From 42dd06cf966981f32c36c13623267a125b475b94 Mon Sep 17 00:00:00 2001
From: Tridy <genadij@outlook.com>
Date: Thu, 29 Aug 2019 13:28:05 +0200
Subject: [PATCH 01/11] added IsCancel to Button

Like pressing Enter triggers a button that has the property IsDefault set to true, pressing Escape should work on the button that has IsCancel set to true.
---
 src/Avalonia.Controls/Button.cs | 83 +++++++++++++++++++++++++++++++--
 1 file changed, 80 insertions(+), 3 deletions(-)

diff --git a/src/Avalonia.Controls/Button.cs b/src/Avalonia.Controls/Button.cs
index b09d3bddff..e7407201c4 100644
--- a/src/Avalonia.Controls/Button.cs
+++ b/src/Avalonia.Controls/Button.cs
@@ -64,6 +64,12 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<bool> IsDefaultProperty =
             AvaloniaProperty.Register<Button, bool>(nameof(IsDefault));
 
+        /// <summary>
+        /// Defines the <see cref="IsCancelProperty"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> IsCancelProperty =
+            AvaloniaProperty.Register<Button, bool>(nameof(IsCancel));
+
         /// <summary>
         /// Defines the <see cref="Click"/> event.
         /// </summary>
@@ -84,6 +90,7 @@ namespace Avalonia.Controls
             FocusableProperty.OverrideDefaultValue(typeof(Button), true);
             CommandProperty.Changed.Subscribe(CommandChanged);
             IsDefaultProperty.Changed.Subscribe(IsDefaultChanged);
+            IsCancelProperty.Changed.Subscribe(IsCancelChanged);
             PseudoClass<Button>(IsPressedProperty, ":pressed");
         }
 
@@ -142,6 +149,16 @@ namespace Avalonia.Controls
             set { SetValue(IsDefaultProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether the button is the Cancel button for the
+        /// window.
+        /// </summary>
+        public bool IsCancel
+        {
+            get { return GetValue(IsCancelProperty); }
+            set { SetValue(IsCancelProperty, value); }
+        }
+
         public bool IsPressed
         {
             get { return GetValue(IsPressedProperty); }
@@ -162,6 +179,13 @@ namespace Avalonia.Controls
                     ListenForDefault(inputElement);
                 }
             }
+            if (IsCancel)
+            {
+                if (e.Root is IInputElement inputElement)
+                {
+                    ListenForCancel(inputElement);
+                }
+            }
         }
 
         /// <inheritdoc/>
@@ -351,6 +375,28 @@ namespace Avalonia.Controls
             }
         }
 
+        /// <summary>
+        /// Called when the <see cref="IsCancel"/> property changes.
+        /// </summary>
+        /// <param name="e">The event args.</param>
+        private static void IsCancelChanged(AvaloniaPropertyChangedEventArgs e)
+        {
+            var button = e.Sender as Button;
+            var isCancel = (bool)e.NewValue;
+
+            if (button?.VisualRoot is IInputElement inputRoot)
+            {
+                if (isCancel)
+                {
+                    button.ListenForCancel(inputRoot);
+                }
+                else
+                {
+                    button.StopListeningForCancel(inputRoot);
+                }
+            }
+        }
+
         /// <summary>
         /// Called when the <see cref="ICommand.CanExecuteChanged"/> event fires.
         /// </summary>
@@ -373,7 +419,16 @@ namespace Avalonia.Controls
         /// <param name="root">The input root.</param>
         private void ListenForDefault(IInputElement root)
         {
-            root.AddHandler(KeyDownEvent, RootKeyDown);
+            root.AddHandler(KeyDownEvent, RootDefaultKeyDown);
+        }
+
+        /// <summary>
+        /// Starts listening for the Enter key when the button <see cref="IsCancel"/>.
+        /// </summary>
+        /// <param name="root">The input root.</param>
+        private void ListenForCancel(IInputElement root)
+        {
+            root.AddHandler(KeyDownEvent, RootCancelKeyDown);
         }
 
         /// <summary>
@@ -382,7 +437,16 @@ namespace Avalonia.Controls
         /// <param name="root">The input root.</param>
         private void StopListeningForDefault(IInputElement root)
         {
-            root.RemoveHandler(KeyDownEvent, RootKeyDown);
+            root.RemoveHandler(KeyDownEvent, RootDefaultKeyDown);
+        }
+
+        /// <summary>
+        /// Stops listening for the Escape key when the button is no longer <see cref="IsCancel"/>.
+        /// </summary>
+        /// <param name="root">The input root.</param>
+        private void StopListeningForCancel(IInputElement root)
+        {
+            root.RemoveHandler(KeyDownEvent, RootCancelKeyDown);
         }
 
         /// <summary>
@@ -390,12 +454,25 @@ namespace Avalonia.Controls
         /// </summary>
         /// <param name="sender">The event sender.</param>
         /// <param name="e">The event args.</param>
-        private void RootKeyDown(object sender, KeyEventArgs e)
+        private void RootDefaultKeyDown(object sender, KeyEventArgs e)
         {
             if (e.Key == Key.Enter && IsVisible && IsEnabled)
             {
                 OnClick();
             }
         }
+
+        /// <summary>
+        /// Called when a key is pressed on the input root and the button <see cref="IsCancel"/>.
+        /// </summary>
+        /// <param name="sender">The event sender.</param>
+        /// <param name="e">The event args.</param>
+        private void RootCancelKeyDown(object sender, KeyEventArgs e)
+        {
+            if (e.Key == Key.Escape && IsVisible && IsEnabled)
+            {
+                OnClick();
+            }
+        }
     }
 }

