Merge branch 'master' into compiledbinding-methods

Avalonia.sln

@@ -60,20 +60,17 @@ EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Shared", "Shared", "{A689DEF5-D50F-4975-8B72-124C9EB54066}"
 	ProjectSection(SolutionItems) = preProject
 		.editorconfig = .editorconfig
+		src\Shared\ModuleInitializer.cs = src\Shared\ModuleInitializer.cs
 	EndProjectSection
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.ReactiveUI", "src\Avalonia.ReactiveUI\Avalonia.ReactiveUI.csproj", "{6417B24E-49C2-4985-8DB2-3AB9D898EC91}"
 EndProject
-Project("{D954291E-2A0B-460D-934E-DC6B0785DB48}") = "PlatformSupport", "src\Shared\PlatformSupport\PlatformSupport.shproj", "{E4D9629C-F168-4224-3F51-A5E482FFBC42}"
-EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Markup", "src\Markup\Avalonia.Markup\Avalonia.Markup.csproj", "{6417E941-21BC-467B-A771-0DE389353CE6}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Markup.UnitTests", "tests\Avalonia.Markup.UnitTests\Avalonia.Markup.UnitTests.csproj", "{8EF392D5-1416-45AA-9956-7CBBC3229E8A}"
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "BindingDemo", "samples\BindingDemo\BindingDemo.csproj", "{08B3E6B9-1CD5-443C-9F61-6D49D1C5F162}"
 EndProject
-Project("{D954291E-2A0B-460D-934E-DC6B0785DB48}") = "RenderHelpers", "src\Shared\RenderHelpers\RenderHelpers.shproj", "{3C4C0CB4-0C0F-4450-A37B-148C84FF905F}"
-EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Skia", "Skia", "{3743B0F2-CC41-4F14-A8C8-267F579BF91E}"
 EndProject
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Android", "Android", "{7CF9789C-F1D3-4D0E-90E5-F1DF67A2753F}"
@@ -235,15 +232,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "WindowsInteropTest", "sampl
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "ControlSamples", "samples\SampleControls\ControlSamples.csproj", "{A0D0A6A4-5C72-4ADA-9B27-621C7D94F270}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.PlatformSupport", "src\Avalonia.PlatformSupport\Avalonia.PlatformSupport.csproj", "{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}"
+EndProject
 Global
-	GlobalSection(SharedMSBuildProjectFiles) = preSolution
-		src\Shared\RenderHelpers\RenderHelpers.projitems*{3c4c0cb4-0c0f-4450-a37b-148c84ff905f}*SharedItemsImports = 13
-		src\Shared\RenderHelpers\RenderHelpers.projitems*{3e908f67-5543-4879-a1dc-08eace79b3cd}*SharedItemsImports = 5
-		src\Shared\PlatformSupport\PlatformSupport.projitems*{7b92af71-6287-4693-9dcb-bd5b6e927e23}*SharedItemsImports = 5
-		src\Shared\RenderHelpers\RenderHelpers.projitems*{7d2d3083-71dd-4cc9-8907-39a0d86fb322}*SharedItemsImports = 5
-		src\Shared\PlatformSupport\PlatformSupport.projitems*{88060192-33d5-4932-b0f9-8bd2763e857d}*SharedItemsImports = 5
-		src\Shared\PlatformSupport\PlatformSupport.projitems*{e4d9629c-f168-4224-3f51-a5e482ffbc42}*SharedItemsImports = 13
-	EndGlobalSection
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Ad-Hoc|Any CPU = Ad-Hoc|Any CPU
 		Ad-Hoc|iPhone = Ad-Hoc|iPhone
@@ -2169,6 +2160,30 @@ Global
 		{A0D0A6A4-5C72-4ADA-9B27-621C7D94F270}.Release|iPhone.Build.0 = Release|Any CPU
 		{A0D0A6A4-5C72-4ADA-9B27-621C7D94F270}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
 		{A0D0A6A4-5C72-4ADA-9B27-621C7D94F270}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|Any CPU.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|Any CPU.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|iPhone.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Ad-Hoc|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|Any CPU.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|Any CPU.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|iPhone.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.AppStore|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|iPhone.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|iPhone.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|Any CPU.Build.0 = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|iPhone.ActiveCfg = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|iPhone.Build.0 = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
+		{E8A597F0-2AB5-4BDA-A235-41162DAF53CF}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -2187,11 +2202,9 @@ Global
 		{EFB11458-9CDF-41C0-BE4F-44AF45A4CAB8} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 		{99135EAB-653D-47E4-A378-C96E1278CA44} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 		{3E53A01A-B331-47F3-B828-4A5717E77A24} = {8B6A8209-894F-4BA1-B880-965FD453982C}
-		{E4D9629C-F168-4224-3F51-A5E482FFBC42} = {A689DEF5-D50F-4975-8B72-124C9EB54066}
 		{6417E941-21BC-467B-A771-0DE389353CE6} = {8B6A8209-894F-4BA1-B880-965FD453982C}
 		{8EF392D5-1416-45AA-9956-7CBBC3229E8A} = {C5A00AC3-B34C-4564-9BDD-2DA473EF4D8B}
 		{08B3E6B9-1CD5-443C-9F61-6D49D1C5F162} = {9B9E3891-2366-4253-A952-D08BCEB71098}
-		{3C4C0CB4-0C0F-4450-A37B-148C84FF905F} = {A689DEF5-D50F-4975-8B72-124C9EB54066}
 		{7B92AF71-6287-4693-9DCB-BD5B6E927E23} = {7CF9789C-F1D3-4D0E-90E5-F1DF67A2753F}
 		{FF69B927-C545-49AE-8E16-3D14D621AA12} = {7CF9789C-F1D3-4D0E-90E5-F1DF67A2753F}
 		{4488AD85-1495-4809-9AA4-DDFE0A48527E} = {0CB0B92E-6CFF-4240-80A5-CCAFE75D91E1}

build/CoreLibraries.props

@@ -17,5 +17,6 @@
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Markup/Avalonia.Markup.Xaml/Avalonia.Markup.Xaml.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.MicroCom/Avalonia.MicroCom.csproj" />
       <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.DesktopRuntime/Avalonia.DesktopRuntime.csproj" Condition="'$(TargetFramework)' != 'netstandard2.0'" />
+      <ProjectReference Include="$(MSBuildThisFileDirectory)/../src/Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj" />
   </ItemGroup>
 </Project>

build/SharedVersion.props

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <Product>Avalonia</Product>
     <Version>0.10.999</Version>
-    <Copyright>Copyright 2021 &#169; The AvaloniaUI Project</Copyright>
+    <Copyright>Copyright 2022 &#169; The AvaloniaUI Project</Copyright>
     <PackageProjectUrl>https://avaloniaui.net</PackageProjectUrl>
     <RepositoryUrl>https://github.com/AvaloniaUI/Avalonia/</RepositoryUrl>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>

build/SourceLink.props

@@ -3,7 +3,6 @@
     <PublishRepositoryUrl>true</PublishRepositoryUrl>
     <IncludeSymbols>false</IncludeSymbols>
     <EmbedUntrackedSources>true</EmbedUntrackedSources>
-    <DebugType>embedded</DebugType>
     <AllowedOutputExtensionsInPackageBuildOutputFolder>$(AllowedOutputExtensionsInPackageBuildOutputFolder);.pdb</AllowedOutputExtensionsInPackageBuildOutputFolder>
   </PropertyGroup>
   
@@ -15,6 +14,10 @@
     <ContinuousIntegrationBuild>true</ContinuousIntegrationBuild>
   </PropertyGroup>
   
+  <PropertyGroup>
+    <DebugType Condition="$(ContinuousIntegrationBuild) == 'true'">embedded</DebugType>
+  </PropertyGroup>
+  
   <ItemGroup>
     <PackageReference Include="Microsoft.SourceLink.GitHub" Version="1.0.0" PrivateAssets="All"/>
   </ItemGroup>

native/Avalonia.Native/src/OSX/window.mm

@@ -1627,6 +1627,19 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
             return;
         }
     }
+    else if (type == Magnify)
+    {
+        delta.X = delta.Y = [event magnification];
+    }
+    else if (type == Rotate)
+    {
+        delta.X = delta.Y = [event rotation];
+    }
+    else if (type == Swipe)
+    {
+        delta.X = [event deltaX];
+        delta.Y = [event deltaY];
+    }
     
     auto timestamp = [event timestamp] * 1000;
     auto modifiers = [self getModifiers:[event modifierFlags]];
@@ -1753,6 +1766,24 @@ NSArray* AllLoopModes = [NSArray arrayWithObjects: NSDefaultRunLoopMode, NSEvent
     [super scrollWheel:event];
 }
 
+- (void)magnifyWithEvent:(NSEvent *)event
+{
+    [self mouseEvent:event withType:Magnify];
+    [super magnifyWithEvent:event];
+}
+
+- (void)rotateWithEvent:(NSEvent *)event
+{
+    [self mouseEvent:event withType:Rotate];
+    [super rotateWithEvent:event];
+}
+
+- (void)swipeWithEvent:(NSEvent *)event
+{
+    [self mouseEvent:event withType:Swipe];
+    [super swipeWithEvent:event];
+}
+
 - (void)mouseEntered:(NSEvent *)event
 {
     _isMouseOver = true;

samples/ControlCatalog.Android/Assets/AboutAssets.txt

@@ -1,7 +1,7 @@
 Any raw assets you want to be deployed with your application can be placed in
 this directory (and child directories) and given a Build Action of "AndroidAsset".
 
-These files will be deployed with you package and will be accessible using Android's
+These files will be deployed with your package and will be accessible using Android's
 AssetManager, like this:
 
 public class ReadAsset : Activity
@@ -16,4 +16,4 @@ public class ReadAsset : Activity
 
 Additionally, some Android functions will automatically load asset files:
 
-Typeface tf = Typeface.CreateFromAsset (Context.Assets, "fonts/samplefont.ttf");
+Typeface tf = Typeface.CreateFromAsset (Context.Assets, "fonts/samplefont.ttf");

samples/ControlCatalog.Web/ControlCatalog.Web.csproj

@@ -2,6 +2,7 @@
   <PropertyGroup>
     <TargetFramework>net6.0</TargetFramework>
     <Nullable>enable</Nullable>
+    <WasmBuildNative>True</WasmBuildNative>
   </PropertyGroup>
 
   <ItemGroup>

samples/ControlCatalog/App.xaml

@@ -3,6 +3,7 @@
              xmlns:vm="using:ControlCatalog.ViewModels"
              x:DataType="vm:ApplicationViewModel"
              x:CompileBindings="True"
+             Name="Avalonia ControlCatalog"
              x:Class="ControlCatalog.App">
   <Application.Styles>
     <Style Selector="TextBlock.h1, TextBlock.h2, TextBlock.h3">

samples/ControlCatalog/App.xaml.cs

@@ -5,6 +5,7 @@ using Avalonia.Controls.ApplicationLifetimes;
 using Avalonia.Markup.Xaml;
 using Avalonia.Markup.Xaml.Styling;
 using Avalonia.Styling;
+using Avalonia.Themes.Default;
 using Avalonia.Themes.Fluent;
 using ControlCatalog.ViewModels;
 
@@ -29,6 +30,8 @@ namespace ControlCatalog
 
         public static FluentTheme Fluent = new FluentTheme(new Uri("avares://ControlCatalog/Styles"));
 
+        public static SimpleTheme Default = new SimpleTheme(new Uri("avares://ControlCatalog/Styles"));
+
         public static Styles DefaultLight = new Styles
         {
             new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
@@ -43,14 +46,7 @@ namespace ControlCatalog
             {
                 Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/BaseLight.xaml")
             },
-            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("avares://Avalonia.Themes.Default/Accents/BaseLight.xaml")
-            },
-            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("avares://Avalonia.Themes.Default/DefaultTheme.xaml")
-            }
+            Default
         };
 
         public static Styles DefaultDark = new Styles
@@ -67,14 +63,7 @@ namespace ControlCatalog
             {
                 Source = new Uri("avares://Avalonia.Themes.Fluent/Accents/BaseDark.xaml")
             },
-            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("avares://Avalonia.Themes.Default/Accents/BaseDark.xaml")
-            },
-            new StyleInclude(new Uri("resm:Styles?assembly=ControlCatalog"))
-            {
-                Source = new Uri("avares://Avalonia.Themes.Default/DefaultTheme.xaml")
-            }
+            Default
         };
 
         public override void Initialize()
@@ -89,16 +78,18 @@ namespace ControlCatalog
             if (ApplicationLifetime is IClassicDesktopStyleApplicationLifetime desktopLifetime)
             {
                 desktopLifetime.MainWindow = new MainWindow();
+
+                this.AttachDevTools(new Avalonia.Diagnostics.DevToolsOptions()
+                {
+                    StartupScreenIndex = 1,
+                });
             }
             else if (ApplicationLifetime is ISingleViewApplicationLifetime singleViewLifetime)
+            {
                 singleViewLifetime.MainView = new MainView();
+            }
 
             base.OnFrameworkInitializationCompleted();
-
-            this.AttachDevTools(new Avalonia.Diagnostics.DevToolsOptions()
-            {
-                StartupScreenIndex = 1,
-            });
         }
     }
 }

samples/ControlCatalog/MainView.xaml.cs

@@ -63,11 +63,13 @@ namespace ControlCatalog
                     }
                     else if (theme == CatalogTheme.DefaultLight)
                     {
+                        App.Default.Mode = Avalonia.Themes.Default.SimpleThemeMode.Light;
                         Application.Current.Styles[0] = App.DefaultLight;
                         Application.Current.Styles[1] = App.DataGridDefault;
                     }
                     else if (theme == CatalogTheme.DefaultDark)
                     {
+                        App.Default.Mode = Avalonia.Themes.Default.SimpleThemeMode.Dark;
                         Application.Current.Styles[0] = App.DefaultDark;
                         Application.Current.Styles[1] = App.DataGridDefault;
                     }

samples/ControlCatalog/Models/Person.cs

@@ -16,6 +16,7 @@ namespace ControlCatalog.Models
         string _firstName;
         string _lastName;
         bool _isBanned;
+        private int _age;
 
         public string FirstName
         {
@@ -59,6 +60,20 @@ namespace ControlCatalog.Models
             }
         }
 
+        
+        /// <summary>
+        ///    Gets or sets the age of the person
+        /// </summary>
+        public int Age
+        {
+            get => _age;
+            set
+            {
+                _age = value;
+                OnPropertyChanged(nameof(Age));
+            }
+        }
+
         Dictionary<string, List<string>> _errorLookup = new Dictionary<string, List<string>>();
 
         void SetError(string propertyName, string error)

samples/ControlCatalog/Pages/CalendarDatePickerPage.xaml

@@ -1,5 +1,7 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:vm="clr-namespace:ControlCatalog.ViewModels"
+             x:DataType="vm:MainWindowViewModel"
              x:Class="ControlCatalog.Pages.CalendarDatePickerPage">
   <StackPanel Orientation="Vertical" Spacing="4">
     <TextBlock Classes="h2">A control for selecting dates with a calendar drop-down</TextBlock>
@@ -39,6 +41,9 @@
                 
         <TextBlock Text="Disabled"/>
         <CalendarDatePicker IsEnabled="False"/>
+        
+        <TextBlock Text="Validation Example"/>
+        <CalendarDatePicker SelectedDate="{CompiledBinding ValidatedDateExample, Mode=TwoWay}"/>
       </StackPanel>
 
     </StackPanel> 

samples/ControlCatalog/Pages/DataGridPage.xaml

@@ -64,6 +64,18 @@
               <DataGridTextColumn Header="First Name" Binding="{Binding FirstName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridTextColumn Header="Last" Binding="{Binding LastName}" Width="2*" FontSize="{Binding #FontSizeSlider.Value, Mode=OneWay}" />
               <DataGridCheckBoxColumn Header="Is Banned" Binding="{Binding IsBanned}" Width="*" IsThreeState="{Binding #IsThreeStateCheckBox.IsChecked, Mode=OneWay}" />
+              <DataGridTemplateColumn Header="Age" >
+                <DataGridTemplateColumn.CellTemplate>
+                  <DataTemplate DataType="local:Person">
+                    <TextBlock Text="{Binding Age, StringFormat='{}{0} years'}" VerticalAlignment="Center" HorizontalAlignment="Center" />
+                  </DataTemplate>
+                </DataGridTemplateColumn.CellTemplate>
+                <DataGridTemplateColumn.CellEditingTemplate>
+                  <DataTemplate DataType="local:Person">
+                    <NumericUpDown Value="{Binding Age}" FormatString="N0" HorizontalAlignment="Stretch" Minimum="0" Maximum="120" TemplateApplied="NumericUpDown_OnTemplateApplied" />
+                  </DataTemplate>
+                </DataGridTemplateColumn.CellEditingTemplate>
+              </DataGridTemplateColumn>
             </DataGrid.Columns>
           </DataGrid>
           <Button Grid.Row="1" Name="btnAdd" Margin="12,0,12,12" Content="Add" HorizontalAlignment="Right" />

samples/ControlCatalog/Pages/DataGridPage.xaml.cs

@@ -6,7 +6,9 @@ using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
 using ControlCatalog.Models;
 using Avalonia.Collections;
+using Avalonia.Controls.Primitives;
 using Avalonia.Data;
+using Avalonia.Threading;
 
 namespace ControlCatalog.Pages
 {
@@ -48,9 +50,9 @@ namespace ControlCatalog.Pages
 
             var items = new List<Person>
             {
-                new Person { FirstName = "John", LastName = "Doe" },
-                new Person { FirstName = "Elizabeth", LastName = "Thomas", IsBanned = true },
-                new Person { FirstName = "Zack", LastName = "Ward" }
+                new Person { FirstName = "John", LastName = "Doe" , Age = 30},
+                new Person { FirstName = "Elizabeth", LastName = "Thomas", IsBanned = true , Age = 40 },
+                new Person { FirstName = "Zack", LastName = "Ward" , Age = 50 }
             };
             var collectionView3 = new DataGridCollectionView(items);
 
@@ -84,5 +86,19 @@ namespace ControlCatalog.Pages
                 return Comparer.Default.Compare(x, y);
             }
         }
+
+        private void NumericUpDown_OnTemplateApplied(object sender, TemplateAppliedEventArgs e)
+        {
+            // We want to focus the TextBox of the NumericUpDown. To do so we search for this control when the template
+            // is applied, but we postpone the action until the control is actually loaded. 
+            if (e.NameScope.Find<TextBox>("PART_TextBox") is {} textBox)
+            {
+                Dispatcher.UIThread.InvokeAsync(() =>
+                {
+                    textBox.Focus();
+                    textBox.SelectAll();
+                }, DispatcherPriority.Loaded);
+            }
+        }
     }
 }

samples/ControlCatalog/Pages/PointersPage.cs

@@ -1,15 +1,37 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.Linq;
+using System.Reactive.Linq;
+using System.Runtime.InteropServices;
+using System.Threading;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Input;
+using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Media.Immutable;
+using Avalonia.Threading;
+using Avalonia.VisualTree;
 
-namespace ControlCatalog.Pages
+namespace ControlCatalog.Pages;
+
+public class PointersPage : Decorator
 {
-    public class PointersPage : Control
+    public PointersPage()
+    {
+        Child = new TabControl
+        {
+            Items = new[]
+            {
+                new TabItem() { Header = "Contacts", Content = new PointerContactsTab() },
+                new TabItem() { Header = "IntermediatePoints", Content = new PointerIntermediatePointsTab() }
+            }
+        };
+    }
+    
+    
+    class PointerContactsTab : Control
     {
         class PointerInfo
         {
@@ -45,7 +67,7 @@ namespace ControlCatalog.Pages
         
         private Dictionary<IPointer, PointerInfo> _pointers = new Dictionary<IPointer, PointerInfo>();
 
-        public PointersPage()
+        public PointerContactsTab()
         {
             ClipToBounds = true;
         }
@@ -104,4 +126,196 @@ namespace ControlCatalog.Pages
             }
         }
     }
+
+    public class PointerIntermediatePointsTab : Decorator
+    {
+        public PointerIntermediatePointsTab()
+        {
+            this[TextBlock.ForegroundProperty] = Brushes.Black;
+            var slider = new Slider
+            {
+                Margin = new Thickness(5),
+                Minimum = 0,
+                Maximum = 500
+            };
+
+            var status = new TextBlock()
+            {
+                HorizontalAlignment = HorizontalAlignment.Left,
+                VerticalAlignment = VerticalAlignment.Top,
+            };
+            Child = new Grid
+            {
+                Children =
+                {
+                    new PointerCanvas(slider, status),
+                    new Border
+                    {
+                        Background = Brushes.LightYellow,
+                        Child = new StackPanel
+                        {
+                            Children =
+                            {
+                                new StackPanel
+                                {
+                                    Orientation = Orientation.Horizontal,
+                                    Children =
+                                    {
+                                        new TextBlock { Text = "Thread sleep:" },
+                                        new TextBlock()
+                                        {
+                                            [!TextBlock.TextProperty] =slider.GetObservable(Slider.ValueProperty)
+                                                .Select(x=>x.ToString()).ToBinding()
+                                        }
+                                    }
+                                },
+                                slider
+                            }
+                        },
+
+                        HorizontalAlignment = HorizontalAlignment.Right,
+                        VerticalAlignment = VerticalAlignment.Top,
+                        Width = 300,
+                        Height = 60
+                    },
+                    status
+                }
+            };
+        }
+
+        class PointerCanvas : Control
+        {
+            private readonly Slider _slider;
+            private readonly TextBlock _status;
+            private int _events;
+            private Stopwatch _stopwatch = Stopwatch.StartNew();
+            private Dictionary<int, PointerPoints> _pointers = new();
+            class PointerPoints
+            {
+                struct CanvasPoint
+                {
+                    public IBrush Brush;
+                    public Point Point;
+                    public double Radius;
+                }
+
+                readonly CanvasPoint[] _points = new CanvasPoint[1000];
+                int _index;
+                
+                public  void Render(DrawingContext context)
+                {
+                    
+                    CanvasPoint? prev = null;
+                    for (var c = 0; c < _points.Length; c++)
+                    {
+                        var i = (c + _index) % _points.Length;
+                        var pt = _points[i];
+                        if (prev.HasValue && prev.Value.Brush != null && pt.Brush != null)
+                            context.DrawLine(new Pen(Brushes.Black), prev.Value.Point, pt.Point);
+                        prev = pt;
+                        if (pt.Brush != null)
+                            context.DrawEllipse(pt.Brush, null, pt.Point, pt.Radius, pt.Radius);
+
+                    }
+
+                }
+
+                void AddPoint(Point pt, IBrush brush, double radius)
+                {
+                    _points[_index] = new CanvasPoint { Point = pt, Brush = brush, Radius = radius };
+                    _index = (_index + 1) % _points.Length;
+                }
+
+                public void HandleEvent(PointerEventArgs e, Visual v)
+                {
+                    e.Handled = true;
+                    if (e.RoutedEvent == PointerPressedEvent)
+                        AddPoint(e.GetPosition(v), Brushes.Green, 10);
+                    else if (e.RoutedEvent == PointerReleasedEvent)
+                        AddPoint(e.GetPosition(v), Brushes.Red, 10);
+                    else
+                    {
+                        var pts = e.GetIntermediatePoints(v);
+                        for (var c = 0; c < pts.Count; c++)
+                        {
+                            var pt = pts[c];
+                            AddPoint(pt.Position, c == pts.Count - 1 ? Brushes.Blue : Brushes.Black,
+                                c == pts.Count - 1 ? 5 : 2);
+                        }
+                    }
+                }
+            }
+            
+            public PointerCanvas(Slider slider, TextBlock status)
+            {
+                _slider = slider;
+                _status = status;
+                DispatcherTimer.Run(() =>
+                {
+                    if (_stopwatch.Elapsed.TotalSeconds > 1)
+                    {
+                        _status.Text = "Events per second: " + (_events / _stopwatch.Elapsed.TotalSeconds);
+                        _stopwatch.Restart();
+                        _events = 0;
+                    }
+
+                    return this.GetVisualRoot() != null;
+                }, TimeSpan.FromMilliseconds(10));
+            }
+
+
+            void HandleEvent(PointerEventArgs e)
+            {
+                _events++;
+                Thread.Sleep((int)_slider.Value);
+                InvalidateVisual();
+
+                if (e.RoutedEvent == PointerReleasedEvent && e.Pointer.Type == PointerType.Touch)
+                {
+                    _pointers.Remove(e.Pointer.Id);
+                    return;
+                }
+
+                if (!_pointers.TryGetValue(e.Pointer.Id, out var pt))
+                    _pointers[e.Pointer.Id] = pt = new PointerPoints();
+                pt.HandleEvent(e, this);
+                
+                
+            }
+            
+            public override void Render(DrawingContext context)
+            {
+                context.FillRectangle(Brushes.White, Bounds);
+                foreach(var pt in _pointers.Values)
+                    pt.Render(context);
+                base.Render(context);
+            }
+
+            protected override void OnPointerPressed(PointerPressedEventArgs e)
+            {
+                if (e.ClickCount == 2)
+                {
+                    _pointers.Clear();
+                    InvalidateVisual();
+                    return;
+                }
+                
+                HandleEvent(e);
+                base.OnPointerPressed(e);
+            }
+
+            protected override void OnPointerMoved(PointerEventArgs e)
+            {
+                HandleEvent(e);
+                base.OnPointerMoved(e);
+            }
+
+            protected override void OnPointerReleased(PointerReleasedEventArgs e)
+            {
+                HandleEvent(e);
+                base.OnPointerReleased(e);
+            }
+        }
+    
+    }
 }

samples/ControlCatalog/Pages/ScreenPage.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Globalization;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
@@ -49,25 +50,33 @@ namespace ControlCatalog.Pages
                     context.DrawRectangle(p, boundsRect);
                     context.DrawRectangle(p, workingAreaRect);
 
-                    var text = new FormattedText() { Typeface = new Typeface("Arial"), FontSize = 18 };
 
