[Mac] Fix image rendering

Xwt.Mac/Xwt.Mac/ContextBackendHandler.cs

@@ -250,8 +250,10 @@ namespace Xwt.Mac
 						((CustomImage)pi.Image).DrawInContext (c);
 					});
 				} else {
-					pattern = new CGPattern (bounds, t, bounds.Width, bounds.Height,
-				                      CGPatternTiling.ConstantSpacing, true, c => c.DrawImage (bounds, null));
+					RectangleF empty = RectangleF.Empty;
+					CGImage cgimg = ((NSImage)pi.Image).AsCGImage (ref empty, null, null);
+					pattern = new CGPattern (bounds, CGAffineTransform.MakeScale (1f, -1f), bounds.Width, bounds.Height,
+					                         CGPatternTiling.ConstantSpacing, true, c => c.DrawImage (bounds, cgimg));
 				}
 
 				CGContext ctx = gc.Context;

Xwt.Mac/Xwt.Mac/ImageHandler.cs

@@ -130,8 +130,8 @@ namespace Xwt.Mac
 
 				var ctx = new CGContextBackend {
 					Context = bmp,
-					Size = new SizeF (pixelWidth, pixelHeight)/*,
-					InverseViewTransform = bmp.GetCTM ().Invert ()*/
+					Size = new SizeF (pixelWidth, pixelHeight),
+					InverseViewTransform = bmp.GetCTM ().Invert ()
 				};
 
 				var ci = (CustomImage)handle;
@@ -271,7 +271,7 @@ namespace Xwt.Mac
 
 		internal void DrawInContext (CGContextBackend ctx)
 		{
-			var s = Size;
+			var s = ctx.Size != SizeF.Empty ? ctx.Size : Size;
 			actx.InvokeUserCode (delegate {
 				drawCallback (ctx, new Rectangle (0, 0, s.Width, s.Height));
 			});