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more transitionend events (was Re: when do transitions occur?)

From: L. David Baron <dbaron@dbaron.org>
Date: Wed, 21 Sep 2011 13:29:51 -0700
To: Dean Jackson <dino@apple.com>
Cc: Jennifer Yu <Jennifer.Yu@microsoft.com>, Brian Manthos <brianman@microsoft.com>, "Tab Atkins Jr." <jackalmage@gmail.com>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <20110921202951.GA11935@pickering.dbaron.org>
On Thursday 2011-09-22 06:17 +1000, Dean Jackson wrote:
> On 16/09/2011, at 6:37 AM, Jennifer Yu wrote:
> > Thanks for the responses Tab and David. I didn't realize that shorthands don't have a computed value since getComputedStyle seems to return a valid string for shorthands.
> > 
> > And just for clarification regarding zero duration transitions and animations (since I seem to have trouble finding the previous discussion of it), 0 duration transitions should not throw events if the delay is also 0. If the delay is positive, 0 duration transitions should throw an event. 0 duration animations, on the other hand, should throw events. Are those statements accurate?
> We get a *LOT* of requests from developers asking for transitionend events to fire all the time, even if the property didn't change. This could be a 0/0 duration delay, or setting a property to the same value.
> The use case is generally wanting to run a bunch of animations on children before changing a parent. Think of something like a slide-show where the text might slide off the page before the transition to the next screen.
> Any opinions on this?
> We're concerned about performance impact. An alternative would be to write an API that allows you to query the current state of all transitions on an element (or subtree). That way you'd know what is active.

I'm not sure what it even means.  Transitions start when a computed
value changes; are you saying you'd introduce cases where
transitions occur even when a computed value doesn't change?

It sounds to me like the use case that these authors have is
probably best solved by a mechanism other than transitions, and one
that should be designed to be able to do what they want efficiently.


𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Wednesday, 21 September 2011 20:30:17 UTC

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