Merge branch 'master' into master

Avalonia.sln

@@ -222,9 +222,9 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Headless.Vnc", "sr
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.Markup.Xaml.Loader", "src\Markup\Avalonia.Markup.Xaml.Loader\Avalonia.Markup.Xaml.Loader.csproj", "{909A8CBD-7D0E-42FD-B841-022AD8925820}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.ReactiveUI.Events", "src\Avalonia.ReactiveUI.Events\Avalonia.ReactiveUI.Events.csproj", "{28F18757-C3E6-4BBE-A37D-11BA2AB9177C}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.ReactiveUI.Events", "src\Avalonia.ReactiveUI.Events\Avalonia.ReactiveUI.Events.csproj", "{28F18757-C3E6-4BBE-A37D-11BA2AB9177C}"
 EndProject
-Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Avalonia.ReactiveUI.Events.UnitTests", "tests\Avalonia.ReactiveUI.Events.UnitTests\Avalonia.ReactiveUI.Events.UnitTests.csproj", "{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Avalonia.ReactiveUI.Events.UnitTests", "tests\Avalonia.ReactiveUI.Events.UnitTests\Avalonia.ReactiveUI.Events.UnitTests.csproj", "{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}"
 EndProject
 Global
 	GlobalSection(SharedMSBuildProjectFiles) = preSolution
@@ -2040,6 +2040,30 @@ Global
 		{28F18757-C3E6-4BBE-A37D-11BA2AB9177C}.Release|iPhone.Build.0 = Release|Any CPU
 		{28F18757-C3E6-4BBE-A37D-11BA2AB9177C}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
 		{28F18757-C3E6-4BBE-A37D-11BA2AB9177C}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|Any CPU.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|Any CPU.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|iPhone.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|iPhone.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Ad-Hoc|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|Any CPU.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|Any CPU.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|iPhone.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|iPhone.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.AppStore|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|iPhone.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|iPhone.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|iPhoneSimulator.ActiveCfg = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Debug|iPhoneSimulator.Build.0 = Debug|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|Any CPU.Build.0 = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|iPhone.ActiveCfg = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|iPhone.Build.0 = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|iPhoneSimulator.ActiveCfg = Release|Any CPU
+		{780AC0FE-8DD2-419F-A1DC-AC7E3EB393F7}.Release|iPhoneSimulator.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

azure-pipelines.yml

@@ -56,13 +56,6 @@ jobs:
       xcodeVersion: '10' # Options: 8, 9, default, specifyPath
       args: '-derivedDataPath ./'
 
-  - task: CmdLine@2
-    displayName: 'Install CastXML'
-    inputs:
-      script: |
-        brew update
-        brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/8a004a91a7fcd3f6620d5b01b6541ff0a640ffba/Formula/castxml.rb
-
   - task: CmdLine@2
     displayName: 'Install Nuke'
     inputs:

build/NetFX.props

@@ -1,7 +1,7 @@
 <Project>
 
   <ItemGroup>
-    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0-preview.2" PrivateAssets="All" />
+    <PackageReference Include="Microsoft.NETFramework.ReferenceAssemblies" Version="1.0.0" PrivateAssets="All" />
   </ItemGroup>
 
 </Project>

src/Avalonia.Controls/ApiCompatBaseline.txt

@@ -12,7 +12,9 @@ MembersMustExist : Member 'public Avalonia.DirectProperty<Avalonia.Controls.Tree
 MembersMustExist : Member 'public Avalonia.Interactivity.RoutedEvent<Avalonia.Controls.SelectionChangedEventArgs> Avalonia.Interactivity.RoutedEvent<Avalonia.Controls.SelectionChangedEventArgs> Avalonia.Controls.TreeView.SelectionChangedEvent' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public Avalonia.Controls.ISelectionModel Avalonia.Controls.TreeView.Selection.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'public void Avalonia.Controls.TreeView.Selection.set(Avalonia.Controls.ISelectionModel)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.String[] Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.Args' is present in the implementation but not in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.String[] Avalonia.Controls.ApplicationLifetimes.IClassicDesktopStyleApplicationLifetime.Args.get()' is present in the implementation but not in the contract.
 MembersMustExist : Member 'public Avalonia.DirectProperty<Avalonia.Controls.Primitives.SelectingItemsControl, Avalonia.Controls.ISelectionModel> Avalonia.DirectProperty<Avalonia.Controls.Primitives.SelectingItemsControl, Avalonia.Controls.ISelectionModel> Avalonia.Controls.Primitives.SelectingItemsControl.SelectionProperty' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'protected Avalonia.Controls.ISelectionModel Avalonia.Controls.Primitives.SelectingItemsControl.Selection.get()' does not exist in the implementation but it does exist in the contract.
 MembersMustExist : Member 'protected void Avalonia.Controls.Primitives.SelectingItemsControl.Selection.set(Avalonia.Controls.ISelectionModel)' does not exist in the implementation but it does exist in the contract.
-Total Issues: 16
+Total Issues: 18

src/Avalonia.Controls/ApplicationLifetimes/ClassicDesktopStyleApplicationLifetime.cs

@@ -47,6 +47,11 @@ namespace Avalonia.Controls.ApplicationLifetimes
         /// <inheritdoc/>
         public event EventHandler<ControlledApplicationLifetimeExitEventArgs> Exit;
 
+        /// <summary>
+        /// Gets the arguments passed to the AppBuilder Start method.
+        /// </summary>
+        public string[] Args { get; set; }
+        
         /// <inheritdoc/>
         public ShutdownMode ShutdownMode { get; set; }
         
@@ -68,9 +73,6 @@ namespace Avalonia.Controls.ApplicationLifetimes
             else if (ShutdownMode == ShutdownMode.OnMainWindowClose && window == MainWindow)
                 Shutdown();
         }
-        
-        
-
 
         public void Shutdown(int exitCode = 0)
         {
@@ -123,7 +125,11 @@ namespace Avalonia
             this T builder, string[] args, ShutdownMode shutdownMode = ShutdownMode.OnLastWindowClose)
             where T : AppBuilderBase<T>, new()
         {
-            var lifetime = new ClassicDesktopStyleApplicationLifetime() {ShutdownMode = shutdownMode};
+            var lifetime = new ClassicDesktopStyleApplicationLifetime()
+            {
+                Args = args,
+                ShutdownMode = shutdownMode
+            };
             builder.SetupWithLifetime(lifetime);
             return lifetime.Start(args);
         }

src/Avalonia.Controls/ApplicationLifetimes/IClassicDesktopStyleApplicationLifetime.cs

@@ -8,6 +8,13 @@ namespace Avalonia.Controls.ApplicationLifetimes
     /// </summary>
     public interface IClassicDesktopStyleApplicationLifetime : IControlledApplicationLifetime
     {
+        /// <summary>
+        /// Gets the arguments passed to the
+        /// <see cref="ClassicDesktopStyleApplicationLifetimeExtensions.StartWithClassicDesktopLifetime{T}(T, string[], ShutdownMode)"/>
+        /// method.
+        /// </summary>
+        string[] Args { get; }
+        
         /// <summary>
         /// Gets or sets the <see cref="ShutdownMode"/>. This property indicates whether the application is shutdown explicitly or implicitly. 
         /// If <see cref="ShutdownMode"/> is set to OnExplicitShutdown the application is only closes if Shutdown is called.

src/Avalonia.Controls/ColumnDefinitions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Specialized;
 using System.Linq;
+using System.Text;
 using Avalonia.Collections;
 
 namespace Avalonia.Controls
@@ -13,7 +14,7 @@ namespace Avalonia.Controls
         /// <summary>
         /// Initializes a new instance of the <see cref="ColumnDefinitions"/> class.
         /// </summary>
-        public ColumnDefinitions() : base ()
+        public ColumnDefinitions()
         {
         }
 
@@ -27,6 +28,11 @@ namespace Avalonia.Controls
             AddRange(GridLength.ParseLengths(s).Select(x => new ColumnDefinition(x)));
         }
 
+        public override string ToString()
+        {
+            return string.Join(",", this.Select(x => x.Width));
+        }
+
         /// <summary>
         /// Parses a string representation of column definitions collection.
         /// </summary>
@@ -34,4 +40,4 @@ namespace Avalonia.Controls
         /// <returns>The <see cref="ColumnDefinitions"/>.</returns>
         public static ColumnDefinitions Parse(string s) => new ColumnDefinitions(s);
     }
-}
+}

src/Avalonia.Controls/Presenters/TextPresenter.cs

@@ -282,7 +282,7 @@ namespace Avalonia.Controls.Presenters
             return new FormattedText
             {
                 Constraint = constraint,
-                Typeface = FontManager.Current?.GetOrAddTypeface(FontFamily, FontStyle, FontWeight),
+                Typeface = new Typeface(FontFamily, FontStyle, FontWeight),
                 FontSize = FontSize,
                 Text = text ?? string.Empty,
                 TextAlignment = TextAlignment,
@@ -499,7 +499,7 @@ namespace Avalonia.Controls.Presenters
                 return new FormattedText
                 {
                     Text = "X",
-                    Typeface = FontManager.Current?.GetOrAddTypeface(FontFamily, FontStyle, FontWeight),
+                    Typeface = new Typeface(FontFamily, FontStyle, FontWeight),
                     FontSize = FontSize,
                     TextAlignment = TextAlignment,
                     Constraint = availableSize,

src/Avalonia.Controls/Primitives/ScrollBar.cs

@@ -141,7 +141,7 @@ namespace Avalonia.Controls.Primitives
                 _ => throw new InvalidOperationException("Invalid value for ScrollBar.Visibility.")
             };
 
-            SetValue(IsVisibleProperty, isVisible, BindingPriority.Style);
+            SetValue(IsVisibleProperty, isVisible);
         }
 
         protected override void OnKeyDown(KeyEventArgs e)

src/Avalonia.Controls/Repeater/ItemsRepeater.cs

@@ -7,10 +7,10 @@ using System;
 using System.Collections;
 using System.Collections.Specialized;
 using Avalonia.Controls.Templates;
-using Avalonia.Data;
 using Avalonia.Input;
 using Avalonia.Layout;
 using Avalonia.Logging;
+using Avalonia.Utilities;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Controls
@@ -681,8 +681,15 @@ namespace Avalonia.Controls
             if (oldValue != null)
             {
                 oldValue.UninitializeForContext(LayoutContext);
-                oldValue.MeasureInvalidated -= InvalidateMeasureForLayout;
+
-                oldValue.ArrangeInvalidated -= InvalidateArrangeForLayout;
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(AttachedLayout.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Unsubscribe<EventArgs, ItemsRepeater>(
+                    oldValue,
+                    nameof(AttachedLayout.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
 
                 // Walk through all the elements and make sure they are cleared
                 foreach (var element in Children)
@@ -699,8 +706,15 @@ namespace Avalonia.Controls
             if (newValue != null)
             {
                 newValue.InitializeForContext(LayoutContext);
-                newValue.MeasureInvalidated += InvalidateMeasureForLayout;
+
-                newValue.ArrangeInvalidated += InvalidateArrangeForLayout;
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(AttachedLayout.MeasureInvalidated),
+                    InvalidateMeasureForLayout);
+                WeakEventHandlerManager.Subscribe<AttachedLayout, EventArgs, ItemsRepeater>(
+                    newValue,
+                    nameof(AttachedLayout.ArrangeInvalidated),
+                    InvalidateArrangeForLayout);
             }
 
             bool isVirtualizingLayout = newValue != null && newValue is VirtualizingLayout;

src/Avalonia.Controls/TextBlock.cs

@@ -452,7 +452,7 @@ namespace Avalonia.Controls
 
             return new TextLayout(
                 text ?? string.Empty,
-                FontManager.Current?.GetOrAddTypeface(FontFamily, FontStyle, FontWeight),
+                new Typeface(FontFamily, FontStyle, FontWeight),
                 FontSize,
                 Foreground,
                 TextAlignment,

src/Avalonia.DesignerSupport/Remote/HtmlTransport/HtmlTransport.cs

@@ -38,11 +38,13 @@ namespace Avalonia.DesignerSupport.Remote.HtmlTransport
         public HtmlWebSocketTransport(IAvaloniaRemoteTransportConnection signalTransport, Uri listenUri)
         {
             if (listenUri.Scheme != "http")
-                throw new ArgumentException("listenUri");
+                throw new ArgumentException("URI scheme is not HTTP.", nameof(listenUri));
 
             var resourcePrefix = "Avalonia.DesignerSupport.Remote.HtmlTransport.webapp.build.";
             _resources = typeof(HtmlWebSocketTransport).Assembly.GetManifestResourceNames()
-                .Where(r => r.StartsWith(resourcePrefix) && r.EndsWith(".gz")).ToDictionary(
+                .Where(r => r.StartsWith(resourcePrefix, StringComparison.OrdinalIgnoreCase)
+                         && r.EndsWith(".gz", StringComparison.OrdinalIgnoreCase))
+                .ToDictionary(
                     r => r.Substring(resourcePrefix.Length).Substring(0,r.Length-resourcePrefix.Length-3),
                     r =>
                     {

src/Avalonia.Diagnostics/Diagnostics/ViewModels/PropertyViewModel.cs

@@ -8,8 +8,8 @@ namespace Avalonia.Diagnostics.ViewModels
     internal abstract class PropertyViewModel : ViewModelBase
     {
         private const BindingFlags PublicStatic = BindingFlags.Public | BindingFlags.Static;
-        private static readonly Type[] StringParameter = new[] { typeof(string) };
+        private static readonly Type[] StringParameter = { typeof(string) };
-        private static readonly Type[] StringIFormatProviderParameters = new[] { typeof(string), typeof(IFormatProvider) };
+        private static readonly Type[] StringIFormatProviderParameters = { typeof(string), typeof(IFormatProvider) };
 
         public abstract object Key { get; }
         public abstract string Name { get; }
@@ -26,35 +26,46 @@ namespace Avalonia.Diagnostics.ViewModels
             }
 
             var converter = TypeDescriptor.GetConverter(value);
-            return converter?.ConvertToString(value) ?? value.ToString();
+
+            //CollectionConverter does not deliver any important information. It just displays "(Collection)".
+            if (!converter.CanConvertTo(typeof(string)) || 
+                converter.GetType() == typeof(CollectionConverter))
+            {
+                return value.ToString();
+            }
+
+            return converter.ConvertToString(value);
         }
 
