Try to fix a bug where a window move, with a non-rectangular region
Try to fix a bug where a window move, with a non-rectangular region unobstructed, would cause pieces of the window to be moved twice. Effectively, sort of implement a gdk_draw_drawable_region(drawable, gc, drawable, region, dx, dy); Am going blind trying to find the off-by-one thing, especially since it doesn't happen except for the preview tests. Still not fixed, have at it.
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