[Android] - Fix Shadow Rendering For Transparent Fill, Stroke (Lines), and Text on Shapes

src/Controls/tests/TestCases.HostApp/Issues/Issue29394.cs

@@ -0,0 +1,68 @@
+namespace Maui.Controls.Sample.Issues;
+
+[Issue(IssueTracker.Github, 29394, "On Android Shadows should not be rendered over fully transparent areas of drawn shapes", PlatformAffected.Android)]
+public class Issue29394 : TestContentPage
+{
+    protected override void Init()
+    {
+        var verticalStackLayout = new VerticalStackLayout()
+        {
+            Padding = new Thickness(30, 0),
+            Spacing = 25,
+            VerticalOptions = LayoutOptions.Center
+        };
+
+        var graphicsView = new GraphicsView()
+        {
+            HeightRequest = 500,
+            WidthRequest = 400,
+            Drawable = new Issue29394_Drawable()
+        };
+        var label = new Label()
+        {
+            Text = "This is a test for Shadows should not be rendered over fully transparent areas of drawn shapes.",
+            AutomationId = "label",
+            HorizontalOptions = LayoutOptions.Center,
+            VerticalOptions = LayoutOptions.Center
+        };
+
+        verticalStackLayout.Children.Add(graphicsView);
+        verticalStackLayout.Children.Add(label);
+        Content = verticalStackLayout;
+    }
+}
+
+public class Issue29394_Drawable : IDrawable
+{
+    Rect fillRect = new Rect(0, 0, 300, 300);
+
+    public void Draw(ICanvas canvas, RectF dirtyRect)
+    {
+        canvas.SaveState();
+
+        float centerX = (dirtyRect.Width - (float)fillRect.Width) / 2;
+        float centerY = (dirtyRect.Height - (float)fillRect.Height) / 2;
+        var outerRect = new RectF(centerX, centerY, (float)fillRect.Width, (float)fillRect.Height);
+
+        canvas.SetFillPaint(Colors.Transparent.AsPaint(), outerRect);
+        canvas.SetShadow(new SizeF(0, 15), 4, Color.FromArgb("#59000000"));
+        canvas.FillEllipse(outerRect.X, outerRect.Y, outerRect.Width, outerRect.Height);
+
+        float arcSize = 250f;
+        float arcX = outerRect.X + (outerRect.Width - arcSize) / 2;
+        float arcY = outerRect.Y + (outerRect.Height - arcSize) / 2;
+
+        canvas.FillColor = Colors.Blue;
+        canvas.FillCircle(arcX + arcSize / 2, arcY + arcSize / 2, 15);
+        canvas.DrawArc(arcX, arcY, arcSize, arcSize, 45, 90, true, false);
+
+        canvas.StrokeColor = Colors.Transparent;
+        canvas.StrokeSize = 2;
+        canvas.DrawLine(0, 25, dirtyRect.Width, 25);
+
+        canvas.FontColor = Colors.Transparent;
+        canvas.DrawString("Shadow should not be Rendered", dirtyRect.Width / 2, 10, HorizontalAlignment.Center);
+
+        canvas.RestoreState();
+    }
+}

src/Controls/tests/TestCases.Shared.Tests/Tests/Issues/Issue29394.cs

@@ -0,0 +1,19 @@
+using NUnit.Framework;
+using UITest.Appium;
+using UITest.Core;
+
+namespace Microsoft.Maui.TestCases.Tests.Issues;
+public class Issue29394 : _IssuesUITest
+{
+	public Issue29394(TestDevice device) : base(device) { }
+
+	public override string Issue => "On Android Shadows should not be rendered over fully transparent areas of drawn shapes";
+
+	[Test]
+	[Category(UITestCategories.GraphicsView)]
+	public void TransparentShapeShouldNotDisplayShadow()
+	{
+		App.WaitForElement("label");
+		VerifyScreenshot();
+	}
+}

src/Graphics/src/Graphics/Platforms/Android/PlatformCanvasState.cs

@@ -61,22 +61,40 @@ public PlatformCanvasState(PlatformCanvasState prototype) : base(prototype)
 		public Color StrokeColor
 		{
 			get => _strokeColor;
-			set => _strokeColor = value;
+			set
+			{
+				if (_strokeColor != value)
+				{
+					_strokeColor = value;
+					UpdateShadowState();
+				}
+			}
 		}
 
 		public Color FillColor
 		{
 			get => _fillColor;
-			set => _fillColor = value;
+			set
+			{
+				if (_fillColor != value)
+				{
+					_fillColor = value;
+					UpdateShadowState();
+				}
+			}
 		}
 
 		public Color FontColor
 		{
 			get => _fontColor;
 			set
 			{
-				_fontColor = value;
-				FontPaint.Color = value != null ? _fontColor.AsColor() : global::Android.Graphics.Color.Black;
+				if (_fontColor != value)
+				{
+					_fontColor = value;
+					FontPaint.Color = value != null ? _fontColor.AsColor() : global::Android.Graphics.Color.Black;
+					UpdateShadowState();
+				}
 			}
 		}
 
@@ -352,15 +370,15 @@ public override void Dispose()
 
 		public void SetShadow(float blur, float sx, float sy, global::Android.Graphics.Color color)
 		{
-			FillPaint.SetShadowLayer(blur, sx, sy, color);
-			StrokePaint.SetShadowLayer(blur, sx, sy, color);
-			FontPaint.SetShadowLayer(blur, sx, sy, color);
-
 			_shadowed = true;
 			_shadowBlur = blur;
 			_shadowX = sx;
 			_shadowY = sy;
 			_shadowColor = color;
+
+			ApplyShadow(FillPaint, FillColor.Alpha);
+			ApplyShadow(StrokePaint, StrokeColor.Alpha);
+			ApplyShadow(FontPaint, FontColor.Alpha);
 		}
 
 		public global::Android.Graphics.Paint GetShadowPaint(float sx, float sy)
@@ -420,5 +438,25 @@ public void Reset(global::Android.Graphics.Paint aFontPaint, global::Android.Gra
 			_scaleX = 1;
 			_scaleY = 1;
 		}
+
+		void ApplyShadow(global::Android.Graphics.Paint paint, float alpha)
+		{
+			if (alpha > 0)
+			{
+				paint.SetShadowLayer(_shadowBlur, _shadowX, _shadowY, _shadowColor);
+			}
+			else
+			{
+				paint.ClearShadowLayer();
+			}
+		}
+
+		void UpdateShadowState()
+		{
+			if (_shadowed)
+			{
+				SetShadow(_shadowBlur, _shadowX, _shadowY, _shadowColor);
+			}
+		}
 	}
 }