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[css3-animations] Transitions on moving targets (was Re: Override of animation rule by !important)

From: L. David Baron <dbaron@dbaron.org>
Date: Sun, 29 Jan 2012 02:19:33 +0100
To: Jon Rimmer <jon.rimmer@gmail.com>
Cc: Sylvain Galineau <sylvaing@microsoft.com>, "www-style@w3.org" <www-style@w3.org>
Message-ID: <20120129011933.GA12964@pickering.dbaron.org>
[ In the future, when you change the subject of a thread, please
  change the Subject: header of your message.  I've done that. ]

[ Also, writing this on board an airplane, so apologies if the
  discussion has already covered this by the time I land. ]

On Friday 2012-01-20 17:06 +0000, Jon Rimmer wrote:
> For both animations and transitions, at any instant, we have a base
> property value, a target property value, and an interpolation function
> that produces an intermediate value based on the duration and the
> easing. All we need is a simple pipeline, where the instantaneous,
> intermediate value from the animation is fed as the base value into
> the interpolation function of the transition.

I think this doesn't make sense with transitions as they are today
because of the mechanism with which transitions start:  they start
in response to changes in computed values.  If there's another
animation running (a moving target), the computed value is
constantly changing.  If transitions, initiated today via
'transition-property', started in response to changes in computed
value caused by other animations it would only serve to damp those
animations in bizarre ways.  And since the model of transitions that
happen based on 'transition-property' is based on computed values,
it's not clear how a change in the value "underneath" the animation
would start an animation since that change would not be reflected in
the computed value.

However, if we had an API to initiate a one-off transition (which I
think would probably be a good idea), I think the concept you're
talking about might make more sense.

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                           http://www.mozilla.org/   𝄂
Received on Sunday, 29 January 2012 13:00:56 GMT

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