[csswg-drafts] [scroll-animation] Define when `ScrollTimeline.source` should update (#13480)

dshin-moz has just created a new issue for https://github.com/w3c/csswg-drafts:

== [scroll-animation] Define when `ScrollTimeline.source` should update ==
Given this testcase: [scroll-timeline.html](https://github.com/user-attachments/files/25218711/scroll-timeline.html)

On clicking the "Change" button, it changes the animation scroller from `#outer` to  to `#inner`.
Corresponding `timeline.source` updates as well on WebKit/Blink. However, the timing differs slightly:

* On WebKit, the change is reflected after rAF.
* On Blink, the change is reflected immediately afterwards, before rAF.

Should the change be reflected synchronously or asynchronously?

(cc @emilio @BorisChiou @jwatt)

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/13480 using your GitHub account


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Received on Tuesday, 10 February 2026 19:33:43 UTC