From cd90cf86e7ff39472deab8b9ea775e79de5ef39f Mon Sep 17 00:00:00 2001
From: Genadij Trimailov <genadij@outlook.com>
Date: Thu, 29 Aug 2019 14:40:41 +0200
Subject: [PATCH 02/11] copy paste typo

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

diff --git a/src/Avalonia.Controls/Button.cs b/src/Avalonia.Controls/Button.cs
index e7407201c4..d39ea73828 100644
--- a/src/Avalonia.Controls/Button.cs
+++ b/src/Avalonia.Controls/Button.cs
@@ -423,7 +423,7 @@ namespace Avalonia.Controls
         }
 
         /// <summary>
-        /// Starts listening for the Enter key when the button <see cref="IsCancel"/>.
+        /// Starts listening for the Escape key when the button <see cref="IsCancel"/>.
         /// </summary>
         /// <param name="root">The input root.</param>
         private void ListenForCancel(IInputElement root)

From bc8a5af921ff9efbc46da652b3b928532016a30e Mon Sep 17 00:00:00 2001
From: ahopper <alan@samsararesearch.com>
Date: Wed, 4 Sep 2019 14:40:30 +0100
Subject: [PATCH 03/11] fix nested popups closing

---
 src/Avalonia.Controls/Primitives/Popup.cs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/Primitives/Popup.cs b/src/Avalonia.Controls/Primitives/Popup.cs
index 5ddbed5944..b3f86e8a76 100644
--- a/src/Avalonia.Controls/Primitives/Popup.cs
+++ b/src/Avalonia.Controls/Primitives/Popup.cs
@@ -450,7 +450,14 @@ namespace Avalonia.Controls.Primitives
 
         private bool IsChildOrThis(IVisual child)
         {
-            return _popupHost != null && ((IVisual)_popupHost).FindCommonVisualAncestor(child) == _popupHost;
+            IVisual root = child.GetVisualRoot();
+            while (root is IHostedVisualTreeRoot hostedRoot )
+            {
+                if (root == this._popupHost)
+                    return true;
+                root = hostedRoot.Host?.GetVisualRoot();
+            }
+            return false;
         }
         
         public bool IsInsidePopup(IVisual visual)

From 19f9729e867c5cb8f7ad9bd14131b0bb63e447b7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Pedro?= <jpedrolmail@gmail.com>
Date: Mon, 2 Sep 2019 20:44:54 +0100
Subject: [PATCH 04/11] Reduced array allocations.

---
 build/System.Memory.props                     |  2 +-
 .../Platform/SkiaPlatform/TopLevelImpl.cs     |  6 ++-
 .../Platform/Interop/Utf8Buffer.cs            | 23 +++++++---
 src/Avalonia.Controls/TreeView.cs             |  2 +-
 src/Avalonia.FreeDesktop/NativeMethods.cs     | 37 ++++++++++------
 src/Avalonia.X11/X11CursorFactory.cs          |  5 ++-
 src/Avalonia.X11/XI2Manager.cs                | 40 +++++++++++------
 .../FramebufferToplevelImpl.cs                |  7 ++-
 .../Avalonia.Direct2D1.csproj                 |  1 +
 src/Windows/Avalonia.Win32/DataObject.cs      | 25 ++++++++---
 src/Windows/Avalonia.Win32/DragSource.cs      |  7 ++-
 .../Interop/UnmanagedMethods.cs               |  6 +--
 src/Windows/Avalonia.Win32/OleDataObject.cs   | 43 +++++++++++--------
 src/Windows/Avalonia.Win32/WindowImpl.cs      | 12 +++---
 src/iOS/Avalonia.iOS/TopLevelImpl.cs          |  9 ++--
 15 files changed, 143 insertions(+), 82 deletions(-)

diff --git a/build/System.Memory.props b/build/System.Memory.props
index b328f7fd97..b36998a780 100644
--- a/build/System.Memory.props
+++ b/build/System.Memory.props
@@ -1,5 +1,5 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
-    <PackageReference Include="System.Memory" Version="4.5.1" />
+    <PackageReference Include="System.Memory" Version="4.5.3" />
   </ItemGroup>
 </Project>
diff --git a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
index 0d0d9db252..71706676d6 100644
--- a/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
+++ b/src/Android/Avalonia.Android/Platform/SkiaPlatform/TopLevelImpl.cs
@@ -15,10 +15,10 @@ using Avalonia.Rendering;
 namespace Avalonia.Android.Platform.SkiaPlatform
 {
     class TopLevelImpl : IAndroidView, ITopLevelImpl,  IFramebufferPlatformSurface
-
     {
         private readonly AndroidKeyboardEventsHelper<TopLevelImpl> _keyboardHelper;
         private readonly AndroidTouchEventsHelper<TopLevelImpl> _touchHelper;
+
         private ViewImpl _view;
 
         public TopLevelImpl(Context context, bool placeOnTop = false)
@@ -28,6 +28,8 @@ namespace Avalonia.Android.Platform.SkiaPlatform
             _touchHelper = new AndroidTouchEventsHelper<TopLevelImpl>(this, () => InputRoot,
                 p => GetAvaloniaPointFromEvent(p));
 