-                    text.Text = $"Bounds: {screen.Bounds.TopLeft} {screen.Bounds.Width}:{screen.Bounds.Height}";
-                    context.DrawText(drawBrush, boundsRect.Position.WithY(boundsRect.Size.Height), text);
-                    
-                    text.Text = $"WorkArea: {screen.WorkingArea.TopLeft} {screen.WorkingArea.Width}:{screen.WorkingArea.Height}";
-                    context.DrawText(drawBrush, boundsRect.Position.WithY(boundsRect.Size.Height + 20), text);
+                    var formattedText = CreateFormattedText($"Bounds: {screen.Bounds.Width}:{screen.Bounds.Height}");
+                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height));
 
-                    text.Text = $"Scaling: {screen.PixelDensity * 100}%";
-                    context.DrawText(drawBrush, boundsRect.Position.WithY(boundsRect.Size.Height + 40), text);
-                    
-                    text.Text = $"Primary: {screen.Primary}";
-                    context.DrawText(drawBrush, boundsRect.Position.WithY(boundsRect.Size.Height + 60), text);
-                    
-                    text.Text = $"Current: {screen.Equals(w.Screens.ScreenFromBounds(new PixelRect(w.Position, PixelSize.FromSize(w.Bounds.Size, scaling))))}";
-                    context.DrawText(drawBrush, boundsRect.Position.WithY(boundsRect.Size.Height + 80), text);
+                    formattedText =
+                        CreateFormattedText($"WorkArea: {screen.WorkingArea.Width}:{screen.WorkingArea.Height}");
+                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 20));
+
+                    formattedText = CreateFormattedText($"Scaling: {screen.PixelDensity * 100}%");
+                    context.DrawText(formattedText, boundsRect.Position.WithY(boundsRect.Size.Height + 40));
+
+                    formattedText = CreateFormattedText($"Primary: {screen.Primary}");
+                    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));
         }
+
+        private FormattedText CreateFormattedText(string textToFormat)
+        {
+            return new FormattedText(textToFormat, CultureInfo.CurrentCulture, FlowDirection.LeftToRight,
+                Typeface.Default, 12, Brushes.Green);
+        }
     }
 }

samples/ControlCatalog/Pages/ViewboxPage.xaml

@@ -1,5 +1,6 @@
 <UserControl xmlns="https://github.com/avaloniaui"
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:collections="clr-namespace:System.Collections;assembly=netstandard"
              x:Class="ControlCatalog.Pages.ViewboxPage">
 
     <Grid RowDefinitions="Auto,*,*">
@@ -12,8 +13,8 @@
           <Border HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="Orange" Width="200" Height="200">
             <Border VerticalAlignment="Center" HorizontalAlignment="Center" Grid.Column="0" BorderThickness="1" BorderBrush="CornflowerBlue" Width="{Binding #WidthSlider.Value}" Height="{Binding #HeightSlider.Value}" >
               <Viewbox
-                  Stretch="{Binding #StretchSelector.SelectedItem}"
-                  StretchDirection="{Binding #StretchDirectionSelector.SelectedItem}">
+                  Stretch="{Binding #StretchSelector.SelectedItem, FallbackValue={x:Static Stretch.Uniform}}"
+                  StretchDirection="{Binding #StretchDirectionSelector.SelectedItem, FallbackValue={x:Static StretchDirection.Both}}">
                 <Ellipse Width="50" Height="50" Fill="CornflowerBlue" />
               </Viewbox>
             </Border>
@@ -25,9 +26,22 @@
             <TextBlock Text="Height" />
             <Slider Minimum="10" Maximum="200" Value="100" x:Name="HeightSlider" TickFrequency="25" TickPlacement="TopLeft" />
             <TextBlock Text="Stretch" />
-            <ComboBox x:Name="StretchSelector" HorizontalAlignment="Stretch" Margin="0,0,0,2" />
+            <ComboBox x:Name="StretchSelector" HorizontalAlignment="Stretch" SelectedIndex="0" Margin="0,0,0,2">
+              <collections:ArrayList>
+                <Stretch>Uniform</Stretch>
+                <Stretch>UniformToFill</Stretch>
+                <Stretch>Fill</Stretch>
+                <Stretch>None</Stretch>
+              </collections:ArrayList>
+            </ComboBox>
             <TextBlock Text="Stretch Direction" />
-            <ComboBox x:Name="StretchDirectionSelector" HorizontalAlignment="Stretch" />
+            <ComboBox x:Name="StretchDirectionSelector" SelectedIndex="0" HorizontalAlignment="Stretch">
+              <collections:ArrayList>
+                <StretchDirection>Both</StretchDirection>
+                <StretchDirection>DownOnly</StretchDirection>
+                <StretchDirection>UpOnly</StretchDirection>
+              </collections:ArrayList>
+            </ComboBox>
           </StackPanel>
         </Grid>
 

samples/ControlCatalog/Pages/ViewboxPage.xaml.cs

@@ -1,6 +1,5 @@
 using Avalonia.Controls;
 using Avalonia.Markup.Xaml;
-using Avalonia.Media;
 
 namespace ControlCatalog.Pages
 {
@@ -9,24 +8,6 @@ namespace ControlCatalog.Pages
         public ViewboxPage()
         {
             InitializeComponent();
-
-            var stretchSelector = this.FindControl<ComboBox>("StretchSelector");
-
-            stretchSelector.Items = new[]
-            {
-                Stretch.Uniform, Stretch.UniformToFill, Stretch.Fill, Stretch.None
-            };
-
-            stretchSelector.SelectedIndex = 0;
-
-            var stretchDirectionSelector = this.FindControl<ComboBox>("StretchDirectionSelector");
-
-            stretchDirectionSelector.Items = new[]
-            {
-                StretchDirection.Both, StretchDirection.DownOnly, StretchDirection.UpOnly
-            };
-
-            stretchDirectionSelector.SelectedIndex = 0;
         }
 
         private void InitializeComponent()

samples/ControlCatalog/ViewModels/MainWindowViewModel.cs

@@ -5,6 +5,7 @@ using Avalonia.Controls.Notifications;
 using Avalonia.Dialogs;
 using Avalonia.Platform;
 using System;
+using System.ComponentModel.DataAnnotations;
 using MiniMvvm;
 
 namespace ControlCatalog.ViewModels
@@ -164,5 +165,17 @@ namespace ControlCatalog.ViewModels
         public MiniCommand ExitCommand { get; }
 
         public MiniCommand ToggleMenuItemCheckedCommand { get; }
+
+        private DateTime? _validatedDateExample;
+
+        /// <summary>
+        ///    A required DateTime which should demonstrate validation for the DateTimePicker
+        /// </summary>
+        [Required]
+        public DateTime? ValidatedDateExample
+        {
+            get => _validatedDateExample;
+            set => this.RaiseAndSetIfChanged(ref _validatedDateExample, value);
+        }
     }
 }

samples/RenderDemo/MainWindow.xaml

@@ -57,6 +57,9 @@
     <TabItem Header="GlyphRun">
       <pages:GlyphRunPage />
     </TabItem>
+    <TabItem Header="FormattedText">
+      <pages:FormattedTextPage />
+    </TabItem>
     <TabItem Header="LineBounds">
       <pages:LineBoundsPage />
     </TabItem>

samples/RenderDemo/Pages/ClippingPage.xaml

@@ -19,30 +19,36 @@
         </Style>
       </Styles>
     </Grid.Styles>
-    <Border Name="clipped" 
-            Background="Yellow" 
-            Width="100" 
-            Height="100" 
-            Clip="M 58.625 0.07421875
-                  C 50.305778 0.26687364 42.411858 7.0346526 41.806641 15.595703
-                  C 42.446442 22.063923 39.707425 13.710754 36.982422 12.683594
-                  C 29.348395 6.1821635 16.419398 8.4359222 11.480469 17.195312
-                  C 6.0935256 25.476803 9.8118851 37.71125 18.8125 41.6875
-                  C 9.1554771 40.62945 -0.070876925 49.146842 0.21679688 58.857422 
-                  C 0.21545578 60.872512 0.56758794 62.88911 1.2617188 64.78125 
-                  C 4.3821886 74.16708 16.298268 78.921772 25.03125 74.326172 
-                  C 28.266843 72.062552 26.298191 74.214838 25.414062 76.398438
-                  C 21.407348 85.589198 27.295992 97.294293 37.097656 99.501953 
-                  C 46.864883 102.3541 57.82177 94.726518 58.539062 84.580078 
-                  C 58.142158 79.498998 59.307538 83.392694 61.207031 85.433594 
-                  C 67.532324 93.056874 80.440232 93.192029 86.882812 85.630859 
-                  C 93.836392 78.456939 92.396838 65.538666 84.115234 60.009766 
-                  C 79.783641 57.904836 83.569793 58.802369 86.375 58.193359 
-                  C 96.383335 56.457569 102.87506 44.824101 99.083984 35.394531 
-                  C 95.963498 26.008711 84.047451 21.254079 75.314453 25.849609
-                  C 72.078834 28.113269 74.047517 25.960974 74.931641 23.777344 
-                  C 78.93827 14.586564 73.049722 2.8815081 63.248047 0.67382812
-                  C 61.721916 0.22817968 60.165597 0.038541919 58.625 0.07421875 z ">
+    <Border Name="clipped"
+            Background="Yellow"
+            Width="100"
+            Height="100"
+            Classes.clip="{Binding #useMask.IsChecked}">
+      <Border.Styles>
+        <Style Selector="Border.clip">
+          <Setter Property="Clip" 
+                  Value="M 58.625 0.07421875
+                         C 50.305778 0.26687364 42.411858 7.0346526 41.806641 15.595703
+                         C 42.446442 22.063923 39.707425 13.710754 36.982422 12.683594
+                         C 29.348395 6.1821635 16.419398 8.4359222 11.480469 17.195312
+                         C 6.0935256 25.476803 9.8118851 37.71125 18.8125 41.6875
+                         C 9.1554771 40.62945 -0.070876925 49.146842 0.21679688 58.857422 
+                         C 0.21545578 60.872512 0.56758794 62.88911 1.2617188 64.78125 
+                         C 4.3821886 74.16708 16.298268 78.921772 25.03125 74.326172 
+                         C 28.266843 72.062552 26.298191 74.214838 25.414062 76.398438
+                         C 21.407348 85.589198 27.295992 97.294293 37.097656 99.501953 
+                         C 46.864883 102.3541 57.82177 94.726518 58.539062 84.580078 
+                         C 58.142158 79.498998 59.307538 83.392694 61.207031 85.433594 
+                         C 67.532324 93.056874 80.440232 93.192029 86.882812 85.630859 
+                         C 93.836392 78.456939 92.396838 65.538666 84.115234 60.009766 
+                         C 79.783641 57.904836 83.569793 58.802369 86.375 58.193359 
+                         C 96.383335 56.457569 102.87506 44.824101 99.083984 35.394531 
+                         C 95.963498 26.008711 84.047451 21.254079 75.314453 25.849609
+                         C 72.078834 28.113269 74.047517 25.960974 74.931641 23.777344 
+                         C 78.93827 14.586564 73.049722 2.8815081 63.248047 0.67382812
+                         C 61.721916 0.22817968 60.165597 0.038541919 58.625 0.07421875 z " />
+        </Style>
+      </Border.Styles>
       <Border Name="clipChild" Background="Red" Margin="4">
         <!-- Setting opacity puts the TextBox on a new layer -->
         <TextBox Text="Avalonia" Opacity="0.9" VerticalAlignment="Center"/>

samples/RenderDemo/Pages/ClippingPage.xaml.cs

@@ -1,35 +1,18 @@
-using System;
-using System.Reactive.Linq;
-using Avalonia;
-using Avalonia.Animation;
 using Avalonia.Controls;
-using Avalonia.Data;
 using Avalonia.Markup.Xaml;
-using Avalonia.Media;
 
 namespace RenderDemo.Pages
 {
     public class ClippingPage : UserControl
     {
-        private Geometry _clip;
-
         public ClippingPage()
         {
             InitializeComponent();
-            WireUpCheckbox();
         }
 
         private void InitializeComponent()
         {
             AvaloniaXamlLoader.Load(this);
         }
-
-        private void WireUpCheckbox()
-        {
-            var useMask = this.FindControl<CheckBox>("useMask");
-            var clipped = this.FindControl<Border>("clipped");
-            _clip = clipped.Clip;
-            useMask.Click += (s, e) => clipped.Clip = clipped.Clip == null ? _clip : null;
-        }
     }
 }

samples/RenderDemo/Pages/CustomSkiaPage.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Diagnostics;
+using System.Globalization;
 using Avalonia;
 using Avalonia.Controls;
 using Avalonia.Media;
@@ -41,7 +42,10 @@ namespace RenderDemo.Pages
             {
                 var canvas = (context as ISkiaDrawingContextImpl)?.SkCanvas;
                 if (canvas == null)
-                    context.DrawText(Brushes.Black, new Point(), _noSkia.PlatformImpl);
+                    using (var c = new DrawingContext(context, false))
+                    {
+                        c.DrawText(_noSkia, new Point());
+                    }
                 else
                 {
                     canvas.Save();
@@ -108,10 +112,9 @@ namespace RenderDemo.Pages
         
         public override void Render(DrawingContext context)
         {
-            var noSkia = new FormattedText()
-            {
-                Text = "Current rendering API is not Skia"
-            };
+            var noSkia = new FormattedText("Current rendering API is not Skia", CultureInfo.CurrentCulture,
+                FlowDirection.LeftToRight, Typeface.Default, 12, Brushes.Black);
+
             context.Custom(new CustomDrawOp(new Rect(0, 0, Bounds.Width, Bounds.Height), noSkia));
             Dispatcher.UIThread.InvokeAsync(InvalidateVisual, DispatcherPriority.Background);
         }

samples/RenderDemo/Pages/FormattedTextPage.axaml

@@ -0,0 +1,7 @@
+<UserControl xmlns="https://github.com/avaloniaui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+             mc:Ignorable="d" d:DesignWidth="800" d:DesignHeight="450"
+             x:Class="RenderDemo.Pages.FormattedTextPage">
+</UserControl>

samples/RenderDemo/Pages/FormattedTextPage.axaml.cs

@@ -0,0 +1,60 @@
+using System.Globalization;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Markup.Xaml;
+using Avalonia.Media;
+
+namespace RenderDemo.Pages
+{
+    public class FormattedTextPage : UserControl
+    {
+        public FormattedTextPage()
+        {
+            this.InitializeComponent();
+        }
+
+        private void InitializeComponent()
+        {
+            AvaloniaXamlLoader.Load(this);
+        }
+
+        public override void Render(DrawingContext context)
+        {
+            const string testString = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor";
+
+            // Create the initial formatted text string.
+            var formattedText = new FormattedText(
+                testString,
+                CultureInfo.GetCultureInfo("en-us"),
+                FlowDirection.LeftToRight,
+                new Typeface("Verdana"),
+                32,
+                Brushes.Black) { MaxTextWidth = 300, MaxTextHeight = 240 };
+
+            // Set a maximum width and height. If the text overflows these values, an ellipsis "..." appears.
+
+            // Use a larger font size beginning at the first (zero-based) character and continuing for 5 characters.
+            // The font size is calculated in terms of points -- not as device-independent pixels.
+            formattedText.SetFontSize(36 * (96.0 / 72.0), 0, 5);
+
+            // Use a Bold font weight beginning at the 6th character and continuing for 11 characters.
+            formattedText.SetFontWeight(FontWeight.Bold, 6, 11);
+
+            var gradient = new LinearGradientBrush
+            {
+                GradientStops =
+                    new GradientStops { new GradientStop(Colors.Orange, 0), new GradientStop(Colors.Teal, 1) },
+                StartPoint = new RelativePoint(0,0, RelativeUnit.Relative),
+                EndPoint = new RelativePoint(0,1, RelativeUnit.Relative)
+            };
+
+            // Use a linear gradient brush beginning at the 6th character and continuing for 11 characters.
+            formattedText.SetForegroundBrush(gradient, 6, 11);
+
+            // Use an Italic font style beginning at the 28th character and continuing for 28 characters.
+            formattedText.SetFontStyle(FontStyle.Italic, 28, 28);
+
+            context.DrawText(formattedText, new Point(10, 0));
+        }
+    }
+}

samples/RenderDemo/Pages/GlyphRunPage.xaml.cs

@@ -13,6 +13,7 @@ namespace RenderDemo.Pages
         private GlyphTypeface _glyphTypeface = Typeface.Default.GlyphTypeface;
         private readonly Random _rand = new Random();
         private ushort[] _glyphIndices = new ushort[1];
+        private char[] _characters = new char[1];
         private float _fontSize = 20;
         private int _direction = 10;
 
@@ -38,7 +39,7 @@ namespace RenderDemo.Pages
 
         private void UpdateGlyphRun()
         {
-            var c = (uint)_rand.Next(65, 90);
+            var c = (char)_rand.Next(65, 90);
 
             if (_fontSize + _direction > 200)
             {
@@ -54,6 +55,8 @@ namespace RenderDemo.Pages
 
             _glyphIndices[0] = _glyphTypeface.GetGlyph(c);
 
+            _characters[0] = c;
+
             var scale = (double)_fontSize / _glyphTypeface.DesignEmHeight;
 
             var drawingGroup = new DrawingGroup();
@@ -61,7 +64,7 @@ namespace RenderDemo.Pages
             var glyphRunDrawing = new GlyphRunDrawing
             {
                 Foreground = Brushes.Black,
-                GlyphRun = new GlyphRun(_glyphTypeface, _fontSize, _glyphIndices),
+                GlyphRun = new GlyphRun(_glyphTypeface, _fontSize, _characters, _glyphIndices)
             };
 
             drawingGroup.Children.Add(glyphRunDrawing);

src/Android/Avalonia.Android/AndroidPlatform.cs

@@ -10,7 +10,7 @@ using Avalonia.Input.Platform;
 using Avalonia.OpenGL.Egl;
 using Avalonia.Platform;
 using Avalonia.Rendering;
-using Avalonia.Shared.PlatformSupport;
+using Avalonia.PlatformSupport;
 using Avalonia.Skia;
 
 namespace Avalonia
@@ -59,8 +59,7 @@ namespace Avalonia.Android
                 .Bind<IPlatformIconLoader>().ToSingleton<PlatformIconLoaderStub>()
                 .Bind<IRenderTimer>().ToConstant(new ChoreographerTimer())
                 .Bind<IRenderLoop>().ToConstant(new RenderLoop())
-                .Bind<PlatformHotkeyConfiguration>().ToSingleton<PlatformHotkeyConfiguration>()
-                .Bind<IAssetLoader>().ToConstant(new AssetLoader(appType.Assembly));
+                .Bind<PlatformHotkeyConfiguration>().ToSingleton<PlatformHotkeyConfiguration>();
 
             SkiaPlatform.Initialize();
 

src/Android/Avalonia.Android/AppBuilder.cs

@@ -1,5 +1,5 @@
 using Avalonia.Controls;
-using Avalonia.Shared.PlatformSupport;
+using Avalonia.PlatformSupport;
 
 namespace Avalonia
 {

src/Android/Avalonia.Android/Avalonia.Android.csproj

@@ -5,9 +5,11 @@
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\..\..\packages\Avalonia\Avalonia.csproj" />
+    <ProjectReference Include="..\..\Avalonia.PlatformSupport\Avalonia.PlatformSupport.csproj">
+      <SetTargetFramework>TargetFramework=netstandard2.0</SetTargetFramework>
+    </ProjectReference>
     <ProjectReference Include="..\..\Skia\Avalonia.Skia\Avalonia.Skia.csproj" />
   </ItemGroup>
-  <Import Project="..\..\Shared\PlatformSupport\PlatformSupport.projitems" Label="Shared" />
   <Import Project="..\..\..\build\Rx.props" />
   <Import Project="..\..\..\build\AndroidWorkarounds.props" />
 </Project>

src/Android/Avalonia.Android/RuntimeInfo.cs

@@ -1,18 +0,0 @@
-using Avalonia.Platform;
-
-namespace Avalonia.Shared.PlatformSupport
-{
-    internal partial class StandardRuntimePlatform
-    {
-        public RuntimePlatformInfo GetRuntimeInfo() => new RuntimePlatformInfo
-        {
-            IsCoreClr = false,
-            IsDesktop = false,
-            IsMobile = true,
-            IsDotNetFramework = false,
-            IsMono = true,
-            IsUnix = true,
-            OperatingSystem = OperatingSystemType.Android
-        };
-    }
-}

src/Avalonia.Animation/Animatable.cs

@@ -157,7 +157,7 @@ namespace Avalonia.Animation
                             state.Instance?.Dispose();
                             state.Instance = transition.Apply(
                                 this,
-                                Clock ?? AvaloniaLocator.Current.GetService<IGlobalClock>(),
+                                Clock ?? AvaloniaLocator.Current.GetRequiredService<IGlobalClock>(),
                                 oldValue,
                                 newValue);
                             return;
@@ -169,7 +169,7 @@ namespace Avalonia.Animation
             base.OnPropertyChangedCore(change);
         }
 
-        private void TransitionsCollectionChanged(object sender, NotifyCollectionChangedEventArgs e)
+        private void TransitionsCollectionChanged(object? sender, NotifyCollectionChangedEventArgs e)
         {
             if (!_transitionsEnabled)
             {
@@ -179,14 +179,14 @@ namespace Avalonia.Animation
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
-                    AddTransitions(e.NewItems);
+                    AddTransitions(e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Remove:
-                    RemoveTransitions(e.OldItems);
+                    RemoveTransitions(e.OldItems!);
                     break;
                 case NotifyCollectionChangedAction.Replace:
-                    RemoveTransitions(e.OldItems);
-                    AddTransitions(e.NewItems);
+                    RemoveTransitions(e.OldItems!);
+                    AddTransitions(e.NewItems!);
                     break;
                 case NotifyCollectionChangedAction.Reset:
                     throw new NotSupportedException("Transitions collection cannot be reset.");
@@ -204,7 +204,7 @@ namespace Avalonia.Animation
 
             for (var i = 0; i < items.Count; ++i)
             {
-                var t = (ITransition)items[i];
+                var t = (ITransition)items[i]!;
 
                 _transitionState.Add(t, new TransitionState
                 {
@@ -222,7 +222,7 @@ namespace Avalonia.Animation
 
             for (var i = 0; i < items.Count; ++i)
             {
-                var t = (ITransition)items[i];
+                var t = (ITransition)items[i]!;
 
                 if (_transitionState.TryGetValue(t, out var state))
                 {

src/Avalonia.Animation/Animation.cs

@@ -203,7 +203,7 @@ namespace Avalonia.Animation
         /// </summary>
         /// <param name="setter">The animation setter.</param>
         /// <returns>The property animator type.</returns>
-        public static Type GetAnimator(IAnimationSetter setter)
+        public static Type? GetAnimator(IAnimationSetter setter)
         {
             if (s_animators.TryGetValue(setter, out var type))
             {
@@ -254,7 +254,7 @@ namespace Avalonia.Animation
             Animators.Insert(0, (condition, typeof(TAnimator)));
         }
 
-        private static Type GetAnimatorType(AvaloniaProperty property)
+        private static Type? GetAnimatorType(AvaloniaProperty property)
         {
             foreach (var (condition, type) in Animators)
             {
@@ -276,6 +276,11 @@ namespace Avalonia.Animation
             {
                 foreach (var setter in keyframe.Setters)
                 {
+                    if (setter.Property is null)
+                    {
+                        throw new InvalidOperationException("No Setter property assigned.");
+                    }
+
                     var handler = Animation.GetAnimator(setter) ?? GetAnimatorType(setter.Property);
 
                     if (handler == null)
@@ -305,7 +310,7 @@ namespace Avalonia.Animation
 
             foreach (var (handlerType, property) in handlerList)
             {
-                var newInstance = (IAnimator)Activator.CreateInstance(handlerType);
+                var newInstance = (IAnimator)Activator.CreateInstance(handlerType)!;
                 newInstance.Property = property;
                 newAnimatorInstances.Add(newInstance);
             }
@@ -321,32 +326,43 @@ namespace Avalonia.Animation
         }
 
         /// <inheritdoc/>
-        public IDisposable Apply(Animatable control, IClock clock, IObservable<bool> match, Action onComplete)
+        public IDisposable Apply(Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete)
         {
             var (animators, subscriptions) = InterpretKeyframes(control);
             if (animators.Count == 1)
             {
-                subscriptions.Add(animators[0].Apply(this, control, clock, match, onComplete));
+                var subscription = animators[0].Apply(this, control, clock, match, onComplete);
+                
+                if (subscription is not null)
+                {
+                    subscriptions.Add(subscription);
+                }
             }
             else
             {
                 var completionTasks = onComplete != null ? new List<Task>() : null;
                 foreach (IAnimator animator in animators)
                 {
-                    Action animatorOnComplete = null;
+                    Action? animatorOnComplete = null;
                     if (onComplete != null)
                     {
-                        var tcs = new TaskCompletionSource<object>();
+                        var tcs = new TaskCompletionSource<object?>();
                         animatorOnComplete = () => tcs.SetResult(null);
-                        completionTasks.Add(tcs.Task);
+                        completionTasks!.Add(tcs.Task);
+                    }
+
+                    var subscription = animator.Apply(this, control, clock, match, animatorOnComplete);
+
+                    if (subscription is not null)
+                    {
+                        subscriptions.Add(subscription);
                     }
-                    subscriptions.Add(animator.Apply(this, control, clock, match, animatorOnComplete));
                 }
 
                 if (onComplete != null)
                 {
-                    Task.WhenAll(completionTasks).ContinueWith(
-                        (_, state) => ((Action)state).Invoke(),
+                    Task.WhenAll(completionTasks!).ContinueWith(
+                        (_, state) => ((Action)state!).Invoke(),
                         onComplete);
                 }
             }
@@ -354,25 +370,25 @@ namespace Avalonia.Animation
         }
 