-        protected static object ConvertFromString(string s, Type targetType)
+        private static object InvokeParse(string s, Type targetType)
         {
-            var converter = TypeDescriptor.GetConverter(targetType);
+            var method = targetType.GetMethod("Parse", PublicStatic, null, StringIFormatProviderParameters, null);
-            
+
-            if (converter != null && converter.CanConvertFrom(typeof(string)))
+            if (method != null)
             {
-                return converter.ConvertFrom(null, CultureInfo.InvariantCulture, s);
+                return method.Invoke(null, new object[] { s, CultureInfo.InvariantCulture });
             }
-            else
+
+            method = targetType.GetMethod("Parse", PublicStatic, null, StringParameter, null);
+
+            if (method != null)
             {
-                var method = targetType.GetMethod("Parse", PublicStatic, null, StringIFormatProviderParameters, null);
+                return method.Invoke(null, new object[] { s });
+            }
 
-                if (method != null)
+            throw new InvalidCastException("Unable to convert value.");
-                {
+        }
-                    return method.Invoke(null, new object[] { s, CultureInfo.InvariantCulture });
-                }
 
-                method = targetType.GetMethod("Parse", PublicStatic, null, StringParameter, null);
+        protected static object ConvertFromString(string s, Type targetType)
+        {
+            var converter = TypeDescriptor.GetConverter(targetType);
 
-                if (method != null)
+            if (converter.CanConvertFrom(typeof(string)))
-                {
+            {
-                    return method.Invoke(null, new object[] { s });
+                return converter.ConvertFrom(null, CultureInfo.InvariantCulture, s);
-                }
             }
 
-            throw new InvalidCastException("Unable to convert value.");
+            return InvokeParse(s, targetType);
         }
     }
 }

src/Avalonia.Headless/HeadlessPlatformStubs.cs

@@ -155,9 +155,9 @@ namespace Avalonia.Headless
             return new List<string> { "Arial" };
         }
 
-        public bool TryMatchCharacter(int codepoint, FontStyle fontStyle, FontWeight fontWeight, FontFamily fontFamily, CultureInfo culture, out FontKey fontKey)
+        public bool TryMatchCharacter(int codepoint, FontStyle fontStyle, FontWeight fontWeight, FontFamily fontFamily, CultureInfo culture, out Typeface typeface)
         {
-            fontKey = new FontKey("Arial", fontStyle, fontWeight);
+            typeface = new Typeface("Arial", fontStyle, fontWeight);
             return true;
         }
     }

src/Avalonia.Input/AccessKeyHandler.cs

@@ -28,7 +28,7 @@ namespace Avalonia.Input
         /// <summary>
         /// The window to which the handler belongs.
         /// </summary>
-        private IInputRoot _owner;
+        private IInputRoot? _owner;
 
         /// <summary>
         /// Whether access keys are currently being shown;
@@ -48,17 +48,17 @@ namespace Avalonia.Input
         /// <summary>
         /// Element to restore following AltKey taking focus.
         /// </summary>
-        private IInputElement _restoreFocusElement;
+        private IInputElement? _restoreFocusElement;
 
         /// <summary>
         /// The window's main menu.
         /// </summary>
-        private IMainMenu _mainMenu;
+        private IMainMenu? _mainMenu;
 
         /// <summary>
         /// Gets or sets the window's main menu.
         /// </summary>
-        public IMainMenu MainMenu
+        public IMainMenu? MainMenu
         {
             get => _mainMenu;
             set
@@ -86,14 +86,12 @@ namespace Avalonia.Input
         /// </remarks>
         public void SetOwner(IInputRoot owner)
         {
-            Contract.Requires<ArgumentNullException>(owner != null);
-
             if (_owner != null)
             {
                 throw new InvalidOperationException("AccessKeyHandler owner has already been set.");
             }
 
-            _owner = owner;
+            _owner = owner ?? throw new ArgumentNullException(nameof(owner));
 
             _owner.AddHandler(InputElement.KeyDownEvent, OnPreviewKeyDown, RoutingStrategies.Tunnel);
             _owner.AddHandler(InputElement.KeyDownEvent, OnKeyDown, RoutingStrategies.Bubble);
@@ -149,7 +147,7 @@ namespace Avalonia.Input
 
                     // When Alt is pressed without a main menu, or with a closed main menu, show
                     // access key markers in the window (i.e. "_File").
-                    _owner.ShowAccessKeys = _showingAccessKeys = true;
+                    _owner!.ShowAccessKeys = _showingAccessKeys = true;
                 }
                 else
                 {
@@ -241,7 +239,7 @@ namespace Avalonia.Input
         {
             if (_showingAccessKeys)
             {
-                _owner.ShowAccessKeys = false;
+                _owner!.ShowAccessKeys = false;
             }
         }
 
@@ -250,13 +248,13 @@ namespace Avalonia.Input
         /// </summary>
         private void CloseMenu()
         {
-            MainMenu.Close();
+            MainMenu!.Close();
-            _owner.ShowAccessKeys = _showingAccessKeys = false;
+            _owner!.ShowAccessKeys = _showingAccessKeys = false;
         }
 
         private void MainMenuClosed(object sender, EventArgs e)
         {
-            _owner.ShowAccessKeys = false;
+            _owner!.ShowAccessKeys = false;
         }
     }
 }

src/Avalonia.Input/Avalonia.Input.csproj

@@ -1,6 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFramework>netstandard2.0</TargetFramework>
+    <Nullable>Enable</Nullable>
+    <WarningsAsErrors>CS8600;CS8602;CS8603</WarningsAsErrors>
   </PropertyGroup>
   <ItemGroup>
     <ProjectReference Include="..\Avalonia.Animation\Avalonia.Animation.csproj" />

src/Avalonia.Input/DataObject.cs

@@ -11,7 +11,7 @@ namespace Avalonia.Input
             return _items.ContainsKey(dataFormat);
         }
 
-        public object Get(string dataFormat)
+        public object? Get(string dataFormat)
         {
             if (_items.ContainsKey(dataFormat))
                 return _items[dataFormat];
@@ -23,12 +23,12 @@ namespace Avalonia.Input
             return _items.Keys;
         }
 
-        public IEnumerable<string> GetFileNames()
+        public IEnumerable<string>? GetFileNames()
         {
             return Get(DataFormats.FileNames) as IEnumerable<string>;
         }
 
-        public string GetText()
+        public string? GetText()
         {
             return Get(DataFormats.Text) as string;
         }

src/Avalonia.Input/DragDropDevice.cs

@@ -9,9 +9,9 @@ namespace Avalonia.Input
     {
         public static readonly DragDropDevice Instance = new DragDropDevice();
         
-        private Interactive _lastTarget = null;
+        private Interactive? _lastTarget = null;
         
-        private Interactive GetTarget(IInputRoot root, Point local)
+        private Interactive? GetTarget(IInputRoot root, Point local)
         {
             var target = root.InputHitTest(local)?.GetSelfAndVisualAncestors()?.OfType<Interactive>()?.FirstOrDefault();
             if (target != null && DragDrop.GetAllowDrop(target))
@@ -19,7 +19,7 @@ namespace Avalonia.Input
             return null;
         }
         
-        private DragDropEffects RaiseDragEvent(Interactive target, IInputRoot inputRoot, Point point, RoutedEvent<DragEventArgs> routedEvent, DragDropEffects operation, IDataObject data, KeyModifiers modifiers)
+        private DragDropEffects RaiseDragEvent(Interactive? target, IInputRoot inputRoot, Point point, RoutedEvent<DragEventArgs> routedEvent, DragDropEffects operation, IDataObject data, KeyModifiers modifiers)
         {
             if (target == null)
                 return DragDropEffects.None;

src/Avalonia.Input/FocusManager.cs

@@ -15,8 +15,8 @@ namespace Avalonia.Input
         /// <summary>
         /// The focus scopes in which the focus is currently defined.
         /// </summary>
-        private readonly ConditionalWeakTable<IFocusScope, IInputElement> _focusScopes =
+        private readonly ConditionalWeakTable<IFocusScope, IInputElement?> _focusScopes =
-            new ConditionalWeakTable<IFocusScope, IInputElement>();
+            new ConditionalWeakTable<IFocusScope, IInputElement?>();
 
         /// <summary>
         /// Initializes a new instance of the <see cref="FocusManager"/> class.
@@ -37,12 +37,12 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets the currently focused <see cref="IInputElement"/>.
         /// </summary>
-        public IInputElement Current => KeyboardDevice.Instance?.FocusedElement;
+        public IInputElement? Current => KeyboardDevice.Instance?.FocusedElement;
 
         /// <summary>
         /// Gets the current focus scope.
         /// </summary>
-        public IFocusScope Scope
+        public IFocusScope? Scope
         {
             get;
             private set;
@@ -55,7 +55,7 @@ namespace Avalonia.Input
         /// <param name="method">The method by which focus was changed.</param>
         /// <param name="keyModifiers">Any key modifiers active at the time of focus.</param>
         public void Focus(
-            IInputElement control, 
+            IInputElement? control, 
             NavigationMethod method = NavigationMethod.Unspecified,
             KeyModifiers keyModifiers = KeyModifiers.None)
         {
@@ -75,17 +75,18 @@ namespace Avalonia.Input
                 // If control is null, set focus to the topmost focus scope.
                 foreach (var scope in GetFocusScopeAncestors(Current).Reverse().ToList())
                 {
-                    IInputElement element;
+                    if (_focusScopes.TryGetValue(scope, out var element) && element != null)
-
-                    if (_focusScopes.TryGetValue(scope, out element) && element != null)
                     {
                         Focus(element, method);
                         return;
                     }
                 }
 
-                // Couldn't find a focus scope, clear focus.
+                if (Scope is object)
-                SetFocusedElement(Scope, null);
+                {
+                    // Couldn't find a focus scope, clear focus.
+                    SetFocusedElement(Scope, null);
+                }
             }
         }
 
@@ -102,13 +103,13 @@ namespace Avalonia.Input
         /// </remarks>
         public void SetFocusedElement(
             IFocusScope scope,
-            IInputElement element,
+            IInputElement? element,
             NavigationMethod method = NavigationMethod.Unspecified,
             KeyModifiers keyModifiers = KeyModifiers.None)
         {
-            Contract.Requires<ArgumentNullException>(scope != null);
+            scope = scope ?? throw new ArgumentNullException(nameof(scope));
 
-            if (_focusScopes.TryGetValue(scope, out IInputElement existingElement))
+            if (_focusScopes.TryGetValue(scope, out var existingElement))
             {
                 if (element != existingElement)
                 {
@@ -133,11 +134,9 @@ namespace Avalonia.Input
         /// <param name="scope">The new focus scope.</param>
         public void SetFocusScope(IFocusScope scope)
         {
-            Contract.Requires<ArgumentNullException>(scope != null);
+            scope = scope ?? throw new ArgumentNullException(nameof(scope));
 
-            IInputElement e;
+            if (!_focusScopes.TryGetValue(scope, out var e))
-
-            if (!_focusScopes.TryGetValue(scope, out e))
             {
                 // TODO: Make this do something useful, i.e. select the first focusable
                 // control, select a control that the user has specified to have default
@@ -164,17 +163,19 @@ namespace Avalonia.Input
         /// <returns>The focus scopes.</returns>
         private static IEnumerable<IFocusScope> GetFocusScopeAncestors(IInputElement control)
         {
-            while (control != null)
+            IInputElement? c = control;
+
+            while (c != null)
             {
-                var scope = control as IFocusScope;
+                var scope = c as IFocusScope;
 
-                if (scope != null && control.VisualRoot?.IsVisible == true)
+                if (scope != null && c.VisualRoot?.IsVisible == true)
                 {
                     yield return scope;
                 }
 
-                control = control.GetVisualParent<IInputElement>() ??
+                c = c.GetVisualParent<IInputElement>() ??
-                    ((control as IHostedVisualTreeRoot)?.Host as IInputElement);
+                    ((c as IHostedVisualTreeRoot)?.Host as IInputElement);
             }
         }
 
@@ -190,7 +191,7 @@ namespace Avalonia.Input
 
             if (sender == e.Source && ev.GetCurrentPoint(visual).Properties.IsLeftButtonPressed)
             {
-                IVisual element = ev.Pointer?.Captured ?? e.Source as IInputElement;
+                IVisual? element = ev.Pointer?.Captured ?? e.Source as IInputElement;
 
                 while (element != null)
                 {

src/Avalonia.Input/GestureRecognizers/GestureRecognizerCollection.cs

@@ -1,8 +1,6 @@
-using System;
 using System.Collections;
 using System.Collections.Generic;
 using Avalonia.Controls;
-using Avalonia.Data;
 using Avalonia.LogicalTree;
 using Avalonia.Styling;
 
