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Re: [css-round-display] Decision about if polar-angle turns into an angle or a keyword in the computed value

From: Jihye Hong <jh.hong@lge.com>
Date: Mon, 21 Dec 2015 11:14:40 +0900
To: <www-style@w3.org>, "'fantasai'" <fantasai.lists@inkedblade.net>, "'L. David Baron'" <dbaron@dbaron.org>
Cc: "'Brad Kemper'" <brad.kemper@gmail.com>, "'Florian Rivoal'" <florian@rivoal.net>
Message-ID: <000a01d13b95$5a8ef820$0face860$@hong@lge.com>
Depending on fantasai's mention [1] in the last Telecon, I understood how
the animation using rotate(polar-angle) works like below:

  If the keyword value remains as a keyword, you can't animate between it
and another angle value.
  For example, animating between rotate(polar-angle) and rotate(0deg) isn't
  However, when polar-angle property animates, the changes in it affect to
the rotation function with the keyword value.

  If the keyword value turns into an angle, you can animate between it and a
different angle.
  Thus you can animate between rotate(polar-angle) and rotate(0deg) or
between rotate(polar-angle) and rotate(polar-angle-reverse).
  But if polar-angle property animates, the rotation animation with the
keyword value will not track the changes in polar-angle property.

Did I understand right?
If I did, I'm curious about the mechanics.

When the polar-angle value remains as a keyword, animating between it and
another angle value isn't possible. Is it because it cannot be interpolated
with different type of computed value?

And when the polar-angle value turns into angle value and polar-angle
property and rotate(polar-angle) animate, why the rotation animation cannot
track the changes in polar-angle?

In case of 'currentColor'[2] which computed value is the computed value of
the color property,
when I give currentColor for the border-color property, and animate the
color property, currentColor tracks changes in color animation. 
And it was possible to animate border-color property from currentColor and
another color value.

> On Dec 18, 2015, at 15:13, Brad Kemper <brad.kemper@gmail.com> wrote:
>> On Dec 7, 2015, at 6:57 PM, Florian Rivoal <florian@rivoal.net> wrote:
>>> It's a shame that we can't just animate the used values to do that, so
that we could have our cake and eat it too, but it's the same situation with
trying to animate from/to height:auto, I guess. 
>> That seems different, because you cannot resolve height:auto at computed
value time.  But the rotate(polar-angle)'s relationship with the polar angle
property *can* be done at computed value time.
>> Or can it not? Am I misunderstanding how computed values and animations

> I'm not sure. Maybe I am misunderstanding. I was inferring from the
discussion that it was something like that.

[1] http://log.csswg.org/irc.w3.org/css/2015-12-02/#e625737
[2] http://www.w3.org/TR/css3-color/#currentcolor

Jihye Hong
Received on Monday, 21 December 2015 02:15:21 UTC

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