                    _hwnd,
+                    (int)DwmWindowAttribute.DWMWA_USE_IMMERSIVE_DARK_MODE,
+                    &pvUseBackdropBrush,
+                    sizeof(int));
+            }
+        }
+        
         protected virtual IntPtr CreateWindowOverride(ushort atom)
         {
             return CreateWindowEx(

From d76bdd7807f9612793708ac50033b2e806d53cd1 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:15:00 -0500
Subject: [PATCH 098/157] FreeDesktop/x11 implementation

---
 .../DBusPlatformSettings.cs                   | 74 +++++++++++++++++++
 src/Avalonia.FreeDesktop/DBusSettings.cs      | 16 ++++
 src/Avalonia.X11/X11Platform.cs               |  2 +-
 src/Avalonia.X11/X11Window.cs                 |  2 +
 .../FramebufferToplevelImpl.cs                |  2 +
 5 files changed, 95 insertions(+), 1 deletion(-)
 create mode 100644 src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
 create mode 100644 src/Avalonia.FreeDesktop/DBusSettings.cs

diff --git a/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs b/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
new file mode 100644
index 0000000000..82b4a72e74
--- /dev/null
+++ b/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
@@ -0,0 +1,74 @@
+using System;
+using System.Threading.Tasks;
+using Avalonia.Logging;
+using Avalonia.Platform;
+
+namespace Avalonia.FreeDesktop;
+
+internal class DBusPlatformSettings : DefaultPlatformSettings
+{
+    private readonly IDBusSettings? _settings;
+    private PlatformColorValues? _lastColorValues;
+
+    public DBusPlatformSettings()
+    {
+        _settings = DBusHelper.TryInitialize()?
+            .CreateProxy<IDBusSettings>("org.freedesktop.portal.Desktop", "/org/freedesktop/portal/desktop");
+
+        if (_settings is not null)
+        {
+            _ = _settings.WatchSettingChangedAsync(SettingsChangedHandler);
+
+            _ = TryGetInitialValue();
+        }
+    }
+
+    public override PlatformColorValues GetColorValues()
+    {
+        return _lastColorValues ?? base.GetColorValues();
+    }
+
+    private async Task TryGetInitialValue()
+    {
+        var colorSchemeTask = _settings!.ReadAsync("org.freedesktop.appearance", "color-scheme");
+        if (colorSchemeTask.Status == TaskStatus.RanToCompletion)
+        {
+            _lastColorValues = GetColorValuesFromSetting(colorSchemeTask.Result);
+        }
+        else
+        {
+            try
+            {
+                var value = await colorSchemeTask;
+                _lastColorValues = GetColorValuesFromSetting(value);
+                OnColorValuesChanged(_lastColorValues.Value);
+            }
+            catch (Exception ex)
+            {
+                _lastColorValues = base.GetColorValues();
+                Logger.TryGet(LogEventLevel.Error, LogArea.FreeDesktopPlatform)?.Log(this, "Unable to get setting value", ex);
+            }
+        }
+    }
+    
+    private void SettingsChangedHandler((string @namespace, string key, object value) tuple)
+    {
+        if (tuple.@namespace == "org.freedesktop.appearance"
+            && tuple.key == "color-scheme")
+        {
+            /*
+            <member>0: No preference</member>
+            <member>1: Prefer dark appearance</member>
+            <member>2: Prefer light appearance</member>
+            */
+            _lastColorValues = GetColorValuesFromSetting(tuple.value);
+            OnColorValuesChanged(_lastColorValues.Value);
+        }
+    }
+    
+    private static PlatformColorValues GetColorValuesFromSetting(object value)
+    {
+        var isDark = value?.ToString() == "1";
+        return new PlatformColorValues(isDark ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light);
+    }
+}
diff --git a/src/Avalonia.FreeDesktop/DBusSettings.cs b/src/Avalonia.FreeDesktop/DBusSettings.cs
new file mode 100644
index 0000000000..05911981c7
--- /dev/null
+++ b/src/Avalonia.FreeDesktop/DBusSettings.cs
@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Tmds.DBus;
+
+namespace Avalonia.FreeDesktop;
+
+[DBusInterface("org.freedesktop.portal.Settings")]
+internal interface IDBusSettings : IDBusObject
+{
+    Task<(string @namespace, IDictionary<string, object>)> ReadAllAsync(string[] namespaces);
+
+    Task<object> ReadAsync(string @namespace, string key);
+
+    Task<IDisposable> WatchSettingChangedAsync(Action<(string @namespace, string key, object value)> handler, Action<Exception>? onError = null);
+}
diff --git a/src/Avalonia.X11/X11Platform.cs b/src/Avalonia.X11/X11Platform.cs
index 9692e0a384..7820f8a3c2 100644
--- a/src/Avalonia.X11/X11Platform.cs
+++ b/src/Avalonia.X11/X11Platform.cs
@@ -80,7 +80,7 @@ namespace Avalonia.X11
                 .Bind<IKeyboardDevice>().ToFunc(() => KeyboardDevice)
                 .Bind<ICursorFactory>().ToConstant(new X11CursorFactory(Display))
                 .Bind<IClipboard>().ToConstant(new X11Clipboard(this))
-                .Bind<IPlatformSettings>().ToSingleton<DefaultPlatformSettings>()
+                .Bind<IPlatformSettings>().ToSingleton<DBusPlatformSettings>()
                 .Bind<IPlatformIconLoader>().ToConstant(new X11IconLoader())
                 .Bind<IMountedVolumeInfoProvider>().ToConstant(new LinuxMountedVolumeInfoProvider())
                 .Bind<IPlatformLifetimeEventsImpl>().ToConstant(new X11PlatformLifetimeEvents(this));
diff --git a/src/Avalonia.X11/X11Window.cs b/src/Avalonia.X11/X11Window.cs
index 810a806c8a..4b0e8473cc 100644
--- a/src/Avalonia.X11/X11Window.cs
+++ b/src/Avalonia.X11/X11Window.cs
@@ -1225,6 +1225,8 @@ namespace Avalonia.X11
         public WindowTransparencyLevel TransparencyLevel =>
             _transparencyHelper?.CurrentLevel ?? WindowTransparencyLevel.None;
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 0.8, 0.8);
 
         public bool NeedsManagedDecorations => false;
diff --git a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
index ac54365f51..1c2fad56a6 100644
--- a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
+++ b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
@@ -83,6 +83,8 @@ namespace Avalonia.LinuxFramebuffer
 
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant) { }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 1, 1);
     }
 }

From a4bffbf660595ea70e3073401fd3df43746fd73f Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:15:18 -0500
Subject: [PATCH 099/157] iOS and Android implementations

---
 .../Avalonia.Android/AndroidPlatform.cs       |  2 +-
 src/Android/Avalonia.Android/AvaloniaView.cs  | 16 ++++
 .../Platform/AndroidPlatformSettings.cs       | 73 +++++++++++++++++++
 .../Platform/SkiaPlatform/TopLevelImpl.cs     |  6 ++
 src/iOS/Avalonia.iOS/AvaloniaView.cs          | 27 ++++++-
 .../Avalonia.iOS/AvaloniaViewController.cs    |  6 ++
 src/iOS/Avalonia.iOS/Platform.cs              |  2 +-
 src/iOS/Avalonia.iOS/PlatformSettings.cs      | 34 +++++++++
 8 files changed, 163 insertions(+), 3 deletions(-)
 create mode 100644 src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
 create mode 100644 src/iOS/Avalonia.iOS/AvaloniaViewController.cs
 create mode 100644 src/iOS/Avalonia.iOS/PlatformSettings.cs

diff --git a/src/Android/Avalonia.Android/AndroidPlatform.cs b/src/Android/Avalonia.Android/AndroidPlatform.cs
index 01b48ffd89..c73fd92423 100644
--- a/src/Android/Avalonia.Android/AndroidPlatform.cs
+++ b/src/Android/Avalonia.Android/AndroidPlatform.cs
@@ -43,7 +43,7 @@ namespace Avalonia.Android
                 .Bind<ICursorFactory>().ToTransient<CursorFactory>()
                 .Bind<IWindowingPlatform>().ToConstant(new WindowingPlatformStub())
                 .Bind<IKeyboardDevice>().ToSingleton<AndroidKeyboardDevice>()
-                .Bind<IPlatformSettings>().ToSingleton<DefaultPlatformSettings>()
+                .Bind<IPlatformSettings>().ToSingleton<AndroidPlatformSettings>()
                 .Bind<IPlatformThreadingInterface>().ToConstant(new AndroidThreadingInterface())
                 .Bind<IPlatformIconLoader>().ToSingleton<PlatformIconLoaderStub>()
                 .Bind<IRenderTimer>().ToConstant(new ChoreographerTimer())
diff --git a/src/Android/Avalonia.Android/AvaloniaView.cs b/src/Android/Avalonia.Android/AvaloniaView.cs
index f7e32f99db..2a345a857c 100644
--- a/src/Android/Avalonia.Android/AvaloniaView.cs
+++ b/src/Android/Avalonia.Android/AvaloniaView.cs
@@ -1,11 +1,14 @@
 using System;
 using Android.Content;
+using Android.Content.Res;
 using Android.Runtime;
 using Android.Views;
 using Android.Widget;
+using Avalonia.Android.Platform;
 using Avalonia.Android.Platform.SkiaPlatform;
 using Avalonia.Controls;
 using Avalonia.Controls.Embedding;
+using Avalonia.Platform;
 using Avalonia.Rendering;
 
 namespace Avalonia.Android
@@ -26,6 +29,7 @@ namespace Avalonia.Android
             _root.Prepare();
 
             this.SetBackgroundColor(global::Android.Graphics.Color.Transparent);
+            OnConfigurationChanged();
         }
 
         internal TopLevelImpl TopLevelImpl => _view;
@@ -70,6 +74,18 @@ namespace Avalonia.Android
                 _timerSubscription?.Dispose();
             }
         }
+        
+        protected override void OnConfigurationChanged(Configuration newConfig)
+        {
+            base.OnConfigurationChanged(newConfig);
+            OnConfigurationChanged();
+        }
+
+        private void OnConfigurationChanged()
+        {
+            var settings = AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>() as AndroidPlatformSettings;
+            settings?.OnViewConfigurationChanged(Context);
+        }
 
         class ViewImpl : TopLevelImpl
         {
diff --git a/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs b/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
new file mode 100644
index 0000000000..f560dea3ce
--- /dev/null
+++ b/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
@@ -0,0 +1,73 @@
+using System;
+using Android;
+using Android.Content;
+using Android.Content.Res;
+using Android.Graphics;
+using AndroidX.Core.Content.Resources;
+using Avalonia.Media;
+using Avalonia.Platform;
+using Color = Avalonia.Media.Color;
+
+namespace Avalonia.Android.Platform;
+
+// TODO: ideally should be created per view/activity.
+internal class AndroidPlatformSettings : DefaultPlatformSettings
+{
+    private PlatformColorValues _latestValues;
+
+    public AndroidPlatformSettings()
+    {
+        _latestValues = base.GetColorValues();
+    }
+
+    public override PlatformColorValues GetColorValues()
+    {
+        return _latestValues;
+    }
+
+    internal void OnViewConfigurationChanged(Context context)
+    {
+        if (context.Resources?.Configuration is null)
+        {
+            return;
+        }
+
+        var systemTheme = (context.Resources.Configuration.UiMode & UiMode.NightMask) switch
+        {
+            UiMode.NightYes => PlatformThemeVariant.Dark,
+            UiMode.NightNo => PlatformThemeVariant.Light,
+            _ => throw new ArgumentOutOfRangeException()
+        };
+
+        if (OperatingSystem.IsAndroidVersionAtLeast(31))
+        {
+            // See https://developer.android.com/reference/android/R.color
+            var accent1 = context.Resources.GetColor(17170494, context.Theme); // Resource.Color.SystemAccent1500
+            var accent2 = context.Resources.GetColor(17170507, context.Theme); // Resource.Color.SystemAccent2500
+            var accent3 = context.Resources.GetColor(17170520, context.Theme); // Resource.Color.SystemAccent3500
+
+            _latestValues = new PlatformColorValues(
+                systemTheme,
+                new Color(accent1.A, accent1.R, accent1.G, accent1.B),
+                new Color(accent2.A, accent2.R, accent2.G, accent2.B),
+                new Color(accent3.A, accent3.R, accent3.G, accent3.B));
+        }
+        else if (OperatingSystem.IsAndroidVersionAtLeast(23))
+        {
+            // See https://developer.android.com/reference/android/R.attr
+            var array = context.Theme.ObtainStyledAttributes(new[] { 16843829 }); // Resource.Attribute.ColorAccent
+            var accent = array.GetColor(0, 0);
+
+            _latestValues = new PlatformColorValues(
+                systemTheme,
+                new Color(accent.A, accent.R, accent.G, accent.B));
+            array.Recycle();
+        }
+        else
+        {
+            _latestValues = _latestValues with { ThemeVariant = systemTheme };
+        }
+
+        OnColorValuesChanged(_latestValues);
+    }
+}
diff --git a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
index 1aac567dda..1f997af26d 100644
--- a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
+++ b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
@@ -26,6 +26,7 @@ using Avalonia.Rendering.Composition;
 using Java.Lang;
 using Math = System.Math;
 using AndroidRect = Android.Graphics.Rect;
+using Window = Android.Views.Window;
 using Android.Graphics.Drawables;
 
 namespace Avalonia.Android.Platform.SkiaPlatform
@@ -286,6 +287,11 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        {
+            // TODO adjust status bar depending on full screen mode.
+        }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels => new AcrylicPlatformCompensationLevels(1, 1, 1);
 
         IntPtr EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo.Handle => ((IPlatformHandle)_view).Handle;
diff --git a/src/iOS/Avalonia.iOS/AvaloniaView.cs b/src/iOS/Avalonia.iOS/AvaloniaView.cs
index 48358c745f..6d36ca7814 100644
--- a/src/iOS/Avalonia.iOS/AvaloniaView.cs
+++ b/src/iOS/Avalonia.iOS/AvaloniaView.cs
@@ -52,6 +52,14 @@ namespace Avalonia.iOS
 
         public override bool CanResignFirstResponder => true;
 
+        public override void TraitCollectionDidChange(UITraitCollection previousTraitCollection)
+        {
+            base.TraitCollectionDidChange(previousTraitCollection);
+            
+            var settings = AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>() as PlatformSettings;
+            settings?.TraitCollectionDidChange();
+        }
+
         internal class TopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost,
             ITopLevelImplWithStorageProvider
         {
@@ -120,7 +128,24 @@ namespace Avalonia.iOS
             // legacy no-op
             public IMouseDevice MouseDevice { get; } = new MouseDevice();
             public WindowTransparencyLevel TransparencyLevel { get; }
-
+            
+            public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+            {
+                // TODO adjust status bar depending on full screen mode.
+                if (OperatingSystem.IsIOSVersionAtLeast(13))
+                {
+                    var uiStatusBarStyle = themeVariant switch
+                    {
+                        PlatformThemeVariant.Light => UIStatusBarStyle.DarkContent,
+                        PlatformThemeVariant.Dark => UIStatusBarStyle.LightContent,
+                        _ => throw new ArgumentOutOfRangeException(nameof(themeVariant), themeVariant, null)
+                    };
+                    
+                    // Consider using UIViewController.PreferredStatusBarStyle in the future.
+                    UIApplication.SharedApplication.SetStatusBarStyle(uiStatusBarStyle, true);
+                }
+            }
+            
             public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } =
                 new AcrylicPlatformCompensationLevels();
 
diff --git a/src/iOS/Avalonia.iOS/AvaloniaViewController.cs b/src/iOS/Avalonia.iOS/AvaloniaViewController.cs
new file mode 100644
index 0000000000..c6856789b8
--- /dev/null
+++ b/src/iOS/Avalonia.iOS/AvaloniaViewController.cs
@@ -0,0 +1,6 @@
+namespace Avalonia.iOS;
+
+public class AvaloniaViewController
+{
+    
+}
diff --git a/src/iOS/Avalonia.iOS/Platform.cs b/src/iOS/Avalonia.iOS/Platform.cs
index 63025f7f0a..5bcd1eae84 100644
--- a/src/iOS/Avalonia.iOS/Platform.cs
+++ b/src/iOS/Avalonia.iOS/Platform.cs
@@ -40,7 +40,7 @@ namespace Avalonia.iOS
                 .Bind<ICursorFactory>().ToConstant(new CursorFactoryStub())
                 .Bind<IWindowingPlatform>().ToConstant(new WindowingPlatformStub())
                 .Bind<IClipboard>().ToConstant(new ClipboardImpl())
-                .Bind<IPlatformSettings>().ToSingleton<DefaultPlatformSettings>()
+                .Bind<IPlatformSettings>().ToSingleton<PlatformSettings>()
                 .Bind<IPlatformIconLoader>().ToConstant(new PlatformIconLoaderStub())
                 .Bind<PlatformHotkeyConfiguration>().ToSingleton<PlatformHotkeyConfiguration>()
                 .Bind<IRenderLoop>().ToSingleton<RenderLoop>()
diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
new file mode 100644
index 0000000000..736e94ffc6
--- /dev/null
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -0,0 +1,34 @@
+using System;
+using System.Linq;
+using Avalonia.Media;
+using Avalonia.Platform;
+using Foundation;
+using UIKit;
+
+namespace Avalonia.iOS;
+
+// TODO: ideally should be created per view/activity.
+internal class PlatformSettings : DefaultPlatformSettings
+{
+    private PlatformColorValues _lastColorValues;
+
+    public override PlatformColorValues GetColorValues()
+    {
+        var themeVariant = UITraitCollection.CurrentTraitCollection.UserInterfaceStyle == UIUserInterfaceStyle.Dark ?
+            PlatformThemeVariant.Dark :
+            PlatformThemeVariant.Light;
+        
+        return _lastColorValues = new PlatformColorValues(themeVariant);
+    }
+
+    public void TraitCollectionDidChange()
+    {
+        var oldColorValues = _lastColorValues;
+        var colorValues = GetColorValues();
+
+        if (oldColorValues != colorValues)
+        {
+            OnColorValuesChanged(colorValues);
+        }
+    }
+}

From 70dcf71910afa309d6ec5ae35729e501a3073ec7 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:15:26 -0500
Subject: [PATCH 100/157] Browser implementation

---
 .../BrowserPlatformSettings.cs                | 26 +++++++++++++++++++
 .../Avalonia.Browser/BrowserTopLevelImpl.cs   |  5 ++++
 .../Avalonia.Browser/Interop/DomHelper.cs     |  5 ++++
 .../Avalonia.Browser/WindowingPlatform.cs     |  2 +-
 .../webapp/modules/avalonia/dom.ts            | 13 ++++++++++
 5 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs

diff --git a/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs b/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs
new file mode 100644
index 0000000000..8a5a089752
--- /dev/null
+++ b/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs
@@ -0,0 +1,26 @@
+using Avalonia.Browser.Interop;
+using Avalonia.Platform;
+
+namespace Avalonia.Browser;
+
+internal class BrowserPlatformSettings : DefaultPlatformSettings
+{
+    private bool _isDarkMode;
+    
+    public BrowserPlatformSettings()
+    {
+        _isDarkMode = DomHelper.ObserveDarkMode(m =>
+        {
+            _isDarkMode = m;
+            OnColorValuesChanged(GetColorValues());
+        });
+    }
+    
+    public override PlatformColorValues GetColorValues()
+    {
+        return base.GetColorValues() with
+        {
+            ThemeVariant = _isDarkMode ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light
+        };
+    }
+}
diff --git a/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs b/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
index 4e6be3268b..a1f293757c 100644
--- a/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
+++ b/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
@@ -228,6 +228,11 @@ namespace Avalonia.Browser
 
         public IKeyboardDevice KeyboardDevice { get; } = BrowserWindowingPlatform.Keyboard;
         public WindowTransparencyLevel TransparencyLevel { get; private set; }
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        {
+            // not in the standard, but we potentially can use "apple-mobile-web-app-status-bar-style" for iOS and "theme-color" for android.
+        }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; }
 
         public ITextInputMethodImpl TextInputMethod => _avaloniaView;
diff --git a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
index b97a03209b..090f03c4f1 100644
--- a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
+++ b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
@@ -25,4 +25,9 @@ internal static partial class DomHelper
     public static partial double ObserveDpi(
        [JSMarshalAs<JSType.Function<JSType.Number, JSType.Number>>]
         Action<double, double> onDpiChanged);
+    
+    [JSImport("AvaloniaDOM.observeDarkMode", AvaloniaModule.MainModuleName)]
+    public static partial bool ObserveDarkMode(
+        [JSMarshalAs<JSType.Function<JSType.Boolean>>]
+        Action<bool> onDpiChanged);
 }
diff --git a/src/Browser/Avalonia.Browser/WindowingPlatform.cs b/src/Browser/Avalonia.Browser/WindowingPlatform.cs
index 6493374a50..46db8936eb 100644
--- a/src/Browser/Avalonia.Browser/WindowingPlatform.cs
+++ b/src/Browser/Avalonia.Browser/WindowingPlatform.cs
@@ -39,7 +39,7 @@ namespace Avalonia.Browser
                 .Bind<IClipboard>().ToSingleton<ClipboardImpl>()
                 .Bind<ICursorFactory>().ToSingleton<CssCursorFactory>()
                 .Bind<IKeyboardDevice>().ToConstant(s_keyboard)
-                .Bind<IPlatformSettings>().ToSingleton<DefaultPlatformSettings>()
+                .Bind<IPlatformSettings>().ToSingleton<BrowserPlatformSettings>()
                 .Bind<IPlatformThreadingInterface>().ToConstant(instance)
                 .Bind<IRenderLoop>().ToConstant(new RenderLoop())
                 .Bind<IRenderTimer>().ToConstant(ManualTriggerRenderTimer.Instance)
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
index e8e37faf58..9760fccc3b 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
@@ -3,6 +3,19 @@ export class AvaloniaDOM {
         element.classList.add(className);
     }
 
+    static observeDarkMode(observer: (isDarkMode: boolean) => boolean): boolean {
+        if (globalThis.matchMedia === undefined) {
+            return false;
+        }
+
+        const media = globalThis.matchMedia("(prefers-color-scheme: dark)");
+        media.addEventListener("change", (args: MediaQueryListEvent) => {
+            observer(args.matches);
+        });
+
+        return media.matches;
+    }
+
     static createAvaloniaHost(host: HTMLElement) {
         const randomIdPart = Math.random().toString(36).replace(/[^a-z]+/g, "").substr(2, 10);
 

From 8f11c5a6ede15080385e8fd51c2cfdc5e356ea0a Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:15:36 -0500
Subject: [PATCH 101/157] macOS implementation

---
 .../project.pbxproj                           |   4 +
 .../src/OSX/PlatformSettings.mm               | 111 ++++++++++++++++++
 .../Avalonia.Native/src/OSX/WindowBaseImpl.h  |   2 +
 .../Avalonia.Native/src/OSX/WindowBaseImpl.mm |  18 +++
 native/Avalonia.Native/src/OSX/common.h       |   1 +
 native/Avalonia.Native/src/OSX/main.mm        |  10 ++
 src/Avalonia.Native/AvaloniaNativePlatform.cs |   2 +-
 src/Avalonia.Native/NativePlatformSettings.cs |  61 ++++++++++
 src/Avalonia.Native/WindowImplBase.cs         |   5 +
 src/Avalonia.Native/avn.idl                   |  16 +++
 10 files changed, 229 insertions(+), 1 deletion(-)
 create mode 100644 native/Avalonia.Native/src/OSX/PlatformSettings.mm
 create mode 100644 src/Avalonia.Native/NativePlatformSettings.cs

diff --git a/native/Avalonia.Native/src/OSX/Avalonia.Native.OSX.xcodeproj/project.pbxproj b/native/Avalonia.Native/src/OSX/Avalonia.Native.OSX.xcodeproj/project.pbxproj
index ace4a71a56..41d1534f8d 100644
--- a/native/Avalonia.Native/src/OSX/Avalonia.Native.OSX.xcodeproj/project.pbxproj
+++ b/native/Avalonia.Native/src/OSX/Avalonia.Native.OSX.xcodeproj/project.pbxproj
@@ -50,6 +50,7 @@
 		BC11A5BE2608D58F0017BAD0 /* automation.h in Headers */ = {isa = PBXBuildFile; fileRef = BC11A5BC2608D58F0017BAD0 /* automation.h */; };
 		BC11A5BF2608D58F0017BAD0 /* automation.mm in Sources */ = {isa = PBXBuildFile; fileRef = BC11A5BD2608D58F0017BAD0 /* automation.mm */; };
 		ED3791C42862E1F40080BD62 /* UniformTypeIdentifiers.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = ED3791C32862E1F40080BD62 /* UniformTypeIdentifiers.framework */; };
+		EDF8CDCD2964CB01001EE34F /* PlatformSettings.mm in Sources */ = {isa = PBXBuildFile; fileRef = EDF8CDCC2964CB01001EE34F /* PlatformSettings.mm */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
@@ -103,6 +104,7 @@
 		BC11A5BC2608D58F0017BAD0 /* automation.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = automation.h; sourceTree = "<group>"; };
 		BC11A5BD2608D58F0017BAD0 /* automation.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = automation.mm; sourceTree = "<group>"; };
 		ED3791C32862E1F40080BD62 /* UniformTypeIdentifiers.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = UniformTypeIdentifiers.framework; path = System/Library/Frameworks/UniformTypeIdentifiers.framework; sourceTree = SDKROOT; };
+		EDF8CDCC2964CB01001EE34F /* PlatformSettings.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = PlatformSettings.mm; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -163,6 +165,7 @@
 				1A3E5EA723E9E83B00EDE661 /* rendertarget.mm */,
 				37A517B22159597E00FBA241 /* Screens.mm */,
 				37C09D8721580FE4006A6758 /* SystemDialogs.mm */,
+				EDF8CDCC2964CB01001EE34F /* PlatformSettings.mm */,
 				AB7A61F02147C815003C5833 /* Products */,
 				AB661C1C2148230E00291242 /* Frameworks */,
 				18391676ECF0E983F4964357 /* WindowBaseImpl.mm */,
@@ -299,6 +302,7 @@
 				1839151F32D1BB1AB51A7BB6 /* AvnPanelWindow.mm in Sources */,
 				18391AC16726CBC45856233B /* AvnWindow.mm in Sources */,
 				18391D8CD1756DC858DC1A09 /* PopupImpl.mm in Sources */,
+				EDF8CDCD2964CB01001EE34F /* PlatformSettings.mm in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/native/Avalonia.Native/src/OSX/PlatformSettings.mm b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
new file mode 100644
index 0000000000..e709cd5135
--- /dev/null
+++ b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
@@ -0,0 +1,111 @@
+#include "common.h"
+
+@interface CocoaThemeObserver : NSObject
+-(id)initWithCallback:(IAvnActionCallback *)callback;
+@end
+
+class PlatformSettings : public ComSingleObject<IAvnPlatformSettings, &IID_IAvnPlatformSettings>
+{
+    CocoaThemeObserver* observer;
+
+public:
+    FORWARD_IUNKNOWN()
+    virtual AvnPlatformThemeVariant GetPlatformTheme() override
+    {
+        @autoreleasepool
+        {
+            if (@available(macOS 10.14, *))
+            {
+                if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantLight
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
+                    return AvnPlatformThemeVariant::Light;
+                } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameDarkAqua
+                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantDark
+                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
+                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
+                    return AvnPlatformThemeVariant::Dark;
+                }
+            }
+            return AvnPlatformThemeVariant::Light;
+        }
+    }
+    
+    virtual unsigned int GetAccentColor() override
+    {
+        @autoreleasepool
+        {
+            if (@available(macOS 10.14, *))
+            {
+                auto color = [NSColor controlAccentColor];
+                return to_argb(color);
+            }
+            else
+            {
+                return 0;
+            }
+        }
+    }
+    
+    virtual void RegisterColorsChange(IAvnActionCallback *callback) override
+    {
+        if (@available(macOS 10.14, *))
+        {
+            observer = [[CocoaThemeObserver alloc] initWithCallback: callback];
+            [[NSApplication sharedApplication] addObserver:observer forKeyPath:@"effectiveAppearance" options:NSKeyValueObservingOptionNew context:nil];
+        }
+    }
+    
+private:
+    unsigned int to_argb(NSColor* color)
+    {
+        const CGFloat* components = CGColorGetComponents(color.CGColor);
+        unsigned int alpha = static_cast<unsigned int>(CGColorGetAlpha(color.CGColor) * 0xFF);
+        unsigned int red = static_cast<unsigned int>(components[0] * 0xFF);
+        unsigned int green = static_cast<unsigned int>(components[1] * 0xFF);
+        unsigned int blue = static_cast<unsigned int>(components[2] * 0xFF);
+        return (alpha << 24) + (red << 16) + (green << 8) + blue;
+    }
+};
+
+@implementation CocoaThemeObserver
+{
+    ComPtr<IAvnActionCallback> _callback;
+}
+- (id) initWithCallback:(IAvnActionCallback *)callback{
+    self = [super init];
+    if (self) {
+        _callback = callback;
+    }
+    return self;
+}
+
+/*- (void)didChangeValueForKey:(NSString *)key {
+    if([key isEqualToString:@"effectiveAppearance"]) {
+        _callback->Run();
+    }
+    else {
+        [super didChangeValueForKey:key];
+    }
+}*/
+
+- (void)observeValueForKeyPath:(NSString *)keyPath
+                      ofObject:(id)object
+                        change:(NSDictionary *)change
+                       context:(void *)context {
+    if([keyPath isEqualToString:@"effectiveAppearance"]) {
+        _callback->Run();
+    } else {
+        [super observeValueForKeyPath:keyPath
+                             ofObject:object
+                               change:change
+                              context:context];
+    }
+}
+@end
+
+extern IAvnPlatformSettings* CreatePlatformSettings()
+{
+    return new PlatformSettings();
+}
diff --git a/native/Avalonia.Native/src/OSX/WindowBaseImpl.h b/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
index 7fb002e54f..1404ec361c 100644
--- a/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
+++ b/native/Avalonia.Native/src/OSX/WindowBaseImpl.h
@@ -92,6 +92,8 @@ BEGIN_INTERFACE_MAP()
 
     virtual HRESULT SetTransparencyMode(AvnWindowTransparencyMode mode) override;
 
+    virtual HRESULT SetFrameThemeVariant(AvnPlatformThemeVariant variant) override;
+
     virtual HRESULT BeginDragAndDropOperation(AvnDragDropEffects effects, AvnPoint point,
             IAvnClipboard *clipboard, IAvnDndResultCallback *cb,
             void *sourceHandle) override;
diff --git a/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm b/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
index 9946ad9b10..39dde5a582 100644
--- a/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
+++ b/native/Avalonia.Native/src/OSX/WindowBaseImpl.mm
@@ -498,6 +498,24 @@ HRESULT WindowBaseImpl::SetTransparencyMode(AvnWindowTransparencyMode mode) {
     return S_OK;
 }
 
+HRESULT WindowBaseImpl::SetFrameThemeVariant(AvnPlatformThemeVariant variant) {
+    START_COM_CALL;
+
+    NSAppearanceName appearanceName;
+    if (@available(macOS 10.14, *))
+    {
+        appearanceName = variant == AvnPlatformThemeVariant::Dark ? NSAppearanceNameDarkAqua : NSAppearanceNameAqua;
+    }
+    else
+    {
+        appearanceName = variant == AvnPlatformThemeVariant::Dark ? NSAppearanceNameVibrantDark : NSAppearanceNameAqua;
+    }
+
+    [Window setAppearance: [NSAppearance appearanceNamed: appearanceName]];
+
+    return S_OK;
+}
+
 HRESULT WindowBaseImpl::BeginDragAndDropOperation(AvnDragDropEffects effects, AvnPoint point, IAvnClipboard *clipboard, IAvnDndResultCallback *cb, void *sourceHandle) {
     START_COM_CALL;
 
diff --git a/native/Avalonia.Native/src/OSX/common.h b/native/Avalonia.Native/src/OSX/common.h
index 7ee7205776..972927b99d 100644
--- a/native/Avalonia.Native/src/OSX/common.h
+++ b/native/Avalonia.Native/src/OSX/common.h
@@ -27,6 +27,7 @@ extern IAvnMenuItem* CreateAppMenuItem();
 extern IAvnMenuItem* CreateAppMenuItemSeparator();
 extern IAvnApplicationCommands* CreateApplicationCommands();
 extern IAvnNativeControlHost* CreateNativeControlHost(NSView* parent);
+extern IAvnPlatformSettings* CreatePlatformSettings();
 extern void SetAppMenu(IAvnMenu *menu);
 extern void SetServicesMenu (IAvnMenu* menu);
 extern IAvnMenu* GetAppMenu ();
diff --git a/native/Avalonia.Native/src/OSX/main.mm b/native/Avalonia.Native/src/OSX/main.mm
index c29d4108d0..99063e600e 100644
--- a/native/Avalonia.Native/src/OSX/main.mm
+++ b/native/Avalonia.Native/src/OSX/main.mm
@@ -398,6 +398,16 @@ public:
         }
     }
     
+    virtual HRESULT CreatePlatformSettings (IAvnPlatformSettings** ppv) override
+    {
+        START_COM_CALL;
+        
+        @autoreleasepool
+        {
+            *ppv = ::CreatePlatformSettings();
+            return S_OK;
+        }
+    }
 };
 
 extern "C" IAvaloniaNativeFactory* CreateAvaloniaNative()
diff --git a/src/Avalonia.Native/AvaloniaNativePlatform.cs b/src/Avalonia.Native/AvaloniaNativePlatform.cs
index 6d5925c0ae..fc23fbb226 100644
--- a/src/Avalonia.Native/AvaloniaNativePlatform.cs
+++ b/src/Avalonia.Native/AvaloniaNativePlatform.cs
@@ -104,7 +104,7 @@ namespace Avalonia.Native
                 .Bind<ICursorFactory>().ToConstant(new CursorFactory(_factory.CreateCursorFactory()))
                 .Bind<IPlatformIconLoader>().ToSingleton<IconLoader>()
                 .Bind<IKeyboardDevice>().ToConstant(KeyboardDevice)
-                .Bind<IPlatformSettings>().ToSingleton<DefaultPlatformSettings>()
+                .Bind<IPlatformSettings>().ToConstant(new NativePlatformSettings(_factory.CreatePlatformSettings()))
                 .Bind<IWindowingPlatform>().ToConstant(this)
                 .Bind<IClipboard>().ToConstant(new ClipboardImpl(_factory.CreateClipboard()))
                 .Bind<IRenderTimer>().ToConstant(new DefaultRenderTimer(60))
diff --git a/src/Avalonia.Native/NativePlatformSettings.cs b/src/Avalonia.Native/NativePlatformSettings.cs
new file mode 100644
index 0000000000..cea748bbae
--- /dev/null
+++ b/src/Avalonia.Native/NativePlatformSettings.cs
@@ -0,0 +1,61 @@
+using System;
+using Avalonia.Media;
+using Avalonia.Native.Interop;
+using Avalonia.Platform;
+
+namespace Avalonia.Native;
+
+internal class NativePlatformSettings : DefaultPlatformSettings
+{
+    private readonly IAvnPlatformSettings _platformSettings;
+    private PlatformColorValues _lastColorValues;
+
+    public NativePlatformSettings(IAvnPlatformSettings platformSettings)
+    {
+        _platformSettings = platformSettings;
+        platformSettings.RegisterColorsChange(new ColorsChangeCallback(this));
+    }
+
+    public override PlatformColorValues GetColorValues()
+    {
+        var theme = (PlatformThemeVariant)_platformSettings.PlatformTheme;
+        var color = _platformSettings.AccentColor;
+
+        if (color > 0)
+        {
+            _lastColorValues = new PlatformColorValues(theme, Color.FromUInt32(color));
+        }
+        else
+        {
+            _lastColorValues = new PlatformColorValues(theme);
+        }
+
+        return _lastColorValues;
+    }
+
+    public void OnColorValuesChanged()
+    {
+        var oldColorValues = _lastColorValues;
+        var colorValues = GetColorValues();
+
+        if (oldColorValues != colorValues)
+        {
+            OnColorValuesChanged(colorValues);
+        }
+    }
+
+    private class ColorsChangeCallback : NativeCallbackBase, IAvnActionCallback
+    {
+        private readonly NativePlatformSettings _settings;
+
+        public ColorsChangeCallback(NativePlatformSettings settings)
+        {
+            _settings = settings;
+        }
+        
+        public void Run()
+        {
+            _settings.OnColorValuesChanged();
+        }
+    }
+}
diff --git a/src/Avalonia.Native/WindowImplBase.cs b/src/Avalonia.Native/WindowImplBase.cs
index ca57e30b1c..7686b42275 100644
--- a/src/Avalonia.Native/WindowImplBase.cs
+++ b/src/Avalonia.Native/WindowImplBase.cs
@@ -519,6 +519,11 @@ namespace Avalonia.Native
 
         public WindowTransparencyLevel TransparencyLevel { get; private set; } = WindowTransparencyLevel.Transparent;
 
+        public void SetFrameThemeVariant(PlatformThemeVariant themeVariant)
+        {
+            _native.SetFrameThemeVariant((AvnPlatformThemeVariant)themeVariant);
+        }
+
         public AcrylicPlatformCompensationLevels AcrylicCompensationLevels { get; } = new AcrylicPlatformCompensationLevels(1, 0, 0);
 
         public IPlatformHandle Handle { get; private set; }
diff --git a/src/Avalonia.Native/avn.idl b/src/Avalonia.Native/avn.idl
index 8057b162f5..29f839c826 100644
--- a/src/Avalonia.Native/avn.idl
+++ b/src/Avalonia.Native/avn.idl
@@ -473,6 +473,12 @@ enum AvnWindowTransparencyMode
     Blur
 }
 
+enum AvnPlatformThemeVariant
+{
+    Light,
+    Dark
+}
+
 [uuid(809c652e-7396-11d2-9771-00a0c9b4d50c)]
 interface IAvaloniaNativeFactory : IUnknown
 {
@@ -494,6 +500,7 @@ interface IAvaloniaNativeFactory : IUnknown
      HRESULT CreateMenuItemSeparator(IAvnMenuItem** ppv);
      HRESULT CreateTrayIcon(IAvnTrayIcon** ppv);
      HRESULT CreateApplicationCommands(IAvnApplicationCommands** ppv);
+     HRESULT CreatePlatformSettings(IAvnPlatformSettings** ppv);
 }
 
 [uuid(233e094f-9b9f-44a3-9a6e-6948bbdd9fb1)]
@@ -535,6 +542,7 @@ interface IAvnWindowBase : IUnknown
      HRESULT BeginDragAndDropOperation(AvnDragDropEffects effects, AvnPoint point,
                                               IAvnClipboard* clipboard, IAvnDndResultCallback* cb, [intptr]void* sourceHandle);
      HRESULT SetTransparencyMode(AvnWindowTransparencyMode mode);
+     HRESULT SetFrameThemeVariant(AvnPlatformThemeVariant mode);
 }
 
 [uuid(83e588f3-6981-4e48-9ea0-e1e569f79a91), cpp-virtual-inherits]
@@ -906,3 +914,11 @@ interface IAvnAutomationNode : IUnknown
     void PropertyChanged(AvnAutomationProperty property);
     void FocusChanged();
 }
+
+[uuid(d1f009cc-9d2d-493b-845d-90d2c104baae)]
+interface IAvnPlatformSettings : IUnknown
+{
+    AvnPlatformThemeVariant GetPlatformTheme();
+    uint GetAccentColor();
+    void RegisterColorsChange(IAvnActionCallback* callback);
+}

From f01ea6a8a11c8750cc5c72a9be5a0867709834a5 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 02:26:41 -0500
Subject: [PATCH 102/157] Fix control catalog on mobile

---
 samples/ControlCatalog/MainView.xaml.cs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/samples/ControlCatalog/MainView.xaml.cs b/samples/ControlCatalog/MainView.xaml.cs
index ecd9d0bf52..8c8be2638e 100644
--- a/samples/ControlCatalog/MainView.xaml.cs
+++ b/samples/ControlCatalog/MainView.xaml.cs
@@ -107,6 +107,7 @@ namespace ControlCatalog
                 decorations.SelectedIndex = (int)window.SystemDecorations;
             
             _platformSettings.ColorValuesChanged += PlatformSettingsOnColorValuesChanged;
+            PlatformSettingsOnColorValuesChanged(_platformSettings, _platformSettings.GetColorValues());
         }
 
         protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)

From 1396c5aac7ba0987e06d828589b1c53b52726a62 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 19:48:05 +1100
Subject: [PATCH 103/157] Update WriteableBitmapImpl.cs

---
 src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs b/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
index 12d9471204..9864a14a9c 100644
--- a/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
+++ b/src/Skia/Avalonia.Skia/WriteableBitmapImpl.cs
@@ -97,7 +97,7 @@ namespace Avalonia.Skia
             SKColorType colorType = format.ToSkColorType();
             SKAlphaType alphaType = alphaFormat.ToSkAlphaType();
 
-            var runtimePlatform = AvaloniaLocator.Current.GetRequiredService<IRuntimePlatform>();
+            var runtimePlatform = AvaloniaLocator.Current.GetService<IRuntimePlatform>();
 
             if (runtimePlatform != null)
             {

From ac01ee00e68e0bdfbe6f0992a4743bf4472561ae Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Fri, 6 Jan 2023 20:38:05 +1100
Subject: [PATCH 104/157] .

---
 samples/Directory.Build.props                      | 5 ++---
 tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj | 1 -
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/samples/Directory.Build.props b/samples/Directory.Build.props
index 471c42ec07..3b14f0ce12 100644
--- a/samples/Directory.Build.props
+++ b/samples/Directory.Build.props
@@ -2,9 +2,8 @@
   <PropertyGroup>
       <IsPackable>false</IsPackable>
       <AvaloniaPreviewerNetCoreToolPath>$(MSBuildThisFileDirectory)..\src\tools\Avalonia.Designer.HostApp\bin\Debug\netcoreapp2.0\Avalonia.Designer.HostApp.dll</AvaloniaPreviewerNetCoreToolPath>
+      <EnableNETAnalyzers>false</EnableNETAnalyzers>
+      <LangVersion>11</LangVersion>
   </PropertyGroup>
   <Import Project="..\build\SharedVersion.props" />
-  <PropertyGroup>
-    <EnableNETAnalyzers>false</EnableNETAnalyzers>
-  </PropertyGroup>  
 </Project>
diff --git a/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj b/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
index b9c2a619d9..17448ade76 100644
--- a/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
+++ b/tests/Avalonia.UnitTests/Avalonia.UnitTests.csproj
@@ -4,7 +4,6 @@
     <GenerateAssemblyInfo>false</GenerateAssemblyInfo>
     <OutputType>Library</OutputType>
     <IsPackable>false</IsPackable>
-    <LangVersion>latest</LangVersion>
     <AssemblyOriginatorKeyFile>..\..\build\avalonia.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>false</SignAssembly>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>

From d1037a73699bfff23cd25a9c9d08bf66e3948e70 Mon Sep 17 00:00:00 2001
From: AlmightyJu <almightyju2@gmail.com>
Date: Fri, 6 Jan 2023 14:26:00 +0000
Subject: [PATCH 105/157] Fix DataGridTemplateColumn reusing edit control when
 exiting edit mode

---
 src/Avalonia.Controls.DataGrid/DataGrid.cs       |  1 +
 src/Avalonia.Controls.DataGrid/DataGridColumn.cs | 11 +++++++++++
 .../DataGridTemplateColumn.cs                    | 16 ++++++++++++----
 3 files changed, 24 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/DataGrid.cs b/src/Avalonia.Controls.DataGrid/DataGrid.cs
index 78de00078e..cadecc03bc 100644
--- a/src/Avalonia.Controls.DataGrid/DataGrid.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGrid.cs
@@ -4152,6 +4152,7 @@ namespace Avalonia.Controls
 
             if (exitEditingMode)
             {
+                CurrentColumn.EndCellEditInternal();
                 _editingColumnIndex = -1;
                 editingCell.UpdatePseudoClasses();
 
diff --git a/src/Avalonia.Controls.DataGrid/DataGridColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
index d9d80acdc3..63e7e1e2b3 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridColumn.cs
@@ -800,11 +800,22 @@ namespace Avalonia.Controls
         protected internal virtual void RefreshCellContent(Control element, string propertyName)
         { }
 
+        /// <summary>
+        /// When overridden in a derived class, called when a cell in the column exits editing mode.
+        /// </summary>
+        protected virtual void EndCellEdit()
+        { }
+
         internal void CancelCellEditInternal(Control editingElement, object uneditedValue)
         {
             CancelCellEdit(editingElement, uneditedValue);
         }
 
+        internal void EndCellEditInternal()
+        {
+            EndCellEdit();
+        }
+
         /// <summary>
         /// Coerces a DataGridLength to a valid value.  If any value components are double.NaN, this method
         /// coerces them to a proper initial value.  For star columns, the desired width is calculated based
diff --git a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
index 24ae358dcc..516e9cf6c2 100644
--- a/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
+++ b/src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs
@@ -55,17 +55,25 @@ namespace Avalonia.Controls
             get => _cellEditingCellTemplate;
             set => SetAndRaise(CellEditingTemplateProperty, ref _cellEditingCellTemplate, value);
         }
-        
-        private static void OnCellTemplateChanged(AvaloniaPropertyChangedEventArgs e)
+
+        private bool _forceGenerateCellFromTemplate;
+
+        protected override void EndCellEdit()
         {
-            var oldValue = (IDataTemplate)e.OldValue;
-            var value = (IDataTemplate)e.NewValue;
+            //the next call to generate element should not resuse the current content as we need to exit edit mode
+            _forceGenerateCellFromTemplate = true;
+            base.EndCellEdit();
         }
 
         protected override Control GenerateElement(DataGridCell cell, object dataItem)
         {
             if (CellTemplate != null)
             {
+                if (_forceGenerateCellFromTemplate)
+                {
+                    _forceGenerateCellFromTemplate = false;
+                    return CellTemplate.Build(dataItem);
+                }
                 return (CellTemplate is IRecyclingDataTemplate recyclingDataTemplate)
                     ? recyclingDataTemplate.Build(dataItem, cell.Content as Control)
                     : CellTemplate.Build(dataItem);

From 148b4a9aca16754a6b22835d6b3983fb060fa92a Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 17:11:50 -0500
Subject: [PATCH 106/157] Changes after review

---
 samples/ControlCatalog/MainView.xaml.cs        | 1 -
 src/iOS/Avalonia.iOS/AvaloniaViewController.cs | 6 ------
 2 files changed, 7 deletions(-)
 delete mode 100644 src/iOS/Avalonia.iOS/AvaloniaViewController.cs

diff --git a/samples/ControlCatalog/MainView.xaml.cs b/samples/ControlCatalog/MainView.xaml.cs
index 8c8be2638e..1726028a3f 100644
--- a/samples/ControlCatalog/MainView.xaml.cs
+++ b/samples/ControlCatalog/MainView.xaml.cs
@@ -8,7 +8,6 @@ using Avalonia.Markup.Xaml;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
 using Avalonia.Platform;
-using Avalonia.Styling;
 using Avalonia.VisualTree;
 using ControlCatalog.Models;
 using ControlCatalog.Pages;
diff --git a/src/iOS/Avalonia.iOS/AvaloniaViewController.cs b/src/iOS/Avalonia.iOS/AvaloniaViewController.cs
deleted file mode 100644
index c6856789b8..0000000000
--- a/src/iOS/Avalonia.iOS/AvaloniaViewController.cs
+++ /dev/null
@@ -1,6 +0,0 @@
-namespace Avalonia.iOS;
-
-public class AvaloniaViewController
-{
-    
-}

From 84206e93dd9980e9b590398e50e1ba780cb5ce7c Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 03:45:50 +0300
Subject: [PATCH 107/157] [Text] Optimize grapheme and add performance
 benchmark

---
 .../TextFormatting/FormattedTextSource.cs     |  2 +-
 .../Media/TextFormatting/TextCharacters.cs    |  4 +-
 .../Media/TextFormatting/Unicode/Grapheme.cs  | 14 +++--
 .../Unicode/GraphemeEnumerator.cs             |  4 +-
 src/Avalonia.Controls/TextBox.cs              |  2 +-
 .../GraphemeBreakClassTrieGeneratorTests.cs   |  4 +-
 .../Text/HugeTextLayout.cs                    | 62 +++++++++++++++++++
 .../Media/TextFormatting/TextLayoutTests.cs   |  8 +--
 8 files changed, 83 insertions(+), 17 deletions(-)
 create mode 100644 tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs

diff --git a/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs b/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
index 4472ba87eb..49d94b511d 100644
--- a/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
@@ -132,7 +132,7 @@ namespace Avalonia.Media.TextFormatting
             {
                 var grapheme = graphemeEnumerator.Current;
 
-                finalLength += grapheme.Text.Length;
+                finalLength += grapheme.Length;
 
                 if (finalLength >= length)
                 {
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs b/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
index db035b8750..1a48151834 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
@@ -196,7 +196,7 @@ namespace Avalonia.Media.TextFormatting
                     break;
                 }
 
-                count += grapheme.Text.Length;
+                count += grapheme.Length;
             }
 
             return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, count, defaultProperties, biDiLevel);
@@ -264,7 +264,7 @@ namespace Avalonia.Media.TextFormatting
                     }
                 }
 
