Fixed compositor nullreference in WinUI 3

Author: Arlodotexe

components/Media/src/Brushes/BackdropGammaTransferBrush.cs

@@ -345,7 +345,14 @@ protected override void OnConnected()
                 return;
             }
 
-            var backdrop = Window.Current.Compositor.CreateBackdropBrush();
+            
+#if WINUI2
+            var compositor = Window.Current.Compositor;
+#elif WINUI3
+            var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+
+            var backdrop = compositor.CreateBackdropBrush();
 
             // Use a Win2D blur affect applied to a CompositionBackdropBrush.
             var graphicsEffect = new GammaTransferEffect
@@ -370,7 +377,7 @@ protected override void OnConnected()
                 Source = new CompositionEffectSourceParameter("backdrop")
             };
 
-            var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect, new[]
+            var effectFactory = compositor.CreateEffectFactory(graphicsEffect, new[]
             {
                 "GammaTransfer.AlphaAmplitude",
                 "GammaTransfer.AlphaExponent",

components/Media/src/Brushes/CanvasBrushBase.cs

@@ -66,7 +66,13 @@ protected override void OnConnected()
             _graphics.RenderingDeviceReplaced -= CanvasDevice_RenderingDeviceReplaced;
         }
 
-        _graphics = CanvasComposition.CreateCompositionGraphicsDevice(Window.Current.Compositor, _device);
+#if WINUI2
+        var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+
+        _graphics = CanvasComposition.CreateCompositionGraphicsDevice(compositor, _device);
         _graphics.RenderingDeviceReplaced += CanvasDevice_RenderingDeviceReplaced;
 
         // Delay creating composition resources until they're required.
@@ -95,7 +101,7 @@ protected override void OnConnected()
                 }
             }
 
-            _surfaceBrush = Window.Current.Compositor.CreateSurfaceBrush(surface);
+            _surfaceBrush = compositor.CreateSurfaceBrush(surface);
             _surfaceBrush.Stretch = CompositionStretch.Fill;
 
             CompositionBrush = _surfaceBrush;

components/Media/src/Brushes/ImageBlendBrush.cs

@@ -126,15 +126,22 @@ private static void OnModeChanged(DependencyObject d, DependencyPropertyChangedE
     /// <inheritdoc/>
     protected override void OnConnected()
     {
+#if WINUI2
+        var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+
         // Delay creating composition resources until they're required.
         if (CompositionBrush == null && Source != null && Source is BitmapImage bitmap)
         {
             // Use LoadedImageSurface API to get ICompositionSurface from image uri provided
             // If UriSource is invalid, StartLoadFromUri will return a blank texture.
             _surface = LoadedImageSurface.StartLoadFromUri(bitmap.UriSource);
 
+
             // Load Surface onto SurfaceBrush
-            _surfaceBrush = Window.Current.Compositor.CreateSurfaceBrush(_surface);
+            _surfaceBrush = compositor.CreateSurfaceBrush(_surface);
             _surfaceBrush.Stretch = CompositionStretchFromStretch(Stretch);
 
 #if WINUI2
@@ -150,7 +157,7 @@ protected override void OnConnected()
                 return;
             }
 
-            var backdrop = Window.Current.Compositor.CreateBackdropBrush();
+            var backdrop = compositor.CreateBackdropBrush();
 
             // Use a Win2D invert affect applied to a CompositionBackdropBrush.
             var graphicsEffect = new CanvasBlendEffect
@@ -161,7 +168,7 @@ protected override void OnConnected()
                 Foreground = new CompositionEffectSourceParameter("image")
             };
 
-            var effectFactory = Window.Current.Compositor.CreateEffectFactory(graphicsEffect);
+            var effectFactory = compositor.CreateEffectFactory(graphicsEffect);
             var effectBrush = effectFactory.CreateBrush();
 
             effectBrush.SetSourceParameter("backdrop", backdrop);

components/Media/src/Helpers/SurfaceLoader.Instance.cs

@@ -43,7 +43,12 @@ public sealed partial class SurfaceLoader : IDisposable
     /// <returns>A <see cref="SurfaceLoader"/> instance to use in the current window</returns>
     public static SurfaceLoader GetInstance()
     {
-        return GetInstance(Window.Current.Compositor);
+#if WINUI2
+        var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+        return GetInstance(compositor);
     }
 
     /// <summary>

components/Media/src/Helpers/SurfaceLoader.cs

@@ -44,7 +44,11 @@ public sealed partial class SurfaceLoader
     /// <returns>A <see cref="Task{T}"/> that returns the loaded <see cref="CompositionBrush"/> instance</returns>
     public static async Task<CompositionBrush?> LoadImageAsync(Uri uri, DpiMode dpiMode, CacheMode cacheMode = CacheMode.Default)
     {
+#if WINUI2
         var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
 
         // Lock and check the cache first
         using (await Win2DMutex.LockAsync())

components/Media/src/Pipelines/PipelineBuilder.Initialization.cs

@@ -46,7 +46,12 @@ public static PipelineBuilder FromBackdrop()
     {
         ValueTask<CompositionBrush> Factory()
         {
-            var brush = BackdropBrushCache.GetValue(Window.Current.Compositor, c => c.CreateBackdropBrush());
+#if WINUI2
+            var compositor = Window.Current.Compositor;
+#elif WINUI3
+            var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+            var brush = BackdropBrushCache.GetValue(compositor, c => c.CreateBackdropBrush());
 
             return new ValueTask<CompositionBrush>(brush);
         }

components/Media/src/Pipelines/PipelineBuilder.cs

@@ -160,6 +160,12 @@ private PipelineBuilder(
     [Pure]
     public async Task<CompositionBrush> BuildAsync()
     {
+#if WINUI2
+        var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+
         var effect = await this.sourceProducer() as IGraphicsEffect;
 
         // Validate the pipeline
@@ -170,8 +176,8 @@ public async Task<CompositionBrush> BuildAsync()
 
         // Build the effects factory
         var factory = this.animationProperties.Count > 0
-            ? Window.Current.Compositor.CreateEffectFactory(effect, this.animationProperties)
-            : Window.Current.Compositor.CreateEffectFactory(effect);
+            ? compositor.CreateEffectFactory(effect, this.animationProperties)
+            : compositor.CreateEffectFactory(effect);
 
         // Create the effect factory and apply the final effect
         var effectBrush = factory.CreateBrush();
@@ -191,7 +197,13 @@ public async Task<CompositionBrush> BuildAsync()
     /// <returns>A <see cref="Task{T}"/> that returns the final <see cref="SpriteVisual"/> instance to use</returns>
     public async Task<SpriteVisual> AttachAsync(UIElement target, UIElement? reference = null)
     {
-        SpriteVisual visual = Window.Current.Compositor.CreateSpriteVisual();
+#if WINUI2
+        var compositor = Window.Current.Compositor;
+#elif WINUI3
+        var compositor = CompositionTarget.GetCompositorForCurrentThread();
+#endif
+
+        SpriteVisual visual = compositor.CreateSpriteVisual();
 
         visual.Brush = await BuildAsync();