Track direct window cairo access and avoid tricks when used
When a cairo surface is requested for direct window access (i.e. not when double-buffering) we can't really track when the actual drawing happens as cairo drawing is not virtualized. This means we can't properly flush any outstanding window moves or implicit paints. This actually causes problems with e.g. abiword (bug #606009) where they draw without double-buffering. If you press down it scrolls the window and then draws the caret, but the caret drawing does not flush the outstanding move from the scroll, so the caret gets drawn on the wrong screen. We fix this by never allowing either implicit paints or outstanding window moves on impl-windows where any windows related to it has an outstanding direct cairo surface. Luckily this is not very common so in practice this doesn't matter much.
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