-                length += currentGrapheme.Text.Length;
+                length += currentGrapheme.Length;
             }
 
             return length > 0;
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
index 69015fb17d..f75168083c 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
@@ -7,10 +7,11 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// </summary>
     public readonly ref struct Grapheme
     {
-        public Grapheme(Codepoint firstCodepoint, ReadOnlySpan<char> text)
+        public Grapheme(Codepoint firstCodepoint, int offset, int length)
         {
             FirstCodepoint = firstCodepoint;
-            Text = text;
+            Offset = offset;
+            Length = length;
         }
 
         /// <summary>
@@ -19,8 +20,13 @@ namespace Avalonia.Media.TextFormatting.Unicode
         public Codepoint FirstCodepoint { get; }
 
         /// <summary>
-        /// The text that is representing the <see cref="Grapheme"/>.
+        /// The Offset to the FirstCodepoint
         /// </summary>
-        public ReadOnlySpan<char> Text { get; }
+        public int Offset { get; }
+
+        /// <summary>
+        /// The length of the grapheme cluster
+        /// </summary>
+        public int Length { get; }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
index 5ca120c856..dc21e06813 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
@@ -185,9 +185,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             Return:
 
-            var text = _text.Take(processor.CurrentCodeUnitOffset);
-
-            Current = new Grapheme(firstCodepoint, text.Span);
+            Current = new Grapheme(firstCodepoint, _text.OffsetToFirstChar, processor.CurrentCodeUnitOffset);
 
             _text = _text.Skip(processor.CurrentCodeUnitOffset);
 
diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index 9a2ee12dc3..0e1024c027 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -981,7 +981,7 @@ namespace Avalonia.Controls
                         }
                     }
 
-                    length += grapheme.Text.Length;
+                    length += grapheme.Length;
                 }
 
                 if (length < input.Length)
diff --git a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
index 4e0207a85d..c57bd6c002 100644
--- a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
@@ -42,7 +42,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
 
             enumerator.MoveNext();
 
-            var actual = enumerator.Current.Text;
+            var actual = text.AsSpan(enumerator.Current.Offset, enumerator.Current.Length);
 
             var pass = true;
 
@@ -93,7 +93,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
 
             while (enumerator.MoveNext())
             {
-                Assert.Equal(1, enumerator.Current.Text.Length);
+                Assert.Equal(1, enumerator.Current.Length);
 
                 count++;
             }
diff --git a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
new file mode 100644
index 0000000000..e1b3c6a99c
--- /dev/null
+++ b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
@@ -0,0 +1,62 @@
+using System;
+using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
+using Avalonia.UnitTests;
+using BenchmarkDotNet.Attributes;
+
+namespace Avalonia.Benchmarks.Text;
+
+[MemoryDiagnoser]
+public class HugeTextLayout : IDisposable
+{
+    private readonly IDisposable _app;
+
+    public HugeTextLayout()
+    {
+        _app = UnitTestApplication.Start(
+            TestServices.StyledWindow.With(
+                renderInterface: new NullRenderingPlatform(),
+                threadingInterface: new NullThreadingPlatform(),
+                standardCursorFactory: new NullCursorFactory()));
+    }
+    
+    private const string Text = @"Though, the objectives of the development of the prominent landmarks can be neglected in most cases, it should be realized that after the completion of the strategic decision gives rise to The Expertise of Regular Program (Carlton Cartwright in The Book of the Key Factor) 
+A number of key issues arise from the belief that the explicit examination of strategic management should correlate with the conceptual design.  
+By all means, the unification of the reliably developed techniques indicates the importance of the ultimate advantage of episodic skill over alternate practices.  
+Let's consider, that the portion of the continuing support can be regarded as relentlessly insignificant. The hardware maintenance focuses our attention on the structure absorption. The real reason of the permanent growth drastically the preliminary action plan the ultimate advantage of useful probability over alternate practices.  
+Let it not be said that a section of the essential component discards the principle of the more interconnection of critical thinking with productivity boosting of the referential arguments.  
+One should, however, not forget that concentration of violations of the strategic management requires urgent actions to be taken towards the comprehensive set of policy statements. Therefore, the concept of the design aspects can be treated as the only solution.  
+In a loose sense concentration of the center of the critical thinking provides a deep insight into the emergency planning. The comparison is quite a powerful matter.  
+Resulting from review or analysis of threats and opportunities, we can presume that either significant improvement or basics of planning and scheduling reveals the patterns of the final draft. Therefore, the concept of the crucial component can be treated as the only solution.  
+One should, nevertheless, consider that the exceptional results of the diverse sources of information gives an overview of the production cycle. It should rather be regarded as an integral part of the direct access to key resources.  
+Admitting that the possibility of achieving the results of the constructive criticism, as far as the strategic management is questionable, cannot rely only on the critical thinking. It may reveal how the systems approach partially the comprehensive project management. We must be ready for outline design stage and network development investigation of every contradiction between the effective time management and the efficient decision the network development. Everyone understands what it takes to the draft analysis and prior decisions and early design solutions. In any case, we can systematically change the mechanism of the sources and influences of the continuing financing doctrine. This could exceedingly be a result of a task analysis the hardware maintenance. The real reason of the strategic planning seemingly the influence on eventual productivity. Everyone understands what it takes to the well-known practice. Therefore, the concept of the productivity boost can be treated as the only solution the driving factor. It may reveal how the matters of peculiar interest slowly the goals and objectives or the diverse sources of information the positive influence of any major outcomes complete failure of the supposed theory.  
+In respect that the structure of the sufficient amount poses problems and challenges for both the set of related commands and controls and the ability bias.";
+    
+    [Benchmark]
+    public TextLayout BuildTextLayout() => new TextLayout(Text, Typeface.Default, 12d, Brushes.Black);
+
+    private const string Emojis = @"😀 😁 😂 🤣 😃 😄 😅 😆 😉 😊 😋 😎 😍 😘 🥰 😗 😙 😚 ☺️ 🙂 🤗 🤩 🤔 🤨 😐 😑 😶 🙄 😏 😣 😥 😮 🤐 😯 😪 😫 😴 😌 😛 😜 😝 🤤 😒 😓 😔 😕 🙃 🤑 😲 ☹️ 🙁 😖 😞 😟 😤 😢 😭 😦 😧 😨 😩 🤯 😬 😰 😱 🥵 🥶 😳 🤪 😵 😡 😠 🤬 😷 🤒 🤕 🤢 🤮 🤧 😇 🤠 🤡 🥳 🥴 🥺 🤥 🤫 🤭 🧐 🤓 😈 👿 👹 👺 💀 👻 👽 🤖 💩 😺 😸 😹 😻 😼 😽 🙀 😿 😾
+👶 👧 🧒 👦 👩 🧑 👨 👵 🧓 👴 👲 👳‍♀️ 👳‍♂️ 🧕 🧔 👱‍♂️ 👱‍♀️ 👨‍🦰 👩‍🦰 👨‍🦱 👩‍🦱 👨‍🦲 👩‍🦲 👨‍🦳 👩‍🦳 🦸‍♀️ 🦸‍♂️ 🦹‍♀️ 🦹‍♂️ 👮‍♀️ 👮‍♂️ 👷‍♀️ 👷‍♂️ 💂‍♀️ 💂‍♂️ 🕵️‍♀️ 🕵️‍♂️ 👩‍⚕️ 👨‍⚕️ 👩‍🌾 👨‍🌾 👩‍🍳 👨‍🍳 👩‍🎓 👨‍🎓 👩‍🎤 👨‍🎤 👩‍🏫 👨‍🏫 👩‍🏭 👨‍🏭 👩‍💻 👨‍💻 👩‍💼 👨‍💼 👩‍🔧 👨‍🔧 👩‍🔬 👨‍🔬 👩‍🎨 👨‍🎨 👩‍🚒 👨‍🚒 👩‍✈️ 👨‍✈️ 👩‍🚀 👨‍🚀 👩‍⚖️ 👨‍⚖️ 👰 🤵 👸 🤴 🤶 🎅 🧙‍♀️ 🧙‍♂️ 🧝‍♀️ 🧝‍♂️ 🧛‍♀️ 🧛‍♂️ 🧟‍♀️ 🧟‍♂️ 🧞‍♀️ 🧞‍♂️ 🧜‍♀️ 🧜‍♂️ 🧚‍♀️ 🧚‍♂️ 👼 🤰 🤱 🙇‍♀️ 🙇‍♂️ 💁‍♀️ 💁‍♂️ 🙅‍♀️ 🙅‍♂️ 🙆‍♀️ 🙆‍♂️ 🙋‍♀️ 🙋‍♂️ 🤦‍♀️ 🤦‍♂️ 🤷‍♀️ 🤷‍♂️ 🙎‍♀️ 🙎‍♂️ 🙍‍♀️ 🙍‍♂️ 💇‍♀️ 💇‍♂️ 💆‍♀️ 💆‍♂️ 🧖‍♀️ 🧖‍♂️ 💅 🤳 💃 🕺 👯‍♀️ 👯‍♂️ 🕴 🚶‍♀️ 🚶‍♂️ 🏃‍♀️ 🏃‍♂️ 👫 👭 👬 💑 👩‍❤️‍👩 👨‍❤️‍👨 💏 👩‍❤️‍💋‍👩 👨‍❤️‍💋‍👨 👪 👨‍👩‍👧 👨‍👩‍👧‍👦 👨‍👩‍👦‍👦 👨‍👩‍👧‍👧 👩‍👩‍👦 👩‍👩‍👧 👩‍👩‍👧‍👦 👩‍👩‍👦‍👦 👩‍👩‍👧‍👧 👨‍👨‍👦 👨‍👨‍👧 👨‍👨‍👧‍👦 👨‍👨‍👦‍👦 👨‍👨‍👧‍👧 👩‍👦 👩‍👧 👩‍👧‍👦 👩‍👦‍👦 👩‍👧‍👧 👨‍👦 👨‍👧 👨‍👧‍👦 👨‍👦‍👦 👨‍👧‍👧 🤲 👐 🙌 👏 🤝 👍 👎 👊 ✊ 🤛 🤜 🤞 ✌️ 🤟 🤘 👌 👈 👉 👆 👇 ☝️ ✋ 🤚 🖐 🖖 👋 🤙 💪 🦵 🦶 🖕 ✍️ 🙏 💍 💄 💋 👄 👅 👂 👃 👣 👁 👀 🧠 🦴 🦷 🗣 👤 👥
+🧥 👚 👕 👖 👔 👗 👙 👘 👠 👡 👢 👞 👟 🥾 🥿 🧦 🧤 🧣 🎩 🧢 👒 🎓 ⛑ 👑 👝 👛 👜 💼 🎒 👓 🕶 🥽 🥼 🌂 🧵 🧶
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+🐶 🐱 🐭 🐹 🐰 🦊 🦝 🐻 🐼 🦘 🦡 🐨 🐯 🦁 🐮 🐷 🐽 🐸 🐵 🙈 🙉 🙊 🐒 🐔 🐧 🐦 🐤 🐣 🐥 🦆 🦢 🦅 🦉 🦚 🦜 🦇 🐺 🐗 🐴 🦄 🐝 🐛 🦋 🐌 🐚 🐞 🐜 🦗 🕷 🕸 🦂 🦟 🦠 🐢 🐍 🦎 🦖 🦕 🐙 🦑 🦐 🦀 🐡 🐠 🐟 🐬 🐳 🐋 🦈 🐊 🐅 🐆 🦓 🦍 🐘 🦏 🦛 🐪 🐫 🦙 🦒 🐃 🐂 🐄 🐎 🐖 🐏 🐑 🐐 🦌 🐕 🐩 🐈 🐓 🦃 🕊 🐇 🐁 🐀 🐿 🦔 🐾 🐉 🐲 🌵 🎄 🌲 🌳 🌴 🌱 🌿 ☘️ 🍀 🎍 🎋 🍃 🍂 🍁 🍄 🌾 💐 🌷 🌹 🥀 🌺 🌸 🌼 🌻 🌞 🌝 🌛 🌜 🌚 🌕 🌖 🌗 🌘 🌑 🌒 🌓 🌔 🌙 🌎 🌍 🌏 💫 ⭐️ 🌟 ✨ ⚡️ ☄️ 💥 🔥 🌪 🌈 ☀️ 🌤 ⛅️ 🌥 ☁️ 🌦 🌧 ⛈ 🌩 🌨 ❄️ ☃️ ⛄️ 🌬 💨 💧 💦 ☔️ ☂️ 🌊 🌫
+🍏 🍎 🍐 🍊 🍋 🍌 🍉 🍇 🍓 🍈 🍒 🍑 🍍 🥭 🥥 🥝 🍅 🍆 🥑 🥦 🥒 🥬 🌶 🌽 🥕 🥔 🍠 🥐 🍞 🥖 🥨 🥯 🧀 🥚 🍳 🥞 🥓 🥩 🍗 🍖 🌭 🍔 🍟 🍕 🥪 🥙 🌮 🌯 🥗 🥘 🥫 🍝 🍜 🍲 🍛 🍣 🍱 🥟 🍤 🍙 🍚 🍘 🍥 🥮 🥠 🍢 🍡 🍧 🍨 🍦 🥧 🍰 🎂 🍮 🍭 🍬 🍫 🍿 🧂 🍩 🍪 🌰 🥜 🍯 🥛 🍼 ☕️ 🍵 🥤 🍶 🍺 🍻 🥂 🍷 🥃 🍸 🍹 🍾 🥄 🍴 🍽 🥣 🥡 🥢
+⚽️ 🏀 🏈 ⚾️ 🥎 🏐 🏉 🎾 🥏 🎱 🏓 🏸 🥅 🏒 🏑 🥍 🏏 ⛳️ 🏹 🎣 🥊 🥋 🎽 ⛸ 🥌 🛷 🛹 🎿 ⛷ 🏂 🏋️‍♀️ 🏋🏻‍♀️ 🏋🏼‍♀️ 🏋🏽‍♀️ 🏋🏾‍♀️ 🏋🏿‍♀️ 🏋️‍♂️ 🏋🏻‍♂️ 🏋🏼‍♂️ 🏋🏽‍♂️ 🏋🏾‍♂️ 🏋🏿‍♂️ 🤼‍♀️ 🤼‍♂️ 🤸‍♀️ 🤸🏻‍♀️ 🤸🏼‍♀️ 🤸🏽‍♀️ 🤸🏾‍♀️ 🤸🏿‍♀️ 🤸‍♂️ 🤸🏻‍♂️ 🤸🏼‍♂️ 🤸🏽‍♂️ 🤸🏾‍♂️ 🤸🏿‍♂️ ⛹️‍♀️ ⛹🏻‍♀️ ⛹🏼‍♀️ ⛹🏽‍♀️ ⛹🏾‍♀️ ⛹🏿‍♀️ ⛹️‍♂️ ⛹🏻‍♂️ ⛹🏼‍♂️ ⛹🏽‍♂️ ⛹🏾‍♂️ ⛹🏿‍♂️ 🤺 🤾‍♀️ 🤾🏻‍♀️ 🤾🏼‍♀️ 🤾🏾‍♀️ 🤾🏾‍♀️ 🤾🏿‍♀️ 🤾‍♂️ 🤾🏻‍♂️ 🤾🏼‍♂️ 🤾🏽‍♂️ 🤾🏾‍♂️ 🤾🏿‍♂️ 🏌️‍♀️ 🏌🏻‍♀️ 🏌🏼‍♀️ 🏌🏽‍♀️ 🏌🏾‍♀️ 🏌🏿‍♀️ 🏌️‍♂️ 🏌🏻‍♂️ 🏌🏼‍♂️ 🏌🏽‍♂️ 🏌🏾‍♂️ 🏌🏿‍♂️ 🏇 🏇🏻 🏇🏼 🏇🏽 🏇🏾 🏇🏿 🧘‍♀️ 🧘🏻‍♀️ 🧘🏼‍♀️ 🧘🏽‍♀️ 🧘🏾‍♀️ 🧘🏿‍♀️ 🧘‍♂️ 🧘🏻‍♂️ 🧘🏼‍♂️ 🧘🏽‍♂️ 🧘🏾‍♂️ 🧘🏿‍♂️ 🏄‍♀️ 🏄🏻‍♀️ 🏄🏼‍♀️ 🏄🏽‍♀️ 🏄🏾‍♀️ 🏄🏿‍♀️ 🏄‍♂️ 🏄🏻‍♂️ 🏄🏼‍♂️ 🏄🏽‍♂️ 🏄🏾‍♂️ 🏄🏿‍♂️ 🏊‍♀️ 🏊🏻‍♀️ 🏊🏼‍♀️ 🏊🏽‍♀️ 🏊🏾‍♀️ 🏊🏿‍♀️ 🏊‍♂️ 🏊🏻‍♂️ 🏊🏼‍♂️ 🏊🏽‍♂️ 🏊🏾‍♂️ 🏊🏿‍♂️ 🤽‍♀️ 🤽🏻‍♀️ 🤽🏼‍♀️ 🤽🏽‍♀️ 🤽🏾‍♀️ 🤽🏿‍♀️ 🤽‍♂️ 🤽🏻‍♂️ 🤽🏼‍♂️ 🤽🏽‍♂️ 🤽🏾‍♂️ 🤽🏿‍♂️ 🚣‍♀️ 🚣🏻‍♀️ 🚣🏼‍♀️ 🚣🏽‍♀️ 🚣🏾‍♀️ 🚣🏿‍♀️ 🚣‍♂️ 🚣🏻‍♂️ 🚣🏼‍♂️ 🚣🏽‍♂️ 🚣🏾‍♂️ 🚣🏿‍♂️ 🧗‍♀️ 🧗🏻‍♀️ 🧗🏼‍♀️ 🧗🏽‍♀️ 🧗🏾‍♀️ 🧗🏿‍♀️ 🧗‍♂️ 🧗🏻‍♂️ 🧗🏼‍♂️ 🧗🏽‍♂️ 🧗🏾‍♂️ 🧗🏿‍♂️ 🚵‍♀️ 🚵🏻‍♀️ 🚵🏼‍♀️ 🚵🏽‍♀️ 🚵🏾‍♀️ 🚵🏿‍♀️ 🚵‍♂️ 🚵🏻‍♂️ 🚵🏼‍♂️ 🚵🏽‍♂️ 🚵🏾‍♂️ 🚵🏿‍♂️ 🚴‍♀️ 🚴🏻‍♀️ 🚴🏼‍♀️ 🚴🏽‍♀️ 🚴🏾‍♀️ 🚴🏿‍♀️ 🚴‍♂️ 🚴🏻‍♂️ 🚴🏼‍♂️ 🚴🏽‍♂️ 🚴🏾‍♂️ 🚴🏿‍♂️ 🏆 🥇 🥈 🥉 🏅 🎖 🏵 🎗 🎫 🎟 🎪 🤹‍♀️ 🤹🏻‍♀️ 🤹🏼‍♀️ 🤹🏽‍♀️ 🤹🏾‍♀️ 🤹🏿‍♀️ 🤹‍♂️ 🤹🏻‍♂️ 🤹🏼‍♂️ 🤹🏽‍♂️ 🤹🏾‍♂️ 🤹🏿‍♂️ 🎭 🎨 🎬 🎤 🎧 🎼 🎹 🥁 🎷 🎺 🎸 🎻 🎲 🧩 ♟ 🎯 🎳 🎮 🎰
+🚗 🚕 🚙 🚌 🚎 🏎 🚓 🚑 🚒 🚐 🚚 🚛 🚜 🛴 🚲 🛵 🏍 🚨 🚔 🚍 🚘 🚖 🚡 🚠 🚟 🚃 🚋 🚞 🚝 🚄 🚅 🚈 🚂 🚆 🚇 🚊 🚉 ✈️ 🛫 🛬 🛩 💺 🛰 🚀 🛸 🚁 🛶 ⛵️ 🚤 🛥 🛳 ⛴ 🚢 ⚓️ ⛽️ 🚧 🚦 🚥 🚏 🗺 🗿 🗽 🗼 🏰 🏯 🏟 🎡 🎢 🎠 ⛲️ ⛱ 🏖 🏝 🏜 🌋 ⛰ 🏔 🗻 🏕 ⛺️ 🏠 🏡 🏘 🏚 🏗 🏭 🏢 🏬 🏣 🏤 🏥 🏦 🏨 🏪 🏫 🏩 💒 🏛 ⛪️ 🕌 🕍 🕋 ⛩ 🛤 🛣 🗾 🎑 🏞 🌅 🌄 🌠 🎇 🎆 🌇 🌆 🏙 🌃 🌌 🌉 🌁
+⌚️ 📱 📲 💻 ⌨️ 🖥 🖨 🖱 🖲 🕹 🗜 💽 💾 💿 📀 📼 📷 📸 📹 🎥 📽 🎞 📞 ☎️ 📟 📠 📺 📻 🎙 🎚 🎛 ⏱ ⏲ ⏰ 🕰 ⌛️ ⏳ 📡 🔋 🔌 💡 🔦 🕯 🗑 🛢 💸 💵 💴 💶 💷 💰 💳 🧾 💎 ⚖️ 🔧 🔨 ⚒ 🛠 ⛏ 🔩 ⚙️ ⛓ 🔫 💣 🔪 🗡 ⚔️ 🛡 🚬 ⚰️ ⚱️ 🏺 🧭 🧱 🔮 🧿 🧸 📿 💈 ⚗️ 🔭 🧰 🧲 🧪 🧫 🧬 🧯 🔬 🕳 💊 💉 🌡 🚽 🚰 🚿 🛁 🛀 🛀🏻 🛀🏼 🛀🏽 🛀🏾 🛀🏿 🧴 🧵 🧶 🧷 🧹 🧺 🧻 🧼 🧽 🛎 🔑 🗝 🚪 🛋 🛏 🛌 🖼 🛍 🧳 🛒 🎁 🎈 🎏 🎀 🎊 🎉 🧨 🎎 🏮 🎐 🧧 ✉️ 📩 📨 📧 💌 📥 📤 📦 🏷 📪 📫 📬 📭 📮 📯 📜 📃 📄 📑 📊 📈 📉 🗒 🗓 📆 📅 📇 🗃 🗳 🗄 📋 📁 📂 🗂 🗞 📰 📓 📔 📒 📕 📗 📘 📙 📚 📖 🔖 🔗 📎 🖇 📐 📏 📌 📍 ✂️ 🖊 🖋 ✒️ 🖌 🖍 📝 ✏️ 🔍 🔎 🔏 🔐 🔒 🔓
+❤️ 🧡 💛 💚 💙 💜 🖤 💔 ❣️ 💕 💞 💓 💗 💖 💘 💝 💟 ☮️ ✝️ ☪️ 🕉 ☸️ ✡️ 🔯 🕎 ☯️ ☦️ 🛐 ⛎ ♈️ ♉️ ♊️ ♋️ ♌️ ♍️ ♎️ ♏️ ♐️ ♑️ ♒️ ♓️ 🆔 ⚛️ 🉑 ☢️ ☣️ 📴 📳 🈶 🈚️ 🈸 🈺 🈷️ ✴️ 🆚 💮 🉐 ㊙️ ㊗️ 🈴 🈵 🈹 🈲 🅰️ 🅱️ 🆎 🆑 🅾️ 🆘 ❌ ⭕️ 🛑 ⛔️ 📛 🚫 💯 💢 ♨️ 🚷 🚯 🚳 🚱 🔞 📵 🚭 ❗️ ❕ ❓ ❔ ‼️ ⁉️ 🔅 🔆 〽️ ⚠️ 🚸 🔱 ⚜️ 🔰 ♻️ ✅ 🈯️ 💹 ❇️ ✳️ ❎ 🌐 💠 Ⓜ️ 🌀 💤 🏧 🚾 ♿️ 🅿️ 🈳 🈂️ 🛂 🛃 🛄 🛅 🚹 🚺 🚼 🚻 🚮 🎦 📶 🈁 🔣 ℹ️ 🔤 🔡 🔠 🆖 🆗 🆙 🆒 🆕 🆓 0️⃣ 1️⃣ 2️⃣ 3️⃣ 4️⃣ 5️⃣ 6️⃣ 7️⃣ 8️⃣ 9️⃣ 🔟 🔢 #️⃣ *️⃣ ⏏️ ▶️ ⏸ ⏯ ⏹ ⏺ ⏭ ⏮ ⏩ ⏪ ⏫ ⏬ ◀️ 🔼 🔽 ➡️ ⬅️ ⬆️ ⬇️ ↗️ ↘️ ↙️ ↖️ ↕️ ↔️ ↪️ ↩️ ⤴️ ⤵️ 🔀 🔁 🔂 🔄 🔃 🎵 🎶 ➕ ➖ ➗ ✖️ ♾ 💲 💱 ™️ ©️ ®️ 〰️ ➰ ➿ 🔚 🔙 🔛 🔝 🔜 ✔️ ☑️ 🔘 ⚪️ ⚫️ 🔴 🔵 🔺 🔻 🔸 🔹 🔶 🔷 🔳 🔲 ▪️ ▫️ ◾️ ◽️ ◼️ ◻️ ⬛️ ⬜️ 🔈 🔇 🔉 🔊 🔔 🔕 📣 📢 👁‍🗨 💬 💭 🗯 ♠️ ♣️ ♥️ ♦️ 🃏 🎴 🀄️ 🕐 🕑 🕒 🕓 🕔 🕕 🕖 🕗 🕘 🕙 🕚 🕛 🕜 🕝 🕞 🕟 🕠 🕡 🕢 🕣 🕤 🕥 🕦 🕧
+🏳️ 🏴 🏁 🚩 🏳️‍🌈 🏴‍☠️ 🇦🇫 🇦🇽 🇦🇱 🇩🇿 🇦🇸 🇦🇩 🇦🇴 🇦🇮 🇦🇶 🇦🇬 🇦🇷 🇦🇲 🇦🇼 🇦🇺 🇦🇹 🇦🇿 🇧🇸 🇧🇭 🇧🇩 🇧🇧 🇧🇾 🇧🇪 🇧🇿 🇧🇯 🇧🇲 🇧🇹 🇧🇴 🇧🇦 🇧🇼 🇧🇷 🇮🇴 🇻🇬 🇧🇳 🇧🇬 🇧🇫 🇧🇮 🇰🇭 🇨🇲 🇨🇦 🇮🇨 🇨🇻 🇧🇶 🇰🇾 🇨🇫 🇹🇩 🇨🇱 🇨🇳 🇨🇽 🇨🇨 🇨🇴 🇰🇲 🇨🇬 🇨🇩 🇨🇰 🇨🇷 🇨🇮 🇭🇷 🇨🇺 🇨🇼 🇨🇾 🇨🇿 🇩🇰 🇩🇯 🇩🇲 🇩🇴 🇪🇨 🇪🇬 🇸🇻 🇬🇶 🇪🇷 🇪🇪 🇪🇹 🇪🇺 🇫🇰 🇫🇴 🇫🇯 🇫🇮 🇫🇷 🇬🇫 🇵🇫 🇹🇫 🇬🇦 🇬🇲 🇬🇪 🇩🇪 🇬🇭 🇬🇮 🇬🇷 🇬🇱 🇬🇩 🇬🇵 🇬🇺 🇬🇹 🇬🇬 🇬🇳 🇬🇼 🇬🇾 🇭🇹 🇭🇳 🇭🇰 🇭🇺 🇮🇸 🇮🇳 🇮🇩 🇮🇷 🇮🇶 🇮🇪 🇮🇲 🇮🇱 🇮🇹 🇯🇲 🇯🇵 🎌 🇯🇪 🇯🇴 🇰🇿 🇰🇪 🇰🇮 🇽🇰 🇰🇼 🇰🇬 🇱🇦 🇱🇻 🇱🇧 🇱🇸 🇱🇷 🇱🇾 🇱🇮 🇱🇹 🇱🇺 🇲🇴 🇲🇰 🇲🇬 🇲🇼 🇲🇾 🇲🇻 🇲🇱 🇲🇹 🇲🇭 🇲🇶 🇲🇷 🇲🇺 🇾🇹 🇲🇽 🇫🇲 🇲🇩 🇲🇨 🇲🇳 🇲🇪 🇲🇸 🇲🇦 🇲🇿 🇲🇲 🇳🇦 🇳🇷 🇳🇵 🇳🇱 🇳🇨 🇳🇿 🇳🇮 🇳🇪 🇳🇬 🇳🇺 🇳🇫 🇰🇵 🇲🇵 🇳🇴 🇴🇲 🇵🇰 🇵🇼 🇵🇸 🇵🇦 🇵🇬 🇵🇾 🇵🇪 🇵🇭 🇵🇳 🇵🇱 🇵🇹 🇵🇷 🇶🇦 🇷🇪 🇷🇴 🇷🇺 🇷🇼 🇼🇸 🇸🇲 🇸🇦 🇸🇳 🇷🇸 🇸🇨 🇸🇱 🇸🇬 🇸🇽 🇸🇰 🇸🇮 🇬🇸 🇸🇧 🇸🇴 🇿🇦 🇰🇷 🇸🇸 🇪🇸 🇱🇰 🇧🇱 🇸🇭 🇰🇳 🇱🇨 🇵🇲 🇻🇨 🇸🇩 🇸🇷 🇸🇿 🇸🇪 🇨🇭 🇸🇾 🇹🇼 🇹🇯 🇹🇿 🇹🇭 🇹🇱 🇹🇬 🇹🇰 🇹🇴 🇹🇹 🇹🇳 🇹🇷 🇹🇲 🇹🇨 🇹🇻 🇻🇮 🇺🇬 🇺🇦 🇦🇪 🇬🇧 🏴󠁧󠁢󠁥󠁮󠁧󠁿 🏴󠁧󠁢󠁳󠁣󠁴󠁿 🏴󠁧󠁢󠁷󠁬󠁳󠁿 🇺🇳 🇺🇸 🇺🇾 🇺🇿 🇻🇺 🇻🇦 🇻🇪 🇻🇳 🇼🇫 🇪🇭 🇾🇪 🇿🇲 🇿🇼
+🥱 🤏 🦾 🦿 🦻 🧏 🧏‍♂️ 🧏‍♀️ 🧍 🧍‍♂️ 🧍‍♀️ 🧎 🧎‍♂️ 🧎‍♀️ 👨‍🦯 👩‍🦯 👨‍🦼 👩‍🦼 👨‍🦽 👩‍🦽 🦧 🦮 🐕‍🦺 🦥 🦦 🦨 🦩 🧄 🧅 🧇 🧆 🧈 🦪 🧃 🧉 🧊 🛕 🦽 🦼 🛺 🪂 🪐 🤿 🪀 🪁 🦺 🥻 🩱 🩲 🩳 🩰 🪕 🪔 🪓 🦯 🩸 🩹 🩺 🪑 🪒 🤎 🤍 🟠 🟡 🟢 🟣 🟤 🟥 🟧 🟨 🟩 🟦 🟪 🟫";
+    
+    [Benchmark]
+    public TextLayout BuildEmojisTextLayout() => new TextLayout(Emojis, Typeface.Default, 12d, Brushes.Black);
+
+    public void Dispose()
+    {
+        _app?.Dispose();
+    }
+}
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
index 2790bd6096..7501bf21fe 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
@@ -153,7 +153,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 {
                     while (inner.MoveNext())
                     {
-                        j += inner.Current.Text.Length;
+                        j += inner.Current.Length;
 
                         if (j + i > text.Length)
                         {
@@ -192,7 +192,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                     inner = new GraphemeEnumerator(new CharacterBufferRange(text));
 
-                    i += outer.Current.Text.Length;
+                    i += outer.Current.Length;
                 }
             }
         }
@@ -974,9 +974,9 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 {
                     var grapheme = graphemeEnumerator.Current;
 
-                    var textStyleOverrides = new[] { new ValueSpan<TextRunProperties>(i, grapheme.Text.Length, new GenericTextRunProperties(Typeface.Default, 12, foregroundBrush: Brushes.Red)) };
+                    var textStyleOverrides = new[] { new ValueSpan<TextRunProperties>(i, grapheme.Length, new GenericTextRunProperties(Typeface.Default, 12, foregroundBrush: Brushes.Red)) };
 
-                    i += grapheme.Text.Length;
+                    i += grapheme.Length;
 
                     var layout = new TextLayout(
                         text,

From 8c30948e62dcf565d26dbda39020c5dbb15f096a Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 04:59:46 +0300
Subject: [PATCH 108/157] [Text] optimize CharacterBufferReference indexator

---
 src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
index d76f212f26..86e44a5269 100644
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
@@ -140,7 +140,7 @@ namespace Avalonia.Media.TextFormatting
                     throw new ArgumentOutOfRangeException(nameof(index));
                 }
 #endif
-                return Span[index];
+                return CharacterBufferReference.CharacterBuffer.Span[CharacterBufferReference.OffsetToFirstChar + index];
             }
         }
 

From 5bd28141b78d88bb72eb92fe4edb00451dc1e7d8 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 05:07:27 +0300
Subject: [PATCH 109/157] [Text] minor optimize of CharacterBufferRange

---
 .../TextFormatting/CharacterBufferRange.cs    | 29 +++++--------------
 1 file changed, 7 insertions(+), 22 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
index 86e44a5269..599b35dd2c 100644
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
@@ -147,12 +147,12 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Gets a reference to the character buffer
         /// </summary>
-        public CharacterBufferReference CharacterBufferReference { get; }
+        public readonly CharacterBufferReference CharacterBufferReference;
 
         /// <summary>
         /// Gets the number of characters in text source character store
         /// </summary>
-        public int Length { get; }
+        public readonly int Length;
 
         /// <summary>
         /// Gets a span from the character buffer range
@@ -163,27 +163,18 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Gets the character memory buffer
         /// </summary>
-        internal ReadOnlyMemory<char> CharacterBuffer
-        {
-            get { return CharacterBufferReference.CharacterBuffer; }
-        }
+        internal ReadOnlyMemory<char> CharacterBuffer => CharacterBufferReference.CharacterBuffer;
 
         /// <summary>
         /// Gets the character offset relative to the beginning of buffer to 
         /// the first character of the run
         /// </summary>
-        internal int OffsetToFirstChar
-        {
-            get { return CharacterBufferReference.OffsetToFirstChar; }
-        }
+        internal int OffsetToFirstChar => CharacterBufferReference.OffsetToFirstChar;
 
         /// <summary>
         /// Indicate whether the character buffer range is empty
         /// </summary>
-        internal bool IsEmpty
-        {
-            get { return CharacterBufferReference.CharacterBuffer.Length == 0 || Length <= 0; }
-        }
+        internal bool IsEmpty => CharacterBufferReference.CharacterBuffer.Length == 0 || Length <= 0;
 
         internal CharacterBufferRange Take(int length)
         {
@@ -280,14 +271,8 @@ namespace Avalonia.Media.TextFormatting
 
         int IReadOnlyCollection<char>.Count => Length;
 
-        public IEnumerator<char> GetEnumerator()
-        {
-            return new ImmutableReadOnlyListStructEnumerator<char>(this);
-        }
+        public IEnumerator<char> GetEnumerator() => new ImmutableReadOnlyListStructEnumerator<char>(this);
 
-        IEnumerator IEnumerable.GetEnumerator()
-        {
-            return GetEnumerator();
-        }
+        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
     }
 }

From ba9bf5d3641df0d75c780c4ef021b7762764f3d6 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 05:13:50 +0300
Subject: [PATCH 110/157] [Text] Clone CodePoint ReadAt for Span

---
 .../Media/TextFormatting/Unicode/Codepoint.cs | 68 ++++++++++++++++++-
 .../Unicode/CodepointEnumerator.cs            |  2 +-
 .../Unicode/GraphemeEnumerator.cs             |  2 +-
 .../Avalonia.UnitTests/MockTextShaperImpl.cs  |  2 +-
 4 files changed, 70 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
index e6408bcfa6..ecd0681e15 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 
 namespace Avalonia.Media.TextFormatting.Unicode
@@ -222,6 +223,71 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             return new Codepoint(code);
         }
+        
+        /// <summary>
+        /// Reads the <see cref="Codepoint"/> at specified position.
+        /// </summary>
+        /// <param name="text">The buffer to read from.</param>
+        /// <param name="index">The index to read at.</param>
+        /// <param name="count">The count of character that were read.</param>
+        /// <returns></returns>
+        public static Codepoint ReadAt(ReadOnlySpan<char> text, int index, out int count)
+        {
+            count = 1;
+
+            if (index >= text.Length)
+            {
+                return ReplacementCodepoint;
+            }
+
+            var code = text[index];
+
+            ushort hi, low;
+
+            //# High surrogate
+            if (0xD800 <= code && code <= 0xDBFF)
+            {
+                hi = code;
+
+                if (index + 1 == text.Length)
+                {
+                    return ReplacementCodepoint;
+                }
+
+                low = text[index + 1];
+
+                if (0xDC00 <= low && low <= 0xDFFF)
+                {
+                    count = 2;
+                    return new Codepoint((uint)((hi - 0xD800) * 0x400 + (low - 0xDC00) + 0x10000));
+                }
+
+                return ReplacementCodepoint;
+            }
+
+            //# Low surrogate
+            if (0xDC00 <= code && code <= 0xDFFF)
+            {
+                if (index == 0)
+                {
+                    return ReplacementCodepoint;
+                }
+
+                hi = text[index - 1];
+
+                low = code;
+
+                if (0xD800 <= hi && hi <= 0xDBFF)
+                {
+                    count = 2;
+                    return new Codepoint((uint)((hi - 0xD800) * 0x400 + (low - 0xDC00) + 0x10000));
+                }
+
+                return ReplacementCodepoint;
+            }
+
+            return new Codepoint(code);
+        }
 
         /// <summary>
         /// Returns <see langword="true"/> if <paramref name="cp"/> is between
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
index a2c36d9a13..a2e29812d3 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
@@ -30,7 +30,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                 return false;
             }
 
-            Current = Codepoint.ReadAt(_text, 0, out var count);
+            Current = Codepoint.ReadAt(_text.Span, 0, out var count);
 
             _text = _text.Skip(count);
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
index dc21e06813..2488b620e7 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
@@ -245,7 +245,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
                     if (CurrentCodeUnitOffset < _buffer.Length)
                     {
-                        CurrentCodepoint = Codepoint.ReadAt(_buffer, CurrentCodeUnitOffset,
+                        CurrentCodepoint = Codepoint.ReadAt(_buffer.Span, CurrentCodeUnitOffset,
                             out _codeUnitLengthOfCurrentScalar);
                     }
                     else
diff --git a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
index 00bcef295a..d010f9ebf2 100644
--- a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
+++ b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
@@ -18,7 +18,7 @@ namespace Avalonia.UnitTests
             {
                 var glyphCluster = i + text.OffsetToFirstChar;
 
-                var codepoint = Codepoint.ReadAt(characterBufferRange, i, out var count);
+                var codepoint = Codepoint.ReadAt(characterBufferRange.Span, i, out var count);
 
                 var glyphIndex = typeface.GetGlyph(codepoint);
 

From 80972e5f5b287809caeabe0b8873c845061f7c34 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 05:23:58 +0300
Subject: [PATCH 111/157] [Text] a bit better usage of Codepoint.ReadAt

---
 src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs     | 2 +-
 .../Media/TextFormatting/Unicode/CodepointEnumerator.cs         | 2 +-
 .../Media/TextFormatting/Unicode/GraphemeEnumerator.cs          | 2 +-
 tests/Avalonia.UnitTests/MockTextShaperImpl.cs                  | 2 +-
 4 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
index ecd0681e15..8b9d1c1d02 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
@@ -231,7 +231,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <param name="index">The index to read at.</param>
         /// <param name="count">The count of character that were read.</param>
         /// <returns></returns>
-        public static Codepoint ReadAt(ReadOnlySpan<char> text, int index, out int count)
+        public static Codepoint ReadAt(CharacterBufferRange text, int index, out int count)
         {
             count = 1;
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
index a2e29812d3..a2c36d9a13 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
@@ -30,7 +30,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                 return false;
             }
 
-            Current = Codepoint.ReadAt(_text.Span, 0, out var count);
+            Current = Codepoint.ReadAt(_text, 0, out var count);
 
             _text = _text.Skip(count);
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
index 2488b620e7..dc21e06813 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
@@ -245,7 +245,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
                     if (CurrentCodeUnitOffset < _buffer.Length)
                     {
-                        CurrentCodepoint = Codepoint.ReadAt(_buffer.Span, CurrentCodeUnitOffset,
+                        CurrentCodepoint = Codepoint.ReadAt(_buffer, CurrentCodeUnitOffset,
                             out _codeUnitLengthOfCurrentScalar);
                     }
                     else
diff --git a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
index d010f9ebf2..00bcef295a 100644
--- a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
+++ b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
@@ -18,7 +18,7 @@ namespace Avalonia.UnitTests
             {
                 var glyphCluster = i + text.OffsetToFirstChar;
 
-                var codepoint = Codepoint.ReadAt(characterBufferRange.Span, i, out var count);
+                var codepoint = Codepoint.ReadAt(characterBufferRange, i, out var count);
 
                 var glyphIndex = typeface.GetGlyph(codepoint);
 

From 13c14e7360d032168b9a04f4fdd3089f800808bb Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 22:40:23 -0500
Subject: [PATCH 112/157] Add ColorContrastPreference to the
 PlatformColorValues

---
 .../src/OSX/PlatformSettings.mm               | 14 ++--
 .../Platform/AndroidPlatformSettings.cs       | 37 ++++++++---
 .../Platform/DefaultPlatformSettings.cs       |  5 +-
 .../Platform/PlatformColorValues.cs           | 64 +++++++++++++------
 .../DBusPlatformSettings.cs                   |  9 ++-
 src/Avalonia.Native/NativePlatformSettings.cs | 22 ++++++-
 src/Avalonia.Native/avn.idl                   |  4 +-
 .../BrowserPlatformSettings.cs                | 13 ++--
 .../Avalonia.Browser/Interop/DomHelper.cs     |  6 +-
 .../webapp/modules/avalonia/dom.ts            | 18 ++++--
 src/Windows/Avalonia.Win32/Win32Platform.cs   | 11 ++++
 .../Avalonia.Win32/Win32PlatformSettings.cs   | 45 ++++++++++---
 .../WinRT/NativeWinRTMethods.cs               | 26 +++++++-
 src/Windows/Avalonia.Win32/WinRT/winrt.idl    |  7 ++
 .../Avalonia.Win32/WindowImpl.AppWndProc.cs   |  8 ---
 src/iOS/Avalonia.iOS/PlatformSettings.cs      | 11 +++-
 16 files changed, 228 insertions(+), 72 deletions(-)

diff --git a/native/Avalonia.Native/src/OSX/PlatformSettings.mm b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
index e709cd5135..fe88214c8d 100644
--- a/native/Avalonia.Native/src/OSX/PlatformSettings.mm
+++ b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
@@ -17,15 +17,17 @@ public:
             if (@available(macOS 10.14, *))
             {
                 if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAqua
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantLight
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
-                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantLight) {
                     return AvnPlatformThemeVariant::Light;
                 } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameDarkAqua
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantDark
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
-                           || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameVibrantDark) {
                     return AvnPlatformThemeVariant::Dark;
+                } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
+                    return AvnPlatformThemeVariant::HighContrastLight;
+                } else if (|| NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
+                    || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
+                    return AvnPlatformThemeVariant::HighContrastDark;
                 }
             }
             return AvnPlatformThemeVariant::Light;
diff --git a/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs b/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
index f560dea3ce..0872603e7b 100644
--- a/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
+++ b/src/Android/Avalonia.Android/Platform/AndroidPlatformSettings.cs
@@ -3,6 +3,8 @@ using Android;
 using Android.Content;
 using Android.Content.Res;
 using Android.Graphics;
+using Android.Provider;
+using Android.Views.Accessibility;
 using AndroidX.Core.Content.Resources;
 using Avalonia.Media;
 using Avalonia.Platform;
@@ -46,11 +48,14 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
             var accent2 = context.Resources.GetColor(17170507, context.Theme); // Resource.Color.SystemAccent2500
             var accent3 = context.Resources.GetColor(17170520, context.Theme); // Resource.Color.SystemAccent3500
 
-            _latestValues = new PlatformColorValues(
-                systemTheme,
-                new Color(accent1.A, accent1.R, accent1.G, accent1.B),
-                new Color(accent2.A, accent2.R, accent2.G, accent2.B),
-                new Color(accent3.A, accent3.R, accent3.G, accent3.B));
+            _latestValues = new PlatformColorValues
+            {
+                ThemeVariant = systemTheme,
+                ContrastPreference = IsHighContrast(context),
+                AccentColor1 = new Color(accent1.A, accent1.R, accent1.G, accent1.B),
+                AccentColor2 = new Color(accent2.A, accent2.R, accent2.G, accent2.B),
+                AccentColor3 = new Color(accent3.A, accent3.R, accent3.G, accent3.B),
+            };
         }
         else if (OperatingSystem.IsAndroidVersionAtLeast(23))
         {
@@ -58,9 +63,12 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
             var array = context.Theme.ObtainStyledAttributes(new[] { 16843829 }); // Resource.Attribute.ColorAccent
             var accent = array.GetColor(0, 0);
 
-            _latestValues = new PlatformColorValues(
-                systemTheme,
-                new Color(accent.A, accent.R, accent.G, accent.B));
+            _latestValues = new PlatformColorValues
+            {
+                ThemeVariant = systemTheme,
+                ContrastPreference = IsHighContrast(context),
+                AccentColor1 = new Color(accent.A, accent.R, accent.G, accent.B)
+            };
             array.Recycle();
         }
         else
@@ -70,4 +78,17 @@ internal class AndroidPlatformSettings : DefaultPlatformSettings
 
         OnColorValuesChanged(_latestValues);
     }
+
+    private static ColorContrastPreference IsHighContrast(Context context)
+    {
+        try
+        {
+            return Settings.Secure.GetInt(context.ContentResolver, "high_text_contrast_enabled", 0) == 1
+                ? ColorContrastPreference.High : ColorContrastPreference.NoPreference;
+        }
+        catch
+        {
+            return ColorContrastPreference.NoPreference;
+        }
+    }
 }
diff --git a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
index 98f2367819..b5e7298b7e 100644
--- a/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
+++ b/src/Avalonia.Base/Platform/DefaultPlatformSettings.cs
@@ -31,7 +31,10 @@ namespace Avalonia.Platform
         
         public virtual PlatformColorValues GetColorValues()
         {
-            return new PlatformColorValues(PlatformThemeVariant.Light);
+            return new PlatformColorValues
+            {
+                ThemeVariant = PlatformThemeVariant.Light
+            };
         }
 
         public event EventHandler<PlatformColorValues>? ColorValuesChanged;
diff --git a/src/Avalonia.Base/Platform/PlatformColorValues.cs b/src/Avalonia.Base/Platform/PlatformColorValues.cs
index 3071cc217f..d14b58e939 100644
--- a/src/Avalonia.Base/Platform/PlatformColorValues.cs
+++ b/src/Avalonia.Base/Platform/PlatformColorValues.cs
@@ -11,32 +11,58 @@ public enum PlatformThemeVariant
     Dark
 }
 
+/// <summary>
+/// System high contrast preference.
+/// </summary>
+public enum ColorContrastPreference
+{
+    NoPreference,
+    High
+}
+
 /// <summary>
 /// Information about current system color values, including information about dark mode and accent colors.
 /// </summary>
-/// <param name="ThemeVariant">System theme variant or mode.</param>
-/// <param name="AccentColor1">Primary system accent color.</param>
-/// <param name="AccentColor2">Secondary system accent color. On some platforms can return the same value as AccentColor1.</param>
-/// <param name="AccentColor3">Tertiary system accent color. On some platforms can return the same value as AccentColor1.</param>
-public record struct PlatformColorValues(
-    PlatformThemeVariant ThemeVariant,
-    Color AccentColor1,
-    Color AccentColor2,
-    Color AccentColor3)
+public record PlatformColorValues
 {
-    public PlatformColorValues(
-        PlatformThemeVariant ThemeVariant,
-        Color AccentColor1)
-        : this(ThemeVariant, AccentColor1, AccentColor1, AccentColor1)
+    private static Color DefaultAccent => new(255, 0, 120, 215);
+    private Color _accentColor2, _accentColor3;
+
+    /// <summary>
+    /// System theme variant or mode.
+    /// </summary>
+    public PlatformThemeVariant ThemeVariant { get; init; }
+
+    /// <summary>
+    /// System high contrast preference.
+    /// </summary>
+    public ColorContrastPreference ContrastPreference { get; init; }
+    
+    /// <summary>
+    /// Primary system accent color.
+    /// </summary>
+    public Color AccentColor1 { get; init; }
+
+    /// <summary>
+    /// Secondary system accent color. On some platforms can return the same value as <see cref="AccentColor1"/>.
+    /// </summary>
+    public Color AccentColor2
     {
-            
+        get => _accentColor2 != default ? _accentColor2 : AccentColor1;
+        init => _accentColor2 = value;
     }
-        
-    public PlatformColorValues(PlatformThemeVariant ThemeVariant)
-        : this(ThemeVariant, DefaultAccent)
+
+    /// <summary>
+    /// Tertiary system accent color. On some platforms can return the same value as <see cref="AccentColor1"/>.
+    /// </summary>
+    public Color AccentColor3
     {
+        get => _accentColor3 != default ? _accentColor3 : AccentColor1;
+        init => _accentColor3 = value;
+    }
 
