test: Added Test for ShadowContainer re-layout issue (#797)

Co-authored-by: Steve Bilogan <steve.bilogan@gmail.com>
Co-authored-by: Rafael Rosa <rafaelmendesrosa@gmail.com>
Co-authored-by: Rafael Rosa <116665025+rafael-rosa-knowcode@users.noreply.github.com>

src/Uno.Toolkit.RuntimeTests/Tests/ShadowContainerTests.cs

@@ -28,6 +28,7 @@
 using Microsoft.UI.Xaml;
 using Microsoft.UI.Xaml.Media.Imaging;
 using Windows.UI.ViewManagement;
+using FluentAssertions;
 
 namespace Uno.Toolkit.RuntimeTests.Tests
 {
@@ -172,6 +173,68 @@ public async Task Outer_Shadows(int offsetX, int offsetY, bool inner)
 			}
 		}
 #endif
+
+		[TestMethod]
+		public async Task ShadowContainer_ReLayoutsAfterChangeInSize()
+		{
+			ShadowContainer.ClearCache();
+
+			var internalBorder = new Border { Height = 200, Width = 200, Background = new SolidColorBrush(Colors.Green) };
+			bool createdNewCanvas = false;
+
+			var shadowContainer = new ShadowContainer
+			{
+				Content = internalBorder,
+				Shadows = new ShadowCollection
+				{
+					new UI.Shadow
+					{
+						Color = Colors.Blue,
+						OffsetX = 10,
+						OffsetY = 10,
+						IsInner = false,
+						Opacity = 1,
+
+					}
+				}
+			};
+
+			UnitTestsUIContentHelper.Content = shadowContainer;
+
+			shadowContainer.SurfacePaintCompleted += SurfacePaintCompleted;
+
+			shadowContainer.Shadows.Add(new UI.Shadow
+			{
+				Color = Colors.Red,
+				OffsetX = 10,
+				OffsetY = 10,
+				IsInner = false,
+				Opacity = 1,
+			});
+
+			await UnitTestsUIContentHelper.WaitForIdle();
+			await UnitTestsUIContentHelper.WaitForLoaded(shadowContainer);
+			createdNewCanvas.Should().BeTrue();
+			createdNewCanvas = false;
+
+			// Changing the height of the children content of the shadow. 
+			internalBorder.Height = 400;
+
+			await UnitTestsUIContentHelper.WaitForIdle();
+
+			createdNewCanvas.Should().BeTrue();
+
+			shadowContainer.SurfacePaintCompleted -= SurfacePaintCompleted; ;
+
+			void SurfacePaintCompleted(object? sender, ShadowContainer.SurfacePaintCompletedEventArgs args)
+			{
+				// OnSurfacePainted can be called several times, we must make sure that the canvas is regenerated at least once.
+				if (createdNewCanvas == false)
+				{
+					createdNewCanvas = args.CreatedNewCanvas;
+				}
+			}
+		}
 	}
 }
 #endif

src/Uno.Toolkit.Skia.WinUI/AssemblyInfo.cs

@@ -0,0 +1,3 @@
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Uno.Toolkit.RuntimeTests")]

src/Uno.Toolkit.Skia.WinUI/Controls/Shadows/ShadowContainer.Paint.cs

@@ -24,6 +24,18 @@ public partial class ShadowContainer
 	private ShadowPaintState? _lastPaintState;
 	private bool _isShadowDirty;
 
+	internal event EventHandler<SurfacePaintCompletedEventArgs>? SurfacePaintCompleted;
+
+	internal static void ClearCache()
+	{
+		Cache.Clear();
+	}
+
+	private void OnSurfacePaintCompleted(bool createdNewCanvas)
+	{
+		SurfacePaintCompleted?.Invoke(this, new SurfacePaintCompletedEventArgs(createdNewCanvas));
+	}
+
 	private bool NeedsPaint(ShadowPaintState state, out bool pixelRatioChanged)
 	{
 		var needsPaint = state != _lastPaintState;
@@ -84,6 +96,7 @@ private void OnSurfacePainted(object? sender, SKPaintSurfaceEventArgs e)
 			else
 			{
 				canvas.DrawImage(snapshot, SKPoint.Empty);
+				OnSurfacePaintCompleted(createdNewCanvas: false);
 				return;
 			}
 		}
@@ -120,6 +133,8 @@ private void OnSurfacePainted(object? sender, SKPaintSurfaceEventArgs e)
 		{
 			Cache.AddOrUpdate(key, e.Surface.Snapshot());
 		}
+
+		OnSurfacePaintCompleted(createdNewCanvas: true);
 	}
 
 	private static Color? GetBackgroundColor(Brush? background)
@@ -344,4 +359,14 @@ x is { } y &&
 			PixelRatio == y.PixelRatio &&
 			Shadows.SequenceEqual(y.Shadows);
 	}
+
+	public class SurfacePaintCompletedEventArgs : EventArgs
+	{
+		public bool CreatedNewCanvas { get; }
+
+		public SurfacePaintCompletedEventArgs(bool createdNewCanvas)
+		{
+			CreatedNewCanvas = createdNewCanvas;
+		}
+	}
 }

src/Uno.Toolkit.Skia.WinUI/Controls/Shadows/ShadowsCache.cs

@@ -71,6 +71,16 @@ public bool Remove(string key)
 		return _shadowsCache.TryRemove(key, out var _);
 	}
 
+	internal void Clear()
+	{
+		if (_logger.IsEnabled(LogLevel.Trace))
+		{
+			_logger.Trace("Cleared [ShadowsCache]");
+		}
+
+		_shadowsCache.Clear();
+	}
+
 	private class CacheBucket
 	{
 		public CacheBucket(SKImage bitmap)