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[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, 7 Dec 2015 17:41:19 +0900
To: "'www-style list'" <www-style@w3.org>
Message-ID: <001101d130cb$0b1d77f0$215867d0$@hong@lge.com>
Recently, the extension of the 2d rotation was added to the CSS Round
Display [1]. 
Keyword values, polar-angle and polar-angle-reverse can be the value for the
2d rotate function. But it's not clear whether the keyword value turns into
an angle or remain as a keyword when determining the computed value of
transform.

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: 0 isn't
possible.
 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: 0 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.

When suggesting polar-angle and polar-angle-reverse as keyword values for 2d
rotation transform function, the main goal of those value is to rotate the
element toward the origin point whatever the position of the element is in
polar coordinates.

Therefore, the keyword value should remain as a keyword at computed value
time.
Maybe there are some needs for animating between polar-angle and a different
angle, but I think tracking the changes in polar-angle property when
animating rotation function with polar-angle is more important than that
case.

Thanks,
Jihye Hong

[1]
https://drafts.csswg.org/css-round-display/#2d-rotation-transform-function
Received on Monday, 7 December 2015 08:41:54 UTC

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