+    public PlatformColorValues()
+    {
+        AccentColor1 = DefaultAccent;
     }
-        
-    private static Color DefaultAccent => new(255, 0, 120, 215);
 }
diff --git a/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs b/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
index 82b4a72e74..039fc7c088 100644
--- a/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
+++ b/src/Avalonia.FreeDesktop/DBusPlatformSettings.cs
@@ -41,7 +41,7 @@ internal class DBusPlatformSettings : DefaultPlatformSettings
             {
                 var value = await colorSchemeTask;
                 _lastColorValues = GetColorValuesFromSetting(value);
-                OnColorValuesChanged(_lastColorValues.Value);
+                OnColorValuesChanged(_lastColorValues);
             }
             catch (Exception ex)
             {
@@ -62,13 +62,16 @@ internal class DBusPlatformSettings : DefaultPlatformSettings
             <member>2: Prefer light appearance</member>
             */
             _lastColorValues = GetColorValuesFromSetting(tuple.value);
-            OnColorValuesChanged(_lastColorValues.Value);
+            OnColorValuesChanged(_lastColorValues);
         }
     }
     
     private static PlatformColorValues GetColorValuesFromSetting(object value)
     {
         var isDark = value?.ToString() == "1";
-        return new PlatformColorValues(isDark ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light);
+        return new PlatformColorValues
+        {
+            ThemeVariant = isDark ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light
+        };
     }
 }
diff --git a/src/Avalonia.Native/NativePlatformSettings.cs b/src/Avalonia.Native/NativePlatformSettings.cs
index cea748bbae..53d3da0378 100644
--- a/src/Avalonia.Native/NativePlatformSettings.cs
+++ b/src/Avalonia.Native/NativePlatformSettings.cs
@@ -18,16 +18,32 @@ internal class NativePlatformSettings : DefaultPlatformSettings
 
     public override PlatformColorValues GetColorValues()
     {
-        var theme = (PlatformThemeVariant)_platformSettings.PlatformTheme;
+        var (theme, contrast) = _platformSettings.PlatformTheme switch
+        {
+            AvnPlatformThemeVariant.Dark => (PlatformThemeVariant.Dark, ColorContrastPreference.NoPreference),
+            AvnPlatformThemeVariant.Light => (PlatformThemeVariant.Light, ColorContrastPreference.NoPreference),
+            AvnPlatformThemeVariant.HighContrastDark => (PlatformThemeVariant.Dark, ColorContrastPreference.High),
+            AvnPlatformThemeVariant.HighContrastLight => (PlatformThemeVariant.Dark, ColorContrastPreference.High),
+            _ => throw new ArgumentOutOfRangeException()
+        };
         var color = _platformSettings.AccentColor;
 
         if (color > 0)
         {
-            _lastColorValues = new PlatformColorValues(theme, Color.FromUInt32(color));
+            _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = theme,
+                ContrastPreference = contrast,
+                AccentColor1 = Color.FromUInt32(color)
+            };
         }
         else
         {
-            _lastColorValues = new PlatformColorValues(theme);
+            _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = theme,
+                ContrastPreference = contrast
+            };
         }
 
         return _lastColorValues;
diff --git a/src/Avalonia.Native/avn.idl b/src/Avalonia.Native/avn.idl
index 29f839c826..a062fdc61d 100644
--- a/src/Avalonia.Native/avn.idl
+++ b/src/Avalonia.Native/avn.idl
@@ -476,7 +476,9 @@ enum AvnWindowTransparencyMode
 enum AvnPlatformThemeVariant
 {
     Light,
-    Dark
+    Dark,
+    HighContrastLight,
+    HighContrastDark,
 }
 
 [uuid(809c652e-7396-11d2-9771-00a0c9b4d50c)]
diff --git a/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs b/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs
index 8a5a089752..6084c5c7de 100644
--- a/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs
+++ b/src/Browser/Avalonia.Browser/BrowserPlatformSettings.cs
@@ -6,21 +6,26 @@ namespace Avalonia.Browser;
 internal class BrowserPlatformSettings : DefaultPlatformSettings
 {
     private bool _isDarkMode;
+    private bool _isHighContrast;
     
     public BrowserPlatformSettings()
     {
-        _isDarkMode = DomHelper.ObserveDarkMode(m =>
+        var obj = DomHelper.ObserveDarkMode((isDarkMode, isHighContrast) =>
         {
-            _isDarkMode = m;
+            _isDarkMode = isDarkMode;
+            _isHighContrast = isHighContrast;
             OnColorValuesChanged(GetColorValues());
         });
+        _isDarkMode = obj.GetPropertyAsBoolean("isDarkMode");
+        _isHighContrast = obj.GetPropertyAsBoolean("isHighContrast");
     }
-    
+
     public override PlatformColorValues GetColorValues()
     {
         return base.GetColorValues() with
         {
-            ThemeVariant = _isDarkMode ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light
+            ThemeVariant = _isDarkMode ? PlatformThemeVariant.Dark : PlatformThemeVariant.Light,
+            ContrastPreference = _isHighContrast ? ColorContrastPreference.High : ColorContrastPreference.NoPreference
         };
     }
 }
diff --git a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
index 090f03c4f1..9ee96768ec 100644
--- a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
+++ b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
@@ -27,7 +27,7 @@ internal static partial class DomHelper
         Action<double, double> onDpiChanged);
     
     [JSImport("AvaloniaDOM.observeDarkMode", AvaloniaModule.MainModuleName)]
-    public static partial bool ObserveDarkMode(
-        [JSMarshalAs<JSType.Function<JSType.Boolean>>]
-        Action<bool> onDpiChanged);
+    public static partial JSObject ObserveDarkMode(
+        [JSMarshalAs<JSType.Function<JSType.Boolean, JSType.Boolean>>]
+        Action<bool, bool> onDpiChanged);
 }
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
index 9760fccc3b..b99f8e7907 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/dom.ts
@@ -3,17 +3,25 @@ export class AvaloniaDOM {
         element.classList.add(className);
     }
 
-    static observeDarkMode(observer: (isDarkMode: boolean) => boolean): boolean {
+    static observeDarkMode(observer: (isDarkMode: boolean, isHighContrast: boolean) => boolean) {
         if (globalThis.matchMedia === undefined) {
             return false;
         }
 
-        const media = globalThis.matchMedia("(prefers-color-scheme: dark)");
-        media.addEventListener("change", (args: MediaQueryListEvent) => {
-            observer(args.matches);
+        const colorShemeMedia = globalThis.matchMedia("(prefers-color-scheme: dark)");
+        const prefersContrastMedia = globalThis.matchMedia("(prefers-contrast: more)");
+
+        colorShemeMedia.addEventListener("change", (args: MediaQueryListEvent) => {
+            observer(args.matches, prefersContrastMedia.matches);
+        });
+        prefersContrastMedia.addEventListener("change", (args: MediaQueryListEvent) => {
+            observer(colorShemeMedia.matches, args.matches);
         });
 
-        return media.matches;
+        return {
+            isDarkMode: colorShemeMedia.matches,
+            isHighContrast: prefersContrastMedia.matches
+        };
     }
 
     static createAvaloniaHost(host: HTMLElement) {
diff --git a/src/Windows/Avalonia.Win32/Win32Platform.cs b/src/Windows/Avalonia.Win32/Win32Platform.cs
index c0a0ce4da0..26c9fc7abe 100644
--- a/src/Windows/Avalonia.Win32/Win32Platform.cs
+++ b/src/Windows/Avalonia.Win32/Win32Platform.cs
@@ -287,6 +287,17 @@ namespace Avalonia.Win32
                     }
                 }
             }
+
+            if (msg == (uint)WindowsMessage.WM_SETTINGCHANGE 
+                && PlatformSettings is Win32PlatformSettings win32PlatformSettings)
+            {
+                var changedSetting = Marshal.PtrToStringAuto(lParam);
+                if (changedSetting == "ImmersiveColorSet" // dark/light mode
+                    || changedSetting == "WindowsThemeElement") // high contrast mode
+                {
+                    win32PlatformSettings.OnColorValuesChanged();   
+                }
+            }
             
             TrayIconImpl.ProcWnd(hWnd, msg, wParam, lParam);
 
diff --git a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
index 73ac5bf5a9..a021a3c48c 100644
--- a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
+++ b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Runtime.InteropServices;
 using Avalonia.Input;
 using Avalonia.Platform;
 using Avalonia.Win32.Interop;
@@ -38,18 +39,44 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
             return base.GetColorValues();
         }
 
-        var settings = NativeWinRTMethods.CreateInstance<IUISettings3>("Windows.UI.ViewManagement.UISettings");
-        var accent = settings.GetColorValue(UIColorType.Accent).ToAvalonia();
-        var background = settings.GetColorValue(UIColorType.Background).ToAvalonia();
+        var uiSettings = NativeWinRTMethods.CreateInstance<IUISettings3>("Windows.UI.ViewManagement.UISettings");
+        var accent = uiSettings.GetColorValue(UIColorType.Accent).ToAvalonia();
 
-        return _lastColorValues = new PlatformColorValues(
-            background.R + background.G + background.B < (255 * 3 - background.R - background.G - background.B)
-                ? PlatformThemeVariant.Dark
-                : PlatformThemeVariant.Light,
-            accent, accent, accent);
+        var accessibilitySettings = NativeWinRTMethods.CreateInstance<IAccessibilitySettings>("Windows.UI.ViewManagement.AccessibilitySettings");
+        if (accessibilitySettings.HighContrast == 1)
+        {
+            // Windows 11 has 4 different high contrast schemes:
+            // - Aquatic - High Contrast Black
+            // - Desert - High Contrast White
+            // - Dusk - High Contrast #1
+            // - Night sky - High Contrast #2
+            // Only "Desert" one can be considered a "light" preference. 
+            using var highContrastScheme = new HStringInterop(accessibilitySettings.HighContrastScheme);
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = highContrastScheme.Value?.Contains("White", StringComparison.OrdinalIgnoreCase) == true ?
+                    PlatformThemeVariant.Light :
+                    PlatformThemeVariant.Dark,
+                ContrastPreference = ColorContrastPreference.High,
+                // Windows provides more than one accent color for the HighContrast themes, but with no API for that (at least not in the WinRT)
+                AccentColor1 = accent
+            };
+        }
+        else
+        {
+            var background = uiSettings.GetColorValue(UIColorType.Background).ToAvalonia();
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = background.R + background.G + background.B < (255 * 3 - background.R - background.G - background.B) ?
+                    PlatformThemeVariant.Dark :
+                    PlatformThemeVariant.Light,
+                ContrastPreference = ColorContrastPreference.NoPreference,
+                AccentColor1 = accent
+            };   
+        }
     }
     
-    internal void OnColorValuesChanged(IntPtr handle)
+    internal void OnColorValuesChanged()
     {
         var oldColorValues = _lastColorValues;
         var colorValues = GetColorValues();
diff --git a/src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs b/src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs
index 1794b022fe..01b45f3df2 100644
--- a/src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs
+++ b/src/Windows/Avalonia.Win32/WinRT/NativeWinRTMethods.cs
@@ -22,6 +22,9 @@ namespace Avalonia.Win32.WinRT
         internal static IntPtr WindowsCreateString(string sourceString) 
             => WindowsCreateString(sourceString, sourceString.Length);
 
+        [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", CallingConvention = CallingConvention.StdCall)]
+        internal static extern unsafe char* WindowsGetStringRawBuffer(IntPtr hstring, uint* length);
+
         [DllImport("api-ms-win-core-winrt-string-l1-1-0.dll", 
             CallingConvention = CallingConvention.StdCall, PreserveSig = false)]
         internal static extern unsafe void WindowsDeleteString(IntPtr hString);
@@ -120,17 +123,38 @@ namespace Avalonia.Win32.WinRT
     class HStringInterop : IDisposable
     {
         private IntPtr _s;
+        private bool _owns;
 
         public HStringInterop(string s)
         {
             _s = s == null ? IntPtr.Zero : NativeWinRTMethods.WindowsCreateString(s);
+            _owns = true;
+        }
+        
+        public HStringInterop(IntPtr str, bool owns = false)
+        {
+            _s = str;
+            _owns = owns;
         }
 
         public IntPtr Handle => _s;
 
+        public unsafe string Value
+        {
+            get
+            {
+                if (_s == IntPtr.Zero)
+                    return null;
+
+                uint length;
+                var buffer = NativeWinRTMethods.WindowsGetStringRawBuffer(_s, &length);
+                return new string(buffer, 0, (int) length);
+            }
+        }
+        
         public void Dispose()
         {
-            if (_s != IntPtr.Zero)
+            if (_s != IntPtr.Zero && _owns)
             {
                 NativeWinRTMethods.WindowsDeleteString(_s);
                 _s = IntPtr.Zero;
diff --git a/src/Windows/Avalonia.Win32/WinRT/winrt.idl b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
index 8dee275d50..beb88352dd 100644
--- a/src/Windows/Avalonia.Win32/WinRT/winrt.idl
+++ b/src/Windows/Avalonia.Win32/WinRT/winrt.idl
@@ -864,3 +864,10 @@ interface IUISettings3 : IInspectable
 {
     HRESULT GetColorValue([in] UIColorType desiredColor, [out][retval] Color* value);
 }
+
+[uuid(FE0E8147-C4C0-4562-B962-1327B52AD5B9)]
+interface IAccessibilitySettings : IInspectable
+{
+    [propget] HRESULT HighContrast([out] [retval] boolean* value);
+    [propget] HRESULT HighContrastScheme([out] [retval] HSTRING* value);
+}
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
index af634fd760..8c362b0c29 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs
@@ -732,14 +732,6 @@ namespace Avalonia.Win32
                         var node = AutomationNode.GetOrCreate(peer);
                         return UiaCoreProviderApi.UiaReturnRawElementProvider(_hwnd, wParam, lParam, node);
                     }
-                    break;
-                case WindowsMessage.WM_SETTINGCHANGE:
-                    if (Marshal.PtrToStringAuto(lParam) == "ImmersiveColorSet"
-                        && Win32Platform.PlatformSettings is Win32PlatformSettings win32PlatformSettings)
-                    {
-                        win32PlatformSettings.OnColorValuesChanged(_hwnd);
-                    }
-
                     break;
             }
 
diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index 736e94ffc6..b8557f31bd 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -17,8 +17,17 @@ internal class PlatformSettings : DefaultPlatformSettings
         var themeVariant = UITraitCollection.CurrentTraitCollection.UserInterfaceStyle == UIUserInterfaceStyle.Dark ?
             PlatformThemeVariant.Dark :
             PlatformThemeVariant.Light;
+
+
+        var contrastPreference = UITraitCollection.CurrentTraitCollection.AccessibilityContrast == UIAccessibilityContrast.High ?
+            ColorContrastPreference.High :
+            ColorContrastPreference.NoPreference;
         
-        return _lastColorValues = new PlatformColorValues(themeVariant);
+        return _lastColorValues = new PlatformColorValues
+        {
+            ThemeVariant = themeVariant,
+            ContrastPreference = contrastPreference
+        };
     }
 
     public void TraitCollectionDidChange()

From 124c87b2cf4f15963c78511849c0c31b6398a5f0 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 23:01:13 -0500
Subject: [PATCH 113/157] Add iOS tint/accent color support

---
 src/iOS/Avalonia.iOS/AvaloniaView.cs     |  8 ++++++
 src/iOS/Avalonia.iOS/PlatformSettings.cs | 32 ++++++++++++++++++++----
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/src/iOS/Avalonia.iOS/AvaloniaView.cs b/src/iOS/Avalonia.iOS/AvaloniaView.cs
index 6d36ca7814..7442861597 100644
--- a/src/iOS/Avalonia.iOS/AvaloniaView.cs
+++ b/src/iOS/Avalonia.iOS/AvaloniaView.cs
@@ -60,6 +60,14 @@ namespace Avalonia.iOS
             settings?.TraitCollectionDidChange();
         }
 
+        public override void TintColorDidChange()
+        {
+            base.TintColorDidChange();
+            
+            var settings = AvaloniaLocator.Current.GetRequiredService<IPlatformSettings>() as PlatformSettings;
+            settings?.TraitCollectionDidChange();
+        }
+
         internal class TopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost,
             ITopLevelImplWithStorageProvider
         {
diff --git a/src/iOS/Avalonia.iOS/PlatformSettings.cs b/src/iOS/Avalonia.iOS/PlatformSettings.cs
index b8557f31bd..0ae290468b 100644
--- a/src/iOS/Avalonia.iOS/PlatformSettings.cs
+++ b/src/iOS/Avalonia.iOS/PlatformSettings.cs
@@ -22,12 +22,34 @@ internal class PlatformSettings : DefaultPlatformSettings
         var contrastPreference = UITraitCollection.CurrentTraitCollection.AccessibilityContrast == UIAccessibilityContrast.High ?
             ColorContrastPreference.High :
             ColorContrastPreference.NoPreference;
-        
-        return _lastColorValues = new PlatformColorValues
+
+        UIColor? tintColor = null;
+        if (OperatingSystem.IsIOSVersionAtLeast(14))
+        {
+            tintColor = UIConfigurationColorTransformer.PreferredTint(UIColor.Clear);
+        }
+
+        if (tintColor is not null)
         {
-            ThemeVariant = themeVariant,
-            ContrastPreference = contrastPreference
-        };
+            tintColor.GetRGBA(out var red, out var green, out var blue, out var alpha);
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = themeVariant,
+                ContrastPreference = contrastPreference,
+                AccentColor1 = new Color(
+                    (byte)(alpha * 255),
+                    (byte)(red * 255),
+                    (byte)(green * 255),
+                    (byte)(blue * 255))
+            };
+        }
+        else
+        {
+            return _lastColorValues = new PlatformColorValues
+            {
+                ThemeVariant = themeVariant, ContrastPreference = contrastPreference
+            };
+        }
     }
 
     public void TraitCollectionDidChange()

From f7605ca22e66856a19b7c4fc465cbfe92ccc06b3 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 6 Jan 2023 23:05:17 -0500
Subject: [PATCH 114/157] Fix build

---
 native/Avalonia.Native/src/OSX/PlatformSettings.mm  | 2 +-
 src/Windows/Avalonia.Win32/Win32PlatformSettings.cs | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/native/Avalonia.Native/src/OSX/PlatformSettings.mm b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
index fe88214c8d..34ceb93186 100644
--- a/native/Avalonia.Native/src/OSX/PlatformSettings.mm
+++ b/native/Avalonia.Native/src/OSX/PlatformSettings.mm
@@ -25,7 +25,7 @@ public:
                 } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastAqua
                     || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantLight) {
                     return AvnPlatformThemeVariant::HighContrastLight;
-                } else if (|| NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
+                } else if (NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastDarkAqua
                     || NSApplication.sharedApplication.effectiveAppearance.name == NSAppearanceNameAccessibilityHighContrastVibrantDark) {
                     return AvnPlatformThemeVariant::HighContrastDark;
                 }
diff --git a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
index a021a3c48c..0310c4bfad 100644
--- a/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
+++ b/src/Windows/Avalonia.Win32/Win32PlatformSettings.cs
@@ -54,7 +54,7 @@ internal class Win32PlatformSettings : DefaultPlatformSettings
             using var highContrastScheme = new HStringInterop(accessibilitySettings.HighContrastScheme);
             return _lastColorValues = new PlatformColorValues
             {
-                ThemeVariant = highContrastScheme.Value?.Contains("White", StringComparison.OrdinalIgnoreCase) == true ?
+                ThemeVariant = highContrastScheme.Value?.Contains("White") == true ?
                     PlatformThemeVariant.Light :
                     PlatformThemeVariant.Dark,
                 ContrastPreference = ColorContrastPreference.High,

From c9bf6310a8582afc10a504ae1b938267884a58f0 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sat, 7 Jan 2023 14:18:25 +0300
Subject: [PATCH 115/157] [Text] revert fields to props in CharacterBufferRange

---
 .../Media/TextFormatting/CharacterBufferRange.cs              | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
index 599b35dd2c..f5d39e4371 100644
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
@@ -147,12 +147,12 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Gets a reference to the character buffer
         /// </summary>
-        public readonly CharacterBufferReference CharacterBufferReference;
+        public CharacterBufferReference CharacterBufferReference { get; }
 
         /// <summary>
         /// Gets the number of characters in text source character store
         /// </summary>
-        public readonly int Length;
+        public int Length { get; }
 
         /// <summary>
         /// Gets a span from the character buffer range

From 2565538fd30a9669198b2c611b9fcdabd602bac0 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Sun, 8 Jan 2023 03:37:17 +0300
Subject: [PATCH 116/157] [Text] improve benchmarks. add BuildManySmallTexts
 benchmark

---
 .../Text/HugeTextLayout.cs                    | 24 ++++++++++++++++---
 1 file changed, 21 insertions(+), 3 deletions(-)

diff --git a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
index e1b3c6a99c..e696b976ad 100644
--- a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
+++ b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.UnitTests;
@@ -10,9 +11,18 @@ namespace Avalonia.Benchmarks.Text;
 public class HugeTextLayout : IDisposable
 {
     private readonly IDisposable _app;
+    private string[] _manySmallStrings;
+    private static Random _rand = new Random();
+    
+    private static string RandomString(int length)
+    {
+        const string chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789&?%$@";
+        return new string(Enumerable.Repeat(chars, length).Select(s => s[_rand.Next(s.Length)]).ToArray());
+    }
 
     public HugeTextLayout()
     {
+        _manySmallStrings = Enumerable.Range(0, 1000).Select(x => RandomString(_rand.Next(2, 15))).ToArray();
         _app = UnitTestApplication.Start(
             TestServices.StyledWindow.With(
                 renderInterface: new NullRenderingPlatform(),
@@ -29,11 +39,13 @@ One should, however, not forget that concentration of violations of the strategi
 In a loose sense concentration of the center of the critical thinking provides a deep insight into the emergency planning. The comparison is quite a powerful matter.  
 Resulting from review or analysis of threats and opportunities, we can presume that either significant improvement or basics of planning and scheduling reveals the patterns of the final draft. Therefore, the concept of the crucial component can be treated as the only solution.  
 One should, nevertheless, consider that the exceptional results of the diverse sources of information gives an overview of the production cycle. It should rather be regarded as an integral part of the direct access to key resources.  
-Admitting that the possibility of achieving the results of the constructive criticism, as far as the strategic management is questionable, cannot rely only on the critical thinking. It may reveal how the systems approach partially the comprehensive project management. We must be ready for outline design stage and network development investigation of every contradiction between the effective time management and the efficient decision the network development. Everyone understands what it takes to the draft analysis and prior decisions and early design solutions. In any case, we can systematically change the mechanism of the sources and influences of the continuing financing doctrine. This could exceedingly be a result of a task analysis the hardware maintenance. The real reason of the strategic planning seemingly the influence on eventual productivity. Everyone understands what it takes to the well-known practice. Therefore, the concept of the productivity boost can be treated as the only solution the driving factor. It may reveal how the matters of peculiar interest slowly the goals and objectives or the diverse sources of information the positive influence of any major outcomes complete failure of the supposed theory.  
+Admitting that the possibility of achieving the results of the constructive criticism, as far as the strategic management is questionable, cannot rely only on the critical thinking. It may reveal how the systems approach partially the comprehensive project management. We must be ready for outline design stage and network development investigation of every contradiction between the effective time management and the efficient decision the network development. 
+Everyone understands what it takes to the draft analysis and prior decisions and early design solutions. In any case, we can systematically change the mechanism of the sources and influences of the continuing financing doctrine. This could exceedingly be a result of a task analysis the hardware maintenance. The real reason of the strategic planning seemingly the influence on eventual productivity. Everyone understands what it takes to the well-known practice. Therefore, the concept of the productivity boost can be treated as the only solution the driving factor. 
+It may reveal how the matters of peculiar interest slowly the goals and objectives or the diverse sources of information the positive influence of any major outcomes complete failure of the supposed theory.  
 In respect that the structure of the sufficient amount poses problems and challenges for both the set of related commands and controls and the ability bias.";
     
     [Benchmark]
-    public TextLayout BuildTextLayout() => new TextLayout(Text, Typeface.Default, 12d, Brushes.Black);
+    public TextLayout BuildTextLayout() => MakeLayout(Text);
 
     private const string Emojis = @"😀 😁 😂 🤣 😃 😄 😅 😆 😉 😊 😋 😎 😍 😘 🥰 😗 😙 😚 ☺️ 🙂 🤗 🤩 🤔 🤨 😐 😑 😶 🙄 😏 😣 😥 😮 🤐 😯 😪 😫 😴 😌 😛 😜 😝 🤤 😒 😓 😔 😕 🙃 🤑 😲 ☹️ 🙁 😖 😞 😟 😤 😢 😭 😦 😧 😨 😩 🤯 😬 😰 😱 🥵 🥶 😳 🤪 😵 😡 😠 🤬 😷 🤒 🤕 🤢 🤮 🤧 😇 🤠 🤡 🥳 🥴 🥺 🤥 🤫 🤭 🧐 🤓 😈 👿 👹 👺 💀 👻 👽 🤖 💩 😺 😸 😹 😻 😼 😽 🙀 😿 😾
 👶 👧 🧒 👦 👩 🧑 👨 👵 🧓 👴 👲 👳‍♀️ 👳‍♂️ 🧕 🧔 👱‍♂️ 👱‍♀️ 👨‍🦰 👩‍🦰 👨‍🦱 👩‍🦱 👨‍🦲 👩‍🦲 👨‍🦳 👩‍🦳 🦸‍♀️ 🦸‍♂️ 🦹‍♀️ 🦹‍♂️ 👮‍♀️ 👮‍♂️ 👷‍♀️ 👷‍♂️ 💂‍♀️ 💂‍♂️ 🕵️‍♀️ 🕵️‍♂️ 👩‍⚕️ 👨‍⚕️ 👩‍🌾 👨‍🌾 👩‍🍳 👨‍🍳 👩‍🎓 👨‍🎓 👩‍🎤 👨‍🎤 👩‍🏫 👨‍🏫 👩‍🏭 👨‍🏭 👩‍💻 👨‍💻 👩‍💼 👨‍💼 👩‍🔧 👨‍🔧 👩‍🔬 👨‍🔬 👩‍🎨 👨‍🎨 👩‍🚒 👨‍🚒 👩‍✈️ 👨‍✈️ 👩‍🚀 👨‍🚀 👩‍⚖️ 👨‍⚖️ 👰 🤵 👸 🤴 🤶 🎅 🧙‍♀️ 🧙‍♂️ 🧝‍♀️ 🧝‍♂️ 🧛‍♀️ 🧛‍♂️ 🧟‍♀️ 🧟‍♂️ 🧞‍♀️ 🧞‍♂️ 🧜‍♀️ 🧜‍♂️ 🧚‍♀️ 🧚‍♂️ 👼 🤰 🤱 🙇‍♀️ 🙇‍♂️ 💁‍♀️ 💁‍♂️ 🙅‍♀️ 🙅‍♂️ 🙆‍♀️ 🙆‍♂️ 🙋‍♀️ 🙋‍♂️ 🤦‍♀️ 🤦‍♂️ 🤷‍♀️ 🤷‍♂️ 🙎‍♀️ 🙎‍♂️ 🙍‍♀️ 🙍‍♂️ 💇‍♀️ 💇‍♂️ 💆‍♀️ 💆‍♂️ 🧖‍♀️ 🧖‍♂️ 💅 🤳 💃 🕺 👯‍♀️ 👯‍♂️ 🕴 🚶‍♀️ 🚶‍♂️ 🏃‍♀️ 🏃‍♂️ 👫 👭 👬 💑 👩‍❤️‍👩 👨‍❤️‍👨 💏 👩‍❤️‍💋‍👩 👨‍❤️‍💋‍👨 👪 👨‍👩‍👧 👨‍👩‍👧‍👦 👨‍👩‍👦‍👦 👨‍👩‍👧‍👧 👩‍👩‍👦 👩‍👩‍👧 👩‍👩‍👧‍👦 👩‍👩‍👦‍👦 👩‍👩‍👧‍👧 👨‍👨‍👦 👨‍👨‍👧 👨‍👨‍👧‍👦 👨‍👨‍👦‍👦 👨‍👨‍👧‍👧 👩‍👦 👩‍👧 👩‍👧‍👦 👩‍👦‍👦 👩‍👧‍👧 👨‍👦 👨‍👧 👨‍👧‍👦 👨‍👦‍👦 👨‍👧‍👧 🤲 👐 🙌 👏 🤝 👍 👎 👊 ✊ 🤛 🤜 🤞 ✌️ 🤟 🤘 👌 👈 👉 👆 👇 ☝️ ✋ 🤚 🖐 🖖 👋 🤙 💪 🦵 🦶 🖕 ✍️ 🙏 💍 💄 💋 👄 👅 👂 👃 👣 👁 👀 🧠 🦴 🦷 🗣 👤 👥
@@ -53,7 +65,13 @@ In respect that the structure of the sufficient amount poses problems and challe
 🥱 🤏 🦾 🦿 🦻 🧏 🧏‍♂️ 🧏‍♀️ 🧍 🧍‍♂️ 🧍‍♀️ 🧎 🧎‍♂️ 🧎‍♀️ 👨‍🦯 👩‍🦯 👨‍🦼 👩‍🦼 👨‍🦽 👩‍🦽 🦧 🦮 🐕‍🦺 🦥 🦦 🦨 🦩 🧄 🧅 🧇 🧆 🧈 🦪 🧃 🧉 🧊 🛕 🦽 🦼 🛺 🪂 🪐 🤿 🪀 🪁 🦺 🥻 🩱 🩲 🩳 🩰 🪕 🪔 🪓 🦯 🩸 🩹 🩺 🪑 🪒 🤎 🤍 🟠 🟡 🟢 🟣 🟤 🟥 🟧 🟨 🟩 🟦 🟪 🟫";
     
     [Benchmark]
-    public TextLayout BuildEmojisTextLayout() => new TextLayout(Emojis, Typeface.Default, 12d, Brushes.Black);
+    public TextLayout BuildEmojisTextLayout() => MakeLayout(Emojis);
+
+    [Benchmark]
+    public TextLayout[] BuildManySmallTexts() => _manySmallStrings.Select(MakeLayout).ToArray();
+
+    private static TextLayout MakeLayout(string str) 
+        => new TextLayout(str, Typeface.Default, 12d, Brushes.Black, maxWidth:120);
 
     public void Dispose()
     {

From a78b0edd425aca64ed44eb497b52a0b7c0db4603 Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sun, 8 Jan 2023 00:17:53 -0500
Subject: [PATCH 117/157] Changes after review

---
 NOTICE.md                                     | 46 +++++++++++++++----
 .../Data/Core/ExpressionObserver.cs           |  4 +-
 src/Avalonia.Base/Reactive/Operators/Sink.cs  |  2 +
 .../Avalonia.Markup/Data/BindingBase.cs       |  5 +-
 .../Parsers/ExpressionObserverBuilder.cs      |  2 +-
 .../Core/ExpressionObserverTests_Lifetime.cs  |  6 +--
 .../Core/ExpressionObserverTests_Property.cs  | 12 ++---
 7 files changed, 53 insertions(+), 24 deletions(-)

diff --git a/NOTICE.md b/NOTICE.md
index bd26b65d70..7083706c3e 100644
--- a/NOTICE.md
+++ b/NOTICE.md
@@ -81,14 +81,14 @@ A "contributor" is any person that distributes its contribution under this licen
 
 https://github.com/wayland-project/wayland-protocols
 
-Copyright � 2008-2013 Kristian H�gsberg
-Copyright � 2010-2013 Intel Corporation
-Copyright � 2013      Rafael Antognolli
-Copyright � 2013      Jasper St. Pierre
-Copyright � 2014      Jonas �dahl
-Copyright � 2014      Jason Ekstrand
-Copyright � 2014-2015 Collabora, Ltd.
-Copyright � 2015      Red Hat Inc.
+Copyright © 2008-2013 Kristian Høgsberg
+Copyright © 2010-2013 Intel Corporation
+Copyright © 2013      Rafael Antognolli
+Copyright © 2013      Jasper St. Pierre
+Copyright © 2014      Jonas Ådahl
+Copyright © 2014      Jason Ekstrand
+Copyright © 2014-2015 Collabora, Ltd.
+Copyright © 2015      Red Hat Inc.
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),
@@ -140,7 +140,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 https://github.com/toptensoftware/RichTextKit
 
-Copyright � 2019 Topten Software. All Rights Reserved.
+Copyright © 2019 Topten Software. All Rights Reserved.
 
 Licensed under the Apache License, Version 2.0 (the "License"); you may 
 not use this product except in compliance with the License. You may obtain 
@@ -334,3 +334,31 @@ https://github.com/flutter/flutter
 //ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 //(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 //SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+# Reactive Extensions
+
+https://github.com/dotnet/reactive
+
+The MIT License (MIT)
+
+Copyright (c) .NET Foundation and Contributors
+
+All rights reserved.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
index d1d7b98562..0818b5fa62 100644
--- a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
+++ b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
@@ -104,7 +104,7 @@ namespace Avalonia.Data.Core
         public ExpressionObserver(
             Func<object?> rootGetter,
             ExpressionNode node,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             string? description)
         {
             Description = description;
@@ -171,7 +171,7 @@ namespace Avalonia.Data.Core
         public static ExpressionObserver Create<T, U>(
             Func<T> rootGetter,
             Expression<Func<T, U>> expression,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             bool enableDataValidation = false,
             string? description = null)
         {
diff --git a/src/Avalonia.Base/Reactive/Operators/Sink.cs b/src/Avalonia.Base/Reactive/Operators/Sink.cs
index 7a5d39788e..0fef350acc 100644
--- a/src/Avalonia.Base/Reactive/Operators/Sink.cs
+++ b/src/Avalonia.Base/Reactive/Operators/Sink.cs
@@ -3,6 +3,8 @@ using System.Threading;
 
 namespace Avalonia.Reactive.Operators;
 
+// Code based on https://github.com/dotnet/reactive/blob/main/Rx.NET/Source/src/System.Reactive/Internal/Sink.cs
+
 internal abstract class Sink<TTarget> : IDisposable
 {
     private IDisposable? _upstream;
diff --git a/src/Markup/Avalonia.Markup/Data/BindingBase.cs b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
index 56aa930869..90f312a249 100644
--- a/src/Markup/Avalonia.Markup/Data/BindingBase.cs
+++ b/src/Markup/Avalonia.Markup/Data/BindingBase.cs
@@ -252,9 +252,8 @@ namespace Avalonia.Data
                 }).Switch();
         }
 
-        private class UpdateSignal : SingleSubscriberObservableBase<object>
+        private class UpdateSignal : SingleSubscriberObservableBase<ValueTuple>
         {
-            private static readonly object s_val = new(); 
             private readonly AvaloniaObject _target;
             private readonly AvaloniaProperty _property;
 
@@ -278,7 +277,7 @@ namespace Avalonia.Data
             {
                 if (e.Property == _property)
                 {
-                    PublishNext(s_val);
+                    PublishNext(default);
                 }
             }
         }
diff --git a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
index a478af570a..00f40dfcd3 100644
--- a/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
+++ b/src/Markup/Avalonia.Markup/Markup/Parsers/ExpressionObserverBuilder.cs
@@ -63,7 +63,7 @@ namespace Avalonia.Markup.Parsers
         public static ExpressionObserver Build(
             Func<object> rootGetter,
             string expression,
-            IObservable<object> update,
+            IObservable<ValueTuple> update,
             bool enableDataValidation = false,
             string? description = null,
             Func<string, string, Type>? typeResolver = null)
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
index e6864e6806..612f3ff80a 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Lifetime.cs
@@ -41,7 +41,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Completes()
         {
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -54,7 +54,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         [Fact]
         public void Should_Complete_When_Update_Observable_Errors()
         {
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => 1, o => o, update);
             var completed = false;
 
@@ -87,7 +87,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Should_Unsubscribe_From_Update_Observable()
         {
             var scheduler = new TestScheduler();
-            var update = scheduler.CreateColdObservable<object>();
+            var update = scheduler.CreateColdObservable<ValueTuple>();
             var data = new { Foo = "foo" };
             var target = ExpressionObserver.Create(() => data, o => o.Foo, update);
             var result = new List<object>();
diff --git a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
index 6554be2e89..22d5645f76 100644
--- a/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
+++ b/tests/Avalonia.Base.UnitTests/Data/Core/ExpressionObserverTests_Property.cs
@@ -359,14 +359,14 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void Empty_Expression_Should_Track_Root()
         {
             var data = new Class1 { Foo = "foo" };
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => data.Foo, o => o, update);
             var result = new List<object>();
 
             target.Subscribe(x => result.Add(x));
 
             data.Foo = "bar";
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
 
             Assert.Equal(new[] { "foo", "bar" }, result);
 
@@ -533,15 +533,15 @@ namespace Avalonia.Base.UnitTests.Data.Core
             var first = new Class1 { Foo = "foo" };
             var second = new Class1 { Foo = "bar" };
             var root = first;
-            var update = new Subject<object>();
+            var update = new Subject<ValueTuple>();
             var target = ExpressionObserver.Create(() => root, o => o.Foo, update);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));
 
             root = second;
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
             root = null;
-            update.OnNext(Unit.Default);
+            update.OnNext(default);
 
             Assert.Equal(
                 new object[]
@@ -640,7 +640,7 @@ namespace Avalonia.Base.UnitTests.Data.Core
         public void RootGetter_Is_Reevaluated_On_Subscribe()
         {
             var data = "foo";
-            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<object>(), null);
+            var target = new ExpressionObserver(() => data, new EmptyExpressionNode(), new Subject<ValueTuple>(), null);
             var result = new List<object>();
             var sub = target.Subscribe(x => result.Add(x));
 

From 289b14a48c8737d93cd383ea408f40e75f1e6a7f Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sun, 8 Jan 2023 15:02:43 -0500
Subject: [PATCH 118/157] Apply suggestions from code review

---
 src/Browser/Avalonia.Browser/Interop/DomHelper.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
index 9ee96768ec..d1133b8916 100644
--- a/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
+++ b/src/Browser/Avalonia.Browser/Interop/DomHelper.cs
@@ -29,5 +29,5 @@ internal static partial class DomHelper
     [JSImport("AvaloniaDOM.observeDarkMode", AvaloniaModule.MainModuleName)]
     public static partial JSObject ObserveDarkMode(
         [JSMarshalAs<JSType.Function<JSType.Boolean, JSType.Boolean>>]
-        Action<bool, bool> onDpiChanged);
+        Action<bool, bool> observer);
 }

From 24626da4893f2a48ae61f5a8f0860d1d1f7a7ffb Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Sun, 8 Jan 2023 18:43:06 -0500
Subject: [PATCH 119/157] Remove Rx.props from ControlCatalog and some other
 projects too

---
 samples/ControlCatalog/Pages/MenuPage.xaml.cs      |  1 -
 samples/ControlCatalog/Pages/PointerContactsTab.cs |  1 -
 .../ViewModels/ComboBoxPageViewModel.cs            |  1 -
 .../ViewModels/ContextPageViewModel.cs             |  1 -
 .../ViewModels/ListBoxPageViewModel.cs             |  1 -
 .../ViewModels/MainWindowViewModel.cs              |  2 +-
 .../ControlCatalog/ViewModels/MenuPageViewModel.cs |  2 --
 .../ViewModels/NotificationViewModel.cs            |  3 +--
 .../ViewModels/RefreshContainerViewModel.cs        |  1 -
 .../ViewModels/TreeViewPageViewModel.cs            |  1 -
 samples/MiniMvvm/MiniMvvm.csproj                   |  4 +++-
 samples/MiniMvvm/PropertyChangedExtensions.cs      | 14 ++++++++------
 samples/MiniMvvm/ViewModelBase.cs                  |  1 -
 samples/ReactiveUIDemo/ReactiveUIDemo.csproj       |  1 -
 .../WindowsInteropTest/WindowsInteropTest.csproj   |  2 --
 src/Avalonia.Base/Avalonia.Base.csproj             |  2 ++
 16 files changed, 15 insertions(+), 23 deletions(-)

diff --git a/samples/ControlCatalog/Pages/MenuPage.xaml.cs b/samples/ControlCatalog/Pages/MenuPage.xaml.cs
index 52c122f2bc..32cfa9b22b 100644
--- a/samples/ControlCatalog/Pages/MenuPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/MenuPage.xaml.cs
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.Reactive;
 using System.Threading.Tasks;
 using System.Windows.Input;
 using Avalonia.Controls;
diff --git a/samples/ControlCatalog/Pages/PointerContactsTab.cs b/samples/ControlCatalog/Pages/PointerContactsTab.cs
index b6aabebf99..1751b046c0 100644
--- a/samples/ControlCatalog/Pages/PointerContactsTab.cs
+++ b/samples/ControlCatalog/Pages/PointerContactsTab.cs
@@ -2,7 +2,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Reactive.Linq;
 
 using Avalonia;
 using Avalonia.Controls;
diff --git a/samples/ControlCatalog/ViewModels/ComboBoxPageViewModel.cs b/samples/ControlCatalog/ViewModels/ComboBoxPageViewModel.cs
index bbe970afd6..d3e4ea7c31 100644
--- a/samples/ControlCatalog/ViewModels/ComboBoxPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/ComboBoxPageViewModel.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.ObjectModel;
 using System.Linq;
-using System.Reactive;
 using Avalonia.Controls;
 using Avalonia.Controls.Selection;
 using MiniMvvm;
diff --git a/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs b/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
index 4a5462a58b..f041f32b10 100644
--- a/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/ContextPageViewModel.cs
@@ -1,5 +1,4 @@
 using System.Collections.Generic;
-using System.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.VisualTree;
diff --git a/samples/ControlCatalog/ViewModels/ListBoxPageViewModel.cs b/samples/ControlCatalog/ViewModels/ListBoxPageViewModel.cs
index f89d9d1e20..7f32536b11 100644
--- a/samples/ControlCatalog/ViewModels/ListBoxPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/ListBoxPageViewModel.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.ObjectModel;
 using System.Linq;
-using System.Reactive;
 using Avalonia.Controls;
 using Avalonia.Controls.Selection;
 using ControlCatalog.Pages;
diff --git a/samples/ControlCatalog/ViewModels/MainWindowViewModel.cs b/samples/ControlCatalog/ViewModels/MainWindowViewModel.cs
index 47c6f70714..3628a9b8a7 100644
--- a/samples/ControlCatalog/ViewModels/MainWindowViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/MainWindowViewModel.cs
@@ -1,9 +1,9 @@
-using System.Reactive;
 using Avalonia.Controls;
 using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Controls.Notifications;
 using Avalonia.Dialogs;
 using Avalonia.Platform;
+using Avalonia.Reactive;
 using System;
 using System.ComponentModel.DataAnnotations;
 using MiniMvvm;
diff --git a/samples/ControlCatalog/ViewModels/MenuPageViewModel.cs b/samples/ControlCatalog/ViewModels/MenuPageViewModel.cs
index 16051c3c05..df62ba04cb 100644
--- a/samples/ControlCatalog/ViewModels/MenuPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/MenuPageViewModel.cs
@@ -1,6 +1,4 @@
 using System.Collections.Generic;
-using System.Reactive;
-using System.Reactive.Linq;
 using System.Threading.Tasks;
 using Avalonia.Controls;
 using Avalonia.VisualTree;
diff --git a/samples/ControlCatalog/ViewModels/NotificationViewModel.cs b/samples/ControlCatalog/ViewModels/NotificationViewModel.cs
index a31f164a2a..bcbcb345ef 100644
--- a/samples/ControlCatalog/ViewModels/NotificationViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/NotificationViewModel.cs
@@ -1,5 +1,4 @@
-using System.Reactive;
-using Avalonia.Controls.Notifications;
+using Avalonia.Controls.Notifications;
 using MiniMvvm;
 
 namespace ControlCatalog.ViewModels
diff --git a/samples/ControlCatalog/ViewModels/RefreshContainerViewModel.cs b/samples/ControlCatalog/ViewModels/RefreshContainerViewModel.cs
index d4b43043be..aa15d7758b 100644
--- a/samples/ControlCatalog/ViewModels/RefreshContainerViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/RefreshContainerViewModel.cs
@@ -1,6 +1,5 @@
 using System.Collections.ObjectModel;
 using System.Linq;
-using System.Reactive;
 using System.Threading.Tasks;
 using Avalonia.Controls.Notifications;
 using ControlCatalog.Pages;
diff --git a/samples/ControlCatalog/ViewModels/TreeViewPageViewModel.cs b/samples/ControlCatalog/ViewModels/TreeViewPageViewModel.cs
index 80d4844f7a..7c0855e0af 100644
--- a/samples/ControlCatalog/ViewModels/TreeViewPageViewModel.cs
+++ b/samples/ControlCatalog/ViewModels/TreeViewPageViewModel.cs
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.ObjectModel;
 using System.Linq;
-using System.Reactive;
 using Avalonia.Controls;
 using MiniMvvm;
 
diff --git a/samples/MiniMvvm/MiniMvvm.csproj b/samples/MiniMvvm/MiniMvvm.csproj
index 6535b2bdbd..2a9164624a 100644
--- a/samples/MiniMvvm/MiniMvvm.csproj
+++ b/samples/MiniMvvm/MiniMvvm.csproj
@@ -2,5 +2,7 @@
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
   </PropertyGroup>
-  <Import Project="..\..\build\Rx.props" />
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Avalonia.Base\Avalonia.Base.csproj" />
+  </ItemGroup>
 </Project>
diff --git a/samples/MiniMvvm/PropertyChangedExtensions.cs b/samples/MiniMvvm/PropertyChangedExtensions.cs
index f1065c7530..f51773810d 100644
--- a/samples/MiniMvvm/PropertyChangedExtensions.cs
+++ b/samples/MiniMvvm/PropertyChangedExtensions.cs
@@ -1,8 +1,8 @@
 using System;
 using System.ComponentModel;
 using System.Linq.Expressions;
-using System.Reactive.Linq;
 using System.Reflection;
+using Avalonia.Reactive;
 
 namespace MiniMvvm
 {
@@ -92,11 +92,13 @@ namespace MiniMvvm
             Expression<Func<TModel, T3>> v3,
             Func<T1, T2, T3, TRes> cb
         ) where TModel : INotifyPropertyChanged =>
-            Observable.CombineLatest(
-                model.WhenAnyValue(v1),
-                model.WhenAnyValue(v2),
-                model.WhenAnyValue(v3),
-                cb);
+            model.WhenAnyValue(v1)
+                .CombineLatest(
+                    model.WhenAnyValue(v2),
+                    (l, r) => (l, r))
+                .CombineLatest(
+                    model.WhenAnyValue(v3),
+                    (t, r) => cb(t.l, t.r, r));
 
         public static IObservable<ValueTuple<T1, T2, T3>> WhenAnyValue<TModel, T1, T2, T3>(this TModel model,
             Expression<Func<TModel, T1>> v1,
diff --git a/samples/MiniMvvm/ViewModelBase.cs b/samples/MiniMvvm/ViewModelBase.cs
index 7256b05cef..8bc398607f 100644
--- a/samples/MiniMvvm/ViewModelBase.cs
+++ b/samples/MiniMvvm/ViewModelBase.cs
@@ -1,6 +1,5 @@
 using System.Collections.Generic;
 using System.ComponentModel;
-using System.Reactive.Joins;
 using System.Runtime.CompilerServices;
 
 namespace MiniMvvm
diff --git a/samples/ReactiveUIDemo/ReactiveUIDemo.csproj b/samples/ReactiveUIDemo/ReactiveUIDemo.csproj
index 94ca4ee809..9650068434 100644
--- a/samples/ReactiveUIDemo/ReactiveUIDemo.csproj
+++ b/samples/ReactiveUIDemo/ReactiveUIDemo.csproj
@@ -23,6 +23,5 @@
   <Import Project="..\..\build\SampleApp.props" />
   <Import Project="..\..\build\ReferenceCoreLibraries.props" />
   <Import Project="..\..\build\BuildTargets.targets" />
-  <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\ReactiveUI.props" />
 </Project>
diff --git a/samples/interop/WindowsInteropTest/WindowsInteropTest.csproj b/samples/interop/WindowsInteropTest/WindowsInteropTest.csproj
index 223a53d8c5..1643ca3ee2 100644
--- a/samples/interop/WindowsInteropTest/WindowsInteropTest.csproj
+++ b/samples/interop/WindowsInteropTest/WindowsInteropTest.csproj
@@ -15,6 +15,4 @@
       <Name>ControlCatalog</Name>
     </ProjectReference>
   </ItemGroup>
-
-  <Import Project="..\..\..\build\Rx.props" />
 </Project>
diff --git a/src/Avalonia.Base/Avalonia.Base.csproj b/src/Avalonia.Base/Avalonia.Base.csproj
index 1e02d6a8f3..cd122a8b67 100644
--- a/src/Avalonia.Base/Avalonia.Base.csproj
+++ b/src/Avalonia.Base/Avalonia.Base.csproj
@@ -58,6 +58,8 @@
     <InternalsVisibleTo Include="Avalonia.iOS, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Dialogs, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="Avalonia.Diagnostics, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="MiniMvvm, PublicKey=$(AvaloniaPublicKey)" />
+    <InternalsVisibleTo Include="ControlCatalog, PublicKey=$(AvaloniaPublicKey)" />
     <InternalsVisibleTo Include="DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7" />
   </ItemGroup>
   

