Bug 111855

Summary:

Rendered colors shift when element gets a layer

Product:

WebKit

Reporter:

Mihai Balan <mibalan>

Component:

Layout and Rendering

Assignee:

Nobody <webkit-unassigned>

Status:

NEW

Severity:

Normal

CC:

mibalan, mmaerean, simon.fraser, thorton

Priority:

Version:

528+ (Nightly build)

Hardware:

Unspecified

OS:

Unspecified

Attachments:

Description	Flags
Test-case	none
Screenshot of the bug in action :)	none
Magnified shot of the bug	none

Mihai Balan

Reported 2013-03-08 07:09:19 PST

Elements that have the same CSS color get actually rendered with slightly different hues if one of them is on a layer. This doesn't happen on all configurations - from my testing, on the Mac platform, it seems to be limited to Mac 10.8 if the video card is not an Intel chip (e.g. ATi or nVidia) See the attached sample - on configurations where the bug is present, the second line of text will be slightly redder (purple-blue) than the first line of text. The attached .png file shows how this bug manifests.

Attachments
Test-case (726 bytes, text/html) 2013-03-08 07:10 PST, Mihai Balan	no flags	Details
Screenshot of the bug in action :) (13.66 KB, image/png) 2013-03-08 07:14 PST, Mihai Balan	no flags	Details
Magnified shot of the bug (4.46 KB, image/png) 2013-03-08 07:22 PST, Mihai Balan	no flags	Details
View All Add attachment proposed patch, testcase, etc.

Mihai Balan

Comment 1 2013-03-08 07:10:39 PST

Created attachment 192220 [details] Test-case On platforms/configurations exhibiting the bug, the second line will be slightly purpler than the first line.

Mihai Balan

Comment 2 2013-03-08 07:14:55 PST

Created attachment 192223 [details] Screenshot of the bug in action :) Screenshot made on a MacBook Pro with an nVidia graphics chip, running Mac OS X 10.8.2 The second line of text is slightly purpler than the first line of text.

Mihai Balan

Comment 3 2013-03-08 07:21:23 PST

On further investigation of the PNG, it seems that the problem lies in the way anti-aliasing is done. In the case of the first line of text (that does not get a layer), anti-aliasing between blue and white is expectedly done via lighter, whiter blue. In the case of the second line of text, however (that gets a layer), anti-aliasing between blue and white is done via a lighter, *redder* blue.

Mihai Balan

Comment 4 2013-03-08 07:22:26 PST

Created attachment 192225 [details] Magnified shot of the bug Magnified shot of the bug. The anti-alias difference are obvious here. The "main" color of the text does not change between the two lines of text.

Alexey Proskuryakov

Comment 5 2013-03-08 10:01:36 PST

That sounds like bug 23364.

Mihai Balan

Comment 6 2013-03-08 10:31:52 PST

While the two do sound similar, I'm not convinced this is a dupe of bug 23364. Bug 23364 is about anti-aliasing going on and off, this one is about anti-aliasing being done differently. Also, it seems to be specific to some (hardware) configurations.

Simon Fraser (smfr)

Comment 7 2013-03-08 10:49:25 PST

This is not bug 23364 but it is a known issue in the frameworks below WebKit.

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