         /// <inheritdoc/>
-        public Task RunAsync(Animatable control, IClock clock = null)
+        public Task RunAsync(Animatable control, IClock? clock = null)
         {
             return RunAsync(control, clock, default);
         }
 
         /// <inheritdoc/>
-        public Task RunAsync(Animatable control, IClock clock = null, CancellationToken cancellationToken = default)
+        public Task RunAsync(Animatable control, IClock? clock = null, CancellationToken cancellationToken = default)
         {
             if (cancellationToken.IsCancellationRequested)
             {
                 return Task.CompletedTask;
             }
 
-            var run = new TaskCompletionSource<object>();
+            var run = new TaskCompletionSource<object?>();
 
             if (this.IterationCount == IterationCount.Infinite)
                 run.SetException(new InvalidOperationException("Looping animations must not use the Run method."));
 
-            IDisposable subscriptions = null, cancellation = null;
+            IDisposable? subscriptions = null, cancellation = null;
             subscriptions = this.Apply(control, clock, Observable.Return(true), () =>
             {
                 run.TrySetResult(null);

src/Avalonia.Animation/AnimationInstance`1.cs

@@ -31,15 +31,15 @@ namespace Avalonia.Animation
         private TimeSpan _initialDelay;
         private TimeSpan _iterationDelay;
         private TimeSpan _duration;
-        private Easings.Easing _easeFunc;
-        private Action _onCompleteAction;
+        private Easings.Easing? _easeFunc;
+        private Action? _onCompleteAction;
         private Func<double, T, T> _interpolator;
-        private IDisposable _timerSub;
+        private IDisposable? _timerSub;
         private readonly IClock _baseClock;
-        private IClock _clock;
-        private EventHandler<AvaloniaPropertyChangedEventArgs> _propertyChangedDelegate;
+        private IClock? _clock;
+        private EventHandler<AvaloniaPropertyChangedEventArgs>? _propertyChangedDelegate;
 
-        public AnimationInstance(Animation animation, Animatable control, Animator<T> animator, IClock baseClock, Action OnComplete, Func<double, T, T> Interpolator)
+        public AnimationInstance(Animation animation, Animatable control, Animator<T> animator, IClock baseClock, Action? OnComplete, Func<double, T, T> Interpolator)
         {
             _animator = animator;
             _animation = animation;
@@ -47,6 +47,9 @@ namespace Avalonia.Animation
             _onCompleteAction = OnComplete;
             _interpolator = Interpolator;
             _baseClock = baseClock;
+            _lastInterpValue = default!;
+            _firstKFValue = default!;
+            _neutralValue = default!;
             FetchProperties();
         }
 
@@ -82,7 +85,7 @@ namespace Avalonia.Animation
 
             _targetControl.PropertyChanged -= _propertyChangedDelegate;
             _timerSub?.Dispose();
-            _clock.PlayState = PlayState.Stop;
+            _clock!.PlayState = PlayState.Stop;
         }
 
         protected override void Subscribed()
@@ -108,6 +111,8 @@ namespace Avalonia.Animation
 
         private void ApplyFinalFill()
         {
+            if (_animator.Property is null)
+                throw new InvalidOperationException("Animator has no property specified.");
             if (_fillMode == FillMode.Forward || _fillMode == FillMode.Both)
                 _targetControl.SetValue(_animator.Property, _lastInterpValue, BindingPriority.LocalValue);
         }
@@ -130,12 +135,12 @@ namespace Avalonia.Animation
 
         private void DoPlayStates()
         {
-            if (_clock.PlayState == PlayState.Stop || _baseClock.PlayState == PlayState.Stop)
+            if (_clock!.PlayState == PlayState.Stop || _baseClock.PlayState == PlayState.Stop)
                 DoComplete();
 
             if (!_gotFirstKFValue)
             {
-                _firstKFValue = (T)_animator.First().Value;
+                _firstKFValue = (T)_animator.First().Value!;
                 _gotFirstKFValue = true;
             }
         }
@@ -169,7 +174,7 @@ namespace Avalonia.Animation
                 // and snap the last iteration value to exact values.
                 if ((_currentIteration + 1) > _iterationCount)
                 {
-                    var easedTime = _easeFunc.Ease(_playbackReversed ? 0.0 : 1.0);
+                    var easedTime = _easeFunc!.Ease(_playbackReversed ? 0.0 : 1.0);
                     _lastInterpValue = _interpolator(easedTime, _neutralValue);
                     DoComplete();
                 }
@@ -203,7 +208,7 @@ namespace Avalonia.Animation
                         normalizedTime = 1 - normalizedTime;
 
                     // Ease and interpolate
-                    var easedTime = _easeFunc.Ease(normalizedTime);
+                    var easedTime = _easeFunc!.Ease(normalizedTime);
                     _lastInterpValue = _interpolator(easedTime, _neutralValue);
 
                     PublishNext(_lastInterpValue);
@@ -223,14 +228,14 @@ namespace Avalonia.Animation
 
         private void UpdateNeutralValue()
         {
-            var property = _animator.Property;
+            var property = _animator.Property ?? throw new InvalidOperationException("Animator has no property specified.");
             var baseValue = _targetControl.GetBaseValue(property, BindingPriority.LocalValue);
 
             _neutralValue = baseValue != AvaloniaProperty.UnsetValue ?
-                (T)baseValue : (T)_targetControl.GetValue(property);
+                (T)baseValue! : (T)_targetControl.GetValue(property)!;
         }
 
-        private void ControlPropertyChanged(object sender, AvaloniaPropertyChangedEventArgs e)
+        private void ControlPropertyChanged(object? sender, AvaloniaPropertyChangedEventArgs e)
         {
             if (e.Property == _animator.Property && e.Priority > BindingPriority.Animation)
             {

src/Avalonia.Animation/AnimatorKeyFrame.cs

@@ -12,22 +12,22 @@ namespace Avalonia.Animation
     /// </summary>
     public class AnimatorKeyFrame : AvaloniaObject
     {
-        public static readonly DirectProperty<AnimatorKeyFrame, object> ValueProperty =
-            AvaloniaProperty.RegisterDirect<AnimatorKeyFrame, object>(nameof(Value), k => k.Value, (k, v) => k.Value = v);
+        public static readonly DirectProperty<AnimatorKeyFrame, object?> ValueProperty =
+            AvaloniaProperty.RegisterDirect<AnimatorKeyFrame, object?>(nameof(Value), k => k.Value, (k, v) => k.Value = v);
 
         public AnimatorKeyFrame()
         {
 
         }
 
-        public AnimatorKeyFrame(Type animatorType, Cue cue)
+        public AnimatorKeyFrame(Type? animatorType, Cue cue)
         {
             AnimatorType = animatorType;
             Cue = cue;
             KeySpline = null;
         }
 
-        public AnimatorKeyFrame(Type animatorType, Cue cue, KeySpline keySpline)
+        public AnimatorKeyFrame(Type? animatorType, Cue cue, KeySpline? keySpline)
         {
             AnimatorType = animatorType;
             Cue = cue;
@@ -35,14 +35,14 @@ namespace Avalonia.Animation
         }
 
         internal bool isNeutral;
-        public Type AnimatorType { get; }
+        public Type? AnimatorType { get; }
         public Cue Cue { get; }
-        public KeySpline KeySpline { get; }
-        public AvaloniaProperty Property { get; private set; }
+        public KeySpline? KeySpline { get; }
+        public AvaloniaProperty? Property { get; private set; }
 
-        private object _value;
+        private object? _value;
 
-        public object Value
+        public object? Value
         {
             get => _value;
             set => SetAndRaise(ValueProperty, ref _value, value);
@@ -80,7 +80,7 @@ namespace Avalonia.Animation
                 throw new InvalidCastException($"KeyFrame value doesnt match property type.");
             }
 
-            return (T)typeConv.ConvertTo(Value, typeof(T));
+            return (T)typeConv.ConvertTo(Value, typeof(T))!;
         }
     }
 }

src/Avalonia.Animation/Animators/Animator`1.cs

@@ -24,7 +24,7 @@ namespace Avalonia.Animation.Animators
         /// <summary>
         /// Gets or sets the target property for the keyframe.
         /// </summary>
-        public AvaloniaProperty Property { get; set; }
+        public AvaloniaProperty? Property { get; set; }
 
         public Animator()
         {
@@ -33,7 +33,7 @@ namespace Avalonia.Animation.Animators
         }
 
         /// <inheritdoc/>
-        public virtual IDisposable Apply(Animation animation, Animatable control, IClock clock, IObservable<bool> match, Action onComplete)
+        public virtual IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete)
         {
             if (!_isVerifiedAndConverted)
                 VerifyConvertKeyFrames();
@@ -106,13 +106,16 @@ namespace Avalonia.Animation.Animators
 
         public virtual IDisposable BindAnimation(Animatable control, IObservable<T> instance)
         {
+            if (Property is null)
+                throw new InvalidOperationException("Animator has no property specified.");
+
             return control.Bind((AvaloniaProperty<T>)Property, instance, BindingPriority.Animation);
         }
 
         /// <summary>
         /// Runs the KeyFrames Animation.
         /// </summary>
-        internal IDisposable Run(Animation animation, Animatable control, IClock clock, Action onComplete)
+        internal IDisposable Run(Animation animation, Animatable control, IClock? clock, Action? onComplete)
         {
             var instance = new AnimationInstance<T>(
                 animation,

src/Avalonia.Animation/Avalonia.Animation.csproj

@@ -2,9 +2,13 @@
   <PropertyGroup>
     <TargetFrameworks>net6.0;netstandard2.0</TargetFrameworks>
   </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="..\Avalonia.Base\Metadata\NullableAttributes.cs" Link="NullableAttributes.cs" />
+  </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\Avalonia.Base\Avalonia.Base.csproj" />
   </ItemGroup>
   <Import Project="..\..\build\Rx.props" />
   <Import Project="..\..\build\ApiDiff.props" />
+  <Import Project="..\..\build\NullableEnable.props" />
 </Project>

src/Avalonia.Animation/Clock.cs

@@ -4,7 +4,7 @@ namespace Avalonia.Animation
 {
     public class Clock : ClockBase
     {
-        public static IClock GlobalClock => AvaloniaLocator.Current.GetService<IGlobalClock>();
+        public static IClock GlobalClock => AvaloniaLocator.Current.GetRequiredService<IGlobalClock>();
 
         private readonly IDisposable _parentSubscription;
 

src/Avalonia.Animation/Cue.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Animation
         /// <summary>
         /// Parses a string to a <see cref="Cue"/> object.
         /// </summary>
-        public static Cue Parse(string value, CultureInfo culture)
+        public static Cue Parse(string value, CultureInfo? culture)
         {
             string v = value;
 
@@ -72,14 +72,14 @@ namespace Avalonia.Animation
 
     public class CueTypeConverter : TypeConverter
     {
-        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
         {
             return sourceType == typeof(string);
         }
 
-        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
         {
             return Cue.Parse((string)value, culture);
         }
     }
-}
+}

src/Avalonia.Animation/DisposeAnimationInstanceSubject.cs

@@ -8,15 +8,15 @@ namespace Avalonia.Animation
     /// </summary>
     internal class DisposeAnimationInstanceSubject<T> : IObserver<bool>, IDisposable
     {
-        private IDisposable _lastInstance;
+        private IDisposable? _lastInstance;
         private bool _lastMatch;
         private Animator<T> _animator;
         private Animation _animation;
         private Animatable _control;
-        private Action _onComplete;
-        private IClock _clock;
+        private Action? _onComplete;
+        private IClock? _clock;
 
-        public DisposeAnimationInstanceSubject(Animator<T> animator, Animation animation, Animatable control, IClock clock, Action onComplete)
+        public DisposeAnimationInstanceSubject(Animator<T> animator, Animation animation, Animatable control, IClock? clock, Action? onComplete)
         {
             this._animator = animator;
             this._animation = animation;

src/Avalonia.Animation/Easing/Easing.cs

@@ -15,7 +15,7 @@ namespace Avalonia.Animation.Easings
         /// <inheritdoc/>
         public abstract double Ease(double progress);
 
-        static Dictionary<string, Type> _easingTypes;
+        static Dictionary<string, Type>? _easingTypes;
 
         static readonly Type s_thisType = typeof(Easing);
 
@@ -48,7 +48,7 @@ namespace Avalonia.Animation.Easings
             if (_easingTypes.ContainsKey(e))
             {
                 var type = _easingTypes[e];
-                return (Easing)Activator.CreateInstance(type);
+                return (Easing)Activator.CreateInstance(type)!;
             }
             else
             {

src/Avalonia.Animation/Easing/EasingTypeConverter.cs

@@ -6,12 +6,12 @@ namespace Avalonia.Animation.Easings
 {
     public class EasingTypeConverter : TypeConverter
     {
-        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
         {
             return sourceType == typeof(string);
         }
 
-        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
         {
             return Easing.Parse((string)value);
         }

src/Avalonia.Animation/IAnimation.cs

@@ -12,7 +12,7 @@ namespace Avalonia.Animation
         /// <summary>
         /// Apply the animation to the specified control and run it when <paramref name="match" /> produces <c>true</c>.
         /// </summary>
-        IDisposable Apply(Animatable control, IClock clock, IObservable<bool> match, Action onComplete = null);
+        IDisposable Apply(Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete = null);
 
         /// <summary>
         /// Run the animation on the specified control.

src/Avalonia.Animation/IAnimationSetter.cs

@@ -2,7 +2,7 @@ namespace Avalonia.Animation
 {
     public interface IAnimationSetter
     {
-        AvaloniaProperty Property { get; set; }
-        object Value { get; set; }
+        AvaloniaProperty? Property { get; set; }
+        object? Value { get; set; }
     }
 }

src/Avalonia.Animation/IAnimator.cs

@@ -11,11 +11,11 @@ namespace Avalonia.Animation
         /// <summary>
         /// The target property.
         /// </summary>
-        AvaloniaProperty Property {get; set;}
+        AvaloniaProperty? Property {get; set;}
 
         /// <summary>
         /// Applies the current KeyFrame group to the specified control.
         /// </summary>
-        IDisposable Apply(Animation animation, Animatable control, IClock clock, IObservable<bool> match, Action onComplete);
+        IDisposable? Apply(Animation animation, Animatable control, IClock? clock, IObservable<bool> match, Action? onComplete);
     }
 }

src/Avalonia.Animation/ITransition.cs

@@ -10,7 +10,7 @@ namespace Avalonia.Animation
         /// <summary>
         /// Applies the transition to the specified <see cref="Animatable"/>.
         /// </summary>
-        IDisposable Apply(Animatable control, IClock clock, object oldValue, object newValue);
+        IDisposable Apply(Animatable control, IClock clock, object? oldValue, object? newValue);
 
         /// <summary>
         /// Gets the property to be animated.

src/Avalonia.Animation/IterationCount.cs

@@ -97,7 +97,7 @@ namespace Avalonia.Animation
         /// </summary>
         /// <param name="o">The object with which to test equality.</param>
         /// <returns>True if the objects are equal, otherwise false.</returns>
-        public override bool Equals(object o)
+        public override bool Equals(object? o)
         {
             if (o == null)
             {

src/Avalonia.Animation/IterationCountTypeConverter.cs

@@ -6,12 +6,12 @@ namespace Avalonia.Animation
 {
     public class IterationCountTypeConverter : TypeConverter
     {
-        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
         {
             return sourceType == typeof(string);
         }
 
-        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
         {
             return IterationCount.Parse((string)value);
         }

src/Avalonia.Animation/KeyFrame.cs

@@ -19,7 +19,7 @@ namespace Avalonia.Animation
     {
         private TimeSpan _ktimeSpan;
         private Cue _kCue;
-        private KeySpline _kKeySpline;
+        private KeySpline? _kKeySpline;
 
         public KeyFrame()
         {
@@ -79,7 +79,7 @@ namespace Avalonia.Animation
         /// Gets or sets the KeySpline of this <see cref="KeyFrame"/>.
         /// </summary>
         /// <value>The key spline.</value>
-        public KeySpline KeySpline
+        public KeySpline? KeySpline
         {
             get
             {

src/Avalonia.Animation/KeySplineTypeConverter.cs

@@ -12,12 +12,12 @@ namespace Avalonia.Animation
     /// </summary>
     public class KeySplineTypeConverter : TypeConverter
     {
-        public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
+        public override bool CanConvertFrom(ITypeDescriptorContext? context, Type sourceType)
         {
             return sourceType == typeof(string);
         }
 
-        public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
+        public override object ConvertFrom(ITypeDescriptorContext? context, CultureInfo? culture, object value)
         {
             return KeySpline.Parse((string)value, CultureInfo.InvariantCulture);
         }

src/Avalonia.Animation/Transition.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics.CodeAnalysis;
 using Avalonia.Animation.Easings;
 
 namespace Avalonia.Animation
@@ -8,7 +9,7 @@ namespace Avalonia.Animation
     /// </summary>
     public abstract class Transition<T> : AvaloniaObject, ITransition
     {
-        private AvaloniaProperty _prop;
+        private AvaloniaProperty? _prop;
 
         /// <summary>
         /// Gets or sets the duration of the transition.
@@ -26,7 +27,8 @@ namespace Avalonia.Animation
         public Easing Easing { get; set; } = new LinearEasing();
 
         /// <inheritdocs/>
-        public AvaloniaProperty Property
+        [DisallowNull]
+        public AvaloniaProperty? Property
         {
             get
             {
@@ -42,16 +44,25 @@ namespace Avalonia.Animation
             }
         }
 
+        AvaloniaProperty ITransition.Property
+        {
+            get => Property ?? throw new InvalidOperationException("Transition has no property specified.");
+            set => Property = value;
+        }
+
         /// <summary>
         /// Apply interpolation to the property.
         /// </summary>
         public abstract IObservable<T> DoTransition(IObservable<double> progress, T oldValue, T newValue);
 
         /// <inheritdocs/>
-        public virtual IDisposable Apply(Animatable control, IClock clock, object oldValue, object newValue)
+        public virtual IDisposable Apply(Animatable control, IClock clock, object? oldValue, object? newValue)
         {
-            var transition = DoTransition(new TransitionInstance(clock, Delay, Duration), (T)oldValue, (T)newValue);
+            if (Property is null)
+                throw new InvalidOperationException("Transition has no property specified.");
+
+            var transition = DoTransition(new TransitionInstance(clock, Delay, Duration), (T)oldValue!, (T)newValue!);
             return control.Bind<T>((AvaloniaProperty<T>)Property, transition, Data.BindingPriority.Animation);
         }
     }
-}
+}

src/Avalonia.Animation/TransitionInstance.cs

@@ -10,11 +10,11 @@ namespace Avalonia.Animation
     /// </summary>
     internal class TransitionInstance : SingleSubscriberObservableBase<double>, IObserver<TimeSpan>
     {
-        private IDisposable _timerSubscription;
+        private IDisposable? _timerSubscription;
         private TimeSpan _delay;
         private TimeSpan _duration;
         private readonly IClock _baseClock;
-        private TransitionClock _clock;
+        private TransitionClock? _clock;
 
         public TransitionInstance(IClock clock, TimeSpan delay, TimeSpan duration)
         {
@@ -67,7 +67,7 @@ namespace Avalonia.Animation
         protected override void Unsubscribed()
         {
             _timerSubscription?.Dispose();
-            _clock.PlayState = PlayState.Stop;
+            _clock!.PlayState = PlayState.Stop;
         }
 
         protected override void Subscribed()

src/Avalonia.Base/Collections/AvaloniaDictionary.cs

@@ -146,6 +146,7 @@ namespace Avalonia.Collections
         {
             if (_inner.TryGetValue(key, out var value))
             {
+                _inner.Remove(key);
                 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(Count)));
                 PropertyChanged?.Invoke(this, new PropertyChangedEventArgs($"Item[{key}]"));
 

src/Avalonia.Base/Collections/NotifyCollectionChangedExtensions.cs

@@ -59,7 +59,7 @@ namespace Avalonia.Collections
         }
 
         private class WeakCollectionChangedObservable : LightweightObservableBase<NotifyCollectionChangedEventArgs>,
-            IWeakSubscriber<NotifyCollectionChangedEventArgs>
+            IWeakEventSubscriber<NotifyCollectionChangedEventArgs>
         {
             private WeakReference<INotifyCollectionChanged> _sourceReference;
 
@@ -68,31 +68,22 @@ namespace Avalonia.Collections
                 _sourceReference = source;
             }
 
-            public void OnEvent(object? sender, NotifyCollectionChangedEventArgs e)
+            public void OnEvent(object? sender,
+                WeakEvent ev,
+                NotifyCollectionChangedEventArgs e)
             {
                 PublishNext(e);
             }
-
             protected override void Initialize()
             {
                 if (_sourceReference.TryGetTarget(out var instance))
-                {
-                    WeakSubscriptionManager.Subscribe(
-                    instance,
-                    nameof(instance.CollectionChanged),
-                    this);
-                }
+                    WeakEvents.CollectionChanged.Subscribe(instance, this);
             }
 
             protected override void Deinitialize()
             {
                 if (_sourceReference.TryGetTarget(out var instance))
-                {
-                    WeakSubscriptionManager.Unsubscribe(
-                        instance,
-                        nameof(instance.CollectionChanged),
-                        this);
-                }
+                    WeakEvents.CollectionChanged.Unsubscribe(instance, this);
             }
         }
     }

src/Avalonia.Base/Data/Core/IndexerNodeBase.cs

@@ -23,18 +23,16 @@ namespace Avalonia.Data.Core
 
             if (incc != null)
             {
-                inputs.Add(WeakObservable.FromEventPattern<INotifyCollectionChanged, NotifyCollectionChangedEventArgs>(
-                    incc,
-                    nameof(incc.CollectionChanged))
+                inputs.Add(WeakObservable.FromEventPattern(
+                    incc, WeakEvents.CollectionChanged)
                     .Where(x => ShouldUpdate(x.Sender, x.EventArgs))
                     .Select(_ => GetValue(target)));
             }
 
             if (inpc != null)
             {
-                inputs.Add(WeakObservable.FromEventPattern<INotifyPropertyChanged, PropertyChangedEventArgs>(
-                    inpc,
-                    nameof(inpc.PropertyChanged))
+                inputs.Add(WeakObservable.FromEventPattern(
+                    inpc, WeakEvents.PropertyChanged)
                     .Where(x => ShouldUpdate(x.Sender, x.EventArgs))
                     .Select(_ => GetValue(target)));
             }

src/Avalonia.Base/Data/Core/Plugins/IndeiValidationPlugin.cs

@@ -11,6 +11,12 @@ namespace Avalonia.Data.Core.Plugins
     /// </summary>
     public class IndeiValidationPlugin : IDataValidationPlugin
     {
+        private static readonly WeakEvent<INotifyDataErrorInfo, DataErrorsChangedEventArgs>
+            ErrorsChangedWeakEvent = WeakEvent.Register<INotifyDataErrorInfo, DataErrorsChangedEventArgs>(
+                (s, h) => s.ErrorsChanged += h,
+                (s, h) => s.ErrorsChanged -= h
+            );
+
         /// <inheritdoc/>
         public bool Match(WeakReference<object?> reference, string memberName)
         {
@@ -25,7 +31,7 @@ namespace Avalonia.Data.Core.Plugins
             return new Validator(reference, name, accessor);
         }
 
-        private class Validator : DataValidationBase, IWeakSubscriber<DataErrorsChangedEventArgs>
+        private class Validator : DataValidationBase, IWeakEventSubscriber<DataErrorsChangedEventArgs>
         {
             private readonly WeakReference<object?> _reference;
             private readonly string _name;
@@ -37,7 +43,7 @@ namespace Avalonia.Data.Core.Plugins
                 _name = name;
             }
 
-            void IWeakSubscriber<DataErrorsChangedEventArgs>.OnEvent(object? sender, DataErrorsChangedEventArgs e)
+            void IWeakEventSubscriber<DataErrorsChangedEventArgs>.OnEvent(object? notifyDataErrorInfo, WeakEvent ev, DataErrorsChangedEventArgs e)
             {
                 if (e.PropertyName == _name || string.IsNullOrEmpty(e.PropertyName))
                 {
@@ -51,10 +57,7 @@ namespace Avalonia.Data.Core.Plugins
 
                 if (target != null)
                 {
-                    WeakSubscriptionManager.Subscribe(
-                        target,
-                        nameof(target.ErrorsChanged),
-                        this);
+                    ErrorsChangedWeakEvent.Subscribe(target, this);
                 }
 
                 base.SubscribeCore();
@@ -66,10 +69,7 @@ namespace Avalonia.Data.Core.Plugins
 
                 if (target != null)
                 {
-                    WeakSubscriptionManager.Unsubscribe(
-                        target,
-                        nameof(target.ErrorsChanged),
-                        this);
+                    ErrorsChangedWeakEvent.Unsubscribe(target, this);
                 }
 
                 base.UnsubscribeCore();

src/Avalonia.Base/Data/Core/Plugins/InpcPropertyAccessorPlugin.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.Specialized;
 using System.ComponentModel;
 using System.Reflection;
 using Avalonia.Utilities;
@@ -85,7 +86,7 @@ namespace Avalonia.Data.Core.Plugins
             return found;
         }
 
-        private class Accessor : PropertyAccessorBase, IWeakSubscriber<PropertyChangedEventArgs>
+        private class Accessor : PropertyAccessorBase, IWeakEventSubscriber<PropertyChangedEventArgs>
         {
             private readonly WeakReference<object?> _reference;
             private readonly PropertyInfo _property;
@@ -129,7 +130,8 @@ namespace Avalonia.Data.Core.Plugins
                 return false;
             }
 
