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Re: [css3-animations] Possible spec bug?

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Sun, 30 Oct 2011 16:52:36 -0700
Message-ID: <CAAWBYDBdcSSFk186mN84OnKWgQu+Db-U24uByu1y_80t1-Zh8A@mail.gmail.com>
To: Lea Verou <leaverou@gmail.com>
Cc: www-style list <www-style@w3.org>
On Sat, Oct 29, 2011 at 2:02 PM, Lea Verou <leaverou@gmail.com> wrote:
> Check this out: http://jsfiddle.net/leaverou/jwHva/2/
>
> If you remove border-style: solid; from the div {...} rule, the animation
> stops having a visible effect, even though both the interpolated values
> contain border-style:solid; (in the shorthand). This doesn't change even
> with animation-fill-mode: both; It happens in both Webkit and Mozilla, so
> it's probably not a browser bug.
>
> I discussed it with David Baron on IRC and his explanation was this:
> dbaron: I think it may be because each property in the animation gets
> handled separately
> dbaron: on top of the base values
> dbaron: and with a 'none' border style the border-width doesn't do anything
> leaverou: but I defined border-style in the animation, through the shorthand
> dbaron: I doubt the spec is clear on this point, though.
> dbaron: yeah
> dbaron: my guess (haven't checked yet)
> dbaron: is that despite that, the border-width computes to zero in the
> animation
>
> I took a look at the spec, but couldn't find anything relevant.
> I think it's very confusing behavior and potentially a spec bug, so thought
> I'd let you guys know.

David's likely right.  If the three subproperties are resolved and
animated independently, then border-width computes to 0 for the start
and end, because the base value (ignoring other properties the
animation may change) of border-style is 'none'.  Thus, no animation
happens to the property.

That's *really* unexpected, though.  Maybe we should specify that the
0% and 100% keyframes are fully applied, rather than being done
individually.

~TJ
Received on Sunday, 30 October 2011 23:53:34 GMT

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