1790131 - ResizeObserver timing doesn't match the spec.

Status: RESOLVED INVALID

(Core :: Layout, defect)

Description

[Emilio Cobos Álvarez (:emilio)]

See blocked bug. To summarize, ResizeObserver is triggered from:

• https://searchfox.org/mozilla-central/rev/31368c7795f44b7a15531d6c5e52dc97f82cf2d5/dom/base/ResizeObserverController.cpp#21

Which is called from:

• https://searchfox.org/mozilla-central/rev/31368c7795f44b7a15531d6c5e52dc97f82cf2d5/layout/base/nsRefreshDriver.cpp#2510

While rAF is triggered from:

• https://searchfox.org/mozilla-central/rev/31368c7795f44b7a15531d6c5e52dc97f82cf2d5/layout/base/nsRefreshDriver.cpp#2547

So I don't think Gecko right now is guaranteeing that ordering... I don't think this is too hard to fix.

Comment 1

[Emilio Cobos Álvarez (:emilio)]

Ah, I actually was misreading the code, the ResizeObserver controller gets added as a Display refresh driver observer, so it should match the spec ordering. Might be better to make it more explicit (and e.g., the intersection observer steps right now run after ResizeObserver), but I don't think it's a correctness issue anymore.