зеркало из https://github.com/mozilla/gecko-dev.git
0471905a26
Previously our region code was just a simple y,x sorted list of non-intersecting rectangles. This can cause us to have simple regions represented in a complex unoptimizable way. Switching to pixman regions gives us a canonical region implementation. There are some cases when this can cause performance regressions. For example, with the old region code we end up with this region: http://people.mozilla.org/~jmuizelaar/region-pre.html which is represented like this: http://people.mozilla.org/~jmuizelaar/region-post.html with the new code. We call SimplifyOutward(4) on this. With old regions we can't simplify it so we end up taking the bounds and get 1 rect. With the new regions we have only 3 rects to start and so we do nothing. The difference between 3 rects and 1 rect cause D2D to do a PushLayer() instead of a ClipRect() and that seems to be the causes for the regression. --HG-- extra : rebase_source : 65e0d29d67b51a3780448eaecfde33dbcb6b99b1 |
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