@@ -11,8 +9,8 @@ namespace Avalonia.Input.GestureRecognizers
     public class GestureRecognizerCollection : IReadOnlyCollection<IGestureRecognizer>, IGestureRecognizerActionsDispatcher
     {
         private readonly IInputElement _inputElement;
-        private List<IGestureRecognizer> _recognizers;
+        private List<IGestureRecognizer>? _recognizers;
-        private Dictionary<IPointer, IGestureRecognizer> _pointerGrabs;
+        private Dictionary<IPointer, IGestureRecognizer>? _pointerGrabs;
         
         
         public GestureRecognizerCollection(IInputElement inputElement)
@@ -72,7 +70,7 @@ namespace Avalonia.Input.GestureRecognizers
         {
             if (_recognizers == null)
                 return false;
-            if (_pointerGrabs.TryGetValue(e.Pointer, out var capture))
+            if (_pointerGrabs!.TryGetValue(e.Pointer, out var capture))
             {
                 capture.PointerReleased(e);
             }
@@ -90,7 +88,7 @@ namespace Avalonia.Input.GestureRecognizers
         {
             if (_recognizers == null)
                 return false;
-            if (_pointerGrabs.TryGetValue(e.Pointer, out var capture))
+            if (_pointerGrabs!.TryGetValue(e.Pointer, out var capture))
             {
                 capture.PointerMoved(e);
             }
@@ -108,7 +106,7 @@ namespace Avalonia.Input.GestureRecognizers
         {
             if (_recognizers == null)
                 return;
-            _pointerGrabs.Remove(e.Pointer);
+            _pointerGrabs!.Remove(e.Pointer);
             foreach (var r in _recognizers)
             {
                 r.PointerCaptureLost(e.Pointer);
@@ -118,8 +116,8 @@ namespace Avalonia.Input.GestureRecognizers
         void IGestureRecognizerActionsDispatcher.Capture(IPointer pointer, IGestureRecognizer recognizer)
         {
             pointer.Capture(_inputElement);
-            _pointerGrabs[pointer] = recognizer;
+            _pointerGrabs![pointer] = recognizer;
-            foreach (var r in _recognizers)
+            foreach (var r in _recognizers!)
             {
                 if (r != recognizer)
                     r.PointerCaptureLost(pointer);

src/Avalonia.Input/GestureRecognizers/ScrollGestureRecognizer.cs

@@ -1,6 +1,5 @@
 using System;
 using System.Diagnostics;
-using Avalonia.Interactivity;
 using Avalonia.Threading;
 
 namespace Avalonia.Input.GestureRecognizers
@@ -11,9 +10,9 @@ namespace Avalonia.Input.GestureRecognizers
     {
         private bool _scrolling;
         private Point _trackedRootPoint;
-        private IPointer _tracking;
+        private IPointer? _tracking;
-        private IInputElement _target;
+        private IInputElement? _target;
-        private IGestureRecognizerActionsDispatcher _actions;
+        private IGestureRecognizerActionsDispatcher? _actions;
         private bool _canHorizontallyScroll;
         private bool _canVerticallyScroll;
         private int _gestureId;
@@ -95,7 +94,7 @@ namespace Avalonia.Input.GestureRecognizers
                         _scrolling = true;
                     if (_scrolling)
                     {
-                        _actions.Capture(e.Pointer, this);
+                        _actions!.Capture(e.Pointer, this);
                     }
                 }
 
@@ -110,7 +109,7 @@ namespace Avalonia.Input.GestureRecognizers
                     _trackedRootPoint = rootPoint;
                     if (elapsed.TotalSeconds > 0)
                         _inertia = vector / elapsed.TotalSeconds;
-                    _target.RaiseEvent(new ScrollGestureEventArgs(_gestureId, vector));
+                    _target!.RaiseEvent(new ScrollGestureEventArgs(_gestureId, vector));
                     e.Handled = true;
                 }
             }
@@ -128,7 +127,7 @@ namespace Avalonia.Input.GestureRecognizers
             {
                 _inertia = default;
                 _scrolling = false;
-                _target.RaiseEvent(new ScrollGestureEndedEventArgs(_gestureId));
+                _target!.RaiseEvent(new ScrollGestureEndedEventArgs(_gestureId));
                 _gestureId = 0;
                 _lastMoveTimestamp = null;
             }
@@ -165,7 +164,7 @@ namespace Avalonia.Input.GestureRecognizers
 
                         var speed = _inertia * Math.Pow(0.15, st.Elapsed.TotalSeconds);
                         var distance = speed * elapsedSinceLastTick.TotalSeconds;
-                        _target.RaiseEvent(new ScrollGestureEventArgs(_gestureId, distance));
+                        _target!.RaiseEvent(new ScrollGestureEventArgs(_gestureId, distance));
 
 
 

src/Avalonia.Input/Gestures.cs

@@ -29,7 +29,9 @@ namespace Avalonia.Input
             RoutedEvent.Register<ScrollGestureEventArgs>(
                 "ScrollGestureEnded", RoutingStrategies.Bubble, typeof(Gestures));
 
+#pragma warning disable CS8625 // Cannot convert null literal to non-nullable reference type.
         private static WeakReference<IInteractive> s_lastPress = new WeakReference<IInteractive>(null);
+#pragma warning restore CS8625 // Cannot convert null literal to non-nullable reference type.
 
         static Gestures()
         {
@@ -69,6 +71,11 @@ namespace Avalonia.Input
 
         private static void PointerPressed(RoutedEventArgs ev)
         {
+            if (ev.Source is null)
+            {
+                return;
+            }
+
             if (ev.Route == RoutingStrategies.Bubble)
             {
                 var e = (PointerPressedEventArgs)ev;
@@ -76,7 +83,7 @@ namespace Avalonia.Input
 
                 if (e.ClickCount <= 1)
                 {
-                    s_lastPress = new WeakReference<IInteractive>(e.Source);
+                    s_lastPress = new WeakReference<IInteractive>(ev.Source);
                 }
                 else if (s_lastPress != null && e.ClickCount == 2 && e.GetCurrentPoint(visual).Properties.IsLeftButtonPressed)
                 {

src/Avalonia.Input/IAccessKeyHandler.cs

@@ -8,7 +8,7 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets or sets the window's main menu.
         /// </summary>
-        IMainMenu MainMenu { get; set; }
+        IMainMenu? MainMenu { get; set; }
 
         /// <summary>
         /// Sets the owner of the access key handler.

src/Avalonia.Input/IDataObject.cs

@@ -23,17 +23,17 @@ namespace Avalonia.Input
         /// Returns the dragged text if the DataObject contains any text.
         /// <seealso cref="DataFormats.Text"/>
         /// </summary>
-        string GetText();
+        string? GetText();
 
         /// <summary>
         /// Returns a list of filenames if the DataObject contains filenames.
         /// <seealso cref="DataFormats.FileNames"/>
         /// </summary>
-        IEnumerable<string> GetFileNames();
+        IEnumerable<string>? GetFileNames();
         
         /// <summary>
         /// Tries to get the data of the given DataFormat.
         /// </summary>
-        object Get(string dataFormat);
+        object? Get(string dataFormat);
     }
 }

src/Avalonia.Input/IFocusManager.cs

@@ -8,12 +8,12 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets the currently focused <see cref="IInputElement"/>.
         /// </summary>
-        IInputElement Current { get; }
+        IInputElement? Current { get; }
 
         /// <summary>
         /// Gets the current focus scope.
         /// </summary>
-        IFocusScope Scope { get; }
+        IFocusScope? Scope { get; }
 
         /// <summary>
         /// Focuses a control.
@@ -22,7 +22,7 @@ namespace Avalonia.Input
         /// <param name="method">The method by which focus was changed.</param>
         /// <param name="keyModifiers">Any key modifiers active at the time of focus.</param>
         void Focus(
-            IInputElement control,
+            IInputElement? control,
             NavigationMethod method = NavigationMethod.Unspecified,
             KeyModifiers keyModifiers = KeyModifiers.None);
 

src/Avalonia.Input/IInputElement.cs

@@ -78,7 +78,7 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets or sets the associated mouse cursor.
         /// </summary>
-        Cursor Cursor { get; }
+        Cursor? Cursor { get; }
 
         /// <summary>
         /// Gets a value indicating whether this control and all its parents are enabled.

src/Avalonia.Input/IInputRoot.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets or sets the input element that the pointer is currently over.
         /// </summary>
-        IInputElement PointerOverElement { get; set; }
+        IInputElement? PointerOverElement { get; set; }
 
         /// <summary>
         /// Gets or sets a value indicating whether access keys are shown in the window.
@@ -31,6 +31,6 @@ namespace Avalonia.Input
         /// Gets associated mouse device
         /// </summary>
         [CanBeNull]
-        IMouseDevice MouseDevice { get; }
+        IMouseDevice? MouseDevice { get; }
     }
 }

src/Avalonia.Input/IKeyboardDevice.cs

@@ -58,10 +58,10 @@ namespace Avalonia.Input
 
     public interface IKeyboardDevice : IInputDevice, INotifyPropertyChanged
     {
-        IInputElement FocusedElement { get; }
+        IInputElement? FocusedElement { get; }
 
         void SetFocusedElement(
-            IInputElement element, 
+            IInputElement? element, 
             NavigationMethod method,
             KeyModifiers modifiers);
     }

src/Avalonia.Input/IPointer.cs

@@ -3,8 +3,8 @@ namespace Avalonia.Input
     public interface IPointer
     {
         int Id { get; }
-        void Capture(IInputElement control);
+        void Capture(IInputElement? control);
-        IInputElement Captured { get; }
+        IInputElement? Captured { get; }
         PointerType Type { get; }
         bool IsPrimary { get; }
         

src/Avalonia.Input/IPointerDevice.cs

@@ -6,10 +6,10 @@ namespace Avalonia.Input
     public interface IPointerDevice : IInputDevice
     {
         [Obsolete("Use IPointer")]
-        IInputElement Captured { get; }
+        IInputElement? Captured { get; }
         
         [Obsolete("Use IPointer")]
-        void Capture(IInputElement control);
+        void Capture(IInputElement? control);
 
         [Obsolete("Use PointerEventArgs.GetPosition")]
         Point GetPosition(IVisual relativeTo);

src/Avalonia.Input/InputElement.cs

@@ -37,8 +37,8 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets or sets associated mouse cursor.
         /// </summary>
-        public static readonly StyledProperty<Cursor> CursorProperty =
+        public static readonly StyledProperty<Cursor?> CursorProperty =
-            AvaloniaProperty.Register<InputElement, Cursor>(nameof(Cursor), null, true);
+            AvaloniaProperty.Register<InputElement, Cursor?>(nameof(Cursor), null, true);
 
         /// <summary>
         /// Defines the <see cref="IsFocused"/> property.
@@ -160,7 +160,7 @@ namespace Avalonia.Input
         private bool _isFocused;
         private bool _isFocusVisible;
         private bool _isPointerOver;
-        private GestureRecognizerCollection _gestureRecognizers;
+        private GestureRecognizerCollection? _gestureRecognizers;
 
         /// <summary>
         /// Initializes static members of the <see cref="InputElement"/> class.
@@ -336,7 +336,7 @@ namespace Avalonia.Input
         /// <summary>
         /// Gets or sets associated mouse cursor.
         /// </summary>
-        public Cursor Cursor
+        public Cursor? Cursor
         {
             get { return GetValue(CursorProperty); }
             set { SetValue(CursorProperty, value); }

src/Avalonia.Input/KeyEventArgs.cs

@@ -5,7 +5,7 @@ namespace Avalonia.Input
 {
     public class KeyEventArgs : RoutedEventArgs
     {
-        public IKeyboardDevice Device { get; set; }
+        public IKeyboardDevice? Device { get; set; }
 
         public Key Key { get; set; }
 

src/Avalonia.Input/KeyboardDevice.cs

@@ -8,9 +8,9 @@ namespace Avalonia.Input
 {
     public class KeyboardDevice : IKeyboardDevice, INotifyPropertyChanged
     {
-        private IInputElement _focusedElement;
+        private IInputElement? _focusedElement;
 
-        public event PropertyChangedEventHandler PropertyChanged;
+        public event PropertyChangedEventHandler? PropertyChanged;
 
         public static IKeyboardDevice Instance => AvaloniaLocator.Current.GetService<IKeyboardDevice>();
 
@@ -18,7 +18,7 @@ namespace Avalonia.Input
 
         public IFocusManager FocusManager => AvaloniaLocator.Current.GetService<IFocusManager>();
 
-        public IInputElement FocusedElement
+        public IInputElement? FocusedElement
         {
             get
             {
@@ -33,7 +33,7 @@ namespace Avalonia.Input
         }
 
         public void SetFocusedElement(
-            IInputElement element, 
+            IInputElement? element, 
             NavigationMethod method,
             KeyModifiers keyModifiers)
         {

src/Avalonia.Input/KeyboardNavigationHandler.cs

@@ -13,7 +13,7 @@ namespace Avalonia.Input
         /// <summary>
         /// The window to which the handler belongs.
         /// </summary>
-        private IInputRoot _owner;
+        private IInputRoot? _owner;
 
         /// <summary>
         /// Sets the owner of the keyboard navigation handler.
@@ -24,15 +24,12 @@ namespace Avalonia.Input
         /// </remarks>
         public void SetOwner(IInputRoot owner)
         {
-            Contract.Requires<ArgumentNullException>(owner != null);
-
             if (_owner != null)
             {
                 throw new InvalidOperationException("AccessKeyHandler owner has already been set.");
             }
 
-            _owner = owner;
+            _owner = owner ?? throw new ArgumentNullException(nameof(owner));
-
             _owner.AddHandler(InputElement.KeyDownEvent, OnKeyDown);
         }
 
