[Webkit-unassigned] [Bug 61124] New: Webkit mismanages scrollHeight on elements with overflow: hidden and position:fixed

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=61124

           Summary: Webkit mismanages scrollHeight on elements with
                    overflow: hidden and position:fixed
           Product: WebKit
           Version: 525.x (Safari 3.2)
          Platform: Unspecified
               URL: http://jsfiddle.net/XWrnw/
        OS/Version: Unspecified
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: New Bugs
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: aimee at writography.net


Steps to reproduce:

0. Visit: http://jsfiddle.net/XWrnw/
1. Scroll down until the scrollbar has reached the very bottom.
2. Hover over "Stuff 8." A red box should appear. This shifts "Stuff 9" out of scrollable view, which may be part of the bug, but overall, the transition feels smooth.
3. Scroll all the way back to the top, not hovering over any of the sidebar elements.
4. Scroll all the way back to the bottom until the scrollbar has reached the very bottom.
5. Now hover over "Stuff 7." The content will shift both up and down, as though webkit is trying to rerender content. It will feel "jumpy." 

I can only reproduce it once per page load. After it happens initially, the browser seems to figure out how to handle it in all future attempts.

This doesn't happen in Firefox, Internet Explorer, or Opera, only Safari and Chrome, so I'm assuming after much frustration that it's a browser engine problem since it only happens in Safari or Chrome. The problem, I think, being tht webkit is not correctly determining either the element's scrollHeight, not compensating for repositioned elements in this odd mixture of overflow:hidden/position:fixed (only seems to happen under that very particular scenario, can't reproduce with position: absolute or overflow:auto,overflow:visible).

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