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Re: [css3-transitions] faster reversing of partially completed transitions

From: L. David Baron <dbaron@dbaron.org>
Date: Mon, 28 Dec 2009 16:48:19 -0500
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style <www-style@w3.org>
Message-ID: <20091228214819.GA13349@pickering.dbaron.org>
On Monday 2009-12-28 13:31 -0600, Tab Atkins Jr. wrote:
> On Mon, Dec 28, 2009 at 12:43 PM, L. David Baron <dbaron@dbaron.org> wrote:
> >> (2) jump to the point in the timing function (at the specified
> >>     transition-duration) for the reverse transition that would have
> >>     the element at its current position (and thus ignore
> >>     transition-delay entirely)
> >
> > I tried implementing this, and it also looked horrible (due to
> > unexpected jumpiness).
> 
> I'm curious about this.  Can you describe the jumpiness?  It doesn't
> seem like anything should jump at all; is it that perhaps the element
> changes velocity (not counting the reversal itself) in a possibly
> discontinuous manner?  That is, with a transition that is ease-in both
> ways, if you reversed it near the beginning of the transition it would
> change from transitioning quickly (the start of an ease-in transition)
> to transitioning slowly in reverse (the end of an ease-in transition).

Yes, it was just unexpected velocity changes: in particular, quick
starts to movement for transitions that are 'ease-in-out' or
'ease-in' seem unexpected.  (Try, for example, mousing in and out on
http://dbaron.org/css/test/2009/transitions/transition-timing-functions .)

Perhaps it's not that horrible, though.

In any case, demo builds with the code this way are at:
https://build.mozilla.org/tryserver-builds/dbaron@mozilla.com-try-9d113f7acb59/
(The Mac build isn't quite done yet, but should be there shortly.)
Please do NOT use this as your main Firefox build; it will never
auto-update so you'll be stuck with a random nightly.

For the record, this build consists of the source in:
http://hg.mozilla.org/mozilla-central/file/699d0367eccf
Plus these two patches:
http://hg.mozilla.org/users/dbaron_mozilla.com/patches/raw-file/c44094e6c49c/transitions-division-crash
(a patch that the next patch happened to be written on top of)
http://hg.mozilla.org/users/dbaron_mozilla.com/patches/raw-file/fa6b2c782a68/transition-no-compute-distance
(the patch that actually implements the behavior in question).

-David

-- 
L. David Baron                                 http://dbaron.org/
Mozilla Corporation                       http://www.mozilla.com/
Received on Monday, 28 December 2009 21:48:51 GMT

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