-            void IWeakSubscriber<PropertyChangedEventArgs>.OnEvent(object? sender, PropertyChangedEventArgs e)
+            void IWeakEventSubscriber<PropertyChangedEventArgs>.
+                OnEvent(object? notifyPropertyChanged, WeakEvent ev, PropertyChangedEventArgs e)
             {
                 if (e.PropertyName == _property.Name || string.IsNullOrEmpty(e.PropertyName))
                 {
@@ -148,13 +150,8 @@ namespace Avalonia.Data.Core.Plugins
             {
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
-                if (inpc != null)
-                {
-                    WeakSubscriptionManager.Unsubscribe(
-                        inpc,
-                        nameof(inpc.PropertyChanged),
-                        this);
-                }
+                if (inpc != null) 
+                    WeakEvents.PropertyChanged.Unsubscribe(inpc, this);
             }
 
             private object? GetReferenceTarget()
@@ -178,13 +175,8 @@ namespace Avalonia.Data.Core.Plugins
             {
                 var inpc = GetReferenceTarget() as INotifyPropertyChanged;
 
-                if (inpc != null)
-                {
-                    WeakSubscriptionManager.Subscribe(
-                        inpc,
-                        nameof(inpc.PropertyChanged),
-                        this);
-                }
+                if (inpc != null) 
+                    WeakEvents.PropertyChanged.Subscribe(inpc, this);
             }
         }
     }

src/Avalonia.Base/Platform/IRuntimePlatform.cs

@@ -1,5 +1,4 @@
 using System;
-using System.Reflection;
 
 namespace Avalonia.Platform
 {
@@ -23,6 +22,7 @@ namespace Avalonia.Platform
         public OperatingSystemType OperatingSystem { get; set; }
         public bool IsDesktop { get; set; }
         public bool IsMobile { get; set; }
+        public bool IsBrowser { get; set; }
         public bool IsCoreClr { get; set; }
         public bool IsMono { get; set; }
         public bool IsDotNetFramework { get; set; }
@@ -36,6 +36,7 @@ namespace Avalonia.Platform
         Linux,
         OSX,
         Android,
-        iOS
+        iOS,
+        Browser
     }
 }

src/Avalonia.Base/Threading/AvaloniaSynchronizationContext.cs

@@ -30,7 +30,7 @@ namespace Avalonia.Threading
         /// <inheritdoc/>
         public override void Post(SendOrPostCallback d, object? state)
         {
-           Dispatcher.UIThread.Post(() => d(state), DispatcherPriority.Send);
+           Dispatcher.UIThread.Post(() => d(state), DispatcherPriority.Background);
         }
 
         /// <inheritdoc/>

src/Avalonia.Base/Threading/Dispatcher.cs

@@ -74,6 +74,13 @@ namespace Avalonia.Threading
         /// </summary>
         /// <param name="minimumPriority"></param>
         public void RunJobs(DispatcherPriority minimumPriority) => _jobRunner.RunJobs(minimumPriority);
+        
+        /// <summary>
+        /// Use this method to check if there are more prioritized tasks
+        /// </summary>
+        /// <param name="minimumPriority"></param>
+        public bool HasJobsWithPriority(DispatcherPriority minimumPriority) =>
+            _jobRunner.HasJobsWithPriority(minimumPriority);
 
         /// <inheritdoc/>
         public Task InvokeAsync(Action action, DispatcherPriority priority = DispatcherPriority.Normal)

src/Avalonia.Base/Threading/JobRunner.cs

@@ -121,6 +121,21 @@ namespace Avalonia.Threading
             return null;
         }
 
+        public bool HasJobsWithPriority(DispatcherPriority minimumPriority)
+        {
+            for (int c = (int)minimumPriority; c < (int)DispatcherPriority.MaxValue; c++)
+            {
+                var q = _queues[c];
+                lock (q)
+                {
+                    if (q.Count > 0)
+                        return true;
+                }
+            }
+
+            return false;
+        }
+
         private interface IJob
         {
             /// <summary>

src/Avalonia.Base/Utilities/IWeakEventSubscriber.cs

@@ -0,0 +1,12 @@
+using System;
+
+namespace Avalonia.Utilities;
+
+/// <summary>
+/// Defines a listener to a event subscribed vis the <see cref="WeakEvent{TTarget, TEventArgs}"/>.
+/// </summary>
+/// <typeparam name="TEventArgs">The type of the event arguments.</typeparam>
+public interface IWeakEventSubscriber<in TEventArgs> where TEventArgs : EventArgs
+{
+    void OnEvent(object? sender, WeakEvent ev, TEventArgs e);
+}

src/Avalonia.Base/Utilities/ImmutableReadOnlyListStructEnumerator.cs

@@ -3,7 +3,7 @@ using System.Collections.Generic;
 
 namespace Avalonia.Utilities
 {
-    public struct ImmutableReadOnlyListStructEnumerator<T> : IEnumerator, IEnumerator<T>
+    public struct ImmutableReadOnlyListStructEnumerator<T> : IEnumerator<T>
     {
         private readonly IReadOnlyList<T> _readOnlyList;
         private int _pos;

src/Avalonia.Base/Utilities/WeakEvent.cs

@@ -0,0 +1,187 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using Avalonia.Threading;
+
+namespace Avalonia.Utilities;
+
+/// <summary>
+/// Manages subscriptions to events using weak listeners.
+/// </summary>
+public class WeakEvent<TSender, TEventArgs> : WeakEvent where TEventArgs : EventArgs where TSender : class
+{
+    private readonly Func<TSender, EventHandler<TEventArgs>, Action> _subscribe;
+
+    readonly ConditionalWeakTable<object, Subscription> _subscriptions = new();
+
+    internal WeakEvent(
+        Action<TSender, EventHandler<TEventArgs>> subscribe,
+        Action<TSender, EventHandler<TEventArgs>> unsubscribe)
+    {
+        _subscribe = (t, s) =>
+        {
+            subscribe(t, s);
+            return () => unsubscribe(t, s);
+        };
+    }
+    
+    internal WeakEvent(Func<TSender, EventHandler<TEventArgs>, Action> subscribe)
+    {
+        _subscribe = subscribe;
+    }
+    
+    public void Subscribe(TSender target, IWeakEventSubscriber<TEventArgs> subscriber)
+    {
+        if (!_subscriptions.TryGetValue(target, out var subscription))
+            _subscriptions.Add(target, subscription = new Subscription(this, target));
+        subscription.Add(new WeakReference<IWeakEventSubscriber<TEventArgs>>(subscriber));
+    }
+
+    public void Unsubscribe(TSender target, IWeakEventSubscriber<TEventArgs> subscriber)
+    {
+        if (_subscriptions.TryGetValue(target, out var subscription)) 
+            subscription.Remove(subscriber);
+    }
+
+    private class Subscription
+    {
+        private readonly WeakEvent<TSender, TEventArgs> _ev;
+        private readonly TSender _target;
+        private readonly Action _compact;
+
+        private WeakReference<IWeakEventSubscriber<TEventArgs>>?[] _data =
+            new WeakReference<IWeakEventSubscriber<TEventArgs>>[16];
+        private int _count;
+        private readonly Action _unsubscribe;
+        private bool _compactScheduled;
+
+        public Subscription(WeakEvent<TSender, TEventArgs> ev, TSender target)
+        {
+            _ev = ev;
+            _target = target;
+            _compact = Compact;
+            _unsubscribe = ev._subscribe(target, OnEvent);
+        }
+
+        void Destroy()
+        {
+            _unsubscribe();
+            _ev._subscriptions.Remove(_target);
+        }
+
+        public void Add(WeakReference<IWeakEventSubscriber<TEventArgs>> s)
+        {
+            if (_count == _data.Length)
+            {
+                //Extend capacity
+                var extendedData = new WeakReference<IWeakEventSubscriber<TEventArgs>>?[_data.Length * 2];
+                Array.Copy(_data, extendedData, _data.Length);
+                _data = extendedData;
+            }
+
+            _data[_count] = s;
+            _count++;
+        }
+
+        public void Remove(IWeakEventSubscriber<TEventArgs> s)
+        {
+            var removed = false;
+
+            for (int c = 0; c < _count; ++c)
+            {
+                var reference = _data[c];
+
+                if (reference != null && reference.TryGetTarget(out var instance) && instance == s)
+                {
+                    _data[c] = null;
+                    removed = true;
+                }
+            }
+
+            if (removed)
+            {
+                ScheduleCompact();
+            }
+        }
+
+        void ScheduleCompact()
+        {
+            if(_compactScheduled)
+                return;
+            _compactScheduled = true;
+            Dispatcher.UIThread.Post(_compact, DispatcherPriority.Background);
+        }
+        
+        void Compact()
+        {
+            _compactScheduled = false;
+            int empty = -1;
+            for (var c = 0; c < _count; c++)
+            {
+                var r = _data[c];
+                //Mark current index as first empty
+                if (r == null && empty == -1)
+                    empty = c;
+                //If current element isn't null and we have an empty one
+                if (r != null && empty != -1)
+                {
+                    _data[c] = null;
+                    _data[empty] = r;
+                    empty++;
+                }
+            }
+
+            if (empty != -1)
+                _count = empty;
+            if (_count == 0)
+                Destroy();
+        }
+
+        void OnEvent(object? sender, TEventArgs eventArgs)
+        {
+            var needCompact = false;
+            for (var c = 0; c < _count; c++)
+            {
+                var r = _data[c];
+                if (r?.TryGetTarget(out var sub) == true)
+                    sub!.OnEvent(_target, _ev, eventArgs);
+                else
+                    needCompact = true;
+            }
+
+            if (needCompact)
+                ScheduleCompact();
+        }
+    }
+
+}
+
+public class WeakEvent
+{
+    public static WeakEvent<TSender, TEventArgs> Register<TSender, TEventArgs>(
+        Action<TSender, EventHandler<TEventArgs>> subscribe,
+        Action<TSender, EventHandler<TEventArgs>> unsubscribe) where TSender : class where TEventArgs : EventArgs
+    {
+        return new WeakEvent<TSender, TEventArgs>(subscribe, unsubscribe);
+    }
+    
+    public static WeakEvent<TSender, TEventArgs> Register<TSender, TEventArgs>(
+        Func<TSender, EventHandler<TEventArgs>, Action> subscribe) where TSender : class where TEventArgs : EventArgs
+    {
+        return new WeakEvent<TSender, TEventArgs>(subscribe);
+    }
+    
+    public static WeakEvent<TSender, EventArgs> Register<TSender>(
+        Action<TSender, EventHandler> subscribe,
+        Action<TSender, EventHandler> unsubscribe) where TSender : class
+    {
+        return Register<TSender, EventArgs>((s, h) =>
+        {
+            EventHandler handler = (_, e) => h(s, e);
+            subscribe(s, handler);
+            return () => unsubscribe(s, handler);
+        });
+    }
+}

src/Avalonia.Base/Utilities/WeakEvents.cs

@@ -0,0 +1,40 @@
+using System;
+using System.Collections.Specialized;
+using System.ComponentModel;
+using System.Windows.Input;
+
+namespace Avalonia.Utilities;
+
+public class WeakEvents
+{
+    /// <summary>
+    /// Represents CollectionChanged event from <see cref="INotifyCollectionChanged"/>
+    /// </summary>
+    public static readonly WeakEvent<INotifyCollectionChanged, NotifyCollectionChangedEventArgs>
+        CollectionChanged = WeakEvent.Register<INotifyCollectionChanged, NotifyCollectionChangedEventArgs>(
+            (c, s) =>
+            {
+                NotifyCollectionChangedEventHandler handler = (_, e) => s(c, e);
+                c.CollectionChanged += handler;
+                return () => c.CollectionChanged -= handler;
+            });
+    
+    /// <summary>
+    /// Represents PropertyChanged event from <see cref="INotifyPropertyChanged"/>
+    /// </summary>
+    public static readonly WeakEvent<INotifyPropertyChanged, PropertyChangedEventArgs>
+        PropertyChanged = WeakEvent.Register<INotifyPropertyChanged, PropertyChangedEventArgs>(
+            (s, h) =>
+            {
+                PropertyChangedEventHandler handler = (_, e) => h(s, e);
+                s.PropertyChanged += handler;
+                return () => s.PropertyChanged -= handler;
+            });
+
+    /// <summary>
+    /// Represents CanExecuteChanged event from <see cref="ICommand"/>
+    /// </summary>
+    public static readonly WeakEvent<ICommand, EventArgs> CommandCanExecuteChanged =
+        WeakEvent.Register<ICommand>((s, h) => s.CanExecuteChanged += h,
+            (s, h) => s.CanExecuteChanged -= h);
+}

src/Avalonia.Base/Utilities/WeakObservable.cs

@@ -18,6 +18,7 @@ namespace Avalonia.Utilities
         /// <param name="target">Object instance that exposes the event to convert.</param>
         /// <param name="eventName">Name of the event to convert.</param>
         /// <returns></returns>
+        [Obsolete("Use WeakEvent-based overload")]
         public static IObservable<EventPattern<object, TEventArgs>> FromEventPattern<TTarget, TEventArgs>(
             TTarget target, 
             string eventName)
@@ -34,7 +35,9 @@ namespace Avalonia.Utilities
             }).Publish().RefCount();
         }
 
-        private class Handler<TEventArgs> : IWeakSubscriber<TEventArgs> where TEventArgs : EventArgs
+        private class Handler<TEventArgs> 
+            : IWeakSubscriber<TEventArgs>,
+                IWeakEventSubscriber<TEventArgs> where TEventArgs : EventArgs
         {
             private IObserver<EventPattern<object, TEventArgs>> _observer;
 
@@ -47,6 +50,36 @@ namespace Avalonia.Utilities
             {
                 _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();
+        }
+
     }
 }

src/Avalonia.Base/Utilities/WeakSubscriptionManager.cs

@@ -19,6 +19,7 @@ namespace Avalonia.Utilities
         /// <param name="target">The event source.</param>
         /// <param name="eventName">The name of the event.</param>
         /// <param name="subscriber">The subscriber.</param>
+        [Obsolete("Use WeakEvent")]
         public static void Subscribe<TTarget, TEventArgs>(TTarget target, string eventName, IWeakSubscriber<TEventArgs> subscriber)
             where TEventArgs : EventArgs
         {

src/Avalonia.Controls.DataGrid/DataGrid.cs

@@ -2215,7 +2215,14 @@ namespace Avalonia.Controls
         /// <param name="e">PointerWheelEventArgs</param>
         protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
         {
-            e.Handled = e.Handled || UpdateScroll(e.Delta * DATAGRID_mouseWheelDelta);
+            if(UpdateScroll(e.Delta * DATAGRID_mouseWheelDelta))
+            {
+                e.Handled = true;
+            }
+            else
+            {
+                e.Handled = e.Handled || !ScrollViewer.GetIsScrollChainingEnabled(this);
+            }
         }
 
         internal bool UpdateScroll(Vector delta)
@@ -5751,6 +5758,7 @@ namespace Avalonia.Controls
                 return true;
             }
             // Unselect everything except the row that was clicked on
+            _noSelectionChangeCount++;
             try
             {
                 UpdateSelectionAndCurrency(columnIndex, slot, DataGridSelectionAction.SelectCurrent, scrollIntoView: false);

src/Avalonia.Controls.DataGrid/DataGridColumn.cs

@@ -448,7 +448,7 @@ namespace Avalonia.Controls
             internal set;
         }
 
-        public bool IsReadOnly
+        public virtual bool IsReadOnly
         {
             get
             {
@@ -680,7 +680,7 @@ namespace Avalonia.Controls
         public void ClearSort()
         {
             //InvokeProcessSort is already validating if sorting is possible
-            _headerCell?.InvokeProcessSort(Input.KeyModifiers.Control);
+            _headerCell?.InvokeProcessSort(KeyboardHelper.GetPlatformCtrlOrCmdKeyModifier());
         }
 
         /// <summary>

src/Avalonia.Controls.DataGrid/DataGridTemplateColumn.cs

@@ -1,4 +1,4 @@
-// (c) Copyright Microsoft Corporation.
+// (c) Copyright Microsoft Corporation.
 // This source is subject to the Microsoft Public License (Ms-PL).
 // Please see http://go.microsoft.com/fwlink/?LinkID=131993 for details.
 // All other rights reserved.
@@ -15,7 +15,7 @@ namespace Avalonia.Controls
 {
     public class DataGridTemplateColumn : DataGridColumn
     {
-        IDataTemplate _cellTemplate;
+        private IDataTemplate _cellTemplate;
 
         public static readonly DirectProperty<DataGridTemplateColumn, IDataTemplate> CellTemplateProperty =
             AvaloniaProperty.RegisterDirect<DataGridTemplateColumn, IDataTemplate>(
@@ -30,17 +30,38 @@ namespace Avalonia.Controls
             set { SetAndRaise(CellTemplateProperty, ref _cellTemplate, value); }
         }
 
+        private IDataTemplate _cellEditingCellTemplate;
+
+        /// <summary>
+        /// Defines the <see cref="CellEditingTemplate"/> property.
+        /// </summary>
+        public static readonly DirectProperty<DataGridTemplateColumn, IDataTemplate> CellEditingTemplateProperty =
+                AvaloniaProperty.RegisterDirect<DataGridTemplateColumn, IDataTemplate>(
+                    nameof(CellEditingTemplate),
+                    o => o.CellEditingTemplate,
+                    (o, v) => o.CellEditingTemplate = v);
+
+        /// <summary>
+        /// Gets or sets the <see cref="IDataTemplate"/> which is used for the editing mode of the current <see cref="DataGridCell"/>
+        /// </summary>
+        /// <value>
+        /// An <see cref="IDataTemplate"/> for the editing mode of the current <see cref="DataGridCell"/>
+        /// </value>
+        /// <remarks>
+        /// If this property is <see langword="null"/> the column is read-only.
+        /// </remarks>
+        public IDataTemplate CellEditingTemplate
+        {
+            get => _cellEditingCellTemplate;
+            set => SetAndRaise(CellEditingTemplateProperty, ref _cellEditingCellTemplate, value);
+        }
+        
         private void OnCellTemplateChanged(AvaloniaPropertyChangedEventArgs e)
         {
             var oldValue = (IDataTemplate)e.OldValue;
             var value = (IDataTemplate)e.NewValue;
         }
 
-        public DataGridTemplateColumn()
-        {
-            IsReadOnly = true;
-        }
-
         protected override IControl GenerateElement(DataGridCell cell, object dataItem)
         {
             if(CellTemplate != null)
@@ -60,7 +81,22 @@ namespace Avalonia.Controls
         protected override IControl GenerateEditingElement(DataGridCell cell, object dataItem, out ICellEditBinding binding)
         {
             binding = null;
-            return GenerateElement(cell, dataItem);
+            if(CellEditingTemplate != null)
+            {
+                return CellEditingTemplate.Build(dataItem);
+            }
+            else if (CellTemplate != null)
+            {
+                return CellTemplate.Build(dataItem);
+            }
+            if (Design.IsDesignMode)
+            {
+                return null;
+            }
+            else
+            {
+                throw DataGridError.DataGridTemplateColumn.MissingTemplateForType(typeof(DataGridTemplateColumn));
+            }
         }
 
         protected override object PrepareCellForEdit(IControl editingElement, RoutedEventArgs editingEventArgs)
@@ -70,12 +106,30 @@ namespace Avalonia.Controls
 
         protected internal override void RefreshCellContent(IControl element, string propertyName)
         {
-            if(propertyName == nameof(CellTemplate) && element.Parent is DataGridCell cell)
+            var cell = element.Parent as DataGridCell;
+            if(propertyName == nameof(CellTemplate) && cell is not null)
             {
                 cell.Content = GenerateElement(cell, cell.DataContext);
             }
 
             base.RefreshCellContent(element, propertyName);
         }
+        
+        public override bool IsReadOnly
+        {
+            get
+            {
+                if (CellEditingTemplate is null)
+                {
+                    return true;
+                }
+
+                return base.IsReadOnly;
+            }
+            set
+            {
+                base.IsReadOnly = value;
+            }
+        }
     }
 }

src/Avalonia.Controls.DataGrid/Utils/KeyboardHelper.cs

@@ -4,22 +4,29 @@
 // All other rights reserved.
 
 using Avalonia.Input;
+using Avalonia.Input.Platform;
 
 namespace Avalonia.Controls.Utils
 {
     internal static class KeyboardHelper
     {
-        public static void GetMetaKeyState(KeyModifiers modifiers, out bool ctrl, out bool shift)
+        public static void GetMetaKeyState(KeyModifiers modifiers, out bool ctrlOrCmd, out bool shift)
         {
-            ctrl = (modifiers & KeyModifiers.Control) == KeyModifiers.Control;
-            shift = (modifiers & KeyModifiers.Shift) == KeyModifiers.Shift;
+            ctrlOrCmd = modifiers.HasFlag(GetPlatformCtrlOrCmdKeyModifier());
+            shift = modifiers.HasFlag(KeyModifiers.Shift);
         }
 
-        public static void GetMetaKeyState(KeyModifiers modifiers, out bool ctrl, out bool shift, out bool alt)
+        public static void GetMetaKeyState(KeyModifiers modifiers, out bool ctrlOrCmd, out bool shift, out bool alt)
         {
-            ctrl = (modifiers & KeyModifiers.Control) == KeyModifiers.Control;
-            shift = (modifiers & KeyModifiers.Shift) == KeyModifiers.Shift;
-            alt = (modifiers & KeyModifiers.Alt) == KeyModifiers.Alt;
+            ctrlOrCmd = modifiers.HasFlag(GetPlatformCtrlOrCmdKeyModifier());
+            shift = modifiers.HasFlag(KeyModifiers.Shift);
+            alt = modifiers.HasFlag(KeyModifiers.Alt);
+        }
+
+        public static KeyModifiers GetPlatformCtrlOrCmdKeyModifier()
+        {                
+            var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
+            return keymap?.CommandModifiers ?? KeyModifiers.Control;
         }
     }
 }

src/Avalonia.Controls/ApiCompatBaseline.txt

@@ -29,15 +29,25 @@ MembersMustExist : Member 'public void Avalonia.Controls.NumericUpDownValueChang
 MembersMustExist : Member 'public System.Double Avalonia.Controls.NumericUpDownValueChangedEventArgs.NewValue.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public System.Double Avalonia.Controls.NumericUpDownValueChangedEventArgs.OldValue.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public Avalonia.StyledProperty<System.Boolean> Avalonia.StyledProperty<System.Boolean> Avalonia.Controls.ScrollViewer.AllowAutoHideProperty' does not exist in the implementation but it does exist in the contract.
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.TopLevel' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
 MembersMustExist : Member 'public Avalonia.AvaloniaProperty<Avalonia.Media.Stretch> Avalonia.AvaloniaProperty<Avalonia.Media.Stretch> Avalonia.Controls.Viewbox.StretchProperty' does not exist in the implementation but it does exist in the contract.
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.Window' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.WindowBase' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.EventHandler<Avalonia.Controls.ApplicationLifetimes.ShutdownRequestedEventArgs> Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.ShutdownRequested' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.add_ShutdownRequested(System.EventHandler<Avalonia.Controls.ApplicationLifetimes.ShutdownRequestedEventArgs>)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.remove_ShutdownRequested(System.EventHandler<Avalonia.Controls.ApplicationLifetimes.ShutdownRequestedEventArgs>)' is present in the implementation but not in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.TryShutdown(System.Int32)' is present in the implementation but not in the contract.
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.Embedding.EmbeddableControlRoot' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
 MembersMustExist : Member 'public System.Action<Avalonia.Size> Avalonia.Controls.Embedding.Offscreen.OffscreenTopLevelImplBase.Resized.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public void Avalonia.Controls.Embedding.Offscreen.OffscreenTopLevelImplBase.Resized.set(System.Action<Avalonia.Size>)' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public void Avalonia.Controls.Embedding.Offscreen.OffscreenTopLevelImplBase.SetCursor(Avalonia.Platform.IPlatformHandle)' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public Avalonia.AvaloniaProperty Avalonia.AvaloniaProperty Avalonia.Controls.Notifications.NotificationCard.CloseOnClickProperty' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Controls.Platform.ITopLevelNativeMenuExporter.SetNativeMenu(Avalonia.Controls.NativeMenu)' is present in the contract but not in the implementation.
+MembersMustExist : Member 'protected Avalonia.Media.FormattedText Avalonia.Controls.Presenters.TextPresenter.CreateFormattedText()' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.FormattedText Avalonia.Controls.Presenters.TextPresenter.FormattedText.get()' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public System.Int32 Avalonia.Controls.Presenters.TextPresenter.GetCaretIndex(Avalonia.Point)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'protected void Avalonia.Controls.Presenters.TextPresenter.InvalidateFormattedText()' does not exist in the implementation but it does exist in the contract.
+CannotRemoveBaseTypeOrInterface : Type 'Avalonia.Controls.Primitives.PopupRoot' does not implement interface 'Avalonia.Utilities.IWeakSubscriber<Avalonia.Controls.ResourcesChangedEventArgs>' in the implementation but it does in the contract.
 EnumValuesMustMatch : Enum value 'Avalonia.Platform.ExtendClientAreaChromeHints Avalonia.Platform.ExtendClientAreaChromeHints.Default' is (System.Int32)2 in the implementation but (System.Int32)1 in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Nullable<Avalonia.Size> Avalonia.Platform.ITopLevelImpl.FrameSize' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public System.Nullable<Avalonia.Size> Avalonia.Platform.ITopLevelImpl.FrameSize.get()' is present in the implementation but not in the contract.
@@ -57,4 +67,4 @@ InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platfor
 MembersMustExist : Member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size)' does not exist in the implementation but it does exist in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public void Avalonia.Platform.IWindowImpl.Resize(Avalonia.Size, Avalonia.Platform.PlatformResizeReason)' is present in the implementation but not in the contract.
 InterfacesShouldHaveSameMembers : Interface member 'public Avalonia.Platform.ITrayIconImpl Avalonia.Platform.IWindowingPlatform.CreateTrayIcon()' is present in the implementation but not in the contract.
-Total Issues: 58
+Total Issues: 68