+            Surfaces = new object[] { this };
+
             MaxClientSize = new Size(_view.Resources.DisplayMetrics.WidthPixels,
                 _view.Resources.DisplayMetrics.HeightPixels);
         }
@@ -82,7 +84,7 @@ namespace Avalonia.Android.Platform.SkiaPlatform
 
         public IPlatformHandle Handle => _view;
 
-        public IEnumerable<object> Surfaces => new object[] {this};
+        public IEnumerable<object> Surfaces { get; }
 
         public IRenderer CreateRenderer(IRenderRoot root)
         {
diff --git a/src/Avalonia.Base/Platform/Interop/Utf8Buffer.cs b/src/Avalonia.Base/Platform/Interop/Utf8Buffer.cs
index dc7a3e5634..7117576b3b 100644
--- a/src/Avalonia.Base/Platform/Interop/Utf8Buffer.cs
+++ b/src/Avalonia.Base/Platform/Interop/Utf8Buffer.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -6,7 +7,7 @@ namespace Avalonia.Platform.Interop
 {
     public class Utf8Buffer : SafeHandle
     {
-        private GCHandle _gchandle;
+        private GCHandle _gcHandle;
         private byte[] _data;
             
         public Utf8Buffer(string s) : base(IntPtr.Zero, true)
@@ -14,8 +15,8 @@ namespace Avalonia.Platform.Interop
             if (s == null)
                 return;
             _data = Encoding.UTF8.GetBytes(s);
-            _gchandle = GCHandle.Alloc(_data, GCHandleType.Pinned);
-            handle = _gchandle.AddrOfPinnedObject();
+            _gcHandle = GCHandle.Alloc(_data, GCHandleType.Pinned);
+            handle = _gcHandle.AddrOfPinnedObject();
         }
 
         public int ByteLen => _data.Length;
@@ -26,7 +27,7 @@ namespace Avalonia.Platform.Interop
             {
                 handle = IntPtr.Zero;
                 _data = null;
-                _gchandle.Free();
+                _gcHandle.Free();
             }
             return true;
         }
@@ -40,10 +41,18 @@ namespace Avalonia.Platform.Interop
                 return null;
             int len;
             for (len = 0; pstr[len] != 0; len++) ;
-            var bytes = new byte[len];
-            Marshal.Copy(s, bytes, 0, len);
 
-            return Encoding.UTF8.GetString(bytes, 0, len);
+            var bytes = ArrayPool<byte>.Shared.Rent(len);
+
+            try
+            {
+                Marshal.Copy(s, bytes, 0, len);
+                return Encoding.UTF8.GetString(bytes, 0, len);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(bytes);
+            }
         }
     }
 }
diff --git a/src/Avalonia.Controls/TreeView.cs b/src/Avalonia.Controls/TreeView.cs
index eb68ba647e..cc47365214 100644
--- a/src/Avalonia.Controls/TreeView.cs
+++ b/src/Avalonia.Controls/TreeView.cs
@@ -50,7 +50,7 @@ namespace Avalonia.Controls
         public static readonly StyledProperty<SelectionMode> SelectionModeProperty =
             ListBox.SelectionModeProperty.AddOwner<TreeView>();
 
-        private static readonly IList Empty = new object[0];
+        private static readonly IList Empty = Array.Empty<object>();
         private object _selectedItem;
         private IList _selectedItems;
 
diff --git a/src/Avalonia.FreeDesktop/NativeMethods.cs b/src/Avalonia.FreeDesktop/NativeMethods.cs
index d9b6dce082..8bbda98bb2 100644
--- a/src/Avalonia.FreeDesktop/NativeMethods.cs
+++ b/src/Avalonia.FreeDesktop/NativeMethods.cs
@@ -1,12 +1,5 @@
-using System;
-using System.IO;
-using System.Linq;
-using System.Collections.Generic;
-using System.Collections.ObjectModel;
-using Avalonia.Controls.Platform;
-using System.Reactive.Disposables;
-using System.Reactive.Linq;
-using System.Text.RegularExpressions;
+using System.Buffers;
+using System.Diagnostics;
 using System.Runtime.InteropServices;
 using System.Text;
 
@@ -21,11 +14,27 @@ namespace Avalonia.FreeDesktop
 
         public static string ReadLink(string path)
         {
-            var symlink = Encoding.UTF8.GetBytes(path);
-            var result = new byte[4095];
-            readlink(symlink, result, result.Length);
-            var rawstr = Encoding.UTF8.GetString(result);
-            return rawstr.Substring(0, rawstr.IndexOf('\0'));
+            var symlinkMaxSize = Encoding.ASCII.GetMaxByteCount(path.Length);
+            var bufferSize = 4097; // PATH_MAX is (usually?) 4096, but we need to know if the result was truncated
+
+            var symlink = ArrayPool<byte>.Shared.Rent(symlinkMaxSize + 1);
+            var buffer = ArrayPool<byte>.Shared.Rent(bufferSize);
+
+            try
+            {
+                var symlinkSize = Encoding.UTF8.GetBytes(path, 0, path.Length, symlink, 0);
+                symlink[symlinkSize] = 0;
+
+                var size = readlink(symlink, buffer, bufferSize);
+                Debug.Assert(size < bufferSize); // if this fails, we need to increase the buffer size (dynamically?)
+
+                return Encoding.UTF8.GetString(buffer, 0, (int)size);
+            }
+            finally
+            {
+                ArrayPool<byte>.Shared.Return(symlink);
+                ArrayPool<byte>.Shared.Return(buffer);
+            }
         }
     }
 }
diff --git a/src/Avalonia.X11/X11CursorFactory.cs b/src/Avalonia.X11/X11CursorFactory.cs
index bed6f4693b..1c995475ae 100644
--- a/src/Avalonia.X11/X11CursorFactory.cs
+++ b/src/Avalonia.X11/X11CursorFactory.cs
@@ -8,6 +8,8 @@ namespace Avalonia.X11
 {
     class X11CursorFactory : IStandardCursorFactory
     {
+        private static readonly byte[] NullCursorData = new byte[] { 0 };
+
         private static IntPtr _nullCursor;
 
