add drawing surface interop..

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

@@ -2,6 +2,7 @@
 using System.Runtime.InteropServices;
 using Avalonia.OpenGL.Angle;
 using Windows.UI.Composition;
+using Windows.UI.Composition.Interop;
 using WinRT;
 
 namespace Avalonia.Win32
@@ -89,8 +90,24 @@ namespace Avalonia.Win32
 
             var gDevice = interop.CreateGraphicsDevice(display.GetDirect3DDevice());
 
-            gDevice.CreateDrawingSurface(new Windows.Foundation.Size(100,100), Windows.Graphics.DirectX.DirectXPixelFormat.B8G8R8A8UIntNormalized, Windows.Graphics.DirectX.DirectXAlphaMode.Premultiplied);
-                
+            var surface = gDevice.CreateDrawingSurface(new Windows.Foundation.Size(100,100), Windows.Graphics.DirectX.DirectXPixelFormat.B8G8R8A8UIntNormalized, Windows.Graphics.DirectX.DirectXAlphaMode.Premultiplied);
+
+            var surfaceInterop = surface.As<ICompositionDrawingSurfaceInterop>();
+
+            surfaceInterop.BeginDraw(new Windows.Foundation.Rect(0, 0, 100, 100), Guid.Parse("6f15aaf2-d208-4e89-9ab4-489535d34f9c"), out var texture, new Windows.Foundation.Point(0, 0));
+            surfaceInterop.EndDraw();
+            
+            var brush = _compositor.CreateSurfaceBrush(surface);
+
+            var visual = _compositor.CreateSpriteVisual();
+
+            visual.RelativeSizeAdjustment = new System.Numerics.Vector2(1.0f, 1.0f);
+            visual.Brush = brush;
+
+            _target.Root = visual;
+
+            AddElement(100, 200, 200);
+
         }
 
         public void CreateBlur()