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -76,36 +76,21 @@ namespace Avalonia.Controls.ApplicationLifetimes
                 return;
 
             if (ShutdownMode == ShutdownMode.OnLastWindowClose && _windows.Count == 0)
-                Shutdown();
-            else if (ShutdownMode == ShutdownMode.OnMainWindowClose && window == MainWindow)
-                Shutdown();
+                TryShutdown();
+            else if (ShutdownMode == ShutdownMode.OnMainWindowClose && ReferenceEquals(window, MainWindow))
+                TryShutdown();
         }
 
         public void Shutdown(int exitCode = 0)
         {
-            if (_isShuttingDown)
-                throw new InvalidOperationException("Application is already shutting down.");
-            
-            _exitCode = exitCode;
-            _isShuttingDown = true;
+            DoShutdown(new ShutdownRequestedEventArgs(), true, exitCode);
+        }
 
-            try
-            {
-                foreach (var w in Windows)
-                    w.Close();
-                var e = new ControlledApplicationLifetimeExitEventArgs(exitCode);
-                Exit?.Invoke(this, e);
-                _exitCode = e.ApplicationExitCode;                
-            }
-            finally
-            {
-                _cts?.Cancel();
-                _cts = null;
-                _isShuttingDown = false;
-            }
+        public bool TryShutdown(int exitCode = 0)
+        {
+            return DoShutdown(new ShutdownRequestedEventArgs(), false, exitCode);
         }
         
-        
         public int Start(string[] args)
         {
             Startup?.Invoke(this, new ControlledApplicationLifetimeStartupEventArgs(args));
@@ -114,7 +99,10 @@ namespace Avalonia.Controls.ApplicationLifetimes
             
             if(options != null && options.ProcessUrlActivationCommandLine && args.Length > 0)
             {
-                ((IApplicationPlatformEvents)Application.Current).RaiseUrlsOpened(args);
+                if (Application.Current is IApplicationPlatformEvents events)
+                {
+                    events.RaiseUrlsOpened(args);
+                }
             }
 
             var lifetimeEvents = AvaloniaLocator.Current.GetService<IPlatformLifetimeEventsImpl>(); 
@@ -145,23 +133,57 @@ namespace Avalonia.Controls.ApplicationLifetimes
             if (_activeLifetime == this)
                 _activeLifetime = null;
         }
-        
-        private void OnShutdownRequested(object sender, ShutdownRequestedEventArgs e)
+
+        private bool DoShutdown(ShutdownRequestedEventArgs e, bool force = false, int exitCode = 0)
         {
-            ShutdownRequested?.Invoke(this, e);
+            if (!force)
+            {
+                ShutdownRequested?.Invoke(this, e);
 
-            if (e.Cancel)
-                return;
+                if (e.Cancel)
+                    return false;
+
+                if (_isShuttingDown)
+                    throw new InvalidOperationException("Application is already shutting down.");
+            }
+
+            _exitCode = exitCode;
+            _isShuttingDown = true;
 
-            // When an OS shutdown request is received, try to close all non-owned windows. Windows can cancel
-            // shutdown by setting e.Cancel = true in the Closing event. Owned windows will be shutdown by their
-            // owners.
-            foreach (var w in Windows)
-                if (w.Owner is null)
-                    w.Close();
-            if (Windows.Count > 0)
-                e.Cancel = true;
+            try
+            {
+                // When an OS shutdown request is received, try to close all non-owned windows. Windows can cancel
+                // shutdown by setting e.Cancel = true in the Closing event. Owned windows will be shutdown by their
+                // owners.
+                foreach (var w in Windows)
+                {
+                    if (w.Owner is null)
+                    {
+                        w.Close();
+                    }
+                }
+
+                if (!force && Windows.Count > 0)
+                {
+                    e.Cancel = true;
+                    return false;
+                }
+
+                var args = new ControlledApplicationLifetimeExitEventArgs(exitCode);
+                Exit?.Invoke(this, args);
+                _exitCode = args.ApplicationExitCode;                
+            }
+            finally
+            {
+                _cts?.Cancel();
+                _cts = null;
+                _isShuttingDown = false;
+            }
+
+            return true;
         }
+        
+        private void OnShutdownRequested(object sender, ShutdownRequestedEventArgs e) => DoShutdown(e);
     }
     
     public class ClassicDesktopStyleApplicationLifetimeOptions

src/Avalonia.Controls/ApplicationLifetimes/IClassicDesktopStyleApplicationLifetime.cs

@@ -9,6 +9,12 @@ namespace Avalonia.Controls.ApplicationLifetimes
     /// </summary>
     public interface IClassicDesktopStyleApplicationLifetime : IControlledApplicationLifetime
     {
+        /// <summary>
+        /// Tries to Shutdown the application. <see cref="ShutdownRequested" /> event can be used to cancel the shutdown.
+        /// </summary>
+        /// <param name="exitCode">An integer exit code for an application. The default exit code is 0.</param>
+        bool TryShutdown(int exitCode = 0);
+
         /// <summary>
         /// Gets the arguments passed to the
         /// <see cref="ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime{T}(T, string[], ShutdownMode)"/>

src/Avalonia.Controls/Button.cs

@@ -59,13 +59,13 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<Button, object>(nameof(CommandParameter));
 
         /// <summary>
-        /// Defines the <see cref="IsDefaultProperty"/> property.
+        /// Defines the <see cref="IsDefault"/> property.
         /// </summary>
         public static readonly StyledProperty<bool> IsDefaultProperty =
             AvaloniaProperty.Register<Button, bool>(nameof(IsDefault));
 
         /// <summary>
-        /// Defines the <see cref="IsCancelProperty"/> property.
+        /// Defines the <see cref="IsCancel"/> property.
         /// </summary>
         public static readonly StyledProperty<bool> IsCancelProperty =
             AvaloniaProperty.Register<Button, bool>(nameof(IsCancel));
@@ -76,6 +76,9 @@ namespace Avalonia.Controls
         public static readonly RoutedEvent<RoutedEventArgs> ClickEvent =
             RoutedEvent.Register<Button, RoutedEventArgs>(nameof(Click), RoutingStrategies.Bubble);
 
+        /// <summary>
+        /// Defines the <see cref="IsPressed"/> property.
+        /// </summary>
         public static readonly StyledProperty<bool> IsPressedProperty =
             AvaloniaProperty.Register<Button, bool>(nameof(IsPressed));
 
@@ -95,13 +98,12 @@ namespace Avalonia.Controls
         static Button()
         {
             FocusableProperty.OverrideDefaultValue(typeof(Button), true);
-            CommandProperty.Changed.Subscribe(CommandChanged);
-            CommandParameterProperty.Changed.Subscribe(CommandParameterChanged);
-            IsDefaultProperty.Changed.Subscribe(IsDefaultChanged);
-            IsCancelProperty.Changed.Subscribe(IsCancelChanged);
             AccessKeyHandler.AccessKeyPressedEvent.AddClassHandler<Button>((lbl, args) => lbl.OnAccessKey(args));
         }
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="Button"/> class.
+        /// </summary>
         public Button()
         {
             UpdatePseudoClasses(IsPressed);
@@ -112,8 +114,8 @@ namespace Avalonia.Controls
         /// </summary>
         public event EventHandler<RoutedEventArgs> Click
         {
-            add { AddHandler(ClickEvent, value); }
-            remove { RemoveHandler(ClickEvent, value); }
+            add => AddHandler(ClickEvent, value);
+            remove => RemoveHandler(ClickEvent, value);
         }
 
         /// <summary>
@@ -121,8 +123,8 @@ namespace Avalonia.Controls
         /// </summary>
         public ClickMode ClickMode
         {
-            get { return GetValue(ClickModeProperty); }
-            set { SetValue(ClickModeProperty, value); }
+            get => GetValue(ClickModeProperty);
+            set => SetValue(ClickModeProperty, value);
         }
 
         /// <summary>
@@ -130,8 +132,8 @@ namespace Avalonia.Controls
         /// </summary>
         public ICommand Command
         {
-            get { return _command; }
-            set { SetAndRaise(CommandProperty, ref _command, value); }
+            get => _command;
+            set => SetAndRaise(CommandProperty, ref _command, value);
         }
 
         /// <summary>
@@ -139,8 +141,8 @@ namespace Avalonia.Controls
         /// </summary>
         public KeyGesture HotKey
         {
-            get { return GetValue(HotKeyProperty); }
-            set { SetValue(HotKeyProperty, value); }
+            get => GetValue(HotKeyProperty);
+            set => SetValue(HotKeyProperty, value);
         }
 
         /// <summary>
@@ -148,8 +150,8 @@ namespace Avalonia.Controls
         /// </summary>
         public object CommandParameter
         {
-            get { return GetValue(CommandParameterProperty); }
-            set { SetValue(CommandParameterProperty, value); }
+            get => GetValue(CommandParameterProperty);
+            set => SetValue(CommandParameterProperty, value);
         }
 
         /// <summary>
@@ -158,8 +160,8 @@ namespace Avalonia.Controls
         /// </summary>
         public bool IsDefault
         {
-            get { return GetValue(IsDefaultProperty); }
-            set { SetValue(IsDefaultProperty, value); }
+            get => GetValue(IsDefaultProperty);
+            set => SetValue(IsDefaultProperty, value);
         }
 
         /// <summary>
@@ -168,18 +170,21 @@ namespace Avalonia.Controls
         /// </summary>
         public bool IsCancel
         {
-            get { return GetValue(IsCancelProperty); }
-            set { SetValue(IsCancelProperty, value); }
+            get => GetValue(IsCancelProperty);
+            set => SetValue(IsCancelProperty, value);
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether the button is currently pressed.
+        /// </summary>
         public bool IsPressed
         {
-            get { return GetValue(IsPressedProperty); }
-            private set { SetValue(IsPressedProperty, value); }
+            get => GetValue(IsPressedProperty);
+            private set => SetValue(IsPressedProperty, value);
         }
 
         /// <summary>
-        /// Gets or sets the Flyout that should be shown with this button
+        /// Gets or sets the Flyout that should be shown with this button.
         /// </summary>
         public FlyoutBase Flyout
         {
@@ -187,7 +192,8 @@ namespace Avalonia.Controls
             set => SetValue(FlyoutProperty, value);
         }
 
-        protected override bool IsEnabledCore => base.IsEnabledCore && _commandCanExecute; 
+        /// <inheritdoc/>
+        protected override bool IsEnabledCore => base.IsEnabledCore && _commandCanExecute;
 
         /// <inheritdoc/>
         protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
@@ -224,6 +230,7 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <inheritdoc/>
         protected override void OnAttachedToLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
             if (_hotkey != null) // Control attached again, set Hotkey to create a hotkey manager for this control
@@ -240,6 +247,7 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <inheritdoc/>
         protected override void OnDetachedFromLogicalTree(LogicalTreeAttachmentEventArgs e)
         {
             // This will cause the hotkey manager to dispose the observer and the reference to this control
@@ -358,12 +366,14 @@ namespace Avalonia.Controls
                 }
             }
         }
-        
+
+        /// <inheritdoc/>
         protected override void OnPointerCaptureLost(PointerCaptureLostEventArgs e)
         {
             IsPressed = false;
         }
 
+        /// <inheritdoc/>
         protected override void OnLostFocus(RoutedEventArgs e)
         {
             base.OnLostFocus(e);
@@ -371,119 +381,93 @@ namespace Avalonia.Controls
             IsPressed = false;
         }
 
+        /// <inheritdoc/>
         protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
         {
             base.OnPropertyChanged(change);
 
-            if (change.Property == IsPressedProperty)
-            {
-                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<bool>());
-            }
-            else if (change.Property == FlyoutProperty)
+            if (change.Property == CommandProperty)
             {
-                // If flyout is changed while one is already open, make sure we 
-                // close the old one first
-                if (change.OldValue.GetValueOrDefault() is FlyoutBase oldFlyout &&
-                    oldFlyout.IsOpen)
+                if (((ILogical)this).IsAttachedToLogicalTree)
                 {
-                    oldFlyout.Hide();
+                    if (change.OldValue.GetValueOrDefault() is ICommand oldCommand)
+                    {
+                        oldCommand.CanExecuteChanged -= CanExecuteChanged;
+                    }
+
+                    if (change.NewValue.GetValueOrDefault() is ICommand newCommand)
+                    {
+                        newCommand.CanExecuteChanged += CanExecuteChanged;
+                    }
                 }
-            }
-        }
 
-        protected override void UpdateDataValidation<T>(AvaloniaProperty<T> property, BindingValue<T> value)
-        {
-            base.UpdateDataValidation(property, value);
-            if (property == CommandProperty)
+                CanExecuteChanged(this, EventArgs.Empty);
+            }
+            else if (change.Property == CommandParameterProperty)
             {
-                if (value.Type == BindingValueType.BindingError)
+                CanExecuteChanged(this, EventArgs.Empty);
+            }
+            else if (change.Property == IsCancelProperty)
+            {
+                var isCancel = change.NewValue.GetValueOrDefault<bool>();
+
+                if (VisualRoot is IInputElement inputRoot)
                 {
-                    if (_commandCanExecute)
+                    if (isCancel)
                     {
-                        _commandCanExecute = false;
-                        UpdateIsEffectivelyEnabled();
+                        ListenForCancel(inputRoot);
+                    }
+                    else
+                    {
+                        StopListeningForCancel(inputRoot);
                     }
                 }
             }
-        }
-
-        /// <summary>
-        /// Called when the <see cref="Command"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private static void CommandChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (e.Sender is Button button)
+            else if (change.Property == IsDefaultProperty)
             {
-                if (((ILogical)button).IsAttachedToLogicalTree)
+                var isDefault = change.NewValue.GetValueOrDefault<bool>();
+
+                if (VisualRoot is IInputElement inputRoot)
                 {
-                    if (e.OldValue is ICommand oldCommand)
+                    if (isDefault)
                     {
-                        oldCommand.CanExecuteChanged -= button.CanExecuteChanged;
+                        ListenForDefault(inputRoot);
                     }
-
-                    if (e.NewValue is ICommand newCommand)
+                    else
                     {
-                        newCommand.CanExecuteChanged += button.CanExecuteChanged;
+                        StopListeningForDefault(inputRoot);
                     }
                 }
-
-                button.CanExecuteChanged(button, EventArgs.Empty);
             }
-        }
-
-        /// <summary>
-        /// Called when the <see cref="CommandParameter"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private static void CommandParameterChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            if (e.Sender is Button button)
+            else if (change.Property == IsPressedProperty)
             {
-                button.CanExecuteChanged(button, EventArgs.Empty);
+                UpdatePseudoClasses(change.NewValue.GetValueOrDefault<bool>());
             }
-        }
-
-        /// <summary>
-        /// Called when the <see cref="IsDefault"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private static void IsDefaultChanged(AvaloniaPropertyChangedEventArgs e)
-        {
-            var button = e.Sender as Button;
-            var isDefault = (bool)e.NewValue;
-
-            if (button?.VisualRoot is IInputElement inputRoot)
+            else if (change.Property == FlyoutProperty)
             {
-                if (isDefault)
-                {
-                    button.ListenForDefault(inputRoot);
-                }
-                else
+                // If flyout is changed while one is already open, make sure we 
+                // close the old one first
+                if (change.OldValue.GetValueOrDefault() is FlyoutBase oldFlyout &&
+                    oldFlyout.IsOpen)
                 {
-                    button.StopListeningForDefault(inputRoot);
+                    oldFlyout.Hide();
                 }
             }
         }
 
-        /// <summary>
-        /// Called when the <see cref="IsCancel"/> property changes.
-        /// </summary>
-        /// <param name="e">The event args.</param>
-        private static void IsCancelChanged(AvaloniaPropertyChangedEventArgs e)
+        /// <inheritdoc/>
+        protected override void UpdateDataValidation<T>(AvaloniaProperty<T> property, BindingValue<T> value)
         {
-            var button = e.Sender as Button;
-            var isCancel = (bool)e.NewValue;
-
-            if (button?.VisualRoot is IInputElement inputRoot)
+            base.UpdateDataValidation(property, value);
+            if (property == CommandProperty)
             {
-                if (isCancel)
-                {
-                    button.ListenForCancel(inputRoot);
-                }
-                else
+                if (value.Type == BindingValueType.BindingError)
                 {
-                    button.StopListeningForCancel(inputRoot);
+                    if (_commandCanExecute)
+                    {
+                        _commandCanExecute = false;
+                        UpdateIsEffectivelyEnabled();
+                    }
                 }
             }
         }
@@ -566,6 +550,9 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Updates the visual state of the control by applying latest PseudoClasses.
+        /// </summary>
         private void UpdatePseudoClasses(bool isPressed)
         {
             PseudoClasses.Set(":pressed", isPressed);

src/Avalonia.Controls/Calendar/CalendarDatePicker.cs

@@ -185,7 +185,8 @@ namespace Avalonia.Controls
             AvaloniaProperty.RegisterDirect<CalendarDatePicker, DateTime?>(
                 nameof(SelectedDate),
                 o => o.SelectedDate,
-                (o, v) => o.SelectedDate = v);
+                (o, v) => o.SelectedDate = v,
+                enableDataValidation: true);
 
         public static readonly StyledProperty<CalendarDatePickerFormat> SelectedDateFormatProperty =
             AvaloniaProperty.Register<CalendarDatePicker, CalendarDatePickerFormat>(
@@ -533,13 +534,11 @@ namespace Avalonia.Controls
             }
         }
 
-        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        protected override void UpdateDataValidation<T>(AvaloniaProperty<T> property, BindingValue<T> value)
         {
-            base.OnPropertyChanged(change);
-
-            if (change.Property == SelectedDateProperty)
+            if (property == SelectedDateProperty)
             {
-                DataValidationErrors.SetError(this, change.NewValue.Error);
+                DataValidationErrors.SetError(this, value.Error);
             }
         }
 

src/Avalonia.Controls/Control.cs

@@ -1,10 +1,12 @@
 using System;
 using System.ComponentModel;
+using System.Runtime.CompilerServices;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.Interactivity;
+using Avalonia.Media;
 using Avalonia.Rendering;
 using Avalonia.Styling;
 using Avalonia.VisualTree;
@@ -60,7 +62,13 @@ namespace Avalonia.Controls
         public static readonly RoutedEvent<ContextRequestedEventArgs> ContextRequestedEvent =
             RoutedEvent.Register<Control, ContextRequestedEventArgs>(nameof(ContextRequested),
                 RoutingStrategies.Tunnel | RoutingStrategies.Bubble);
-
+        
+        /// <summary>
+        /// Defines the <see cref="FlowDirection"/> property.
+        /// </summary>
+        public static readonly AttachedProperty<FlowDirection> FlowDirectionProperty =
+            AvaloniaProperty.RegisterAttached<Control, Control, FlowDirection>(nameof(FlowDirection), inherits: true);
+        
         private DataTemplates? _dataTemplates;
         private IControl? _focusAdorner;
 
@@ -108,6 +116,15 @@ namespace Avalonia.Controls
             get => GetValue(TagProperty);
             set => SetValue(TagProperty, value);
         }
+        
+        /// <summary>
+        /// Gets or sets the text flow direction.
+        /// </summary>
+        public FlowDirection FlowDirection
+        {
+            get => GetValue(FlowDirectionProperty);
+            set => SetValue(FlowDirectionProperty, value);
+        }
 
         /// <summary>
         /// Occurs when the user has completed a context input gesture, such as a right-click.

src/Avalonia.Controls/Flyouts/MenuFlyoutPresenter.cs

@@ -43,5 +43,18 @@ namespace Avalonia.Controls
         {
             return new MenuItemContainerGenerator(this);
         }
+
+        protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromVisualTree(e);
+
+            foreach (var i in LogicalChildren)
+            {
+                if (i is MenuItem menuItem)
+                {
+                    menuItem.IsSubMenuOpen = false;
+                }
+            }
+        }
     }
 }

src/Avalonia.Controls/LayoutTransformControl.cs

@@ -18,7 +18,7 @@ namespace Avalonia.Controls
             AvaloniaProperty.Register<LayoutTransformControl, ITransform>(nameof(LayoutTransform));
 
         public static readonly StyledProperty<bool> UseRenderTransformProperty =
-            AvaloniaProperty.Register<LayoutTransformControl, bool>(nameof(LayoutTransform));
+            AvaloniaProperty.Register<LayoutTransformControl, bool>(nameof(UseRenderTransform));
 
         static LayoutTransformControl()
         {

src/Avalonia.Controls/NativeMenuItem.cs

@@ -33,7 +33,7 @@ namespace Avalonia.Controls
         }
 
 
-        class CanExecuteChangedSubscriber : IWeakSubscriber<EventArgs>
+        class CanExecuteChangedSubscriber : IWeakEventSubscriber<EventArgs>
         {
             private readonly NativeMenuItem _parent;
 
@@ -42,7 +42,7 @@ namespace Avalonia.Controls
                 _parent = parent;
             }
 
-            public void OnEvent(object sender, EventArgs e)
+            public void OnEvent(object? sender, WeakEvent ev, EventArgs e)
             {
                 _parent.CanExecuteChanged();
             }
@@ -160,14 +160,12 @@ namespace Avalonia.Controls
             set
             {
                 if (_command != null)
-                    WeakSubscriptionManager.Unsubscribe(_command,
-                        nameof(ICommand.CanExecuteChanged), _canExecuteChangedSubscriber);
+                    WeakEvents.CommandCanExecuteChanged.Unsubscribe(_command, _canExecuteChangedSubscriber);
 
                 SetAndRaise(CommandProperty, ref _command, value);
 
                 if (_command != null)
-                    WeakSubscriptionManager.Subscribe(_command,
-                        nameof(ICommand.CanExecuteChanged), _canExecuteChangedSubscriber);
+                    WeakEvents.CommandCanExecuteChanged.Subscribe(_command, _canExecuteChangedSubscriber);
 
                 CanExecuteChanged();
             }

src/Avalonia.Controls/Platform/DefaultMenuInteractionHandler.cs

@@ -101,7 +101,7 @@ namespace Avalonia.Controls.Platform
                 root.Deactivated -= WindowDeactivated;
             }
             
-            if (_root is TopLevel tl)
+            if (_root is TopLevel tl && tl.PlatformImpl != null)
                 tl.PlatformImpl.LostFocus -= TopLevelLostPlatformFocus;
 
             _inputManagerSubscription?.Dispose();

src/Avalonia.Controls/Presenters/ScrollContentPresenter.cs

@@ -60,6 +60,12 @@ namespace Avalonia.Controls.Presenters
                 o => o.Viewport,
                 (o, v) => o.Viewport = v);
 
+        /// <summary>
+        /// Defines the <see cref="IsScrollChainingEnabled"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> IsScrollChainingEnabledProperty =
+            ScrollViewer.IsScrollChainingEnabledProperty.AddOwner<ScrollContentPresenter>();
+
         private bool _canHorizontallyScroll;
         private bool _canVerticallyScroll;
         private bool _arranging;
@@ -138,6 +144,20 @@ namespace Avalonia.Controls.Presenters
             private set { SetAndRaise(ViewportProperty, ref _viewport, value); }
         }
 
+        /// <summary>
+        ///  Gets or sets if scroll chaining is enabled. The default value is true.
+        /// </summary>
+        /// <remarks>
+        ///  After a user hits a scroll limit on an element that has been nested within another scrollable element,
+        /// you can specify whether that parent element should continue the scrolling operation begun in its child element.
+        /// This is called scroll chaining.
+        /// </remarks>
+        public bool IsScrollChainingEnabled
+        {
+            get => GetValue(IsScrollChainingEnabledProperty);
+            set => SetValue(IsScrollChainingEnabledProperty, value);
+        }
+
         /// <inheritdoc/>
         IControl? IScrollAnchorProvider.CurrentAnchor
         {
@@ -405,8 +425,11 @@ namespace Avalonia.Controls.Presenters
                     _activeLogicalGestureScrolls[e.Id] = delta;
                 }
 
-                Offset = new Vector(x, y);
-                e.Handled = true;
+                Vector newOffset = new Vector(x, y);
+                bool offsetChanged = newOffset != Offset;
+                Offset = newOffset;
+
+                e.Handled = !IsScrollChainingEnabled || offsetChanged;
             }
         }
 
@@ -440,8 +463,11 @@ namespace Avalonia.Controls.Presenters
                     x = Math.Min(x, Extent.Width - Viewport.Width);
                 }
 
-                Offset = new Vector(x, y);
-                e.Handled = true;
+                Vector newOffset = new Vector(x, y);
+                bool offsetChanged = newOffset != Offset;
+                Offset = newOffset;
+
+                e.Handled = !IsScrollChainingEnabled || offsetChanged;
             }
         }
 

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -1,9 +1,12 @@
 using System;
+using System.Collections.Generic;
+using System.Diagnostics;
 using System.Reactive.Linq;
-using Avalonia.Input.TextInput;
 using Avalonia.Media;
+using Avalonia.Media.TextFormatting;
 using Avalonia.Metadata;
 using Avalonia.Threading;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 using Avalonia.Layout;
 using Avalonia.Media.Immutable;
@@ -75,28 +78,18 @@ namespace Avalonia.Controls.Presenters
         private int _selectionEnd;
         private bool _caretBlink;
         private string _text;
-        private FormattedText _formattedText;
-        private Size _constraint;
+        private TextLayout _textLayout;
+        private Size _constraint = Size.Infinity;
 
-        static TextPresenter()
-        {
-            AffectsRender<TextPresenter>(SelectionBrushProperty, TextBlock.ForegroundProperty, 
-                                         SelectionForegroundBrushProperty, CaretBrushProperty,
-                                         SelectionStartProperty, SelectionEndProperty);
-            
-            AffectsMeasure<TextPresenter>(TextProperty, PasswordCharProperty, RevealPasswordProperty, 
-                TextAlignmentProperty, TextWrappingProperty, TextBlock.FontSizeProperty,
-                TextBlock.FontStyleProperty, TextBlock.FontWeightProperty, TextBlock.FontFamilyProperty);
+        private CharacterHit _lastCharacterHit;
+        private Rect _caretBounds;
+        private Point _navigationPosition;
 
