feat(gradient): Added Radial Gradient for Android

src/Uno.UI/UI/Xaml/Controls/Border/BorderLayerRenderer.iOSmacOS.cs

@@ -115,12 +115,10 @@ private static IDisposable InnerCreateLayer(UIElement owner, CALayer parent, Lay
 
 				var outerPath = GetRoundedPath(cornerRadius, area);
 
-				var lgbBackground = background as LinearGradientBrush;
-				var scbBackground = background as SolidColorBrush;
 				var imgBackground = background as ImageBrush;
 				var insertionIndex = 0;
 
-				if (lgbBackground != null)
+				if (background is LinearGradientBrush lgbBackground)
 				{
 					var fillMask = new CAShapeLayer()
 					{
@@ -134,12 +132,12 @@ private static IDisposable InnerCreateLayer(UIElement owner, CALayer parent, Lay
 
 					CreateLinearGradientBrushLayers(area, adjustedArea, parent, sublayers, ref insertionIndex, lgbBackground, fillMask);
 				}
-				else if (scbBackground != null)
+				else if (background is SolidColorBrush scbBackground)
 				{
 					Brush.AssignAndObserveBrush(scbBackground, color => layer.FillColor = color)
 						.DisposeWith(disposables);
 				}
-				else if (imgBackground != null)
+				else if (background is ImageBrush imgBackground)
 				{
 					var uiImage = imgBackground.ImageSource?.ImageData;
 					if (uiImage != null && uiImage.Size != CGSize.Empty)
@@ -184,11 +182,7 @@ private static IDisposable InnerCreateLayer(UIElement owner, CALayer parent, Lay
 			}
 			else
 			{
-				var lgbBackground = background as LinearGradientBrush;
-				var scbBackground = background as SolidColorBrush;
-				var imgBackground = background as ImageBrush;
-
-				if (lgbBackground != null)
+				if (background is LinearGradientBrush lgbBackground)
 				{
 					var fullArea = new CGRect(
 						area.X + borderThickness.Left,
@@ -201,7 +195,7 @@ private static IDisposable InnerCreateLayer(UIElement owner, CALayer parent, Lay
 
 					CreateLinearGradientBrushLayers(fullArea, insideArea, parent, sublayers, ref insertionIndex, lgbBackground, fillMask: null);
 				}
-				else if (scbBackground != null)
+				else if (background is SolidColorBrush scbBackground)
 				{
 					Brush.AssignAndObserveBrush(scbBackground, c => parent.BackgroundColor = c)
 						.DisposeWith(disposables);
@@ -211,7 +205,7 @@ private static IDisposable InnerCreateLayer(UIElement owner, CALayer parent, Lay
 					Disposable.Create(() => parent.BackgroundColor = null)
 						.DisposeWith(disposables);
 				}
-				else if (imgBackground != null)
+				else if (background is ImageBrush imgBackground)
 				{
 					var uiImage = imgBackground.ImageSource?.ImageData;
 					if (uiImage != null && uiImage.Size != CGSize.Empty)

src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.Android.cs

@@ -207,13 +207,20 @@ private void UpdatePaint()
 				return;
 			}
 
+			var foreground = Foreground switch
+			{
+				SolidColorBrush scb => scb.ColorWithOpacity,
+				GradientBrush gb => gb.FallbackColor,
+				_ => Colors.Transparent
+			};
+
 			_paint = TextPaintPool.GetPaint(
 				FontWeight,
 				FontStyle,
 				FontFamily,
 				FontSize,
 				CharacterSpacing,
-				(Foreground as SolidColorBrush)?.Color ?? Colors.Transparent,
+				foreground,
 				BaseLineAlignment.Baseline,
 				TextDecorations
 			);

src/Uno.UI/UI/Xaml/Controls/TextBlock/TextBlock.cs

@@ -364,17 +364,21 @@ private void OnTextTrimmingChanged()
 #endif
 		Brush Foreground
 		{
-			get { return (Brush)this.GetValue(ForegroundProperty); }
+			get => (Brush)GetValue(ForegroundProperty);
 			set
 			{
 #if !__WASM__
-				if (!(Foreground is SolidColorBrush))
+				if (Foreground is SolidColorBrush || Foreground is GradientBrush)
 				{
-					throw new NotSupportedException();
+					SetValue(ForegroundProperty, value);
 				}
-#endif
-
+				else
+				{
+					throw new NotSupportedException("Only SolidColorBrush or GradientBrush's FallbackColor are supported.");
+				}
+#else
 				this.SetValue(ForegroundProperty, value);
+#endif
 			}
 		}
 