@@ -45,11 +42,11 @@ namespace Avalonia.Input
         /// The next element in the specified direction, or null if <paramref name="element"/>
         /// was the last in the requested direction.
         /// </returns>
-        public static IInputElement GetNext(
+        public static IInputElement? GetNext(
             IInputElement element,
             NavigationDirection direction)
         {
-            Contract.Requires<ArgumentNullException>(element != null);
+            element = element ?? throw new ArgumentNullException(nameof(element));
 
             var customHandler = element.GetSelfAndVisualAncestors()
                 .OfType<ICustomKeyboardNavigation>()
@@ -97,7 +94,7 @@ namespace Avalonia.Input
             NavigationDirection direction,
             KeyModifiers keyModifiers = KeyModifiers.None)
         {
-            Contract.Requires<ArgumentNullException>(element != null);
+            element = element ?? throw new ArgumentNullException(nameof(element));
 
             var next = GetNext(element, direction);
 

src/Avalonia.Input/MouseDevice.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Input
         private readonly Pointer _pointer;
         private bool _disposed;
 
-        public MouseDevice(Pointer pointer = null)
+        public MouseDevice(Pointer? pointer = null)
         {
             _pointer = pointer ?? new Pointer(Pointer.GetNextFreeId(), PointerType.Mouse, true);
         }
@@ -34,7 +34,7 @@ namespace Avalonia.Input
         /// <see cref="Capture"/> method.
         /// </remarks>
         [Obsolete("Use IPointer instead")]
-        public IInputElement Captured => _pointer.Captured;
+        public IInputElement? Captured => _pointer.Captured;
 
         /// <summary>
         /// Gets the mouse position, in screen coordinates.
@@ -54,7 +54,7 @@ namespace Avalonia.Input
         /// within the control's bounds or not. The current mouse capture control is exposed
         /// by the <see cref="Captured"/> property.
         /// </remarks>
-        public void Capture(IInputElement control)
+        public void Capture(IInputElement? control)
         {
             _pointer.Capture(control);
         }
@@ -66,7 +66,7 @@ namespace Avalonia.Input
         /// <returns>The mouse position in the control's coordinates.</returns>
         public Point GetPosition(IVisual relativeTo)
         {
-            Contract.Requires<ArgumentNullException>(relativeTo != null);
+            relativeTo = relativeTo ?? throw new ArgumentNullException(nameof(relativeTo));
 
             if (relativeTo.VisualRoot == null)
             {
@@ -75,7 +75,7 @@ namespace Avalonia.Input
 
             var rootPoint = relativeTo.VisualRoot.PointToClient(Position);
             var transform = relativeTo.VisualRoot.TransformToVisual(relativeTo);
-            return rootPoint * transform.Value;
+            return rootPoint * transform!.Value;
         }
 
         public void ProcessRawEvent(RawInputEventArgs e)
@@ -126,7 +126,7 @@ namespace Avalonia.Input
         
         private void ProcessRawEvent(RawPointerEventArgs e)
         {
-            Contract.Requires<ArgumentNullException>(e != null);
+            e = e ?? throw new ArgumentNullException(nameof(e));
 
             var mouse = (MouseDevice)e.Device;
             if(mouse._disposed)
@@ -173,8 +173,8 @@ namespace Avalonia.Input
         private void LeaveWindow(IMouseDevice device, ulong timestamp, IInputRoot root, PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             ClearPointerOver(this, timestamp, root, properties, inputModifiers);
         }
@@ -214,8 +214,8 @@ namespace Avalonia.Input
             PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             var hit = HitTest(root, p);
 
@@ -250,10 +250,10 @@ namespace Avalonia.Input
         private bool MouseMove(IMouseDevice device, ulong timestamp, IInputRoot root, Point p, PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
-            IInputElement source;
+            IInputElement? source;
 
             if (_pointer.Captured == null)
             {
@@ -265,18 +265,23 @@ namespace Avalonia.Input
                 source = _pointer.Captured;
             }
 
-            var e = new PointerEventArgs(InputElement.PointerMovedEvent, source, _pointer, root,
+            if (source is object)
-                p, timestamp, properties, inputModifiers);
+            {
+                var e = new PointerEventArgs(InputElement.PointerMovedEvent, source, _pointer, root,
+                    p, timestamp, properties, inputModifiers);
 
-            source?.RaiseEvent(e);
+                source.RaiseEvent(e);
-            return e.Handled;
+                return e.Handled;
+            }
+
+            return false;
         }
 
         private bool MouseUp(IMouseDevice device, ulong timestamp, IInputRoot root, Point p, PointerPointProperties props,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             var hit = HitTest(root, p);
 
@@ -298,8 +303,8 @@ namespace Avalonia.Input
             PointerPointProperties props,
             Vector delta, KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             var hit = HitTest(root, p);
 
@@ -317,21 +322,21 @@ namespace Avalonia.Input
 
         private IInteractive GetSource(IVisual hit)
         {
-            Contract.Requires<ArgumentNullException>(hit != null);
+            hit = hit ?? throw new ArgumentNullException(nameof(hit));
 
             return _pointer.Captured ??
                 (hit as IInteractive) ??
                 hit.GetSelfAndVisualAncestors().OfType<IInteractive>().FirstOrDefault();
         }
 
-        private IInputElement HitTest(IInputElement root, Point p)
+        private IInputElement? HitTest(IInputElement root, Point p)
         {
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             return _pointer.Captured ?? root.InputHitTest(p);
         }
 
-        PointerEventArgs CreateSimpleEvent(RoutedEvent ev, ulong timestamp, IInteractive source,
+        PointerEventArgs CreateSimpleEvent(RoutedEvent ev, ulong timestamp, IInteractive? source,
             PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
@@ -343,8 +348,8 @@ namespace Avalonia.Input
             PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             var element = root.PointerOverElement;
             var e = CreateSimpleEvent(InputElement.PointerLeaveEvent, timestamp, element, properties, inputModifiers);
@@ -384,12 +389,12 @@ namespace Avalonia.Input
             }
         }
 
-        private IInputElement SetPointerOver(IPointerDevice device, ulong timestamp, IInputRoot root, Point p, 
+        private IInputElement? SetPointerOver(IPointerDevice device, ulong timestamp, IInputRoot root, Point p, 
             PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
 
             var element = root.InputHitTest(p);
 
@@ -412,11 +417,11 @@ namespace Avalonia.Input
             PointerPointProperties properties,
             KeyModifiers inputModifiers)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
-            Contract.Requires<ArgumentNullException>(root != null);
+            root = root ?? throw new ArgumentNullException(nameof(root));
-            Contract.Requires<ArgumentNullException>(element != null);
+            element = element ?? throw new ArgumentNullException(nameof(element));
 
-            IInputElement branch = null;
+            IInputElement? branch = null;
 
             var el = element;
 

src/Avalonia.Input/Navigation/TabNavigation.cs

@@ -22,15 +22,17 @@ namespace Avalonia.Input.Navigation
         /// The next element in the specified direction, or null if <paramref name="element"/>
         /// was the last in the requested direction.
         /// </returns>
-        public static IInputElement GetNextInTabOrder(
+        public static IInputElement? GetNextInTabOrder(
             IInputElement element,
             NavigationDirection direction,
             bool outsideElement = false)
         {
-            Contract.Requires<ArgumentNullException>(element != null);
+            element = element ?? throw new ArgumentNullException(nameof(element));
-            Contract.Requires<ArgumentException>(
+
-                direction == NavigationDirection.Next ||
+            if (direction != NavigationDirection.Next && direction != NavigationDirection.Previous)
-                direction == NavigationDirection.Previous);
+            {
+                throw new ArgumentException("Invalid direction: must be Next or Previous.");
+            }
 
             var container = element.GetVisualParent<IInputElement>();
 
@@ -110,7 +112,7 @@ namespace Avalonia.Input.Navigation
 
                 if (customNext.handled)
                 {
-                    yield return customNext.next;
+                    yield return customNext.next!;
                 }
                 else
                 {
@@ -143,12 +145,14 @@ namespace Avalonia.Input.Navigation
         /// If true will not descend into <paramref name="element"/> to find next control.
         /// </param>
         /// <returns>The next element, or null if the element is the last.</returns>
-        private static IInputElement GetNextInContainer(
+        private static IInputElement? GetNextInContainer(
             IInputElement element,
             IInputElement container,
             NavigationDirection direction,
             bool outsideElement)
         {
+            IInputElement? e = element;
+
             if (direction == NavigationDirection.Next && !outsideElement)
             {
                 var descendant = GetFocusableDescendants(element, direction).FirstOrDefault();
@@ -167,13 +171,13 @@ namespace Avalonia.Input.Navigation
                 // INavigableContainer.
                 if (navigable != null)
                 {
-                    while (element != null)
+                    while (e != null)
                     {
-                        element = navigable.GetControl(direction, element, false);
+                        e = navigable.GetControl(direction, e, false);
 
-                        if (element != null && 
+                        if (e != null && 
-                            element.CanFocus() &&
+                            e.CanFocus() &&
-                            KeyboardNavigation.GetIsTabStop((InputElement) element))
+                            KeyboardNavigation.GetIsTabStop((InputElement)e))
                         {
                             break;
                         }
@@ -183,12 +187,12 @@ namespace Avalonia.Input.Navigation
                 {
                     // TODO: Do a spatial search here if the container doesn't implement
                     // INavigableContainer.
-                    element = null;
+                    e = null;
                 }
 
-                if (element != null && direction == NavigationDirection.Previous)
+                if (e != null && direction == NavigationDirection.Previous)
                 {
-                    var descendant = GetFocusableDescendants(element, direction).LastOrDefault();
+                    var descendant = GetFocusableDescendants(e, direction).LastOrDefault();
 
                     if (descendant != null)
                     {
@@ -196,7 +200,7 @@ namespace Avalonia.Input.Navigation
                     }
                 }
 
-                return element;
+                return e;
             }
 
             return null;
@@ -209,13 +213,13 @@ namespace Avalonia.Input.Navigation
         /// <param name="container">The container.</param>
         /// <param name="direction">The direction of the search.</param>
         /// <returns>The first element, or null if there are no more elements.</returns>
-        private static IInputElement GetFirstInNextContainer(
+        private static IInputElement? GetFirstInNextContainer(
             IInputElement element,
             IInputElement container,
             NavigationDirection direction)
         {
             var parent = container.GetVisualParent<IInputElement>();
-            IInputElement next = null;
+            IInputElement? next = null;
 
             if (parent != null)
             {
@@ -268,7 +272,7 @@ namespace Avalonia.Input.Navigation
             return next;
         }
 
-        private static (bool handled, IInputElement next) GetCustomNext(IInputElement element,
+        private static (bool handled, IInputElement? next) GetCustomNext(IInputElement element,
             NavigationDirection direction)
         {
             if (element is ICustomKeyboardNavigation custom)

src/Avalonia.Input/Pointer.cs

@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
-using Avalonia.Interactivity;
 using Avalonia.VisualTree;
 
 namespace Avalonia.Input
@@ -20,7 +19,7 @@ namespace Avalonia.Input
 
         public int Id { get; }
 
-        IInputElement FindCommonParent(IInputElement control1, IInputElement control2)
+        IInputElement? FindCommonParent(IInputElement? control1, IInputElement? control2)
         {
             if (control1 == null || control2 == null)
                 return null;
@@ -28,12 +27,12 @@ namespace Avalonia.Input
             return control2.GetSelfAndVisualAncestors().OfType<IInputElement>().FirstOrDefault(seen.Contains);
         }
 
-        protected virtual void PlatformCapture(IInputElement element)
+        protected virtual void PlatformCapture(IInputElement? element)
         {
             
         }
         
-        public void Capture(IInputElement control)
+        public void Capture(IInputElement? control)
         {
             if (Captured != null)
                 Captured.DetachedFromVisualTree -= OnCaptureDetached;
@@ -66,7 +65,7 @@ namespace Avalonia.Input
         }
 
 
-        public IInputElement Captured { get; private set; }
+        public IInputElement? Captured { get; private set; }
             
         public PointerType Type { get; }
         public bool IsPrimary { get; }

src/Avalonia.Input/PointerEventArgs.cs

@@ -7,14 +7,14 @@ namespace Avalonia.Input
 {
     public class PointerEventArgs : RoutedEventArgs
     {
-        private readonly IVisual _rootVisual;
+        private readonly IVisual? _rootVisual;
         private readonly Point _rootVisualPosition;
         private readonly PointerPointProperties _properties;
 
         public PointerEventArgs(RoutedEvent routedEvent,
-            IInteractive source,
+            IInteractive? source,
             IPointer pointer,
-            IVisual rootVisual, Point rootVisualPosition,
+            IVisual? rootVisual, Point rootVisualPosition,
             ulong timestamp,
             PointerPointProperties properties,
             KeyModifiers modifiers)
@@ -40,8 +40,8 @@ namespace Avalonia.Input
             
             public void ProcessRawEvent(RawInputEventArgs ev) => throw new NotSupportedException();
 
-            public IInputElement Captured => _ev.Pointer.Captured;
+            public IInputElement? Captured => _ev.Pointer.Captured;
-            public void Capture(IInputElement control)
+            public void Capture(IInputElement? control)
             {
                 _ev.Pointer.Capture(control);
             }
@@ -52,7 +52,7 @@ namespace Avalonia.Input
         public IPointer Pointer { get; }
         public ulong Timestamp { get; }
 
-        private IPointerDevice _device;
+        private IPointerDevice? _device;
 
         [Obsolete("Use Pointer to get pointer-specific information")]
         public IPointerDevice Device => _device ?? (_device = new EmulatedDevice(this));
@@ -76,7 +76,7 @@ namespace Avalonia.Input
         
         public KeyModifiers KeyModifiers { get; }
 
-        public Point GetPosition(IVisual relativeTo)
+        public Point GetPosition(IVisual? relativeTo)
         {
             if (_rootVisual == null)
                 return default;

src/Avalonia.Input/Raw/RawDragEventType.cs

@@ -7,4 +7,4 @@
         DragLeave,
         Drop
     }
-}
+}

src/Avalonia.Input/Raw/RawInputEventArgs.cs

@@ -21,7 +21,7 @@ namespace Avalonia.Input.Raw
         /// <param name="root">The root from which the event originates.</param>
         public RawInputEventArgs(IInputDevice device, ulong timestamp, IInputRoot root)
         {
-            Contract.Requires<ArgumentNullException>(device != null);
+            device = device ?? throw new ArgumentNullException(nameof(device));
 