From a5ee7ebde83a06ccfcd229ffd26c05ee3e18934f Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Mon, 9 Jan 2023 13:59:42 +0100
Subject: [PATCH 120/157] Resolve conflicts

---
 .../TextFormatting/CharacterBufferRange.cs    |  11 +-
 .../Media/TextFormatting/TextFormatterImpl.cs | 150 +++++++++---------
 .../TextLeadingPrefixCharacterEllipsis.cs     |   2 +-
 .../Media/TextFormatting/TextLineImpl.cs      |   4 +-
 .../Media/TextFormatting/TextRun.cs           |   2 +-
 5 files changed, 87 insertions(+), 82 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
index f5d39e4371..499026e8b3 100644
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
@@ -140,7 +140,7 @@ namespace Avalonia.Media.TextFormatting
                     throw new ArgumentOutOfRangeException(nameof(index));
                 }
 #endif
-                return CharacterBufferReference.CharacterBuffer.Span[CharacterBufferReference.OffsetToFirstChar + index];
+                return CharacterBuffer.Span[CharacterBufferReference.OffsetToFirstChar + index];
             }
         }
 
@@ -157,8 +157,7 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Gets a span from the character buffer range
         /// </summary>
-        public ReadOnlySpan<char> Span =>
-            CharacterBufferReference.CharacterBuffer.Span.Slice(CharacterBufferReference.OffsetToFirstChar, Length);
+        public ReadOnlySpan<char> Span => CharacterBuffer.Span.Slice(OffsetToFirstChar, Length);
 
         /// <summary>
         /// Gets the character memory buffer
@@ -174,7 +173,7 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Indicate whether the character buffer range is empty
         /// </summary>
-        internal bool IsEmpty => CharacterBufferReference.CharacterBuffer.Length == 0 || Length <= 0;
+        internal bool IsEmpty => CharacterBuffer.Length == 0 || Length <= 0;
 
         internal CharacterBufferRange Take(int length)
         {
@@ -208,9 +207,7 @@ namespace Avalonia.Media.TextFormatting
                 return new CharacterBufferRange(new CharacterBufferReference(), 0);
             }
 
-            var characterBufferReference = new CharacterBufferReference(
-                CharacterBufferReference.CharacterBuffer,
-                CharacterBufferReference.OffsetToFirstChar + length);
+            var characterBufferReference = new CharacterBufferReference(CharacterBuffer, OffsetToFirstChar + length);
 
             return new CharacterBufferRange(characterBufferReference, Length - length);
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
index 544800ecea..989bf7749d 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
@@ -130,7 +130,7 @@ namespace Avalonia.Media.TextFormatting
                         first.Add(split.First);
 
                         second.Add(split.Second!);
-                    }                
+                    }
 
                     for (var j = 1; j < secondCount; j++)
                     {
@@ -237,7 +237,7 @@ namespace Avalonia.Media.TextFormatting
 
                             var shaperOptions = new TextShaperOptions(currentRun.Properties!.Typeface.GlyphTypeface,
                                         currentRun.Properties.FontRenderingEmSize,
-                                         shapeableRun.BidiLevel, currentRun.Properties.CultureInfo, 
+                                         shapeableRun.BidiLevel, currentRun.Properties.CultureInfo,
                                          paragraphProperties.DefaultIncrementalTab, paragraphProperties.LetterSpacing);
 
                             shapedRuns.AddRange(ShapeTogether(groupedRuns, characterBufferReference, length, shaperOptions));
@@ -478,7 +478,7 @@ namespace Avalonia.Media.TextFormatting
                 {
                     case ShapedTextRun shapedTextCharacters:
                         {
-                            if(shapedTextCharacters.ShapedBuffer.Length > 0)
+                            if (shapedTextCharacters.ShapedBuffer.Length > 0)
                             {
                                 var firstCluster = shapedTextCharacters.ShapedBuffer.GlyphInfos[0].GlyphCluster;
                                 var lastCluster = firstCluster;
@@ -499,7 +499,7 @@ namespace Avalonia.Media.TextFormatting
                                 }
 
                                 measuredLength += currentRun.Length;
-                            }                         
+                            }
 
                             break;
                         }
@@ -525,7 +525,7 @@ namespace Avalonia.Media.TextFormatting
                 }
             }
 
-            found:
+        found:
 
             return measuredLength != 0;
         }
@@ -565,9 +565,9 @@ namespace Avalonia.Media.TextFormatting
             double paragraphWidth, TextParagraphProperties paragraphProperties, FlowDirection resolvedFlowDirection,
             TextLineBreak? currentLineBreak)
         {
-            if(textRuns.Count == 0)
+            if (textRuns.Count == 0)
             {
-                return CreateEmptyTextLine(firstTextSourceIndex,paragraphWidth, paragraphProperties);
+                return CreateEmptyTextLine(firstTextSourceIndex, paragraphWidth, paragraphProperties);
             }
 
             if (!TryMeasureLength(textRuns, paragraphWidth, out var measuredLength))
@@ -583,46 +583,24 @@ namespace Avalonia.Media.TextFormatting
 
             for (var index = 0; index < textRuns.Count; index++)
             {
-                var currentRun = textRuns[index];
-
-                var runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
-
-                var lineBreaker = new LineBreakEnumerator(runText);
-
                 var breakFound = false;
 
-                while (lineBreaker.MoveNext())
-                {
-                    if (lineBreaker.Current.Required &&
-                        currentLength + lineBreaker.Current.PositionMeasure <= measuredLength)
-                    {
-                        //Explicit break found
-                        breakFound = true;
-
-                        currentPosition = currentLength + lineBreaker.Current.PositionWrap;
-
-                        break;
-                    }
+                var currentRun = textRuns[index];
 
-                    if (currentLength + lineBreaker.Current.PositionMeasure > measuredLength)
-                    {
-                        if (paragraphProperties.TextWrapping == TextWrapping.WrapWithOverflow)
+                switch (currentRun)
+                {
+                    case ShapedTextRun:
                         {
-                            if (lastWrapPosition > 0)
-                            {
-                                currentPosition = lastWrapPosition;
+                            var runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
 
-                                breakFound = true;
+                            var lineBreaker = new LineBreakEnumerator(runText);
 
-                                break;
-                            }
-
-                            //Find next possible wrap position (overflow)
-                            if (index < textRuns.Count - 1)
+                            while (lineBreaker.MoveNext())
                             {
-                                if (lineBreaker.Current.PositionWrap != currentRun.Length)
+                                if (lineBreaker.Current.Required &&
+                                    currentLength + lineBreaker.Current.PositionMeasure <= measuredLength)
                                 {
-                                    //We already found the next possible wrap position.
+                                    //Explicit break found
                                     breakFound = true;
 
                                     currentPosition = currentLength + lineBreaker.Current.PositionWrap;
@@ -630,51 +608,81 @@ namespace Avalonia.Media.TextFormatting
                                     break;
                                 }
 
-                                while (lineBreaker.MoveNext() && index < textRuns.Count)
+                                if (currentLength + lineBreaker.Current.PositionMeasure > measuredLength)
                                 {
-                                    currentPosition += lineBreaker.Current.PositionWrap;
-
-                                    if (lineBreaker.Current.PositionWrap != currentRun.Length)
+                                    if (paragraphProperties.TextWrapping == TextWrapping.WrapWithOverflow)
                                     {
-                                        break;
-                                    }
+                                        if (lastWrapPosition > 0)
+                                        {
+                                            currentPosition = lastWrapPosition;
 
-                                    index++;
+                                            breakFound = true;
+
+                                            break;
+                                        }
+
+                                        //Find next possible wrap position (overflow)
+                                        if (index < textRuns.Count - 1)
+                                        {
+                                            if (lineBreaker.Current.PositionWrap != currentRun.Length)
+                                            {
+                                                //We already found the next possible wrap position.
+                                                breakFound = true;
+
+                                                currentPosition = currentLength + lineBreaker.Current.PositionWrap;
+
+                                                break;
+                                            }
+
+                                            while (lineBreaker.MoveNext() && index < textRuns.Count)
+                                            {
+                                                currentPosition += lineBreaker.Current.PositionWrap;
+
+                                                if (lineBreaker.Current.PositionWrap != currentRun.Length)
+                                                {
+                                                    break;
+                                                }
+
+                                                index++;
+
+                                                if (index >= textRuns.Count)
+                                                {
+                                                    break;
+                                                }
+
+                                                currentRun = textRuns[index];
+
+                                                runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
+
+                                                lineBreaker = new LineBreakEnumerator(runText);
+                                            }
+                                        }
+                                        else
+                                        {
+                                            currentPosition = currentLength + lineBreaker.Current.PositionWrap;
+                                        }
+
+                                        breakFound = true;
 
-                                    if (index >= textRuns.Count)
-                                    {
                                         break;
                                     }
 
-                                    currentRun = textRuns[index];
+                                    //We overflowed so we use the last available wrap position.
+                                    currentPosition = lastWrapPosition == 0 ? measuredLength : lastWrapPosition;
 
-                                    runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
+                                    breakFound = true;
 
-                                    lineBreaker = new LineBreakEnumerator(runText);
+                                    break;
                                 }
-                            }
-                            else
-                            {
-                                currentPosition = currentLength + lineBreaker.Current.PositionWrap;
-                            }
 
-                            breakFound = true;
+                                if (lineBreaker.Current.PositionMeasure != lineBreaker.Current.PositionWrap)
+                                {
+                                    lastWrapPosition = currentLength + lineBreaker.Current.PositionWrap;
+                                }
+                            }
 
                             break;
                         }
-
-                        //We overflowed so we use the last available wrap position.
-                        currentPosition = lastWrapPosition == 0 ? measuredLength : lastWrapPosition;
-
-                        breakFound = true;
-
-                        break;
-                    }
-
-                    if (lineBreaker.Current.PositionMeasure != lineBreaker.Current.PositionWrap)
-                    {
-                        lastWrapPosition = currentLength + lineBreaker.Current.PositionWrap;
-                    }
                 }
 
                 if (!breakFound)
@@ -694,7 +702,7 @@ namespace Avalonia.Media.TextFormatting
             var remainingCharacters = splitResult.Second;
 
             var lineBreak = remainingCharacters?.Count > 0 ?
-                new TextLineBreak(currentLineBreak?.TextEndOfLine, resolvedFlowDirection, remainingCharacters) :
+                new TextLineBreak(null, resolvedFlowDirection, remainingCharacters) :
                 null;
 
             if (lineBreak is null && currentLineBreak?.TextEndOfLine != null)
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs b/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
index 42a84ec137..e30a0fe9f4 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLeadingPrefixCharacterEllipsis.cs
@@ -123,7 +123,7 @@ namespace Avalonia.Media.TextFormatting
 
                                         switch (run)
                                         {
-                                            case ShapedTextCharacters endShapedRun:
+                                            case ShapedTextRun endShapedRun:
                                                 {
                                                     if (endShapedRun.TryMeasureCharactersBackwards(availableSuffixWidth,
                                                             out var suffixCount, out var suffixWidth))
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index 5a71bde522..a1f93bcd07 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -230,12 +230,12 @@ namespace Avalonia.Media.TextFormatting
 
                         currentRun = _textRuns[j];
 
-                        if(currentRun is not ShapedTextCharacters)
+                        if(currentRun is not ShapedTextRun)
                         {
                             continue;
                         }
 
-                        shapedRun = (ShapedTextCharacters)currentRun;
+                        shapedRun = (ShapedTextRun)currentRun;
 
                         if (currentDistance + shapedRun.Size.Width <= distance)
                         {
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
index 21f85b898f..56232ec9c8 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
@@ -44,7 +44,7 @@ namespace Avalonia.Media.TextFormatting
 
                         fixed (char* charsPtr = characterBuffer.Span)
                         {
-                            return new string(charsPtr, _textRun.CharacterBufferReference.OffsetToFirstChar, _textRun.Length);
+                            return new string(charsPtr, 0, _textRun.Length);
                         }
                     }
                 }

From 182e469066a3da780bd8c50777127fb0fad8ebf8 Mon Sep 17 00:00:00 2001
From: rabbitism <popmessiah@hotmail.com>
Date: Mon, 9 Jan 2023 23:51:18 +0800
Subject: [PATCH 121/157] feat: add UT for GeometryTypeConverter.

---
 src/Avalonia.Base/Media/Geometry.cs           |  4 +-
 .../Converters/GeometryTypeConverterTests.cs  | 54 +++++++++++++++++++
 2 files changed, 56 insertions(+), 2 deletions(-)
 create mode 100644 tests/Avalonia.Markup.Xaml.UnitTests/Converters/GeometryTypeConverterTests.cs

diff --git a/src/Avalonia.Base/Media/Geometry.cs b/src/Avalonia.Base/Media/Geometry.cs
index e2b345df1a..e62f819b74 100644
--- a/src/Avalonia.Base/Media/Geometry.cs
+++ b/src/Avalonia.Base/Media/Geometry.cs
@@ -8,7 +8,7 @@ namespace Avalonia.Media
     /// <summary>
     /// Defines a geometric shape.
     /// </summary>
-    [TypeConverter(typeof(GeometryConverter))]
+    [TypeConverter(typeof(GeometryTypeConverter))]
     public abstract class Geometry : AvaloniaObject
     {
         /// <summary>
@@ -203,7 +203,7 @@ namespace Avalonia.Media
         }
     }
 
-    public class GeometryConverter : TypeConverter
+    public class GeometryTypeConverter : TypeConverter
     {
         public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
         {
diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Converters/GeometryTypeConverterTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Converters/GeometryTypeConverterTests.cs
new file mode 100644
index 0000000000..329a14afa6
--- /dev/null
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Converters/GeometryTypeConverterTests.cs
@@ -0,0 +1,54 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Avalonia.Controls;
+using Avalonia.Controls.Shapes;
+using Avalonia.Media;
+using Avalonia.UnitTests;
+using Xunit;
+
+namespace Avalonia.Markup.Xaml.UnitTests.Converters
+{
+    public class GeometryTypeConverterTests: XamlTestBase
+    {
+        public class StringDataViewModel
+        {
+            public string PathData { get; set; } 
+        }
+
+        public class IntDataViewModel
+        {
+            public int PathData { get; set; }
+        }
+
+
+        [Theory]
+        [MemberData(nameof(Get_GeometryTypeConverter_Data))]
+        public void GeometryTypeConverter_Value_Work(object vm, bool nullData)
+        {
+            using(UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:c='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Converters;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Path Name='path' Data='{Binding PathData}' Height='10' Width='10'/>
+</Window>";
+                var window = (Window)AvaloniaRuntimeXamlLoader.Load(xaml);
+                var path = window.FindControl<Path>("path");
+                window.DataContext = vm;
+                Assert.Equal(nullData, path.Data is null);
+            }
+        }
+
+        public static IEnumerable<object[]> Get_GeometryTypeConverter_Data()
+        {
+            yield return new object[] { new StringDataViewModel { }, true };
+            yield return new object[] { new StringDataViewModel { PathData = "M406.39,333.45l205.93,0" }, false };
+            yield return new object[] { new IntDataViewModel { }, true };
+            yield return new object[] { new IntDataViewModel { PathData = 100 }, true };
+        }
+    }
+}

From 0dcf836a9058e2ea7c4c33d1560c22cc4651bfd2 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 9 Jan 2023 17:02:38 +0100
Subject: [PATCH 122/157] Remove debug code.

---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6dec8c6327..c3bf7a3e5d 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -533,7 +533,6 @@ namespace Avalonia.Controls
                 _recyclePool ??= new();
                 _recyclePool.Push(element);
                 element.IsVisible = false;
-                element.GetObservable(Visual.VisualParentProperty).Subscribe(x => { });
             }
         }
 

From 1ef4df181b299278a60600ee75a9114314f99e8a Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Mon, 9 Jan 2023 17:05:50 +0100
Subject: [PATCH 123/157] Fix nits.

---
 src/Avalonia.Controls/Generators/ItemContainerGenerator.cs | 2 +-
 src/Avalonia.Controls/VirtualizingStackPanel.cs            | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
index b6f54d51eb..57ed67b508 100644
--- a/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
+++ b/src/Avalonia.Controls/Generators/ItemContainerGenerator.cs
@@ -29,7 +29,7 @@ namespace Avalonia.Controls.Generators
     /// </remarks>
     public class ItemContainerGenerator
     {
-        private ItemsControl _owner;
+        private readonly ItemsControl _owner;
 
         internal ItemContainerGenerator(ItemsControl owner) => _owner = owner;
 
diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index c3bf7a3e5d..6c88e6e441 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -127,7 +127,7 @@ namespace Avalonia.Controls
                 {
                     var e = _realizedElements.Elements[i];
 
-                    if (e is object)
+                    if (e is not null)
                     {
                         var sizeU = _realizedElements.SizeU[i];
                         var rect = orientation == Orientation.Horizontal ?
@@ -375,7 +375,7 @@ namespace Avalonia.Controls
 
             while (c is not null)
             {
-                if (!c.Bounds.IsEmpty && c.TransformToVisual(this) is Matrix transform)
+                if (!c.Bounds.IsDefault && c.TransformToVisual(this) is Matrix transform)
                 {
                     viewport = new Rect(0, 0, c.Bounds.Width, c.Bounds.Height)
                         .TransformToAABB(transform);
@@ -990,7 +990,7 @@ namespace Avalonia.Controls
 
                 foreach (var e in _elements)
                 {
-                    if (e is object)
+                    if (e is not null)
                         recycleElement(e);
                 }
 

From 9d075fe2a9ead45840670b2f13b322416ed626c1 Mon Sep 17 00:00:00 2001
From: Simon Cropp <simon.cropp@gmail.com>
Date: Tue, 10 Jan 2023 07:49:29 +1100
Subject: [PATCH 124/157] Update ControlTemplateTests.cs

---
 .../Xaml/ControlTemplateTests.cs                          | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
index 6c29707dcd..396a03645c 100644
--- a/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
+++ b/tests/Avalonia.Markup.Xaml.UnitTests/Xaml/ControlTemplateTests.cs
@@ -27,11 +27,11 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
     <Button>
         <Button.Template>
             <ControlTemplate>
-                <controls:ListBoxHierachyLine>
-                    <controls:ListBoxHierachyLine.LineDashStyle>
+                <controls:ListBoxHierarchyLine>
+                    <controls:ListBoxHierarchyLine.LineDashStyle>
                         <DashStyle Dashes=""2,2"" Offset=""1"" />
-                    </controls:ListBoxHierachyLine.LineDashStyle>
-                </controls:ListBoxHierachyLine>
+                    </controls:ListBoxHierarchyLine.LineDashStyle>
+                </controls:ListBoxHierarchyLine>
             </ControlTemplate>
         </Button.Template>
     </Button>

From ba90d9ab98422d40d99a4f1a6dd48c417761c150 Mon Sep 17 00:00:00 2001
From: Julien Lebosquain <julien@lebosquain.net>
Date: Tue, 10 Jan 2023 01:03:51 +0100
Subject: [PATCH 125/157] Clean/Rebuild removes old resources cache from obj
 folder

---
 packages/Avalonia/AvaloniaBuildTasks.targets  | 25 +++++++++++++----
 .../CompileAvaloniaXamlTask.cs                | 28 ++++++++++++++++---
 2 files changed, 44 insertions(+), 9 deletions(-)

diff --git a/packages/Avalonia/AvaloniaBuildTasks.targets b/packages/Avalonia/AvaloniaBuildTasks.targets
index ca2d4b66ed..33f22f4d02 100644
--- a/packages/Avalonia/AvaloniaBuildTasks.targets
+++ b/packages/Avalonia/AvaloniaBuildTasks.targets
@@ -48,8 +48,12 @@
   </PropertyGroup>
 
   <Target Name="_GenerateAvaloniaResourcesDependencyCache" BeforeTargets="GenerateAvaloniaResources">
+    <PropertyGroup>
+      <_AvaloniaResourcesInputsCacheFilePath>$(IntermediateOutputPath)/Avalonia/Resources.Inputs.cache</_AvaloniaResourcesInputsCacheFilePath>
+    </PropertyGroup>
+
     <ItemGroup>
-      <CustomAdditionalGenerateAvaloniaResourcesInputs Include="$(IntermediateOutputPath)/Avalonia/Resources.Inputs.cache" />
+      <CustomAdditionalGenerateAvaloniaResourcesInputs Include="$(_AvaloniaResourcesInputsCacheFilePath)" />
     </ItemGroup>
     
     <Hash ItemsToHash="@(AvaloniaResource);@(AvaloniaXaml);$(MSBuildAllProjects)">
@@ -57,7 +61,11 @@
     </Hash>
 
     <MakeDir Directories="$(IntermediateOutputPath)/Avalonia" />
-    <WriteLinesToFile Overwrite="true" File="$(IntermediateOutputPath)/Avalonia/Resources.Inputs.cache" Lines="$(AvaloniaResourcesDependencyHash)" WriteOnlyWhenDifferent="True" />
+    <WriteLinesToFile Overwrite="true" File="$(_AvaloniaResourcesInputsCacheFilePath)" Lines="$(AvaloniaResourcesDependencyHash)" WriteOnlyWhenDifferent="True" />
+
+    <ItemGroup>
+      <FileWrites Include="$(_AvaloniaResourcesInputsCacheFilePath)" />
+    </ItemGroup>
   </Target>
   
   <Target Name="GenerateAvaloniaResources" 
@@ -68,7 +76,7 @@
           Condition="('@(AvaloniaResource->Count())' &gt; 0) or ('@(AvaloniaXaml->Count())' &gt; 0)"
           >
     <ItemGroup>
-        <AvaloniaResource Include="@(AvaloniaXaml)"/>
+      <AvaloniaResource Include="@(AvaloniaXaml)" />
     </ItemGroup>
     <GenerateAvaloniaResourcesTask
       Condition="'$(_AvaloniaUseExternalMSBuild)' != 'true'"
@@ -76,6 +84,9 @@
       Root="$(MSBuildProjectDirectory)"
       Resources="@(AvaloniaResource)"
       ReportImportance="$(AvaloniaXamlReportImportance)"/>
+    <ItemGroup Condition="'$(_AvaloniaUseExternalMSBuild)' != 'true'">
+      <FileWrites Include="$(AvaloniaResourcesTemporaryFilePath)" />
+    </ItemGroup>
     <Exec 
       Condition="'$(_AvaloniaUseExternalMSBuild)' == 'true'"
       Command="dotnet msbuild /nodereuse:false $(MSBuildProjectFile) /t:GenerateAvaloniaResources /p:_AvaloniaForceInternalMSBuild=true /p:Configuration=$(Configuration) /p:TargetFramework=$(TargetFramework) /p:RuntimeIdentifier=$(RuntimeIdentifier) /p:BuildProjectReferences=false"/>
@@ -103,6 +114,9 @@
       File="$(AvaloniaXamlReferencesTemporaryFilePath)"
       Lines="@(ReferencePathWithRefAssemblies)"
       Overwrite="true" />
+    <ItemGroup Condition="'$(_AvaloniaForceInternalMSBuild)' != 'true'">
+      <FileWrites Include="$(AvaloniaXamlReferencesTemporaryFilePath)" />
+    </ItemGroup>
     <CompileAvaloniaXamlTask
       Condition="'$(_AvaloniaUseExternalMSBuild)' != 'true'"
       AssemblyFile="@(IntermediateAssembly)"
@@ -117,8 +131,9 @@
       DelaySign="$(DelaySign)"
       SkipXamlCompilation="$(_AvaloniaSkipXamlCompilation)"
       DebuggerLaunch="$(AvaloniaXamlIlDebuggerLaunch)"
-      DefaultCompileBindings="$(AvaloniaUseCompiledBindingsByDefault)"
-    />
+      DefaultCompileBindings="$(AvaloniaUseCompiledBindingsByDefault)">
+      <Output TaskParameter="WrittenFilePaths" ItemName="FileWrites" />
+    </CompileAvaloniaXamlTask>
     <Exec
       Condition="'$(_AvaloniaUseExternalMSBuild)' == 'true'"
       Command="dotnet msbuild /nodereuse:false $(MSBuildProjectFile) /t:CompileAvaloniaXaml /p:_AvaloniaForceInternalMSBuild=true /p:Configuration=$(Configuration) /p:TargetFramework=$(TargetFramework) /p:RuntimeIdentifier=$(RuntimeIdentifier) /p:BuildProjectReferences=false"/>
diff --git a/src/Avalonia.Build.Tasks/CompileAvaloniaXamlTask.cs b/src/Avalonia.Build.Tasks/CompileAvaloniaXamlTask.cs
index fd07e0a143..3bd1ce5ce7 100644
--- a/src/Avalonia.Build.Tasks/CompileAvaloniaXamlTask.cs
+++ b/src/Avalonia.Build.Tasks/CompileAvaloniaXamlTask.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using Microsoft.Build.Framework;
@@ -10,9 +11,10 @@ namespace Avalonia.Build.Tasks
         public bool Execute()
         {
             Enum.TryParse(ReportImportance, true, out MessageImportance outputImportance);
+            var writtenFilePaths = new List<string>();
 
-            OutputPath = OutputPath ?? AssemblyFile;
-            RefOutputPath = RefOutputPath ?? RefAssemblyFile;
+            OutputPath ??= AssemblyFile;
+            RefOutputPath ??= RefAssemblyFile;
             var outputPdb = GetPdbPath(OutputPath);
             var input = AssemblyFile;
             var refInput = RefOutputPath;
@@ -21,8 +23,9 @@ namespace Avalonia.Build.Tasks
             if (OriginalCopyPath != null)
             {
                 var originalCopyPathRef = Path.ChangeExtension(OriginalCopyPath, ".ref.dll");
-                
+
                 File.Copy(AssemblyFile, OriginalCopyPath, true);
+                writtenFilePaths.Add(OriginalCopyPath);
                 input = OriginalCopyPath;
                 File.Delete(AssemblyFile);
 
@@ -30,6 +33,7 @@ namespace Avalonia.Build.Tasks
                 {
                     var copyPdb = GetPdbPath(OriginalCopyPath);
                     File.Copy(inputPdb, copyPdb, true);
+                    writtenFilePaths.Add(copyPdb);
                     File.Delete(inputPdb);
                     inputPdb = copyPdb;
                 }
@@ -39,6 +43,7 @@ namespace Avalonia.Build.Tasks
                     // We also copy ref assembly just for case if needed later for testing.
                     // But do not remove the original one, as MSBuild actually complains about it with multi-thread compiling.
                     File.Copy(RefAssemblyFile, originalCopyPathRef, true);
+                    writtenFilePaths.Add(originalCopyPathRef);
                     refInput = originalCopyPathRef;
                 }
             }
@@ -53,13 +58,25 @@ namespace Avalonia.Build.Tasks
                 ProjectDirectory, VerifyIl, DefaultCompileBindings, outputImportance,
                 (SignAssembly && !DelaySign) ? AssemblyOriginatorKeyFile : null, SkipXamlCompilation, DebuggerLaunch);
             if (!res.Success)
+            {
+                WrittenFilePaths = writtenFilePaths.ToArray();
                 return false;
+            }
+
             if (!res.WrittenFile)
             {
                 File.Copy(input, OutputPath, true);
-                if(File.Exists(inputPdb))
+                if (File.Exists(inputPdb))
                     File.Copy(inputPdb, outputPdb, true);
             }
+            else if (!string.IsNullOrWhiteSpace(RefOutputPath) && File.Exists(RefOutputPath))
+                writtenFilePaths.Add(RefOutputPath);
+
+            writtenFilePaths.Add(OutputPath);
+            if (File.Exists(outputPdb))
+                writtenFilePaths.Add(outputPdb);
+
+            WrittenFilePaths = writtenFilePaths.ToArray();
             return true;
         }
 
@@ -103,5 +120,8 @@ namespace Avalonia.Build.Tasks
         public ITaskHost HostObject { get; set; }
 
         public bool DebuggerLaunch { get; set; }
+
+        [Output]
+        public string[] WrittenFilePaths { get; private set; } = Array.Empty<string>();
     }
 }

From b8a4de969dd6024f75d5d1a09fa51e20a02faaff Mon Sep 17 00:00:00 2001
From: Julien Lebosquain <julien@lebosquain.net>
Date: Tue, 10 Jan 2023 13:55:34 +0100
Subject: [PATCH 126/157] Made resources index binary

Effectively removes System.Xml.Linq dependency
---
 .../Platform/Internal/AssemblyDescriptor.cs   |   2 +-
 .../Utilities/AvaloniaResourcesIndex.cs       | 149 ++++++++++--------
 .../Avalonia.Build.Tasks.csproj               |   3 +
 .../GenerateAvaloniaResourcesTask.cs          |  26 +--
 .../XamlCompilerTaskExecutor.Helpers.cs       |  21 ++-
 5 files changed, 103 insertions(+), 98 deletions(-)

diff --git a/src/Avalonia.Base/Platform/Internal/AssemblyDescriptor.cs b/src/Avalonia.Base/Platform/Internal/AssemblyDescriptor.cs
index df2a26ddd3..467cd530fc 100644
--- a/src/Avalonia.Base/Platform/Internal/AssemblyDescriptor.cs
+++ b/src/Avalonia.Base/Platform/Internal/AssemblyDescriptor.cs
@@ -32,7 +32,7 @@ internal class AssemblyDescriptor : IAssemblyDescriptor
                     Resources.Remove(Constants.AvaloniaResourceName);
 
                     var indexLength = new BinaryReader(resources).ReadInt32();
-                    var index = AvaloniaResourcesIndexReaderWriter.Read(new SlicedStream(resources, 4, indexLength));
+                    var index = AvaloniaResourcesIndexReaderWriter.ReadIndex(new SlicedStream(resources, 4, indexLength));
                     var baseOffset = indexLength + 4;
                     AvaloniaResources = index.ToDictionary(r => GetPathRooted(r), r => (IAssetDescriptor)
                         new AvaloniaResourceDescriptor(assembly, baseOffset + r.Offset, r.Size));
diff --git a/src/Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs b/src/Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs
index 5235e23e08..3c7e82f080 100644
--- a/src/Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs
+++ b/src/Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs
@@ -1,105 +1,116 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-using System.Runtime.Serialization;
-using System.Xml.Linq;
-using System.Linq;
-using System.Diagnostics.CodeAnalysis;
+using System.Text;
 
 namespace Avalonia.Utilities
 {
-    #if !BUILDTASK
+#if !BUILDTASK
     public
-    #endif
+#endif
     static class AvaloniaResourcesIndexReaderWriter
     {
-        private const int LastKnownVersion = 1;
-        public static List<AvaloniaResourcesIndexEntry> Read(Stream stream)
+        private const int XmlLegacyVersion = 1;
+        private const int BinaryCurrentVersion = 2;
+
+        public static List<AvaloniaResourcesIndexEntry> ReadIndex(Stream stream)
         {
-            var ver = new BinaryReader(stream).ReadInt32();
-            if (ver > LastKnownVersion)
-                throw new Exception("Resources index format version is not known");
-
-            var assetDoc = XDocument.Load(stream);
-            XNamespace assetNs = assetDoc.Root!.Attribute("xmlns")!.Value;
-            List<AvaloniaResourcesIndexEntry> entries =         
-                (from entry in assetDoc.Root.Element(assetNs + "Entries")!.Elements(assetNs + "AvaloniaResourcesIndexEntry")
-                    select new AvaloniaResourcesIndexEntry
-                    {
-                        Path = entry.Element(assetNs + "Path")!.Value,
-                        Offset = int.Parse(entry.Element(assetNs + "Offset")!.Value),
-                        Size = int.Parse(entry.Element(assetNs + "Size")!.Value)                     
-                    }).ToList();
+            using var reader = new BinaryReader(stream, Encoding.UTF8, leaveOpen: true);
 
-            return entries;
+            var version = reader.ReadInt32();
+            return version switch
+            {
+                XmlLegacyVersion => ReadXmlIndex(),
+                BinaryCurrentVersion => ReadBinaryIndex(reader),
+                _ => throw new Exception($"Unknown resources index format version {version}")
+            };
         }
 
-        [RequiresUnreferencedCode("AvaloniaResources uses Data Contract Serialization, which might require unreferenced code")]
-        public static void Write(Stream stream, List<AvaloniaResourcesIndexEntry> entries)
+        private static List<AvaloniaResourcesIndexEntry> ReadXmlIndex()
+            => throw new NotSupportedException("Found legacy resources index format: please recompile your XAML files");
+
+        private static List<AvaloniaResourcesIndexEntry> ReadBinaryIndex(BinaryReader reader)
         {
-            new BinaryWriter(stream).Write(LastKnownVersion);
-            new DataContractSerializer(typeof(AvaloniaResourcesIndex)).WriteObject(stream,
-                new AvaloniaResourcesIndex()
-                {
-                    Entries = entries
+            var entryCount = reader.ReadInt32();
+            var entries = new List<AvaloniaResourcesIndexEntry>(entryCount);
+
+            for (var i = 0; i < entryCount; ++i)
+            {
+                entries.Add(new AvaloniaResourcesIndexEntry {
+                    Path = reader.ReadString(),
+                    Offset = reader.ReadInt32(),
+                    Size = reader.ReadInt32()
                 });
+            }
+
+            return entries;
         }
 
-        [RequiresUnreferencedCode("AvaloniaResources uses Data Contract Serialization, which might require unreferenced code")]
-        public static byte[] Create(Dictionary<string, byte[]> data)
+        public static void WriteIndex(Stream output, List<AvaloniaResourcesIndexEntry> entries)
         {
-            var sources = data.ToList();
-            var offsets = new Dictionary<string, int>();
-            var coffset = 0;
-            foreach (var s in sources)
+            using var writer = new BinaryWriter(output, Encoding.UTF8, leaveOpen: true);
+
+            WriteIndex(writer, entries);
+        }
+
+        private static void WriteIndex(BinaryWriter writer, List<AvaloniaResourcesIndexEntry> entries)
+        {
+            writer.Write(BinaryCurrentVersion);
+            writer.Write(entries.Count);
+
+            foreach (var entry in entries)
             {
-                offsets[s.Key] = coffset;
-                coffset += s.Value.Length;
+                writer.Write(entry.Path ?? string.Empty);
+                writer.Write(entry.Offset);
+                writer.Write(entry.Size);
             }
-            var index = sources.Select(s => new AvaloniaResourcesIndexEntry
-            {
-                Path = s.Key,
-                Size = s.Value.Length,
-                Offset = offsets[s.Key]
-            }).ToList();
-            var output = new MemoryStream();
-            var ms = new MemoryStream();
-            AvaloniaResourcesIndexReaderWriter.Write(ms, index);
-            new BinaryWriter(output).Write((int)ms.Length);
-            ms.Position = 0;
-            ms.CopyTo(output);
-            foreach (var s in sources)
+        }
+
+        public static void WriteResources(Stream output, List<(string Path, int Size, Func<Stream> Open)> resources)
+        {
+            var entries = new List<AvaloniaResourcesIndexEntry>(resources.Count);
+            var offset = 0;
+
+            foreach (var resource in resources)
             {
-                output.Write(s.Value,0,s.Value.Length);
+                entries.Add(new AvaloniaResourcesIndexEntry
+                {
+                    Path = resource.Path,
+                    Offset = offset,
+                    Size = resource.Size
+                });
+                offset += resource.Size;
             }
 
-            return output.ToArray();
-        }
-    }
+            using var writer = new BinaryWriter(output, Encoding.UTF8, leaveOpen: true);
+            writer.Write(0); // index size placeholder, overwritten below
 
-    [DataContract]
-#if !BUILDTASK
-    public
-#endif
-    class AvaloniaResourcesIndex
-    {       
-        [DataMember]
-        public List<AvaloniaResourcesIndexEntry> Entries { get; set; } = new List<AvaloniaResourcesIndexEntry>();
+            var posBeforeEntries = output.Position;
+            WriteIndex(writer, entries);
+
+            var posAfterEntries = output.Position;
+            var indexSize = (int) (posAfterEntries - posBeforeEntries);
+            output.Position = 0L;
+            writer.Write(indexSize);
+            output.Position = posAfterEntries;
+
+            foreach (var resource in resources)
+            {
+                using var resourceStream = resource.Open();
+                resourceStream.CopyTo(output);
+            }
+        }
     }
 
-    [DataContract]
 #if !BUILDTASK
     public
 #endif
     class AvaloniaResourcesIndexEntry
     {
-        [DataMember]
         public string? Path { get; set; }
-        
-        [DataMember]
+
         public int Offset { get; set; }
-        
-        [DataMember]
+
         public int Size { get; set; }
     }
 }
diff --git a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
index 35b22f4f23..e44b7290af 100644
--- a/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
+++ b/src/Avalonia.Build.Tasks/Avalonia.Build.Tasks.csproj
@@ -18,6 +18,9 @@
       <Compile Include="../Avalonia.Base/Utilities/AvaloniaResourcesIndex.cs">
         <Link>Shared/AvaloniaResourcesIndex.cs</Link>
       </Compile>
+      <Compile Include="../Avalonia.Base/Platform/Internal/Constants.cs">
+        <Link>Shared/Constants.cs</Link>
+      </Compile>
       <Compile Include="../Markup/Avalonia.Markup.Xaml/PortableXaml/AvaloniaResourceXamlInfo.cs">
         <Link>Shared/AvaloniaResourceXamlInfo.cs</Link>
       </Compile>
diff --git a/src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs b/src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs
index 65681a2d28..264a86b014 100644
--- a/src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs
+++ b/src/Avalonia.Build.Tasks/GenerateAvaloniaResourcesTask.cs
@@ -77,29 +77,9 @@ namespace Avalonia.Build.Tasks
 
         private void Pack(Stream output, List<Source> sources)
         {
-            var offsets = new Dictionary<Source, int>();
-            var coffset = 0;
-            foreach (var s in sources)
-            {
-                offsets[s] = coffset;
-                coffset += s.Size;
-            }
-            var index = sources.Select(s => new AvaloniaResourcesIndexEntry
-            {
-                Path = s.Path,
-                Size = s.Size,
-                Offset = offsets[s]
-            }).ToList();
-            var ms = new MemoryStream();
-            AvaloniaResourcesIndexReaderWriter.Write(ms, index);
-            new BinaryWriter(output).Write((int)ms.Length);
-            ms.Position = 0;
-            ms.CopyTo(output);
-            foreach (var s in sources)
-            {
-                using (var input = s.Open())
-                    input.CopyTo(output);
-            }
+            AvaloniaResourcesIndexReaderWriter.WriteResources(
+                output,
+                sources.Select(source => (source.Path, source.Size, (Func<Stream>) source.Open)).ToList());
         }
 
         private bool PreProcessXamlFiles(List<Source> sources)
diff --git a/src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.Helpers.cs b/src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.Helpers.cs
index f83e07bd74..079ea91db1 100644
--- a/src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.Helpers.cs
+++ b/src/Avalonia.Build.Tasks/XamlCompilerTaskExecutor.Helpers.cs
@@ -1,6 +1,8 @@
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Linq;
+using Avalonia.Platform.Internal;
 using Avalonia.Utilities;
 using Mono.Cecil;
 using Mono.Cecil.Cil;
@@ -34,13 +36,13 @@ namespace Avalonia.Build.Tasks
             {
                 _asm = asm;
                 _embedded = ((EmbeddedResource)asm.MainModule.Resources.FirstOrDefault(r =>
-                    r.ResourceType == ResourceType.Embedded && r.Name == "!AvaloniaResources"));
+                    r.ResourceType == ResourceType.Embedded && r.Name == Constants.AvaloniaResourceName));
                 if (_embedded == null)
                     return;
                 using (var stream = _embedded.GetResourceStream())
                 {
                     var br = new BinaryReader(stream);
-                    var index = AvaloniaResourcesIndexReaderWriter.Read(new MemoryStream(br.ReadBytes(br.ReadInt32())));
+                    var index = AvaloniaResourcesIndexReaderWriter.ReadIndex(new MemoryStream(br.ReadBytes(br.ReadInt32())));
                     var baseOffset = stream.Position;
                     foreach (var e in index)
                     {
@@ -61,9 +63,18 @@ namespace Avalonia.Build.Tasks
                 if (_resources.Count == 0)
                     return;
 
-                _embedded = new EmbeddedResource("!AvaloniaResources", ManifestResourceAttributes.Public,
-                    AvaloniaResourcesIndexReaderWriter.Create(_resources.ToDictionary(x => x.Key,
-                        x => x.Value.FileContents)));
+                var output = new MemoryStream();
+
+                AvaloniaResourcesIndexReaderWriter.WriteResources(
+                    output,
+                    _resources.Select(x => (
+                        Path: x.Key,
+                        Size: x.Value.FileContents.Length,
+                        Open: (Func<Stream>) (() => new MemoryStream(x.Value.FileContents))
+                    )).ToList());
+
+                output.Position = 0L;
+                _embedded = new EmbeddedResource(Constants.AvaloniaResourceName, ManifestResourceAttributes.Public, output);
                 _asm.MainModule.Resources.Add(_embedded);
             }
 

From ae8e6cc12045aa7c4e9fe449d66eebacdd356537 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 02:18:20 +0300
Subject: [PATCH 127/157] [Text] [Optimization] [Alloc] Bidi Pooling

---
 .../Media/TextFormatting/TextFormatterImpl.cs  |  4 ++--
 .../TextFormatting/Unicode/BiDiAlgorithm.cs    | 10 +++++++++-
 .../Media/TextFormatting/Unicode/BiDiData.cs   | 12 +++++++++++-
 src/Avalonia.Base/Utilities/ArrayBuilder.cs    | 18 ++++++++++++++----
 4 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
index ef2abdfea0..c5ded72a43 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
@@ -159,7 +159,7 @@ namespace Avalonia.Media.TextFormatting
         {
             var flowDirection = paragraphProperties.FlowDirection;
             var drawableTextRuns = new List<DrawableTextRun>();
-            var biDiData = new BidiData((sbyte)flowDirection);
+            using var biDiData = new BidiData((sbyte)flowDirection);
 
             foreach (var textRun in textRuns)
             {
@@ -177,7 +177,7 @@ namespace Avalonia.Media.TextFormatting
                 }
             }
 
-            var biDi = new BidiAlgorithm();
+            using var biDi = new BidiAlgorithm();
 
             biDi.Process(biDiData);
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
index 17ec9b1df2..3372d2be51 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
@@ -27,7 +27,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// as much as possible.
     /// </para>
     /// </remarks>
-    internal sealed class BidiAlgorithm
+    internal sealed class BidiAlgorithm : IDisposable
     {
         /// <summary>
         /// The original BiDiClass classes as provided by the caller
@@ -1714,5 +1714,13 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             public BidiClass Eos { get; }
         }
+
+        public void Dispose()
+        {
+            _workingClassesBuffer.Dispose();
+            _resolvedLevelsBuffer.Dispose();
+            _x9Map.Dispose();
+            _isolatedRunMapping.Dispose();
+        }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
index 0c51b0898d..7e5b3a6620 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
@@ -11,7 +11,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// Represents a unicode string and all associated attributes
     /// for each character required for the bidirectional Unicode algorithm
     /// </summary>
-    internal class BidiData
+    internal class BidiData : IDisposable
     {
         private ArrayBuilder<BidiClass> _classes;
         private ArrayBuilder<BidiPairedBracketType> _pairedBracketTypes;
@@ -181,5 +181,15 @@ namespace Avalonia.Media.TextFormatting.Unicode
             
             return _tempLevelBuffer.Add(length, false);
         }
+
+        public void Dispose()
+        {
+            _classes.Dispose();
+            _pairedBracketTypes.Dispose();
+            _pairedBracketValues.Dispose();
+            _savedClasses.Dispose();
+            _savedPairedBracketTypes.Dispose();
+            _tempLevelBuffer.Dispose();
+        }
     }
 }
diff --git a/src/Avalonia.Base/Utilities/ArrayBuilder.cs b/src/Avalonia.Base/Utilities/ArrayBuilder.cs
index 60bf2c7586..d63eaddb7d 100644
--- a/src/Avalonia.Base/Utilities/ArrayBuilder.cs
+++ b/src/Avalonia.Base/Utilities/ArrayBuilder.cs
@@ -3,6 +3,7 @@
 // Ported from: https://github.com/SixLabors/Fonts/
 
 using System;
+using System.Buffers;
 using System.Runtime.CompilerServices;
 
 namespace Avalonia.Utilities
@@ -11,7 +12,7 @@ namespace Avalonia.Utilities
     /// A helper type for avoiding allocations while building arrays.
     /// </summary>
     /// <typeparam name="T">The type of item contained in the array.</typeparam>
-    internal struct ArrayBuilder<T>
+    internal struct ArrayBuilder<T> : IDisposable
         where T : struct
     {
         private const int DefaultCapacity = 4;
@@ -135,7 +136,7 @@ namespace Avalonia.Utilities
             }
 
             // Same expansion algorithm as List<T>.
-            var newCapacity = length == 0 ? DefaultCapacity : (uint)length * 2u;
+            var newCapacity = length == 0 ? DefaultCapacity : length * 2;
 
             if (newCapacity > MaxCoreClrArrayLength)
             {
@@ -144,10 +145,11 @@ namespace Avalonia.Utilities
 
             if (newCapacity < min)
             {
-                newCapacity = (uint)min;
+                newCapacity = min;
             }
 
-            var array = new T[newCapacity];
+            Dispose();
+            var array = ArrayPool<T>.Shared.Rent(newCapacity);
 
             if (_size > 0)
             {
@@ -180,5 +182,13 @@ namespace Avalonia.Utilities
         /// <returns>The <see cref="ArraySlice{T}"/>.</returns>
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public ArraySlice<T> AsSlice(int start, int length) => new ArraySlice<T>(_data!, start, length);
+        
+        public void Dispose()
+        {
+            if (_data != null)
+            {
+                ArrayPool<T>.Shared.Return(_data);
+            }
+        }
     }
 }

From 39374451ddbc733d818255c8a06b2650796b91d3 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 02:54:04 +0300
Subject: [PATCH 128/157] [Text] Add pooling to shapedBuffer. works only with
 dispose.