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

@@ -0,0 +1,135 @@
+using System;
+using System.Runtime.InteropServices;
+using Windows.Foundation;
+using WinRT;
+
+namespace Windows.UI.Composition.Interop
+{
+    [WindowsRuntimeType]
+    [Guid("FD04E6E3-FE0C-4C3C-AB19-A07601A576EE")]
+    public interface ICompositionDrawingSurfaceInterop
+    {
+        void BeginDraw(Rect updateRect, Guid iid, out IntPtr updateObject, Point point);
+
+        void EndDraw();
+
+        void Resize(Size sizePixels);
+
+        void ResumeDraw();
+
+        void Scroll(Rect scrollRect, Rect clipRect, int offsetX, int offsetY);
+
+        void SuspendDraw();
+    }
+}
+
+namespace ABI.Windows.UI.Composition.Interop
+{
+    using global::System;
+    using global::System.Runtime.InteropServices;
+    using global::Windows.UI.Composition;
+
+    [Guid("FD04E6E3-FE0C-4C3C-AB19-A07601A576EE")]
+    internal class ICompositionDrawingSurfaceInterop : global::Windows.UI.Composition.Interop.ICompositionDrawingSurfaceInterop
+
+    {
+        [Guid("FD04E6E3-FE0C-4C3C-AB19-A07601A576EE")]
+        public struct Vftbl
+        {
+            public delegate int _BeginDraw(IntPtr ThisPtr, Guid iid, out IntPtr updateObject, Point updateOffset);
+            public delegate int _EndDraw(IntPtr ThisPtr);
+            public delegate int _Resize(IntPtr ThisPtr, Size sizePixels);
+            public delegate int _ResumeDraw(IntPtr ThisPtr);
+            public delegate int _Scroll(IntPtr ThisPtr, Rect scrollRect, Rect clipRect, int offsetX, int offsetY);
+            public delegate int _SuspendDraw(IntPtr ThisPtr);
+
+            internal global::WinRT.Interop.IUnknownVftbl IUnknownVftbl;
+            public _BeginDraw BeginDraw;
+            public _EndDraw EndDraw;
+            public _Resize Resize;
+            public _ResumeDraw ResumeDraw;
+            public _Scroll Scroll;
+            public _SuspendDraw SuspendDraw;
+
+            public static readonly Vftbl AbiToProjectionVftable;
+            public static readonly IntPtr AbiToProjectionVftablePtr;
+
+            static Vftbl()
+            {
+                AbiToProjectionVftable = new Vftbl
+                {
+                    IUnknownVftbl = global::WinRT.Interop.IUnknownVftbl.AbiToProjectionVftbl,
+
+                    BeginDraw = Do_Abi_BeginDraw,
+                    EndDraw = Do_Abi_EndDraw,
+                    Resize = Do_Abi_Resize
+
+
+                };
+                AbiToProjectionVftablePtr = Marshal.AllocHGlobal(Marshal.SizeOf<Vftbl>());
+                Marshal.StructureToPtr(AbiToProjectionVftable, AbiToProjectionVftablePtr, false);
+            }
+
+            private static int Do_Abi_BeginDraw(IntPtr ThisPtr, Guid iid, out IntPtr updateObject, Point updateOffset)
+            {
+                updateObject = IntPtr.Zero;
+                return 0;
+            }
+
+            private static int Do_Abi_EndDraw(IntPtr ThisPtr)
+            {
+                return 0;
+            }
+
+            private static int Do_Abi_Resize(IntPtr ThisPtr, Size sizePixels)
+            {
+                return 0;
+            }
+        }
+        internal static ObjectReference<Vftbl> FromAbi(IntPtr thisPtr) => ObjectReference<Vftbl>.FromAbi(thisPtr);
+
+        public static implicit operator ICompositionDrawingSurfaceInterop(IObjectReference obj) => (obj != null) ? new ICompositionDrawingSurfaceInterop(obj) : null;
+        protected readonly ObjectReference<Vftbl> _obj;
+        public IObjectReference ObjRef { get => _obj; }
+        public IntPtr ThisPtr => _obj.ThisPtr;
+        public ObjectReference<I> AsInterface<I>() => _obj.As<I>();
+        public A As<A>() => _obj.AsType<A>();
+
+        public ICompositionDrawingSurfaceInterop(IObjectReference obj) : this(obj.As<Vftbl>()) { }
+        internal ICompositionDrawingSurfaceInterop(ObjectReference<Vftbl> obj)
+        {
+            _obj = obj;
+        }
+
+        public void BeginDraw(Rect updateRect, Guid iid, out IntPtr updateObject, Point point)
+        {
+            Marshal.ThrowExceptionForHR(_obj.Vftbl.BeginDraw(ThisPtr, iid, out updateObject, point));
+        }
+
+        public void EndDraw()
+        {
+            Marshal.ThrowExceptionForHR(_obj.Vftbl.EndDraw(ThisPtr));
+        }
+
+        public void Resize(Size sizePixels)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void ResumeDraw()
+        {
+            throw new NotImplementedException();
+        }
+
+        public void Scroll(Rect scrollRect, Rect clipRect, int offsetX, int offsetY)
+        {
+            throw new NotImplementedException();
+        }
+
+        public void SuspendDraw()
+        {
+            throw new NotImplementedException();
+        }        
+    }
+}
+

src/Windows/Avalonia.Win32/Composition/IGraphicsEffectD2D1Interop1.cs

@@ -122,7 +122,7 @@ namespace ABI.Windows.Graphics.Effects.Interop
                 value = default;
 
                 try
-                {
+                {                    
                     var source = ComWrappersSupport.FindObject<global::Windows.Graphics.Effects.Interop.IGraphicsEffectD2D1Interop>(thisPtr).GetSource(index);
 
                     value = MarshalInterface<global::Windows.Graphics.Effects.IGraphicsEffectSource>.FromManaged(source);