1096181 - Descendants of scrollable elements with 'perspective' get incorrect overflow areas when the scroll position changes

Status: RESOLVED FIXED

(Core :: Layout, defect)

Description

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

The transform on the child of a scrollable element with 'perspective' may be dependent on the scroll position. When the element is scrolled, the transform may need to be updated, but it isn't.

Comment 1

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

Attachment: Recompute overflow areas of transformeparent element with perspective is scrolled

Comment 2

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

Actually there's an edge case not handled here: updating the overflow areas of the descendants could cause the overflow area of the scrolled frame to shrink, which we're not handling. And that could change the scroll position so I think there's actually a dependency loop in CSS :-(

But we probably should check this in anyway.

Comment 3

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

https://hg.mozilla.org/integration/mozilla-inbound/rev/9906eabbfd3a

Comment 4

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/9906eabbfd3a

Comment 5

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

Comment on attachment 8519760 [details] [diff] [review]
Recompute overflow areas of transformeparent element with perspective is scrolled

Approval Request Comment
[Feature/regressing bug #]: none
[User impact if declined]: incorrect rendering when scrolling in certain sites that use preserve-3d
[Describe test coverage new/current, TBPL]: some automated tests
[Risks and why]: I was contacted by a Web developer who's hitting this bug in the wild. The patch is very low risk so getting a fix out six weeks earlier would be good.
[String/UUID change made/needed]: none

Comment 6

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

I just landed the **reftest manifest changes only** from this bug on aurora and beta, because those changes actually belonged in either bug 1097437 or bug 1092842, which were just landed in both places:

https://hg.mozilla.org/releases/mozilla-aurora/rev/187e9fa68b67
https://hg.mozilla.org/releases/mozilla-beta/rev/c486cd17bebb

Comment 7

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/5087cbbab5b2