Bug 94795 – CSS3 repeating-linear-gradient rendering bug

• Component: CSS
• Status: NEW

[Binyamin]

CSS3 repeating-linear-gradient rendering bug - the stops should repeat every 3 pixels.
On different browser the same repeating-linear-gradient visual appearance are different.
The bug  refers also to Chrome Canary, Firefox Nightly, Opera Next, IE10.

Demo: http://jsfiddle.net/laukstein/K6XVw/2/
Referring to Firefox bug: https://bugzilla.mozilla.org/show_bug.cgi?id=644444#c23

[Martin Leutelt]

As far as I can tell this is not a bug in webkit but in qt itself. I've reported it here https://bugreports.qt-project.org/browse/QTBUG-27157.

[Binyamin]

(In reply to comment #1)
> As far as I can tell this is not a bug in webkit but in qt itself. I've reported it here https://bugreports.qt-project.org/browse/QTBUG-27157.

Robert O'Callahan from Mozilla relates it to Webkit bug too https://bugzilla.mozilla.org/show_bug.cgi?id=644444#c23

[Martin Leutelt]

Well, he says that Chrome doesn't render it correctly which is true but that doesn't necessarily mean that the bug is in webkit. Chrome uses different drawing libraries on different platforms. So if he tested with Chrome on Linux the bug could be in Skia. Firefox uses cairo to draw which is also used by the Gtk port of webkit. If you compare those two the result looks almost exactly the same which leads me to the conclusion that it most probably is a bug in the drawing library.

[Binyamin]

(In reply to comment #3)
> Well, he says that Chrome doesn't render it correctly which is true but that doesn't necessarily mean that the bug is in webkit.

Comparing latest Chrome Canary and Safari, the visual rendering bug appears on both browsers. And certainly Webkit currently is related to Chrome and Safari.

[Martin Leutelt]

Yes, both Chrome and Safari are using WebKit. But they are using different backends for drawing and it's very possible that those backends are buggy.
WebKitGtk uses the cairo library and seems to draw correctly or at least very similar to Firefox which also uses cairo. That makes me think that the values that WebKit passes to the drawing backends are correct.

At last for QtWebkit it looks like the bug is caused by Qt not drawing the gradient correctly.

[Jocelyn Turcotte]

=== Bulk closing of Qt bugs ===

If you believe that this bug report is still relevant for a non-Qt port of webkit.org, please re-open it and remove [Qt] from the summary.

If you believe that this is still an important QtWebKit bug, please fill a new report at https://bugreports.qt-project.org and add a link to this issue. See http://qt-project.org/wiki/ReportingBugsInQt for additional guidelines.

[Binyamin]

Created attachment 222998 [details]
Webkit vs Firefox

This bug is still relevant.
http://jsfiddle.net/laukstein/K6XVw/2/ and http://jsfiddle.net/laukstein/K6XVw/14/ must return visualy accurately same result, but doesn't.

[Brent Fulgham]

This is still an issue in Safari 15. (Note that Chrome and Firefox seem to do badly on these tests, too).

[Radar WebKit Bug Importer]

<rdar://problem/96961639>