Bug 17997

Summary: Full Page Zoom: Artifacts in background images on mooseyard.com
Product: WebKit Reporter: Frederik De Bleser <frederik>
Component: Layout and RenderingAssignee: Dave Hyatt <hyatt>
Status: RESOLVED FIXED    
Severity: Minor CC: ddkilzer, hyatt, marc
Priority: P2    
Version: 528+ (Nightly build)   
Hardware: Macintosh   
OS: OS X 10.5   
URL: http://mooseyard.com/Jens/
Attachments:
Description Flags
Screenshot of the site showing tearing artefacts
none
This is a workaround patch. Just recording it.
none
Patch sullivan: review+

Description Frederik De Bleser 2008-03-21 17:26:41 PDT
Using the new full page zoom feature in Webkit r31201, zooming twice on the page http://mooseyard.com/Jens/ (command-+ command-+) shows tearing artefacts between repeating background images, manifested as black lines. See the screenshot for details.

Note that this happens only at some zoom levels, notably zoomed in twice and five times. Zooming out also results in artefacts.
Comment 1 Frederik De Bleser 2008-03-21 17:27:21 PDT
Created attachment 19947 [details]
Screenshot of the site showing tearing artefacts
Comment 2 Dave Hyatt 2008-03-21 23:28:09 PDT
*** Bug 18003 has been marked as a duplicate of this bug. ***
Comment 3 Dave Hyatt 2008-03-21 23:28:52 PDT
*** Bug 17999 has been marked as a duplicate of this bug. ***
Comment 4 Dave Hyatt 2008-03-21 23:29:32 PDT
This bug appears to be Leopard-only, and it's an issue with

CGContextDrawTiledImage

The old Tiger code path (although slower) seems to be correct.
Comment 5 Dave Hyatt 2008-03-21 23:47:10 PDT
I can actually work around this, but it would mean taking the slow code path (and I think it would hurt performance way too much for zoomed pages to do this).

Comment 6 Dave Hyatt 2008-03-24 19:41:37 PDT
Created attachment 20018 [details]
This is a workaround patch.  Just recording it.
Comment 7 Dave Hyatt 2008-11-11 11:28:48 PST
Created attachment 25047 [details]
Patch
Comment 8 John Sullivan 2008-11-11 11:41:56 PST
Comment on attachment 25047 [details]
Patch

Do you also want to check PLATFORM(MAC) anywhere? I see the existing #ifndef BUILDING_ON_TIGER does not do so, but maybe it should?

John
Comment 9 Dave Hyatt 2008-11-11 11:51:56 PST
Fixed in r38309.

Good question about PLATFORM(MAC).  It depends on what version of CG ends up
shipping with the next version of Safari on Windows whether or not the
workaround will be needed for Windows.