             Device = device;
             Timestamp = timestamp;

src/Avalonia.Input/TextInputEventArgs.cs

@@ -4,8 +4,8 @@ namespace Avalonia.Input
 {
     public class TextInputEventArgs : RoutedEventArgs
     {
-        public IKeyboardDevice Device { get; set; }
+        public IKeyboardDevice? Device { get; set; }
 
-        public string Text { get; set; }
+        public string? Text { get; set; }
     }
 }

src/Avalonia.Layout/Layoutable.cs

@@ -758,8 +758,6 @@ namespace Avalonia.Layout
 
         protected override void OnDetachedFromVisualTreeCore(VisualTreeAttachmentEventArgs e)
         {
-            base.OnDetachedFromVisualTreeCore(e);
-
             if (e.Root is ILayoutRoot r)
             {
                 if (_layoutUpdated is object)
@@ -772,6 +770,8 @@ namespace Avalonia.Layout
                     r.LayoutManager.UnregisterEffectiveViewportListener(this);
                 }
             }
+
+            base.OnDetachedFromVisualTreeCore(e);
         }
 
         /// <summary>

src/Avalonia.OpenGL/Angle/AngleEglInterface.cs

@@ -0,0 +1,36 @@
+using System;
+using System.Runtime.InteropServices;
+using Avalonia.Platform;
+using Avalonia.Platform.Interop;
+
+namespace Avalonia.OpenGL.Angle
+{
+    public class AngleEglInterface : EglInterface
+    {
+        [DllImport("libegl.dll", CharSet = CharSet.Ansi)]
+        static extern IntPtr eglGetProcAddress(string proc);
+
+        public AngleEglInterface() : base(LoadAngle())
+        {
+
+        }
+
+        static Func<string, IntPtr> LoadAngle()
+        {
+            if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+            {
+                var disp = eglGetProcAddress("eglGetPlatformDisplayEXT");
+
+                if (disp == IntPtr.Zero)
+                {
+                    throw new OpenGlException("libegl.dll doesn't have eglGetPlatformDisplayEXT entry point");
+                }
+
+                return eglGetProcAddress;
+            }
+            
+            throw new PlatformNotSupportedException();
+        }
+
+    }
+}

src/Avalonia.OpenGL/Angle/AngleWin32EglDisplay.cs

@@ -0,0 +1,88 @@
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+
+using static Avalonia.OpenGL.EglConsts;
+
+namespace Avalonia.OpenGL.Angle
+{
+    public class AngleWin32EglDisplay : EglDisplay
+    {
+        struct AngleInfo
+        {
+            public IntPtr Display { get; set; }
+            public AngleOptions.PlatformApi PlatformApi { get; set; }
+        }
+        
+        static AngleInfo CreateAngleDisplay(EglInterface _egl)
+        {
+            if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                throw new PlatformNotSupportedException();
+            var display = IntPtr.Zero;
+            AngleOptions.PlatformApi angleApi = default;
+            {
+                if (_egl.GetPlatformDisplayEXT == null)
+                    throw new OpenGlException("eglGetPlatformDisplayEXT is not supported by libegl.dll");
+
+                var allowedApis = AvaloniaLocator.Current.GetService<AngleOptions>()?.AllowedPlatformApis
+                                  ?? new [] { AngleOptions.PlatformApi.DirectX11, AngleOptions.PlatformApi.DirectX9 };
+
+                foreach (var platformApi in allowedApis)
+                {
+                    int dapi;
+                    if (platformApi == AngleOptions.PlatformApi.DirectX9)
+                        dapi = EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE;
+                    else if (platformApi == AngleOptions.PlatformApi.DirectX11)
+                        dapi = EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE;
+                    else
+                        continue;
+
+                    display = _egl.GetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE, IntPtr.Zero,
+                        new[] { EGL_PLATFORM_ANGLE_TYPE_ANGLE, dapi, EGL_NONE });
+                    if (display != IntPtr.Zero)
+                    {
+                        angleApi = platformApi;
+                        break;
+                    }
+                }
+
+                if (display == IntPtr.Zero)
+                    throw new OpenGlException("Unable to create ANGLE display");
+                return new AngleInfo { Display = display, PlatformApi = angleApi };
+            }
+        }
+
+        private AngleWin32EglDisplay(EglInterface egl, AngleInfo info) : base(egl, info.Display)
+        {
+            PlatformApi = info.PlatformApi;
+        }
+
+        public AngleWin32EglDisplay(EglInterface egl) : this(egl, CreateAngleDisplay(egl))
+        {
+            
+        }
+
+        public AngleWin32EglDisplay() : this(new AngleEglInterface())
+        {
+
+        }
+
+        public AngleOptions.PlatformApi PlatformApi { get; }
+
+        public IntPtr GetDirect3DDevice()
+        {
+            if (!EglInterface.QueryDisplayAttribExt(Handle, EglConsts.EGL_DEVICE_EXT, out var eglDevice))
+                throw new OpenGlException("Unable to get EGL_DEVICE_EXT");
+            if (!EglInterface.QueryDeviceAttribExt(eglDevice, PlatformApi == AngleOptions.PlatformApi.DirectX9 ? EGL_D3D9_DEVICE_ANGLE : EGL_D3D11_DEVICE_ANGLE, out var d3dDeviceHandle))
+                throw new OpenGlException("Unable to get EGL_D3D9_DEVICE_ANGLE");
+            return d3dDeviceHandle;
+        }
+
+        public EglSurface WrapDirect3D11Texture(IntPtr handle)
+        {
+            if (PlatformApi != AngleOptions.PlatformApi.DirectX11)
+                throw new InvalidOperationException("Current platform API is " + PlatformApi);
+            return CreatePBufferFromClientBuffer(EGL_D3D_TEXTURE_ANGLE, handle, new[] { EGL_NONE, EGL_NONE });
+        }
+    }
+}

src/Avalonia.OpenGL/AngleOptions.cs

@@ -10,9 +10,6 @@ namespace Avalonia.OpenGL
 			DirectX11
         }
 
-        public List<PlatformApi> AllowedPlatformApis = new List<PlatformApi>
+        public IList<PlatformApi> AllowedPlatformApis { get; set; } = null;
-        {
-            PlatformApi.DirectX9
-        };
     }
 }

src/Avalonia.OpenGL/EglConsts.cs

@@ -186,11 +186,24 @@ namespace Avalonia.OpenGL
         public const int EGL_PLATFORM_ANGLE_TYPE_DEFAULT_ANGLE = 0x3206;
         public const int EGL_PLATFORM_ANGLE_DEVICE_TYPE_HARDWARE_ANGLE = 0x320A;
         public const int EGL_PLATFORM_ANGLE_DEVICE_TYPE_NULL_ANGLE = 0x345E;
+
+        public const int EGL_PLATFORM_ANGLE_TYPE_OPENGL_ANGLE = 0x320D;
+        public const int EGL_PLATFORM_ANGLE_TYPE_OPENGLES_ANGLE = 0x320E;
         
         //EGL_ANGLE_platform_angle_d3d
         public const int EGL_PLATFORM_ANGLE_DEVICE_TYPE_ANGLE = 0x3209;
         public const int EGL_PLATFORM_ANGLE_ENABLE_AUTOMATIC_TRIM_ANGLE = 0x320F;
         public const int EGL_PLATFORM_ANGLE_DEVICE_TYPE_D3D_WARP_ANGLE = 0x320B;
         public const int EGL_PLATFORM_ANGLE_DEVICE_TYPE_D3D_REFERENCE_ANGLE = 0x320C;
+        
+        //EXT_device_query
+        public const int EGL_DEVICE_EXT = 0x322C;
+
+        //ANGLE_device_d3d
+        public const int EGL_D3D9_DEVICE_ANGLE = 0x33A0;
+        public const int EGL_D3D11_DEVICE_ANGLE = 0x33A1;
+
+        public const int EGL_D3D_TEXTURE_2D_SHARE_HANDLE_ANGLE = 0x3200;
+        public const int EGL_D3D_TEXTURE_ANGLE = 0x33A3;
     }
 }

src/Avalonia.OpenGL/EglDisplay.cs

@@ -15,7 +15,6 @@ namespace Avalonia.OpenGL
         private readonly int _surfaceType;
 
         public IntPtr Handle => _display;
-        private AngleOptions.PlatformApi? _angleApi;
         private int _sampleCount;
         private int _stencilSize;
         private GlVersion _version;
@@ -24,56 +23,41 @@ namespace Avalonia.OpenGL
         {
             
         }
-        public EglDisplay(EglInterface egl, int platformType, IntPtr platformDisplay, int[] attrs)
-        {
-            _egl = egl;
 
+        static IntPtr CreateDisplay(EglInterface egl, int platformType, IntPtr platformDisplay, int[] attrs)
+        {
+            var display = IntPtr.Zero;
             if (platformType == -1 && platformDisplay == IntPtr.Zero)
             {
-                if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+                if (display == IntPtr.Zero)
-                {
+                    display = egl.GetDisplay(IntPtr.Zero);
-                    if (_egl.GetPlatformDisplayEXT == null)
-                        throw new OpenGlException("eglGetPlatformDisplayEXT is not supported by libegl.dll");
-
-                    var allowedApis = AvaloniaLocator.Current.GetService<AngleOptions>()?.AllowedPlatformApis
-                                      ?? new List<AngleOptions.PlatformApi> {AngleOptions.PlatformApi.DirectX9};
-
-                    foreach (var platformApi in allowedApis)
-                    {
-                        int dapi;
-                        if (platformApi == AngleOptions.PlatformApi.DirectX9)
-                            dapi = EGL_PLATFORM_ANGLE_TYPE_D3D9_ANGLE;
-                        else if (platformApi == AngleOptions.PlatformApi.DirectX11)
-                            dapi = EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE;
-                        else
-                            continue;
-
-                        _display = _egl.GetPlatformDisplayEXT(EGL_PLATFORM_ANGLE_ANGLE, IntPtr.Zero,
-                            new[] {EGL_PLATFORM_ANGLE_TYPE_ANGLE, dapi, EGL_NONE});
-                        if (_display != IntPtr.Zero)
-                        {
-                            _angleApi = platformApi;
-                            break;
-                        }
-                    }
-
-                    if (_display == IntPtr.Zero)
-                        throw new OpenGlException("Unable to create ANGLE display");
-                }
-
-                if (_display == IntPtr.Zero)
-                    _display = _egl.GetDisplay(IntPtr.Zero);
             }
             else
             {
-                if (_egl.GetPlatformDisplayEXT == null)
+                if (egl.GetPlatformDisplayEXT == null)
                     throw new OpenGlException("eglGetPlatformDisplayEXT is not supported by libegl");
-                _display = _egl.GetPlatformDisplayEXT(platformType, platformDisplay, attrs);
+                display = egl.GetPlatformDisplayEXT(platformType, platformDisplay, attrs);
             }
+            
+            if (display == IntPtr.Zero)
+                throw OpenGlException.GetFormattedException("eglGetDisplay", egl);
+            return display;
+        }
 
-            if (_display == IntPtr.Zero)
+        public EglDisplay(EglInterface egl, int platformType, IntPtr platformDisplay, int[] attrs)
-                throw OpenGlException.GetFormattedException("eglGetDisplay", _egl);
+            : this(egl, CreateDisplay(egl, platformType, platformDisplay, attrs))
+        {
+
+        }
 
+        public EglDisplay(EglInterface egl, IntPtr display)
+        {
+            _egl = egl;
+            _display = display;
+            if(_display == IntPtr.Zero)
+                throw new ArgumentException();
+            
+            
             if (!_egl.Initialize(_display, out var major, out var minor))
                 throw OpenGlException.GetFormattedException("eglInitialize", _egl);
 
@@ -172,5 +156,15 @@ namespace Avalonia.OpenGL
                 throw OpenGlException.GetFormattedException("eglCreateWindowSurface", _egl);
             return new EglSurface(this, _egl, s);
         }
+        
+        public EglSurface CreatePBufferFromClientBuffer (int bufferType, IntPtr handle, int[] attribs)
+        {
+            var s = _egl.CreatePbufferFromClientBuffer(_display, bufferType, handle,
+                _config, attribs);         
+
+            if (s == IntPtr.Zero)
+                throw OpenGlException.GetFormattedException("eglCreatePbufferFromClientBuffer", _egl);
+            return new EglSurface(this, _egl, s);
+        }
     }
 }

src/Avalonia.OpenGL/EglGlPlatformFeature.cs

@@ -20,12 +20,13 @@ namespace Avalonia.OpenGL
             if (feature != null)
                 AvaloniaLocator.CurrentMutable.Bind<IWindowingPlatformGlFeature>().ToConstant(feature);
         }
-        
+
-        public static EglGlPlatformFeature TryCreate()
+        public static EglGlPlatformFeature TryCreate() => TryCreate(() => new EglDisplay());
+        public static EglGlPlatformFeature TryCreate(Func<EglDisplay> displayFactory)
         {
             try
             {
-                var disp = new EglDisplay();
+                var disp = displayFactory();
                 return new EglGlPlatformFeature
                 {
                     _display = disp,

src/Avalonia.OpenGL/EglGlPlatformSurface.cs

@@ -3,33 +3,26 @@ using System.Threading;
 
 namespace Avalonia.OpenGL
 {
-    public class EglGlPlatformSurface : IGlPlatformSurface
+    public class EglGlPlatformSurface : EglGlPlatformSurfaceBase
     {
-        public interface IEglWindowGlPlatformSurfaceInfo
-        {
-            IntPtr Handle { get; }
-            PixelSize Size { get; }
-            double Scaling { get; }
-        }
-
         private readonly EglDisplay _display;
         private readonly EglContext _context;
         private readonly IEglWindowGlPlatformSurfaceInfo _info;
         
