[Webkit-unassigned] [Bug 48017] New: Incorrect scrolling behavior with the compositor and position: fixed elements

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=48017

           Summary: Incorrect scrolling behavior with the compositor and
                    position: fixed elements
           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: mihaip at chromium.org
                CC: simon.fraser at apple.com, vangelis at chromium.org


Created an attachment (id=71350)
 --> (https://bugs.webkit.org/attachment.cgi?id=71350&action=review)
Test case

Load the attached test case. Scroll the page.

Expected behavior: nothing scrolls, since the content is an position: fixed element.

Actual behavior: The gray rectangle stays put, but the text around it scrolls.

This is triggered by -webkit-transform: translateZ(0px) property on the gray element, hence the suspicion that the compositor is involved.

This is a reduction of http://crbug.com/58982, which is a bug that affects twitter.com. This is not a recent WebKit regression (happens with Safari 5.0.2), but only started to happen with Chrome 8 (where I believe we enabled the compositor for the first time).

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