Hi Julien, As you probably are aware, some mobile ports paint their own overlay scroll indicators and do scrolling on the UI side (div overflow using a separate layer)
Would it be possible to refactor this code in a way that it would simplify the code paths for these ports? maybe avoiding it altogether. Currently there is a lot of scrolling code in FrameView/ScrollView etc as well which we avoid call when delegatesScrolling() is true. Cheers, Kenneth On Tue, Dec 27, 2011 at 5:50 PM, Julien Chaffraix <[email protected]> wrote: > Hi fellow hackers, > > while investigating some slowness related to painting big HTML tables > [1], RenderLayer's painting code path was pointed out as the source of > slowness. The problem stems from RenderLayer not being aware of the > peculiarities of the underlying RenderObject (RenderTableSection > implements painting using a binary search to find out which cells to > paint instead of trying all cells like RenderLayer). > > Looking closely, it seems that the current code path is sub-optimal. > Adding an overflow clip on an element should be a cheap operation but > it ends up not being the case. This is because RenderLayer needs to > handle a lot of different use cases (transforms, opacity, z-index...) > [2]. I have spend some time thinking about how to make clipping a > cheaper operation and it looks like we could factor out most of the > scrolling logic (scroll offset, scrollbars, ScrollableArea) into a > light-weight object. This object would be orthogonal to RenderLayer. > The painting would go through "normal" (ie without layer) code path > that can already handle the clipping. > > As a first step, I took over [3] (splitting ScrollableArea out of > RenderLayer) but would like to get some feedbacks whether this > proposal sounds like something we would like to do or there are some > core issues I missed. > > Any comments welcome! > > Thanks, > Julien > > [1] https://bugs.webkit.org/show_bug.cgi?id=75001 > [2] I would argue that RenderLayer itself is a big memory overhead but > that's another debate. > [3] https://bugs.webkit.org/show_bug.cgi?id=60305 > _______________________________________________ > webkit-dev mailing list > [email protected] > http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev -- Kenneth Rohde Christiansen Senior Engineer Nokia Mobile Phones, Browser / WebKit team Phone +45 4093 0598 / E-mail kenneth at webkit.org http://codeposts.blogspot.com ﹆﹆﹆ _______________________________________________ webkit-dev mailing list [email protected] http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
