Bug 61124 – Webkit mismanages scrollHeight on elements with overflow: hidden and position:fixed

• Status: UNCONFIRMED
• Component: New Bugs

[Aimee Ault]

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).