-            Observable.Merge<AvaloniaPropertyChangedEventArgs>(TextProperty.Changed, TextBlock.ForegroundProperty.Changed,
-                TextAlignmentProperty.Changed, TextWrappingProperty.Changed,
-                TextBlock.FontSizeProperty.Changed, TextBlock.FontStyleProperty.Changed, 
-                TextBlock.FontWeightProperty.Changed, TextBlock.FontFamilyProperty.Changed,
-                SelectionStartProperty.Changed, SelectionEndProperty.Changed,
-                SelectionForegroundBrushProperty.Changed, PasswordCharProperty.Changed, RevealPasswordProperty.Changed
-            ).AddClassHandler<TextPresenter>((x, _) => x.InvalidateFormattedText());
+        private ScrollViewer _scrollViewer;
 
-            CaretIndexProperty.Changed.AddClassHandler<TextPresenter>((x, e) => x.CaretIndexChanged((int)e.NewValue));
+        static TextPresenter()
+        {
+            AffectsRender<TextPresenter>(CaretBrushProperty, SelectionBrushProperty);
         }
 
         public TextPresenter()
@@ -106,6 +99,8 @@ namespace Avalonia.Controls.Presenters
             _caretTimer.Tick += CaretTimerTick;
         }
 
+        public event EventHandler CaretBoundsChanged;
+        
         /// <summary>
         /// Gets or sets a brush used to paint the control's background.
         /// </summary>
@@ -189,13 +184,22 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <summary>
-        /// Gets the <see cref="FormattedText"/> used to render the text.
+        /// Gets the <see cref="TextLayout"/> used to render the text.
         /// </summary>
-        public FormattedText FormattedText
+        public TextLayout TextLayout
         {
             get
             {
-                return _formattedText ?? (_formattedText = CreateFormattedText());
+                if (_textLayout != null)
+                {
+                    return _textLayout;
+                }
+                
+                _textLayout = CreateTextLayout();
+
+                UpdateCaret(_lastCharacterHit);
+                
+                return _textLayout;
             }
         }
 
@@ -205,11 +209,12 @@ namespace Avalonia.Controls.Presenters
             {
                 return _caretIndex;
             }
-
             set
             {
-                value = CoerceCaretIndex(value);
-                SetAndRaise(CaretIndexProperty, ref _caretIndex, value);
+                if (value != _caretIndex)
+                {
+                    MoveCaretToTextPosition(value);
+                }
             }
         }
 
@@ -271,37 +276,25 @@ namespace Avalonia.Controls.Presenters
             }
         }
 
-        public int GetCaretIndex(Point point)
-        {
-            var hit = FormattedText.HitTestPoint(point);
-            return hit.TextPosition + (hit.IsTrailing ? 1 : 0);
-        }
-
         /// <summary>
-        /// Creates the <see cref="FormattedText"/> used to render the text.
+        /// Creates the <see cref="TextLayout"/> used to render the text.
         /// </summary>
         /// <param name="constraint">The constraint of the text.</param>
         /// <param name="text">The text to format.</param>
-        /// <returns>A <see cref="FormattedText"/> object.</returns>
-        private FormattedText CreateFormattedTextInternal(Size constraint, string text)
-        {
-            return new FormattedText
-            {
-                Constraint = constraint,
-                Typeface = new Typeface(FontFamily, FontStyle, FontWeight),
-                FontSize = FontSize,
-                Text = text ?? string.Empty,
-                TextAlignment = TextAlignment,
-                TextWrapping = TextWrapping,
-            };
-        }
+        /// <param name="typeface"></param>
+        /// <param name="textStyleOverrides"></param>
+        /// <returns>A <see cref="TextLayout"/> object.</returns>
+        private TextLayout CreateTextLayoutInternal(Size constraint, string text, Typeface typeface,
+            IReadOnlyList<ValueSpan<TextRunProperties>> textStyleOverrides)
+        {
+            var maxWidth = MathUtilities.IsZero(constraint.Width) ? double.PositiveInfinity : constraint.Width;
+            var maxHeight = MathUtilities.IsZero(constraint.Height) ? double.PositiveInfinity : constraint.Height;
+            
+            var textLayout = new TextLayout(text ?? string.Empty, typeface, FontSize, Foreground, TextAlignment,
+                TextWrapping, maxWidth: maxWidth, maxHeight: maxHeight, textStyleOverrides: textStyleOverrides, 
+                flowDirection: FlowDirection);
 
-        /// <summary>
-        /// Invalidates <see cref="FormattedText"/>.
-        /// </summary>
-        protected void InvalidateFormattedText()
-        {
-            _formattedText = null;
+            return textLayout;
         }
 
         /// <summary>
@@ -317,31 +310,36 @@ namespace Avalonia.Controls.Presenters
                 context.FillRectangle(background, new Rect(Bounds.Size));
             }
 
-            double top = 0;
-            var textSize = FormattedText.Bounds.Size;
+            var top = 0d;
+            var left = 0.0;
+
+            var (_, textHeight) = TextLayout.Size;
 
-            if (Bounds.Height < textSize.Height)
+            if (Bounds.Height < textHeight)
             {
                 switch (VerticalAlignment)
                 {
                     case VerticalAlignment.Center:
-                        top += (Bounds.Height - textSize.Height) / 2;
+                        top += (Bounds.Height - textHeight) / 2;
                         break;
 
                     case VerticalAlignment.Bottom:
-                        top += (Bounds.Height - textSize.Height);
+                        top += (Bounds.Height - textHeight);
                         break;
                 }
             }
 
-            context.DrawText(Foreground, new Point(0, top), FormattedText);
+            TextLayout.Draw(context, new Point(left, top));
         }
 
         public override void Render(DrawingContext context)
         {
-            FormattedText.Constraint = Bounds.Size;
-
-            _constraint = Bounds.Size;
+            if (double.IsPositiveInfinity (_constraint.Width))
+            {
+                _constraint = _scrollViewer?.Viewport ?? Size.Infinity;
+                
+                InvalidateTextLayout();
+            }
 
             var selectionStart = SelectionStart;
             var selectionEnd = SelectionEnd;
@@ -351,7 +349,7 @@ namespace Avalonia.Controls.Presenters
                 var start = Math.Min(selectionStart, selectionEnd);
                 var length = Math.Max(selectionStart, selectionEnd) - start;
 
-                var rects = FormattedText.HitTestTextRange(start, length);
+                var rects = TextLayout.HitTestTextRange(start, length);
 
                 foreach (var rect in rects)
                 {
@@ -361,40 +359,47 @@ namespace Avalonia.Controls.Presenters
 
             RenderInternal(context);
 
-            if (selectionStart == selectionEnd && _caretBlink)
+            if (selectionStart != selectionEnd || !_caretBlink)
+            {
+                return;
+            }
+            
+            var caretBrush = CaretBrush?.ToImmutable();
+
+            if (caretBrush is null)
             {
-                var caretBrush = CaretBrush?.ToImmutable();
+                var backgroundColor = (Background as ISolidColorBrush)?.Color;
 
-                if (caretBrush is null)
+                if (backgroundColor.HasValue)
                 {
-                    var backgroundColor = (Background as ISolidColorBrush)?.Color;
-                    if (backgroundColor.HasValue)
-                    {
-                        byte red = (byte)~(backgroundColor.Value.R);
-                        byte green = (byte)~(backgroundColor.Value.G);
-                        byte blue = (byte)~(backgroundColor.Value.B);
+                    var red = (byte)~(backgroundColor.Value.R);
+                    var green = (byte)~(backgroundColor.Value.G);
+                    var blue = (byte)~(backgroundColor.Value.B);
 
-                        caretBrush = new ImmutableSolidColorBrush(Color.FromRgb(red, green, blue));
-                    }
-                    else
-                    {
-                        caretBrush = Brushes.Black;
-                    }
+                    caretBrush = new ImmutableSolidColorBrush(Color.FromRgb(red, green, blue));
+                }
+                else
+                {
+                    caretBrush = Brushes.Black;
                 }
-
-                var (p1, p2) = GetCaretPoints();
-                context.DrawLine(
-                    new ImmutablePen(caretBrush, 1),
-                    p1, p2);
             }
-        }
 
-        (Point, Point) GetCaretPoints()
+            var (p1, p2) = GetCaretPoints();
+
+            context.DrawLine(new ImmutablePen(caretBrush), p1, p2);
+        }
+        
+        private (Point, Point) GetCaretPoints()
         {
-            var charPos = FormattedText.HitTestTextPosition(CaretIndex);
-            var x = Math.Floor(charPos.X) + 0.5;
-            var y = Math.Floor(charPos.Y) + 0.5;
-            var b = Math.Ceiling(charPos.Bottom) - 0.5;
+            var x = Math.Floor(_caretBounds.X) + 0.5;
+            var y = Math.Floor(_caretBounds.Y) + 0.5;
+            var b = Math.Ceiling(_caretBounds.Bottom) - 0.5;
+
+            if (x >= Bounds.Width)
+            {
+                x = Math.Floor(_caretBounds.X - 1) + 0.5;
+            }
+            
             return (new Point(x, y), new Point(x, b));
         }
 
@@ -412,7 +417,7 @@ namespace Avalonia.Controls.Presenters
             InvalidateVisual();
         }
 
-        internal void CaretIndexChanged(int caretIndex)
+        internal void CaretChanged()
         {
             if (this.GetVisualParent() != null)
             {
@@ -432,8 +437,7 @@ namespace Avalonia.Controls.Presenters
 
                 if (IsMeasureValid)
                 {
-                    var rect = FormattedText.HitTestTextPosition(caretIndex);
-                    this.BringIntoView(rect);
+                    this.BringIntoView(_caretBounds);
                 }
                 else
                 {
@@ -443,8 +447,7 @@ namespace Avalonia.Controls.Presenters
                     Dispatcher.UIThread.Post(
                         () =>
                         {
-                            var rect = FormattedText.HitTestTextPosition(caretIndex);
-                            this.BringIntoView(rect);
+                            this.BringIntoView(_caretBounds);
                         },
                         DispatcherPriority.Render);
                 }
@@ -452,104 +455,310 @@ namespace Avalonia.Controls.Presenters
         }
 
         /// <summary>
-        /// Creates the <see cref="FormattedText"/> used to render the text.
+        /// Creates the <see cref="TextLayout"/> used to render the text.
         /// </summary>
-        /// <returns>A <see cref="FormattedText"/> object.</returns>
-        protected virtual FormattedText CreateFormattedText()
+        /// <returns>A <see cref="TextLayout"/> object.</returns>
+        protected virtual TextLayout CreateTextLayout()
         {
-            FormattedText result = null;
+            TextLayout result;
 
             var text = Text;
 
-            if (PasswordChar != default(char) && !RevealPassword)
-            {
-                result = CreateFormattedTextInternal(_constraint, new string(PasswordChar, text?.Length ?? 0));
-            }
-            else
-            {
-                result = CreateFormattedTextInternal(_constraint, text);
-            }
+            var typeface = new Typeface(FontFamily, FontStyle, FontWeight);
 
             var selectionStart = SelectionStart;
             var selectionEnd = SelectionEnd;
             var start = Math.Min(selectionStart, selectionEnd);
             var length = Math.Max(selectionStart, selectionEnd) - start;
 
+            IReadOnlyList<ValueSpan<TextRunProperties>> textStyleOverrides = null;
+            
             if (length > 0)
             {
-                result.Spans = new[]
+                textStyleOverrides = new[]
                 {
-                    new FormattedTextStyleSpan(start, length, SelectionForegroundBrush),
+                    new ValueSpan<TextRunProperties>(start, length,
+                        new GenericTextRunProperties(typeface, FontSize,
+                            foregroundBrush: SelectionForegroundBrush ?? Brushes.White))
                 };
             }
 
+            if (PasswordChar != default(char) && !RevealPassword)
+            {
+                result = CreateTextLayoutInternal(_constraint, new string(PasswordChar, text?.Length ?? 0), typeface,
+                    textStyleOverrides);
+            }
+            else
+            {
+                result = CreateTextLayoutInternal(_constraint, text, typeface, textStyleOverrides);
+            }
+
             return result;
         }
 
-        /// <summary>
-        /// Measures the control.
-        /// </summary>
-        /// <param name="availableSize">The available size for the control.</param>
-        /// <returns>The desired size.</returns>
-        private Size MeasureInternal(Size availableSize)
+        protected virtual void InvalidateTextLayout()
+        {
+            _textLayout = null;
+            
+            InvalidateMeasure();
+        }
+        
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            if (!double.IsInfinity(availableSize.Width) && availableSize != _constraint)
+            {
+                _constraint = availableSize;
+                
+                InvalidateTextLayout();
+            }
+
+            return TextLayout.Size;
+        }
+
+        private int CoerceCaretIndex(int value)
+        {
+            var text = Text;
+            var length = text?.Length ?? 0;
+            return Math.Max(0, Math.Min(length, value));
+        }
+
+        private void CaretTimerTick(object sender, EventArgs e)
+        {
+            _caretBlink = !_caretBlink;
+            InvalidateVisual();
+        }
+
+        public void MoveCaretToTextPosition(int textPosition, bool trailingEdge = false)
+        {
+            var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(textPosition, trailingEdge);
+            var textLine = TextLayout.TextLines[lineIndex];
+
+            var characterHit = textLine.GetPreviousCaretCharacterHit(new CharacterHit(textPosition));
+            
+            var nextCaretCharacterHit = textLine.GetNextCaretCharacterHit(characterHit);
+
+            if (nextCaretCharacterHit.FirstCharacterIndex <= textPosition)
+            {
+                characterHit = nextCaretCharacterHit;
+            }
+
+            if (textPosition == characterHit.FirstCharacterIndex + characterHit.TrailingLength)
+            {
+                UpdateCaret(characterHit);
+            }
+            else
+            {
+                UpdateCaret(trailingEdge ? characterHit : new CharacterHit(characterHit.FirstCharacterIndex));
+            }
+
+            _navigationPosition = _caretBounds.Position;
+        } 
+        
+        public void MoveCaretToPoint(Point point)
+        {
+            var hit = TextLayout.HitTestPoint(point);
+
+            UpdateCaret(hit.CharacterHit);
+
+            _navigationPosition = _caretBounds.Position;
+        }
+
+        public void MoveCaretVertical(LogicalDirection direction = LogicalDirection.Forward)
         {
-            if (!string.IsNullOrEmpty(Text))
+            var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(CaretIndex, _lastCharacterHit.TrailingLength > 0);
+
+            if (lineIndex < 0)
+            {
+                return;
+            }
+
+            var (currentX, currentY) = _navigationPosition;
+
+            if (direction == LogicalDirection.Forward)
             {
-                if (TextWrapping == TextWrapping.Wrap)
+                if (lineIndex + 1 > TextLayout.TextLines.Count - 1)
                 {
-                    _constraint = new Size(availableSize.Width, double.PositiveInfinity);
+                    return;
                 }
-                else
+
+                var textLine = TextLayout.TextLines[lineIndex];
+                
+                currentY += textLine.Height;
+            }
+            else
+            {
+                if (lineIndex - 1 < 0)
                 {
-                    _constraint = Size.Infinity;
+                    return;
                 }
 
-                _formattedText = null;
+                var textLine = TextLayout.TextLines[--lineIndex];
 
-                return FormattedText.Bounds.Size;
+                currentY -= textLine.Height;
             }
 
-            return new Size();
+            var navigationPosition = _navigationPosition;
+            
+            MoveCaretToPoint(new Point(currentX, currentY));
+            
+            _navigationPosition = navigationPosition.WithY(_caretBounds.Y);
         }
 
-        protected override Size MeasureOverride(Size availableSize)
+        public void MoveCaretHorizontal(LogicalDirection direction = LogicalDirection.Forward)
         {
-            var text = Text;
+            var characterHit = _lastCharacterHit;
+            var caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+            
+            var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(caretIndex, false);
 
-            if (!string.IsNullOrEmpty(text))
+            if (lineIndex < 0)
             {
-                return MeasureInternal(availableSize);
+                return;
+            }
+
+            if (direction == LogicalDirection.Forward)
+            {
+                while (lineIndex < TextLayout.TextLines.Count)
+                {
+                    var textLine = TextLayout.TextLines[lineIndex];
+
+                    characterHit = textLine.GetNextCaretCharacterHit(characterHit);
+
+                    caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+
+                    if (textLine.NewLineLength > 0 && caretIndex == textLine.TextRange.Start + textLine.TextRange.Length)
+                    {
+                        characterHit = new CharacterHit(caretIndex);
+                    }
+                    
+                    if (caretIndex >= Text.Length)
+                    {
+                        characterHit = new CharacterHit(Text.Length);
+                        
+                        break;
+                    }
+
+                    if (caretIndex - textLine.NewLineLength == textLine.TextRange.Start + textLine.TextRange.Length)
+                    {
+                        break;
+                    }
+
+                    if (caretIndex <= CaretIndex)
+                    {
+                        lineIndex++;
+                        
+                        continue;
+                    }
+                    
+                    break;
+                }
             }
             else
             {
-                return new FormattedText
+                while (lineIndex >= 0)
                 {
-                    Text = "X",
-                    Typeface = new Typeface(FontFamily, FontStyle, FontWeight),
-                    FontSize = FontSize,
-                    TextAlignment = TextAlignment,
-                    Constraint = availableSize,
-                }.Bounds.Size;
+                    var textLine = TextLayout.TextLines[lineIndex];
+
+                    characterHit = textLine.GetPreviousCaretCharacterHit(characterHit);
+
+                    caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+
+                    if (caretIndex >= CaretIndex)
+                    {
+                        lineIndex--;
+
+                        continue;
+                    }
+
+                    break;
+                }
             }
+
+            UpdateCaret(characterHit);
+
+            _navigationPosition = _caretBounds.Position;
         }
 
-        private int CoerceCaretIndex(int value)
+        private void UpdateCaret(CharacterHit characterHit)
         {
-            var text = Text;
-            var length = text?.Length ?? 0;
-            return Math.Max(0, Math.Min(length, value));
+            _lastCharacterHit = characterHit;
+            
+            var caretIndex = characterHit.FirstCharacterIndex + characterHit.TrailingLength;
+            
+            var lineIndex = TextLayout.GetLineIndexFromCharacterIndex(caretIndex, characterHit.TrailingLength > 0);
+            var textLine = TextLayout.TextLines[lineIndex];
+            var distanceX = textLine.GetDistanceFromCharacterHit(characterHit);
+
+            var distanceY = 0d;
+
+            for (var i = 0; i < lineIndex; i++)
+            {
+                var currentLine = TextLayout.TextLines[i];
+
+                distanceY += currentLine.Height;
+            }
+
+            var caretBounds = new Rect(distanceX, distanceY, 0, textLine.Height);
+            
+            if (caretBounds != _caretBounds)
+            {
+                _caretBounds = caretBounds;
+
+                CaretBoundsChanged?.Invoke(this, EventArgs.Empty);
+            }
+            
+            CaretChanged();
+            
+            SetAndRaise(CaretIndexProperty, ref _caretIndex, caretIndex);
         }
 
-        private void CaretTimerTick(object sender, EventArgs e)
+        internal Rect GetCursorRectangle()
         {
-            _caretBlink = !_caretBlink;
-            InvalidateVisual();
+            return _caretBounds;
         }
 
-        internal Rect GetCursorRectangle()
+        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
         {
-            var (p1, p2) = GetCaretPoints();
-            return new Rect(p1, p2);
+            base.OnAttachedToVisualTree(e);
+
+            _scrollViewer = this.FindAncestorOfType<ScrollViewer>();
+        }
+
+        protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromVisualTree(e);
+
+            _scrollViewer = null;
+            
+            _caretTimer.Stop();
+            
+            _caretTimer.Tick -= CaretTimerTick;
+        }
+
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        {
+            base.OnPropertyChanged(change);
+            
+            switch (change.Property.Name)
+            {
+                case nameof (TextBlock.Foreground):
+                case nameof (TextBlock.FontSize):
+                case nameof (TextBlock.FontStyle):
+                case nameof (TextBlock.FontWeight):
+                case nameof (TextBlock.FontFamily):
+                case nameof (Text):
+                case nameof (TextAlignment):
+                case nameof (TextWrapping):
+                case nameof (SelectionStart):
+                case nameof (SelectionEnd):
+                case nameof (SelectionForegroundBrush):
+                case nameof (PasswordChar):
+                case nameof (RevealPassword):
+                {
+                    InvalidateTextLayout();
+                    break;
+                }
+            }
         }
     }
 }

src/Avalonia.Controls/Primitives/Popup.cs

@@ -429,16 +429,20 @@ namespace Avalonia.Controls.Primitives
                     (x, handler) => x.LostFocus += handler,
                     (x, handler) => x.LostFocus -= handler).DisposeWith(handlerCleanup);
 
-                SubscribeToEventHandler<IWindowImpl, Action<PixelPoint>>(window.PlatformImpl, WindowPositionChanged,
-                    (x, handler) => x.PositionChanged += handler,
-                    (x, handler) => x.PositionChanged -= handler).DisposeWith(handlerCleanup);
-                    
-                if (placementTarget is Layoutable layoutTarget)
+                // Recalculate popup position on parent moved/resized, but not if placement was on pointer
+                if (PlacementMode != PlacementMode.Pointer)
                 {
-                    // If the placement target is moved, update the popup position
-                    SubscribeToEventHandler<Layoutable, EventHandler>(layoutTarget, PlacementTargetLayoutUpdated,
-                        (x, handler) => x.LayoutUpdated += handler,
-                        (x, handler) => x.LayoutUpdated -= handler).DisposeWith(handlerCleanup);
+                    SubscribeToEventHandler<IWindowImpl, Action<PixelPoint>>(window.PlatformImpl, WindowPositionChanged,
+                        (x, handler) => x.PositionChanged += handler,
+                        (x, handler) => x.PositionChanged -= handler).DisposeWith(handlerCleanup);
+
+                    if (placementTarget is Layoutable layoutTarget)
+                    {
+                        // If the placement target is moved, update the popup position
+                        SubscribeToEventHandler<Layoutable, EventHandler>(layoutTarget, PlacementTargetLayoutUpdated,
+                            (x, handler) => x.LayoutUpdated += handler,
+                            (x, handler) => x.LayoutUpdated -= handler).DisposeWith(handlerCleanup);
+                    }
                 }
             }
             else if (topLevel is PopupRoot parentPopupRoot)

src/Avalonia.Controls/Primitives/PopupRoot.cs

@@ -44,7 +44,7 @@ namespace Avalonia.Controls.Primitives
         /// The dependency resolver to use. If null the default dependency resolver will be used.
         /// </param>
         public PopupRoot(TopLevel parent, IPopupImpl impl, IAvaloniaDependencyResolver dependencyResolver)
-            : base(impl, dependencyResolver)
+            : base(ValidatingPopupImpl.Wrap(impl), dependencyResolver)
         {
             _parent = parent;
         }
@@ -74,7 +74,11 @@ namespace Avalonia.Controls.Primitives
         IStyleHost IStyleHost.StylingParent => Parent;
 
         /// <inheritdoc/>
-        public void Dispose() => PlatformImpl?.Dispose();
+        public void Dispose()
+        {
+            PlatformImpl?.Dispose();
+            HandleClosed();
+        }
 
         private void UpdatePosition()
         {

src/Avalonia.Controls/Properties/AssemblyInfo.cs

@@ -3,6 +3,7 @@ using Avalonia.Metadata;
 
 [assembly: InternalsVisibleTo("Avalonia.Controls.UnitTests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87")]
 [assembly: InternalsVisibleTo("Avalonia.DesignerSupport, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87")]
+[assembly: InternalsVisibleTo("Avalonia.LeakTests, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c1bba1142285fe0419326fb25866ba62c47e6c2b5c1ab0c95b46413fad375471232cb81706932e1cef38781b9ebd39d5100401bacb651c6c5bbf59e571e81b3bc08d2a622004e08b1a6ece82a7e0b9857525c86d2b95fab4bc3dce148558d7f3ae61aa3a234086902aeface87d9dfdd32b9d2fe3c6dd4055b5ab4b104998bd87")]
 
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia")]
 [assembly: XmlnsDefinition("https://github.com/avaloniaui", "Avalonia.Controls")]

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Controls
     /// Represents a data-driven collection control that incorporates a flexible layout system,
     /// custom views, and virtualization.
     /// </summary>
-    public class ItemsRepeater : Panel, IChildIndexProvider
+    public class ItemsRepeater : Panel, IChildIndexProvider, IWeakEventSubscriber<EventArgs>
     {
         /// <summary>
         /// Defines the <see cref="HorizontalCacheLength"/> property.
@@ -723,14 +723,8 @@ namespace Avalonia.Controls
             {
                 oldValue.UninitializeForContext(LayoutContext);
 
-                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
-                    oldValue,
-                    nameof(AttachedLayout.MeasureInvalidated),
-                    InvalidateMeasureForLayout);
-                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
-                    oldValue,
-                    nameof(AttachedLayout.ArrangeInvalidated),
-                    InvalidateArrangeForLayout);
+                AttachedLayout.MeasureInvalidatedWeakEvent.Unsubscribe(oldValue, this);
+                AttachedLayout.ArrangeInvalidatedWeakEvent.Unsubscribe(oldValue, this);
 
                 // Walk through all the elements and make sure they are cleared
                 foreach (var element in Children)
@@ -748,14 +742,8 @@ namespace Avalonia.Controls
             {
                 newValue.InitializeForContext(LayoutContext);
 
-                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
-                    newValue,
-                    nameof(AttachedLayout.MeasureInvalidated),
-                    InvalidateMeasureForLayout);
-                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
-                    newValue,
-                    nameof(AttachedLayout.ArrangeInvalidated),
-                    InvalidateArrangeForLayout);
+                AttachedLayout.MeasureInvalidatedWeakEvent.Subscribe(newValue, this);
+                AttachedLayout.ArrangeInvalidatedWeakEvent.Subscribe(newValue, this);
             }
 
             bool isVirtualizingLayout = newValue != null && newValue is VirtualizingLayout;
@@ -806,9 +794,13 @@ namespace Avalonia.Controls
             _viewportManager.OnBringIntoViewRequested(e);
         }
 
