778000 - Nested fixed-pos elements probably don't scroll properly with async scrolling

Status: NEW

(Core :: Layout: Scrolling and Overflow, defect)

Description

[Robert O'Callahan (:roc) (email my personal email if necessary)]

While rebasing the patch in bug 769541 to Aurora, I discovered a problem. In nested fixed-pos elements we suppress nsDisplayPositionFixed for the inner item and keep the outer item. This means the metadata attached to the layer will be for the outer fixed-pos element, not the inner one. This seems wrong. We may be able to fix this just by adjusting the fixed-pos frame we pass to the outer nsDisplayPositionFixed. We should probably fix this, although it's not super-important since I suspect nested fixed-pos elements are rare.

Comment 1

[Timothy Nikkel (:tnikkel)]

The code involved here has probably changed a lot since this bug was filed so I wouldn't be surprised if this is fixed.