mono/xwt — comment on commit 02f65feeca738635639bf22179e0eb0187946617
File: Xwt.WPF/Xwt.WPFBackend/CanvasBackend.cs line 56
By ermau:

Not sure how this causes a problem there. The only problem I could see is if QueueDraw (rect), QueueDraw(), QueueDraw (rect) was valid. No dirty rects means the whole thing is dirty.