Avoid using NSUnionRect for dirtying, as that does not work with empty rects.
Avoid using NSUnionRect for dirtying, as that does not work with empty rects.
ycaihua/skim-app,ycaihua/skim-app,ycaihua/skim-app,WoLpH/skim,ycaihua/skim-app,WoLpH/skim,WoLpH/skim,ycaihua/skim-app,WoLpH/skim,WoLpH/skim