-        public EglGlPlatformSurface(EglContext context, IEglWindowGlPlatformSurfaceInfo info)
+        public EglGlPlatformSurface(EglContext context, IEglWindowGlPlatformSurfaceInfo info) : base()
         {
             _display = context.Display;
             _context = context;
             _info = info;
         }
-        
+
-        public IGlPlatformSurfaceRenderTarget CreateGlRenderTarget()
+        public override IGlPlatformSurfaceRenderTarget CreateGlRenderTarget()
         {
             var glSurface = _display.CreateWindowSurface(_info.Handle);
             return new RenderTarget(_display, _context, glSurface, _info);
         }
 
-        class RenderTarget : IGlPlatformSurfaceRenderTargetWithCorruptionInfo
+        class RenderTarget : EglPlatformSurfaceRenderTargetBase
         {
             private readonly EglDisplay _display;
             private readonly EglContext _context;
@@ -38,7 +31,7 @@ namespace Avalonia.OpenGL
             private PixelSize _initialSize;
 
             public RenderTarget(EglDisplay display, EglContext context,
-                EglSurface glSurface, IEglWindowGlPlatformSurfaceInfo info)
+                EglSurface glSurface, IEglWindowGlPlatformSurfaceInfo info) : base(display, context)
             {
                 _display = display;
                 _context = context;
@@ -47,70 +40,11 @@ namespace Avalonia.OpenGL
                 _initialSize = info.Size;
             }
 
-            public void Dispose() => _glSurface.Dispose();
+            public override void Dispose() => _glSurface.Dispose();
 
-            public bool IsCorrupted => _initialSize != _info.Size;
+            public override bool IsCorrupted => _initialSize != _info.Size;
-            
-            public IGlPlatformSurfaceRenderingSession BeginDraw()
-            {
-                var l = _context.Lock();
-                try
-                {
-                    if (IsCorrupted)
-                        throw new RenderTargetCorruptedException();
-                    var restoreContext = _context.MakeCurrent(_glSurface);
-                    _display.EglInterface.WaitClient();
-                    _display.EglInterface.WaitGL();
-                    _display.EglInterface.WaitNative(EglConsts.EGL_CORE_NATIVE_ENGINE);
-                    
-                    return new Session(_display, _context, _glSurface, _info, l, restoreContext);
-                }
-                catch
-                {
-                    l.Dispose();
-                    throw;
-                }
-            }
             
-            class Session : IGlPlatformSurfaceRenderingSession
+            public override IGlPlatformSurfaceRenderingSession BeginDraw() => base.BeginDraw(_glSurface, _info);
-            {
-                private readonly EglContext _context;
-                private readonly EglSurface _glSurface;
-                private readonly IEglWindowGlPlatformSurfaceInfo _info;
-                private readonly EglDisplay _display;
-                private IDisposable _lock;
-                private readonly IDisposable _restoreContext;
-
-
-                public Session(EglDisplay display, EglContext context,
-                    EglSurface glSurface, IEglWindowGlPlatformSurfaceInfo info,
-                    IDisposable @lock, IDisposable restoreContext)
-                {
-                    _context = context;
-                    _display = display;
-                    _glSurface = glSurface;
-                    _info = info;
-                    _lock = @lock;
-                    _restoreContext = restoreContext;
-                }
-
-                public void Dispose()
-                {
-                    _context.GlInterface.Flush();
-                    _display.EglInterface.WaitGL();
-                    _glSurface.SwapBuffers();
-                    _display.EglInterface.WaitClient();
-                    _display.EglInterface.WaitGL();
-                    _display.EglInterface.WaitNative(EglConsts.EGL_CORE_NATIVE_ENGINE);
-                    _restoreContext.Dispose();
-                    _lock.Dispose();
-                }
-
-                public IGlContext Context => _context;
-                public PixelSize Size => _info.Size;
-                public double Scaling => _info.Scaling;
-                public bool IsYFlipped { get; }
-            }
         }
     }
 }

src/Avalonia.OpenGL/EglGlPlatformSurfaceBase.cs

@@ -0,0 +1,103 @@
+using System;
+
+namespace Avalonia.OpenGL
+{
+    public abstract class EglGlPlatformSurfaceBase : IGlPlatformSurface
+    {
+        public interface IEglWindowGlPlatformSurfaceInfo
+        {
+            IntPtr Handle { get; }
+            PixelSize Size { get; }
+            double Scaling { get; }
+        }
+
+        public abstract IGlPlatformSurfaceRenderTarget CreateGlRenderTarget();
+    }
+
+    public abstract class EglPlatformSurfaceRenderTargetBase  : IGlPlatformSurfaceRenderTargetWithCorruptionInfo
+    {
+        private readonly EglDisplay _display;
+        private readonly EglContext _context;
+
+        protected EglPlatformSurfaceRenderTargetBase(EglDisplay display, EglContext context)
+        {
+            _display = display;
+            _context = context;
+        }
+
+        public abstract bool IsCorrupted { get; }
+
+        public virtual void Dispose()
+        {
+            
+        }
+
+        public abstract IGlPlatformSurfaceRenderingSession BeginDraw();
+
+        protected IGlPlatformSurfaceRenderingSession BeginDraw(EglSurface surface,
+            EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo info, Action onFinish = null, bool isYFlipped = false)
+        {
+            var l = _context.Lock();
+            try
+            {
+                if (IsCorrupted)
+                    throw new RenderTargetCorruptedException();
+                var restoreContext = _context.MakeCurrent(surface);
+                _display.EglInterface.WaitClient();
+                _display.EglInterface.WaitGL();
+                _display.EglInterface.WaitNative(EglConsts.EGL_CORE_NATIVE_ENGINE);
+                    
+                return new Session(_display, _context, surface, info, l, restoreContext, onFinish, isYFlipped);
+            }
+            catch
+            {
+                l.Dispose();
+                throw;
+            }
+        }
+        
+        class Session : IGlPlatformSurfaceRenderingSession
+        {
+            private readonly EglContext _context;
+            private readonly EglSurface _glSurface;
+            private readonly EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo _info;
+            private readonly EglDisplay _display;
+            private readonly IDisposable _lock;
+            private readonly IDisposable _restoreContext;
+            private readonly Action _onFinish;
+
+
+            public Session(EglDisplay display, EglContext context,
+                EglSurface glSurface, EglGlPlatformSurfaceBase.IEglWindowGlPlatformSurfaceInfo info,
+                IDisposable @lock, IDisposable restoreContext, Action onFinish, bool isYFlipped)
+            {
+                IsYFlipped = isYFlipped;
+                _context = context;
+                _display = display;
+                _glSurface = glSurface;
+                _info = info;
+                _lock = @lock;
+                _restoreContext = restoreContext;
+                _onFinish = onFinish;
+            }
+
+            public void Dispose()
+            {
+                _context.GlInterface.Flush();
+                _display.EglInterface.WaitGL();
+                _glSurface.SwapBuffers();
+                _display.EglInterface.WaitClient();
+                _display.EglInterface.WaitGL();
+                _display.EglInterface.WaitNative(EglConsts.EGL_CORE_NATIVE_ENGINE);
+                _restoreContext.Dispose();
+                _lock.Dispose();
+                _onFinish?.Invoke();
+            }
+
+            public IGlContext Context => _context;
+            public PixelSize Size => _info.Size;
+            public double Scaling => _info.Scaling;
+            public bool IsYFlipped { get; }
+        }
+    }
+}

src/Avalonia.OpenGL/EglInterface.cs

@@ -17,25 +17,21 @@ namespace Avalonia.OpenGL
             
         }
         
+        public EglInterface(Func<string, IntPtr> getProcAddress) : base(getProcAddress)
+        {
+            
+        }
+        
         public EglInterface(string library) : base(Load(library))
         {
         }
 
-        [DllImport("libegl.dll", CharSet = CharSet.Ansi)]
-        static extern IntPtr eglGetProcAddress(string proc);
         
         static Func<string, IntPtr> Load()
         {
             var os = AvaloniaLocator.Current.GetService<IRuntimePlatform>().GetRuntimeInfo().OperatingSystem;
             if(os == OperatingSystemType.Linux || os == OperatingSystemType.Android)
                 return Load("libEGL.so.1");
-            if (os == OperatingSystemType.WinNT)
-            {
-                var disp = eglGetProcAddress("eglGetPlatformDisplayEXT");
-                if (disp == IntPtr.Zero)
-                    throw new OpenGlException("libegl.dll doesn't have eglGetPlatformDisplayEXT entry point");
-                return eglGetProcAddress;
-            }
 
             throw new PlatformNotSupportedException();
         }
@@ -147,6 +143,21 @@ namespace Avalonia.OpenGL
                 return null;
             return Marshal.PtrToStringAnsi(rv);
         }
+        
+        public delegate IntPtr EglCreatePbufferFromClientBuffer(IntPtr display, int buftype, IntPtr buffer, IntPtr config, int[] attrib_list);
+        [GlEntryPoint("eglCreatePbufferFromClientBuffer")]
+
+        public EglCreatePbufferFromClientBuffer CreatePbufferFromClientBuffer { get; }
+        
+        public delegate bool EglQueryDisplayAttribEXT(IntPtr display, int attr, out IntPtr res);
+
+        [GlEntryPoint("eglQueryDisplayAttribEXT"), GlOptionalEntryPoint]
+        public EglQueryDisplayAttribEXT QueryDisplayAttribExt { get; }
+
+        public delegate bool EglQueryDeviceAttribEXT(IntPtr display, int attr, out IntPtr res);
+
+        [GlEntryPoint("eglQueryDeviceAttribEXT"), GlOptionalEntryPoint]
+        public EglQueryDisplayAttribEXT QueryDeviceAttribExt { get; }
 
         // ReSharper restore UnassignedGetOnlyAutoProperty
     }

src/Avalonia.Themes.Fluent/CheckBox.xaml

@@ -8,11 +8,11 @@
     <Setter Property="Background" Value="{DynamicResource CheckBoxBackgroundUnchecked}" />
     <Setter Property="Foreground" Value="{DynamicResource CheckBoxForegroundUnchecked}" />
     <Setter Property="BorderBrush" Value="{DynamicResource CheckBoxBorderBrushUnchecked}" />
-    <Setter Property="Padding" Value="8,5,0,0" />
+    <Setter Property="Padding" Value="8,0,0,0" />
     <Setter Property="HorizontalAlignment" Value="Left" />
     <Setter Property="VerticalAlignment" Value="Center" />
     <Setter Property="HorizontalContentAlignment" Value="Left" />
-    <Setter Property="VerticalContentAlignment" Value="Top" />    
+    <Setter Property="VerticalContentAlignment" Value="Center" />    
     <Setter Property="FontSize" Value="{DynamicResource ControlContentThemeFontSize}" />
     <Setter Property="MinWidth" Value="120" />
     <Setter Property="MinHeight" Value="32" />

src/Avalonia.Themes.Fluent/RadioButton.xaml

@@ -13,11 +13,11 @@
     <Setter Property="Background" Value="{DynamicResource RadioButtonBackground}" />
     <Setter Property="Foreground" Value="{DynamicResource RadioButtonForeground}" />
     <Setter Property="BorderBrush" Value="{DynamicResource RadioButtonBorderBrush}" />
-    <Setter Property="Padding" Value="8,6,0,0" />
+    <Setter Property="Padding" Value="8,0,0,0" />
     <Setter Property="HorizontalAlignment" Value="Left" />
     <Setter Property="VerticalAlignment" Value="Center" />
     <Setter Property="HorizontalContentAlignment" Value="Left" />
-    <Setter Property="VerticalContentAlignment" Value="Top" />    
+    <Setter Property="VerticalContentAlignment" Value="Center" />    
     <Setter Property="FontSize" Value="{DynamicResource ControlContentThemeFontSize}" />
     <Setter Property="MinWidth" Value="120" />
     <Setter Property="Template">

