RESOLVED FIXED 86651
FrameView::scrollContentsFastPath should use painted area to determine whether to drop out of the fast path 
https://bugs.webkit.org/show_bug.cgi?id=86651
Summary FrameView::scrollContentsFastPath should use painted area to determine whethe...
Tim Horton
Reported 2012-05-16 10:23:40 PDT
<rdar://problem/11459243> FrameView::scrollContentsFastPath has a fixedObjectThreshold of 5: if there are more than 5 fixed-positioning elements on the page, it will fall out of the fast (blit) path and repaint everything. This doesn't make sense - causing repaints of the whole page just because someone used 5 (or 10, or whatever) tiny fixed-position elements is wasteful (and vice versa, blitting the whole window and then just going ahead and redrawing it all because someone used only one enormous fixed-position element also doesn't make sense). We can make trivial use of regions and threshold based on percentage of the view that will need to be repainted by fixed-position elements. I've tested a few different thresholds with an internal test; 50% seems to work relatively well, but the ideal value is hard to determine and likely depends on hardware. I have a patch.
Attachments
patch (5.63 KB, patch)
2012-05-16 10:29 PDT, Tim Horton 		simon.fraser: review+
DetailsFormatted DiffDiff
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Tim Horton
Comment 1 2012-05-16 10:29:48 PDT
Created attachment 142292 [details] patch
Tim Horton
Comment 2 2012-05-16 11:41:47 PDT
http://trac.webkit.org/changeset/117313
Adrienne Walker
Comment 3 2012-05-16 12:23:10 PDT
Ooh, that's excellent. That seems like a much better heuristic.
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