---
 src/Avalonia.Base/Media/GlyphRun.cs           |  2 +-
 .../Media/TextFormatting/ShapedBuffer.cs      | 29 ++++++++++++++++---
 .../Media/TextFormatting/ShapedTextRun.cs     |  8 ++++-
 .../Media/TextFormatting/TextLayout.cs        | 10 ++++++-
 .../Media/TextFormatting/TextLine.cs          |  4 ++-
 .../Media/TextFormatting/TextLineImpl.cs      |  9 ++++++
 src/Avalonia.Base/Utilities/ArraySlice.cs     |  9 ++++++
 .../Text/HugeTextLayout.cs                    |  8 +++--
 8 files changed, 69 insertions(+), 10 deletions(-)

diff --git a/src/Avalonia.Base/Media/GlyphRun.cs b/src/Avalonia.Base/Media/GlyphRun.cs
index af9e458a28..811479fde8 100644
--- a/src/Avalonia.Base/Media/GlyphRun.cs
+++ b/src/Avalonia.Base/Media/GlyphRun.cs
@@ -918,7 +918,7 @@ namespace Avalonia.Media
             _glyphRunImpl = platformRenderInterface.CreateGlyphRun(GlyphTypeface, FontRenderingEmSize, GlyphIndices, GlyphAdvances, GlyphOffsets);
         }
 
-        void IDisposable.Dispose()
+        public void Dispose()
         {
             _glyphRunImpl?.Dispose();
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
index 902b897240..5cf153d199 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
@@ -1,17 +1,20 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using Avalonia.Utilities;
 
 namespace Avalonia.Media.TextFormatting
 {
-    public sealed class ShapedBuffer : IList<GlyphInfo>
+    public sealed class ShapedBuffer : IList<GlyphInfo>, IDisposable
     {
         private static readonly IComparer<GlyphInfo> s_clusterComparer = new CompareClusters();
+        private bool _rented;
         
         public ShapedBuffer(CharacterBufferRange characterBufferRange, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) : 
-            this(characterBufferRange, new GlyphInfo[bufferLength], glyphTypeface,  fontRenderingEmSize,  bidiLevel)
+            this(characterBufferRange, ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), glyphTypeface,  fontRenderingEmSize,  bidiLevel)
         {
-
+            _rented = true;
+            Length = bufferLength;
         }
 
         internal ShapedBuffer(CharacterBufferRange characterBufferRange, ArraySlice<GlyphInfo> glyphInfos, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel)
@@ -21,11 +24,12 @@ namespace Avalonia.Media.TextFormatting
             GlyphTypeface = glyphTypeface;
             FontRenderingEmSize = fontRenderingEmSize;
             BidiLevel = bidiLevel;
+            Length = GlyphInfos.Length;
         }
 
         internal ArraySlice<GlyphInfo> GlyphInfos { get; }
         
-        public int Length => GlyphInfos.Length;
+        public int Length { get; }
 
         public IGlyphTypeface GlyphTypeface { get; }
 
@@ -260,6 +264,23 @@ namespace Avalonia.Media.TextFormatting
 
             System.Collections.IEnumerator System.Collections.IEnumerable.GetEnumerator() => GetEnumerator();
         }
+
+        public void Dispose()
+        {
+            GC.SuppressFinalize(this);
+            if (_rented)
+            {
+                GlyphInfos.ReturnRent();
+            }
+        }
+
+        ~ShapedBuffer()
+        {
+            if (_rented)
+            {
+                GlyphInfos.ReturnRent();
+            }
+        }
     }
 
     public readonly record struct GlyphInfo
diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
index 3149bc2cda..665723b284 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
@@ -6,7 +6,7 @@ namespace Avalonia.Media.TextFormatting
     /// <summary>
     /// A text run that holds shaped characters.
     /// </summary>
-    public sealed class ShapedTextRun : DrawableTextRun
+    public sealed class ShapedTextRun : DrawableTextRun, IDisposable
     {
         private GlyphRun? _glyphRun;
 
@@ -199,5 +199,11 @@ namespace Avalonia.Media.TextFormatting
                 ShapedBuffer.GlyphClusters,
                 BidiLevel);
         }
+
+        public void Dispose()
+        {
+            _glyphRun?.Dispose();
+            ShapedBuffer.Dispose();
+        }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs b/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
index f803001481..969b960c6b 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLayout.cs
@@ -8,7 +8,7 @@ namespace Avalonia.Media.TextFormatting
     /// <summary>
     /// Represents a multi line text layout.
     /// </summary>
-    public class TextLayout
+    public class TextLayout : IDisposable
     {
         private readonly ITextSource _textSource;
         private readonly TextParagraphProperties _paragraphProperties;
@@ -561,5 +561,13 @@ namespace Avalonia.Media.TextFormatting
 
             return _textTrimming.CreateCollapsingProperties(new TextCollapsingCreateInfo(width, _paragraphProperties.DefaultTextRunProperties));
         }
+
+        public void Dispose()
+        {
+            foreach (var line in TextLines)
+            {
+                line.Dispose();
+            }
+        }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLine.cs b/src/Avalonia.Base/Media/TextFormatting/TextLine.cs
index 61b24dc8c5..3cb26882dc 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLine.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLine.cs
@@ -6,7 +6,7 @@ namespace Avalonia.Media.TextFormatting
     /// <summary>
     /// Represents a line of text that is used for text rendering.
     /// </summary>
-    public abstract class TextLine
+    public abstract class TextLine : IDisposable
     {
         /// <summary>
         /// Gets the text runs that are contained within a line.
@@ -207,5 +207,7 @@ namespace Avalonia.Media.TextFormatting
         /// <param name="textLength">number of characters of the specified range</param>
         /// <returns>an array of bounding rectangles.</returns>
         public abstract IReadOnlyList<TextBounds> GetTextBounds(int firstTextSourceCharacterIndex, int textLength);
+
+        public abstract void Dispose();
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index 5fb1171221..93ee139763 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Avalonia.Utilities;
 
 namespace Avalonia.Media.TextFormatting
@@ -934,6 +935,14 @@ namespace Avalonia.Media.TextFormatting
             return GetTextBoundsRightToLeft(firstTextSourceIndex, textLength);
         }
 
+        public override void Dispose()
+        {
+            foreach (var run in _textRuns.OfType<ShapedTextRun>())
+            {
+                run.Dispose();
+            }
+        }
+
         public TextLineImpl FinalizeLine()
         {
             _textLineMetrics = CreateLineMetrics();
diff --git a/src/Avalonia.Base/Utilities/ArraySlice.cs b/src/Avalonia.Base/Utilities/ArraySlice.cs
index 39c0cd5556..b70088a907 100644
--- a/src/Avalonia.Base/Utilities/ArraySlice.cs
+++ b/src/Avalonia.Base/Utilities/ArraySlice.cs
@@ -3,6 +3,7 @@
 // Ported from: https://github.com/SixLabors/Fonts/
 
 using System;
+using System.Buffers;
 using System.Collections;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
@@ -185,5 +186,13 @@ namespace Avalonia.Utilities
 
         /// <inheritdoc/>
         int IReadOnlyCollection<T>.Count => Length;
+
+        public void ReturnRent()
+        {
+            if (_data != null)
+            {
+                ArrayPool<T>.Shared.Return(_data);
+            }
+        }
     }
 }
diff --git a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
index e696b976ad..20fa268a85 100644
--- a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
+++ b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
@@ -70,8 +70,12 @@ In respect that the structure of the sufficient amount poses problems and challe
     [Benchmark]
     public TextLayout[] BuildManySmallTexts() => _manySmallStrings.Select(MakeLayout).ToArray();
 
-    private static TextLayout MakeLayout(string str) 
-        => new TextLayout(str, Typeface.Default, 12d, Brushes.Black, maxWidth:120);
+    private static TextLayout MakeLayout(string str)
+    {
+        var layout = new TextLayout(str, Typeface.Default, 12d, Brushes.Black, maxWidth: 120);
+        layout.Dispose();
+        return layout;
+    }
 
     public void Dispose()
     {

From f8c2288f4a738900be1b75c6c507c403f153e056 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 03:04:34 +0300
Subject: [PATCH 129/157] [Text] [Bidi] fix EnsureCapacity return

---
 src/Avalonia.Base/Utilities/ArrayBuilder.cs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Base/Utilities/ArrayBuilder.cs b/src/Avalonia.Base/Utilities/ArrayBuilder.cs
index d63eaddb7d..e6b67bd383 100644
--- a/src/Avalonia.Base/Utilities/ArrayBuilder.cs
+++ b/src/Avalonia.Base/Utilities/ArrayBuilder.cs
@@ -147,13 +147,13 @@ namespace Avalonia.Utilities
             {
                 newCapacity = min;
             }
-
-            Dispose();
+            
             var array = ArrayPool<T>.Shared.Rent(newCapacity);
 
             if (_size > 0)
             {
                 Array.Copy(_data!, array, _size);
+                ArrayPool<T>.Shared.Return(_data!);
             }
 
             _data = array;

From dc25b802a758abd8cd6c8329224c6cb9ada45be5 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 03:30:06 +0300
Subject: [PATCH 130/157] [Text] add pooled list and pooled stack usage

---
 .../TextFormatting/Unicode/BiDiAlgorithm.cs   | 22 ++++++++++++-------
 .../Media/TextFormatting/Unicode/BiDiData.cs  |  2 +-
 2 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
index 3372d2be51..0bea4def28 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
@@ -6,6 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
 using System.Threading;
+using Avalonia.Collections.Pooled;
 using Avalonia.Utilities;
 
 namespace Avalonia.Media.TextFormatting.Unicode
@@ -27,7 +28,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// as much as possible.
     /// </para>
     /// </remarks>
-    internal sealed class BidiAlgorithm : IDisposable
+    internal struct BidiAlgorithm : IDisposable
     {
         /// <summary>
         /// The original BiDiClass classes as provided by the caller
@@ -97,7 +98,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// The status stack used during resolution of explicit
         /// embedding and isolating runs
         /// </summary>
-        private readonly Stack<Status> _statusStack = new Stack<Status>();
+        private readonly PooledStack<Status> _statusStack = new PooledStack<Status>();
 
         /// <summary>
         /// Mapping used to virtually remove characters for rule X9
@@ -107,7 +108,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// Re-usable list of level runs
         /// </summary>
-        private readonly List<LevelRun> _levelRuns = new List<LevelRun>();
+        private readonly PooledList<LevelRun> _levelRuns = new PooledList<LevelRun>();
 
         /// <summary>
         /// Mapping for the current isolating sequence, built
@@ -118,7 +119,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// A stack of pending isolate openings used by FindIsolatePairs()
         /// </summary>
-        private readonly Stack<int> _pendingIsolateOpenings = new Stack<int>();
+        private readonly PooledStack<int> _pendingIsolateOpenings = new PooledStack<int>();
 
         /// <summary>
         /// The level of the isolating run currently being processed
@@ -174,17 +175,17 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Reusable list of pending opening brackets used by the
         /// LocatePairedBrackets method
         /// </summary>
-        private readonly List<int> _pendingOpeningBrackets = new List<int>();
+        private readonly PooledList<int> _pendingOpeningBrackets = new PooledList<int>();
 
         /// <summary>
         /// Resolved list of paired brackets
         /// </summary>
-        private readonly List<BracketPair> _pairedBrackets = new List<BracketPair>();
+        private readonly PooledList<BracketPair> _pairedBrackets = new PooledList<BracketPair>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BidiAlgorithm"/> class.
         /// </summary>
-        internal BidiAlgorithm()
+        public BidiAlgorithm()
         {
         }
 
@@ -1272,7 +1273,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Locate all pair brackets in the current isolating run
         /// </summary>
         /// <returns>A sorted list of BracketPairs</returns>
-        private List<BracketPair> LocatePairedBrackets()
+        private PooledList<BracketPair> LocatePairedBrackets()
         {
             // Clear work collections
             _pendingOpeningBrackets.Clear();
@@ -1719,8 +1720,13 @@ namespace Avalonia.Media.TextFormatting.Unicode
         {
             _workingClassesBuffer.Dispose();
             _resolvedLevelsBuffer.Dispose();
+            _statusStack.Dispose();
             _x9Map.Dispose();
+            _levelRuns.Dispose();
             _isolatedRunMapping.Dispose();
+            _pendingIsolateOpenings.Dispose();
+            _pendingOpeningBrackets.Dispose();
+            _pairedBrackets.Dispose();
         }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
index 7e5b3a6620..644f7e9a8a 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
@@ -11,7 +11,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// Represents a unicode string and all associated attributes
     /// for each character required for the bidirectional Unicode algorithm
     /// </summary>
-    internal class BidiData : IDisposable
+    internal struct BidiData : IDisposable
     {
         private ArrayBuilder<BidiClass> _classes;
         private ArrayBuilder<BidiPairedBracketType> _pairedBracketTypes;

From 22a41933bedfddb81c1d4db82a078263e7632a0c Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 03:43:55 +0300
Subject: [PATCH 131/157] [Text] bidi - do not use pooled collections

---
 .../TextFormatting/Unicode/BiDiAlgorithm.cs     | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
index 0bea4def28..093c7f3f56 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
@@ -98,7 +98,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// The status stack used during resolution of explicit
         /// embedding and isolating runs
         /// </summary>
-        private readonly PooledStack<Status> _statusStack = new PooledStack<Status>();
+        private readonly Stack<Status> _statusStack = new Stack<Status>();
 
         /// <summary>
         /// Mapping used to virtually remove characters for rule X9
@@ -108,7 +108,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// Re-usable list of level runs
         /// </summary>
-        private readonly PooledList<LevelRun> _levelRuns = new PooledList<LevelRun>();
+        private readonly List<LevelRun> _levelRuns = new List<LevelRun>();
 
         /// <summary>
         /// Mapping for the current isolating sequence, built
@@ -119,7 +119,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// A stack of pending isolate openings used by FindIsolatePairs()
         /// </summary>
-        private readonly PooledStack<int> _pendingIsolateOpenings = new PooledStack<int>();
+        private readonly Stack<int> _pendingIsolateOpenings = new Stack<int>();
 
         /// <summary>
         /// The level of the isolating run currently being processed
@@ -175,12 +175,12 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Reusable list of pending opening brackets used by the
         /// LocatePairedBrackets method
         /// </summary>
-        private readonly PooledList<int> _pendingOpeningBrackets = new PooledList<int>();
+        private readonly List<int> _pendingOpeningBrackets = new List<int>();
 
         /// <summary>
         /// Resolved list of paired brackets
         /// </summary>
-        private readonly PooledList<BracketPair> _pairedBrackets = new PooledList<BracketPair>();
+        private readonly List<BracketPair> _pairedBrackets = new List<BracketPair>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="BidiAlgorithm"/> class.
@@ -1273,7 +1273,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Locate all pair brackets in the current isolating run
         /// </summary>
         /// <returns>A sorted list of BracketPairs</returns>
-        private PooledList<BracketPair> LocatePairedBrackets()
+        private List<BracketPair> LocatePairedBrackets()
         {
             // Clear work collections
             _pendingOpeningBrackets.Clear();
@@ -1720,13 +1720,8 @@ namespace Avalonia.Media.TextFormatting.Unicode
         {
             _workingClassesBuffer.Dispose();
             _resolvedLevelsBuffer.Dispose();
-            _statusStack.Dispose();
             _x9Map.Dispose();
-            _levelRuns.Dispose();
             _isolatedRunMapping.Dispose();
-            _pendingIsolateOpenings.Dispose();
-            _pendingOpeningBrackets.Dispose();
-            _pairedBrackets.Dispose();
         }
     }
 }

From 8ece18c53dcedf2475f9cbf97a25c4ea66f564e5 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 04:09:19 +0300
Subject: [PATCH 132/157] [Text] optimize CoalesceLevels alloc

---
 .../Media/TextFormatting/TextFormatterImpl.cs | 21 +++++++++----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
index a69c56eee1..517372648f 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
@@ -187,10 +187,7 @@ namespace Avalonia.Media.TextFormatting
 
             var processedRuns = new List<TextRun>(textRuns.Count);
 
-            foreach (var coalescedRuns in CoalesceLevels(textRuns, biDi.ResolvedLevels))
-            {
-                processedRuns.AddRange(coalescedRuns);
-            }
+            CoalesceLevels(textRuns, biDi.ResolvedLevels, processedRuns);
 
             for (var index = 0; index < processedRuns.Count; index++)
             {
@@ -282,12 +279,14 @@ namespace Avalonia.Media.TextFormatting
         /// </summary>
         /// <param name="textCharacters">The text characters to form <see cref="UnshapedTextRun"/> from.</param>
         /// <param name="levels">The bidi levels.</param>
+        /// <param name="processedRuns"></param>
         /// <returns></returns>
-        private static IEnumerable<IReadOnlyList<TextRun>> CoalesceLevels(IReadOnlyList<TextRun> textCharacters, ArraySlice<sbyte> levels)
+        private static void CoalesceLevels(IReadOnlyList<TextRun> textCharacters, ArraySlice<sbyte> levels,
+            List<TextRun> processedRuns)
         {
             if (levels.Length == 0)
             {
-                yield break;
+                return;
             }
 
             var levelIndex = 0;
@@ -306,7 +305,7 @@ namespace Avalonia.Media.TextFormatting
                 {
                     var drawableRun = textCharacters[i];
 
-                    yield return new[] { drawableRun };
+                    processedRuns.Add(drawableRun);
 
                     levelIndex += drawableRun.Length;
 
@@ -329,7 +328,7 @@ namespace Avalonia.Media.TextFormatting
 
                     if (j == runText.Length)
                     {
-                        yield return currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties);
+                        processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties));
 
                         runLevel = levels[levelIndex];
 
@@ -342,7 +341,7 @@ namespace Avalonia.Media.TextFormatting
                     }
 
                     // End of this run
-                    yield return currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties);
+                    processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties));
 
                     runText = runText.Skip(j);
 
@@ -355,10 +354,10 @@ namespace Avalonia.Media.TextFormatting
 
             if (currentRun is null || runText.IsEmpty)
             {
-                yield break;
+                return;
             }
 
-            yield return currentRun.GetShapeableCharacters(runText, runLevel, ref previousProperties);
+            processedRuns.AddRange(currentRun.GetShapeableCharacters(runText, runLevel, ref previousProperties));
         }
 
         /// <summary>

From 31beefe487a3f3d09027d835c7897d0d082947f6 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 04:12:02 +0300
Subject: [PATCH 133/157] [Bidi] Optimize alloc of double dictionary

---
 .../Media/TextFormatting/Unicode/BiDiAlgorithm.cs     | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
index 093c7f3f56..8014762ce8 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
@@ -67,7 +67,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// The forward mapping maps the start index to the end index.
         /// The reverse mapping maps the end index to the start index.
         /// </remarks>
-        private readonly BidiDictionary<int, int> _isolatePairs = new BidiDictionary<int, int>();
+        private BidiDictionary<int, int>? _isolatePairs;
 
         /// <summary>
         /// The working BiDi classes
@@ -228,7 +228,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
             ArraySlice<sbyte>? outLevels)
         {
             // Reset state
-            _isolatePairs.Clear();
+            _isolatePairs?.Clear();
             _workingClassesBuffer.Clear();
             _levelRuns.Clear();
             _resolvedLevelsBuffer.Clear();
@@ -324,7 +324,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                         // Skip isolate pairs
                         // (Because we're working with a slice, we need to adjust the indices
                         //  we're using for the isolatePairs map)
-                        if (_isolatePairs.TryGetValue(data.Start + i, out i))
+                        if (_isolatePairs?.TryGetValue(data.Start + i, out i) == true)
                         {
                             i -= data.Start;
                         }
@@ -379,6 +379,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                     {
                         if (_pendingIsolateOpenings.Count > 0)
                         {
+                            _isolatePairs ??= new BidiDictionary<int, int>();
                             _isolatePairs.Add(_pendingIsolateOpenings.Pop(), i);
                         }
 
@@ -499,7 +500,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
                         if (resolvedIsolate == BidiClass.FirstStrongIsolate)
                         {
-                            if (!_isolatePairs.TryGetValue(i, out var endOfIsolate))
+                            if (_isolatePairs == null || !_isolatePairs.TryGetValue(i, out var endOfIsolate))
                             {
                                 endOfIsolate = _originalClasses.Length;
                             }
@@ -830,7 +831,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                     var lastCharacterIndex = _isolatedRunMapping[_isolatedRunMapping.Length - 1];
                     var lastType = _originalClasses[lastCharacterIndex];
                     if ((lastType == BidiClass.LeftToRightIsolate || lastType == BidiClass.RightToLeftIsolate || lastType == BidiClass.FirstStrongIsolate) &&
-                            _isolatePairs.TryGetValue(lastCharacterIndex, out var nextRunIndex))
+                            _isolatePairs?.TryGetValue(lastCharacterIndex, out var nextRunIndex) == true)
                     {
                         // Find the continuing run index
                         runIndex = FindRunForIndex(nextRunIndex);

From 97f2a26941c492cd7bcc5447dd78aac60ce12b80 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 04:18:01 +0300
Subject: [PATCH 134/157] [Text] [Bidi] do not create collections if not need
 them

---
 .../Media/TextFormatting/Unicode/BiDiAlgorithm.cs          | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
index 8014762ce8..100d381afe 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiAlgorithm.cs
@@ -119,7 +119,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <summary>
         /// A stack of pending isolate openings used by FindIsolatePairs()
         /// </summary>
-        private readonly Stack<int> _pendingIsolateOpenings = new Stack<int>();
+        private Stack<int>? _pendingIsolateOpenings;
 
         /// <summary>
         /// The level of the isolating run currently being processed
@@ -359,7 +359,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
             _hasIsolates = false;
 
             // BD9...
-            _pendingIsolateOpenings.Clear();
+            _pendingIsolateOpenings?.Clear();
             
             for (var i = 0; i < _originalClasses.Length; i++)
             {
@@ -371,13 +371,14 @@ namespace Avalonia.Media.TextFormatting.Unicode
                     case BidiClass.RightToLeftIsolate:
                     case BidiClass.FirstStrongIsolate:
                     {
+                        _pendingIsolateOpenings ??= new Stack<int>();
                         _pendingIsolateOpenings.Push(i);
                         _hasIsolates = true;
                         break;
                     }
                     case BidiClass.PopDirectionalIsolate:
                     {
-                        if (_pendingIsolateOpenings.Count > 0)
+                        if (_pendingIsolateOpenings?.Count > 0)
                         {
                             _isolatePairs ??= new BidiDictionary<int, int>();
                             _isolatePairs.Add(_pendingIsolateOpenings.Pop(), i);

From fc4e549c2eb480aa1339befc88a6473bd71a320c Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Wed, 11 Jan 2023 13:31:01 +0100
Subject: [PATCH 135/157] Cleanup

---
 src/Avalonia.Base/Media/TextDecoration.cs     | 57 ++++++++++++++++++-
 src/Avalonia.Base/Platform/IGlyphRunImpl.cs   |  6 +-
 .../HeadlessPlatformRenderInterface.cs        |  5 ++
 src/Skia/Avalonia.Skia/GlyphRunImpl.cs        |  4 ++
 .../Avalonia.Direct2D1/Media/GlyphRunImpl.cs  |  8 ++-
 tests/Avalonia.UnitTests/MockGlyphRun.cs      |  8 ++-
 6 files changed, 82 insertions(+), 6 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextDecoration.cs b/src/Avalonia.Base/Media/TextDecoration.cs
index 0a7328125a..0ed73e7786 100644
--- a/src/Avalonia.Base/Media/TextDecoration.cs
+++ b/src/Avalonia.Base/Media/TextDecoration.cs
@@ -1,5 +1,9 @@
-using Avalonia.Collections;
+using System.Collections.Generic;
+using Avalonia.Collections;
+using Avalonia.Collections.Pooled;
 using Avalonia.Media.TextFormatting;
+using Avalonia.Platform;
+using Avalonia.Utilities;
 
 namespace Avalonia.Media
 {
@@ -196,19 +200,66 @@ namespace Avalonia.Media
                     break;
             }
 
+            var strokeOffset = 0.0;
+
             switch (StrokeOffsetUnit)
             {
                 case TextDecorationUnit.FontRenderingEmSize:
-                    origin += new Point(0, StrokeOffset * textMetrics.FontRenderingEmSize);
+                    strokeOffset = StrokeOffset * textMetrics.FontRenderingEmSize;
                     break;
                 case TextDecorationUnit.Pixel:
-                    origin += new Point(0, StrokeOffset);
+                    strokeOffset = StrokeOffset;
                     break;
             }
 
+            origin += new Point(0, strokeOffset);
+
             var pen = new Pen(Stroke ?? defaultBrush, thickness,
                 new DashStyle(StrokeDashArray, StrokeDashOffset), StrokeLineCap);
 
+            if (Location == TextDecorationLocation.Underline && MathUtilities.IsZero(strokeOffset))
+            {
+                var intersections = glyphRun.GlyphRunImpl.GetIntersections((float)(thickness * 0.5d + strokeOffset), (float)(thickness * 1.5d + strokeOffset));
+
+                if (intersections != null && intersections.Count > 0)
+                {
+                    var last = baselineOrigin.X;
+                    var finalPos = last + glyphRun.Size.Width;
+                    var end = last;
+
+                    var points = new List<double>();
+
+                    //math is taken from chrome's source code.
+                    for (var i = 0; i < intersections.Count; i += 2)
+                    {
+                        var start = intersections[i] - thickness;
+                        end = intersections[i + 1] + thickness;
+                        if (start > last && last + textMetrics.FontRenderingEmSize / 12 < start)
+                        {
+                            points.Add(last);
+                            points.Add(start);
+                        }
+                        last = end;
+                    }
+
+                    if (end < finalPos)
+                    {
+                        points.Add(end);
+                        points.Add(finalPos);
+                    }
+
+                    for (var i = 0; i < points.Count; i += 2)
+                    {
+                        var a = new Point(points[i], origin.Y);
+                        var b = new Point(points[i + 1], origin.Y);
+
+                        drawingContext.DrawLine(pen, a, b);
+                    }
+
+                    return;
+                }              
+            }
+
             drawingContext.DrawLine(pen, origin, origin + new Point(glyphRun.Metrics.Width, 0));
         }
     }
diff --git a/src/Avalonia.Base/Platform/IGlyphRunImpl.cs b/src/Avalonia.Base/Platform/IGlyphRunImpl.cs
index 7801bdd50f..6a8ae4d954 100644
--- a/src/Avalonia.Base/Platform/IGlyphRunImpl.cs
+++ b/src/Avalonia.Base/Platform/IGlyphRunImpl.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Avalonia.Metadata;
 
 namespace Avalonia.Platform
@@ -7,5 +8,8 @@ namespace Avalonia.Platform
     ///     Actual implementation of a glyph run that stores platform dependent resources.
     /// </summary>
     [Unstable]
-    public interface IGlyphRunImpl : IDisposable { }
+    public interface IGlyphRunImpl : IDisposable 
+    {
+        IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound);
+    }
 }
diff --git a/src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs b/src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs
index 9bb4b34976..cb79cc85db 100644
--- a/src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs
+++ b/src/Avalonia.Headless/HeadlessPlatformRenderInterface.cs
@@ -128,6 +128,11 @@ namespace Avalonia.Headless
             public void Dispose()
             {
             }
+
+            public IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound)
+            {
+                throw new NotImplementedException();
+            }
         }
 
         class HeadlessGeometryStub : IGeometryImpl
diff --git a/src/Skia/Avalonia.Skia/GlyphRunImpl.cs b/src/Skia/Avalonia.Skia/GlyphRunImpl.cs
index 484fd9f219..dd7ed31a6e 100644
--- a/src/Skia/Avalonia.Skia/GlyphRunImpl.cs
+++ b/src/Skia/Avalonia.Skia/GlyphRunImpl.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using Avalonia.Metadata;
 using Avalonia.Platform;
 using SkiaSharp;
@@ -20,6 +21,9 @@ namespace Avalonia.Skia
         /// </summary>
         public SKTextBlob TextBlob { get; }
 
+        public IReadOnlyList<float> GetIntersections(float upperBound, float lowerBound) => 
+            TextBlob.GetIntercepts(lowerBound, upperBound);
+
         void IDisposable.Dispose()
         {
             TextBlob.Dispose();
diff --git a/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs b/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
index 0b06d5ef3e..638aaf08d6 100644
--- a/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
+++ b/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
@@ -1,4 +1,5 @@
-using Avalonia.Platform;
+using System.Collections.Generic;
+using Avalonia.Platform;
 
 namespace Avalonia.Direct2D1.Media
 {
@@ -15,5 +16,10 @@ namespace Avalonia.Direct2D1.Media
         {
             GlyphRun?.Dispose();
         }
+
+        public IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound)
+        {
+            return null;
+        }
     }
 }
diff --git a/tests/Avalonia.UnitTests/MockGlyphRun.cs b/tests/Avalonia.UnitTests/MockGlyphRun.cs
index 24948aff01..f525e4736b 100644
--- a/tests/Avalonia.UnitTests/MockGlyphRun.cs
+++ b/tests/Avalonia.UnitTests/MockGlyphRun.cs
@@ -1,4 +1,5 @@
-using Avalonia.Platform;
+using System.Collections.Generic;
+using Avalonia.Platform;
 
 namespace Avalonia.UnitTests
 {
@@ -8,5 +9,10 @@ namespace Avalonia.UnitTests
         {
             
         }
+
+        public IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound)
+        {
+            return null;
+        }
     }
 }

From f6535c6b26845f7e327ab494e5ff50b53fb108d8 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 16:01:37 +0300
Subject: [PATCH 136/157] [Text] Dispose Text Layout in TextBlock and
 TextPresenter

---
 src/Avalonia.Controls/Presenters/TextPresenter.cs |  3 +++
 src/Avalonia.Controls/TextBlock.cs                | 11 ++++-------
 2 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/src/Avalonia.Controls/Presenters/TextPresenter.cs b/src/Avalonia.Controls/Presenters/TextPresenter.cs
index 480a8ee7a7..f599511392 100644
--- a/src/Avalonia.Controls/Presenters/TextPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/TextPresenter.cs
@@ -588,6 +588,7 @@ namespace Avalonia.Controls.Presenters
 
         protected virtual void InvalidateTextLayout()
         {
+            _textLayout?.Dispose();
             _textLayout = null;
 
             InvalidateMeasure();
@@ -597,6 +598,7 @@ namespace Avalonia.Controls.Presenters
         {
             _constraint = availableSize;
 
+            _textLayout?.Dispose();
             _textLayout = null;
 
             InvalidateArrange();
@@ -622,6 +624,7 @@ namespace Avalonia.Controls.Presenters
 
             _constraint = new Size(Math.Ceiling(finalSize.Width), double.PositiveInfinity);
 
+            _textLayout?.Dispose();
             _textLayout = null;
 
             return finalSize;
diff --git a/src/Avalonia.Controls/TextBlock.cs b/src/Avalonia.Controls/TextBlock.cs
index 7a0da1ecc5..31ddf1f985 100644
--- a/src/Avalonia.Controls/TextBlock.cs
+++ b/src/Avalonia.Controls/TextBlock.cs
@@ -173,13 +173,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Gets the <see cref="TextLayout"/> used to render the text.
         /// </summary>
-        public TextLayout TextLayout
-        {
-            get
-            {
-                return _textLayout ??= CreateTextLayout(_text);
-            }
-        }
+        public TextLayout TextLayout => _textLayout ??= CreateTextLayout(_text);
 
         /// <summary>
         /// Gets or sets the padding to place around the <see cref="Text"/>.
@@ -648,6 +642,7 @@ namespace Avalonia.Controls
         /// </summary>
         protected void InvalidateTextLayout()
         {
+            _textLayout?.Dispose();
             _textLayout = null;
 
             InvalidateVisual();
@@ -663,6 +658,7 @@ namespace Avalonia.Controls
 
             _constraint = availableSize.Deflate(padding);
 
+            _textLayout?.Dispose();
             _textLayout = null;
 
             var inlines = Inlines;
@@ -726,6 +722,7 @@ namespace Avalonia.Controls
 
             _constraint = new Size(Math.Ceiling(finalSize.Deflate(padding).Width), double.PositiveInfinity);
 
+            _textLayout?.Dispose();
             _textLayout = null;
 
             if (HasComplexContent)

From 56e94e424c9b120f8fac3aa450bbe43ceae22d81 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 16:35:23 +0300
Subject: [PATCH 137/157] [Text] Add textblocks virtualization benchmark,
 rename field

---
 .../Media/TextFormatting/ShapedBuffer.cs      |  8 +++----
 .../Text/HugeTextLayout.cs                    | 21 +++++++++++++++++++
 2 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
index 5cf153d199..40500670ad 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
@@ -8,12 +8,12 @@ namespace Avalonia.Media.TextFormatting
     public sealed class ShapedBuffer : IList<GlyphInfo>, IDisposable
     {
         private static readonly IComparer<GlyphInfo> s_clusterComparer = new CompareClusters();
-        private bool _rented;
+        private bool _bufferRented;
         
         public ShapedBuffer(CharacterBufferRange characterBufferRange, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) : 
             this(characterBufferRange, ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), glyphTypeface,  fontRenderingEmSize,  bidiLevel)
         {
-            _rented = true;
+            _bufferRented = true;
             Length = bufferLength;
         }
 
@@ -268,7 +268,7 @@ namespace Avalonia.Media.TextFormatting
         public void Dispose()
         {
             GC.SuppressFinalize(this);
-            if (_rented)
+            if (_bufferRented)
             {
                 GlyphInfos.ReturnRent();
             }
@@ -276,7 +276,7 @@ namespace Avalonia.Media.TextFormatting
 
         ~ShapedBuffer()
         {
-            if (_rented)
+            if (_bufferRented)
             {
                 GlyphInfos.ReturnRent();
             }
diff --git a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
index 20fa268a85..bf0253e9ab 100644
--- a/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
+++ b/tests/Avalonia.Benchmarks/Text/HugeTextLayout.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Linq;
+using Avalonia.Controls;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.UnitTests;
@@ -70,6 +71,26 @@ In respect that the structure of the sufficient amount poses problems and challe
     [Benchmark]
     public TextLayout[] BuildManySmallTexts() => _manySmallStrings.Select(MakeLayout).ToArray();
 
+    [Benchmark]
+    public void VirtualizeTextBlocks()
+    {
+        var blocks = new TextBlock[10];
+        for (var i = 0; i < blocks.Length; i++)
+        {
+            blocks[i] = new TextBlock
+            {
+                Width = 120,
+                Height = 32,
+            };
+        }
+
+        for (int i = 0, j = 0; i < _manySmallStrings.Length; i++, j = j < blocks.Length - 1 ? j + 1 : 0)
+        {
+            blocks[j].Text = _manySmallStrings[i];
+            blocks[j].Measure(new Size(200, 200));
+        }
+    }
+
     private static TextLayout MakeLayout(string str)
     {
         var layout = new TextLayout(str, Typeface.Default, 12d, Brushes.Black, maxWidth: 120);

From 91fd89017e3f0b43886422715b091c42cacf034b Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 17:34:48 +0300
Subject: [PATCH 138/157] [Text] do not use linq on dispose

---
 src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index af954eb5e9..6034e9f679 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -981,9 +981,12 @@ namespace Avalonia.Media.TextFormatting
 
         public override void Dispose()
         {
-            foreach (var run in _textRuns.OfType<ShapedTextRun>())
+            for (int i = 0; i < _textRuns.Count; i++)
             {
-                run.Dispose();
+                if (_textRuns[i] is ShapedTextRun shapedTextRun)
+                {
+                    shapedTextRun.Dispose();
+                }
             }
         }
 

From 74bbfd8509c34c82d7f73f9bd1e85f9e1801414a Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Wed, 11 Jan 2023 15:35:07 +0100
Subject: [PATCH 139/157] Support intercepts for all location but
 TextDecorationLocation.Strikethrough

---
 src/Avalonia.Base/Media/TextDecoration.cs | 19 +++++++++----------
 tests/Avalonia.Benchmarks/NullGlyphRun.cs |  8 +++++++-
 2 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextDecoration.cs b/src/Avalonia.Base/Media/TextDecoration.cs
index 0ed73e7786..d6b2841214 100644
--- a/src/Avalonia.Base/Media/TextDecoration.cs
+++ b/src/Avalonia.Base/Media/TextDecoration.cs
@@ -1,4 +1,5 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using Avalonia.Collections;
 using Avalonia.Collections.Pooled;
 using Avalonia.Media.TextFormatting;
@@ -200,26 +201,24 @@ namespace Avalonia.Media
                     break;
             }
 
-            var strokeOffset = 0.0;
-
             switch (StrokeOffsetUnit)
             {
                 case TextDecorationUnit.FontRenderingEmSize:
-                    strokeOffset = StrokeOffset * textMetrics.FontRenderingEmSize;
+                    origin += new Point(0, StrokeOffset * textMetrics.FontRenderingEmSize);
                     break;
                 case TextDecorationUnit.Pixel:
-                    strokeOffset = StrokeOffset;
+                    origin += new Point(0, StrokeOffset);
                     break;
             }
 
-            origin += new Point(0, strokeOffset);
-
             var pen = new Pen(Stroke ?? defaultBrush, thickness,
                 new DashStyle(StrokeDashArray, StrokeDashOffset), StrokeLineCap);
 
-            if (Location == TextDecorationLocation.Underline && MathUtilities.IsZero(strokeOffset))
+            if (Location != TextDecorationLocation.Strikethrough)
             {
-                var intersections = glyphRun.GlyphRunImpl.GetIntersections((float)(thickness * 0.5d + strokeOffset), (float)(thickness * 1.5d + strokeOffset));
+                var offsetY = glyphRun.BaselineOrigin.Y - origin.Y;
+
+                var intersections = glyphRun.GlyphRunImpl.GetIntersections((float)(thickness * 0.5d - offsetY), (float)(thickness * 1.5d - offsetY));
 
                 if (intersections != null && intersections.Count > 0)
                 {
@@ -257,7 +256,7 @@ namespace Avalonia.Media
                     }
 
                     return;
-                }              
+                }
             }
 
             drawingContext.DrawLine(pen, origin, origin + new Point(glyphRun.Metrics.Width, 0));
diff --git a/tests/Avalonia.Benchmarks/NullGlyphRun.cs b/tests/Avalonia.Benchmarks/NullGlyphRun.cs
index 5ba0822649..1c2c7c0d7d 100644
--- a/tests/Avalonia.Benchmarks/NullGlyphRun.cs
+++ b/tests/Avalonia.Benchmarks/NullGlyphRun.cs
@@ -1,4 +1,5 @@
-using Avalonia.Platform;
+using System.Collections.Generic;
+using Avalonia.Platform;
 
 namespace Avalonia.Benchmarks
 {
@@ -7,5 +8,10 @@ namespace Avalonia.Benchmarks
         public void Dispose()
         {
         }
+
+        public IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound)
+        {
+            return null;
+        }
     }
 }

From 13280eecf51d2055936d48684643b232d5f8277c Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Wed, 11 Jan 2023 16:29:01 +0100
Subject: [PATCH 140/157] Fix TextLineMetrics calculation for TextLines that
 contain a TextEndOfLine run

---
 .../Media/TextFormatting/TextLineImpl.cs            | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index a1f93bcd07..e7efa33435 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -1436,6 +1436,13 @@ namespace Avalonia.Media.TextFormatting
 
             var lineHeight = _paragraphProperties.LineHeight;
 
+            var lastRunIndex = _textRuns.Count - 1;
+
+            if (_textRuns[lastRunIndex] is TextEndOfLine && lastRunIndex > 0)
+            {
+                lastRunIndex--;
+            }
+
             for (var index = 0; index < _textRuns.Count; index++)
             {
                 switch (_textRuns[index])
@@ -1470,7 +1477,7 @@ namespace Avalonia.Media.TextFormatting
                                 }
                             }
 
-                            if (index == _textRuns.Count - 1)
+                            if (index == lastRunIndex)
                             {
                                 width = widthIncludingWhitespace + textRun.GlyphRun.Metrics.Width;
                                 trailingWhitespaceLength = textRun.GlyphRun.Metrics.TrailingWhitespaceLength;
@@ -1490,7 +1497,7 @@ namespace Avalonia.Media.TextFormatting
                             {
                                 case FlowDirection.LeftToRight:
                                     {
-                                        if (index == _textRuns.Count - 1)
+                                        if (index == lastRunIndex)
                                         {
                                             width = widthIncludingWhitespace;
                                             trailingWhitespaceLength = 0;
@@ -1502,7 +1509,7 @@ namespace Avalonia.Media.TextFormatting
 
                                 case FlowDirection.RightToLeft:
                                     {
-                                        if (index == _textRuns.Count - 1)
+                                        if (index == lastRunIndex)
                                         {
                                             width = widthIncludingWhitespace;
                                             trailingWhitespaceLength = 0;

From 55f33e5c444caef23e9805f4af5b51d37f099883 Mon Sep 17 00:00:00 2001
From: Sergey Mikolaitis <blasterloremaster@gmail.com>
Date: Wed, 11 Jan 2023 20:21:00 +0300
Subject: [PATCH 141/157] [Text] fix tests for ShapedBuffer pooling

---
 src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
index 5cf153d199..0e3267ee38 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
@@ -11,7 +11,11 @@ namespace Avalonia.Media.TextFormatting
         private bool _rented;
         
         public ShapedBuffer(CharacterBufferRange characterBufferRange, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) : 
-            this(characterBufferRange, ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), glyphTypeface,  fontRenderingEmSize,  bidiLevel)
+            this(characterBufferRange, 
+                new ArraySlice<GlyphInfo>(ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), 0, bufferLength), 
+                glyphTypeface,  
+                fontRenderingEmSize,  
+                bidiLevel)
         {
             _rented = true;
             Length = bufferLength;

From 1e646fd9a0431fa1c5b72f384232cff118f6c2e4 Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Wed, 11 Jan 2023 18:47:30 +0100
Subject: [PATCH 142/157] Prevent a crash for empty lines

---
 src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
index e7efa33435..72a8ec8941 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextLineImpl.cs
@@ -1438,7 +1438,7 @@ namespace Avalonia.Media.TextFormatting
 
             var lastRunIndex = _textRuns.Count - 1;
 
-            if (_textRuns[lastRunIndex] is TextEndOfLine && lastRunIndex > 0)
+            if (lastRunIndex > 0 && _textRuns[lastRunIndex] is TextEndOfLine)
             {
                 lastRunIndex--;
             }

From 95ccb0c9c69dda3873a2a1ec1e0ce8f922f1d8c2 Mon Sep 17 00:00:00 2001
From: Martijn Sneijders <martijn@florisoft.nl>
Date: Thu, 12 Jan 2023 20:24:28 +0100
Subject: [PATCH 143/157] ScrollGestureRecognizer ends its current fling
 gesture (touch or pen) if ScrollGestureEventArgs is no longer handled by the
 Presenter.

---
 .../Input/GestureRecognizers/ScrollGestureRecognizer.cs  | 9 ++++++++-
 src/Avalonia.Base/Input/ScrollGestureEventArgs.cs        | 4 ++++
 .../Presenters/ScrollContentPresenter.cs                 | 2 ++
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs b/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
index cec98ec66b..790439245a 100644
--- a/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
+++ b/src/Avalonia.Base/Input/GestureRecognizers/ScrollGestureRecognizer.cs
@@ -189,7 +189,14 @@ namespace Avalonia.Input.GestureRecognizers
 
                         var speed = _inertia * Math.Pow(0.15, st.Elapsed.TotalSeconds);
                         var distance = speed * elapsedSinceLastTick.TotalSeconds;
-                        _target!.RaiseEvent(new ScrollGestureEventArgs(_gestureId, distance));
+                        var scrollGestureEventArgs = new ScrollGestureEventArgs(_gestureId, distance);
+                        _target!.RaiseEvent(scrollGestureEventArgs);
+
+                        if (!scrollGestureEventArgs.Handled || scrollGestureEventArgs.ShouldEndScrollGesture)
+                        {
+                            EndGesture();
+                            return false;
+                        }
 
                         // EndGesture using InertialScrollSpeedEnd only in the direction of scrolling
                         if (CanVerticallyScroll && CanHorizontallyScroll && Math.Abs(speed.X) < InertialScrollSpeedEnd && Math.Abs(speed.Y) <= InertialScrollSpeedEnd)
diff --git a/src/Avalonia.Base/Input/ScrollGestureEventArgs.cs b/src/Avalonia.Base/Input/ScrollGestureEventArgs.cs
index fd1d0f42c3..f1a0887b60 100644
--- a/src/Avalonia.Base/Input/ScrollGestureEventArgs.cs
+++ b/src/Avalonia.Base/Input/ScrollGestureEventArgs.cs
@@ -6,6 +6,10 @@ namespace Avalonia.Input
     {
         public int Id { get; }
         public Vector Delta { get; }
+        /// <summary>
+        /// When set the ScrollGestureRecognizer should stop its current active scroll gesture.
+        /// </summary>
+        public bool ShouldEndScrollGesture { get; set; }
         private static int _nextId = 1;
 
         public static int GetNextFreeId() => _nextId++;
diff --git a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
index 5a691ce665..0cfe4bada1 100644
--- a/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs
@@ -428,6 +428,8 @@ namespace Avalonia.Controls.Presenters
                 Offset = newOffset;
 
                 e.Handled = !IsScrollChainingEnabled || offsetChanged;
+
+                e.ShouldEndScrollGesture = !IsScrollChainingEnabled && !offsetChanged;
             }
         }
 

From a9fd9f4474b205a5f460e1bce19fe0506e315d80 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 10:56:52 +0100
Subject: [PATCH 144/157] A few more tests.

Trying to get a repro for an issue seen with DataBox but so far unable to repro in a unit test. Anyway, these tests should be useful.
---
 .../ListBoxTests.cs                           | 85 +++++++++++++++++++
 .../VirtualizingStackPanelTests.cs            | 12 +++
 2 files changed, 97 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
index cc824876ac..3f1a3b6342 100644
--- a/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/ListBoxTests.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Linq;
 using System.Reactive.Subjects;
 using Avalonia.Collections;
@@ -663,6 +665,71 @@ namespace Avalonia.Controls.UnitTests
             Assert.True(DataValidationErrors.GetErrors(target).SequenceEqual(new[] { exception }));
         }
 
+        [Fact]
+        public void Handles_Resetting_Items()
+        {
+            var items = new ResettingCollection(100);
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = items,
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
+            };
+
+            Prepare(target);
+
+            var realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{x}"), realized);
+
+            items.Reverse();
+            Layout(target);
+
+            realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{99 - x}"), realized);
+        }
+
+        [Fact]
+        public void Handles_Resetting_Items_With_Existing_Selection_And_AutoScrollToSelectedItem()
+        {
+            var items = new ResettingCollection(100);
+            var target = new ListBox
+            {
+                Template = ListBoxTemplate(),
+                Items = items,
+                ItemTemplate = new FuncDataTemplate<string>((_, __) => new Canvas { Height = 10 }),
+                AutoScrollToSelectedItem = true,
+                SelectedIndex = 1,
+            };
+
+            Prepare(target);
+
+            var realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{x}"), realized);
+
+            items.Reverse();
+            Layout(target);
+
+            realized = target.GetRealizedContainers()
+                .Cast<ListBoxItem>()
+                .Select(x => (string)x.DataContext)
+                .ToList();
+
+            // "Item1" should remain selected, and now be at the bottom of the viewport.
+            Assert.Equal(Enumerable.Range(0, 10).Select(x => $"Item{10 - x}"), realized);
+        }
+
         private static void RaiseKeyEvent(ListBox listBox, Key key, KeyModifiers inputModifiers = 0)
         {
             listBox.RaiseEvent(new KeyEventArgs
@@ -711,5 +778,23 @@ namespace Avalonia.Controls.UnitTests
                 Assert.Equal(true, first.IsSelected);
             }
         }
+
+        private class ResettingCollection : List<string>, INotifyCollectionChanged
+        {
+            public ResettingCollection(int itemCount)
+            {
+                AddRange(Enumerable.Range(0, itemCount).Select(x => $"Item{x}"));
+            }
+
+            public new void Reverse()
+            {
+                base.Reverse();
+                CollectionChanged?.Invoke(
+                    this,
+                    new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Reset));
+            }
+
+            public event NotifyCollectionChangedEventHandler CollectionChanged;
+        }
     }
 }
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index c20d4fa41a..aa521c0d37 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -2,6 +2,7 @@ using System;
 using System.Collections;
 using System.Collections.Generic;
 using System.Collections.ObjectModel;
+using System.Collections.Specialized;
 using System.Linq;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Templates;
@@ -79,6 +80,17 @@ namespace Avalonia.Controls.UnitTests
             AssertRealizedItems(target, itemsControl, 20, 10);
         }
 
+        [Fact]
+        public void Scrolls_To_Index()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            target.ScrollIntoView(20);
+
+            AssertRealizedItems(target, itemsControl, 11, 10);
+        }
+
         [Fact]
         public void Creates_Elements_On_Item_Insert()
         {

From 8600f306e01506567cf641e1147375eb47512404 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 11:16:23 +0100
Subject: [PATCH 145/157] Add redundancy for a problem I can't repro in tests.

