Bug 58515

Summary: Translucent scrollbars on composited layers render incorrectly
Product: WebKit Reporter: James Robinson <jamesr>
Component: Layout and RenderingAssignee: Simon Fraser (smfr) <simon.fraser>
Status: RESOLVED FIXED    
Severity: Normal CC: bdakin, sam, simon.fraser
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Mac   
OS: OS X 10.5   
Attachments:
Description Flags
testcase
none
Patch sam: review+

Description James Robinson 2011-04-13 22:51:03 PDT 
See the attached test case.  It appears that when the RenderLayer owning the scrollbars becomes composited we somehow render the translucent scrollbars twice on top of each other or something of the like.  I can reproduce the issue in Chromium, WebKit nightlies, and minibrowser.  The patch on bug 57202 ensures that this bug doesn't happen when the overflow controls are on their own layer, but it doesn't help when the controls are not.
Comment 1 James Robinson 2011-04-13 22:52:15 PDT 
Created attachment 89537 [details]
testcase

This page has a div with overflow:auto with custom scrollbars set to rgba(0, 127, 0, 0.5).  The div alternates between being composited and not composited every second.  When it's composited, the scrollbar regions appear 'more green' then they should.
Comment 2 Simon Fraser (smfr) 2011-08-29 17:43:39 PDT 
Looks like this was cased by https://bugs.webkit.org/show_bug.cgi?id=23740
Comment 3 Simon Fraser (smfr) 2011-09-09 16:22:41 PDT 
Created attachment 106935 [details]
Patch
Comment 4 Simon Fraser (smfr) 2011-09-26 22:11:34 PDT 
http://trac.webkit.org/changeset/96069