Bug 20047 – Incorrect rendering during opacity transition on element with positioned children

• Status: RESOLVED
• Resolution: FIXED
• Component: Layout and Rendering

[Simon Fraser (smfr)]

In the attached testcase, a positioned element runs a transition when its opacity changes on :hover. However, a child element which is positioned snaps to the final opacity, without showing the transition, which is wrong.

This only happens if:
* the child is positioned
* the target opacity is 1

I think it's related to stacking context changes when opacity hits 1.

[Simon Fraser (smfr)]

Created attachment 22293 [details]
Testcase

[Simon Fraser (smfr)]

Created attachment 22295 [details]
Better testcase; reveals stacking context

[Simon Fraser (smfr)]

Created attachment 22296 [details]
Patch (with some FIXMES)

[Dave Hyatt]

Comment on attachment 22296 [details]
Patch (with some FIXMES)

The property has to blend in order for this problem to be exposed.  I think you only need the opacity and transform checks.

[Simon Fraser (smfr)]

Created attachment 22321 [details]
Patch, testcase, changelogs

[Dave Hyatt]

Comment on attachment 22321 [details]
Patch, testcase, changelogs

r=me

[Dean Jackson]

Committing to http://svn.webkit.org/repository/webkit/trunk ...
	M	LayoutTests/ChangeLog
	A	LayoutTests/transitions/opacity-transition-zindex-expected.txt
	A	LayoutTests/transitions/opacity-transition-zindex.html
	M	WebCore/ChangeLog
	M	WebCore/page/AnimationController.cpp
Committed r35207