There's a problem with `DataBox` that I can't repro in a unit test. Add some redundancy such that if we're still waiting for a viewport update after carrying out a layout pass, force another layout.
---
 src/Avalonia.Controls/VirtualizingStackPanel.cs | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 6c88e6e441..45f1a02a24 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -277,12 +277,25 @@ namespace Avalonia.Controls
                     _isWaitingForViewportUpdate = false;
                 }
 
-                // Try to bring the item into view and do a layout pass.
+                // Try to bring the item into view.
                 _anchorElement.BringIntoView();
 
+                // If the viewport does not contain the item to scroll to, set _isWaitingForViewportUpdate:
+                // this should cause the following chain of events:
+                // - Measure is first done with the old viewport (which will be a no-op, see MeasureOverride)
+                // - The viewport is then updated by the layout system which invalidates our measure
+                // - Measure is then done with the new viewport.
                 _isWaitingForViewportUpdate = !_viewport.Contains(rect);
                 root.LayoutManager.ExecuteLayoutPass();
-                _isWaitingForViewportUpdate = false;
+
+                // If for some reason the layout system didn't give us a new viewport during the layout, we
+                // need to do another layout pass as the one that took place was a no-op.
+                if (_isWaitingForViewportUpdate)
+                {
+                    _isWaitingForViewportUpdate = false;
+                    InvalidateMeasure();
+                    root.LayoutManager.ExecuteLayoutPass();
+                }
 
                 var result = _anchorElement;
                 _anchorElement = null;

From 79b30658f15b11820a5a086923d3fed2bbdf2a07 Mon Sep 17 00:00:00 2001
From: Emmanuel Hansen <emmausssss@gmail.com>
Date: Fri, 13 Jan 2023 10:19:45 +0000
Subject: [PATCH 146/157] add TopLevel.GetTopLevel api

---
 samples/ControlCatalog/Pages/DialogsPage.xaml.cs       |  2 +-
 samples/ControlCatalog/Pages/NotificationsPage.xaml.cs |  2 +-
 src/Avalonia.Controls/ComboBox.cs                      |  2 +-
 src/Avalonia.Controls/Primitives/OverlayPopupHost.cs   |  2 +-
 src/Avalonia.Controls/Primitives/Popup.cs              |  2 +-
 src/Avalonia.Controls/TopLevel.cs                      | 10 ++++++++++
 src/Avalonia.Native/AvaloniaNativeDragSource.cs        |  3 +--
 src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs |  3 +--
 8 files changed, 17 insertions(+), 9 deletions(-)

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 67e9ef4e40..46f25f4d8d 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -397,7 +397,7 @@ CanPickFolder: {storageProvider.CanPickFolder}";
         }
 
         Window GetWindow() => this.VisualRoot as Window ?? throw new NullReferenceException("Invalid Owner");
-        TopLevel GetTopLevel() => this.VisualRoot as TopLevel ?? throw new NullReferenceException("Invalid Owner");
+        TopLevel GetTopLevel() => TopLevel.GetTopLevel(this) ?? throw new NullReferenceException("Invalid Owner");
 
         private void InitializeComponent()
         {
diff --git a/samples/ControlCatalog/Pages/NotificationsPage.xaml.cs b/samples/ControlCatalog/Pages/NotificationsPage.xaml.cs
index bfd49a2c00..6f83e5c366 100644
--- a/samples/ControlCatalog/Pages/NotificationsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/NotificationsPage.xaml.cs
@@ -27,7 +27,7 @@ namespace ControlCatalog.Pages
         {
             base.OnAttachedToVisualTree(e);
 
-            _viewModel.NotificationManager = new Avalonia.Controls.Notifications.WindowNotificationManager(VisualRoot as TopLevel);
+            _viewModel.NotificationManager = new Avalonia.Controls.Notifications.WindowNotificationManager(TopLevel.GetTopLevel(this));
         }
     }
 }
diff --git a/src/Avalonia.Controls/ComboBox.cs b/src/Avalonia.Controls/ComboBox.cs
index 8da99b5f25..6018779e34 100644
--- a/src/Avalonia.Controls/ComboBox.cs
+++ b/src/Avalonia.Controls/ComboBox.cs
@@ -383,7 +383,7 @@ namespace Avalonia.Controls
 
             _subscriptionsOnOpen.Clear();
 
-            var toplevel = this.GetVisualRoot() as TopLevel;
+            var toplevel = TopLevel.GetTopLevel(this);
             if (toplevel != null)
             {
                 toplevel.AddDisposableHandler(PointerWheelChangedEvent, (s, ev) =>
diff --git a/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs b/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
index e0f72cae54..e265f4eb6a 100644
--- a/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
+++ b/src/Avalonia.Controls/Primitives/OverlayPopupHost.cs
@@ -123,7 +123,7 @@ namespace Avalonia.Controls.Primitives
        
         public static IPopupHost CreatePopupHost(Visual target, IAvaloniaDependencyResolver? dependencyResolver)
         {
-            var platform = (target.GetVisualRoot() as TopLevel)?.PlatformImpl?.CreatePopup();
+            var platform = TopLevel.GetTopLevel(target)?.PlatformImpl?.CreatePopup();
             if (platform != null)
                 return new PopupRoot((TopLevel)target.GetVisualRoot()!, platform, dependencyResolver);
             
diff --git a/src/Avalonia.Controls/Primitives/Popup.cs b/src/Avalonia.Controls/Primitives/Popup.cs
index bf79198939..7cac12eabe 100644
--- a/src/Avalonia.Controls/Primitives/Popup.cs
+++ b/src/Avalonia.Controls/Primitives/Popup.cs
@@ -358,7 +358,7 @@ namespace Avalonia.Controls.Primitives
                 return;
             }
             
-            var topLevel = placementTarget.VisualRoot as TopLevel;
+            var topLevel = TopLevel.GetTopLevel(placementTarget);
 
             if (topLevel == null)
             {
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 1f5b8f80d2..9970a0f1c7 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -341,6 +341,16 @@ namespace Avalonia.Controls
         {
             return PlatformImpl?.PointToScreen(p) ?? default;
         }
+
+        /// <summary>
+        /// Gets the <see cref="TopLevel" /> for which the given <see cref="Visual"/> is hosted in.
+        /// </summary>
+        /// <param name="visual">The visual to query its TopLevel</param>
+        /// <returns>The TopLevel</returns>
+        public static TopLevel? GetTopLevel(Visual? visual)
+        {
+            return visual == null ? null : visual.VisualRoot as TopLevel;
+        }
         
         /// <summary>
         /// Creates the layout manager for this <see cref="TopLevel" />.
diff --git a/src/Avalonia.Native/AvaloniaNativeDragSource.cs b/src/Avalonia.Native/AvaloniaNativeDragSource.cs
index bec45c2d71..7f4c462ee0 100644
--- a/src/Avalonia.Native/AvaloniaNativeDragSource.cs
+++ b/src/Avalonia.Native/AvaloniaNativeDragSource.cs
@@ -6,7 +6,6 @@ using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
 using Avalonia.Native.Interop;
-using Avalonia.VisualTree;
 
 namespace Avalonia.Native
 {
@@ -26,7 +25,7 @@ namespace Avalonia.Native
             if (element == null)
                 return null;
             var visual = (Visual)element;
-            return visual.GetVisualRoot() as TopLevel;
+            return TopLevel.GetTopLevel(visual);
         }
 
         class DndCallback : NativeCallbackBase, IAvnDndResultCallback
diff --git a/src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs b/src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs
index cf1bdc1671..998ff4a427 100644
--- a/src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs
+++ b/src/Windows/Avalonia.Win32/Input/WindowsMouseDevice.cs
@@ -1,7 +1,6 @@
 using System;
 using Avalonia.Controls;
 using Avalonia.Input;
-using Avalonia.VisualTree;
 using Avalonia.Win32.Interop;
 
 namespace Avalonia.Win32.Input
@@ -34,7 +33,7 @@ namespace Avalonia.Win32.Input
 
             protected override void PlatformCapture(IInputElement element)
             {
-                var hwnd = (((element as Visual)?.GetVisualRoot() as TopLevel)?.PlatformImpl as WindowImpl)
+                var hwnd = (TopLevel.GetTopLevel(element as Visual)?.PlatformImpl as WindowImpl)
                     ?.Handle.Handle;
 
                 if (hwnd.HasValue && hwnd != IntPtr.Zero)

From d0f479d80cf4f805f2357042fd4f3138f7034d42 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Fri, 13 Jan 2023 13:29:30 +0100
Subject: [PATCH 147/157] Don't recycle focused element.

Fixes #9269
---
 .../VirtualizingStackPanel.cs                 | 56 ++++++++++++++++---
 .../VirtualizingStackPanelTests.cs            | 53 +++++++++++++++++-
 2 files changed, 99 insertions(+), 10 deletions(-)

diff --git a/src/Avalonia.Controls/VirtualizingStackPanel.cs b/src/Avalonia.Controls/VirtualizingStackPanel.cs
index 45f1a02a24..3f539ce198 100644
--- a/src/Avalonia.Controls/VirtualizingStackPanel.cs
+++ b/src/Avalonia.Controls/VirtualizingStackPanel.cs
@@ -26,7 +26,7 @@ namespace Avalonia.Controls
             AvaloniaProperty.RegisterAttached<VirtualizingStackPanel, Control, bool>("ItemIsOwnContainer");
 
         private static readonly Rect s_invalidViewport = new(double.PositiveInfinity, double.PositiveInfinity, 0, 0);
-        private readonly Action<Control> _recycleElement;
+        private readonly Action<Control, int> _recycleElement;
         private readonly Action<Control> _recycleElementOnItemRemoved;
         private readonly Action<Control, int, int> _updateElementIndex;
         private int _anchorIndex = -1;
@@ -38,6 +38,8 @@ namespace Avalonia.Controls
         private RealizedElementList? _realizedElements;
         private Rect _viewport = s_invalidViewport;
         private Stack<Control>? _recyclePool;
+        private Control? _unrealizedFocusedElement;
+        private int _unrealizedFocusedIndex = -1;
 
         public VirtualizingStackPanel()
         {
@@ -167,7 +169,7 @@ namespace Avalonia.Controls
                     _realizedElements.ItemsInserted(e.NewStartingIndex, e.NewItems!.Count, _updateElementIndex);
                     break;
                 case NotifyCollectionChangedAction.Reset:
-                    _realizedElements.RecycleAllElements(_recycleElementOnItemRemoved);
+                    _realizedElements.ItemsReset(_recycleElementOnItemRemoved);
                     break;
             }
         }
@@ -482,6 +484,13 @@ namespace Avalonia.Controls
             var generator = ItemContainerGenerator!;
             var item = items[index];
 
+            if (_unrealizedFocusedIndex == index)
+            {
+                var element = _unrealizedFocusedElement;
+                _unrealizedFocusedElement = null;
+                _unrealizedFocusedIndex = -1;
+                return element;
+            }
             if (_recyclePool?.Count > 0)
             {
                 var recycled = _recyclePool.Pop();
@@ -515,7 +524,7 @@ namespace Avalonia.Controls
             return index * estimatedElementSize;
         }
 
-        private void RecycleElement(Control element)
+        private void RecycleElement(Control element, int index)
         {
             Debug.Assert(ItemContainerGenerator is not null);
             
@@ -523,6 +532,11 @@ namespace Avalonia.Controls
             {
                 element.IsVisible = false;
             }
+            else if (element.IsKeyboardFocusWithin)
+            {
+                _unrealizedFocusedElement = element;
+                _unrealizedFocusedIndex = index;
+            }
             else
             {
                 ItemContainerGenerator!.ClearItemContainer(element);
@@ -932,12 +946,33 @@ namespace Avalonia.Controls
                 }
             }
 
+            /// <summary>
+            /// Recycles all elements in response to the source collection being reset.
+            /// </summary>
+            /// <param name="recycleElement">A method used to recycle elements.</param>
+            public void ItemsReset(Action<Control> recycleElement)
+            {
+                if (_elements is null || _elements.Count == 0)
+                    return;
+
+                foreach (var e in _elements)
+                {
+                    if (e is not null)
+                        recycleElement(e);
+                }
+
+                _startU = _firstIndex = 0;
+                _elements?.Clear();
+                _sizes?.Clear();
+
+            }
+
             /// <summary>
             /// Recycles elements before a specific index.
             /// </summary>
             /// <param name="index">The index in the source collection of new first element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsBefore(int index, Action<Control> recycleElement)
+            public void RecycleElementsBefore(int index, Action<Control, int> recycleElement)
             {
                 if (index <= FirstIndex || _elements is null || _elements.Count == 0)
                     return;
@@ -953,7 +988,7 @@ namespace Avalonia.Controls
                     for (var i = 0; i < endIndex; ++i)
                     {
                         if (_elements[i] is Control e)
-                            recycleElement(e);
+                            recycleElement(e, i + FirstIndex);
                     }
 
                     _elements.RemoveRange(0, endIndex);
@@ -967,7 +1002,7 @@ namespace Avalonia.Controls
             /// </summary>
             /// <param name="index">The index in the source collection of new last element.</param>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleElementsAfter(int index, Action<Control> recycleElement)
+            public void RecycleElementsAfter(int index, Action<Control, int> recycleElement)
             {
                 if (index >= LastIndex || _elements is null || _elements.Count == 0)
                     return;
@@ -984,7 +1019,7 @@ namespace Avalonia.Controls
                     for (var i = startIndex; i < count; ++i)
                     {
                         if (_elements[i] is Control e)
-                            recycleElement(e);
+                            recycleElement(e, i + FirstIndex);
                     }
 
                     _elements.RemoveRange(startIndex, _elements.Count - startIndex);
@@ -996,15 +1031,18 @@ namespace Avalonia.Controls
             /// Recycles all realized elements.
             /// </summary>
             /// <param name="recycleElement">A method used to recycle elements.</param>
-            public void RecycleAllElements(Action<Control> recycleElement)
+            public void RecycleAllElements(Action<Control, int> recycleElement)
             {
                 if (_elements is null || _elements.Count == 0)
                     return;
 
+                var i = FirstIndex;
+
                 foreach (var e in _elements)
                 {
                     if (e is not null)
-                        recycleElement(e);
+                        recycleElement(e, i);
+                    ++i;
                 }
 
                 _startU = _firstIndex = 0;
diff --git a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
index aa521c0d37..f1dd874c71 100644
--- a/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/VirtualizingStackPanelTests.cs
@@ -227,6 +227,57 @@ namespace Avalonia.Controls.UnitTests
             Assert.Null(removed.VisualParent);
         }
 
+        [Fact]
+        public void Does_Not_Recycle_Focused_Element()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            target.GetRealizedElements().First()!.Focus();
+            Assert.True(target.GetRealizedElements().First()!.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            Assert.All(target.GetRealizedElements(), x => Assert.False(x!.IsKeyboardFocusWithin));
+        }
+
+        [Fact]
+        public void Removing_Item_Of_Focused_Element_Clears_Focus()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            var focused = target.GetRealizedElements().First()!;
+            focused.Focus();
+            Assert.True(focused.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            Assert.All(target.GetRealizedElements(), x => Assert.False(x!.IsKeyboardFocusWithin));
+            Assert.All(target.GetRealizedElements(), x => Assert.NotSame(focused, x));
+        }
+
+        [Fact]
+        public void Scrolling_Back_To_Focused_Element_Uses_Correct_Element()
+        {
+            using var app = App();
+            var (target, scroll, itemsControl) = CreateTarget();
+
+            var focused = target.GetRealizedElements().First()!;
+            focused.Focus();
+            Assert.True(focused.IsKeyboardFocusWithin);
+
+            scroll.Offset = new Vector(0, 200);
+            Layout(target);
+
+            scroll.Offset = new Vector(0, 0);
+            Layout(target);
+
+            Assert.Same(focused, target.GetRealizedElements().First());
+        }
+
         private static IReadOnlyList<int> GetRealizedIndexes(VirtualizingStackPanel target, ItemsControl itemsControl)
         {
             return target.GetRealizedElements()
@@ -326,6 +377,6 @@ namespace Avalonia.Controls.UnitTests
                 }.RegisterInNameScope(ns));
         }
 
-        private static IDisposable App() => UnitTestApplication.Start();
+        private static IDisposable App() => UnitTestApplication.Start(TestServices.RealFocus);
     }
 }

From 7cd51c91615e3b02e8aa0827d179e77c315db89c Mon Sep 17 00:00:00 2001
From: Max Katz <maxkatz6@outlook.com>
Date: Fri, 13 Jan 2023 14:34:22 -0500
Subject: [PATCH 148/157] Update
 samples/ControlCatalog/Pages/DialogsPage.xaml.cs

---
 samples/ControlCatalog/Pages/DialogsPage.xaml.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
index 46f25f4d8d..8db6e76dca 100644
--- a/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
+++ b/samples/ControlCatalog/Pages/DialogsPage.xaml.cs
@@ -396,7 +396,7 @@ CanPickFolder: {storageProvider.CanPickFolder}";
             return item.TryGetUri(out var uri) ? uri.ToString() : item.Name;
         }
 
-        Window GetWindow() => this.VisualRoot as Window ?? throw new NullReferenceException("Invalid Owner");
+        Window GetWindow() => TopLevel.GetTopLevel(this) as Window ?? throw new NullReferenceException("Invalid Owner");
         TopLevel GetTopLevel() => TopLevel.GetTopLevel(this) ?? throw new NullReferenceException("Invalid Owner");
 
         private void InitializeComponent()

From 473cda2d3e92e511a4f1917d18c5cb641394b426 Mon Sep 17 00:00:00 2001
From: Benedikt Stebner <Gillibald@users.noreply.github.com>
Date: Fri, 13 Jan 2023 21:56:10 +0100
Subject: [PATCH 149/157] [Direct2D1] Don't dispose DirectWrite GlyphRun
 explicitly

---
 src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs b/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
index 638aaf08d6..67418613a4 100644
--- a/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
+++ b/src/Windows/Avalonia.Direct2D1/Media/GlyphRunImpl.cs
@@ -14,7 +14,8 @@ namespace Avalonia.Direct2D1.Media
 
         public void Dispose()
         {
-            GlyphRun?.Dispose();
+            //SharpDX already handles this.
+            //GlyphRun?.Dispose();
         }
 
         public IReadOnlyList<float> GetIntersections(float lowerBound, float upperBound)

From dec8c1c586be564857dea712c36851918267fe80 Mon Sep 17 00:00:00 2001
From: Julien Lebosquain <julien@lebosquain.net>
Date: Fri, 13 Jan 2023 16:33:28 +0100
Subject: [PATCH 150/157] Used Memory/Span instead of
 CharacterBufferReference/Range

+ GlyphRun uses ReadOnlyMemory for characters
---
 src/Avalonia.Base/Media/FormattedText.cs      |   7 +-
 src/Avalonia.Base/Media/GlyphRun.cs           |  93 +++---
 .../TextFormatting/CharacterBufferRange.cs    | 275 ------------------
 .../CharacterBufferReference.cs               | 115 --------
 .../TextFormatting/FormattedTextSource.cs     |  14 +-
 .../TextFormatting/InterWordJustification.cs  |   6 +-
 .../Media/TextFormatting/ShapedBuffer.cs      |  24 +-
 .../Media/TextFormatting/ShapedTextRun.cs     |  16 +-
 .../Media/TextFormatting/TextCharacters.cs    | 123 +++-----
 .../TextFormatting/TextEllipsisHelper.cs      |   4 +-
 .../Media/TextFormatting/TextFormatterImpl.cs | 153 ++++++----
 .../Media/TextFormatting/TextRun.cs           |  21 +-
 .../Media/TextFormatting/TextShaper.cs        |   6 +-
 .../Media/TextFormatting/Unicode/BiDiData.cs  |   2 +-
 .../Media/TextFormatting/Unicode/Codepoint.cs |  67 +----
 .../Unicode/CodepointEnumerator.cs            |   6 +-
 .../Media/TextFormatting/Unicode/Grapheme.cs  |  14 +-
 .../Unicode/GraphemeEnumerator.cs             |  14 +-
 .../Unicode/LineBreakEnumerator.cs            |  13 +-
 .../Media/TextFormatting/UnshapedTextRun.cs   |  44 +--
 src/Avalonia.Base/Platform/ITextShaperImpl.cs |   6 +-
 src/Avalonia.Controls/TextBlock.cs            |  15 +-
 src/Avalonia.Controls/TextBox.cs              |   6 +-
 .../TextBoxTextInputMethodClient.cs           |   6 +-
 .../HeadlessPlatformStubs.cs                  |   6 +-
 src/Skia/Avalonia.Skia/TextShaperImpl.cs      |  33 ++-
 .../Media/TextShaperImpl.cs                   |  40 ++-
 .../Media/TextFormatting/BiDiClassTests.cs    |   2 +-
 .../GraphemeBreakClassTrieGeneratorTests.cs   |  15 +-
 .../LineBreakEnumuratorTests.cs               |   8 +-
 .../Presenters/TextPresenter_Tests.cs         |   2 +-
 .../Media/GlyphRunTests.cs                    |  12 +-
 .../TextFormatting/SingleBufferTextSource.cs  |  11 +-
 .../TextFormatting/TextFormatterTests.cs      |   4 +-
 .../Media/TextFormatting/TextLayoutTests.cs   |  38 +--
 .../Media/TextFormatting/TextLineTests.cs     |   9 +-
 .../Media/TextFormatting/TextShaperTests.cs   |   2 +-
 .../HarfBuzzTextShaperImpl.cs                 |  69 +++--
 .../Avalonia.UnitTests/MockTextShaperImpl.cs  |  14 +-
 tests/Avalonia.UnitTests/TextTestHelper.cs    |  15 +
 40 files changed, 457 insertions(+), 873 deletions(-)
 delete mode 100644 src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
 delete mode 100644 src/Avalonia.Base/Media/TextFormatting/CharacterBufferReference.cs
 create mode 100644 tests/Avalonia.UnitTests/TextTestHelper.cs

diff --git a/src/Avalonia.Base/Media/FormattedText.cs b/src/Avalonia.Base/Media/FormattedText.cs
index 774580415a..0bab473442 100644
--- a/src/Avalonia.Base/Media/FormattedText.cs
+++ b/src/Avalonia.Base/Media/FormattedText.cs
@@ -1610,12 +1610,9 @@ namespace Avalonia.Media
 
                 var thatFormatRider = new SpanRider(_that._formatRuns, _that._latestPosition, textSourceCharacterIndex);
 
+                var text = _that._text.AsMemory(textSourceCharacterIndex, thatFormatRider.Length);
                 TextRunProperties properties = (GenericTextRunProperties)thatFormatRider.CurrentElement!;
-
-                var textCharacters = new TextCharacters(_that._text, textSourceCharacterIndex, thatFormatRider.Length,
-                    properties);
-
-                return textCharacters;
+                return new TextCharacters(text, properties);
             }
         }
     }
diff --git a/src/Avalonia.Base/Media/GlyphRun.cs b/src/Avalonia.Base/Media/GlyphRun.cs
index 811479fde8..fc4bc6aa1c 100644
--- a/src/Avalonia.Base/Media/GlyphRun.cs
+++ b/src/Avalonia.Base/Media/GlyphRun.cs
@@ -21,7 +21,7 @@ namespace Avalonia.Media
         private Point? _baselineOrigin;
         private GlyphRunMetrics? _glyphRunMetrics;
 
-        private IReadOnlyList<char> _characters;
+        private ReadOnlyMemory<char> _characters;
         private IReadOnlyList<ushort> _glyphIndices;
         private IReadOnlyList<double>? _glyphAdvances;
         private IReadOnlyList<Vector>? _glyphOffsets;
@@ -41,7 +41,7 @@ namespace Avalonia.Media
         public GlyphRun(
             IGlyphTypeface glyphTypeface,
             double fontRenderingEmSize,
-            IReadOnlyList<char> characters,
+            ReadOnlyMemory<char> characters,
             IReadOnlyList<ushort> glyphIndices,
             IReadOnlyList<double>? glyphAdvances = null,
             IReadOnlyList<Vector>? glyphOffsets = null,
@@ -141,7 +141,7 @@ namespace Avalonia.Media
         /// <summary>
         ///     Gets or sets the list of UTF16 code points that represent the Unicode content of the <see cref="GlyphRun"/>.
         /// </summary>
-        public IReadOnlyList<char> Characters
+        public ReadOnlyMemory<char> Characters
         {
             get => _characters;
             set => Set(ref _characters, value);
@@ -600,9 +600,9 @@ namespace Avalonia.Media
                     }
                 }
 
-                if (Characters != null)
+                if (!Characters.IsEmpty)
                 {
-                    clusterLength = Characters.Count - characterLength;
+                    clusterLength = Characters.Length - characterLength;
                 }
                 else
                 {
@@ -653,10 +653,10 @@ namespace Avalonia.Media
             }
             else
             {
-                if (Characters != null && Characters.Count > 0)
+                if (!Characters.IsEmpty)
                 {
                     firstCluster = 0;
-                    lastCluster = Characters.Count - 1;
+                    lastCluster = Characters.Length - 1;
                 }
             }
 
@@ -716,14 +716,15 @@ namespace Avalonia.Media
             glyphCount = 0;
             newLineLength = 0;
             var trailingWhitespaceLength = 0;
+            var charactersSpan = _characters.Span;
 
-            if (Characters != null)
+            if (!charactersSpan.IsEmpty)
             {
                 if (GlyphClusters == null)
                 {
-                    for (var i = _characters.Count - 1; i >= 0;)
+                    for (var i = charactersSpan.Length - 1; i >= 0;)
                     {
-                        var codepoint = Codepoint.ReadAt(_characters, i, out var count);
+                        var codepoint = Codepoint.ReadAt(charactersSpan, i, out var count);
 
                         if (!codepoint.IsWhiteSpace)
                         {
@@ -743,55 +744,52 @@ namespace Avalonia.Media
                 }
                 else
                 {
-                    if (Characters.Count > 0)
+                    var characterIndex = charactersSpan.Length - 1;
+
+                    for (var i = GlyphClusters.Count - 1; i >= 0; i--)
                     {
-                        var characterIndex = Characters.Count - 1;
+                        var currentCluster = GlyphClusters[i];
+                        var codepoint = Codepoint.ReadAt(charactersSpan, characterIndex, out var characterLength);
 
-                        for (var i = GlyphClusters.Count - 1; i >= 0; i--)
-                        {
-                            var currentCluster = GlyphClusters[i];
-                            var codepoint = Codepoint.ReadAt(_characters, characterIndex, out var characterLength);
+                        characterIndex -= characterLength;
 
-                            characterIndex -= characterLength;
+                        if (!codepoint.IsWhiteSpace)
+                        {
+                            break;
+                        }
 
-                            if (!codepoint.IsWhiteSpace)
-                            {
-                                break;
-                            }
+                        var clusterLength = 1;
 
-                            var clusterLength = 1;
+                        while (i - 1 >= 0)
+                        {
+                            var nextCluster = GlyphClusters[i - 1];
 
-                            while (i - 1 >= 0)
+                            if (currentCluster == nextCluster)
                             {
-                                var nextCluster = GlyphClusters[i - 1];
+                                clusterLength++;
+                                i--;
 
-                                if (currentCluster == nextCluster)
+                                if(characterIndex >= 0)
                                 {
-                                    clusterLength++;
-                                    i--;
-
-                                    if(characterIndex >= 0)
-                                    {
-                                        codepoint = Codepoint.ReadAt(_characters, characterIndex, out characterLength);
+                                    codepoint = Codepoint.ReadAt(charactersSpan, characterIndex, out characterLength);
 
-                                        characterIndex -= characterLength;
-                                    }
-
-                                    continue;
+                                    characterIndex -= characterLength;
                                 }
 
-                                break;
-                            }
-
-                            if (codepoint.IsBreakChar)
-                            {
-                                newLineLength += clusterLength;
+                                continue;
                             }
 
-                            trailingWhitespaceLength += clusterLength;
+                            break;
+                        }
 
-                            glyphCount++;
+                        if (codepoint.IsBreakChar)
+                        {
+                            newLineLength += clusterLength;
                         }
+
+                        trailingWhitespaceLength += clusterLength;
+
+                        glyphCount++;
                     }
                 }
             }
@@ -804,14 +802,15 @@ namespace Avalonia.Media
             glyphCount = 0;
             newLineLength = 0;
             var trailingWhitespaceLength = 0;
+            var charactersSpan = Characters.Span;
 
-            if (Characters != null)
+            if (!charactersSpan.IsEmpty)
             {
                 if (GlyphClusters == null)
                 {
-                    for (var i = 0; i < Characters.Count;)
+                    for (var i = 0; i < charactersSpan.Length;)
                     {
-                        var codepoint = Codepoint.ReadAt(_characters, i, out var count);
+                        var codepoint = Codepoint.ReadAt(charactersSpan, i, out var count);
 
                         if (!codepoint.IsWhiteSpace)
                         {
@@ -836,7 +835,7 @@ namespace Avalonia.Media
                     for (var i = 0; i < GlyphClusters.Count; i++)
                     {
                         var currentCluster = GlyphClusters[i];
-                        var codepoint = Codepoint.ReadAt(_characters, characterIndex, out var characterLength);
+                        var codepoint = Codepoint.ReadAt(charactersSpan, characterIndex, out var characterLength);
 
                         characterIndex += characterLength;
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
deleted file mode 100644
index 499026e8b3..0000000000
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferRange.cs
+++ /dev/null
@@ -1,275 +0,0 @@
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Runtime.CompilerServices;
-using Avalonia.Utilities;
-
-namespace Avalonia.Media.TextFormatting
-{
-    public readonly struct CharacterBufferRange : IReadOnlyList<char>
-    {
-        /// <summary>
-        /// Getting an empty character string
-        /// </summary>
-        public static CharacterBufferRange Empty => new CharacterBufferRange();
-
-        /// <summary>
-        /// Construct <see cref="CharacterBufferRange"/> from character array
-        /// </summary>
-        /// <param name="characterArray">character array</param>
-        /// <param name="offsetToFirstChar">character buffer offset to the first character</param>
-        /// <param name="characterLength">character length</param>
-        public CharacterBufferRange(
-            char[] characterArray,
-            int offsetToFirstChar,
-            int characterLength
-            )
-            : this(
-                new CharacterBufferReference(characterArray, offsetToFirstChar),
-                characterLength
-                )
-        { }
-
-        /// <summary>
-        /// Construct <see cref="CharacterBufferRange"/> from string
-        /// </summary>
-        /// <param name="characterString">character string</param>
-        /// <param name="offsetToFirstChar">character buffer offset to the first character</param>
-        /// <param name="characterLength">character length</param>
-        public CharacterBufferRange(
-            string characterString,
-            int offsetToFirstChar,
-            int characterLength
-            )
-            : this(
-                new CharacterBufferReference(characterString, offsetToFirstChar),
-                characterLength
-                )
-        { }
-
-        /// <summary>
-        /// Construct a <see cref="CharacterBufferRange"/> from <see cref="CharacterBufferReference"/>
-        /// </summary>
-        /// <param name="characterBufferReference">character buffer reference</param>
-        /// <param name="characterLength">number of characters</param>
-        public CharacterBufferRange(
-            CharacterBufferReference characterBufferReference,
-            int characterLength
-            )
-        {
-            if (characterLength < 0)
-            {
-                throw new ArgumentOutOfRangeException("characterLength", "ParameterCannotBeNegative");
-            }
-
-            int maxLength = characterBufferReference.CharacterBuffer.Length > 0 ?
-                characterBufferReference.CharacterBuffer.Length - characterBufferReference.OffsetToFirstChar :
-                0;
-
-            if (characterLength > maxLength)
-            {
-                throw new ArgumentOutOfRangeException("characterLength", $"ParameterCannotBeGreaterThan {maxLength}");
-            }
-
-            CharacterBufferReference = characterBufferReference;
-            Length = characterLength;
-        }
-
-        /// <summary>
-        /// Construct a <see cref="CharacterBufferRange"/> from part of another <see cref="CharacterBufferRange"/>
-        /// </summary>
-        internal CharacterBufferRange(
-            CharacterBufferRange characterBufferRange,
-            int offsetToFirstChar,
-            int characterLength
-            ) :
-            this(
-                characterBufferRange.CharacterBuffer,
-                characterBufferRange.OffsetToFirstChar + offsetToFirstChar,
-                characterLength
-                )
-        { }
-
-
-        /// <summary>
-        /// Construct a <see cref="CharacterBufferRange"/> from string
-        /// </summary>
-        internal CharacterBufferRange(
-            string charString
-            ) :
-            this(
-                charString,
-                0,
-                charString.Length
-                )
-        { }
-
-
-        /// <summary>
-        /// Construct <see cref="CharacterBufferRange"/> from memory buffer
-        /// </summary>
-        internal CharacterBufferRange(
-            ReadOnlyMemory<char> charBuffer,
-            int offsetToFirstChar,
-            int characterLength
-            ) :
-            this(
-                new CharacterBufferReference(charBuffer, offsetToFirstChar),
-                characterLength
-                )
-        { }
-
-
-        /// <summary>
-        /// Construct a <see cref="CharacterBufferRange"/> by extracting text info from a text run
-        /// </summary>
-        internal CharacterBufferRange(TextRun textRun)
-        {
-            CharacterBufferReference = textRun.CharacterBufferReference;
-            Length = textRun.Length;
-        }
-
-        public char this[int index]
-        {
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get
-            {
-#if DEBUG
-                if (index.CompareTo(0) < 0 || index.CompareTo(Length) > 0)
-                {
-                    throw new ArgumentOutOfRangeException(nameof(index));
-                }
-#endif
-                return CharacterBuffer.Span[CharacterBufferReference.OffsetToFirstChar + index];
-            }
-        }
-
-        /// <summary>
-        /// Gets a reference to the character buffer
-        /// </summary>
-        public CharacterBufferReference CharacterBufferReference { get; }
-
-        /// <summary>
-        /// Gets the number of characters in text source character store
-        /// </summary>
-        public int Length { get; }
-
-        /// <summary>
-        /// Gets a span from the character buffer range
-        /// </summary>
-        public ReadOnlySpan<char> Span => CharacterBuffer.Span.Slice(OffsetToFirstChar, Length);
-
-        /// <summary>
-        /// Gets the character memory buffer
-        /// </summary>
-        internal ReadOnlyMemory<char> CharacterBuffer => CharacterBufferReference.CharacterBuffer;
-
-        /// <summary>
-        /// Gets the character offset relative to the beginning of buffer to 
-        /// the first character of the run
-        /// </summary>
-        internal int OffsetToFirstChar => CharacterBufferReference.OffsetToFirstChar;
-
-        /// <summary>
-        /// Indicate whether the character buffer range is empty
-        /// </summary>
-        internal bool IsEmpty => CharacterBuffer.Length == 0 || Length <= 0;
-
-        internal CharacterBufferRange Take(int length)
-        {
-            if (IsEmpty)
-            {
-                return this;
-            }
-
-            if (length > Length)
-            {
-                throw new ArgumentOutOfRangeException(nameof(length));
-            }
-
-            return new CharacterBufferRange(CharacterBufferReference, length);
-        }
-
-        internal CharacterBufferRange Skip(int length)
-        {
-            if (IsEmpty)
-            {
-                return this;
-            }
-
-            if (length > Length)
-            {
-                throw new ArgumentOutOfRangeException(nameof(length));
-            }
-
-            if (length == Length)
-            {
-                return new CharacterBufferRange(new CharacterBufferReference(), 0);
-            }
-
-            var characterBufferReference = new CharacterBufferReference(CharacterBuffer, OffsetToFirstChar + length);
-
-            return new CharacterBufferRange(characterBufferReference, Length - length);
-        }
-
-        /// <summary>
-        /// Compute hash code
-        /// </summary>
-        public override int GetHashCode()
-        {
-            return CharacterBufferReference.GetHashCode() ^ Length;
-        }
-
-        /// <summary>
-        /// Test equality with the input object
-        /// </summary>
-        /// <param name="obj"> The object to test </param>
-        public override bool Equals(object? obj)
-        {
-            if (obj is CharacterBufferRange range)
-            {
-                return Equals(range);
-            }
-
-            return false;
-        }
-
-        /// <summary>
-        /// Test equality with the input CharacterBufferRange
-        /// </summary>
-        /// <param name="value"> The CharacterBufferRange value to test </param>
-        public bool Equals(CharacterBufferRange value)
-        {
-            return CharacterBufferReference.Equals(value.CharacterBufferReference)
-                && Length == value.Length;
-        }
-
-        /// <summary>
-        /// Compare two CharacterBufferRange for equality
-        /// </summary>
-        /// <param name="left">left operand</param>
-        /// <param name="right">right operand</param>
-        /// <returns>whether or not two operands are equal</returns>
-        public static bool operator ==(CharacterBufferRange left, CharacterBufferRange right)
-        {
-            return left.Equals(right);
-        }
-
-        /// <summary>
-        /// Compare two CharacterBufferRange for inequality
-        /// </summary>
-        /// <param name="left">left operand</param>
-        /// <param name="right">right operand</param>
-        /// <returns>whether or not two operands are equal</returns>
-        public static bool operator !=(CharacterBufferRange left, CharacterBufferRange right)
-        {
-            return !(left == right);
-        }
-
-        int IReadOnlyCollection<char>.Count => Length;
-
-        public IEnumerator<char> GetEnumerator() => new ImmutableReadOnlyListStructEnumerator<char>(this);
-
-        IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
-    }
-}
diff --git a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferReference.cs b/src/Avalonia.Base/Media/TextFormatting/CharacterBufferReference.cs
deleted file mode 100644
index 672fcf3377..0000000000
--- a/src/Avalonia.Base/Media/TextFormatting/CharacterBufferReference.cs
+++ /dev/null
@@ -1,115 +0,0 @@
-using System;
-
-namespace Avalonia.Media.TextFormatting
-{
-    /// <summary>
-    /// Text character buffer reference
-    /// </summary>
-    public readonly struct CharacterBufferReference : IEquatable<CharacterBufferReference>
-    {
-        /// <summary>
-        /// Construct character buffer reference from character array
-        /// </summary>
-        /// <param name="characterArray">character array</param>
-        /// <param name="offsetToFirstChar">character buffer offset to the first character</param>
-        public CharacterBufferReference(char[] characterArray, int offsetToFirstChar = 0)
-            : this(characterArray.AsMemory(), offsetToFirstChar)
-        { }
-
-        /// <summary>
-        /// Construct character buffer reference from string
-        /// </summary>
-        /// <param name="characterString">character string</param>
-        /// <param name="offsetToFirstChar">character buffer offset to the first character</param>
-        public CharacterBufferReference(string characterString, int offsetToFirstChar = 0)
-            : this(characterString.AsMemory(), offsetToFirstChar)
-        { }
-      
-        /// <summary>
-        /// Construct character buffer reference from memory buffer
-        /// </summary>
-        internal CharacterBufferReference(ReadOnlyMemory<char> characterBuffer, int offsetToFirstChar = 0)
-        {
-            if (offsetToFirstChar < 0)
-            {
-                throw new ArgumentOutOfRangeException("offsetToFirstChar", "ParameterCannotBeNegative");
-            }
-
-            // maximum offset is one less than CharacterBuffer.Count, except that zero is always a valid offset
-            // even in the case of an empty or null character buffer
-            var maxOffset = characterBuffer.Length == 0 ? 0 : Math.Max(0, characterBuffer.Length - 1);
-            if (offsetToFirstChar > maxOffset)
-            {
-                throw new ArgumentOutOfRangeException("offsetToFirstChar", $"ParameterCannotBeGreaterThan, {maxOffset}");
-            }
-
-            CharacterBuffer = characterBuffer;
-            OffsetToFirstChar = offsetToFirstChar;
-        }
-
-        /// <summary>
-        /// Gets the character memory buffer
-        /// </summary>
-        public ReadOnlyMemory<char> CharacterBuffer { get; }
-
-        /// <summary>
-        /// Gets the character offset relative to the beginning of buffer to 
-        /// the first character of the run
-        /// </summary>
-        public int OffsetToFirstChar { get; }
-
-        /// <summary>
-        /// Compute hash code
-        /// </summary>
-        public override int GetHashCode()
-        {
-            return CharacterBuffer.IsEmpty ? 0 : CharacterBuffer.GetHashCode();
-        }
-
-        /// <summary>
-        /// Test equality with the input object 
-        /// </summary>
-        /// <param name="obj"> The object to test. </param>
-        public override bool Equals(object? obj)
-        {
-            if (obj is CharacterBufferReference reference)
-            {
-                return Equals(reference);
-            }
-
-            return false;
-        }
-
-        /// <summary>
-        /// Test equality with the input CharacterBufferReference
-        /// </summary>
-        /// <param name="value"> The characterBufferReference value to test </param>
-        public bool Equals(CharacterBufferReference value)
-        {
-            return CharacterBuffer.Equals(value.CharacterBuffer);
-        }
-
-        /// <summary>
-        /// Compare two CharacterBufferReference for equality
-        /// </summary>
-        /// <param name="left">left operand</param>
-        /// <param name="right">right operand</param>
-        /// <returns>whether or not two operands are equal</returns>
-        public static bool operator ==(CharacterBufferReference left, CharacterBufferReference right)
-        {
-            return left.Equals(right);
-        }
-
-        /// <summary>
-        /// Compare two CharacterBufferReference for inequality
-        /// </summary>
-        /// <param name="left">left operand</param>
-        /// <param name="right">right operand</param>
-        /// <returns>whether or not two operands are equal</returns>
-        public static bool operator !=(CharacterBufferReference left, CharacterBufferReference right)
-        {
-            return !(left == right);
-        }
-    }
-}
-
diff --git a/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs b/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
index 49d94b511d..5c28989c7d 100644
--- a/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/FormattedTextSource.cs
@@ -7,14 +7,14 @@ namespace Avalonia.Media.TextFormatting
 {
     internal readonly struct FormattedTextSource : ITextSource
     {
-        private readonly CharacterBufferRange _text;
+        private readonly string _text;
         private readonly TextRunProperties _defaultProperties;
         private readonly IReadOnlyList<ValueSpan<TextRunProperties>>? _textModifier;
 
         public FormattedTextSource(string text, TextRunProperties defaultProperties,
             IReadOnlyList<ValueSpan<TextRunProperties>>? textModifier)
         {
-            _text = new CharacterBufferRange(text);
+            _text = text;
             _defaultProperties = defaultProperties;
             _textModifier = textModifier;
         }
@@ -26,7 +26,7 @@ namespace Avalonia.Media.TextFormatting
                 return null;
             }
 
-            var runText = _text.Skip(textSourceIndex);
+            var runText = _text.AsSpan(textSourceIndex);
 
             if (runText.IsEmpty)
             {
@@ -35,7 +35,7 @@ namespace Avalonia.Media.TextFormatting
 
             var textStyleRun = CreateTextStyleRun(runText, textSourceIndex, _defaultProperties, _textModifier);
 
-            return new TextCharacters(runText.Take(textStyleRun.Length).CharacterBufferReference, textStyleRun.Length, textStyleRun.Value);
+            return new TextCharacters(_text.AsMemory(textSourceIndex, textStyleRun.Length), textStyleRun.Value);
         }
 
         /// <summary>
@@ -48,7 +48,7 @@ namespace Avalonia.Media.TextFormatting
         /// <returns>
         /// The created text style run.
         /// </returns>
-        private static ValueSpan<TextRunProperties> CreateTextStyleRun(CharacterBufferRange text, int firstTextSourceIndex,
+        private static ValueSpan<TextRunProperties> CreateTextStyleRun(ReadOnlySpan<char> text, int firstTextSourceIndex,
             TextRunProperties defaultProperties, IReadOnlyList<ValueSpan<TextRunProperties>>? textModifier)
         {
             if (textModifier == null || textModifier.Count == 0)
@@ -122,7 +122,7 @@ namespace Avalonia.Media.TextFormatting
             return new ValueSpan<TextRunProperties>(firstTextSourceIndex, length, currentProperties);
         }
 
-        private static int CoerceLength(CharacterBufferRange text, int length)
+        private static int CoerceLength(ReadOnlySpan<char> text, int length)
         {
             var finalLength = 0;
 
@@ -132,7 +132,7 @@ namespace Avalonia.Media.TextFormatting
             {
                 var grapheme = graphemeEnumerator.Current;
 
-                finalLength += grapheme.Length;
+                finalLength += grapheme.Text.Length;
 
                 if (finalLength >= length)
                 {
diff --git a/src/Avalonia.Base/Media/TextFormatting/InterWordJustification.cs b/src/Avalonia.Base/Media/TextFormatting/InterWordJustification.cs
index 21e8ce089a..b518d47a6d 100644
--- a/src/Avalonia.Base/Media/TextFormatting/InterWordJustification.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/InterWordJustification.cs
@@ -50,14 +50,14 @@ namespace Avalonia.Media.TextFormatting
 
             foreach (var textRun in lineImpl.TextRuns)
             {
-                var text = new CharacterBufferRange(textRun);
+                var text = textRun.Text;
 
                 if (text.IsEmpty)
                 {
                     continue;
                 }
 
-                var lineBreakEnumerator = new LineBreakEnumerator(text);
+                var lineBreakEnumerator = new LineBreakEnumerator(text.Span);
 
                 while (lineBreakEnumerator.MoveNext())
                 {
@@ -84,7 +84,7 @@ namespace Avalonia.Media.TextFormatting
 
             foreach (var textRun in lineImpl.TextRuns)
             {
-                var text = textRun.CharacterBufferReference.CharacterBuffer;
+                var text = textRun.Text;
 
                 if (text.IsEmpty)
                 {
diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
index af896b426d..b05fab08fa 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedBuffer.cs
@@ -9,21 +9,21 @@ namespace Avalonia.Media.TextFormatting
     {
         private static readonly IComparer<GlyphInfo> s_clusterComparer = new CompareClusters();
         private bool _bufferRented;
-        
-        public ShapedBuffer(CharacterBufferRange characterBufferRange, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) : 
-            this(characterBufferRange, 
-                new ArraySlice<GlyphInfo>(ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), 0, bufferLength), 
-                glyphTypeface,  
-                fontRenderingEmSize,  
+
+        public ShapedBuffer(ReadOnlyMemory<char> text, int bufferLength, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel) :
+            this(text,
+                new ArraySlice<GlyphInfo>(ArrayPool<GlyphInfo>.Shared.Rent(bufferLength), 0, bufferLength),
+                glyphTypeface,
+                fontRenderingEmSize,
                 bidiLevel)
         {
             _bufferRented = true;
             Length = bufferLength;
         }
 
-        internal ShapedBuffer(CharacterBufferRange characterBufferRange, ArraySlice<GlyphInfo> glyphInfos, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel)
+        internal ShapedBuffer(ReadOnlyMemory<char> text, ArraySlice<GlyphInfo> glyphInfos, IGlyphTypeface glyphTypeface, double fontRenderingEmSize, sbyte bidiLevel)
         {
-            CharacterBufferRange = characterBufferRange;
+            Text = text;
             GlyphInfos = glyphInfos;
             GlyphTypeface = glyphTypeface;
             FontRenderingEmSize = fontRenderingEmSize;
@@ -51,7 +51,7 @@ namespace Avalonia.Media.TextFormatting
 
         public IReadOnlyList<Vector> GlyphOffsets => new GlyphOffsetList(GlyphInfos);
 
-        public CharacterBufferRange CharacterBufferRange { get; }
+        public ReadOnlyMemory<char> Text { get; }
         
         /// <summary>
         /// Finds a glyph index for given character index.
@@ -113,7 +113,7 @@ namespace Avalonia.Media.TextFormatting
         /// <returns>The split result.</returns>
         internal SplitResult<ShapedBuffer> Split(int length)
         {
-            if (CharacterBufferRange.Length == length)
+            if (Text.Length == length)
             {
                 return new SplitResult<ShapedBuffer>(this, null);
             }
@@ -125,10 +125,10 @@ namespace Avalonia.Media.TextFormatting
 
             var glyphCount = FindGlyphIndex(start + length);
 
-            var first = new ShapedBuffer(CharacterBufferRange.Take(length), 
+            var first = new ShapedBuffer(Text.Slice(0, length),
                 GlyphInfos.Take(glyphCount), GlyphTypeface, FontRenderingEmSize, BidiLevel);
 
-            var second = new ShapedBuffer(CharacterBufferRange.Skip(length),
+            var second = new ShapedBuffer(Text.Slice(length),
                 GlyphInfos.Skip(glyphCount), GlyphTypeface, FontRenderingEmSize, BidiLevel);
 
             return new SplitResult<ShapedBuffer>(first, second);
diff --git a/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs b/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
index 665723b284..583f2e49f1 100644
--- a/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/ShapedTextRun.cs
@@ -13,8 +13,6 @@ namespace Avalonia.Media.TextFormatting
         public ShapedTextRun(ShapedBuffer shapedBuffer, TextRunProperties properties)
         {
             ShapedBuffer = shapedBuffer;
-            CharacterBufferReference = shapedBuffer.CharacterBufferRange.CharacterBufferReference;
-            Length = shapedBuffer.CharacterBufferRange.Length;
             Properties = properties;
             TextMetrics = new TextMetrics(properties.Typeface.GlyphTypeface, properties.FontRenderingEmSize);
         }
@@ -26,13 +24,15 @@ namespace Avalonia.Media.TextFormatting
         public ShapedBuffer ShapedBuffer { get; }
 
         /// <inheritdoc/>
-        public override CharacterBufferReference CharacterBufferReference { get; }
+        public override ReadOnlyMemory<char> Text
+            => ShapedBuffer.Text;
 
         /// <inheritdoc/>
         public override TextRunProperties Properties { get; }
 
         /// <inheritdoc/>
-        public override int Length { get; }
+        public override int Length
+            => ShapedBuffer.Text.Length;
 
         public TextMetrics TextMetrics { get; }
 
@@ -113,6 +113,7 @@ namespace Avalonia.Media.TextFormatting
         {
             length = 0;
             var currentWidth = 0.0;
+            var charactersSpan = GlyphRun.Characters.Span;
 
             for (var i = 0; i < ShapedBuffer.Length; i++)
             {
@@ -123,7 +124,7 @@ namespace Avalonia.Media.TextFormatting
                     break;
                 }
 
-                Codepoint.ReadAt(GlyphRun.Characters, length, out var count);
+                Codepoint.ReadAt(charactersSpan, length, out var count);
 
                 length += count;
                 currentWidth += advance;
@@ -136,6 +137,7 @@ namespace Avalonia.Media.TextFormatting
         {
             length = 0;
             width = 0;
+            var charactersSpan = GlyphRun.Characters.Span;
 
             for (var i = ShapedBuffer.Length - 1; i >= 0; i--)
             {
@@ -146,7 +148,7 @@ namespace Avalonia.Media.TextFormatting
                     break;
                 }
 
-                Codepoint.ReadAt(GlyphRun.Characters, length, out var count);
+                Codepoint.ReadAt(charactersSpan, length, out var count);
 
                 length += count;
                 width += advance;
@@ -192,7 +194,7 @@ namespace Avalonia.Media.TextFormatting
             return new GlyphRun(
                 ShapedBuffer.GlyphTypeface,
                 ShapedBuffer.FontRenderingEmSize,
-                new CharacterBufferRange(CharacterBufferReference, Length),
+                Text,
                 ShapedBuffer.GlyphIndices,
                 ShapedBuffer.GlyphAdvances,
                 ShapedBuffer.GlyphOffsets,
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs b/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
index 1a48151834..2525f0dbf9 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextCharacters.cs
@@ -10,82 +10,34 @@ namespace Avalonia.Media.TextFormatting
     public class TextCharacters : TextRun
     {
         /// <summary>
-        /// Construct a run of text content from character array
+        /// Constructs a run for text content from a string.
         /// </summary>
-        public TextCharacters(
-            char[] characterArray,
-            int offsetToFirstChar,
-            int length,
-            TextRunProperties textRunProperties
-            ) :
-            this(
-                new CharacterBufferReference(characterArray, offsetToFirstChar),
-                length,
-                textRunProperties
-                )
-        { }
-
-
-        /// <summary>
-        /// Construct a run for text content from string 
-        /// </summary>
-        public TextCharacters(
-            string characterString,
-            TextRunProperties textRunProperties
-            ) :
-            this(
-                characterString,
-                0,  // offsetToFirstChar
-                (characterString == null) ? 0 : characterString.Length,
-                textRunProperties
-                )
-        { }
-
-        /// <summary>
-        /// Construct a run for text content from string
-        /// </summary>
-        public TextCharacters(
-            string characterString,
-            int offsetToFirstChar,
-            int length,
-            TextRunProperties textRunProperties
-            ) :
-            this(
-                new CharacterBufferReference(characterString, offsetToFirstChar),
-                length,
-                textRunProperties
-                )
-        { }
+        public TextCharacters(string text, TextRunProperties textRunProperties)
+            : this(text.AsMemory(), textRunProperties)
+        {
+        }
 
