We don't need to always repaint overlay scrollbars if they're in layers
authorandersca@apple.com <andersca@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Fri, 27 Jan 2012 00:31:29 +0000 (00:31 +0000)
committerandersca@apple.com <andersca@apple.com@268f45cc-cd09-0410-ab3c-d52691b4dbfc>
Fri, 27 Jan 2012 00:31:29 +0000 (00:31 +0000)
commit4dcc7b0c7a8c47b4e67a1a562507be306fa7a404
tree418e83c59128c4328a9d3e5e1ecf94a26c312d34
parent5d0d535242603449325656abdffff58273d61b2a
We don't need to always repaint overlay scrollbars if they're in layers
https://bugs.webkit.org/show_bug.cgi?id=77159

Reviewed by Beth Dakin.

If a scrollable area has overlay scrollbars we'll always invalidate both scrollbars, regardless of
whether both scroll offsets actually change since they're translucent and we want to draw the new page
contents underneath.

However, if the scrollbars are painted into GraphicsLayers they'll be composited by the GPU, and so we don't
need to repaint them unless the corresponding scroll offset actually changes (which is handled in Scrollbar::updateThumb).

* platform/ScrollableArea.cpp:
(WebCore::ScrollableArea::setScrollOffsetFromAnimation):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@106061 268f45cc-cd09-0410-ab3c-d52691b4dbfc
Source/WebCore/ChangeLog
Source/WebCore/platform/ScrollableArea.cpp