src/Avalonia.Visuals/ApiCompatBaseline.txt

@@ -1,5 +1,15 @@
 Compat issues with assembly Avalonia.Visuals:
+MembersMustExist : Member 'public Avalonia.Media.Typeface Avalonia.Media.FontManager.GetOrAddTypeface(Avalonia.Media.FontFamily, Avalonia.Media.FontStyle, Avalonia.Media.FontWeight)' does not exist in the implementation but it does exist in the contract.
+MembersMustExist : Member 'public Avalonia.Media.Typeface Avalonia.Media.FontManager.MatchCharacter(System.Int32, Avalonia.Media.FontStyle, Avalonia.Media.FontWeight, Avalonia.Media.FontFamily, System.Globalization.CultureInfo)' does not exist in the implementation but it does exist in the contract.
+CannotSealType : Type 'Avalonia.Media.Typeface' is actually (has the sealed modifier) sealed in the implementation but not sealed in the contract.
+TypeCannotChangeClassification : Type 'Avalonia.Media.Typeface' is a 'struct' in the implementation but is a 'class' in the contract.
+CannotMakeMemberNonVirtual : Member 'public System.Boolean Avalonia.Media.Typeface.Equals(System.Object)' is non-virtual in the implementation but is virtual in the contract.
+CannotMakeMemberNonVirtual : Member 'public System.Int32 Avalonia.Media.Typeface.GetHashCode()' is non-virtual in the implementation but is virtual in the contract.
+TypesMustExist : Type 'Avalonia.Media.Fonts.FontKey' does not exist in the implementation but it does exist in the contract.
 CannotAddAbstractMembers : Member 'public Avalonia.Media.TextFormatting.TextLineBreak Avalonia.Media.TextFormatting.TextLine.TextLineBreak' is abstract in the implementation but is missing in the contract.
 MembersMustExist : Member 'public Avalonia.Media.TextFormatting.TextLineBreak Avalonia.Media.TextFormatting.TextLine.LineBreak.get()' does not exist in the implementation but it does exist in the contract.
 CannotAddAbstractMembers : Member 'public Avalonia.Media.TextFormatting.TextLineBreak Avalonia.Media.TextFormatting.TextLine.TextLineBreak.get()' is abstract in the implementation but is missing in the contract.
-Total Issues: 3
+InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Platform.IFontManagerImpl.TryMatchCharacter(System.Int32, Avalonia.Media.FontStyle, Avalonia.Media.FontWeight, Avalonia.Media.FontFamily, System.Globalization.CultureInfo, Avalonia.Media.Fonts.FontKey)' is present in the contract but not in the implementation.
+MembersMustExist : Member 'public System.Boolean Avalonia.Platform.IFontManagerImpl.TryMatchCharacter(System.Int32, Avalonia.Media.FontStyle, Avalonia.Media.FontWeight, Avalonia.Media.FontFamily, System.Globalization.CultureInfo, Avalonia.Media.Fonts.FontKey)' does not exist in the implementation but it does exist in the contract.
+InterfacesShouldHaveSameMembers : Interface member 'public System.Boolean Avalonia.Platform.IFontManagerImpl.TryMatchCharacter(System.Int32, Avalonia.Media.FontStyle, Avalonia.Media.FontWeight, Avalonia.Media.FontFamily, System.Globalization.CultureInfo, Avalonia.Media.Typeface)' is present in the implementation but not in the contract.
+Total Issues: 13

src/Avalonia.Visuals/Media/FontManager.cs

@@ -13,8 +13,8 @@ namespace Avalonia.Media
     /// </summary>
     public sealed class FontManager
     {
-        private readonly ConcurrentDictionary<FontKey, Typeface> _typefaceCache =
+        private readonly ConcurrentDictionary<Typeface, GlyphTypeface> _glyphTypefaceCache =
-            new ConcurrentDictionary<FontKey, Typeface>();
+            new ConcurrentDictionary<Typeface, GlyphTypeface>();
         private readonly FontFamily _defaultFontFamily;
 
         public FontManager(IFontManagerImpl platformImpl)
@@ -76,79 +76,52 @@ namespace Avalonia.Media
             PlatformImpl.GetInstalledFontFamilyNames(checkForUpdates);
 
         /// <summary>
-        ///     Returns a new typeface, or an existing one if a matching typeface exists.
+        ///     Returns a new <see cref="GlyphTypeface"/>, or an existing one if a matching <see cref="GlyphTypeface"/> exists.
         /// </summary>
-        /// <param name="fontFamily">The font family.</param>
+        /// <param name="typeface">The typeface.</param>
-        /// <param name="fontStyle">The font style.</param>
-        /// <param name="fontWeight">The font weight.</param>
         /// <returns>
-        ///     The typeface.
+        ///     The <see cref="GlyphTypeface"/>.
         /// </returns>
-        public Typeface GetOrAddTypeface(FontFamily fontFamily, FontStyle fontStyle = FontStyle.Normal,
+        public GlyphTypeface GetOrAddGlyphTypeface(Typeface typeface)
-            FontWeight fontWeight = FontWeight.Normal)
         {
             while (true)
             {
-                if (fontFamily.IsDefault)
+                if (_glyphTypefaceCache.TryGetValue(typeface, out var glyphTypeface))
                 {
-                    fontFamily = _defaultFontFamily;
+                    return glyphTypeface;
                 }
 
-                var key = new FontKey(fontFamily.Name, fontStyle, fontWeight);
+                glyphTypeface = new GlyphTypeface(typeface);
 
-                if (_typefaceCache.TryGetValue(key, out var typeface))
+                if (_glyphTypefaceCache.TryAdd(typeface, glyphTypeface))
                 {
-                    return typeface;
+                    return glyphTypeface;
                 }
 
-                typeface = new Typeface(fontFamily, fontStyle, fontWeight);
+                if (typeface.FontFamily == _defaultFontFamily)
-
-                if (_typefaceCache.TryAdd(key, typeface))
-                {
-                    return typeface;
-                }
-
-                if (fontFamily == _defaultFontFamily)
                 {
                     return null;
                 }
 
-                fontFamily = _defaultFontFamily;
+                typeface = new Typeface(_defaultFontFamily, typeface.Style, typeface.Weight);
             }
         }
 
         /// <summary>
-        ///     Tries to match a specified character to a typeface that supports specified font properties.
+        ///     Tries to match a specified character to a <see cref="Typeface"/> that supports specified font properties.
-        ///     Returns <c>null</c> if no fallback was found.
         /// </summary>
         /// <param name="codepoint">The codepoint to match against.</param>
         /// <param name="fontStyle">The font style.</param>
         /// <param name="fontWeight">The font weight.</param>
         /// <param name="fontFamily">The font family. This is optional and used for fallback lookup.</param>
         /// <param name="culture">The culture.</param>
+        /// <param name="typeface">The matching <see cref="Typeface"/>.</param>
         /// <returns>
-        ///     The matched typeface.
+        ///     <c>True</c>, if the <see cref="FontManager"/> could match the character to specified parameters, <c>False</c> otherwise.
         /// </returns>
-        public Typeface MatchCharacter(int codepoint,
+        public bool TryMatchCharacter(int codepoint, FontStyle fontStyle,
-            FontStyle fontStyle = FontStyle.Normal,
+            FontWeight fontWeight,
-            FontWeight fontWeight = FontWeight.Normal,
+            FontFamily fontFamily, CultureInfo culture, out Typeface typeface) =>
-            FontFamily fontFamily = null, CultureInfo culture = null)
+            PlatformImpl.TryMatchCharacter(codepoint, fontStyle, fontWeight, fontFamily, culture, out typeface);
-        {
-            foreach (var cachedTypeface in _typefaceCache.Values)
-            {
-                // First try to find a cached typeface by style and weight to avoid redundant glyph index lookup.
-                if (cachedTypeface.Style == fontStyle && cachedTypeface.Weight == fontWeight
-                                                      && cachedTypeface.GlyphTypeface.GetGlyph((uint)codepoint) != 0)
-                {
-                    return cachedTypeface;
-                }
-            }
-
-            var matchedTypeface = PlatformImpl.TryMatchCharacter(codepoint, fontStyle, fontWeight, fontFamily, culture, out var key) ?
-                _typefaceCache.GetOrAdd(key, new Typeface(key.FamilyName, key.Style, key.Weight)) :
-                null;
-
-            return matchedTypeface;
-        }
     }
 }

src/Avalonia.Visuals/Media/Fonts/FontKey.cs

@@ -1,40 +0,0 @@
-using System;
-
-namespace Avalonia.Media.Fonts
-{
-    public readonly struct FontKey : IEquatable<FontKey>
-    {
-        public FontKey(string familyName, FontStyle style, FontWeight weight)
-        {
-            FamilyName = familyName;
-            Style = style;
-            Weight = weight;
-        }
-
-        public string FamilyName { get; }
-        public FontStyle Style { get; }
-        public FontWeight Weight { get; }
-
-        public override int GetHashCode()
-        {
-            var hash = FamilyName.GetHashCode();
-
-            hash = hash * 31 + (int)Style;
-            hash = hash * 31 + (int)Weight;
-
-            return hash;
-        }
-
-        public override bool Equals(object other)
-        {
-            return other is FontKey key && Equals(key);
-        }
-
-        public bool Equals(FontKey other)
-        {
-            return FamilyName == other.FamilyName &&
-                Style == other.Style &&
-                   Weight == other.Weight;
-        }
-    }
-}

src/Avalonia.Visuals/Media/TextFormatting/TextCharacters.cs

@@ -70,10 +70,11 @@ namespace Avalonia.Media.TextFormatting
             var codepoint = Codepoint.ReadAt(text, count, out _);
 
             //ToDo: Fix FontFamily fallback
-            currentTypeface =
+            var matchFound =
-                FontManager.Current.MatchCharacter(codepoint, defaultTypeface.Style, defaultTypeface.Weight, defaultTypeface.FontFamily);
+                FontManager.Current.TryMatchCharacter(codepoint, defaultTypeface.Style, defaultTypeface.Weight,
+                    defaultTypeface.FontFamily, defaultProperties.CultureInfo, out currentTypeface);
 
-            if (currentTypeface != null && TryGetRunProperties(text, currentTypeface, defaultTypeface, out count))
+            if (matchFound && TryGetRunProperties(text, currentTypeface, defaultTypeface, out count))
             {
                 //Fallback found
                 return new ShapeableTextCharacters(text.Take(count),

src/Avalonia.Visuals/Media/Typeface.cs

@@ -8,17 +8,15 @@ namespace Avalonia.Media
     /// Represents a typeface.
     /// </summary>
     [DebuggerDisplay("Name = {FontFamily.Name}, Weight = {Weight}, Style = {Style}")]
-    public class Typeface : IEquatable<Typeface>
+    public readonly struct Typeface : IEquatable<Typeface>
     {
-        private GlyphTypeface _glyphTypeface;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="Typeface"/> class.
         /// </summary>
         /// <param name="fontFamily">The font family.</param>
         /// <param name="style">The font style.</param>
         /// <param name="weight">The font weight.</param>
-        public Typeface([NotNull]FontFamily fontFamily,
+        public Typeface([NotNull] FontFamily fontFamily,
             FontStyle style = FontStyle.Normal,
             FontWeight weight = FontWeight.Normal)
         {
@@ -45,7 +43,7 @@ namespace Avalonia.Media
         {
         }
 
-        public static Typeface Default => FontManager.Current?.GetOrAddTypeface(FontFamily.Default);
+        public static Typeface Default { get; } = new Typeface(FontFamily.Default);
 
         /// <summary>
         /// Gets the font family.
@@ -68,7 +66,7 @@ namespace Avalonia.Media
         /// <value>
         /// The glyph typeface.
         /// </value>
-        public GlyphTypeface GlyphTypeface => _glyphTypeface ?? (_glyphTypeface = new GlyphTypeface(this));
+        public GlyphTypeface GlyphTypeface => FontManager.Current.GetOrAddGlyphTypeface(this);
 
         public static bool operator !=(Typeface a, Typeface b)
         {
@@ -77,32 +75,17 @@ namespace Avalonia.Media
 
         public static bool operator ==(Typeface a, Typeface b)
         {
-            if (ReferenceEquals(a, b))
+            return  a.Equals(b);
-            {
-                return true;
-            }
-
-            return !(a is null) && a.Equals(b);
         }
 
         public override bool Equals(object obj)
         {
-            if (obj is Typeface typeface)
+            return obj is Typeface typeface && Equals(typeface);
-            {
-                return Equals(typeface);
-            }
-
-            return false;
         }
 
         public bool Equals(Typeface other)
         {
-            if (other is null)
+            return FontFamily == other.FontFamily && Style == other.Style && Weight == other.Weight;
-            {
-                return false;
-            }
-
-            return FontFamily.Equals(other.FontFamily) && Style == other.Style && Weight == other.Weight;
         }
 
         public override int GetHashCode()

src/Avalonia.Visuals/Platform/IFontManagerImpl.cs

@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using Avalonia.Media;
-using Avalonia.Media.Fonts;
 
 namespace Avalonia.Platform
 {
@@ -26,13 +25,13 @@ namespace Avalonia.Platform
         /// <param name="fontWeight">The font weight.</param>
         /// <param name="fontFamily">The font family. This is optional and used for fallback lookup.</param>
         /// <param name="culture">The culture.</param>
-        /// <param name="fontKey">The matching font key.</param>
+        /// <param name="typeface">The matching typeface.</param>
         /// <returns>
         ///     <c>True</c>, if the <see cref="IFontManagerImpl"/> could match the character to specified parameters, <c>False</c> otherwise.
         /// </returns>
         bool TryMatchCharacter(int codepoint, FontStyle fontStyle,
             FontWeight fontWeight,
-            FontFamily fontFamily, CultureInfo culture, out FontKey fontKey);
+            FontFamily fontFamily, CultureInfo culture, out Typeface typeface);
 
         /// <summary>
         ///     Creates a glyph typeface.

src/Avalonia.Visuals/Rendering/RenderLayer.cs

@@ -30,12 +30,13 @@ namespace Avalonia.Rendering
         {
             if (Size != size || Scaling != scaling)
             {
+                Bitmap.Dispose();
                 var resized = RefCountable.Create(drawingContext.CreateLayer(size));
 
                 using (var context = resized.Item.CreateDrawingContext(null))
                 {
                     context.Clear(Colors.Transparent);
-                    Bitmap.Dispose();
+                    
                     Bitmap = resized;
                     Scaling = scaling;
                     Size = size;

src/Avalonia.Visuals/Rendering/RendererBase.cs

@@ -20,7 +20,7 @@ namespace Avalonia.Rendering
             _useManualFpsCounting = useManualFpsCounting;
             _fpsText = new FormattedText
             {
-                Typeface = FontManager.Current?.GetOrAddTypeface(FontFamily.Default),
+                Typeface = new Typeface(FontFamily.Default),
                 FontSize = s_fontSize
             };
         }

src/Skia/Avalonia.Skia/FontManagerImpl.cs

@@ -2,7 +2,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using Avalonia.Media;
-using Avalonia.Media.Fonts;
 using Avalonia.Platform;
 using SkiaSharp;
 