         /// <summary>
-        /// Internal constructor of TextContent
+        /// Constructs a run for text content from a memory region.
         /// </summary>
-        public TextCharacters(
-            CharacterBufferReference characterBufferReference,
-            int length,
-            TextRunProperties textRunProperties
-            )
+        public TextCharacters(ReadOnlyMemory<char> text, TextRunProperties textRunProperties)
         {
-            if (length <= 0)
-            {
-                throw new ArgumentOutOfRangeException("length", "ParameterMustBeGreaterThanZero");
-            }
-
             if (textRunProperties.FontRenderingEmSize <= 0)
             {
-                throw new ArgumentOutOfRangeException("textRunProperties.FontRenderingEmSize", "ParameterMustBeGreaterThanZero");
+                throw new ArgumentOutOfRangeException(nameof(textRunProperties), textRunProperties.FontRenderingEmSize,
+                    $"Invalid {nameof(TextRunProperties.FontRenderingEmSize)}");
             }
 
-            CharacterBufferReference = characterBufferReference;
-            Length = length;
+            Text = text;
             Properties = textRunProperties;
         }
 
         /// <inheritdoc />
-        public override int Length { get; }
+        public override int Length
+            => Text.Length;
 
         /// <inheritdoc />
-        public override CharacterBufferReference CharacterBufferReference { get; }
+        public override ReadOnlyMemory<char> Text { get; }
 
         /// <inheritdoc />
         public override TextRunProperties Properties { get; }
@@ -94,17 +46,19 @@ namespace Avalonia.Media.TextFormatting
         /// Gets a list of <see cref="UnshapedTextRun"/>.
         /// </summary>
         /// <returns>The shapeable text characters.</returns>
-        internal IReadOnlyList<UnshapedTextRun> GetShapeableCharacters(CharacterBufferRange characterBufferRange, sbyte biDiLevel, ref TextRunProperties? previousProperties)
+        internal IReadOnlyList<UnshapedTextRun> GetShapeableCharacters(ReadOnlyMemory<char> text, sbyte biDiLevel,
+            ref TextRunProperties? previousProperties)
         {
             var shapeableCharacters = new List<UnshapedTextRun>(2);
+            var properties = Properties;
 
-            while (characterBufferRange.Length > 0)
+            while (!text.IsEmpty)
             {
-                var shapeableRun = CreateShapeableRun(characterBufferRange, Properties, biDiLevel, ref previousProperties);
+                var shapeableRun = CreateShapeableRun(text, properties, biDiLevel, ref previousProperties);
 
                 shapeableCharacters.Add(shapeableRun);
 
-                characterBufferRange = characterBufferRange.Skip(shapeableRun.Length);
+                text = text.Slice(shapeableRun.Length);
 
                 previousProperties = shapeableRun.Properties;
             }
@@ -115,45 +69,46 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Creates a shapeable text run with unique properties.
         /// </summary>
-        /// <param name="characterBufferRange">The character buffer range to create text runs from.</param>
+        /// <param name="text">The characters to create text runs from.</param>
         /// <param name="defaultProperties">The default text run properties.</param>
         /// <param name="biDiLevel">The bidi level of the run.</param>
         /// <param name="previousProperties"></param>
         /// <returns>A list of shapeable text runs.</returns>
-        private static UnshapedTextRun CreateShapeableRun(CharacterBufferRange characterBufferRange,
+        private static UnshapedTextRun CreateShapeableRun(ReadOnlyMemory<char> text,
             TextRunProperties defaultProperties, sbyte biDiLevel, ref TextRunProperties? previousProperties)
         {
             var defaultTypeface = defaultProperties.Typeface;
             var currentTypeface = defaultTypeface;
             var previousTypeface = previousProperties?.Typeface;
+            var textSpan = text.Span;
 
-            if (TryGetShapeableLength(characterBufferRange, currentTypeface, null, out var count, out var script))
+            if (TryGetShapeableLength(textSpan, currentTypeface, null, out var count, out var script))
             {
                 if (script == Script.Common && previousTypeface is not null)
                 {
-                    if (TryGetShapeableLength(characterBufferRange, previousTypeface.Value, null, out var fallbackCount, out _))
+                    if (TryGetShapeableLength(textSpan, previousTypeface.Value, null, out var fallbackCount, out _))
                     {
-                        return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, fallbackCount,
+                        return new UnshapedTextRun(text.Slice(0, fallbackCount),
                             defaultProperties.WithTypeface(previousTypeface.Value), biDiLevel);
                     }
                 }
 
-                return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, count, defaultProperties.WithTypeface(currentTypeface),
+                return new UnshapedTextRun(text.Slice(0, count), defaultProperties.WithTypeface(currentTypeface),
                     biDiLevel);
             }
 
             if (previousTypeface is not null)
             {
-                if (TryGetShapeableLength(characterBufferRange, previousTypeface.Value, defaultTypeface, out count, out _))
+                if (TryGetShapeableLength(textSpan, previousTypeface.Value, defaultTypeface, out count, out _))
                 {
-                    return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, count,
+                    return new UnshapedTextRun(text.Slice(0, count),
                         defaultProperties.WithTypeface(previousTypeface.Value), biDiLevel);
                 }
             }
 
             var codepoint = Codepoint.ReplacementCodepoint;
 
-            var codepointEnumerator = new CodepointEnumerator(characterBufferRange.Skip(count));
+            var codepointEnumerator = new CodepointEnumerator(text.Slice(count).Span);
 
             while (codepointEnumerator.MoveNext())
             {
@@ -173,10 +128,10 @@ namespace Avalonia.Media.TextFormatting
                     defaultTypeface.Stretch, defaultTypeface.FontFamily, defaultProperties.CultureInfo,
                     out currentTypeface);
 
-            if (matchFound && TryGetShapeableLength(characterBufferRange, currentTypeface, defaultTypeface, out count, out _))
+            if (matchFound && TryGetShapeableLength(textSpan, currentTypeface, defaultTypeface, out count, out _))
             {
                 //Fallback found
-                return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, count, defaultProperties.WithTypeface(currentTypeface),
+                return new UnshapedTextRun(text.Slice(0, count), defaultProperties.WithTypeface(currentTypeface),
                     biDiLevel);
             }
 
@@ -185,7 +140,7 @@ namespace Avalonia.Media.TextFormatting
 
             var glyphTypeface = currentTypeface.GlyphTypeface;
 
-            var enumerator = new GraphemeEnumerator(characterBufferRange);
+            var enumerator = new GraphemeEnumerator(textSpan);
 
             while (enumerator.MoveNext())
             {
@@ -196,23 +151,23 @@ namespace Avalonia.Media.TextFormatting
                     break;
                 }
 
-                count += grapheme.Length;
+                count += grapheme.Text.Length;
             }
 
-            return new UnshapedTextRun(characterBufferRange.CharacterBufferReference, count, defaultProperties, biDiLevel);
+            return new UnshapedTextRun(text.Slice(0, count), defaultProperties, biDiLevel);
         }
 
         /// <summary>
         /// Tries to get a shapeable length that is supported by the specified typeface.
         /// </summary>
-        /// <param name="characterBufferRange">The character buffer range to shape.</param>
+        /// <param name="text">The characters to shape.</param>
         /// <param name="typeface">The typeface that is used to find matching characters.</param>
         /// <param name="defaultTypeface"></param>
         /// <param name="length">The shapeable length.</param>
         /// <param name="script"></param>
         /// <returns></returns>
         internal static bool TryGetShapeableLength(
-            CharacterBufferRange characterBufferRange,
+            ReadOnlySpan<char> text,
             Typeface typeface,
             Typeface? defaultTypeface,
             out int length,
@@ -221,7 +176,7 @@ namespace Avalonia.Media.TextFormatting
             length = 0;
             script = Script.Unknown;
 
-            if (characterBufferRange.Length == 0)
+            if (text.IsEmpty)
             {
                 return false;
             }
@@ -229,7 +184,7 @@ namespace Avalonia.Media.TextFormatting
             var font = typeface.GlyphTypeface;
             var defaultFont = defaultTypeface?.GlyphTypeface;
 
-            var enumerator = new GraphemeEnumerator(characterBufferRange);
+            var enumerator = new GraphemeEnumerator(text);
 
             while (enumerator.MoveNext())
             {
@@ -264,7 +219,7 @@ namespace Avalonia.Media.TextFormatting
                     }
                 }
 
-                length += currentGrapheme.Length;
+                length += currentGrapheme.Text.Length;
             }
 
             return length > 0;
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs b/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
index 9c201bda22..528cd45581 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextEllipsisHelper.cs
@@ -45,9 +45,7 @@ namespace Avalonia.Media.TextFormatting
                                     {
                                         var currentBreakPosition = 0;
 
-                                        var text = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
-
-                                        var lineBreaker = new LineBreakEnumerator(text);
+                                        var lineBreaker = new LineBreakEnumerator(currentRun.Text.Span);
 
                                         while (currentBreakPosition < measuredLength && lineBreaker.MoveNext())
                                         {
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
index 517372648f..8afecb09e2 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextFormatterImpl.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Utilities;
 
@@ -162,17 +164,13 @@ namespace Avalonia.Media.TextFormatting
 
             foreach (var textRun in textRuns)
             {
-                if (textRun.CharacterBufferReference.CharacterBuffer.Length == 0)
+                if (textRun.Text.IsEmpty)
                 {
-                    var characterBuffer = new CharacterBufferReference(new char[textRun.Length]);
-
-                    biDiData.Append(new CharacterBufferRange(characterBuffer, textRun.Length));
+                    biDiData.Append(new char[textRun.Length]);
                 }
                 else
                 {
-                    var text = new CharacterBufferRange(textRun.CharacterBufferReference, textRun.Length);
-
-                    biDiData.Append(text);
+                    biDiData.Append(textRun.Text.Span);
                 }
             }
 
@@ -198,9 +196,7 @@ namespace Avalonia.Media.TextFormatting
                     case UnshapedTextRun shapeableRun:
                         {
                             var groupedRuns = new List<UnshapedTextRun>(2) { shapeableRun };
-                            var characterBufferReference = currentRun.CharacterBufferReference;
-                            var length = currentRun.Length;
-                            var offsetToFirstCharacter = characterBufferReference.OffsetToFirstChar;
+                            var text = shapeableRun.Text;
 
                             while (index + 1 < processedRuns.Count)
                             {
@@ -209,23 +205,14 @@ namespace Avalonia.Media.TextFormatting
                                     break;
                                 }
 
-                                if (shapeableRun.CanShapeTogether(nextRun))
+                                if (shapeableRun.BidiLevel == nextRun.BidiLevel
+                                    && TryJoinContiguousMemories(text, nextRun.Text, out var joinedText)
+                                    && CanShapeTogether(shapeableRun.Properties, nextRun.Properties))
                                 {
                                     groupedRuns.Add(nextRun);
-
-                                    length += nextRun.Length;
-
-                                    if (offsetToFirstCharacter > nextRun.CharacterBufferReference.OffsetToFirstChar)
-                                    {
-                                        offsetToFirstCharacter = nextRun.CharacterBufferReference.OffsetToFirstChar;
-                                    }
-
-                                    characterBufferReference = new CharacterBufferReference(characterBufferReference.CharacterBuffer, offsetToFirstCharacter);
-
                                     index++;
-
                                     shapeableRun = nextRun;
-
+                                    text = joinedText;
                                     continue;
                                 }
 
@@ -237,7 +224,7 @@ namespace Avalonia.Media.TextFormatting
                                          shapeableRun.BidiLevel, currentRun.Properties.CultureInfo,
                                          paragraphProperties.DefaultIncrementalTab, paragraphProperties.LetterSpacing);
 
-                            shapedRuns.AddRange(ShapeTogether(groupedRuns, characterBufferReference, length, shaperOptions));
+                            shapedRuns.AddRange(ShapeTogether(groupedRuns, text, shaperOptions));
 
                             break;
                         }
@@ -253,12 +240,81 @@ namespace Avalonia.Media.TextFormatting
             return shapedRuns;
         }
 
+        /// <summary>
+        /// Tries to join two potnetially contiguous memory regions.
+        /// </summary>
+        /// <param name="x">The first memory region.</param>
+        /// <param name="y">The second memory region.</param>
+        /// <param name="joinedMemory">On success, a memory region representing the union of the two regions.</param>
+        /// <returns>true if the two regions were contigous; false otherwise.</returns>
+        private static bool TryJoinContiguousMemories(ReadOnlyMemory<char> x, ReadOnlyMemory<char> y,
+            out ReadOnlyMemory<char> joinedMemory)
+        {
+            if (MemoryMarshal.TryGetString(x, out var xString, out var xStart, out var xLength))
+            {
+                if (MemoryMarshal.TryGetString(y, out var yString, out var yStart, out var yLength)
+                    && ReferenceEquals(xString, yString)
+                    && TryGetContiguousStart(xStart, xLength, yStart, yLength, out var joinedStart))
+                {
+                    joinedMemory = xString.AsMemory(joinedStart, xLength + yLength);
+                    return true;
+                }
+            }
+
+            else if (MemoryMarshal.TryGetArray(x, out var xSegment))
+            {
+                if (MemoryMarshal.TryGetArray(y, out var ySegment)
+                    && ReferenceEquals(xSegment.Array, ySegment.Array)
+                    && TryGetContiguousStart(xSegment.Offset, xSegment.Count, ySegment.Offset, ySegment.Count, out var joinedStart))
+                {
+                    joinedMemory = xSegment.Array.AsMemory(joinedStart, xSegment.Count + ySegment.Count);
+                    return true;
+                }
+            }
+
+            else if (MemoryMarshal.TryGetMemoryManager(x, out MemoryManager<char>? xManager, out xStart, out xLength))
+            {
+                if (MemoryMarshal.TryGetMemoryManager(y, out MemoryManager<char>? yManager, out var yStart, out var yLength)
+                    && ReferenceEquals(xManager, yManager)
+                    && TryGetContiguousStart(xStart, xLength, yStart, yLength, out var joinedStart))
+                {
+                    joinedMemory = xManager.Memory.Slice(joinedStart, xLength + yLength);
+                    return true;
+                }
+            }
+
+            joinedMemory = default;
+            return false;
+
+            static bool TryGetContiguousStart(int xStart, int xLength, int yStart, int yLength, out int joinedStart)
+            {
+                var xRange = (Start: xStart, Length: xLength);
+                var yRange = (Start: yStart, Length: yLength);
+
+                var (firstRange, secondRange) = xStart <= yStart ? (xRange, yRange) : (yRange, xRange);
+                if (firstRange.Start + firstRange.Length == secondRange.Start)
+                {
+                    joinedStart = firstRange.Start;
+                    return true;
+                }
+
+                joinedStart = default;
+                return false;
+            }
+        }
+
+
+        private static bool CanShapeTogether(TextRunProperties x, TextRunProperties y)
+            => MathUtilities.AreClose(x.FontRenderingEmSize, y.FontRenderingEmSize)
+               && x.Typeface == y.Typeface
+               && x.BaselineAlignment == y.BaselineAlignment;
+
         private static IReadOnlyList<ShapedTextRun> ShapeTogether(
-            IReadOnlyList<UnshapedTextRun> textRuns, CharacterBufferReference text, int length, TextShaperOptions options)
+            IReadOnlyList<UnshapedTextRun> textRuns, ReadOnlyMemory<char> text, TextShaperOptions options)
         {
             var shapedRuns = new List<ShapedTextRun>(textRuns.Count);
 
-            var shapedBuffer = TextShaper.Current.ShapeText(text, length, options);
+            var shapedBuffer = TextShaper.Current.ShapeText(text, options);
 
             for (var i = 0; i < textRuns.Count; i++)
             {
@@ -294,7 +350,7 @@ namespace Avalonia.Media.TextFormatting
 
             TextRunProperties? previousProperties = null;
             TextCharacters? currentRun = null;
-            CharacterBufferRange runText = default;
+            ReadOnlyMemory<char> runText = default;
 
             for (var i = 0; i < textCharacters.Count; i++)
             {
@@ -312,11 +368,12 @@ namespace Avalonia.Media.TextFormatting
                     continue;
                 }
 
-                runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
+                runText = currentRun.Text;
+                var runTextSpan = runText.Span;
 
-                for (; j < runText.Length;)
+                for (; j < runTextSpan.Length;)
                 {
-                    Codepoint.ReadAt(runText, j, out var count);
+                    Codepoint.ReadAt(runTextSpan, j, out var count);
 
                     if (levelIndex + 1 == levels.Length)
                     {
@@ -326,9 +383,9 @@ namespace Avalonia.Media.TextFormatting
                     levelIndex++;
                     j += count;
 
-                    if (j == runText.Length)
+                    if (j == runTextSpan.Length)
                     {
-                        processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties));
+                        processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Slice(0, j), runLevel, ref previousProperties));
 
                         runLevel = levels[levelIndex];
 
@@ -341,9 +398,10 @@ namespace Avalonia.Media.TextFormatting
                     }
 
                     // End of this run
-                    processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Take(j), runLevel, ref previousProperties));
+                    processedRuns.AddRange(currentRun.GetShapeableCharacters(runText.Slice(0, j), runLevel, ref previousProperties));
 
-                    runText = runText.Skip(j);
+                    runText = runText.Slice(j);
+                    runTextSpan = runText.Span;
 
                     j = 0;
 
@@ -411,7 +469,7 @@ namespace Avalonia.Media.TextFormatting
                         {
                             if (TryGetLineBreak(textCharacters, out var runLineBreak))
                             {
-                                var splitResult = new TextCharacters(textCharacters.CharacterBufferReference, runLineBreak.PositionWrap,
+                                var splitResult = new TextCharacters(textCharacters.Text.Slice(0, runLineBreak.PositionWrap),
                                     textCharacters.Properties);
 
                                 textRuns.Add(splitResult);
@@ -442,14 +500,14 @@ namespace Avalonia.Media.TextFormatting
         {
             lineBreak = default;
 
-            if (textRun.CharacterBufferReference.CharacterBuffer.IsEmpty)
+            var text = textRun.Text;
+
+            if (text.IsEmpty)
             {
                 return false;
             }
 
-            var characterBufferRange = new CharacterBufferRange(textRun.CharacterBufferReference, textRun.Length);
-
-            var lineBreakEnumerator = new LineBreakEnumerator(characterBufferRange);
+            var lineBreakEnumerator = new LineBreakEnumerator(text.Span);
 
             while (lineBreakEnumerator.MoveNext())
             {
@@ -541,8 +599,7 @@ namespace Avalonia.Media.TextFormatting
             var glyph = glyphTypeface.GetGlyph(s_empty[0]);
             var glyphInfos = new[] { new GlyphInfo(glyph, firstTextSourceIndex) };
 
-            var characterBufferRange = new CharacterBufferRange(new CharacterBufferReference(s_empty), s_empty.Length);
-            var shapedBuffer = new ShapedBuffer(characterBufferRange, glyphInfos, glyphTypeface, properties.FontRenderingEmSize,
+            var shapedBuffer = new ShapedBuffer(s_empty.AsMemory(), glyphInfos, glyphTypeface, properties.FontRenderingEmSize,
                 (sbyte)flowDirection);
 
             var textRuns = new List<DrawableTextRun> { new ShapedTextRun(shapedBuffer, properties) };
@@ -589,10 +646,8 @@ namespace Avalonia.Media.TextFormatting
                 switch (currentRun)
                 {
                     case ShapedTextRun:
-                        {
-                            var runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
-
-                            var lineBreaker = new LineBreakEnumerator(runText);
+                    {
+                            var lineBreaker = new LineBreakEnumerator(currentRun.Text.Span);
 
                             while (lineBreaker.MoveNext())
                             {
@@ -651,9 +706,7 @@ namespace Avalonia.Media.TextFormatting
 
                                                 currentRun = textRuns[index];
 
-                                                runText = new CharacterBufferRange(currentRun.CharacterBufferReference, currentRun.Length);
-
-                                                lineBreaker = new LineBreakEnumerator(runText);
+                                                lineBreaker = new LineBreakEnumerator(currentRun.Text.Span);
                                             }
                                         }
                                         else
@@ -771,9 +824,7 @@ namespace Avalonia.Media.TextFormatting
 
             var shaperOptions = new TextShaperOptions(glyphTypeface, fontRenderingEmSize, (sbyte)flowDirection, cultureInfo);
 
-            var characterBuffer = textRun.CharacterBufferReference;
-
-            var shapedBuffer = textShaper.ShapeText(characterBuffer, textRun.Length, shaperOptions);
+            var shapedBuffer = textShaper.ShapeText(textRun.Text, shaperOptions);
 
             return new ShapedTextRun(shapedBuffer, textRun.Properties);
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
index 56232ec9c8..da343676bb 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextRun.cs
@@ -1,4 +1,5 @@
-using System.Diagnostics;
+using System;
+using System.Diagnostics;
 
 namespace Avalonia.Media.TextFormatting
 {
@@ -18,7 +19,7 @@ namespace Avalonia.Media.TextFormatting
         /// <summary>
         /// Gets the text run's text.
         /// </summary>
-        public virtual CharacterBufferReference CharacterBufferReference => default;
+        public virtual ReadOnlyMemory<char> Text => default;
 
         /// <summary>
         /// A set of properties shared by every characters in the run
@@ -34,21 +35,7 @@ namespace Avalonia.Media.TextFormatting
                 _textRun = textRun;
             }
 
-            public string Text
-            {
-                get
-                {
-                    unsafe
-                    {
-                        var characterBuffer = new CharacterBufferRange(_textRun.CharacterBufferReference, _textRun.Length);
-
-                        fixed (char* charsPtr = characterBuffer.Span)
-                        {
-                            return new string(charsPtr, 0, _textRun.Length);
-                        }
-                    }
-                }
-            }
+            public string Text => _textRun.Text.ToString();
 
             public TextRunProperties? Properties => _textRun.Properties;
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs b/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
index c161b08d20..ae2a827944 100644
--- a/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/TextShaper.cs
@@ -40,14 +40,14 @@ namespace Avalonia.Media.TextFormatting
         }
 
         /// <inheritdoc cref="ITextShaperImpl.ShapeText"/>
-        public ShapedBuffer ShapeText(CharacterBufferReference text, int length, TextShaperOptions options = default)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options = default)
         {
-            return _platformImpl.ShapeText(text, length, options);
+            return _platformImpl.ShapeText(text, options);
         }
 
         public ShapedBuffer ShapeText(string text, TextShaperOptions options = default)
         {
-            return ShapeText(new CharacterBufferReference(text), text.Length, options);
+            return ShapeText(text.AsMemory(), options);
         }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
index 644f7e9a8a..0f0b3235e1 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/BiDiData.cs
@@ -64,7 +64,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// Appends text to the bidi data.
         /// </summary>
         /// <param name="text">The text to process.</param>
-        public void Append(CharacterBufferRange text)
+        public void Append(ReadOnlySpan<char> text)
         {
             _classes.Add(text.Length);
             _pairedBracketTypes.Add(text.Length);
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
index 8b9d1c1d02..22f7b50fd4 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/Codepoint.cs
@@ -166,72 +166,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         /// <param name="index">The index to read at.</param>
         /// <param name="count">The count of character that were read.</param>
         /// <returns></returns>
-        public static Codepoint ReadAt(IReadOnlyList<char> text, int index, out int count)
-        {
-            count = 1;
-
-            if (index >= text.Count)
-            {
-                return ReplacementCodepoint;
-            }
-
-            var code = text[index];
-
-            ushort hi, low;
-
-            //# High surrogate
-            if (0xD800 <= code && code <= 0xDBFF)
-            {
-                hi = code;
-
-                if (index + 1 == text.Count)
-                {
-                    return ReplacementCodepoint;
-                }
-
-                low = text[index + 1];
-
-                if (0xDC00 <= low && low <= 0xDFFF)
-                {
-                    count = 2;
-                    return new Codepoint((uint)((hi - 0xD800) * 0x400 + (low - 0xDC00) + 0x10000));
-                }
-
-                return ReplacementCodepoint;
-            }
-
-            //# Low surrogate
-            if (0xDC00 <= code && code <= 0xDFFF)
-            {
-                if (index == 0)
-                {
-                    return ReplacementCodepoint;
-                }
-
-                hi = text[index - 1];
-
-                low = code;
-
-                if (0xD800 <= hi && hi <= 0xDBFF)
-                {
-                    count = 2;
-                    return new Codepoint((uint)((hi - 0xD800) * 0x400 + (low - 0xDC00) + 0x10000));
-                }
-
-                return ReplacementCodepoint;
-            }
-
-            return new Codepoint(code);
-        }
-        
-        /// <summary>
-        /// Reads the <see cref="Codepoint"/> at specified position.
-        /// </summary>
-        /// <param name="text">The buffer to read from.</param>
-        /// <param name="index">The index to read at.</param>
-        /// <param name="count">The count of character that were read.</param>
-        /// <returns></returns>
-        public static Codepoint ReadAt(CharacterBufferRange text, int index, out int count)
+        public static Codepoint ReadAt(ReadOnlySpan<char> text, int index, out int count)
         {
             count = 1;
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
index a2c36d9a13..d21f30ab7e 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/CodepointEnumerator.cs
@@ -4,9 +4,9 @@ namespace Avalonia.Media.TextFormatting.Unicode
 {
     public ref struct CodepointEnumerator
     {
-        private CharacterBufferRange _text;
+        private ReadOnlySpan<char> _text;
 
-        public CodepointEnumerator(CharacterBufferRange text)
+        public CodepointEnumerator(ReadOnlySpan<char> text)
         {
             _text = text;
             Current = Codepoint.ReplacementCodepoint;
@@ -32,7 +32,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             Current = Codepoint.ReadAt(_text, 0, out var count);
 
-            _text = _text.Skip(count);
+            _text = _text.Slice(count);
 
             return true;
         }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
index f75168083c..fa8e8ac976 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/Grapheme.cs
@@ -7,11 +7,10 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// </summary>
     public readonly ref struct Grapheme
     {
-        public Grapheme(Codepoint firstCodepoint, int offset, int length)
+        public Grapheme(Codepoint firstCodepoint, ReadOnlySpan<char> text)
         {
             FirstCodepoint = firstCodepoint;
-            Offset = offset;
-            Length = length;
+            Text = text;
         }
 
         /// <summary>
@@ -20,13 +19,8 @@ namespace Avalonia.Media.TextFormatting.Unicode
         public Codepoint FirstCodepoint { get; }
 
         /// <summary>
-        /// The Offset to the FirstCodepoint
+        /// The text of the grapheme cluster
         /// </summary>
-        public int Offset { get; }
-
-        /// <summary>
-        /// The length of the grapheme cluster
-        /// </summary>
-        public int Length { get; }
+        public ReadOnlySpan<char> Text { get; }
     }
 }
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
index dc21e06813..812bb99d99 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/GraphemeEnumerator.cs
@@ -3,16 +3,16 @@
 // 
 // Licensed to The Avalonia Project under MIT License, courtesy of The .NET Foundation.
 
-using System.Collections.Generic;
+using System;
 using System.Runtime.InteropServices;
 
 namespace Avalonia.Media.TextFormatting.Unicode
 {
     public ref struct GraphemeEnumerator
     {
-        private CharacterBufferRange _text;
+        private ReadOnlySpan<char> _text;
 
-        public GraphemeEnumerator(CharacterBufferRange text)
+        public GraphemeEnumerator(ReadOnlySpan<char> text)
         {
             _text = text;
             Current = default;
@@ -185,9 +185,9 @@ namespace Avalonia.Media.TextFormatting.Unicode
 
             Return:
 
-            Current = new Grapheme(firstCodepoint, _text.OffsetToFirstChar, processor.CurrentCodeUnitOffset);
+            Current = new Grapheme(firstCodepoint, _text.Slice(0, processor.CurrentCodeUnitOffset));
 
-            _text = _text.Skip(processor.CurrentCodeUnitOffset);
+            _text = _text.Slice(processor.CurrentCodeUnitOffset);
 
             return true; // rules GB2, GB999
         }
@@ -195,10 +195,10 @@ namespace Avalonia.Media.TextFormatting.Unicode
         [StructLayout(LayoutKind.Auto)]
         private ref struct Processor
         {
-            private readonly CharacterBufferRange _buffer;
+            private readonly ReadOnlySpan<char> _buffer;
             private int _codeUnitLengthOfCurrentScalar;
 
-            internal Processor(CharacterBufferRange buffer)
+            internal Processor(ReadOnlySpan<char> buffer)
             {
                 _buffer = buffer;
                 _codeUnitLengthOfCurrentScalar = 0;
diff --git a/src/Avalonia.Base/Media/TextFormatting/Unicode/LineBreakEnumerator.cs b/src/Avalonia.Base/Media/TextFormatting/Unicode/LineBreakEnumerator.cs
index 41a476c17e..877ab76ce5 100644
--- a/src/Avalonia.Base/Media/TextFormatting/Unicode/LineBreakEnumerator.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/Unicode/LineBreakEnumerator.cs
@@ -3,7 +3,6 @@
 // Ported from: https://github.com/SixLabors/Fonts/
 
 using System;
-using System.Collections.Generic;
 
 namespace Avalonia.Media.TextFormatting.Unicode
 {
@@ -13,7 +12,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
     /// </summary>
     public ref struct LineBreakEnumerator
     {
-        private readonly IReadOnlyList<char> _text;
+        private readonly ReadOnlySpan<char> _text;
         private int _position;
         private int _lastPosition;
         private LineBreakClass _currentClass;
@@ -29,7 +28,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
         private int _lb30a;
         private bool _lb31;
 
-        public LineBreakEnumerator(IReadOnlyList<char> text)
+        public LineBreakEnumerator(ReadOnlySpan<char> text)
             : this()
         {
             _text = text;
@@ -63,7 +62,7 @@ namespace Avalonia.Media.TextFormatting.Unicode
                 _lb30a = 0;
             }
 
-            while (_position < _text.Count)
+            while (_position < _text.Length)
             {
                 _lastPosition = _position;
                 var lastClass = _nextClass;
@@ -93,11 +92,11 @@ namespace Avalonia.Media.TextFormatting.Unicode
                 }
             }
 
-            if (_position >= _text.Count)
+            if (_position >= _text.Length)
             {
-                if (_lastPosition < _text.Count)
+                if (_lastPosition < _text.Length)
                 {
-                    _lastPosition = _text.Count;
+                    _lastPosition = _text.Length;
 
                     var required = false;
 
diff --git a/src/Avalonia.Base/Media/TextFormatting/UnshapedTextRun.cs b/src/Avalonia.Base/Media/TextFormatting/UnshapedTextRun.cs
index 817086db88..5582ab4787 100644
--- a/src/Avalonia.Base/Media/TextFormatting/UnshapedTextRun.cs
+++ b/src/Avalonia.Base/Media/TextFormatting/UnshapedTextRun.cs
@@ -1,4 +1,4 @@
-using Avalonia.Utilities;
+using System;
 
 namespace Avalonia.Media.TextFormatting
 {
@@ -7,52 +7,20 @@ namespace Avalonia.Media.TextFormatting
     /// </summary>
     public sealed class UnshapedTextRun : TextRun
     {
-        public UnshapedTextRun(CharacterBufferReference characterBufferReference, int length,
-            TextRunProperties properties, sbyte biDiLevel)
+        public UnshapedTextRun(ReadOnlyMemory<char> text, TextRunProperties properties, sbyte biDiLevel)
         {
-            CharacterBufferReference = characterBufferReference;
-            Length = length;
+            Text = text;
             Properties = properties;
             BidiLevel = biDiLevel;
         }
 
-        public override int Length { get; }
+        public override int Length
+            => Text.Length;
 
-        public override CharacterBufferReference CharacterBufferReference { get; }
+        public override ReadOnlyMemory<char> Text { get; }
 
         public override TextRunProperties Properties { get; }
 
         public sbyte BidiLevel { get; }
-
-        public bool CanShapeTogether(UnshapedTextRun unshapedTextRun)
-        {
-            if (!CharacterBufferReference.Equals(unshapedTextRun.CharacterBufferReference))
-            {
-                return false;
-            }
-
-            if (BidiLevel != unshapedTextRun.BidiLevel)
-            {
-                return false;
-            }
-
-            if (!MathUtilities.AreClose(Properties.FontRenderingEmSize,
-                    unshapedTextRun.Properties.FontRenderingEmSize))
-            {
-                return false;
-            }
-
-            if (Properties.Typeface != unshapedTextRun.Properties.Typeface)
-            {
-                return false;
-            }
-
-            if (Properties.BaselineAlignment != unshapedTextRun.Properties.BaselineAlignment)
-            {
-                return false;
-            }
-
-            return true;
-        }
     }
 }
diff --git a/src/Avalonia.Base/Platform/ITextShaperImpl.cs b/src/Avalonia.Base/Platform/ITextShaperImpl.cs
index c3eb89ab1a..a651b49e64 100644
--- a/src/Avalonia.Base/Platform/ITextShaperImpl.cs
+++ b/src/Avalonia.Base/Platform/ITextShaperImpl.cs
@@ -1,4 +1,5 @@
-using Avalonia.Media.TextFormatting;
+using System;
+using Avalonia.Media.TextFormatting;
 using Avalonia.Metadata;
 
 namespace Avalonia.Platform
@@ -13,9 +14,8 @@ namespace Avalonia.Platform
         /// Shapes the specified region within the text and returns a shaped buffer.
         /// </summary>
         /// <param name="text">The text buffer.</param>
-        /// <param name="length">The length of text.</param>
         /// <param name="options">Text shaper options to customize the shaping process.</param>
         /// <returns>A shaped glyph run.</returns>
-        ShapedBuffer ShapeText(CharacterBufferReference text, int length, TextShaperOptions options);
+        ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options);
     }   
 }
diff --git a/src/Avalonia.Controls/TextBlock.cs b/src/Avalonia.Controls/TextBlock.cs
index 31ddf1f985..9bd1dc95f9 100644
--- a/src/Avalonia.Controls/TextBlock.cs
+++ b/src/Avalonia.Controls/TextBlock.cs
@@ -826,12 +826,12 @@ namespace Avalonia.Controls
 
         protected readonly record struct SimpleTextSource : ITextSource
         {
-            private readonly CharacterBufferRange _text;
+            private readonly string _text;
             private readonly TextRunProperties _defaultProperties;
 
             public SimpleTextSource(string text, TextRunProperties defaultProperties)
             {
-                _text = new CharacterBufferRange(new CharacterBufferReference(text), text.Length);
+                _text = text;
                 _defaultProperties = defaultProperties;
             }
 
@@ -842,14 +842,14 @@ namespace Avalonia.Controls
                     return new TextEndOfParagraph();
                 }
 
-                var runText = _text.Skip(textSourceIndex);
+                var runText = _text.AsMemory(textSourceIndex);
 
                 if (runText.IsEmpty)
                 {
                     return new TextEndOfParagraph();
                 }
 
-                return new TextCharacters(runText.CharacterBufferReference, runText.Length, _defaultProperties);
+                return new TextCharacters(runText, _defaultProperties);
             }
         }
 
@@ -884,14 +884,9 @@ namespace Avalonia.Controls
 
                     if (textRun is TextCharacters)                 
                     {
-                        var characterBufferReference = textRun.CharacterBufferReference;
-
                         var skip = Math.Max(0, textSourceIndex - currentPosition);
 
-                        return new TextCharacters(
-                            new CharacterBufferReference(characterBufferReference.CharacterBuffer, characterBufferReference.OffsetToFirstChar + skip), 
-                            textRun.Length - skip,
-                            textRun.Properties!);
+                        return new TextCharacters(textRun.Text.Slice(skip), textRun.Properties!);
                     }
 
                     return textRun;
diff --git a/src/Avalonia.Controls/TextBox.cs b/src/Avalonia.Controls/TextBox.cs
index f388dc871e..9d07fb024a 100644
--- a/src/Avalonia.Controls/TextBox.cs
+++ b/src/Avalonia.Controls/TextBox.cs
@@ -961,9 +961,7 @@ namespace Avalonia.Controls
 
                 var length = 0;
 
-                var inputRange = new CharacterBufferRange(new CharacterBufferReference(input), input.Length);
-
-                var graphemeEnumerator = new GraphemeEnumerator(inputRange);
+                var graphemeEnumerator = new GraphemeEnumerator(input.AsSpan());
 
                 while (graphemeEnumerator.MoveNext())
                 {
@@ -981,7 +979,7 @@ namespace Avalonia.Controls
                         }
                     }
 
-                    length += grapheme.Length;
+                    length += grapheme.Text.Length;
                 }
 
                 if (length < input.Length)
diff --git a/src/Avalonia.Controls/TextBoxTextInputMethodClient.cs b/src/Avalonia.Controls/TextBoxTextInputMethodClient.cs
index 52815b943d..c1146cceda 100644
--- a/src/Avalonia.Controls/TextBoxTextInputMethodClient.cs
+++ b/src/Avalonia.Controls/TextBoxTextInputMethodClient.cs
@@ -79,12 +79,10 @@ namespace Avalonia.Controls
             {
                 if(run.Length > 0)
                 {
-                    var characterBufferRange = new CharacterBufferRange(run.CharacterBufferReference, run.Length);
-
 #if NET6_0
-                    builder.Append(characterBufferRange.Span);
+                    builder.Append(run.Text.Span);
 #else
-                    builder.Append(characterBufferRange.Span.ToArray());
+                    builder.Append(run.Text.Span.ToArray());
 #endif
                 }
             }
diff --git a/src/Avalonia.Headless/HeadlessPlatformStubs.cs b/src/Avalonia.Headless/HeadlessPlatformStubs.cs
index 1cc0fa73bb..2a04e624cb 100644
--- a/src/Avalonia.Headless/HeadlessPlatformStubs.cs
+++ b/src/Avalonia.Headless/HeadlessPlatformStubs.cs
@@ -145,15 +145,13 @@ namespace Avalonia.Headless
 
     class HeadlessTextShaperStub : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(CharacterBufferReference text, int length, TextShaperOptions options)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options)
         {
             var typeface = options.Typeface;
             var fontRenderingEmSize = options.FontRenderingEmSize;
             var bidiLevel = options.BidiLevel;
 
-            var characterBufferRange = new CharacterBufferRange(text, length);
-
-            return new ShapedBuffer(characterBufferRange, length, typeface, fontRenderingEmSize, bidiLevel);
+            return new ShapedBuffer(text, text.Length, typeface, fontRenderingEmSize, bidiLevel);
         }
     }
 
diff --git a/src/Skia/Avalonia.Skia/TextShaperImpl.cs b/src/Skia/Avalonia.Skia/TextShaperImpl.cs
index 98eb35d5c5..e0f95bac60 100644
--- a/src/Skia/Avalonia.Skia/TextShaperImpl.cs
+++ b/src/Skia/Avalonia.Skia/TextShaperImpl.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Globalization;
+using System.Runtime.InteropServices;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Platform;
@@ -11,9 +13,9 @@ namespace Avalonia.Skia
 {
     internal class TextShaperImpl : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(CharacterBufferReference characterBufferReference, int length, TextShaperOptions options)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options)
         {
-            var text = new CharacterBufferRange(characterBufferReference, length);
+            var textSpan = text.Span;
             var typeface = options.Typeface;
             var fontRenderingEmSize = options.FontRenderingEmSize;
             var bidiLevel = options.BidiLevel;
@@ -21,7 +23,9 @@ namespace Avalonia.Skia
 
             using (var buffer = new Buffer())
             {
-                buffer.AddUtf16(characterBufferReference.CharacterBuffer.Span, characterBufferReference.OffsetToFirstChar, length);
+                // HarfBuzz needs the surrounding characters to correctly shape the text
+                var containingText = GetContainingMemory(text, out var start, out var length);
+                buffer.AddUtf16(containingText.Span, start, length);
 
                 MergeBreakPair(buffer);
 
@@ -64,7 +68,7 @@ namespace Avalonia.Skia
 
                     var glyphOffset = GetGlyphOffset(glyphPositions, i, textScale);
 
-                    if (text[i] == '\t')
+                    if (textSpan[i] == '\t')
                     {
                         glyphIndex = typeface.GetGlyph(' ');
 
@@ -147,5 +151,26 @@ namespace Avalonia.Skia
             // glyphPositions[index].YAdvance * textScale;
             return glyphPositions[index].XAdvance * textScale;
         }
+
+        private static ReadOnlyMemory<char> GetContainingMemory(ReadOnlyMemory<char> memory, out int start, out int length)
+        {
+            if (MemoryMarshal.TryGetString(memory, out var containingString, out start, out length))
+            {
+                return containingString.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetArray(memory, out var segment))
+            {
+                return segment.Array.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetMemoryManager(memory, out MemoryManager<char> memoryManager, out start, out length))
+            {
+                return memoryManager.Memory;
+            }
+
+            // should never happen
+            throw new InvalidOperationException("Memory not backed by string, array or manager");
+        }
     }
 }
diff --git a/src/Windows/Avalonia.Direct2D1/Media/TextShaperImpl.cs b/src/Windows/Avalonia.Direct2D1/Media/TextShaperImpl.cs
index 6685dd00b9..fffa5ce490 100644
--- a/src/Windows/Avalonia.Direct2D1/Media/TextShaperImpl.cs
+++ b/src/Windows/Avalonia.Direct2D1/Media/TextShaperImpl.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Globalization;
+using System.Runtime.InteropServices;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Platform;
@@ -11,8 +13,9 @@ namespace Avalonia.Direct2D1.Media
 {
     internal class TextShaperImpl : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(CharacterBufferReference characterBufferReference, int length, TextShaperOptions options)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options)
         {
+            var textSpan = text.Span;
             var typeface = options.Typeface;
             var fontRenderingEmSize = options.FontRenderingEmSize;
             var bidiLevel = options.BidiLevel;
@@ -20,7 +23,9 @@ namespace Avalonia.Direct2D1.Media
 
             using (var buffer = new Buffer())
             {
-                buffer.AddUtf16(characterBufferReference.CharacterBuffer.Span, characterBufferReference.OffsetToFirstChar, length);
+                // HarfBuzz needs the surrounding characters to correctly shape the text
+                var containingText = GetContainingMemory(text, out var start, out var length);
+                buffer.AddUtf16(containingText.Span, start, length);
 
                 MergeBreakPair(buffer);
 
@@ -34,7 +39,7 @@ namespace Avalonia.Direct2D1.Media
 
                 font.Shape(buffer);
 
-                if(buffer.Direction == Direction.RightToLeft)
+                if (buffer.Direction == Direction.RightToLeft)
                 {
                     buffer.Reverse();
                 }
@@ -45,9 +50,7 @@ namespace Avalonia.Direct2D1.Media
 
                 var bufferLength = buffer.Length;
 
-                var characterBufferRange = new CharacterBufferRange(characterBufferReference, length);
-
-                var shapedBuffer = new ShapedBuffer(characterBufferRange, bufferLength, typeface, fontRenderingEmSize, bidiLevel);
+                var shapedBuffer = new ShapedBuffer(text, bufferLength, typeface, fontRenderingEmSize, bidiLevel);
 
                 var glyphInfos = buffer.GetGlyphInfoSpan();
 
@@ -61,11 +64,11 @@ namespace Avalonia.Direct2D1.Media
 
                     var glyphCluster = (int)(sourceInfo.Cluster);
 
-                    var glyphAdvance = GetGlyphAdvance(glyphPositions, i, textScale);
+                    var glyphAdvance = GetGlyphAdvance(glyphPositions, i, textScale) + options.LetterSpacing;
 
                     var glyphOffset = GetGlyphOffset(glyphPositions, i, textScale);
 
-                    if (characterBufferRange[i] == '\t')
+                    if (textSpan[i] == '\t')
                     {
                         glyphIndex = typeface.GetGlyph(' ');
 
@@ -148,5 +151,26 @@ namespace Avalonia.Direct2D1.Media
             // glyphPositions[index].YAdvance * textScale;
             return glyphPositions[index].XAdvance * textScale;
         }
+
+        private static ReadOnlyMemory<char> GetContainingMemory(ReadOnlyMemory<char> memory, out int start, out int length)
+        {
+            if (MemoryMarshal.TryGetString(memory, out var containingString, out start, out length))
+            {
+                return containingString.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetArray(memory, out var segment))
+            {
+                return segment.Array.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetMemoryManager(memory, out MemoryManager<char> memoryManager, out start, out length))
+            {
+                return memoryManager.Memory;
+            }
+
+            // should never happen
+            throw new InvalidOperationException("Memory not backed by string, array or manager");
+        }
     }
 }
diff --git a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/BiDiClassTests.cs b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/BiDiClassTests.cs
index b2c40f4ff1..9d189d1950 100644
--- a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/BiDiClassTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/BiDiClassTests.cs
@@ -37,7 +37,7 @@ namespace Avalonia.Visuals.UnitTests.Media.TextFormatting
             var text = Encoding.UTF32.GetString(MemoryMarshal.Cast<int, byte>(t.CodePoints).ToArray());
 
             // Append
-            bidiData.Append(new CharacterBufferRange(text));
+            bidiData.Append(text);
 
             // Act
             for (int i = 0; i < 10; i++)
diff --git a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
index c57bd6c002..a022039000 100644
--- a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/GraphemeBreakClassTrieGeneratorTests.cs
@@ -38,18 +38,13 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
             var text = Encoding.UTF32.GetString(MemoryMarshal.Cast<int, byte>(t.Codepoints).ToArray());
             var grapheme = Encoding.UTF32.GetString(MemoryMarshal.Cast<int, byte>(t.Grapheme).ToArray()).AsSpan();
 
-            var enumerator = new GraphemeEnumerator(new CharacterBufferRange(text));
+            var enumerator = new GraphemeEnumerator(text);
 
             enumerator.MoveNext();
 
-            var actual = text.AsSpan(enumerator.Current.Offset, enumerator.Current.Length);
+            var actual = enumerator.Current.Text;
 
-            var pass = true;
-
-            if(actual.Length != grapheme.Length)
-            {
-                pass = false;
-            }
+            bool pass = actual.Length == grapheme.Length;
 
             if (pass)
             {
@@ -87,13 +82,13 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
         {
             const string text = "ABCDEFGHIJ";
 
-            var enumerator = new GraphemeEnumerator(new CharacterBufferRange(text));
+            var enumerator = new GraphemeEnumerator(text);
 
             var count = 0;
 
             while (enumerator.MoveNext())
             {
-                Assert.Equal(1, enumerator.Current.Length);
+                Assert.Equal(1, enumerator.Current.Text.Length);
 
                 count++;
             }
diff --git a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/LineBreakEnumuratorTests.cs b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/LineBreakEnumuratorTests.cs
index b2648bf348..d198fe81a6 100644
--- a/tests/Avalonia.Base.UnitTests/Media/TextFormatting/LineBreakEnumuratorTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Media/TextFormatting/LineBreakEnumuratorTests.cs
@@ -23,7 +23,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
         [Fact]
         public void BasicLatinTest()
         {
-            var lineBreaker = new LineBreakEnumerator(new CharacterBufferRange("Hello World\r\nThis is a test."));
+            var lineBreaker = new LineBreakEnumerator("Hello World\r\nThis is a test.");
 
             Assert.True(lineBreaker.MoveNext());
             Assert.Equal(6, lineBreaker.Current.PositionWrap);
@@ -56,7 +56,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
         [Fact]
         public void ForwardTextWithOuterWhitespace()
         {
-            var lineBreaker = new LineBreakEnumerator(new CharacterBufferRange(" Apples Pears Bananas   "));
+            var lineBreaker = new LineBreakEnumerator(" Apples Pears Bananas   ");
             var positionsF = GetBreaks(lineBreaker);
             Assert.Equal(1, positionsF[0].PositionWrap);
             Assert.Equal(0, positionsF[0].PositionMeasure);
@@ -83,7 +83,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
         [Fact]
         public void ForwardTest()
         {
-            var lineBreaker = new LineBreakEnumerator(new CharacterBufferRange("Apples Pears Bananas"));
+            var lineBreaker = new LineBreakEnumerator("Apples Pears Bananas");
 
             var positionsF = GetBreaks(lineBreaker);
             Assert.Equal(7, positionsF[0].PositionWrap);
@@ -100,7 +100,7 @@ namespace Avalonia.Base.UnitTests.Media.TextFormatting
         {
             var text = string.Join(null, codePoints.Select(char.ConvertFromUtf32));
 
-            var lineBreaker = new LineBreakEnumerator(new CharacterBufferRange(text));
+            var lineBreaker = new LineBreakEnumerator(text);
 
             var foundBreaks = new List<int>();
             
diff --git a/tests/Avalonia.Controls.UnitTests/Presenters/TextPresenter_Tests.cs b/tests/Avalonia.Controls.UnitTests/Presenters/TextPresenter_Tests.cs
index 8e06fbd831..61ce056c49 100644
--- a/tests/Avalonia.Controls.UnitTests/Presenters/TextPresenter_Tests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Presenters/TextPresenter_Tests.cs
@@ -46,7 +46,7 @@ namespace Avalonia.Controls.UnitTests.Presenters
                 Assert.NotNull(target.TextLayout);
 
                 var actual = string.Join(null,
-                    target.TextLayout.TextLines.SelectMany(x => x.TextRuns).Select(x => x.CharacterBufferReference.CharacterBuffer.Span.ToString()));
+                    target.TextLayout.TextLines.SelectMany(x => x.TextRuns).Select(x => x.Text.ToString()));
 
