Add support for locating custom renderers

src/Avalonia.Visuals/Media/DrawingContext.cs

@@ -59,7 +59,7 @@ namespace Avalonia.Media
         //HACK: This is a temporary hack that is used in the render loop 
         //to update TransformedBounds property
         [Obsolete("HACK for render loop, don't use")]
-        internal Matrix CurrentContainerTransform => _currentContainerTransform;
+        public Matrix CurrentContainerTransform => _currentContainerTransform;
 
         /// <summary>
         /// Draws a bitmap image.

src/Avalonia.Visuals/Rendering/IRendererFactory.cs

@@ -0,0 +1,20 @@
+// Copyright (c) The Avalonia Project. All rights reserved.
+// Licensed under the MIT license. See licence.md file in the project root for full license information.
+
+using System;
+
+namespace Avalonia.Rendering
+{
+    /// <summary>
+    /// Defines the interface for a renderer factory.
+    /// </summary>
+    public interface IRendererFactory
+    {
+        /// <summary>
+        /// Creates a renderer.
+        /// </summary>
+        /// <param name="root">The root visual.</param>
+        /// <param name="renderLoop">The render loop.</param>
+        IRenderer Create(IRenderRoot root, IRenderLoop renderLoop);
+    }
+}

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -124,9 +124,12 @@ namespace Avalonia.Win32
         public IRenderer CreateRenderer(IRenderRoot root)
         {
             var loop = AvaloniaLocator.Current.GetService<IRenderLoop>();
-            return Win32Platform.UseDeferredRendering ?
-                (IRenderer)new DeferredRenderer(root, loop) :
-                new ImmediateRenderer(root);
+            var customRendererFactory = AvaloniaLocator.Current.GetService<IRendererFactory>();
+
+            if (customRendererFactory != null)
+                return customRendererFactory.Create(root, loop);
+
+            return Win32Platform.UseDeferredRendering ? (IRenderer)new DeferredRenderer(root, loop) : new ImmediateRenderer(root);
         }
 
         public void Resize(Size value)