feat(xaml): Implement XamlCompositionBrushBase

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Media/XamlCompositionBrushBase/XamlCompositionBrushBaseTests.xaml

@@ -0,0 +1,15 @@
+<UserControl
+    x:Class="UITests.Windows_UI_Xaml_Media.XamlCompositionBrushBase.XamlCompositionBrushBaseTests"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:UITests.Windows_UI_Xaml_Media.XamlCompositionBrushBase"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    d:DesignHeight="300"
+    d:DesignWidth="400" Loaded="UserControl_Loaded">
+
+	<Grid>
+		<Grid x:Name="testGrid" Width="200" Height="200" HorizontalAlignment="Left" VerticalAlignment="Top"/>
+	</Grid>
+</UserControl>

src/SamplesApp/UITests.Shared/Windows_UI_Xaml_Media/XamlCompositionBrushBase/XamlCompositionBrushBaseTests.xaml.cs

@@ -0,0 +1,38 @@
+using Windows.UI;
+using Windows.UI.Xaml;
+using Windows.UI.Xaml.Controls;
+using Uno.UI.Samples.Controls;
+
+// The User Control item template is documented at https://go.microsoft.com/fwlink/?LinkId=234236
+
+namespace UITests.Windows_UI_Xaml_Media.XamlCompositionBrushBase
+{
+	[Sample("Windows.UI.Xaml.Media", Name = "XamlCompositionBrushBase", Description = "Provides a base class used to create XAML brushes that paint an area with a CompositionBrush.", IsManualTest = true)]
+	public sealed partial class XamlCompositionBrushBaseTests : UserControl
+	{
+		public XamlCompositionBrushBaseTests()
+		{
+			this.InitializeComponent();
+		}
+
+		private void UserControl_Loaded(object sender, RoutedEventArgs e)
+		{
+			testGrid.Background = new TestBrush();
+		}
+	}
+
+	class TestBrush : Windows.UI.Xaml.Media.XamlCompositionBrushBase
+	{
+		protected override void OnConnected()
+		{
+			var compositor = Window.Current.Compositor;
+			var brush = compositor.CreateLinearGradientBrush();
+			brush.ColorStops.Add(compositor.CreateColorGradientStop(0.0f, Colors.Black));
+			brush.ColorStops.Add(compositor.CreateColorGradientStop(1.0f, Colors.White));
+			brush.StartPoint = new();
+			brush.EndPoint = new(200, 200);
+
+			CompositionBrush = brush;
+		}
+	}
+}

src/Uno.UI/Generated/3.0.0.0/Windows.UI.Xaml.Media/XamlCompositionBrushBase.cs

@@ -9,20 +9,7 @@ namespace Windows.UI.Xaml.Media
 	public partial class XamlCompositionBrushBase : global::Windows.UI.Xaml.Media.Brush
 	{
 		// Skipping already declared property FallbackColor
-#if __ANDROID__ || __IOS__ || IS_UNIT_TESTS || __WASM__ || __SKIA__ || __NETSTD_REFERENCE__ || __MACOS__
-		[global::Uno.NotImplemented("__ANDROID__", "__IOS__", "IS_UNIT_TESTS", "__WASM__", "__SKIA__", "__NETSTD_REFERENCE__", "__MACOS__")]
-		public global::Windows.UI.Composition.CompositionBrush CompositionBrush
-		{
-			get
-			{
-				throw new global::System.NotImplementedException("The member CompositionBrush XamlCompositionBrushBase.CompositionBrush is not implemented. For more information, visit https://aka.platform.uno/notimplemented#m=CompositionBrush%20XamlCompositionBrushBase.CompositionBrush");
-			}
-			set
-			{
-				global::Windows.Foundation.Metadata.ApiInformation.TryRaiseNotImplemented("Windows.UI.Xaml.Media.XamlCompositionBrushBase", "CompositionBrush XamlCompositionBrushBase.CompositionBrush");
-			}
-		}
-#endif
+		// Skipping already declared property CompositionBrush
 		// Skipping already declared property FallbackColorProperty
 		// Skipping already declared method Windows.UI.Xaml.Media.XamlCompositionBrushBase.XamlCompositionBrushBase()
 		// Forced skipping of method Windows.UI.Xaml.Media.XamlCompositionBrushBase.XamlCompositionBrushBase()

