Merge pull request #2553 from cwensley/curtis/wpf-more-rendertargetbitmap

Wpf: Don't store RenderTargetBitmap anywhere

Author: cwensley

src/Eto.Wpf/Drawing/BitmapHandler.cs

@@ -137,6 +137,8 @@ protected override void Initialize()
 
 		public void SetBitmap(swmi.BitmapSource bitmap)
 		{
+			if (bitmap is swmi.RenderTargetBitmap)
+				bitmap = new swmi.WriteableBitmap(bitmap);
 			Control = bitmap;
 			SetFrozen();
 		}

src/Eto.Wpf/Drawing/CachedBitmapFrame.cs

@@ -38,10 +38,11 @@ public swmi.BitmapFrame Get(swmi.BitmapSource image, float scale, int width, int
 			// There's no way to get around it other than just not creating that many and using GC.Collect/WaitForPendingFinalizers.
 			// we can't do it in Eto as it'd be a serious performance hit.
 			var target = new swmi.RenderTargetBitmap(scaledwidth, scaledheight, 96 * scale, 96 * scale, swm.PixelFormats.Default);
-			target.Render(targetVisual);
-			target.Freeze();
+			target.RenderWithCollect(targetVisual);
+			
+			var writable = new swmi.WriteableBitmap(target);
 
-			_cachedFrame = swmi.BitmapFrame.Create(target);
+			_cachedFrame = swmi.BitmapFrame.Create(writable);
 			_cachedFrame.Freeze();
 			_scale = scale;
 			_width = width;