protected override void OnRender(System.Windows.Media.DrawingContext drawingContext)
{
// Draw something so that rendering does something. This
// is part of the fix for rendering artifacts, see WndProc
// hooking WM_WINDOWPOSCHANGED too.
//
// TODO: this actually makes things worse! At least on my home machine...
if (Background != null) {
drawingContext.DrawRectangle(Background, null, new Rect(RenderSize));
}
base.OnRender(drawingContext);
}