[Webkit-unassigned] [Bug 126267] New: -webkit-backface-visibility: hidden on <html> element can cause portions of the screen not to update

Fri Dec 27 15:23:35 PST 2013

https://bugs.webkit.org/show_bug.cgi?id=126267

           Summary: -webkit-backface-visibility: hidden on <html> element
                    can cause portions of the screen not to update
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Layout and Rendering
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: geoff.benson at ecofactor.com

This bug is best seen with a minimal demonstration page, which I have attached.

How to reproduce:
* Apply this style declaration:
html {
  -webkit-backface-visibility: hidden;
}

* After the page has loaded, change the styling on the <body> tag dynamically via JavaScript, for example by setting the background-color to something new.

Expected behavior:
The body style should be applied, and the viewport should redraw to show the applied style.

Actual behavior:
Only portions of the page get updated.  This bug was found when researching why only parts of the screen were rendered with a new background image when a style was applied to <body> (the parts of the screen which didn't get new elements added remained black, per the <body>'s previous style at the time.)

Additional:
If the time between initial render and when the <body> style is changed is small enough (1ms or less), the bug doesn't trigger.

This has been reproduced on the following environments:

MacOS: Safari 7.0.1, Chrome 31.0.1650.63, Opera Next 19.0.1326.21
Windows 7: Chrome 31.0.1650.63 m
Android: 4.3, 4.0, 2.3.5 (though 2.3.5 has additional rendering bugs related to this). 
iOS: 7.0.4

Workaround:
If the -webkit-backface-visibility style is applied to <body> instead of <html>, this bug is not triggered.

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