Fixed memory management issues in OpacityMaskView

AIDevGallery/Controls/OpacityMask.xaml.cs

@@ -31,8 +31,13 @@ public partial class OpacityMaskView : ContentControl
     private const string RootGridTemplateName = "PART_RootGrid";
 
     private readonly Compositor _compositor = CompositionTarget.GetCompositorForCurrentThread();
+
+    // Composition resources we create and need to tear down explicitly to avoid retaining composition references longer than necessary
     private CompositionBrush? _mask;
     private CompositionMaskBrush? _maskBrush;
+    private CompositionSurfaceBrush? _sourceBrush;
+    private Grid? _rootGrid;
+    private SpriteVisual? _redirectVisual;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="OpacityMaskView"/> class.
@@ -41,6 +46,9 @@ public partial class OpacityMaskView : ContentControl
     public OpacityMaskView()
     {
         DefaultStyleKey = typeof(OpacityMaskView);
+
+        // Ensure composition resources are cleaned up when control unloads
+        Unloaded += OpacityMaskView_Unloaded;
     }
 
     /// <summary>
@@ -57,22 +65,35 @@ protected override void OnApplyTemplate()
     {
         base.OnApplyTemplate();
 
+        // Clean up any prior composition resources (e.g., when the template is re-applied)
+        CleanupComposition();
+
         Grid rootGrid = (Grid)GetTemplateChild(RootGridTemplateName);
         ContentPresenter contentPresenter = (ContentPresenter)GetTemplateChild(ContentPresenterTemplateName);
         Border maskContainer = (Border)GetTemplateChild(MaskContainerTemplateName);
 
+        _rootGrid = rootGrid;
+
+        // Create mask brush and its sources
         _maskBrush = _compositor.CreateMaskBrush();
-        _maskBrush.Source = GetVisualBrush(contentPresenter);
+
+        // Source is the content we want to render through the mask
+        _sourceBrush = GetVisualBrush(contentPresenter);
+        _maskBrush.Source = _sourceBrush;
+
+        // Mask is the opacity mask visual brush
         _mask = GetVisualBrush(maskContainer);
         _maskBrush.Mask = OpacityMask is null ? null : _mask;
 
+        // Create a sprite visual that draws with the mask brush, and redirect the control visual to it
         SpriteVisual redirectVisual = _compositor.CreateSpriteVisual();
         redirectVisual.RelativeSizeAdjustment = Vector2.One;
         redirectVisual.Brush = _maskBrush;
         ElementCompositionPreview.SetElementChildVisual(rootGrid, redirectVisual);
+        _redirectVisual = redirectVisual;
     }
 
-    private static CompositionBrush GetVisualBrush(UIElement element)
+    private static CompositionSurfaceBrush GetVisualBrush(UIElement element)
     {
         Visual visual = ElementCompositionPreview.GetElementVisual(element);
 
@@ -100,6 +121,51 @@ private static void OnOpacityMaskChanged(DependencyObject d, DependencyPropertyC
         }
 
         UIElement? opacityMask = (UIElement?)e.NewValue;
+
+        // Switch to the mask brush if an opacity mask is set; otherwise remove the mask
         maskBrush.Mask = opacityMask is null ? null : self._mask;
     }
+
+    // On control unload, ensure we tear down composition resources and clear the child visual
+    private void OpacityMaskView_Unloaded(object sender, RoutedEventArgs e) => CleanupComposition();
+
+    /// <summary>
+    /// Clears the ElementCompositionPreview child visual and disposes all composition resources created by this control.
+    /// This prevents composition resource retention across template reapplications or when the control is unloaded.
+    /// </summary>
+    private void CleanupComposition()
+    {
+        // Detach the child visual from the root grid if present
+        if (_rootGrid != null)
+        {
+            ElementCompositionPreview.SetElementChildVisual(_rootGrid, null);
+        }
+
+        // Dispose the redirect visual
+        if (_redirectVisual != null)
+        {
+            _redirectVisual.Brush = null;
+            _redirectVisual.Dispose();
+            _redirectVisual = null;
+        }
+
+        // Dispose mask brush and its sources
+        if (_maskBrush != null)
+        {
+            _maskBrush.Source = null;
+            _maskBrush.Mask = null;
+            _maskBrush.Dispose();
+            _maskBrush = null;
+        }
+
+        // Dispose the source content brush explicitly
+        _sourceBrush?.Dispose();
+        _sourceBrush = null;
+
+        // Dispose the mask brush instance if we created one
+        _mask?.Dispose();
+        _mask = null;
+
+        _rootGrid = null;
+    }
 }