         private readonly IntPtr _display;
@@ -68,9 +70,8 @@ namespace Avalonia.X11
         private static IntPtr GetNullCursor(IntPtr display)
         {
             XColor color = new XColor();
-            byte[] data = new byte[] { 0 };
             IntPtr window = XLib.XRootWindow(display, 0);
-            IntPtr pixmap = XLib.XCreateBitmapFromData(display, window, data, 1, 1);
+            IntPtr pixmap = XLib.XCreateBitmapFromData(display, window, NullCursorData, 1, 1);
             return XLib.XCreatePixmapCursor(display, pixmap, pixmap, ref color, ref color, 0, 0);
         }
     }
diff --git a/src/Avalonia.X11/XI2Manager.cs b/src/Avalonia.X11/XI2Manager.cs
index cf75572601..6989d6d26d 100644
--- a/src/Avalonia.X11/XI2Manager.cs
+++ b/src/Avalonia.X11/XI2Manager.cs
@@ -1,18 +1,32 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using System.Runtime.InteropServices;
-using System.Text;
 using Avalonia.Input;
 using Avalonia.Input.Raw;
 using static Avalonia.X11.XLib;
+
 namespace Avalonia.X11
 {
     unsafe class XI2Manager
     {
+        private static readonly XiEventType[] DefaultEventTypes = new XiEventType[]
+        {
+            XiEventType.XI_Motion,
+            XiEventType.XI_ButtonPress,
+            XiEventType.XI_ButtonRelease
+        };
+
+        private static readonly XiEventType[] MultiTouchEventTypes = new XiEventType[]
+        {
+            XiEventType.XI_TouchBegin,
+            XiEventType.XI_TouchUpdate,
+            XiEventType.XI_TouchEnd
+        };
+
         private X11Info _x11;
         private bool _multitouch;
         private Dictionary<IntPtr, IXI2Client> _clients = new Dictionary<IntPtr, IXI2Client>();
+
         class DeviceInfo
         {
             public int Id { get; }
@@ -125,20 +139,18 @@ namespace Avalonia.X11
         public XEventMask AddWindow(IntPtr xid, IXI2Client window)
         {
             _clients[xid] = window;
-            var events = new List<XiEventType>
-            {
-                XiEventType.XI_Motion,
-                XiEventType.XI_ButtonPress,
-                XiEventType.XI_ButtonRelease
-            };
+
+            var eventsLength = DefaultEventTypes.Length;
 
             if (_multitouch)
-                events.AddRange(new[]
-                {
-                    XiEventType.XI_TouchBegin,
-                    XiEventType.XI_TouchUpdate,
-                    XiEventType.XI_TouchEnd
-                });
+                eventsLength += MultiTouchEventTypes.Length;
+
+            var events = new List<XiEventType>(eventsLength);
+
+            events.AddRange(DefaultEventTypes);
+
+            if (_multitouch)
+                events.AddRange(MultiTouchEventTypes);
 
             XiSelectEvents(_x11.Display, xid,
                 new Dictionary<int, List<XiEventType>> {[_pointerDevice.Id] = events});
diff --git a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
index 2dc112f3d3..9844cdc03b 100644
--- a/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
+++ b/src/Linux/Avalonia.LinuxFramebuffer/FramebufferToplevelImpl.cs
@@ -6,7 +6,6 @@ using Avalonia.LinuxFramebuffer.Input;
 using Avalonia.LinuxFramebuffer.Output;
 using Avalonia.Platform;
 using Avalonia.Rendering;
-using Avalonia.Threading;
 
 namespace Avalonia.LinuxFramebuffer
 {
@@ -14,6 +13,7 @@ namespace Avalonia.LinuxFramebuffer
     {
         private readonly IOutputBackend _outputBackend;
         private readonly IInputBackend _inputBackend;
+
         private bool _renderQueued;
         public IInputRoot InputRoot { get; private set; }
 
