107326 2013-01-18 14:33:07 -0800 Rubberband scrolling on news.google.com causes text to blink repeatedly 2013-01-29 21:40:11 -0800 1 1 1 Unclassified WebKit Layout and Rendering 528+ (Nightly build) Mac OS X 10.8 RESOLVED FIXED https://news.google.com InRadar P2 Normal --- 1 esprehn simon.fraser bdakin eric jamesr ojan.autocc simon.fraser vollick webkit-bug-importer webkit.review.bot oldest_to_newest 811050 0 esprehn 2013-01-18 14:33:07 -0800 In Webkit nightlies (but not Chrome canary) when you two finger scroll to the bottom of news.google.com and then scroll some more so the page bounces up and then back down the side bar of categories on the left has all of it's text blink at you several times. This seems to be some kind of compositing badness. 811051 1 esprehn 2013-01-18 14:34:11 -0800 Note that the sidebar is position: fixed in this scenario, so I think it's rubber banding + position fixed + compositing. 811060 2 webkit-bug-importer 2013-01-18 14:41:46 -0800 <rdar://problem/13045436> 819605 3 simon.fraser 2013-01-29 18:02:51 -0800 The fixed thing is dropping out of a layer briefly, because we think it's layer is at 0,0 in the view (the Y offset should be larger). 819606 4 simon.fraser 2013-01-29 18:03:01 -0800 s/it's/its 819730 5 simon.fraser 2013-01-29 20:28:17 -0800 When we destroy the fixed layer because we think it's outside the viewport, the render tree is actually needing layout: RenderView 0x1180834f8 at (0,0) size 1143x605 (needs layout: positioned child) and the fixed layer has a bogus 0,0 location: layer 0x10d67eca8 at (0,0) size 196x606 scrollWidth 204 (composited, bounds=at (0,0) size 196x605, drawsContent=1, paints into ancestor=0) RenderBlock (positioned) 0x10d69ded8 zI: 99 {DIV} at (0,0) size 196x608 [bgcolor=#FFFFFF] id="nav-menu-wrapper" class="nav nav-one-col-hp jfk-scrollbar-borderless left-nav-pinned" (needs layout: self) RenderBlock 0x10d652d28 {DIV} at (28,3) size 152x553 class="browse-sidebar" 819733 6 simon.fraser 2013-01-29 20:32:13 -0800 Ah, we're actually inside layout at that point: * thread #1: tid = 0x2303, 0x00000001049d14a3 WebCore`WebCore::RenderLayerCompositor::requiresCompositingForPosition(WebCore::RenderObject*, WebCore::RenderLayer const*, WebCore::RenderLayer::ViewportConstrainedNotCompositedReason*) const + 755 at RenderLayerCompositor.cpp:2079, stop reason = breakpoint 8.1 frame #0: 0x00000001049d14a3 WebCore`WebCore::RenderLayerCompositor::requiresCompositingForPosition(WebCore::RenderObject*, WebCore::RenderLayer const*, WebCore::RenderLayer::ViewportConstrainedNotCompositedReason*) const + 755 at RenderLayerCompositor.cpp:2079 frame #1: 0x00000001049cc41d WebCore`WebCore::RenderLayerCompositor::requiresCompositingLayer(WebCore::RenderLayer const*, WebCore::RenderLayer::ViewportConstrainedNotCompositedReason*) const + 381 at RenderLayerCompositor.cpp:1645 frame #2: 0x00000001049ccdba WebCore`WebCore::RenderLayerCompositor::needsToBeComposited(WebCore::RenderLayer const*, WebCore::RenderLayer::ViewportConstrainedNotCompositedReason*) const + 74 at RenderLayerCompositor.cpp:1621 frame #3: 0x00000001049cc937 WebCore`WebCore::RenderLayerCompositor::updateBacking(WebCore::RenderLayer*, WebCore::RenderLayerCompositor::CompositingChangeRepaint) + 71 at RenderLayerCompositor.cpp:566 frame #4: 0x00000001049cd0e3 WebCore`WebCore::RenderLayerCompositor::updateLayerCompositingState(WebCore::RenderLayer*, WebCore::RenderLayerCompositor::CompositingChangeRepaint) + 35 at RenderLayerCompositor.cpp:659 frame #5: 0x000000010499b293 WebCore`WebCore::RenderLayer::updateScrollInfoAfterLayout() + 435 at RenderLayer.cpp:3097 frame #6: 0x0000000104864444 WebCore`WebCore::RenderBlock::updateScrollInfoAfterLayout() + 180 at RenderBlock.cpp:1349 frame #7: 0x0000000104865a0b WebCore`WebCore::RenderBlock::layoutBlock(bool, WebCore::LayoutUnit) + 2779 at RenderBlock.cpp:1589 frame #8: 0x00000001048644ce WebCore`WebCore::RenderBlock::layout() + 126 at RenderBlock.cpp:1363 frame #9: 0x0000000103bb8db6 WebCore`WebCore::RenderObject::layoutIfNeeded() + 54 at RenderObject.h:676 frame #10: 0x0000000104868cb4 WebCore`WebCore::RenderBlock::layoutPositionedObjects(bool, bool) + 724 at RenderBlock.cpp:2711 frame #11: 0x000000010486619e WebCore`WebCore::RenderBlock::simplifiedLayout() + 574 at RenderBlock.cpp:2604 frame #12: 0x000000010486500a WebCore`WebCore::RenderBlock::layoutBlock(bool, WebCore::LayoutUnit) + 218 at RenderBlock.cpp:1485 frame #13: 0x00000001048644ce WebCore`WebCore::RenderBlock::layout() + 126 at RenderBlock.cpp:1363 frame #14: 0x0000000104b3ad54 WebCore`WebCore::RenderView::layoutContent(WebCore::LayoutState const&) + 116 at RenderView.cpp:131 frame #15: 0x0000000104b3b54c WebCore`WebCore::RenderView::layout() + 1148 at RenderView.cpp:215 frame #16: 0x0000000103c4825d WebCore`WebCore::FrameView::layout(bool) + 3261 at FrameView.cpp:1213 frame #17: 0x00000001038f37d6 WebCore`WebCore::Document::updateLayout() + 374 at Document.cpp:1892 frame #18: 0x00000001049a0edd WebCore`WebCore::RenderLayer::hitTest(WebCore::HitTestRequest const&, RenderBlock::updateScrollInfoAfterLayout() is causing premature compositing stuff to happen inside layout. 819743 7 simon.fraser 2013-01-29 20:53:31 -0800 Looks like the code that was added for compositing scrolling is causing this. 819772 8 185393 simon.fraser 2013-01-29 21:32:27 -0800 Created attachment 185393 Patch 819779 9 simon.fraser 2013-01-29 21:40:11 -0800 http://trac.webkit.org/changeset/141221 185393 2013-01-29 21:32:27 -0800 2013-01-29 21:35:24 -0800 Patch bug-107326-20130129212912.patch text/plain 5295 simon.fraser 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