Bug 98578 – REGRESSION (r128787): Fixed position div unexpectedly moves to textarea

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Kevin M. Dean]

This test link is reduced from a wordpress admin page where it places a admin bar with a position: fixed; on it.

Load the test page. Select all the text, copy and then paste it below the existing text. Then select undo (Command-Z) and the dark bar at the top will jump to the 0,0 coordinate of the textarea when it should stay where it is.

I believe there's other triggers since I've had this come up in other places in wordpress and another site editor.

[Kevin M. Dean]

Created attachment 167430 [details]
Before

[Kevin M. Dean]

Created attachment 167432 [details]
after

[Kevin M. Dean]

Removing the position: fixed; from the top div with Web Inspector causes the glitch to not occur.

[Kevin M. Dean]

Likely related to Bug 98579.

[Kevin M. Dean]

After pasting, pressing the delete key until a line is completely removed will also trigger the glitch.

[Alexey Proskuryakov]

In debug builds, an assertion fails:

ASSERTION FAILED: enclosingIntRect(rendererMappedResult) == enclosingIntRect(FloatQuad(result).boundingBox())
/Users/ap/Safari/OpenSource/Source/WebCore/rendering/RenderGeometryMap.cpp(85) : WebCore::FloatRect WebCore::RenderGeometryMap::absoluteRect(const WebCore::FloatRect &) const
1   0x10aa81d19 WebCore::RenderGeometryMap::absoluteRect(WebCore::FloatRect const&) const
2   0x10aacea1e WebCore::RenderLayerCompositor::addToOverlapMap(WebCore::RenderLayerCompositor::OverlapMap&, WebCore::RenderLayer*, WebCore::IntRect&, bool&)
3   0x10aacc912 WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer*, WebCore::RenderLayerCompositor::OverlapMap*, WebCore::CompositingState&, bool&, bool&)
4   0x10aacc7ef WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer*, WebCore::RenderLayerCompositor::OverlapMap*, WebCore::CompositingState&, bool&, bool&)
5   0x10aacc7ef WebCore::RenderLayerCompositor::computeCompositingRequirements(WebCore::RenderLayer*, WebCore::RenderLayer*, WebCore::RenderLayerCompositor::OverlapMap*, WebCore::CompositingState&, bool&, bool&)
6   0x10aacbd84 WebCore::RenderLayerCompositor::updateCompositingLayers(WebCore::CompositingUpdateType, WebCore::RenderLayer*)
7   0x10aa9fd6e WebCore::RenderLayer::updateCompositingLayersAfterScroll()
8   0x10aa9f8a3 WebCore::RenderLayer::scrollTo(int, int)
9   0x10aaa20ae WebCore::RenderLayer::setScrollOffset(WebCore::IntPoint const&)
10  0x10acdf84d WebCore::ScrollableArea::scrollPositionChanged(WebCore::IntPoint const&)

[Alexey Proskuryakov]

<rdar://problem/12454637>

[Simon Fraser (smfr)]

I am going to fix the assertion via bug 101292.

[Beth Dakin]

I can no longer reproduce this bug on TOT. Kevin, do you still see this?

[Simon Fraser (smfr)]

What if you disable the compositing-for-fixed stuff?

[Kevin M. Dean]

(In reply to comment #9)
> I can no longer reproduce this bug on TOT. Kevin, do you still see this?

I no longer see this specific case, but I do see a similar issue in another area of wordpress where a table row is removed via javascript and the page scrolls back to the top, but the fixed div jumps down the page until you click. I'll upload a before/after.

[Kevin M. Dean]

Created attachment 183269 [details]
Table Row Before

[Kevin M. Dean]

Created attachment 183270 [details]
Table Row After

[Kevin M. Dean]

I've set up a wordpress test area if you want to login and take a look. Just respond here or send me an email directly for the access information and instructions to trigger the bug.

[Kevin M. Dean]

This bug seems to happen in a different range, so I should probably open a new bug for it.

[Kevin M. Dean]

OK, if you're interested, head over to:

Bug 107179 - REGRESSION (r139554-r139561): Fixed position div unexpectedly moves after table row removed

[Beth Dakin]

Thanks, Kevin! And Simon, I tried your experiment and the bug still did not repro. This particular issue does seem to be fixed.