@@ -21,6 +21,9 @@ namespace Avalonia.LinuxFramebuffer
         {
             _outputBackend = outputBackend;
             _inputBackend = inputBackend;
+
+            Surfaces = new object[] { _outputBackend };
+
             Invalidate(default(Rect));
             _inputBackend.Initialize(this, e => Input?.Invoke(e));
         }
@@ -62,7 +65,7 @@ namespace Avalonia.LinuxFramebuffer
         public IPopupImpl CreatePopup() => null;
 
         public double Scaling => _outputBackend.Scaling;
-        public IEnumerable<object> Surfaces => new object[] {_outputBackend};
+        public IEnumerable<object> Surfaces { get; }
         public Action<RawInputEventArgs> Input { get; set; }
         public Action<Rect> Paint { get; set; }
         public Action<Size> Resized { get; set; }
diff --git a/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj b/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
index 16f2767096..458d8f9cbb 100644
--- a/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
+++ b/src/Windows/Avalonia.Direct2D1/Avalonia.Direct2D1.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
     <PackageId>Avalonia.Direct2D1</PackageId>
   </PropertyGroup>
   <ItemGroup>
diff --git a/src/Windows/Avalonia.Win32/DataObject.cs b/src/Windows/Avalonia.Win32/DataObject.cs
index e78a99cc03..6c1b4ef5d9 100644
--- a/src/Windows/Avalonia.Win32/DataObject.cs
+++ b/src/Windows/Avalonia.Win32/DataObject.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
@@ -254,9 +256,18 @@ namespace Avalonia.Win32
                 return WriteFileListToHGlobal(ref hGlobal, files);
             if (data is Stream stream)
             {
-                byte[] buffer = new byte[stream.Length - stream.Position];
-                stream.Read(buffer, 0, buffer.Length);
-                return WriteBytesToHGlobal(ref hGlobal, buffer);
+                var length = (int)(stream.Length - stream.Position);
+                var buffer = ArrayPool<byte>.Shared.Rent(length);
+
+                try
+                {
+                    stream.Read(buffer, 0, length);
+                    return WriteBytesToHGlobal(ref hGlobal, buffer.AsSpan(0, length));
+                }
+                finally
+                {
+                    ArrayPool<byte>.Shared.Return(buffer);
+                }
             }
             if (data is IEnumerable<byte> bytes)
             {
@@ -277,7 +288,7 @@ namespace Avalonia.Win32
             }
         }
 
-        private int WriteBytesToHGlobal(ref IntPtr hGlobal, byte[] data)
+        private unsafe int WriteBytesToHGlobal(ref IntPtr hGlobal, ReadOnlySpan<byte> data)
         {
             int required = data.Length;
             if (hGlobal == IntPtr.Zero)
@@ -287,10 +298,12 @@ namespace Avalonia.Win32
             if (required > available)
                 return STG_E_MEDIUMFULL;
 
-            IntPtr ptr = UnmanagedMethods.GlobalLock(hGlobal);
+            var ptr = UnmanagedMethods.GlobalLock(hGlobal);
+            Debug.Assert(ptr == hGlobal);
+
             try
             {
-                Marshal.Copy(data, 0, ptr, data.Length);
+                data.CopyTo(new Span<byte>((void*)ptr, data.Length));
                 return unchecked((int)UnmanagedMethods.HRESULT.S_OK);
             }
             finally
diff --git a/src/Windows/Avalonia.Win32/DragSource.cs b/src/Windows/Avalonia.Win32/DragSource.cs
index a8d74571a1..f74e59a8f8 100644
--- a/src/Windows/Avalonia.Win32/DragSource.cs
+++ b/src/Windows/Avalonia.Win32/DragSource.cs
@@ -17,9 +17,8 @@ namespace Avalonia.Win32
             DataObject dataObject = new DataObject(data);
             int allowed = (int)OleDropTarget.ConvertDropEffect(allowedEffects);
 
-            int[] finalEffect = new int[1];
-            UnmanagedMethods.DoDragDrop(dataObject, src, allowed, finalEffect);
-
-            return Task.FromResult(OleDropTarget.ConvertDropEffect((DropEffect)finalEffect[0]));}
+            UnmanagedMethods.DoDragDrop(dataObject, src, allowed, out var finalEffect);
+            return Task.FromResult(OleDropTarget.ConvertDropEffect((DropEffect)finalEffect));
+        }
     }
 }
diff --git a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
index 097aba6dc9..d37bec3334 100644
--- a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
+++ b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
@@ -1051,10 +1051,10 @@ namespace Avalonia.Win32.Interop
         public static extern bool GetMonitorInfo([In] IntPtr hMonitor, ref MONITORINFO lpmi);
 
         [DllImport("user32")]
-        public static extern bool GetTouchInputInfo(
+        public static extern unsafe bool GetTouchInputInfo(
             IntPtr hTouchInput,
             uint        cInputs,
-            [Out]TOUCHINPUT[] pInputs,
+            TOUCHINPUT* pInputs,
             int         cbSize
         );
         
@@ -1115,7 +1115,7 @@ namespace Avalonia.Win32.Interop
         public static extern int DragQueryFile(IntPtr hDrop, int iFile, StringBuilder lpszFile, int cch);
 
         [DllImport("ole32.dll", CharSet = CharSet.Auto, ExactSpelling = true, PreserveSig = false)]
-        internal static extern void DoDragDrop(IOleDataObject dataObject, IDropSource dropSource, int allowedEffects, int[] finalEffect);
+        internal static extern void DoDragDrop(IOleDataObject dataObject, IDropSource dropSource, int allowedEffects, out int finalEffect);
 