-        private void InvalidateMeasureForLayout(object sender, EventArgs e) => InvalidateMeasure();
-
-        private void InvalidateArrangeForLayout(object sender, EventArgs e) => InvalidateArrange();
+        void IWeakEventSubscriber<EventArgs>.OnEvent(object? sender, WeakEvent ev, EventArgs e)
+        {
+            if(ev == AttachedLayout.ArrangeInvalidatedWeakEvent)
+                InvalidateArrange();
+            else if (ev == AttachedLayout.MeasureInvalidatedWeakEvent)
+                InvalidateMeasure();
+        }
 
         private VirtualizingLayoutContext GetLayoutContext()
         {

src/Avalonia.Controls/ScrollViewer.cs

@@ -181,6 +181,14 @@ namespace Avalonia.Controls
                 nameof(AllowAutoHide),
                 true);
 
+        /// <summary>
+        /// Defines the <see cref="IsScrollChainingEnabled"/> property.
+        /// </summary>
+        public static readonly AttachedProperty<bool> IsScrollChainingEnabledProperty =
+            AvaloniaProperty.RegisterAttached<ScrollViewer, Control, bool>(
+                nameof(IsScrollChainingEnabled),
+                defaultValue: true);
+
         /// <summary>
         /// Defines the <see cref="ScrollChanged"/> event.
         /// </summary>
@@ -418,6 +426,20 @@ namespace Avalonia.Controls
             set => SetValue(AllowAutoHideProperty, value);
         }
 
+        /// <summary>
+        ///  Gets or sets if scroll chaining is enabled. The default value is true.
+        /// </summary>
+        /// <remarks>
+        ///  After a user hits a scroll limit on an element that has been nested within another scrollable element,
+        /// you can specify whether that parent element should continue the scrolling operation begun in its child element.
+        /// This is called scroll chaining.
+        /// </remarks>
+        public bool IsScrollChainingEnabled
+        {
+            get => GetValue(IsScrollChainingEnabledProperty);
+            set => SetValue(IsScrollChainingEnabledProperty, value);
+        }
+
         /// <summary>
         /// Scrolls the content up one line.
         /// </summary>
@@ -548,6 +570,36 @@ namespace Avalonia.Controls
             return control.GetValue(AllowAutoHideProperty);
         }
 
+        /// <summary>
+        /// Sets the value of the IsScrollChainingEnabled attached property.
+        /// </summary>
+        /// <param name="control">The control to set the value on.</param>
+        /// <param name="value">The value of the property.</param>
+        /// <remarks>
+        ///  After a user hits a scroll limit on an element that has been nested within another scrollable element,
+        /// you can specify whether that parent element should continue the scrolling operation begun in its child element.
+        /// This is called scroll chaining.
+        /// </remarks>
+        public static void SetIsScrollChainingEnabled(Control control, bool value)
+        {
+            control.SetValue(IsScrollChainingEnabledProperty, value);
+        }
+
+        /// <summary>
+        ///  Gets the value of the IsScrollChainingEnabled attached property.
+        /// </summary>
+        /// <param name="control">The control to read the value from.</param>
+        /// <returns>The value of the property.</returns>
+        /// <remarks>
+        ///  After a user hits a scroll limit on an element that has been nested within another scrollable element,
+        /// you can specify whether that parent element should continue the scrolling operation begun in its child element.
+        /// This is called scroll chaining.
+        /// </remarks>
+        public static bool GetIsScrollChainingEnabled(Control control)
+        {
+            return control.GetValue(IsScrollChainingEnabledProperty);
+        }
+
         /// <summary>
         /// Gets the value of the VerticalScrollBarVisibility attached property.
         /// </summary>

src/Avalonia.Controls/TextBlock.cs

@@ -131,21 +131,8 @@ namespace Avalonia.Controls
         static TextBlock()
         {
             ClipToBoundsProperty.OverrideDefaultValue<TextBlock>(true);
-
-            AffectsRender<TextBlock>(BackgroundProperty, ForegroundProperty,
-                TextAlignmentProperty, TextDecorationsProperty);
-
-            AffectsMeasure<TextBlock>(FontSizeProperty, FontWeightProperty,
-                FontStyleProperty, TextWrappingProperty, FontFamilyProperty,
-                TextTrimmingProperty, TextProperty, PaddingProperty, LineHeightProperty, MaxLinesProperty);
-
-            Observable.Merge<AvaloniaPropertyChangedEventArgs>(TextProperty.Changed, ForegroundProperty.Changed,
-                TextAlignmentProperty.Changed, TextWrappingProperty.Changed,
-                TextTrimmingProperty.Changed, FontSizeProperty.Changed,
-                FontStyleProperty.Changed, FontWeightProperty.Changed,
-                FontFamilyProperty.Changed, TextDecorationsProperty.Changed,
-                PaddingProperty.Changed, MaxLinesProperty.Changed, LineHeightProperty.Changed
-            ).AddClassHandler<TextBlock>((x, _) => x.InvalidateTextLayout());
+            
+            AffectsRender<TextBlock>(BackgroundProperty, ForegroundProperty);
         }
 
         /// <summary>
@@ -460,6 +447,7 @@ namespace Avalonia.Controls
                 TextWrapping,
                 TextTrimming,
                 TextDecorations,
+                FlowDirection,
                 constraint.Width,
                 constraint.Height,
                 maxLines: MaxLines,
@@ -472,6 +460,8 @@ namespace Avalonia.Controls
         protected void InvalidateTextLayout()
         {
             _textLayout = null;
+            
+            InvalidateMeasure();
         }
 
         /// <summary>
@@ -507,12 +497,40 @@ namespace Avalonia.Controls
             base.OnAttachedToLogicalTree(e);
 
             InvalidateTextLayout();
-
-            InvalidateMeasure();
         }
 
         private static bool IsValidMaxLines(int maxLines) => maxLines >= 0;
 
         private static bool IsValidLineHeight(double lineHeight) => double.IsNaN(lineHeight) || lineHeight > 0;
+
+        protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
+        {
+            base.OnPropertyChanged(change);
+
+            switch (change.Property.Name)
+            {
+                case nameof (FontSize):
+                case nameof (FontWeight):
+                case nameof (FontStyle):
+                case nameof (FontFamily):
+
+                case nameof (TextWrapping):
+                case nameof (TextTrimming):
+                case nameof (TextAlignment):
+                case nameof (FlowDirection):
+
+                case nameof (Padding):
+                case nameof (LineHeight):
+                case nameof (MaxLines):
+
+                case nameof (Text):
+                case nameof (TextDecorations):
+                case nameof (Foreground):
+                {
+                    InvalidateTextLayout();
+                    break;
+                }
+            }
+        }
     }
 }

src/Avalonia.Controls/TextBox.cs

@@ -14,6 +14,8 @@ using Avalonia.Data;
 using Avalonia.Layout;
 using Avalonia.Utilities;
 using Avalonia.Controls.Metadata;
+using Avalonia.Media.TextFormatting;
+using Avalonia.Media.TextFormatting.Unicode;
 
 namespace Avalonia.Controls
 {
@@ -250,6 +252,7 @@ namespace Avalonia.Controls
             {
                 value = CoerceCaretIndex(value);
                 SetAndRaise(CaretIndexProperty, ref _caretIndex, value);
+
                 UndoRedoState state;
                 if (IsUndoEnabled && _undoRedoHelper.TryGetLastState(out state) && state.Text == Text)
                     _undoRedoHelper.UpdateLastState();
@@ -301,7 +304,8 @@ namespace Avalonia.Controls
                 {
                     UpdateCommandStates();
                 }
-                if (SelectionStart == SelectionEnd)
+                
+                if (value == SelectionEnd)
                 {
                     CaretIndex = SelectionStart;
                 }
@@ -319,13 +323,15 @@ namespace Avalonia.Controls
             {
                 value = CoerceCaretIndex(value);
                 var changed = SetAndRaise(SelectionEndProperty, ref _selectionEnd, value);
+                
                 if (changed)
                 {
                     UpdateCommandStates();
                 }
-                if (SelectionStart == SelectionEnd)
+
+                if (value == SelectionStart)
                 {
-                    CaretIndex = SelectionEnd;
+                    CaretIndex = value;
                 }
             }
         }
@@ -345,6 +351,7 @@ namespace Avalonia.Controls
                 if (!_ignoreTextChanges)
                 {
                     var caretIndex = CaretIndex;
+                    
                     SelectionStart = CoerceCaretIndex(SelectionStart, value);
                     SelectionEnd = CoerceCaretIndex(SelectionEnd, value);
                     CaretIndex = CoerceCaretIndex(caretIndex, value);
@@ -533,13 +540,27 @@ namespace Avalonia.Controls
         protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         {
             _presenter = e.NameScope.Get<TextPresenter>("PART_TextPresenter");
+        }
+
+        protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnAttachedToVisualTree(e);
+            
             _imClient.SetPresenter(_presenter, this);
+            
             if (IsFocused)
             {
                 _presenter?.ShowCaret();
             }
         }
 
+        protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+        {
+            base.OnDetachedFromVisualTree(e);
+            
+            _imClient.SetPresenter(null, null);
+        }
+
         protected override void OnPropertyChanged<T>(AvaloniaPropertyChangedEventArgs<T> change)
         {
             base.OnPropertyChanged(change);
@@ -631,9 +652,8 @@ namespace Avalonia.Controls
             _selectedTextChangesMadeSinceLastUndoSnapshot++;
             SnapshotUndoRedo(ignoreChangeCount: false);
 
-            string text = Text ?? string.Empty;
-            int caretIndex = CaretIndex;
-            int newLength = input.Length + text.Length - Math.Abs(SelectionStart - SelectionEnd);
+            var text = Text ?? string.Empty;
+            var newLength = input.Length + text.Length - Math.Abs(SelectionStart - SelectionEnd);
 
             if (MaxLength > 0 && newLength > MaxLength)
             {
@@ -649,11 +669,11 @@ namespace Avalonia.Controls
                 try
                 {
                     DeleteSelection(false);
-                    caretIndex = CaretIndex;
+                    var caretIndex = CaretIndex;
                     text = Text ?? string.Empty;
                     SetTextInternal(text.Substring(0, caretIndex) + input + text.Substring(caretIndex));
-                    CaretIndex += input.Length;
                     ClearSelection();
+                    
                     if (IsUndoEnabled)
                     {
                         _undoRedoHelper.DiscardRedo();
@@ -663,6 +683,8 @@ namespace Avalonia.Controls
                     {
                         RaisePropertyChanged(TextProperty, oldText, _text);
                     }
+                    
+                    CaretIndex = caretIndex + input.Length;
                 }
                 finally
                 {
@@ -684,6 +706,7 @@ namespace Avalonia.Controls
         public async void Cut()
         {
             var text = GetSelection();
+
             if (string.IsNullOrEmpty(text))
             {
                 return;
@@ -703,6 +726,7 @@ namespace Avalonia.Controls
         public async void Copy()
         {
             var text = GetSelection();
+
             if (string.IsNullOrEmpty(text))
             {
                 return;
@@ -739,11 +763,16 @@ namespace Avalonia.Controls
 
         protected override void OnKeyDown(KeyEventArgs e)
         {
-            string text = Text ?? string.Empty;
-            int caretIndex = CaretIndex;
-            bool movement = false;
-            bool selection = false;
-            bool handled = false;
+            if (_presenter == null)
+            {
+                return;
+            }
+            
+            var text = Text ?? string.Empty;
+            var caretIndex = CaretIndex;
+            var movement = false;
+            var selection = false;
+            var handled = false;
             var modifiers = e.KeyModifiers;
 
             var keymap = AvaloniaLocator.Current.GetService<PlatformHotkeyConfiguration>();
@@ -884,46 +913,85 @@ namespace Avalonia.Controls
                         break;
 
                     case Key.Up:
-                        movement = MoveVertical(-1);
+                    {
                         selection = DetectSelection();
-                        break;
+                        
+                        _presenter.MoveCaretVertical(LogicalDirection.Backward);
+                        
+                        if (caretIndex != _presenter.CaretIndex)
+                        {
+                            movement = true;
+                        }
 
+                        if (selection)
+                        {
+                            SelectionEnd = _presenter.CaretIndex;
+                        }
+                        
+                        break;
+                    }
                     case Key.Down:
-                        movement = MoveVertical(1);
+                    {
                         selection = DetectSelection();
+                        
+                        _presenter?.MoveCaretVertical();
+                        
+                        if (caretIndex != _presenter.CaretIndex)
+                        {
+                            movement = true;
+                        }
+  
+                        if (selection)
+                        {
+                            SelectionEnd = _presenter.CaretIndex;
+                        }
+                        
                         break;
-
+                    }
                     case Key.Back:
+                    {
                         SnapshotUndoRedo();
+                        
                         if (hasWholeWordModifiers && SelectionStart == SelectionEnd)
                         {
                             SetSelectionForControlBackspace();
                         }
 
-                        if (!DeleteSelection() && CaretIndex > 0)
+                        if (!DeleteSelection() && caretIndex > 0)
                         {
-                            var removedCharacters = 1;
-                            // handle deleting /r/n
-                            // you don't ever want to leave a dangling /r around. So, if deleting /n, check to see if 
-                            // a /r should also be deleted.
-                            if (CaretIndex > 1 &&
-                                text[CaretIndex - 1] == '\n' &&
-                                text[CaretIndex - 2] == '\r')
+                            var removedCharacters = 0;
+                            
+                            // \r\n needs special treatment here
+                            if (caretIndex - 1 > 0 && text[caretIndex - 1] == '\n' && text[caretIndex - 2] == '\r')
                             {
                                 removedCharacters = 2;
                             }
+                            else
+                            {
+                                Codepoint.ReadAt(text.AsMemory(), caretIndex - 1, out removedCharacters);
+                            }
+
+                            if (removedCharacters == 0)
+                            {
+                                return;
+                            }
+
+                            var length = Math.Max(0, caretIndex - removedCharacters);
 
-                            SetTextInternal(text.Substring(0, caretIndex - removedCharacters) +
+                            SetTextInternal(text.Substring(0, length) +
                                             text.Substring(caretIndex));
-                            CaretIndex -= removedCharacters;
+                            
+                            CaretIndex = caretIndex - removedCharacters;
+                            
                             ClearSelection();
                         }
 
                         handled = true;
                         break;
-
+                    }
                     case Key.Delete:
                         SnapshotUndoRedo();
+                        
                         if (hasWholeWordModifiers && SelectionStart == SelectionEnd)
                         {
                             SetSelectionForControlDelete();
@@ -931,21 +999,18 @@ namespace Avalonia.Controls
 
                         if (!DeleteSelection() && caretIndex < text.Length)
                         {
-                            var removedCharacters = 1;
-                            // handle deleting /r/n
-                            // you don't ever want to leave a dangling /r around. So, if deleting /n, check to see if 
-                            // a /r should also be deleted.
-                            if (CaretIndex < text.Length - 1 &&
-                                text[caretIndex + 1] == '\n' &&
-                                text[caretIndex] == '\r')
-                            {
-                                removedCharacters = 2;
-                            }
+                            _presenter.MoveCaretHorizontal();
+
+                            var removedCharacters = Math.Max(0, _presenter.CaretIndex - caretIndex);
 
                             SetTextInternal(text.Substring(0, caretIndex) +
                                             text.Substring(caretIndex + removedCharacters));
+
+                            CaretIndex = caretIndex;
                         }
 
+                        SnapshotUndoRedo();
+
                         handled = true;
                         break;
 
@@ -983,11 +1048,7 @@ namespace Avalonia.Controls
                 }
             }
 
-            if (movement && selection)
-            {
-                SelectionEnd = CaretIndex;
-            }
-            else if (movement)
+            if (movement && !selection)
             {
                 ClearSelection();
             }
@@ -1000,19 +1061,28 @@ namespace Avalonia.Controls
 
         protected override void OnPointerPressed(PointerPressedEventArgs e)
         {
+            if (_presenter == null)
+            {
+                return;
+            }
+            
             var text = Text;
-
             var clickInfo = e.GetCurrentPoint(this);
-            if (text != null && clickInfo.Properties.IsLeftButtonPressed && !(clickInfo.Pointer?.Captured is Border))
+
+            if (text != null && clickInfo.Properties.IsLeftButtonPressed &&
+                !(clickInfo.Pointer?.Captured is Border))
             {
                 var point = e.GetPosition(_presenter);
-                var index = _presenter.GetCaretIndex(point);
-                var clickToSelect = index != CaretIndex && e.KeyModifiers.HasFlag(KeyModifiers.Shift);
 
-                if (!clickToSelect)
-                {
-                    CaretIndex = index;
-                }
+                var oldIndex = CaretIndex;
+
+                _presenter.MoveCaretToPoint(point);
+
+                var index = _presenter.CaretIndex;
+
+                var clickToSelect = e.KeyModifiers.HasFlag(KeyModifiers.Shift);
+
+                SetAndRaise(CaretIndexProperty, ref _caretIndex, index);
 
 #pragma warning disable CS0618 // Type or member is obsolete
                 switch (e.ClickCount)
@@ -1021,13 +1091,14 @@ namespace Avalonia.Controls
                     case 1:
                         if (clickToSelect)
                         {
-                            SelectionStart = Math.Min(index, CaretIndex);
-                            SelectionEnd = Math.Max(index, CaretIndex);
+                            SelectionStart = Math.Min(oldIndex, index);
+                            SelectionEnd = Math.Max(oldIndex, index);
                         }
                         else
                         {
                             SelectionStart = SelectionEnd = index;
                         }
+
                         break;
                     case 2:
                         if (!StringUtils.IsStartOfWord(text, index))
@@ -1049,8 +1120,13 @@ namespace Avalonia.Controls
 
         protected override void OnPointerMoved(PointerEventArgs e)
         {
+            if (_presenter == null)
+            {
+                return;
+            }
+            
             // selection should not change during pointer move if the user right clicks
-            if (_presenter != null && e.Pointer.Captured == _presenter && e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
+            if (e.Pointer.Captured == _presenter && e.GetCurrentPoint(this).Properties.IsLeftButtonPressed)
             {
                 var point = e.GetPosition(_presenter);
 
@@ -1058,32 +1134,45 @@ namespace Avalonia.Controls
                     MathUtilities.Clamp(point.X, 0, Math.Max(_presenter.Bounds.Width - 1, 0)),
                     MathUtilities.Clamp(point.Y, 0, Math.Max(_presenter.Bounds.Height - 1, 0)));
 
-                CaretIndex = SelectionEnd = _presenter.GetCaretIndex(point);
+                _presenter.MoveCaretToPoint(point);
+
+                SelectionEnd = _presenter.CaretIndex;
             }
         }
 
         protected override void OnPointerReleased(PointerReleasedEventArgs e)
         {
-            if (_presenter != null && e.Pointer.Captured == _presenter)
+            if (_presenter == null)
             {
-                if (e.InitialPressMouseButton == MouseButton.Right)
+                return;
+            }
+
+            if (e.Pointer.Captured != _presenter)
+            {
+                return;
+            }
+
+            if (e.InitialPressMouseButton == MouseButton.Right)
+            {
+                var point = e.GetPosition(_presenter);
+                    
+                _presenter.MoveCaretToPoint(point);
+                    
+                var caretIndex = _presenter.CaretIndex;
+
+                // see if mouse clicked inside current selection
+                // if it did not, we change the selection to where the user clicked
+                var firstSelection = Math.Min(SelectionStart, SelectionEnd);
+                var lastSelection = Math.Max(SelectionStart, SelectionEnd);
+                var didClickInSelection = SelectionStart != SelectionEnd &&
+                                          caretIndex >= firstSelection && caretIndex <= lastSelection;
+                if (!didClickInSelection)
                 {
-                    var point = e.GetPosition(_presenter);
-                    var caretIndex = _presenter.GetCaretIndex(point);
-
-                    // see if mouse clicked inside current selection
-                    // if it did not, we change the selection to where the user clicked
-                    var firstSelection = Math.Min(SelectionStart, SelectionEnd);
-                    var lastSelection = Math.Max(SelectionStart, SelectionEnd);
-                    var didClickInSelection = SelectionStart != SelectionEnd &&
-                        caretIndex >= firstSelection && caretIndex <= lastSelection;
-                    if (!didClickInSelection)
-                    {
-                        CaretIndex = SelectionEnd = SelectionStart = caretIndex;
-                    }
+                    CaretIndex = SelectionEnd = SelectionStart = caretIndex;
                 }
-                e.Pointer.Capture(null);
             }
+            
+            e.Pointer.Capture(null);
         }
 
         protected override void UpdateDataValidation<T>(AvaloniaProperty<T> property, BindingValue<T> value)
@@ -1127,106 +1216,46 @@ namespace Avalonia.Controls
             Text = string.Empty;
         }
 
-        private int DeleteCharacter(int index)
-        {
-            var start = index + 1;
-            var text = Text;
-            var c = text[index];
-            var result = 1;
-
-            if (c == '\n' && index > 0 && text[index - 1] == '\r')
-            {
-                --index;
-                ++result;
-            }
-            else if (c == '\r' && index < text.Length - 1 && text[index + 1] == '\n')
-            {
-                ++start;
-                ++result;
-            }
-
-            Text = text.Substring(0, index) + text.Substring(start);
-
-            return result;
-        }
-
         private void MoveHorizontal(int direction, bool wholeWord, bool isSelecting)
         {
             var text = Text ?? string.Empty;
-            var caretIndex = CaretIndex;
+            var selectionStart = SelectionStart;
 
             if (!wholeWord)
             {
-                if (SelectionStart != SelectionEnd && !isSelecting)
+                if (_presenter == null)
                 {
-                    var start = Math.Min(SelectionStart, SelectionEnd);
-                    var end = Math.Max(SelectionStart, SelectionEnd);
-                    CaretIndex = direction < 0 ? start : end;
                     return;
                 }
+                
+                _presenter.MoveCaretHorizontal(direction > 0 ? LogicalDirection.Forward : LogicalDirection.Backward);
 
-                var index = caretIndex + direction;
-
-                if (index < 0 || index > text.Length)
+                if (isSelecting)
                 {
-                    return;
-                }
-                else if (index == text.Length)
-                {
-                    CaretIndex = index;
-                    return;
-                }
-
-                var c = text[index];
-
-                if (direction > 0)
-                {
-                    CaretIndex += (c == '\r' && index < text.Length - 1 && text[index + 1] == '\n') ? 2 : 1;
+                    SelectionEnd = _presenter.CaretIndex;
                 }
                 else
                 {
-                    CaretIndex -= (c == '\n' && index > 0 && text[index - 1] == '\r') ? 2 : 1;
+                    SelectionStart = SelectionEnd = _presenter.CaretIndex;
                 }
             }
             else
             {
                 if (direction > 0)
                 {
-                    CaretIndex += StringUtils.NextWord(text, caretIndex) - caretIndex;
+                    var offset = StringUtils.NextWord(text, selectionStart) - selectionStart;
+                    
+                    CaretIndex += offset;
                 }
                 else
                 {
-                    CaretIndex += StringUtils.PreviousWord(text, caretIndex) - caretIndex;
+                    var offset = StringUtils.PreviousWord(text, selectionStart) - selectionStart;
+                    
+                    CaretIndex += offset;
                 }
             }
         }
 
-        private bool MoveVertical(int count)
-        {
-            if (_presenter is null)
-            {
-                return false;
-            }
-
-            var formattedText = _presenter.FormattedText;
-            var lines = formattedText.GetLines().ToList();
-            var caretIndex = CaretIndex;
-            var lineIndex = GetLine(caretIndex, lines) + count;
-
-            if (lineIndex >= 0 && lineIndex < lines.Count)
-            {
-                var line = lines[lineIndex];
-                var rect = formattedText.HitTestTextPosition(caretIndex);
-                var y = count < 0 ? rect.Y : rect.Bottom;
-                var point = new Point(rect.X, y + (count * (line.Height / 2)));
-                var hit = formattedText.HitTestPoint(point);
-                CaretIndex = hit.TextPosition + (hit.IsTrailing ? 1 : 0);
-                return true;
-            }
-
-            return false;
-        }
-
         private void MoveHome(bool document)
         {
             if (_presenter is null)
@@ -1243,17 +1272,17 @@ namespace Avalonia.Controls
             }
             else
             {
-                var lines = _presenter.FormattedText.GetLines();
+                var lines = _presenter.TextLayout.TextLines;
                 var pos = 0;
 
                 foreach (var line in lines)
                 {
-                    if (pos + line.Length > caretIndex || pos + line.Length == text.Length)
+                    if (pos + line.TextRange.Length > caretIndex || pos + line.TextRange.Length == text.Length)
                     {
                         break;
                     }
 
-                    pos += line.Length;
+                    pos += line.TextRange.Length;
                 }
 
                 caretIndex = pos;
@@ -1278,12 +1307,12 @@ namespace Avalonia.Controls
             }
             else
             {
-                var lines = _presenter.FormattedText.GetLines();
+                var lines = _presenter.TextLayout.TextLines;
                 var pos = 0;
 
                 foreach (var line in lines)
                 {
-                    pos += line.Length;
+                    pos += line.TextRange.Length;
 
                     if (pos > caretIndex)
                     {
@@ -1360,25 +1389,6 @@ namespace Avalonia.Controls
             return text.Substring(start, end - start);
         }
 
-        private int GetLine(int caretIndex, IList<FormattedTextLine> lines)
-        {
-            int pos = 0;
-            int i;
-
-            for (i = 0; i < lines.Count - 1; ++i)
-            {
-                var line = lines[i];
-                pos += line.Length;
-
-                if (pos > caretIndex)
-                {
-                    break;
-                }
-            }
-
-            return i;
-        }
-
         private void SetTextInternal(string value, bool raiseTextChanged = true)
         {
             if (raiseTextChanged)

src/Avalonia.Controls/TextBoxTextInputMethodClient.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Diagnostics;
 using Avalonia.Controls.Presenters;
 using Avalonia.Input;
 using Avalonia.Input.TextInput;
@@ -10,7 +11,7 @@ namespace Avalonia.Controls
     {
         private InputElement _parent;
         private TextPresenter _presenter;
-        private IDisposable _subscription;
+
         public Rect CursorRectangle
         {
             get
@@ -20,11 +21,15 @@ namespace Avalonia.Controls
                     return default;
                 }
                 var transform = _presenter.TransformToVisual(_parent);
+                
                 if (transform == null)
                 {
                     return default;
                 }
-                return _presenter.GetCursorRectangle().TransformToAABB(transform.Value);
+                
+                var rect =  _presenter.GetCursorRectangle().TransformToAABB(transform.Value);
+
+                return rect;
             }
         }
 
