Re: [csswg-drafts] [css-animations-2] Alternate animation composite order when owning element of A and B differs (#4669)

> [CSS transitions](https://drafts.csswg.org/css-transitions/#starting) has:
> 
> > Since this specification does not define when a style change event occurs, and thus what changes to computed values are considered simultaneous, authors should be aware that changing any of the transition properties a small amount of time after making a change that might transition can result in behavior that varies between implementations, since the changes might be considered simultaneous in some implementations but not others.
> 
> My concern is that while differences in the timing of transitions being triggered is unfortunate, unless they actually lead to a difference in the set of events being fired (which they _could_, but won't always), they're unlikely to cause catastrophic failure. Returning the animations in a different order, however, is more likely to.

I see, tree order gives you eventual consistency (assuming the same set of eventually running animations) so as long as you retrieve an animation after they are all guaranteed to be running it will be consistent.

> > When I discussed this with some style folks on blink they figured that interop incompatibilities about when style changes occurred would likely cause lots of interop issues. Maybe it's reasonable to try to achieve interop on when style changes should occur (at least with respect to developer APIs).
> 
> Yes, that sounds good. I'm a little unsure how practical it is, though, since we'd need to define whether each DOM API flushes style and under what circumstances. We do that for some Web Animations APIs but most specs don't.

I'm not convinced that outside of toy cases (where the two strategies will yield interoperable lists) it will be practical to assume a static index for specific animations (given animations / transitions may start, css files load, etc), however I agree we should have a consistent ordering and tree ordering does sound like it may be consistent a bit more often than creation time.

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Received on Wednesday, 15 January 2020 16:00:48 UTC