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Re: [web-animations] Significant changes to Web Animations coming up

From: Shane Stephens <shans@google.com>
Date: Thu, 12 Mar 2015 01:10:04 +0000
Message-ID: <CAGTfzwTqddF=eoF2OL_RDmjD9=Lki2hkNiJ-WTW6vFO_nMM9aA@mail.gmail.com>
To: Brian Birtles <bbirtles@mozilla.com>, "public-fx@w3.org" <public-fx@w3.org>
>
>
> Unfortunately I was unable to make a shared keyframe list since as was
> discussed at one stage.[3] This is because keyframe lists return their
> computed offsets but for paced keyframe lists, the computed offset may
> depend on their target element in order to resolve percentage values,
> for example. This is problem exists with the API regardless of this
> change so we can address it subsequently (e.g. by making the computed
> keyframe list getter take a target element).
>

I am very concerned by this.

Our implementation demonstrates that parsing of keyframe lists is a major
cost, possibly the largest cost involved in setting up animations. Sharing
keyframe lists where possible would be a major benefit.

Furthermore, keyframe lists should only deal with specified lists - the
problem you're describing doesn't need to exist as accessors on a
KeyframeList should return the unmodified inputs.

It's fine to keep a getFrames method on the KeyframeEffect object for
accessing the computed result (in a place where the target is known) -
although I think this could be deferred to a later level as we don't have
currently have strong use cases for it.

Sincerely,
    -Shane Stephens
Received on Thursday, 12 March 2015 01:10:31 UTC

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