                 Assert.Equal("****", actual);
             }
diff --git a/tests/Avalonia.Skia.UnitTests/Media/GlyphRunTests.cs b/tests/Avalonia.Skia.UnitTests/Media/GlyphRunTests.cs
index 4083a67b5e..04bc401479 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/GlyphRunTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/GlyphRunTests.cs
@@ -19,7 +19,7 @@ namespace Avalonia.Skia.UnitTests.Media
             {
                 var options = new TextShaperOptions(Typeface.Default.GlyphTypeface, 10, direction, CultureInfo.CurrentCulture);
                 var shapedBuffer =
-                    TextShaper.Current.ShapeText(new CharacterBufferReference(text), text.Length, options);
+                    TextShaper.Current.ShapeText(text, options);
 
                 var glyphRun = CreateGlyphRun(shapedBuffer);
 
@@ -60,7 +60,7 @@ namespace Avalonia.Skia.UnitTests.Media
             {
                 var options = new TextShaperOptions(Typeface.Default.GlyphTypeface, 10, direction, CultureInfo.CurrentCulture);
                 var shapedBuffer =
-                    TextShaper.Current.ShapeText(new CharacterBufferReference(text), text.Length, options);
+                    TextShaper.Current.ShapeText(text, options);
 
                 var glyphRun = CreateGlyphRun(shapedBuffer);
 
@@ -103,7 +103,7 @@ namespace Avalonia.Skia.UnitTests.Media
             {
                 var options = new TextShaperOptions(Typeface.Default.GlyphTypeface, 10, direction, CultureInfo.CurrentCulture);
                 var shapedBuffer =
-                   TextShaper.Current.ShapeText(new CharacterBufferReference(text), text.Length, options);
+                   TextShaper.Current.ShapeText(text, options);
 
                 var glyphRun = CreateGlyphRun(shapedBuffer);
 
@@ -112,14 +112,14 @@ namespace Avalonia.Skia.UnitTests.Media
                     var characterHit =
                         glyphRun.GetCharacterHitFromDistance(glyphRun.Metrics.WidthIncludingTrailingWhitespace, out _);
                     
-                    Assert.Equal(glyphRun.Characters.Count, characterHit.FirstCharacterIndex + characterHit.TrailingLength);
+                    Assert.Equal(glyphRun.Characters.Length, characterHit.FirstCharacterIndex + characterHit.TrailingLength);
                 }
                 else
                 {
                      var characterHit =
                         glyphRun.GetCharacterHitFromDistance(0, out _);
                     
-                    Assert.Equal(glyphRun.Characters.Count, characterHit.FirstCharacterIndex + characterHit.TrailingLength);
+                    Assert.Equal(glyphRun.Characters.Length, characterHit.FirstCharacterIndex + characterHit.TrailingLength);
                 }
                 
                 var rects = BuildRects(glyphRun);
@@ -215,7 +215,7 @@ namespace Avalonia.Skia.UnitTests.Media
             var glyphRun =  new GlyphRun(
                 shapedBuffer.GlyphTypeface,
                 shapedBuffer.FontRenderingEmSize,
-                shapedBuffer.CharacterBufferRange,
+                shapedBuffer.Text,
                 shapedBuffer.GlyphIndices,
                 shapedBuffer.GlyphAdvances,
                 shapedBuffer.GlyphOffsets,
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/SingleBufferTextSource.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/SingleBufferTextSource.cs
index f12f42bd5e..f963277397 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/SingleBufferTextSource.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/SingleBufferTextSource.cs
@@ -1,15 +1,16 @@
-using Avalonia.Media.TextFormatting;
+using System;
+using Avalonia.Media.TextFormatting;
 
 namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 {
     internal class SingleBufferTextSource : ITextSource
     {
-        private readonly CharacterBufferRange _text;
+        private readonly string _text;
         private readonly GenericTextRunProperties _defaultGenericPropertiesRunProperties;
 
         public SingleBufferTextSource(string text, GenericTextRunProperties defaultProperties)
         {
-            _text = new CharacterBufferRange(text);
+            _text = text;
             _defaultGenericPropertiesRunProperties = defaultProperties;
         }
 
@@ -20,14 +21,14 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 return null;
             }
 
-            var runText = _text.Skip(textSourceIndex);
+            var runText = _text.AsMemory(textSourceIndex);
 
             if (runText.IsEmpty)
             {
                 return null;
             }
 
-            return new TextCharacters(runText.CharacterBufferReference, runText.Length, _defaultGenericPropertiesRunProperties);
+            return new TextCharacters(runText, _defaultGenericPropertiesRunProperties);
         }
     }
 }
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
index 1b6fd537eb..b90752861c 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs
@@ -279,7 +279,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
         {
             using (Start())
             {
-                var lineBreaker = new LineBreakEnumerator(new CharacterBufferRange(text));
+                var lineBreaker = new LineBreakEnumerator(text);
 
                 var expected = new List<int>();
 
@@ -677,7 +677,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                     return new RectangleRun(new Rect(0, 0, 50, 50), Brushes.Green);
                 }
 
-                return new TextCharacters(_text, 0, _text.Length, new GenericTextRunProperties(Typeface.Default, foregroundBrush: Brushes.Black));
+                return new TextCharacters(_text, new GenericTextRunProperties(Typeface.Default, foregroundBrush: Brushes.Black));
             }
         }
 
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
index 7501bf21fe..1fd26748cd 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLayoutTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
+using System.Runtime.InteropServices;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
@@ -62,7 +63,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 Assert.Equal(2, textRun.Length);
 
-                var actual = new CharacterBufferRange(textRun).Span.ToString();
+                var actual = textRun.Text.ToString();
 
                 Assert.Equal("1 ", actual);
 
@@ -144,8 +145,8 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 var expectedGlyphs = expected.TextLines.Select(x => string.Join('|', x.TextRuns.Cast<ShapedTextRun>()
                     .SelectMany(x => x.ShapedBuffer.GlyphIndices))).ToList();
 
-                var outer = new GraphemeEnumerator(new CharacterBufferRange(text));
-                var inner = new GraphemeEnumerator(new CharacterBufferRange(text));
+                var outer = new GraphemeEnumerator(text);
+                var inner = new GraphemeEnumerator(text);
                 var i = 0;
                 var j = 0;
 
@@ -153,7 +154,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 {
                     while (inner.MoveNext())
                     {
-                        j += inner.Current.Length;
+                        j += inner.Current.Text.Length;
 
                         if (j + i > text.Length)
                         {
@@ -190,9 +191,9 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                         break;
                     }
 
-                    inner = new GraphemeEnumerator(new CharacterBufferRange(text));
+                    inner = new GraphemeEnumerator(text);
 
-                    i += outer.Current.Length;
+                    i += outer.Current.Text.Length;
                 }
             }
         }
@@ -261,7 +262,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 Assert.Equal(2, textRun.Length);
 
-                var actual = new CharacterBufferRange(textRun).Span.ToString();
+                var actual = textRun.Text.ToString();
 
                 Assert.Equal("89", actual);
 
@@ -331,7 +332,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 Assert.Equal(2, textRun.Length);
 
-                var actual = new CharacterBufferRange(textRun).Span.ToString();
+                var actual = textRun.Text.ToString();
 
                 Assert.Equal("😄", actual);
 
@@ -667,10 +668,10 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 Assert.Equal(5, layout.TextLines.Count);
 
-                Assert.Equal("123\r\n", new CharacterBufferRange(layout.TextLines[0].TextRuns[0]));
-                Assert.Equal("\r\n", new CharacterBufferRange(layout.TextLines[1].TextRuns[0]));
-                Assert.Equal("456\r\n", new CharacterBufferRange(layout.TextLines[2].TextRuns[0]));
-                Assert.Equal("\r\n", new CharacterBufferRange(layout.TextLines[3].TextRuns[0]));
+                Assert.Equal("123\r\n", layout.TextLines[0].TextRuns[0].Text.ToString());
+                Assert.Equal("\r\n", layout.TextLines[1].TextRuns[0].Text.ToString());
+                Assert.Equal("456\r\n", layout.TextLines[2].TextRuns[0].Text.ToString());
+                Assert.Equal("\r\n", layout.TextLines[3].TextRuns[0].Text.ToString());
             }
         }
 
@@ -815,8 +816,9 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                         Assert.True(textLine.Width <= maxWidth);
 
                         var actual = new string(textLine.TextRuns.Cast<ShapedTextRun>()
-                            .OrderBy(x => x.CharacterBufferReference.OffsetToFirstChar)
-                            .SelectMany(x => new CharacterBufferRange(x.CharacterBufferReference, x.Length)).ToArray());
+                            .OrderBy(x => TextTestHelper.GetStartCharIndex(x.Text))
+                            .SelectMany(x => x.Text.ToString())
+                            .ToArray());
 
                         var expected = text.Substring(textLine.FirstTextSourceIndex, textLine.Length);
 
@@ -968,15 +970,15 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 var i = 0;
 
-                var graphemeEnumerator = new GraphemeEnumerator(new CharacterBufferRange(text));
+                var graphemeEnumerator = new GraphemeEnumerator(text);
 
                 while (graphemeEnumerator.MoveNext())
                 {
                     var grapheme = graphemeEnumerator.Current;
 
-                    var textStyleOverrides = new[] { new ValueSpan<TextRunProperties>(i, grapheme.Length, new GenericTextRunProperties(Typeface.Default, 12, foregroundBrush: Brushes.Red)) };
+                    var textStyleOverrides = new[] { new ValueSpan<TextRunProperties>(i, grapheme.Text.Length, new GenericTextRunProperties(Typeface.Default, 12, foregroundBrush: Brushes.Red)) };
 
-                    i += grapheme.Length;
+                    i += grapheme.Text.Length;
 
                     var layout = new TextLayout(
                         text,
@@ -1020,6 +1022,8 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
             }
         }
 
+
+
         private static IDisposable Start()
         {
             var disposable = UnitTestApplication.Start(TestServices.MockPlatformRenderInterface
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
index 2c6ccfa896..6993c70e8b 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextLineTests.cs
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
+using System.Runtime.InteropServices;
 using Avalonia.Media;
 using Avalonia.Media.TextFormatting;
 using Avalonia.UnitTests;
@@ -90,7 +91,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 var clusters = new List<int>();
 
-                foreach (var textRun in textLine.TextRuns.OrderBy(x => x.CharacterBufferReference.OffsetToFirstChar))
+                foreach (var textRun in textLine.TextRuns.OrderBy(x => TextTestHelper.GetStartCharIndex(x.Text)))
                 {
                     var shapedRun = (ShapedTextRun)textRun;
 
@@ -137,7 +138,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 var clusters = new List<int>();
 
-                foreach (var textRun in textLine.TextRuns.OrderBy(x => x.CharacterBufferReference.OffsetToFirstChar))
+                foreach (var textRun in textLine.TextRuns.OrderBy(x => TextTestHelper.GetStartCharIndex(x.Text)))
                 {
                     var shapedRun = (ShapedTextRun)textRun;
 
@@ -410,7 +411,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
 
                 Assert.True(collapsedLine.HasCollapsed);
 
-                var trimmedText = collapsedLine.TextRuns.SelectMany(x => new CharacterBufferRange(x)).ToArray();
+                var trimmedText = collapsedLine.TextRuns.SelectMany(x => x.Text.ToString()).ToArray();
 
                 Assert.Equal(expected.Length, trimmedText.Length);
 
@@ -653,7 +654,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                     var run = textRuns[i];
                     var bounds = runBounds[i];
 
-                    Assert.Equal(run.CharacterBufferReference.OffsetToFirstChar, bounds.TextSourceCharacterIndex);
+                    Assert.Equal(TextTestHelper.GetStartCharIndex(run.Text), bounds.TextSourceCharacterIndex);
                     Assert.Equal(run, bounds.TextRun);
                     Assert.Equal(run.Size.Width, bounds.Rectangle.Width);
                 }
diff --git a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextShaperTests.cs b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextShaperTests.cs
index 63e0083b1d..834dce4a90 100644
--- a/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextShaperTests.cs
+++ b/tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextShaperTests.cs
@@ -18,7 +18,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
                 var options = new TextShaperOptions(Typeface.Default.GlyphTypeface, 12,0, CultureInfo.CurrentCulture);
                 var shapedBuffer = TextShaper.Current.ShapeText(text, options);
                 
-                Assert.Equal(shapedBuffer.CharacterBufferRange.Length, text.Length);
+                Assert.Equal(shapedBuffer.Length, text.Length);
                 Assert.Equal(shapedBuffer.GlyphClusters.Count, text.Length);
                 Assert.Equal(0, shapedBuffer.GlyphClusters[0]);
                 Assert.Equal(1, shapedBuffer.GlyphClusters[1]);
diff --git a/tests/Avalonia.UnitTests/HarfBuzzTextShaperImpl.cs b/tests/Avalonia.UnitTests/HarfBuzzTextShaperImpl.cs
index ae7e00aca1..566cb0f1ac 100644
--- a/tests/Avalonia.UnitTests/HarfBuzzTextShaperImpl.cs
+++ b/tests/Avalonia.UnitTests/HarfBuzzTextShaperImpl.cs
@@ -1,18 +1,21 @@
 using System;
+using System.Buffers;
 using System.Globalization;
+using System.Runtime.InteropServices;
 using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Platform;
-using Avalonia.Utilities;
 using HarfBuzzSharp;
 using Buffer = HarfBuzzSharp.Buffer;
+using GlyphInfo = HarfBuzzSharp.GlyphInfo;
 
 namespace Avalonia.UnitTests
 {
-    public class HarfBuzzTextShaperImpl : ITextShaperImpl
+    internal class HarfBuzzTextShaperImpl : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(CharacterBufferReference text, int textLength, TextShaperOptions options)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options)
         {
+            var textSpan = text.Span;
             var typeface = options.Typeface;
             var fontRenderingEmSize = options.FontRenderingEmSize;
             var bidiLevel = options.BidiLevel;
@@ -20,15 +23,17 @@ namespace Avalonia.UnitTests
 
             using (var buffer = new Buffer())
             {
-                buffer.AddUtf16(text.CharacterBuffer.Span, text.OffsetToFirstChar, textLength);
+                // HarfBuzz needs the surrounding characters to correctly shape the text
+                var containingText = GetContainingMemory(text, out var start, out var length);
+                buffer.AddUtf16(containingText.Span, start, length);
 
                 MergeBreakPair(buffer);
-                
+
                 buffer.GuessSegmentProperties();
 
                 buffer.Direction = (bidiLevel & 1) == 0 ? Direction.LeftToRight : Direction.RightToLeft;
 
-                buffer.Language = new Language(culture ?? CultureInfo.CurrentCulture);              
+                buffer.Language = new Language(culture ?? CultureInfo.CurrentCulture);
 
                 var font = ((HarfBuzzGlyphTypefaceImpl)typeface).Font;
 
@@ -45,9 +50,7 @@ namespace Avalonia.UnitTests
 
                 var bufferLength = buffer.Length;
 
-                var characterBufferRange = new CharacterBufferRange(text, textLength);
-
-                var shapedBuffer = new ShapedBuffer(characterBufferRange, bufferLength, typeface, fontRenderingEmSize, bidiLevel);
+                var shapedBuffer = new ShapedBuffer(text, bufferLength, typeface, fontRenderingEmSize, bidiLevel);
 
                 var glyphInfos = buffer.GetGlyphInfoSpan();
 
@@ -59,12 +62,21 @@ namespace Avalonia.UnitTests
 
                     var glyphIndex = (ushort)sourceInfo.Codepoint;
 
-                    var glyphCluster = (int)sourceInfo.Cluster;
+                    var glyphCluster = (int)(sourceInfo.Cluster);
 
-                    var glyphAdvance = GetGlyphAdvance(glyphPositions, i, textScale);
+                    var glyphAdvance = GetGlyphAdvance(glyphPositions, i, textScale) + options.LetterSpacing;
 
                     var glyphOffset = GetGlyphOffset(glyphPositions, i, textScale);
 
+                    if (textSpan[i] == '\t')
+                    {
+                        glyphIndex = typeface.GetGlyph(' ');
+
+                        glyphAdvance = options.IncrementalTabWidth > 0 ?
+                            options.IncrementalTabWidth :
+                            4 * typeface.GetGlyphAdvance(glyphIndex) * textScale;
+                    }
+
                     var targetInfo = new Media.TextFormatting.GlyphInfo(glyphIndex, glyphCluster, glyphAdvance, glyphOffset);
 
                     shapedBuffer[i] = targetInfo;
@@ -79,7 +91,7 @@ namespace Avalonia.UnitTests
             var length = buffer.Length;
 
             var glyphInfos = buffer.GetGlyphInfoSpan();
-            
+
             var second = glyphInfos[length - 1];
 
             if (!new Codepoint(second.Codepoint).IsBreakChar)
@@ -90,19 +102,19 @@ namespace Avalonia.UnitTests
             if (length > 1 && glyphInfos[length - 2].Codepoint == '\r' && second.Codepoint == '\n')
             {
                 var first = glyphInfos[length - 2];
-                
+
                 first.Codepoint = '\u200C';
                 second.Codepoint = '\u200C';
                 second.Cluster = first.Cluster;
 
                 unsafe
                 {
-                    fixed (HarfBuzzSharp.GlyphInfo* p = &glyphInfos[length - 2])
+                    fixed (GlyphInfo* p = &glyphInfos[length - 2])
                     {
                         *p = first;
                     }
-                
-                    fixed (HarfBuzzSharp.GlyphInfo* p = &glyphInfos[length - 1])
+
+                    fixed (GlyphInfo* p = &glyphInfos[length - 1])
                     {
                         *p = second;
                     }
@@ -114,7 +126,7 @@ namespace Avalonia.UnitTests
 
                 unsafe
                 {
-                    fixed (HarfBuzzSharp.GlyphInfo* p = &glyphInfos[length - 1])
+                    fixed (GlyphInfo* p = &glyphInfos[length - 1])
                     {
                         *p = second;
                     }
@@ -136,8 +148,29 @@ namespace Avalonia.UnitTests
         private static double GetGlyphAdvance(ReadOnlySpan<GlyphPosition> glyphPositions, int index, double textScale)
         {
             // Depends on direction of layout
-            // advanceBuffer[index] = buffer.GlyphPositions[index].YAdvance * textScale;
+            // glyphPositions[index].YAdvance * textScale;
             return glyphPositions[index].XAdvance * textScale;
         }
+
+        private static ReadOnlyMemory<char> GetContainingMemory(ReadOnlyMemory<char> memory, out int start, out int length)
+        {
+            if (MemoryMarshal.TryGetString(memory, out var containingString, out start, out length))
+            {
+                return containingString.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetArray(memory, out var segment))
+            {
+                return segment.Array.AsMemory();
+            }
+
+            if (MemoryMarshal.TryGetMemoryManager(memory, out MemoryManager<char> memoryManager, out start, out length))
+            {
+                return memoryManager.Memory;
+            }
+
+            // should never happen
+            throw new InvalidOperationException("Memory not backed by string, array or manager");
+        }
     }
 }
diff --git a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
index 00bcef295a..3218139251 100644
--- a/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
+++ b/tests/Avalonia.UnitTests/MockTextShaperImpl.cs
@@ -1,4 +1,5 @@
-using Avalonia.Media.TextFormatting;
+using System;
+using Avalonia.Media.TextFormatting;
 using Avalonia.Media.TextFormatting.Unicode;
 using Avalonia.Platform;
 
@@ -6,19 +7,20 @@ namespace Avalonia.UnitTests
 {
     public class MockTextShaperImpl : ITextShaperImpl
     {
-        public ShapedBuffer ShapeText(CharacterBufferReference text, int length, TextShaperOptions options)
+        public ShapedBuffer ShapeText(ReadOnlyMemory<char> text, TextShaperOptions options)
         {
             var typeface = options.Typeface;
             var fontRenderingEmSize = options.FontRenderingEmSize;
             var bidiLevel = options.BidiLevel;
-            var characterBufferRange = new CharacterBufferRange(text, length);
-            var shapedBuffer = new ShapedBuffer(characterBufferRange, length, typeface, fontRenderingEmSize, bidiLevel);
+            var shapedBuffer = new ShapedBuffer(text, text.Length, typeface, fontRenderingEmSize, bidiLevel);
+            var textSpan = text.Span;
+            var textStartIndex = TextTestHelper.GetStartCharIndex(text);
 
             for (var i = 0; i < shapedBuffer.Length;)
             {
-                var glyphCluster = i + text.OffsetToFirstChar;
+                var glyphCluster = i + textStartIndex;
 
-                var codepoint = Codepoint.ReadAt(characterBufferRange, i, out var count);
+                var codepoint = Codepoint.ReadAt(textSpan, i, out var count);
 
                 var glyphIndex = typeface.GetGlyph(codepoint);
 
diff --git a/tests/Avalonia.UnitTests/TextTestHelper.cs b/tests/Avalonia.UnitTests/TextTestHelper.cs
new file mode 100644
index 0000000000..b572333027
--- /dev/null
+++ b/tests/Avalonia.UnitTests/TextTestHelper.cs
@@ -0,0 +1,15 @@
+using System;
+using System.Runtime.InteropServices;
+
+namespace Avalonia.UnitTests
+{
+    public static class TextTestHelper
+    {
+        public static int GetStartCharIndex(ReadOnlyMemory<char> text)
+        {
+            if (!MemoryMarshal.TryGetString(text, out _, out var start, out _))
+                throw new InvalidOperationException("text memory should have been a string");
+            return start;
+        }
+    }
+}

From 5936f52b2c0cba31d11bf366e74dfedfda299a12 Mon Sep 17 00:00:00 2001
From: Emmanuel Hansen <emmausssss@gmail.com>
Date: Tue, 3 Jan 2023 13:48:36 +0000
Subject: [PATCH 151/157] Add back requested event for TopLevel

---
 .../Avalonia.Android/AvaloniaMainActivity.cs  | 19 ++++---
 .../IAndroidNavigationService.cs              | 14 +++++
 .../AndroidSystemNavigationManager.cs         | 28 ++++++++++
 .../Platform/SkiaPlatform/TopLevelImpl.cs     |  7 ++-
 .../Platform/SystemNavigationManager.cs       | 18 ++++++
 src/Avalonia.Controls/TopLevel.cs             | 56 +++++++++++++++++++
 6 files changed, 134 insertions(+), 8 deletions(-)
 create mode 100644 src/Android/Avalonia.Android/IAndroidNavigationService.cs
 create mode 100644 src/Android/Avalonia.Android/Platform/AndroidSystemNavigationManager.cs
 create mode 100644 src/Avalonia.Base/Platform/SystemNavigationManager.cs

diff --git a/src/Android/Avalonia.Android/AvaloniaMainActivity.cs b/src/Android/Avalonia.Android/AvaloniaMainActivity.cs
index b24581fb8b..c06f5c74ec 100644
--- a/src/Android/Avalonia.Android/AvaloniaMainActivity.cs
+++ b/src/Android/Avalonia.Android/AvaloniaMainActivity.cs
@@ -1,18 +1,14 @@
 using System;
 using Android.App;
 using Android.Content;
-using Android.Content.Res;
 using Android.OS;
 using Android.Runtime;
 using Android.Views;
 using AndroidX.AppCompat.App;
-using AndroidX.Lifecycle;
-
-using AndroidRect = Android.Graphics.Rect;
 
 namespace Avalonia.Android
 {
-    public abstract class AvaloniaMainActivity : AppCompatActivity, IActivityResultHandler
+    public abstract class AvaloniaMainActivity : AppCompatActivity, IActivityResultHandler, IActivityNavigationService
     {
         internal static object ViewContent;
 
@@ -56,9 +52,18 @@ namespace Avalonia.Android
             }
         }
 
-        public override void OnConfigurationChanged(Configuration newConfig)
+        public event EventHandler<AndroidBackRequestedEventArgs> BackRequested;
+
+        public override void OnBackPressed()
         {
-            base.OnConfigurationChanged(newConfig);
+            var eventArgs = new AndroidBackRequestedEventArgs();
+
+            BackRequested?.Invoke(this, eventArgs);
+
+            if (!eventArgs.Handled)
+            {
+                base.OnBackPressed();
+            }
         }
 
         protected override void OnDestroy()
diff --git a/src/Android/Avalonia.Android/IAndroidNavigationService.cs b/src/Android/Avalonia.Android/IAndroidNavigationService.cs
new file mode 100644
index 0000000000..5fa93971d9
--- /dev/null
+++ b/src/Android/Avalonia.Android/IAndroidNavigationService.cs
@@ -0,0 +1,14 @@
+using System;
+
+namespace Avalonia.Android
+{
+    public interface IActivityNavigationService
+    {
+        event EventHandler<AndroidBackRequestedEventArgs> BackRequested;
+    }
+
+    public class AndroidBackRequestedEventArgs : EventArgs
+    {
+        public bool Handled { get; set; }
+    }
+}
diff --git a/src/Android/Avalonia.Android/Platform/AndroidSystemNavigationManager.cs b/src/Android/Avalonia.Android/Platform/AndroidSystemNavigationManager.cs
new file mode 100644
index 0000000000..bb9dc66f5a
--- /dev/null
+++ b/src/Android/Avalonia.Android/Platform/AndroidSystemNavigationManager.cs
@@ -0,0 +1,28 @@
+using System;
+using Avalonia.Interactivity;
+using Avalonia.Platform;
+
+namespace Avalonia.Android.Platform
+{
+    internal class AndroidSystemNavigationManager : ISystemNavigationManager
+    {
+        public event EventHandler<RoutedEventArgs> BackRequested;
+
+        public AndroidSystemNavigationManager(IActivityNavigationService? navigationService)
+        {
+            if(navigationService != null)
+            {
+                navigationService.BackRequested += OnBackRequested;
+            }
+        }
+
+        private void OnBackRequested(object sender, AndroidBackRequestedEventArgs e)
+        {
+            var routedEventArgs = new RoutedEventArgs();
+
+            BackRequested?.Invoke(this, routedEventArgs);
+
+            e.Handled = routedEventArgs.Handled;
+        }
+    }
+}
diff --git a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
index 1aac567dda..c504a951e5 100644
--- a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
+++ b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
@@ -31,7 +31,8 @@ using Android.Graphics.Drawables;
 namespace Avalonia.Android.Platform.SkiaPlatform
 {
     class TopLevelImpl : IAndroidView, ITopLevelImpl, EglGlPlatformSurface.IEglWindowGlPlatformSurfaceInfo,
-        ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider
+        ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider,
+        ITopLevelWithSystemNavigationManager
     {
         private readonly IGlPlatformSurface _gl;
         private readonly IFramebufferPlatformSurface _framebuffer;
@@ -57,6 +58,8 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
             NativeControlHost = new AndroidNativeControlHostImpl(avaloniaView);
             StorageProvider = new AndroidStorageProvider((Activity)avaloniaView.Context);
+
+            SystemNavigationManager = new AndroidSystemNavigationManager(avaloniaView.Context as IActivityNavigationService);
         }
 
         public virtual Point GetAvaloniaPointFromEvent(MotionEvent e, int pointerIndex) =>
@@ -300,6 +303,8 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         
         public IStorageProvider StorageProvider { get; }
 
+        public ISystemNavigationManager SystemNavigationManager { get; }
+
         public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel)
         {
             if (TransparencyLevel != transparencyLevel)
diff --git a/src/Avalonia.Base/Platform/SystemNavigationManager.cs b/src/Avalonia.Base/Platform/SystemNavigationManager.cs
new file mode 100644
index 0000000000..6165b2bb77
--- /dev/null
+++ b/src/Avalonia.Base/Platform/SystemNavigationManager.cs
@@ -0,0 +1,18 @@
+using System;
+using Avalonia.Interactivity;
+using Avalonia.Metadata;
+
+namespace Avalonia.Platform
+{
+    [Unstable]
+    public interface ITopLevelWithSystemNavigationManager
+    {
+        ISystemNavigationManager SystemNavigationManager { get; }
+    }
+
+    [Unstable]
+    public interface ISystemNavigationManager
+    {
+        public event EventHandler<RoutedEventArgs>? BackRequested;
+    }
+}
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 9970a0f1c7..66c108b436 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -7,6 +7,7 @@ using Avalonia.Controls.Primitives;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
 using Avalonia.Input.TextInput;
+using Avalonia.Interactivity;
 using Avalonia.Layout;
 using Avalonia.Logging;
 using Avalonia.LogicalTree;
@@ -76,6 +77,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBrush> TransparencyBackgroundFallbackProperty =
             AvaloniaProperty.Register<TopLevel, IBrush>(nameof(TransparencyBackgroundFallback), Brushes.White);
 
+        /// <summary>
+        /// Defines the <see cref="BackRequested"/> event.
+        /// </summary>
+        public static readonly RoutedEvent<RoutedEventArgs> BackRequestedEvent = 
+            RoutedEvent.Register<TopLevel, RoutedEventArgs>(nameof(BackRequested), RoutingStrategies.Bubble);
+
         private static readonly WeakEvent<IResourceHost, ResourcesChangedEventArgs>
             ResourcesChangedWeakEvent = WeakEvent.Register<IResourceHost, ResourcesChangedEventArgs>(
                 (s, h) => s.ResourcesChanged += h,
@@ -89,6 +96,7 @@ namespace Avalonia.Controls
         private readonly IGlobalStyles? _globalStyles;
         private readonly PointerOverPreProcessor? _pointerOverPreProcessor;
         private readonly IDisposable? _pointerOverPreProcessorSubscription;
+        private readonly IDisposable? _backGestureSubscription;
         private Size _clientSize;
         private Size? _frameSize;
         private WindowTransparencyLevel _actualTransparencyLevel;
@@ -205,6 +213,44 @@ namespace Avalonia.Controls
 
             _pointerOverPreProcessor = new PointerOverPreProcessor(this);
             _pointerOverPreProcessorSubscription = _inputManager?.PreProcess.Subscribe(_pointerOverPreProcessor);
+
+            if(impl is ITopLevelWithSystemNavigationManager topLevelWithSystemNavigation)
+            {
+                topLevelWithSystemNavigation.SystemNavigationManager.BackRequested += (s, e) =>
+                {
+                    e.RoutedEvent = BackRequestedEvent;
+                    RaiseEvent(e);
+                };
+            }
+
+            var backKeyGesture = new KeyGesture(Key.Left, KeyModifiers.Alt);
+            _backGestureSubscription = _inputManager?.PreProcess.OfType<RawInputEventArgs>().Subscribe(e =>
+            {
+                bool backRequested = false;
+
+                if (e is RawKeyEventArgs rawKeyEventArgs && rawKeyEventArgs.Type == RawKeyEventType.KeyDown)
+                {
+                    var keyEvent = new KeyEventArgs()
+                    {
+                        KeyModifiers = (KeyModifiers)rawKeyEventArgs.Modifiers,
+                        Key = rawKeyEventArgs.Key
+                    };
+
+                    backRequested = backKeyGesture.Matches(keyEvent);
+                }
+                else if(e is RawPointerEventArgs pointerEventArgs)
+                {
+                    backRequested = pointerEventArgs.Type == RawPointerEventType.XButton1Down;
+                }
+
+                if (backRequested)
+                {
+                    var backRequestedEventArgs = new RoutedEventArgs(BackRequestedEvent);
+                    RaiseEvent(backRequestedEventArgs);
+
+                    e.Handled = backRequestedEventArgs.Handled;
+                }
+            });
         }
 
         /// <summary>
@@ -263,6 +309,15 @@ namespace Avalonia.Controls
             set => SetValue(TransparencyBackgroundFallbackProperty, value);
         }
 
+        /// <summary>
+        /// Occurs when physical Back Button is pressed or a back navigation has been requested.
+        /// </summary>
+        public event EventHandler<RoutedEvent> BackRequested
+        {
+            add { AddHandler(BackRequestedEvent, value); }
+            remove { RemoveHandler(BackRequestedEvent, value); }
+        }
+
         public ILayoutManager LayoutManager
         {
             get
@@ -382,6 +437,7 @@ namespace Avalonia.Controls
 
             _pointerOverPreProcessor?.OnCompleted();
             _pointerOverPreProcessorSubscription?.Dispose();
+            _backGestureSubscription?.Dispose();
 
             PlatformImpl = null;
 

From a75753c9426c5c47b490c24511d082704e244a10 Mon Sep 17 00:00:00 2001
From: Dmitry Zhelnin <d.zhelnin@of-group.ru>
Date: Fri, 6 Jan 2023 16:28:34 +0300
Subject: [PATCH 152/157] EventRoute: remove additional check if event was
 handled

---
 src/Avalonia.Base/Interactivity/EventRoute.cs |  5 +---
 .../Interactivity/InteractiveTests.cs         | 26 +++++++++++++++++++
 2 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Base/Interactivity/EventRoute.cs b/src/Avalonia.Base/Interactivity/EventRoute.cs
index 3491465a68..37539a7153 100644
--- a/src/Avalonia.Base/Interactivity/EventRoute.cs
+++ b/src/Avalonia.Base/Interactivity/EventRoute.cs
@@ -143,10 +143,7 @@ namespace Avalonia.Interactivity
                 // If we've got to a new control then call any RoutedEvent.Raised listeners.
                 if (entry.Target != lastTarget)
                 {
-                    if (!e.Handled)
-                    {
-                        _event.InvokeRaised(entry.Target, e);
-                    }
+                    _event.InvokeRaised(entry.Target, e);
 
                     // If this is a direct event and we've already raised events then we're finished.
                     if (e.Route == RoutingStrategies.Direct && lastTarget is object)
diff --git a/tests/Avalonia.Base.UnitTests/Interactivity/InteractiveTests.cs b/tests/Avalonia.Base.UnitTests/Interactivity/InteractiveTests.cs
index 1a8b72d5e5..49119c3830 100644
--- a/tests/Avalonia.Base.UnitTests/Interactivity/InteractiveTests.cs
+++ b/tests/Avalonia.Base.UnitTests/Interactivity/InteractiveTests.cs
@@ -337,6 +337,27 @@ namespace Avalonia.Base.UnitTests.Interactivity
             Assert.True(target.GetVisualParent<TestInteractive>().ClassHandlerInvoked);
         }
 
+        [Fact]
+        public void Typed_Class_Handlers_Should_Be_Called_For_Handled_Events()
+        {
+            var ev = new RoutedEvent<RoutedEventArgs>(
+                "test",
+                RoutingStrategies.Bubble | RoutingStrategies.Tunnel,
+                typeof(TestInteractive));
+
+            var target = CreateTree(ev, null, 0);
+
+            ev.AddClassHandler<TestInteractive>((x, e) => x.MarkEventAsHandled(e), RoutingStrategies.Bubble);
+            ev.AddClassHandler<TestInteractive>((x, e) => x.ClassHandler(e), RoutingStrategies.Bubble, handledEventsToo: true);
+
+            var args = new RoutedEventArgs(ev, target);
+            target.RaiseEvent(args);
+
+            Assert.True(args.Handled);
+            Assert.True(target.ClassHandlerInvoked);
+            Assert.True(target.GetVisualParent<TestInteractive>().ClassHandlerInvoked);
+        }
+
         [Fact]
         public void GetObservable_Should_Listen_To_Event()
         {
@@ -443,6 +464,11 @@ namespace Avalonia.Base.UnitTests.Interactivity
             {
                 ClassHandlerInvoked = true;
             }
+
+            public void MarkEventAsHandled(RoutedEventArgs e)
+            {
+                e.Handled = true;
+            }
         }
     }
 }

From 1a0492dcb0a239432a851c829179b94120391612 Mon Sep 17 00:00:00 2001
From: Giuseppe Lippolis <workgroupengineering@outlook.com>
Date: Mon, 16 Jan 2023 12:24:51 +0100
Subject: [PATCH 153/157] fix: Warning CS0105: The using directive for
 'Avalonia.Reactive' appeared previously in this namespace

---
 src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs       | 1 -
 src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs    | 4 ----
 src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs         | 1 -
 .../Avalonia.Win32/WindowsMountedVolumeInfoListener.cs        | 1 -
 4 files changed, 7 deletions(-)

diff --git a/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs b/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
index d6c46bb1e0..01badf3833 100644
--- a/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
+++ b/src/Avalonia.Controls.DataGrid/Utils/CellEditBinding.cs
@@ -2,7 +2,6 @@
 using Avalonia.Reactive;
 using System;
 using System.Collections.Generic;
-using Avalonia.Reactive;
 
 namespace Avalonia.Controls.Utils
 {
diff --git a/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs b/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
index 9f6b056d30..53a6f4519e 100644
--- a/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
+++ b/src/Avalonia.FreeDesktop/LinuxMountedVolumeInfoListener.cs
@@ -1,14 +1,10 @@
 using System;
 using System.IO;
 using System.Linq;
-using System.Collections.Generic;
 using System.Collections.ObjectModel;
 using Avalonia.Controls.Platform;
 using Avalonia.Reactive;
-using Avalonia.Reactive;
 using System.Text.RegularExpressions;
-using System.Runtime.InteropServices;
-using System.Text;
 using Avalonia.Threading;
 
 namespace Avalonia.FreeDesktop
diff --git a/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs b/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
index 6f45baeec2..e79c7a40d3 100644
--- a/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
+++ b/src/Avalonia.Native/MacOSMountedVolumeInfoProvider.cs
@@ -3,7 +3,6 @@ using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
 using Avalonia.Reactive;
-using Avalonia.Reactive;
 using Avalonia.Controls.Platform;
 using Avalonia.Threading;
 
diff --git a/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs b/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
index 94e9c0c814..3244e75a34 100644
--- a/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
+++ b/src/Windows/Avalonia.Win32/WindowsMountedVolumeInfoListener.cs
@@ -3,7 +3,6 @@ using System.Collections.ObjectModel;
 using System.IO;
 using System.Linq;
 using Avalonia.Reactive;
-using Avalonia.Reactive;
 using Avalonia.Controls.Platform;
 using Avalonia.Logging;
 using Avalonia.Threading;

From ac206db0980fd3483b3dc3c5db571ec512f965ca Mon Sep 17 00:00:00 2001
From: Emmanuel Hansen <emmausssss@gmail.com>
Date: Mon, 16 Jan 2023 14:14:53 +0000
Subject: [PATCH 154/157] add browser support

---
 .../Platform/PlatformHotkeyConfiguration.cs   |  5 ++++
 src/Avalonia.Controls/TopLevel.cs             | 20 ++++++++++------
 .../BrowserSystemNavigationManager.cs         | 24 +++++++++++++++++++
 .../Avalonia.Browser/BrowserTopLevelImpl.cs   |  5 +++-
 .../Interop/NavigationHelper.cs               | 10 ++++++++
 .../webapp/modules/avalonia.ts                |  5 +++-
 .../modules/avalonia/navigationHelper.ts      | 14 +++++++++++
 7 files changed, 74 insertions(+), 9 deletions(-)
 create mode 100644 src/Browser/Avalonia.Browser/BrowserSystemNavigationManager.cs
 create mode 100644 src/Browser/Avalonia.Browser/Interop/NavigationHelper.cs
 create mode 100644 src/Browser/Avalonia.Browser/webapp/modules/avalonia/navigationHelper.ts

diff --git a/src/Avalonia.Base/Input/Platform/PlatformHotkeyConfiguration.cs b/src/Avalonia.Base/Input/Platform/PlatformHotkeyConfiguration.cs
index 1fc46dd396..b87ca5eded 100644
--- a/src/Avalonia.Base/Input/Platform/PlatformHotkeyConfiguration.cs
+++ b/src/Avalonia.Base/Input/Platform/PlatformHotkeyConfiguration.cs
@@ -81,6 +81,10 @@ namespace Avalonia.Input.Platform
             {
                 new KeyGesture(Key.Apps)
             };
+            Back = new List<KeyGesture>
+            {
+                new KeyGesture(Key.Left, KeyModifiers.Alt)
+            };
         }
 
         public KeyModifiers CommandModifiers { get; set; }
@@ -101,5 +105,6 @@ namespace Avalonia.Input.Platform
         public List<KeyGesture> MoveCursorToTheStartOfDocumentWithSelection { get; set; }
         public List<KeyGesture> MoveCursorToTheEndOfDocumentWithSelection { get; set; }
         public List<KeyGesture> OpenContextMenu { get; set; }
+        public List<KeyGesture> Back { get; set; }
     }
 }
diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index 66c108b436..c0265e28b9 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -18,6 +18,8 @@ using Avalonia.Rendering;
 using Avalonia.Styling;
 using Avalonia.Utilities;
 using Avalonia.VisualTree;
+using Avalonia.Input.Platform;
+using System.Linq;
 
 namespace Avalonia.Controls
 {
@@ -223,20 +225,24 @@ namespace Avalonia.Controls
                 };
             }
 
-            var backKeyGesture = new KeyGesture(Key.Left, KeyModifiers.Alt);
-            _backGestureSubscription = _inputManager?.PreProcess.OfType<RawInputEventArgs>().Subscribe(e =>
+            _backGestureSubscription = _inputManager?.PreProcess.Subscribe(e =>
             {
                 bool backRequested = false;
 
                 if (e is RawKeyEventArgs rawKeyEventArgs && rawKeyEventArgs.Type == RawKeyEventType.KeyDown)
                 {
-                    var keyEvent = new KeyEventArgs()
+                    var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>()?.Back;
+
+                    if (keymap != null)
                     {
-                        KeyModifiers = (KeyModifiers)rawKeyEventArgs.Modifiers,
-                        Key = rawKeyEventArgs.Key
-                    };
+                        var keyEvent = new KeyEventArgs()
+                        {
+                            KeyModifiers = (KeyModifiers)rawKeyEventArgs.Modifiers,
+                            Key = rawKeyEventArgs.Key
+                        };
 
-                    backRequested = backKeyGesture.Matches(keyEvent);
+                        backRequested = keymap.Any( key => key.Matches(keyEvent));
+                    }
                 }
                 else if(e is RawPointerEventArgs pointerEventArgs)
                 {
diff --git a/src/Browser/Avalonia.Browser/BrowserSystemNavigationManager.cs b/src/Browser/Avalonia.Browser/BrowserSystemNavigationManager.cs
new file mode 100644
index 0000000000..cc7d8c3af1
--- /dev/null
+++ b/src/Browser/Avalonia.Browser/BrowserSystemNavigationManager.cs
@@ -0,0 +1,24 @@
+using System;
+using Avalonia.Browser.Interop;
+using Avalonia.Interactivity;
+using Avalonia.Platform;
+
+namespace Avalonia.Browser
+{
+    internal class BrowserSystemNavigationManager : ISystemNavigationManager
+    {
+        public event EventHandler<RoutedEventArgs>? BackRequested;
+
+        public BrowserSystemNavigationManager()
+        {
+            NavigationHelper.AddBackHandler(() =>
+            {
+                var routedEventArgs = new RoutedEventArgs();
+
+                BackRequested?.Invoke(this, routedEventArgs);
+
+                return routedEventArgs.Handled;
+            });
+        }
+    }
+}
diff --git a/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs b/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
index 4e6be3268b..90310fb0e1 100644
--- a/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
+++ b/src/Browser/Avalonia.Browser/BrowserTopLevelImpl.cs
@@ -19,7 +19,8 @@ using Avalonia.Rendering.Composition;
 
 namespace Avalonia.Browser
 {
-    internal class BrowserTopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider
+    internal class BrowserTopLevelImpl : ITopLevelImplWithTextInputMethod, ITopLevelImplWithNativeControlHost, ITopLevelImplWithStorageProvider,
+        ITopLevelWithSystemNavigationManager
     {
         private Size _clientSize;
         private IInputRoot? _inputRoot;
@@ -234,5 +235,7 @@ namespace Avalonia.Browser
 
         public INativeControlHostImpl? NativeControlHost { get; }
         public IStorageProvider StorageProvider { get; } = new BrowserStorageProvider();
+
+        public ISystemNavigationManager SystemNavigationManager { get; } = new BrowserSystemNavigationManager();
     }
 }
diff --git a/src/Browser/Avalonia.Browser/Interop/NavigationHelper.cs b/src/Browser/Avalonia.Browser/Interop/NavigationHelper.cs
new file mode 100644
index 0000000000..d49b83b5a0
--- /dev/null
+++ b/src/Browser/Avalonia.Browser/Interop/NavigationHelper.cs
@@ -0,0 +1,10 @@
+using System;
+using System.Runtime.InteropServices.JavaScript;
+
+namespace Avalonia.Browser.Interop;
+
+internal static partial class NavigationHelper
+{
+    [JSImport("NavigationHelper.addBackHandler", AvaloniaModule.MainModuleName)]
+    public static partial void AddBackHandler([JSMarshalAs<JSType.Function<JSType.Boolean>>] Func<bool> backHandlerCallback);
+}
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia.ts
index 0642bd475d..ab0c85eaa2 100644
--- a/src/Browser/Avalonia.Browser/webapp/modules/avalonia.ts
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia.ts
@@ -5,6 +5,7 @@ import { AvaloniaDOM } from "./avalonia/dom";
 import { Caniuse } from "./avalonia/caniuse";
 import { StreamHelper } from "./avalonia/stream";
 import { NativeControlHost } from "./avalonia/nativeControlHost";
+import { NavigationHelper } from "./avalonia/navigationHelper";
 
 async function registerAvaloniaModule(api: RuntimeAPI): Promise<void> {
     api.setModuleImports("avalonia", {
@@ -15,7 +16,8 @@ async function registerAvaloniaModule(api: RuntimeAPI): Promise<void> {
         DpiWatcher,
         AvaloniaDOM,
         StreamHelper,
-        NativeControlHost
+        NativeControlHost,
+        NavigationHelper
     });
 }
 export {
@@ -27,6 +29,7 @@ export {
     AvaloniaDOM,
     StreamHelper,
     NativeControlHost,
+    NavigationHelper,
 
     registerAvaloniaModule
 };
diff --git a/src/Browser/Avalonia.Browser/webapp/modules/avalonia/navigationHelper.ts b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/navigationHelper.ts
new file mode 100644
index 0000000000..ee594fe85c
--- /dev/null
+++ b/src/Browser/Avalonia.Browser/webapp/modules/avalonia/navigationHelper.ts
@@ -0,0 +1,14 @@
+export class NavigationHelper {
+    public static addBackHandler(backHandlerCallback: () => Boolean) {
+        history.pushState(null, "", window.location.href);
+        window.onpopstate = () => {
+            const handled = backHandlerCallback();
+
+            if (!handled) {
+                history.back();
+            } else {
+                history.forward();
+            }
+        };
+    }
+}

From c1410af0d5edca7db2ca136c6e94131a563bd212 Mon Sep 17 00:00:00 2001
From: mrmandrake <manuel.mazzetto@tesigroup.tech>
Date: Wed, 18 Jan 2023 00:47:50 +0100
Subject: [PATCH 155/157] Update TextInputResponder.cs

fixes #9956
---
 src/iOS/Avalonia.iOS/TextInputResponder.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/iOS/Avalonia.iOS/TextInputResponder.cs b/src/iOS/Avalonia.iOS/TextInputResponder.cs
index d5723d78f7..8862f4e392 100644
--- a/src/iOS/Avalonia.iOS/TextInputResponder.cs
+++ b/src/iOS/Avalonia.iOS/TextInputResponder.cs
@@ -445,7 +445,7 @@ partial class AvaloniaView
 
         UITextPosition IUITextInput.BeginningOfDocument => _beginningOfDocument;
 
-        private int DocumentLength => _client.SurroundingText.Text.Length + (_markedText?.Length ?? 0);
+        private int DocumentLength => (_client.SurroundingText.Text?.Length ?? 0) + (_markedText?.Length ?? 0);
         UITextPosition IUITextInput.EndOfDocument => new AvaloniaTextPosition(DocumentLength);
 
         UITextRange IUITextInput.MarkedTextRange

From f675750aba8d17ae4f93fa96386995d92b702e72 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Wies=C5=82aw=20=C5=A0olt=C3=A9s?=
 <wieslawsoltes@users.noreply.github.com>
Date: Wed, 18 Jan 2023 11:30:21 +0100
Subject: [PATCH 156/157] Fix BackRequested EventHandler args type

---
 src/Avalonia.Controls/TopLevel.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/TopLevel.cs b/src/Avalonia.Controls/TopLevel.cs
index c0265e28b9..ff241dce7a 100644
--- a/src/Avalonia.Controls/TopLevel.cs
+++ b/src/Avalonia.Controls/TopLevel.cs
@@ -318,7 +318,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Occurs when physical Back Button is pressed or a back navigation has been requested.
         /// </summary>
-        public event EventHandler<RoutedEvent> BackRequested
+        public event EventHandler<RoutedEventArgs> BackRequested
         {
             add { AddHandler(BackRequestedEvent, value); }
             remove { RemoveHandler(BackRequestedEvent, value); }

From 85e7f383a21a8519920316b73ee3a90148441e22 Mon Sep 17 00:00:00 2001
From: Emmanuel Hansen <emmausssss@gmail.com>
Date: Wed, 18 Jan 2023 11:13:44 +0000
Subject: [PATCH 157/157] fix crash in previewer for refresh container

---
 src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs b/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
index 8723304f8f..d2a35bb6aa 100644
--- a/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
+++ b/src/Avalonia.Controls/PullToRefresh/RefreshVisualizer.cs
@@ -151,7 +151,11 @@ namespace Avalonia.Controls
                     _content.Loaded += (s, e) =>
                     {
                         var composition = ElementComposition.GetElementVisual(_content);
-                        var compositor = composition!.Compositor;
+
+                        if(composition == null)
+                            return;
+
+                        var compositor = composition.Compositor;
                         composition.Opacity = 0;
 
                         var smoothRotationAnimation