 
 
diff --git a/src/Windows/Avalonia.Win32/OleDataObject.cs b/src/Windows/Avalonia.Win32/OleDataObject.cs
index 70d651b2aa..f111fe0a6b 100644
--- a/src/Windows/Avalonia.Win32/OleDataObject.cs
+++ b/src/Windows/Avalonia.Win32/OleDataObject.cs
@@ -1,5 +1,7 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
@@ -86,15 +88,8 @@ namespace Avalonia.Win32
             return null;
         }
 
-        private bool IsSerializedObject(byte[] data)
-        {
-            if (data.Length < DataObject.SerializedObjectGUID.Length)
-                return false;
-            for (int i = 0; i < DataObject.SerializedObjectGUID.Length; i++)
-                if (data[i] != DataObject.SerializedObjectGUID[i])
-                    return false;
-            return true;
-        }
+        private static bool IsSerializedObject(ReadOnlySpan<byte> data) =>
+            data.StartsWith(DataObject.SerializedObjectGUID);
 
         private static IEnumerable<string> ReadFileNamesFromHGlobal(IntPtr hGlobal)
         {
@@ -148,21 +143,33 @@ namespace Avalonia.Win32
         private IEnumerable<string> GetDataFormatsCore()
         {
             var enumFormat = _wrapped.EnumFormatEtc(DATADIR.DATADIR_GET);
+
             if (enumFormat != null)
             {
                 enumFormat.Reset();
-                FORMATETC[] formats = new FORMATETC[1];
-                int[] fetched = { 1 };
-                while (fetched[0] > 0)
+                
+                var formats = ArrayPool<FORMATETC>.Shared.Rent(1);
+                var fetched = ArrayPool<int>.Shared.Rent(1);
+
+                try
                 {
-                    fetched[0] = 0;
-                    if (enumFormat.Next(1, formats, fetched) == 0 && fetched[0] > 0)
+                    do
                     {
-                        if (formats[0].ptd != IntPtr.Zero)
-                            Marshal.FreeCoTaskMem(formats[0].ptd);
-                        
-                        yield return ClipboardFormats.GetFormat(formats[0].cfFormat);
+                        fetched[0] = 0;
+                        if (enumFormat.Next(1, formats, fetched) == 0 && fetched[0] > 0)
+                        {
+                            if (formats[0].ptd != IntPtr.Zero)
+                                Marshal.FreeCoTaskMem(formats[0].ptd);
+
+                            yield return ClipboardFormats.GetFormat(formats[0].cfFormat);
+                        }
                     }
+                    while (fetched[0] > 0);
+                }
+                finally
+                {
+                    ArrayPool<FORMATETC>.Shared.Return(formats);
+                    ArrayPool<int>.Shared.Return(fetched);
                 }
             }
         }
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 9bd58c10bc..e8c3177ec5 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -5,7 +5,6 @@ using System;
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics.CodeAnalysis;
-using System.Reactive.Disposables;
 using System.Runtime.InteropServices;
 using Avalonia.Controls;
 using Avalonia.Input;
@@ -13,7 +12,6 @@ using Avalonia.Input.Raw;
 using Avalonia.OpenGL;
 using Avalonia.Platform;
 using Avalonia.Rendering;
-using Avalonia.Threading;
 using Avalonia.Win32.Input;
 using Avalonia.Win32.Interop;
 using static Avalonia.Win32.Interop.UnmanagedMethods;
@@ -430,7 +428,7 @@ namespace Avalonia.Win32
         }
         
         [SuppressMessage("Microsoft.StyleCop.CSharp.NamingRules", "SA1305:FieldNamesMustNotUseHungarianNotation", Justification = "Using Win32 naming for consistency.")]
-        protected virtual IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
+        protected virtual unsafe IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
         {
             bool unicode = UnmanagedMethods.IsWindowUnicode(hWnd);
 
@@ -637,8 +635,12 @@ namespace Avalonia.Win32
                         new Point(0, 0), GetMouseModifiers(wParam));
                     break;
                 case WindowsMessage.WM_TOUCH:
-                    var touchInputs = new TOUCHINPUT[wParam.ToInt32()];
-                    if (GetTouchInputInfo(lParam, (uint)wParam.ToInt32(), touchInputs, Marshal.SizeOf<TOUCHINPUT>()))
+                    var touchInputCount = wParam.ToInt32();
+
+                    var pTouchInputs = stackalloc TOUCHINPUT[touchInputCount];
+                    var touchInputs = new Span<TOUCHINPUT>(pTouchInputs, touchInputCount);
+
+                    if (GetTouchInputInfo(lParam, (uint)touchInputCount, pTouchInputs, Marshal.SizeOf<TOUCHINPUT>()))
                     {
                         foreach (var touchInput in touchInputs)
                         {
diff --git a/src/iOS/Avalonia.iOS/TopLevelImpl.cs b/src/iOS/Avalonia.iOS/TopLevelImpl.cs
index a5342b227f..c5b6642982 100644
--- a/src/iOS/Avalonia.iOS/TopLevelImpl.cs
+++ b/src/iOS/Avalonia.iOS/TopLevelImpl.cs
@@ -16,14 +16,17 @@ namespace Avalonia.iOS
     [Adopts("UIKeyInput")]
     class TopLevelImpl : UIView, ITopLevelImpl, IFramebufferPlatformSurface
     {
-        private IInputRoot _inputRoot;
         private readonly KeyboardEventsHelper<TopLevelImpl> _keyboardHelper;
 
