[csswg-drafts] [web-animations-1] Consider allowing seeking currentTime from resolved to unresolved (#4323)

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

== [web-animations-1] Consider allowing seeking currentTime from resolved to unresolved ==
[web-animations section 4.4.5](https://drafts.csswg.org/web-animations/#setting-the-current-time-of-an-animation) of the spec says that:
1. If *seek time is an unresolved time value*, then perform the following steps.
    1. If the *current time is resolved*, then throw a *TypeError*

In the ScrollTimeline spec, [scroll-animations section 3.1.4](https://wicg.github.io/scroll-animations/#current-time-algorithm) the current time can go from resolved to unresolved if the ScrollTimeline does not have `fill: both`. For the [ScrollTimeline polyfill](https://github.com/flackr/scroll-timeline), I [implemented this transition by canceling the animation](https://github.com/flackr/scroll-timeline/blob/master/scroll-timeline-base.js#L94)

```js
    if (currentTime == null) {
      if (animations[i].playState == 'paused')
        animations[i].cancel();
    } else {
      animations[i].currentTime = currentTime;
    }
```

However, if transitioning from resolved to unresolved is expected behavior, I think that we should allow seeking to unresolved time values. Of course, doing so may be equivalent to canceling the animation?

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/4323 using your GitHub account

Received on Tuesday, 17 September 2019 13:59:28 UTC