Re: [csswg-drafts] [web-animations-1][scroll-animations-1] Animations on inactive timelines should still become ready (#9256)

Getting stuck waiting on the ready promise feels off in the null timeline case as well, when the animation is frozen at currentTime 0 waiting (possibly indefinitely) on a resolved timeline with a timeline time.  (see https://github.com/w3c/csswg-drafts/issues/13817).

If the ready promise can resolve before the timeline is active, we can be left in an awkward position in calculating playState. If holdTime and startTime are both unresolved, and not pending(), then the animation would be considered idle. Naturally, this could be resolved by adding a new state, or forcing a start time (still not in effect if timeline.currentTime is unresolved).   

Once playing, there is no issue with the timeline becoming inactive and then active again due to the scroll range disappearing and reappearing.   What differs here is that when the timeline becomes inactive, we can maintain that we are still playing but not in effect, because we have a value for startTime. Methinks we can apply a sensible start time when the timeline is inactive, provided the animation is set to auto-align its start time as the scroll range changes.  Playing an animation currently sets auto-alignment for scroll based animations.




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Received on Friday, 1 May 2026 19:14:59 UTC