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

@@ -21,7 +21,7 @@ public Color FallbackColor
 		public static readonly DependencyProperty GradientStopsProperty = DependencyProperty.Register(
 			"GradientStops",
 			typeof(GradientStopCollection),
-			typeof(LinearGradientBrush),
+			typeof(GradientBrush),
 			new PropertyMetadata(null)
 		);
 		public GradientStopCollection GradientStops

src/Uno.UI/UI/Xaml/Media/LinearGradientBrush.Android.cs

@@ -4,6 +4,7 @@
 using Android.Graphics;
 using System.Linq;
 using System.Drawing;
+using Uno.Extensions;
 
 namespace Windows.UI.Xaml.Media
 {
@@ -17,24 +18,34 @@ protected override Paint GetPaintInner(Windows.Foundation.Rect destinationRect)
 			// Android LinearGradient requires two ore more stop points.
 			if (GradientStops.Count >= 2)
 			{
-				var colors = GradientStops.Select(s => ((Android.Graphics.Color)s.Color).ToArgb()).ToArray();
-				var locations = GradientStops.Select(s => (float)s.Offset).ToArray();
+				var colors = GradientStops.SelectToArray(s => ((Android.Graphics.Color)s.Color).ToArgb());
+				var locations = GradientStops.SelectToArray(s => (float)s.Offset);
 
 				var width = destinationRect.Width;
 				var height = destinationRect.Height;
 
-				var transform = RelativeTransform?.ToNative(size: new Windows.Foundation.Size(width, height), isBrush: true);
+				var transform =
+					RelativeTransform?.ToNative(size: new Windows.Foundation.Size(width, height), isBrush: true);
 
 				//Matrix .MapPoints takes an array of floats
-				var pts = new[] { StartPoint, EndPoint }
-					.Select(p => new float[] { (float)(p.X * width), (float)(p.Y * height) })
-					.SelectMany(p => p)
-					.ToArray();
+				var pts = MappingMode == BrushMappingMode.RelativeToBoundingBox
+					? new []
+						{
+							(float)(StartPoint.X * width),
+							(float)(StartPoint.Y * height),
+							(float)(EndPoint.X * width),
+							(float)(EndPoint.Y * height)
+						}
+					: new []
+						{
+							(float)StartPoint.X,
+							(float)StartPoint.Y,
+							(float)EndPoint.X,
+							(float)EndPoint.Y
+						};
 
 				transform?.MapPoints(pts);
-
-
-				var shader = new LinearGradient(pts[0], pts[1], pts[2], pts[3], colors, locations, Shader.TileMode.Mirror);
+				var shader = new LinearGradient(pts[0], pts[1], pts[2], pts[3], colors, locations, Shader.TileMode.Clamp);
 
 				paint.SetShader(shader);
 			}

src/Uno.UI/UI/Xaml/Media/RadialGradientBrush.Android.cs

@@ -0,0 +1,61 @@
+using System.Linq;
+using Android.Graphics;
+using Uno.Extensions;
+using Uno.UI;
+using Point = Windows.Foundation.Point;
+
+namespace Windows.UI.Xaml.Media
+{
+	partial class RadialGradientBrush
+	{
+		protected override Paint GetPaintInner(Windows.Foundation.Rect destinationRect)
+		{
+			var paint = new Paint();
+
+			var center = Center;
+			var radiusX = RadiusX;
+			var radiusY = RadiusY;
+
+			float radius;
+
+			if (MappingMode == BrushMappingMode.RelativeToBoundingBox)
+			{
+				var size = destinationRect.Size;
+
+				center = new Point(center.X * size.Width, Center.Y * size.Height);
+				radius = (float)(radiusX * size.Width + radiusY * size.Height) / 4.0f; // We take the avg
+			}
+			else
+			{
+				center = center.LogicalToPhysicalPixels();
+				radius = ViewHelper.LogicalToPhysicalPixels((radiusX + radiusY) / 2.0d); // We take the avg
+			}
+
+
+			// Android RadialGradient requires two ore more stop points.
+			if (GradientStops.Count >= 2)
+			{
+				var colors = GradientStops.SelectToArray(s => ((Android.Graphics.Color)s.Color).ToArgb());
+				var locations = GradientStops.SelectToArray(s => (float)s.Offset);
+
+				var width = destinationRect.Width;
+				var height = destinationRect.Height;
+
+				var transform = RelativeTransform?.ToNative(size: new Windows.Foundation.Size(width, height), isBrush: true);
+
+				var shader = new RadialGradient(
+					(float)center.X,
+					(float)center.Y,
+					radius,
+					colors,
+					locations,
+					Shader.TileMode.Clamp);
+
+				paint.SetShader(shader);
+			}
+
+			return paint;
+		}
+
+	}
+}

src/Uno.UI/UI/Xaml/Media/RadialGradientBrush.wasm.cs

@@ -12,12 +12,9 @@ partial class RadialGradientBrush
 		internal override string ToCssString(Size size)
 		{
 			var center = Center;
-
 			var radiusX = RadiusX;
 			var radiusY = RadiusY;
 
-			var ratio = size.AspectRatio();
-
 			if (MappingMode != BrushMappingMode.RelativeToBoundingBox)
 			{
 				center = new Point(center.X * size.Width, Center.Y * size.Height);