Throw an exception when CustomPlatformGraphics is used with unsupported Win32CompositionMode

src/Windows/Avalonia.Win32/Win32Platform.cs

@@ -99,9 +99,24 @@ namespace Avalonia.Win32
                 .Bind<NonPumpingLockHelper.IHelperImpl>().ToConstant(NonPumpingWaitHelperImpl.Instance)
                 .Bind<IMountedVolumeInfoProvider>().ToConstant(new WindowsMountedVolumeInfoProvider())
                 .Bind<IPlatformLifetimeEventsImpl>().ToConstant(s_instance);
-            
-            var platformGraphics = options.CustomPlatformGraphics
-                                   ?? Win32GlManager.Initialize();
+
+            IPlatformGraphics? platformGraphics;
+            if (options.CustomPlatformGraphics is not null)
+            {
+                if (options.CompositionMode.HasValue
+                    && options.CompositionMode != Win32CompositionMode.RedirectionSurface)
+                {
+                    throw new InvalidOperationException(
+                        $"{nameof(Win32PlatformOptions)}.{nameof(Win32PlatformOptions.CustomPlatformGraphics)} is only " +
+                        $"compatible with {nameof(Win32CompositionMode)}.{nameof(Win32CompositionMode.RedirectionSurface)}");
+                }
+                
+                platformGraphics = options.CustomPlatformGraphics;
+            }
+            else
+            {
+                platformGraphics = Win32GlManager.Initialize();   
+            }
             
             if (OleContext.Current != null)
                 AvaloniaLocator.CurrentMutable.Bind<IPlatformDragSource>().ToSingleton<DragSource>();

src/Windows/Avalonia.Win32/Win32PlatformOptions.cs

@@ -91,7 +91,7 @@ public class Win32PlatformOptions
 
     /// <summary>
     /// Render directly on the UI thread instead of using a dedicated render thread.
-    /// Only applicable if <see cref="CompositionMode"/> is set to <see cref="Win32CompositionMode.None"/>.
+    /// Only applicable if <see cref="CompositionMode"/> is set to <see cref="Win32CompositionMode.RedirectionSurface"/>.
     /// This setting is only recommended for interop with systems that must render on the UI thread, such as WPF.
     /// This setting is false by default.
     /// </summary>
@@ -108,7 +108,8 @@ public class Win32PlatformOptions
 
     /// <summary>
     /// Provides a way to use a custom-implemented graphics context such as a custom ISkiaGpu.
-    /// When this property set <see cref="RenderingMode"/> and <see cref="CompositionMode"/> are completely ignored.
+    /// When this property set <see cref="RenderingMode"/> is ignored
+    /// and <see cref="CompositionMode"/> only accepts null or <see cref="Win32CompositionMode.RedirectionSurface"/>.
     /// </summary>
     public IPlatformGraphics? CustomPlatformGraphics { get; set; }
 }