RESOLVED FIXED 104724
Pre-painting should not paint out-of-view fixed position elements 
https://bugs.webkit.org/show_bug.cgi?id=104724
Summary Pre-painting should not paint out-of-view fixed position elements
Xianzhu Wang
Reported 2012-12-11 14:59:34 PST
Out-of-view fixed position elements are not composited. In RenderLayer::paintLayer(), such elements will be painted when pre-paint out-of-view parts. This causes residues when the part scrolls into the viewport. Patch of bug 102543 provides a way to determine if a non-composited fixed position element is out-of-view so not to be painted in pre-paining.
Attachments
Patch (5.79 KB, patch)
2012-12-11 21:28 PST, Xianzhu Wang 		no flags
DetailsFormatted DiffDiff
Use manual test (3.71 KB, patch)
2012-12-12 10:58 PST, Xianzhu Wang 		no flags
DetailsFormatted DiffDiff
Show Obsolete (1) View All Add attachment proposed patch, testcase, etc.
James Robinson
Comment 1 2012-12-11 19:22:34 PST
I see the same bug in Safari running a WebKit nightly
James Robinson
Comment 2 2012-12-11 19:26:14 PST
For instance load up http://software.hixie.ch/utilities/js/live-dom-viewer/saved/2012, click "Rendered view", and scroll down. I see lots of red on Version 6.0.2 (8536.26.17, 537+) WebKit r137338
Simon Fraser (smfr)
Comment 3 2012-12-11 19:52:38 PST
Not sure what pre-painting is.
James Robinson
Comment 4 2012-12-11 20:46:51 PST
Painting things not currently in the visible viewport. On mac, I think this is done via the tile caching logic.
Xianzhu Wang
Comment 5 2012-12-11 21:28:01 PST
Created attachment 178958 [details] Patch
Xianzhu Wang
Comment 6 2012-12-11 21:31:04 PST
Actually I didn't reproduce the issue with the added test case when the fix was not applied. I wonder what the correct way is to test prepainting behavior.
James Robinson
Comment 7 2012-12-11 22:14:23 PST
The scroll will generate an invalidation before the test completes. I don't know of any way to see the results of off-main-thread scrolling in a layout test.
Beth Dakin
Comment 8 2012-12-11 22:17:29 PST
(In reply to comment #0) > Out-of-view fixed position elements are not composited. In RenderLayer::paintLayer(), such elements will be painted when pre-paint out-of-view parts. This causes residues when the part scrolls into the viewport. Patch of bug 102543 provides a way to determine if a non-composited fixed position element is out-of-view so not to be painted in pre-paining. Can you provide a manual test that reproduces this bug? I am just curious to see it.
James Robinson
Comment 9 2012-12-11 22:27:17 PST
(In reply to comment #8) > (In reply to comment #0) > > Out-of-view fixed position elements are not composited. In RenderLayer::paintLayer(), such elements will be painted when pre-paint out-of-view parts. This causes residues when the part scrolls into the viewport. Patch of bug 102543 provides a way to determine if a non-composited fixed position element is out-of-view so not to be painted in pre-paining. > > Can you provide a manual test that reproduces this bug? I am just curious to see it. See comment #2
Beth Dakin
Comment 10 2012-12-11 22:31:58 PST
(In reply to comment #9) > (In reply to comment #8) > > (In reply to comment #0) > > > Out-of-view fixed position elements are not composited. In RenderLayer::paintLayer(), such elements will be painted when pre-paint out-of-view parts. This causes residues when the part scrolls into the viewport. Patch of bug 102543 provides a way to determine if a non-composited fixed position element is out-of-view so not to be painted in pre-paining. > > > > Can you provide a manual test that reproduces this bug? I am just curious to see it. > > See comment #2 Thanks!
Xianzhu Wang
Comment 11 2012-12-12 10:58:18 PST
Created attachment 179082 [details] Use manual test
James Robinson
Comment 12 2012-12-12 11:02:04 PST
Comment on attachment 179082 [details] Use manual test R=me
WebKit Review Bot
Comment 13 2012-12-12 11:39:16 PST
Comment on attachment 179082 [details] Use manual test Clearing flags on attachment: 179082 Committed r137492: <http://trac.webkit.org/changeset/137492>
WebKit Review Bot
Comment 14 2012-12-12 11:39:20 PST
All reviewed patches have been landed. Closing bug.
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