@@ -40,20 +45,25 @@ namespace Avalonia.Controls
         public string TextBeforeCursor => null;
         public string TextAfterCursor => null;
 
-        private void OnCaretIndexChanged(int index) => CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
+        private void OnCaretBoundsChanged(object sender, EventArgs e) => CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
 
 
         public void SetPresenter(TextPresenter presenter, InputElement parent)
         {
             _parent = parent;
-            _subscription?.Dispose();
-            _subscription = null;
+
+            if (_presenter != null)
+            {
+                _presenter.CaretBoundsChanged -= OnCaretBoundsChanged;
+            }
+           
             _presenter = presenter;
+            
             if (_presenter != null)
             {
-                _subscription = _presenter.GetObservable(TextPresenter.CaretIndexProperty)
-                    .Subscribe(OnCaretIndexChanged);
+                _presenter.CaretBoundsChanged += OnCaretBoundsChanged;
             }
+            
             TextViewVisualChanged?.Invoke(this, EventArgs.Empty);
             CursorRectangleChanged?.Invoke(this, EventArgs.Empty);
         }

src/Avalonia.Controls/TopLevel.cs

@@ -34,7 +34,7 @@ namespace Avalonia.Controls
         IStyleHost,
         ILogicalRoot,
         ITextInputMethodRoot,
-        IWeakSubscriber<ResourcesChangedEventArgs>
+        IWeakEventSubscriber<ResourcesChangedEventArgs>
     {
         /// <summary>
         /// Defines the <see cref="ClientSize"/> property.
@@ -74,6 +74,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<IBrush> TransparencyBackgroundFallbackProperty =
             AvaloniaProperty.Register<TopLevel, IBrush>(nameof(TransparencyBackgroundFallback), Brushes.White);
 
+        private static readonly WeakEvent<IResourceHost, ResourcesChangedEventArgs>
+            ResourcesChangedWeakEvent = WeakEvent.Register<IResourceHost, ResourcesChangedEventArgs>(
+                (s, h) => s.ResourcesChanged += h,
+                (s, h) => s.ResourcesChanged -= h
+            );
+
         private readonly IInputManager _inputManager;
         private readonly IAccessKeyHandler _accessKeyHandler;
         private readonly IKeyboardNavigationHandler _keyboardNavigationHandler;
@@ -128,6 +134,8 @@ namespace Avalonia.Controls
                     "Could not create window implementation: maybe no windowing subsystem was initialized?");
             }
 
+            impl = ValidatingToplevelImpl.Wrap(impl);
+            
             PlatformImpl = impl;
 
             _actualTransparencyLevel = PlatformImpl.TransparencyLevel;            
@@ -178,10 +186,7 @@ namespace Avalonia.Controls
 
             if (((IStyleHost)this).StylingParent is IResourceHost applicationResources)
             {
-                WeakSubscriptionManager.Subscribe(
-                    applicationResources,
-                    nameof(IResourceHost.ResourcesChanged),
-                    this);
+                ResourcesChangedWeakEvent.Subscribe(applicationResources, this);
             }
 
             impl.LostFocus += PlatformImpl_LostFocus;
@@ -286,7 +291,7 @@ namespace Avalonia.Controls
         /// <inheritdoc/>
         IMouseDevice IInputRoot.MouseDevice => PlatformImpl?.MouseDevice;
 
-        void IWeakSubscriber<ResourcesChangedEventArgs>.OnEvent(object sender, ResourcesChangedEventArgs e)
+        void IWeakEventSubscriber<ResourcesChangedEventArgs>.OnEvent(object sender, WeakEvent ev, ResourcesChangedEventArgs e)
         {
             ((ILogical)this).NotifyResourcesChanged(e);
         }
@@ -364,14 +369,15 @@ namespace Avalonia.Controls
             Renderer?.Dispose();
             Renderer = null;
             
+            (this as IInputRoot).MouseDevice?.TopLevelClosed(this);
+            PlatformImpl = null;
+            
             var logicalArgs = new LogicalTreeAttachmentEventArgs(this, this, null);
             ((ILogical)this).NotifyDetachedFromLogicalTree(logicalArgs);
 
             var visualArgs = new VisualTreeAttachmentEventArgs(this, this);
             OnDetachedFromVisualTreeCore(visualArgs);
-
-            (this as IInputRoot).MouseDevice?.TopLevelClosed(this);
-            PlatformImpl = null;
+            
             OnClosed(EventArgs.Empty);
 
             LayoutManager?.Dispose();

src/Avalonia.Controls/Utils/CollectionChangedEventManager.cs

@@ -83,7 +83,7 @@ namespace Avalonia.Controls.Utils
                 "Collection listener not registered for this collection/listener combination.");
         }
 
-        private class Entry : IWeakSubscriber<NotifyCollectionChangedEventArgs>, IDisposable
+        private class Entry : IWeakEventSubscriber<NotifyCollectionChangedEventArgs>, IDisposable
         {
             private INotifyCollectionChanged _collection;
 
@@ -91,23 +91,18 @@ namespace Avalonia.Controls.Utils
             {
                 _collection = collection;
                 Listeners = new List<WeakReference<ICollectionChangedListener>>();
-                WeakSubscriptionManager.Subscribe(
-                    _collection,
-                    nameof(INotifyCollectionChanged.CollectionChanged),
-                    this);
+                WeakEvents.CollectionChanged.Subscribe(_collection, this);
             }
 
             public List<WeakReference<ICollectionChangedListener>> Listeners { get; }
 
             public void Dispose()
             {
-                WeakSubscriptionManager.Unsubscribe(
-                    _collection,
-                    nameof(INotifyCollectionChanged.CollectionChanged),
-                    this);
+                WeakEvents.CollectionChanged.Unsubscribe(_collection, this);
             }
 
-            void IWeakSubscriber<NotifyCollectionChangedEventArgs>.OnEvent(object? sender, NotifyCollectionChangedEventArgs e)
+            void IWeakEventSubscriber<NotifyCollectionChangedEventArgs>.
+                OnEvent(object? notifyCollectionChanged, WeakEvent ev, NotifyCollectionChangedEventArgs e)
             {
                 static void Notify(
                     INotifyCollectionChanged incc,

src/Avalonia.Controls/Utils/StringUtils.cs

@@ -1,4 +1,5 @@
 using System.Globalization;
+using Avalonia.Media.TextFormatting.Unicode;
 
 namespace Avalonia.Controls.Utils
 {
@@ -23,26 +24,38 @@ namespace Avalonia.Controls.Utils
                 return false;
             }
 
+            var codepoint = new Codepoint(text[index]);
+
             // A 'word' starts with an AlphaNumeric or some punctuation symbols immediately
             // preceeded by lwsp.
-            if (index > 0 && !char.IsWhiteSpace(text[index - 1]))
+            if (index > 0)
             {
-                return false;
+                var previousCodepoint = new Codepoint(text[index - 1]);
+
+                if (!previousCodepoint.IsWhiteSpace)
+                {
+                    return false;
+                }
+
+                if (previousCodepoint.IsBreakChar)
+                {
+                    return true;
+                }
             }
 
-            switch (CharUnicodeInfo.GetUnicodeCategory(text[index]))
+            switch (codepoint.GeneralCategory)
             {
-                case UnicodeCategory.LowercaseLetter:
-                case UnicodeCategory.TitlecaseLetter:
-                case UnicodeCategory.UppercaseLetter:
-                case UnicodeCategory.DecimalDigitNumber:
-                case UnicodeCategory.LetterNumber:
-                case UnicodeCategory.OtherNumber:
-                case UnicodeCategory.DashPunctuation:
-                case UnicodeCategory.InitialQuotePunctuation:
-                case UnicodeCategory.OpenPunctuation:
-                case UnicodeCategory.CurrencySymbol:
-                case UnicodeCategory.MathSymbol:
+                case GeneralCategory.LowercaseLetter:
+                case GeneralCategory.TitlecaseLetter:
+                case GeneralCategory.UppercaseLetter:
+                case GeneralCategory.DecimalNumber:
+                case GeneralCategory.LetterNumber:
+                case GeneralCategory.OtherNumber:
+                case GeneralCategory.DashPunctuation:
+                case GeneralCategory.InitialPunctuation:
+                case GeneralCategory.OpenPunctuation:
+                case GeneralCategory.CurrencySymbol:
+                case GeneralCategory.MathSymbol:
                     return true;
 
                 // TODO: How do you do this in .NET?
@@ -56,6 +69,11 @@ namespace Avalonia.Controls.Utils
 
         public static int PreviousWord(string text, int cursor)
         {
+            if (string.IsNullOrEmpty(text))
+            {
+                return 0;
+            }
+            
             int begin;
             int i;
             int cr;
@@ -107,7 +125,12 @@ namespace Avalonia.Controls.Utils
 
             cr = LineEnd(text, cursor);
 
-            if (cr < text.Length && text[cr] == '\r' && text[cr + 1] == '\n')
+            if (cursor >= text.Length)
+            {
+                return cursor;
+            }
+            
+            if (cr < text.Length && text[cr] == '\r' && cr + 1 < text.Length && text[cr + 1] == '\n')
             {
                 lf = cr + 1;
             }

src/Avalonia.Controls/ValidatingToplevel.cs

@@ -0,0 +1,344 @@
+using System;
+using System.Collections.Generic;
+using Avalonia.Controls.Platform;
+using Avalonia.Controls.Primitives.PopupPositioning;
+using Avalonia.Input;
+using Avalonia.Input.Raw;
+using Avalonia.Input.TextInput;
+using Avalonia.Platform;
+using Avalonia.Rendering;
+
+namespace Avalonia.Controls;
+
+internal class ValidatingToplevelImpl : ITopLevelImpl, ITopLevelImplWithNativeControlHost,
+    ITopLevelImplWithNativeMenuExporter, ITopLevelImplWithTextInputMethod
+{
+    private readonly ITopLevelImpl _impl;
+    private bool _disposed;
+
+    public ValidatingToplevelImpl(ITopLevelImpl impl)
+    {
+        _impl = impl ?? throw new InvalidOperationException(
+            "Could not create TopLevel implementation: maybe no windowing subsystem was initialized?");
+    }
+
+    public void Dispose()
+    {
+        _disposed = true;
+        _impl.Dispose();
+    }
+
+    protected void CheckDisposed()
+    {
+        if (_disposed)
+            throw new ObjectDisposedException(_impl.GetType().FullName);
+    }
+
+    protected ITopLevelImpl Inner
+    {
+        get
+        {
+            CheckDisposed();
+            return _impl;
+        }
+    }
+
+    public static ITopLevelImpl Wrap(ITopLevelImpl impl)
+    {
+#if DEBUG
+        if (impl is ValidatingToplevelImpl)
+            return impl;
+        return new ValidatingToplevelImpl(impl);
+#else
+        return impl;
+#endif
+    }
+
+    public Size ClientSize => Inner.ClientSize;
+    public Size? FrameSize => Inner.FrameSize;
+    public double RenderScaling => Inner.RenderScaling;
+    public IEnumerable<object> Surfaces => Inner.Surfaces;
+
+    public Action<RawInputEventArgs> Input
+    {
+        get => Inner.Input;
+        set => Inner.Input = value;
+    }
+
+    public Action<Rect> Paint
+    {
+        get => Inner.Paint;
+        set => Inner.Paint = value;
+    }
+
+    public Action<Size, PlatformResizeReason> Resized
+    {
+        get => Inner.Resized;
+        set => Inner.Resized = value;
+    }
+
+    public Action<double> ScalingChanged
+    {
+        get => Inner.ScalingChanged;
+        set => Inner.ScalingChanged = value;
+    }
+
+    public Action<WindowTransparencyLevel> TransparencyLevelChanged
+    {
+        get => Inner.TransparencyLevelChanged;
+        set => Inner.TransparencyLevelChanged = value;
+    }
+
+    public IRenderer CreateRenderer(IRenderRoot root) => Inner.CreateRenderer(root);
+
+    public void Invalidate(Rect rect) => Inner.Invalidate(rect);
+
+    public void SetInputRoot(IInputRoot inputRoot) => Inner.SetInputRoot(inputRoot);
+
+    public Point PointToClient(PixelPoint point) => Inner.PointToClient(point);
+
+    public PixelPoint PointToScreen(Point point) => Inner.PointToScreen(point);
+
+    public void SetCursor(ICursorImpl cursor) => Inner.SetCursor(cursor);
+
+    public Action Closed
+    {
+        get => Inner.Closed;
+        set => Inner.Closed = value;
+    }
+
+    public Action LostFocus
+    {
+        get => Inner.LostFocus;
+        set => Inner.LostFocus = value;
+    }
+
+    // Exception: for some reason we are notifying platform mouse device from TopLevel.cs
+    public IMouseDevice MouseDevice => _impl.MouseDevice;
+    public IPopupImpl CreatePopup() => Inner.CreatePopup();
+
+    public void SetTransparencyLevelHint(WindowTransparencyLevel transparencyLevel) =>
+        Inner.SetTransparencyLevelHint(transparencyLevel);
+
+
+    public WindowTransparencyLevel TransparencyLevel => Inner.TransparencyLevel;
+    public AcrylicPlatformCompensationLevels AcrylicCompensationLevels => Inner.AcrylicCompensationLevels;
+    public INativeControlHostImpl NativeControlHost => (Inner as ITopLevelImplWithNativeControlHost)?.NativeControlHost;
+
+    public ITopLevelNativeMenuExporter NativeMenuExporter =>
+        (Inner as ITopLevelImplWithNativeMenuExporter)?.NativeMenuExporter;
+
+    public ITextInputMethodImpl TextInputMethod => (Inner as ITopLevelImplWithTextInputMethod)?.TextInputMethod;
+}
+
+internal class ValidatingWindowBaseImpl : ValidatingToplevelImpl, IWindowBaseImpl
+{
+    private readonly IWindowBaseImpl _impl;
+
+    public ValidatingWindowBaseImpl(IWindowBaseImpl impl) : base(impl)
+    {
+        _impl = impl;
+    }
+
+    protected new IWindowBaseImpl Inner
+    {
+        get
+        {
+            CheckDisposed();
+            return _impl;
+        }
+    }
+    
+    public static IWindowBaseImpl Wrap(IWindowBaseImpl impl)
+    {
+#if DEBUG
+        if (impl is ValidatingToplevelImpl)
+            return impl;
+        return new ValidatingWindowBaseImpl(impl);
+#else
+        return impl;
+#endif
+    }
+
+    public void Show(bool activate, bool isDialog) => Inner.Show(activate, isDialog);
+
+    public void Hide() => Inner.Hide();
+
+    public double DesktopScaling => Inner.DesktopScaling;
+    public PixelPoint Position => Inner.Position;
+
+    public Action<PixelPoint> PositionChanged
+    {
+        get => Inner.PositionChanged;
+        set => Inner.PositionChanged = value;
+    }
+
+    public void Activate() => Inner.Activate();
+
+    public Action Deactivated
+    {
+        get => Inner.Deactivated;
+        set => Inner.Deactivated = value;
+    }
+
+    public Action Activated
+    {
+        get => Inner.Activated;
+        set => Inner.Activated = value;
+    }
+
+    public IPlatformHandle Handle => Inner.Handle;
+    public Size MaxAutoSizeHint => Inner.MaxAutoSizeHint;
+    public void SetTopmost(bool value) => Inner.SetTopmost(value);
+    public IScreenImpl Screen => Inner.Screen;
+}
+
+internal class ValidatingWindowImpl : ValidatingWindowBaseImpl, IWindowImpl
+{
+    private readonly IWindowImpl _impl;
+
+    public ValidatingWindowImpl(IWindowImpl impl) : base(impl)
+    {
+        _impl = impl;
+    }
+
+    protected new IWindowImpl Inner
+    {
+        get
+        {
+            CheckDisposed();
+            return _impl;
+        }
+    }
+    
+    public static IWindowImpl Unwrap(IWindowImpl impl)
+    {
+        if (impl is ValidatingWindowImpl v)
+            return v.Inner;
+        return impl;
+    }
+
+    public static IWindowImpl Wrap(IWindowImpl impl)
+    {
+#if DEBUG
+        if (impl is ValidatingToplevelImpl)
+            return impl;
+        return new ValidatingWindowImpl(impl);
+#else
+        return impl;
+#endif
+    }
+
+    public WindowState WindowState
+    {
+        get => Inner.WindowState;
+        set => Inner.WindowState = value;
+    }
+
+    public Action<WindowState> WindowStateChanged
+    {
+        get => Inner.WindowStateChanged;
+        set => Inner.WindowStateChanged = value;
+    }
+
+    public void SetTitle(string title) => Inner.SetTitle(title);
+
+    public void SetParent(IWindowImpl parent)
+    {
+        //Workaround. SetParent will cast IWindowImpl to WindowImpl but  ValidatingWindowImpl isn't actual WindowImpl so it will fail with InvalidCastException.
+        if (parent is ValidatingWindowImpl validatingToplevelImpl)
+        {
+            Inner.SetParent(validatingToplevelImpl.Inner);
+        }
+        else
+        {
+            Inner.SetParent(parent);
+        }
+    }
+
+    public void SetEnabled(bool enable) => Inner.SetEnabled(enable);
+
+    public Action GotInputWhenDisabled
+    {
+        get => Inner.GotInputWhenDisabled;
+        set => Inner.GotInputWhenDisabled = value;
+    }
+
+    public void SetSystemDecorations(SystemDecorations enabled) => Inner.SetSystemDecorations(enabled);
+
+    public void SetIcon(IWindowIconImpl icon) => Inner.SetIcon(icon);
+
+    public void ShowTaskbarIcon(bool value) => Inner.ShowTaskbarIcon(value);
+
+    public void CanResize(bool value) => Inner.CanResize(value);
+
+    public Func<bool> Closing
+    {
+        get => Inner.Closing;
+        set => Inner.Closing = value;
+    }
+
+    public bool IsClientAreaExtendedToDecorations => Inner.IsClientAreaExtendedToDecorations;
+
+    public Action<bool> ExtendClientAreaToDecorationsChanged
+    {
+        get => Inner.ExtendClientAreaToDecorationsChanged;
+        set => Inner.ExtendClientAreaToDecorationsChanged = value;
+    }
+
+    public bool NeedsManagedDecorations => Inner.NeedsManagedDecorations;
+    public Thickness ExtendedMargins => Inner.ExtendedMargins;
+    public Thickness OffScreenMargin => Inner.OffScreenMargin;
+    public void BeginMoveDrag(PointerPressedEventArgs e) => Inner.BeginMoveDrag(e);
+
+    public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e) => Inner.BeginResizeDrag(edge, e);
+
+    public void Resize(Size clientSize, PlatformResizeReason reason) =>
+        Inner.Resize(clientSize, reason);
+
+    public void Move(PixelPoint point) => Inner.Move(point);
+
+    public void SetMinMaxSize(Size minSize, Size maxSize) => Inner.SetMinMaxSize(minSize, maxSize);
+
+    public void SetExtendClientAreaToDecorationsHint(bool extendIntoClientAreaHint) =>
+        Inner.SetExtendClientAreaToDecorationsHint(extendIntoClientAreaHint);
+
+    public void SetExtendClientAreaChromeHints(ExtendClientAreaChromeHints hints) =>
+        Inner.SetExtendClientAreaChromeHints(hints);
+
+    public void SetExtendClientAreaTitleBarHeightHint(double titleBarHeight) =>
+        Inner.SetExtendClientAreaTitleBarHeightHint(titleBarHeight);
+}
+
+internal class ValidatingPopupImpl : ValidatingWindowBaseImpl, IPopupImpl
+{
+    private readonly IPopupImpl _impl;
+
+    public ValidatingPopupImpl(IPopupImpl impl) : base(impl)
+    {
+        _impl = impl;
+    }
+
+    protected new IPopupImpl Inner
+    {
+        get
+        {
+            CheckDisposed();
+            return _impl;
+        }
+    }
+    
+    public static IPopupImpl Wrap(IPopupImpl impl)
+    {
+#if DEBUG
+        if (impl is ValidatingToplevelImpl)
+            return impl;
+        return new ValidatingPopupImpl(impl);
+#else
+        return impl;
+#endif
+    }
+
+    public IPopupPositioner PopupPositioner => Inner.PopupPositioner;
+    public void SetWindowManagerAddShadowHint(bool enabled) => Inner.SetWindowManagerAddShadowHint(enabled);
+}

src/Avalonia.Controls/Window.cs

@@ -237,13 +237,14 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="impl">The window implementation.</param>
         public Window(IWindowImpl impl)
-            : base(impl)
+            : base(ValidatingWindowImpl.Wrap(impl))
         {
-            impl.Closing = HandleClosing;
-            impl.GotInputWhenDisabled = OnGotInputWhenDisabled;
-            impl.WindowStateChanged = HandleWindowStateChanged;
+            var wrapped = (IWindowImpl)base.PlatformImpl!;
+            wrapped.Closing = HandleClosing;
+            wrapped.GotInputWhenDisabled = OnGotInputWhenDisabled;
+            wrapped.WindowStateChanged = HandleWindowStateChanged;
             _maxPlatformClientSize = PlatformImpl?.MaxAutoSizeHint ?? default(Size);
-            impl.ExtendClientAreaToDecorationsChanged = ExtendClientAreaToDecorationsChanged;            
+            wrapped.ExtendClientAreaToDecorationsChanged = ExtendClientAreaToDecorationsChanged;            
             this.GetObservable(ClientSizeProperty).Skip(1).Subscribe(x => PlatformImpl?.Resize(x, PlatformResizeReason.Application));
 
             PlatformImpl?.ShowTaskbarIcon(ShowInTaskbar);

src/Avalonia.Controls/WindowBase.cs

@@ -57,12 +57,13 @@ namespace Avalonia.Controls
         {
         }
 
-        public WindowBase(IWindowBaseImpl impl, IAvaloniaDependencyResolver dependencyResolver) : base(impl, dependencyResolver)
+        public WindowBase(IWindowBaseImpl impl, IAvaloniaDependencyResolver dependencyResolver) : base(ValidatingWindowBaseImpl.Wrap(impl), dependencyResolver)
         {
             Screens = new Screens(PlatformImpl?.Screen);
-            impl.Activated = HandleActivated;
-            impl.Deactivated = HandleDeactivated;
-            impl.PositionChanged = HandlePositionChanged;
+            var wrapped = PlatformImpl!;
+            wrapped.Activated = HandleActivated;
+            wrapped.Deactivated = HandleDeactivated;
+            wrapped.PositionChanged = HandlePositionChanged;
         }
 
         /// <summary>

src/Avalonia.DesktopRuntime/ApiCompatBaseline.txt

@@ -0,0 +1,3 @@
+Compat issues with assembly Avalonia.DesktopRuntime:
+TypesMustExist : Type 'Avalonia.Shared.PlatformSupport.AssetLoader' does not exist in the implementation but it does exist in the contract.
+Total Issues: 1

src/Avalonia.DesktopRuntime/AppBuilder.cs

@@ -4,7 +4,7 @@ using System.Linq;
 using System.Reflection;
 using Avalonia.Controls;
 using Avalonia.Platform;
-using Avalonia.Shared.PlatformSupport;
+using Avalonia.PlatformSupport;
 
 namespace Avalonia
 {

src/Avalonia.DesktopRuntime/Avalonia.DesktopRuntime.csproj

@@ -8,6 +8,7 @@
       <ProjectReference Include="../Avalonia.Base/Avalonia.Base.csproj" />
       <ProjectReference Include="../Avalonia.Visuals/Avalonia.Visuals.csproj" />
       <ProjectReference Include="../Avalonia.Controls/Avalonia.Controls.csproj" />
+      <ProjectReference Include="../Avalonia.PlatformSupport/Avalonia.PlatformSupport.csproj" />
   </ItemGroup>
 
   <ItemGroup>
@@ -16,6 +17,5 @@
 
   <Import Project="..\..\build\NetCore.props" />
   <Import Project="..\..\build\NetFX.props" />
-  <Import Project="..\Shared\PlatformSupport\PlatformSupport.projitems" />
   <Import Project="..\..\build\ApiDiff.props" />
 </Project>

src/Avalonia.DesktopRuntime/RuntimeInfo.cs

@@ -1,40 +0,0 @@
-using System;
-using System.Runtime.InteropServices;
-using Avalonia.Platform;
-
-
-namespace Avalonia.Shared.PlatformSupport
-{
-    internal partial class StandardRuntimePlatform
-    {
-        private static readonly Lazy<RuntimePlatformInfo> Info = new Lazy<RuntimePlatformInfo>(() =>
-        {
-            OperatingSystemType os;
-            if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
-                os = OperatingSystemType.OSX;
-            else if(RuntimeInformation.IsOSPlatform(OSPlatform.Linux))
-                os = OperatingSystemType.Linux;
-            else if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
-                os = OperatingSystemType.WinNT;
-            else
-                throw new Exception("Unknown OS platform " + RuntimeInformation.OSDescription);
-
-            return new RuntimePlatformInfo
-            {
-#if NETCOREAPP2_0
-                IsCoreClr = true,
-#elif NET461
-                IsDotNetFramework = false,
-#endif
-                IsDesktop = true,
-                IsMono = false,
-                IsMobile = false,
-                IsUnix = os != OperatingSystemType.WinNT,
-                OperatingSystem = os,
-            };
-        });
-
-
-        public RuntimePlatformInfo GetRuntimeInfo() => Info.Value;
-    }
-}