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Re: [csswg-drafts] [css-transitions] transitionstart definition does not match Edge behavior

From: Brian Birtles via GitHub <sysbot+gh@w3.org>
Date: Wed, 24 Aug 2016 00:13:15 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-241921399-1471997593-sysbot+gh@w3.org>
Yes, that's right. We're implementing this in Firefox at the moment 
hence we want to clarify this. There's a bug on file for Chrome, but 
no activity yet. I mentioned it to a couple of friends at Google 
earlier this week so I suspect they'll pick it up soon.

If Edge are prepared to change their implementation to match the 
current spec behavior we'll stick with that, otherwise we might need a
 new event.

For what it's worth, the particular use case I have in mind is that 
when we were working on Firefox OS apps we often wanted to wait until 
transitions had finished before updating some piece of state. However,
 in some situations transitions would get cancelled such as when a DOM
 subtree gets replaced (i.e. "rendered" if you're using a framework 
like react). As a result the `transitionend` event would never fire. 
Instead, we'd often end up setting timeouts to run in case the 
transition got cancelled. The 
[`transitioncancel`](https://drafts.csswg.org/css-transitions-2/#eventdef-transitionevent-transitioncancel)
 event is supposed to help with that but there are still situations 
where you might not get a transition to begin with, e.g. if you update
 style but the new style values happen to match the old ones, so you 
still might find you're waiting for an event that never comes. Having 
an event that fires when a new transition is triggered would let you 
know that you need to wait for either `transitionend` or 
`transitioncancel` (and you are guaranteed to get exactly one of 
those).

(And, completely unrelated, but _thank you_ so much for all your work 
on PouchDB! I've been poring over PouchDB code recently for a 
PouchDB-based hobby project I'm working on and really appreciate all 
you've done. Thank you!)

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Received on Wednesday, 24 August 2016 00:13:23 UTC

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