981708 - ScrollLayer Items not always grouped together depending on Z-index

Status: RESOLVED DUPLICATE of bug 967844

(Core :: Layout, defect, P1)

Description

[Mason Chang [Inactive] [:mchang]]

Based on bug 972675, scrolling breaks with APZ if we don't group ScrollLayer items together. The fix in bug 972675 was to fix the z-index so that ScrollLayer items became grouped together. This bug is to fix the platform so that ScrollLayer items are automatically grouped together and the app doesn't have to fiddle with z-indexes.

Comment 1

[Mason Chang [Inactive] [:mchang]]

Attachment: Paint Dump with Broken Scrollable Layer on Calendar App

Comment 2

[Timothy Nikkel (:tnikkel)]

So if we group together all scroll layer items we will be changing their stacking order (z indexes) from what the page specified. I don't think we can do that in general. The plan to fix this properly in the slightly longer term is to let the scrolled content go into separate layers and then scroll those layers together. Bug 967844 was filed to cover this, although it doesn't have many specifics yet. In the short term we will have to go with workarounds from content.

Comment 3

[Kartikaya Gupta (email:[e-mail])]

If there's no more pending changes in layout that can help here I'm just going to dupe this over to the longer-term fix and put some details there.