Re: [web-animations] Updating the finish promise in a separate task

On Tue, Jun 30, 2015 at 3:59 PM Brian Birtles <bbirtles@mozilla.com> wrote:

> On 2015/06/30 13:21, Brian Birtles wrote:
> > Hi,
> >
> > I'm currently speccing finish/cancel events for animations and I think
> > it makes sense to dispatch finish events and also update the finished
> > promise in a separate task.
>
> I was thinking of applying similar handling to the cancel event
> including the part where we cancel a pending finished promise.
>
> However, a consequence of this handling is it means that in the
> following case:
>
>    anim.finish();
>    anim.currentTime = 0;
>
> the finished promise won't resolve. Nor will any finish event fire.
>
> Likewise, if you say:
>
>    anim.finish();
>    anim.cancel();
>    anim.currentTime = 0;
>
> The finished promise won't fulfill or reject. Nor will the finish or
> cancel event fire.
>
> Is that weird?
>
> I wonder if we the following behavior is more intuitive:
>
> 1. cancel() queues event dispatch / promise rejection synchronously
>     such that calling cancel() always triggers a cancel event unless
>     the animation is already idle.
>
> 2. finish() likewise queues event dispatch / promise resolution
>     synchronously unlike simply setting the currentTime.
>

This synchronous queuing behavior for finish/cancel seems reasonable.


> (3. A timeline going inactive should cause us to update the hold time
>      of any animation watching it. This is consistent with what happens
>      when we set animation.timeline = null and means the only time we
>      ever transition to the idle state is from a call to cancel().)
>

+1


>
> Best regards,
>
> Brian
>
>