+        private IInputRoot _inputRoot;
+
         public TopLevelImpl()
         {
             _keyboardHelper = new KeyboardEventsHelper<TopLevelImpl>(this);
             AutoresizingMask = UIViewAutoresizing.All;
             _keyboardHelper.ActivateAutoShowKeyboard();
+
+            Surfaces = new object[] { this };
         }
 
         [Export("hasText")]
@@ -76,8 +79,8 @@ namespace Avalonia.iOS
         {
             //Not supported
         }
-        
-        public IEnumerable<object> Surfaces => new object[] { this };
+
+        public IEnumerable<object> Surfaces { get; }
         
         public override void TouchesEnded(NSSet touches, UIEvent evt)
         {

From 82992f86970ef617457393f2f26a044be5383c5c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mi=C5=82osz=20Kukla?= <milosz.kukla@gmail.com>
Date: Mon, 23 Sep 2019 02:24:57 +0200
Subject: [PATCH 05/11] Rename ResourceProviderExtensions to
 ResourceNodeExtensions

---
 ...{ResourceProviderExtensions.cs => ResourceNodeExtensions.cs} | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
 rename src/Avalonia.Styling/Controls/{ResourceProviderExtensions.cs => ResourceNodeExtensions.cs} (98%)

diff --git a/src/Avalonia.Styling/Controls/ResourceProviderExtensions.cs b/src/Avalonia.Styling/Controls/ResourceNodeExtensions.cs
similarity index 98%
rename from src/Avalonia.Styling/Controls/ResourceProviderExtensions.cs
rename to src/Avalonia.Styling/Controls/ResourceNodeExtensions.cs
index 01112eaf2c..19a16f86c4 100644
--- a/src/Avalonia.Styling/Controls/ResourceProviderExtensions.cs
+++ b/src/Avalonia.Styling/Controls/ResourceNodeExtensions.cs
@@ -3,7 +3,7 @@ using Avalonia.Reactive;
 
 namespace Avalonia.Controls
 {
-    public static class ResourceProviderExtensions
+    public static class ResourceNodeExtensions
     {
         /// <summary>
         /// Finds the specified resource by searching up the logical tree and then global styles.

From 5b15fe4b4114332ed91f8dce9d5867be484d86ee Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mi=C5=82osz=20Kukla?= <milosz.kukla@gmail.com>
Date: Sat, 28 Sep 2019 16:01:17 +0200
Subject: [PATCH 06/11] Allow to use object as a resource key in
 Static/DynamicResourceExtension

---
 .../MarkupExtensions/DynamicResourceExtension.cs              | 2 +-
 .../MarkupExtensions/StaticResourceExtension.cs               | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
index 0a9289bec9..5bdb0cc235 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/DynamicResourceExtension.cs
@@ -18,7 +18,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
         {
         }
 
-        public DynamicResourceExtension(string resourceKey)
+        public DynamicResourceExtension(object resourceKey)
         {
             ResourceKey = resourceKey;
         }
diff --git a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs
index d6b170ae9d..6d055e033f 100644
--- a/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs
+++ b/src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/StaticResourceExtension.cs
@@ -16,12 +16,12 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
         {
         }
 
-        public StaticResourceExtension(string resourceKey)
+        public StaticResourceExtension(object resourceKey)
         {
             ResourceKey = resourceKey;
         }
 
-        public string ResourceKey { get; set; }
+        public object ResourceKey { get; set; }
 
         public object ProvideValue(IServiceProvider serviceProvider)
         {

From 9a6cda66bcaa38fe58500320b5e16e71fcca07a2 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Sun, 29 Sep 2019 18:54:08 +0200
Subject: [PATCH 07/11] Add failing test for #2987

---
 .../Primitives/SelectingItemsControlTests.cs  | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
index 4e4d92afdc..8f27ebe853 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs
@@ -109,6 +109,28 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.True(items[1].IsSelected);
         }
 
+        [Fact]
+        public void Setting_SelectedIndex_During_Initialize_Should_Select_Item_When_AlwaysSelected_Is_Used()
+        {
+            var listBox = new ListBox
+            {
+                SelectionMode = SelectionMode.Single | SelectionMode.AlwaysSelected
+            };
+
+            listBox.BeginInit();
+
+            listBox.SelectedIndex = 1;
+            var items = new AvaloniaList<string>();
+            listBox.Items = items;
+            items.Add("A");
+            items.Add("B");
+            items.Add("C");
+
+            listBox.EndInit();
+
+            Assert.Equal("B", listBox.SelectedItem);
+        }
+
         [Fact]
         public void Setting_SelectedIndex_Before_ApplyTemplate_Should_Set_Item_IsSelected_True()
         {

From bcbe9c3dbd6e2eb824b9947d667096d98edbaca5 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Wed, 18 Sep 2019 19:01:48 +0200
Subject: [PATCH 08/11] Fix setting SelectedIndex in XAML

---
 .../Primitives/SelectingItemsControl.cs          | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index cc0c5f52be..761a3f3b3d 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -304,6 +304,11 @@ namespace Avalonia.Controls.Primitives
         {
             base.ItemsCollectionChanged(sender, e);
 
