private void WithExtraCanvas(Rectangle rect, Action <X11Canvas> action) { using (X11Image tempImage = X11Image.Create(display, visual, drawableId, rect.Width, rect.Height)) { var gcValues = new XGCValues(); gcValues.foreground = ToPArgb(Color.Transparent); var gcValueMask = XGCValueMask.GCForeground; var gc = LibX11.XCreateGC(display, drawableId, gcValueMask, ref gcValues); try { // todo: check int -> uint conversion LibX11.XFillRectangle(display, tempImage.PixmapId, gc, 0, 0, (uint)rect.Width, (uint)rect.Height); } finally { LibX11.XFreeGC(display, gc); } using (var innerCanvas = X11Canvas.CreateForDrawable(display, screenNum, objectCache, visual, colormap, pictFormatPtr, tempImage.PixmapId)) { action(innerCanvas); DrawImage(tempImage, rect.X + origin.X, rect.Y + origin.Y); } } }