NULLREGION means that the entire window should be clipped out, and its children displayed instead. The change broke some offscreening decisions when both parent and children have a GL drawable created but drawing actually happens on the child window. (Found while trying to reproduce otherwise unrelated regression in https://bugs.winehq.org/show_bug.cgi?id=52738, the game there uses ddraw and doesn't display anything after 786d9d1685ac220081b10cc779d4d331ddd2fc52) Fixes: 786d9d1685ac220081b10cc779d4d331ddd2fc52 Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57503 -- v2: winex11: Move GL/VK offscreen if the clipping region is NULLREGION. winex11: Use DCX_USESTYLE when checking DC clipping regions. https://gitlab.winehq.org/wine/wine/-/merge_requests/7014