src/Uno.UI/UI/Xaml/Media/Brush.skia.cs

@@ -39,9 +39,9 @@ internal static IDisposable AssignAndObserveBrush(Brush brush, Compositor compos
 			{
 				return AssignAndObserveRadialGradientBrush(radialGradientBrush, compositor, brushSetter);
 			}
-			else if (brush is XamlCompositionBrushBase unimplementedCompositionBrush)
+			else if (brush is XamlCompositionBrushBase compositionBrush)
 			{
-				return AssignAndObserveXamlCompositionBrush(unimplementedCompositionBrush, compositor, brushSetter);
+				return AssignAndObserveXamlCompositionBrush(compositionBrush, compositor, brushSetter);
 			}
 			else
 			{
@@ -197,25 +197,28 @@ private static IDisposable AssignAndObserveRadialGradientBrush(RadialGradientBru
 			return disposables;
 		}
 
-		/// <summary>
-		/// Apply fallback colour for unimplemented <see cref="XamlCompositionBrushBase"/> types. For implemented types a more specific method
-		/// should be supplied.
-		/// </summary>
 		private static IDisposable AssignAndObserveXamlCompositionBrush(XamlCompositionBrushBase brush, Compositor compositor, BrushSetterHandler brushSetter)
 		{
 			var disposables = new CompositeDisposable();
 
-			var compositionBrush = compositor.CreateColorBrush(brush.FallbackColorWithOpacity);
+			brush.OnConnectedInternal();
+			var compositionBrush = brush.CompositionBrush ?? compositor.CreateColorBrush(brush.FallbackColorWithOpacity);
 
 			brush.RegisterDisposablePropertyChangedCallback(
 				XamlCompositionBrushBase.FallbackColorProperty,
-				(s, colorArg) => compositionBrush.Color = brush.FallbackColorWithOpacity
+				(s, colorArg) => { if (compositionBrush is CompositionColorBrush colorBrush) colorBrush.Color = brush.FallbackColorWithOpacity; }
 			)
 			.DisposeWith(disposables);
 
 			brush.RegisterDisposablePropertyChangedCallback(
 				XamlCompositionBrushBase.OpacityProperty,
-				(s, colorArg) => compositionBrush.Color = brush.FallbackColorWithOpacity
+				(s, colorArg) => { if (compositionBrush is CompositionColorBrush colorBrush) colorBrush.Color = brush.FallbackColorWithOpacity; }
+			)
+			.DisposeWith(disposables);
+
+			brush.RegisterDisposablePropertyChangedCallback(
+				XamlCompositionBrushBase.CompositionBrushProperty,
+				(s, brushArg) => { if (brush.CompositionBrush is CompositionBrush compBrush) brushSetter(compBrush); }
 			)
 			.DisposeWith(disposables);
 

src/Uno.UI/UI/Xaml/Media/XamlCompositionBrushBase.cs

@@ -1,3 +1,4 @@
+using Windows.UI.Composition;
 using Color = Windows.UI.Color;
 
 namespace Windows.UI.Xaml.Media;
@@ -31,11 +32,35 @@ public Color FallbackColor
 	/// </summary>
 	internal Color FallbackColorWithOpacity => FallbackColor.WithOpacity(Opacity);
 
+	public CompositionBrush CompositionBrush
+	{
+		get
+		{
+			return (CompositionBrush)this.GetValue(CompositionBrushProperty);
+		}
+		set
+		{
+			this.SetValue(CompositionBrushProperty, value);
+		}
+	}
+
+	/// <summary>
+	/// Internal DependencyProperty used to track the CompositionBrush property.
+	/// </summary>
+	internal static DependencyProperty CompositionBrushProperty { get; } =
+		DependencyProperty.Register(
+			nameof(CompositionBrush), typeof(CompositionBrush),
+			typeof(XamlCompositionBrushBase),
+			new FrameworkPropertyMetadata(default(CompositionBrush)));
+
 	protected virtual void OnConnected()
 	{
 	}
 
 	protected virtual void OnDisconnected()
 	{
 	}
+
+	internal void OnConnectedInternal() => OnConnected();
+	internal void OnDisconnectedInternal() => OnDisconnected();
 }