simplify composition connection.

src/Windows/Avalonia.Win32/Composition/CompositionConnector.cs

@@ -39,24 +39,13 @@ namespace Avalonia.Win32
         [DllImport("coremessaging.dll", EntryPoint = "CreateDispatcherQueueController", CharSet = CharSet.Unicode)]
         internal static extern IntPtr CreateDispatcherQueueController(DispatcherQueueOptions options, out IntPtr dispatcherQueueController);
 
-        public static CompositionConnector Instance { get; } = new CompositionConnector();
-
         private Compositor _compositor;
         private Windows.System.DispatcherQueueController _dispatcherQueueController;
         private CompositionGraphicsDevice _graphicsDevice;
 
-        private CompositionConnector()
+        internal CompositionConnector(EglPlatformOpenGlInterface egl)
         {
-            var glPlatform = AvaloniaLocator.Current.GetService<IPlatformOpenGlInterface>();
-
-            if (glPlatform is EglPlatformOpenGlInterface egl)
-            {
-                Initialize(egl);
-            }
-            else
-            {
-                throw new PlatformNotSupportedException();
-            }
+            Initialize(egl);
         }
 
         private void Initialize(EglPlatformOpenGlInterface egl)

src/Windows/Avalonia.Win32/Composition/CompositionEglGlPlatformSurface.cs

@@ -21,11 +21,11 @@ namespace Avalonia.Win32
             _info = info;
         }
 
-        public IBlurHost AttachToCompositionTree(IntPtr hwnd)
+        public IBlurHost AttachToCompositionTree(CompositionConnector connector, IntPtr hwnd)
         {
             using (_egl.PrimaryContext.MakeCurrent())
             {
-                _surfaceInterop = CompositionConnector.Instance.InitialiseWindowCompositionTree(hwnd, out _surface, out var blurHost);
+                _surfaceInterop = connector.InitialiseWindowCompositionTree(hwnd, out _surface, out var blurHost);
                 return blurHost;
             }
         }

src/Windows/Avalonia.Win32/Win32GlManager.cs

@@ -7,8 +7,6 @@ namespace Avalonia.Win32
 {
     static class Win32GlManager
     {
-        private static bool s_attemptedToInitialize;
-
         public static void Initialize()
         {
             AvaloniaLocator.CurrentMutable.Bind<IPlatformOpenGlInterface>().ToLazy<IPlatformOpenGlInterface>(() =>
@@ -19,9 +17,21 @@ namespace Avalonia.Win32
                     var wgl = WglPlatformOpenGlInterface.TryCreate();
                     return wgl;
                 }
-                
+
                 if (opts?.AllowEglInitialization == true)
-                    return EglPlatformOpenGlInterface.TryCreate(() => new AngleWin32EglDisplay());
+                {
+                    var egl = EglPlatformOpenGlInterface.TryCreate(() => new AngleWin32EglDisplay());
+
+                    if (egl is { } &&
+                    opts?.UseWindowsUIComposition == true &&
+                    Win32Platform.WindowsVersion.Major >= 10 &&
+                    Win32Platform.WindowsVersion.Build >= 16299)
+                    {
+                        AvaloniaLocator.CurrentMutable.BindToSelf(new CompositionConnector(egl));
+                    }
+
+                    return egl;
+                }
 
                 return null;
             });

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -12,6 +12,7 @@ using Avalonia.Controls.Platform;
 using Avalonia.Input;
 using Avalonia.Input.Platform;
 using Avalonia.OpenGL;
+using Avalonia.OpenGL.Egl;
 using Avalonia.Platform;
 using Avalonia.Rendering;
 using Avalonia.Threading;
@@ -113,7 +114,7 @@ namespace Avalonia.Win32
                 .Bind<IMountedVolumeInfoProvider>().ToConstant(new WindowsMountedVolumeInfoProvider());
 
             Win32GlManager.Initialize();
-            
+
             _uiThread = Thread.CurrentThread;
 
             if (OleContext.Current != null)

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -107,9 +107,10 @@ namespace Avalonia.Win32
 
             var glPlatform = AvaloniaLocator.Current.GetService<IPlatformOpenGlInterface>();
 
-            _isUsingComposition = Win32Platform.Options.UseWindowsUIComposition &&
-                Win32Platform.WindowsVersion.Major >= 10 && Win32Platform.WindowsVersion.Build >= 16299 &&
-                    glPlatform != null && glPlatform is EglPlatformOpenGlInterface egl &&
+            var compositionConnector = AvaloniaLocator.Current.GetService<CompositionConnector>();
+
+            _isUsingComposition = compositionConnector is { } &&
+                glPlatform is EglPlatformOpenGlInterface egl &&
                     egl.Display is AngleWin32EglDisplay angleDisplay &&
                     angleDisplay.PlatformApi == AngleOptions.PlatformApi.DirectX11;
 
@@ -121,7 +122,7 @@ namespace Avalonia.Win32
                 if (_isUsingComposition)
                 {
                     var cgl = new CompositionEglGlPlatformSurface(glPlatform as EglPlatformOpenGlInterface, this);
-                    _blurHost = cgl.AttachToCompositionTree(_hwnd);
+                    _blurHost = cgl.AttachToCompositionTree(compositionConnector, _hwnd);
 
                     _gl = cgl;