+            if (_updateCount > 0)
+            {
+                return;
+            }
+
             switch (e.Action)
             {
                 case NotifyCollectionChangedAction.Add:
@@ -1071,13 +1076,16 @@ namespace Avalonia.Controls.Primitives
 
         private void UpdateFinished()
         {
-            if (_updateSelectedIndex != int.MinValue)
+            if (_updateSelectedItem != null)
             {
-                SelectedIndex = _updateSelectedIndex;
+                SelectedItem = _updateSelectedItem;
             }
-            else if (_updateSelectedItem != null)
+            else
             {
-                SelectedItem = _updateSelectedItem;
+                if (ItemCount > 0)
+                {
+                    SelectedIndex = _updateSelectedIndex != int.MinValue ? _updateSelectedIndex : 0;
+                }
             }
         }
 

From b42126b9e35cc5ce404963584fee95bc7f1b77c3 Mon Sep 17 00:00:00 2001
From: Benedikt Schroeder <benedikt.schroeder@outlook.de>
Date: Wed, 18 Sep 2019 19:22:23 +0200
Subject: [PATCH 09/11] Properly reset SelectedIndex after the DataContext
 changed

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

diff --git a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
index 761a3f3b3d..a50175bdee 100644
--- a/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
+++ b/src/Avalonia.Controls/Primitives/SelectingItemsControl.cs
@@ -1082,7 +1082,11 @@ namespace Avalonia.Controls.Primitives
             }
             else
             {
-                if (ItemCount > 0)
+                if (ItemCount == 0 && SelectedIndex != -1)
+                {
+                    SelectedIndex = -1;
+                }
+                else
                 {
                     SelectedIndex = _updateSelectedIndex != int.MinValue ? _updateSelectedIndex : 0;
                 }

From ea68915de6fd4f3cf0bc21e056f24bf32cac1512 Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 1 Oct 2019 12:22:34 +0200
Subject: [PATCH 10/11] Added failing test for #2971.

And a passing test for normal TreeView.
---
 .../TreeViewTests.cs                          | 74 +++++++++++++++++++
 1 file changed, 74 insertions(+)

diff --git a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
index f51a50c0d5..6c9f0f4f57 100644
--- a/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/TreeViewTests.cs
@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
+using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Collections;
@@ -843,6 +844,54 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal(1, target.SelectedItems.Count);
         }
 
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set()
+        {
+            var tree = CreateTestTreeData();
+            var target = new TreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
+        [Fact]
+        public void TreeViewItems_Level_Should_Be_Set_For_Derived_TreeView()
+        {
+            var tree = CreateTestTreeData();
+            var target = new DerivedTreeView
+            {
+                Template = CreateTreeViewTemplate(),
+                Items = tree,
+            };
+
+            var visualRoot = new TestRoot();
+            visualRoot.Child = target;
+
+            CreateNodeDataTemplate(target);
+            ApplyTemplates(target);
+            ExpandAll(target);
+
+            Assert.Equal(0, GetItem(target, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 0).Level);
+            Assert.Equal(1, GetItem(target, 0, 1).Level);
+            Assert.Equal(1, GetItem(target, 0, 2).Level);
+            Assert.Equal(2, GetItem(target, 0, 1, 0).Level);
+        }
+
         private void ApplyTemplates(TreeView tree)
         {
             tree.ApplyTemplate();
@@ -862,6 +911,19 @@ namespace Avalonia.Controls.UnitTests
             }
         }
 
+        private TreeViewItem GetItem(TreeView target, params int[] indexes)
+        {
+            var c = (ItemsControl)target;
+
+            foreach (var index in indexes)
+            {
+                var item = ((IList)c.Items)[index];
+                c = (ItemsControl)target.ItemContainerGenerator.Index.ContainerFromItem(item);
+            }
+
+            return (TreeViewItem)c;
+        }
+
         private IList<Node> CreateTestTreeData()
         {
             return new AvaloniaList<Node>
@@ -929,6 +991,14 @@ namespace Avalonia.Controls.UnitTests
             });
         }
 
+        private void ExpandAll(TreeView tree)
+        {
+            foreach (var i in tree.ItemContainerGenerator.Containers)
+            {
+                tree.ExpandSubTree((TreeViewItem)i.ContainerControl);
+            }
+        }
+
         private List<string> ExtractItemHeader(TreeView tree, int level)
         {
             return ExtractItemContent(tree.Presenter.Panel, 0, level)
@@ -1019,5 +1089,9 @@ namespace Avalonia.Controls.UnitTests
                 return data is Node;
             }
         }
+
+        private class DerivedTreeView : TreeView
+        {
+        }
     }
 }

From a830d5b2d42a70acdd3ea3029e0593cc46868bea Mon Sep 17 00:00:00 2001
From: Steven Kirk <grokys@gmail.com>
Date: Tue, 1 Oct 2019 12:25:13 +0200
Subject: [PATCH 11/11] Don't test tree view item type by comparing GetType().

Fixes #2971.
---
 src/Avalonia.Controls/TreeViewItem.cs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Avalonia.Controls/TreeViewItem.cs b/src/Avalonia.Controls/TreeViewItem.cs
index e185bc227b..c7fd96b68a 100644
--- a/src/Avalonia.Controls/TreeViewItem.cs
+++ b/src/Avalonia.Controls/TreeViewItem.cs
@@ -173,7 +173,7 @@ namespace Avalonia.Controls
         {
             var result = 0;
 
-            while (logical != null && logical.GetType() != typeof(T))
+            while (logical != null && !(logical is T))
             {
                 ++result;
                 logical = logical.LogicalParent;