@@ -31,7 +30,7 @@ namespace Avalonia.Skia
 
         public bool TryMatchCharacter(int codepoint, FontStyle fontStyle,
             FontWeight fontWeight,
-            FontFamily fontFamily, CultureInfo culture, out FontKey fontKey)
+            FontFamily fontFamily, CultureInfo culture, out Typeface fontKey)
         {
             SKFontStyle skFontStyle;
 
@@ -81,7 +80,7 @@ namespace Avalonia.Skia
                         continue;
                     }
 
-                    fontKey = new FontKey(skTypeface.FamilyName, fontStyle, fontWeight);
+                    fontKey = new Typeface(skTypeface.FamilyName, fontStyle, fontWeight);
 
                     return true;
                 }
@@ -92,7 +91,7 @@ namespace Avalonia.Skia
 
                 if (skTypeface != null)
                 {
-                    fontKey = new FontKey(skTypeface.FamilyName, fontStyle, fontWeight);
+                    fontKey = new Typeface(skTypeface.FamilyName, fontStyle, fontWeight);
 
                     return true;
                 }

src/Skia/Avalonia.Skia/SKTypefaceCollection.cs

@@ -2,31 +2,28 @@ using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Media;
-using Avalonia.Media.Fonts;
 using SkiaSharp;
 
 namespace Avalonia.Skia
 {
     internal class SKTypefaceCollection
     {
-        private readonly ConcurrentDictionary<FontKey, SKTypeface> _typefaces =
+        private readonly ConcurrentDictionary<Typeface, SKTypeface> _typefaces =
-            new ConcurrentDictionary<FontKey, SKTypeface>();
+            new ConcurrentDictionary<Typeface, SKTypeface>();
 
-        public void AddTypeface(FontKey key, SKTypeface typeface)
+        public void AddTypeface(Typeface key, SKTypeface typeface)
         {
             _typefaces.TryAdd(key, typeface);
         }
 
         public SKTypeface Get(Typeface typeface)
         {
-            var key = new FontKey(typeface.FontFamily.Name, typeface.Style, typeface.Weight);
+            return GetNearestMatch(_typefaces, typeface);
-
-            return GetNearestMatch(_typefaces, key);
         }
 
-        private static SKTypeface GetNearestMatch(IDictionary<FontKey, SKTypeface> typefaces, FontKey key)
+        private static SKTypeface GetNearestMatch(IDictionary<Typeface, SKTypeface> typefaces, Typeface key)
         {
-            if (typefaces.TryGetValue(new FontKey(key.FamilyName, key.Style, key.Weight), out var typeface))
+            if (typefaces.TryGetValue(key, out var typeface))
             {
                 return typeface;
             }
@@ -42,7 +39,7 @@ namespace Avalonia.Skia
                 {
                     if (weight - j >= 100)
                     {
-                        if (typefaces.TryGetValue(new FontKey(key.FamilyName, (FontStyle)i, (FontWeight)(weight - j)), out typeface))
+                        if (typefaces.TryGetValue(new Typeface(key.FontFamily, (FontStyle)i, (FontWeight)(weight - j)), out typeface))
                         {
                             return typeface;
                         }
@@ -53,7 +50,7 @@ namespace Avalonia.Skia
                         continue;
                     }
 
-                    if (typefaces.TryGetValue(new FontKey(key.FamilyName, (FontStyle)i, (FontWeight)(weight + j)), out typeface))
+                    if (typefaces.TryGetValue(new Typeface(key.FontFamily, (FontStyle)i, (FontWeight)(weight + j)), out typeface))
                     {
                         return typeface;
                     }

src/Skia/Avalonia.Skia/SKTypefaceCollectionCache.cs

@@ -56,7 +56,7 @@ namespace Avalonia.Skia
                     continue;
                 }
 
-                var key = new FontKey(fontFamily.Name, typeface.FontSlant.ToAvalonia(),
+                var key = new Typeface(fontFamily, typeface.FontSlant.ToAvalonia(),
                     (FontWeight)typeface.FontWeight);
 
                 typeFaceCollection.AddTypeface(key, typeface);

src/Skia/Avalonia.Skia/SkiaOptions.cs

@@ -16,6 +16,10 @@ namespace Avalonia
         /// <summary>
         /// The maximum number of bytes for video memory to store textures and resources.
         /// </summary>
-        public long? MaxGpuResourceSizeBytes { get; set; }
+        /// <remarks>
+        /// This is set by default to the recommended value for Avalonia.
+        /// Setting this to null will give you the default Skia value.
+        /// </remarks>
+        public long? MaxGpuResourceSizeBytes { get; set; } = 1024 * 600 * 4 * 12; // ~28mb 12x 1024 x 600 textures. 
     }
 }

src/Windows/Avalonia.Direct2D1/Media/FontManagerImpl.cs

@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using Avalonia.Media;
-using Avalonia.Media.Fonts;
 using Avalonia.Platform;
 using SharpDX.DirectWrite;
 using FontFamily = Avalonia.Media.FontFamily;
@@ -34,7 +33,7 @@ namespace Avalonia.Direct2D1.Media
 
         public bool TryMatchCharacter(int codepoint, FontStyle fontStyle,
             FontWeight fontWeight,
-            FontFamily fontFamily, CultureInfo culture, out FontKey fontKey)
+            FontFamily fontFamily, CultureInfo culture, out Typeface typeface)
         {
             var familyCount = Direct2D1FontCollectionCache.InstalledFontCollection.FontFamilyCount;
 
@@ -51,12 +50,12 @@ namespace Avalonia.Direct2D1.Media
 
                 var fontFamilyName = font.FontFamily.FamilyNames.GetString(0);
 
-                fontKey = new FontKey(fontFamilyName, fontStyle, fontWeight);
+                typeface = new Typeface(fontFamilyName, fontStyle, fontWeight);
 
                 return true;
             }
 
-            fontKey = default;
+            typeface = default;
 
             return false;
         }

src/Windows/Avalonia.Win32/Win32GlManager.cs

@@ -1,4 +1,5 @@
 using Avalonia.OpenGL;
+using Avalonia.OpenGL.Angle;
 
 namespace Avalonia.Win32
 {
@@ -15,7 +16,7 @@ namespace Avalonia.Win32
             {
                 if (!s_attemptedToInitialize)
                 {
-                    EglFeature = EglGlPlatformFeature.TryCreate();
+                    EglFeature = EglGlPlatformFeature.TryCreate(() => new AngleWin32EglDisplay());
                     s_attemptedToInitialize = true;
                 }
 

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -853,7 +853,7 @@ namespace Avalonia.Win32
 
         private void ShowWindow(WindowState state)
         {
-            ShowWindowCommand command;
+            ShowWindowCommand? command;
 
             var newWindowProperties = _windowProperties;
 
@@ -875,8 +875,8 @@ namespace Avalonia.Win32
 
                 case WindowState.FullScreen:
                     newWindowProperties.IsFullScreen = true;
-                    UpdateWindowProperties(newWindowProperties);
+                    command = IsWindowVisible(_hwnd) ? (ShowWindowCommand?)null : ShowWindowCommand.Restore;
-                    return;
+                    break;
 
                 default:
                     throw new ArgumentException("Invalid WindowState.");
@@ -884,7 +884,10 @@ namespace Avalonia.Win32
 
             UpdateWindowProperties(newWindowProperties);
 
-            UnmanagedMethods.ShowWindow(_hwnd, command);
+            if (command.HasValue)
+            {
+                UnmanagedMethods.ShowWindow(_hwnd, command.Value);
+            }
 
             if (state == WindowState.Maximized)
             {
@@ -1007,10 +1010,12 @@ namespace Avalonia.Win32
                 if (newProperties.IsResizable)
                 {
                     style |= WindowStyles.WS_SIZEFRAME;
+                    style |= WindowStyles.WS_MAXIMIZEBOX;
                 }
                 else
                 {
                     style &= ~WindowStyles.WS_SIZEFRAME;
+                    style &= ~WindowStyles.WS_MAXIMIZEBOX;
                 }
 
                 SetStyle(style);

tests/Avalonia.LeakTests/ControlTests.cs

@@ -552,6 +552,37 @@ namespace Avalonia.LeakTests
             }
         }
 
+        [Fact]
+        public void ItemsRepeater_Is_Freed()
+        {
+            using (Start())
+            {
+                Func<Window> run = () =>
+                {
+                    var window = new Window
+                    {
+                        Content = new ItemsRepeater(),
+                    };
+
+                    window.Show();
+
+                    window.LayoutManager.ExecuteInitialLayoutPass();
+                    Assert.IsType<ItemsRepeater>(window.Presenter.Child);
+
+                    window.Content = null;
+                    window.LayoutManager.ExecuteLayoutPass();
+                    Assert.Null(window.Presenter.Child);
+
+                    return window;
+                };
+
+                var result = run();
+
+                dotMemory.Check(memory =>
+                    Assert.Equal(0, memory.GetObjects(where => where.Type.Is<ItemsRepeater>()).ObjectsCount));
+            }
+        }
+
         private IDisposable Start()
         {
             return UnitTestApplication.Start(TestServices.StyledWindow.With(

tests/Avalonia.RenderTests/Media/FormattedTextImplTests.cs

@@ -51,7 +51,7 @@ namespace Avalonia.Direct2D1.RenderTests.Media
         {
             var r = AvaloniaLocator.Current.GetService<IPlatformRenderInterface>();
             return r.CreateFormattedText(text,
-                FontManager.Current.GetOrAddTypeface(fontFamily, fontStyle, fontWeight),
+                new Typeface(fontFamily, fontStyle, fontWeight),
                 fontSize,
                 textAlignment,
                 wrapping,

tests/Avalonia.Skia.UnitTests/Media/CustomFontManagerImpl.cs

@@ -39,7 +39,7 @@ namespace Avalonia.Skia.UnitTests.Media
         private readonly string[] _bcp47 = { CultureInfo.CurrentCulture.ThreeLetterISOLanguageName, CultureInfo.CurrentCulture.TwoLetterISOLanguageName };
 
         public bool TryMatchCharacter(int codepoint, FontStyle fontStyle, FontWeight fontWeight, FontFamily fontFamily,
-            CultureInfo culture, out FontKey fontKey)
+            CultureInfo culture, out Typeface typeface)
         {
             foreach (var customTypeface in _customTypefaces)
             {
@@ -48,7 +48,7 @@ namespace Avalonia.Skia.UnitTests.Media
                     continue;
                 }
 
-                fontKey = new FontKey(customTypeface.FontFamily.Name, fontStyle, fontWeight);
+                typeface = new Typeface(customTypeface.FontFamily.Name, fontStyle, fontWeight);
 
                 return true;
             }
@@ -56,7 +56,7 @@ namespace Avalonia.Skia.UnitTests.Media
             var fallback = SKFontManager.Default.MatchCharacter(fontFamily?.Name, (SKFontStyleWeight)fontWeight,
                 SKFontStyleWidth.Normal, (SKFontStyleSlant)fontStyle, _bcp47, codepoint);
 
-            fontKey = new FontKey(fallback?.FamilyName ?? _defaultFamilyName, fontStyle, fontWeight);
+            typeface = new Typeface(fallback?.FamilyName ?? _defaultFamilyName, fontStyle, fontWeight);
 
             return true;
         }
@@ -73,13 +73,13 @@ namespace Avalonia.Skia.UnitTests.Media
                         skTypeface = typefaceCollection.Get(typeface);
                         break;
                     }
-
                 case "Noto Sans":
                     {
                         var typefaceCollection = SKTypefaceCollectionCache.GetOrAddTypefaceCollection(_italicTypeface.FontFamily);
                         skTypeface = typefaceCollection.Get(typeface);
                         break;
                     }
+                case FontFamily.DefaultFontFamilyName:
                 case "Noto Mono":
                     {
                         var typefaceCollection = SKTypefaceCollectionCache.GetOrAddTypefaceCollection(_defaultTypeface.FontFamily);

tests/Avalonia.Skia.UnitTests/Media/TextFormatting/TextFormatterTests.cs

@@ -130,7 +130,7 @@ namespace Avalonia.Skia.UnitTests.Media.TextFormatting
         {
             using (Start())
             {
-                const string text = "1234الدولي";
+                const string text = "ABCDالدولي";
 
                 var defaultProperties = new GenericTextRunProperties(Typeface.Default);
 

tests/Avalonia.UnitTests/MockFontManagerImpl.cs

@@ -1,7 +1,6 @@
 using System.Collections.Generic;
 using System.Globalization;
 using Avalonia.Media;
-using Avalonia.Media.Fonts;
 using Avalonia.Platform;
 
 namespace Avalonia.UnitTests
@@ -26,9 +25,9 @@ namespace Avalonia.UnitTests
         }
 
         public bool TryMatchCharacter(int codepoint, FontStyle fontStyle, FontWeight fontWeight, FontFamily fontFamily,
-            CultureInfo culture, out FontKey fontKey)
+            CultureInfo culture, out Typeface fontKey)
         {
-            fontKey = default;
+            fontKey = new Typeface(_defaultFamilyName);
 
             return false;
         }

tests/Avalonia.Visuals.UnitTests/Media/FontManagerTests.cs

@@ -1,6 +1,5 @@
 using System;
 using Avalonia.Media;
-using Avalonia.Platform;
 using Avalonia.UnitTests;
 using Xunit;
 
@@ -15,9 +14,11 @@ namespace Avalonia.Visuals.UnitTests.Media
             {
                 var fontFamily = new FontFamily("MyFont");
 
-                var typeface = FontManager.Current.GetOrAddTypeface(fontFamily);
+                var typeface = new Typeface(fontFamily);
 
-                Assert.Same(typeface, FontManager.Current.GetOrAddTypeface(fontFamily));
+                var glyphTypeface = FontManager.Current.GetOrAddGlyphTypeface(typeface);
+
+                Assert.Same(glyphTypeface, FontManager.Current.GetOrAddGlyphTypeface(typeface));
             }
         }