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Re: [css3-animation] keyframes and percentages

From: Øyvind Stenhaug <oyvinds@opera.com>
Date: Wed, 10 Oct 2012 14:21:59 +0200
To: "Glenn Adams" <glenn@skynav.com>
Cc: www-style@w3.org
Message-ID: <op.wlypyx10bunlto@oyvinds-desktop>
On Wed, 10 Oct 2012 04:20:59 +0200, Glenn Adams <glenn@skynav.com> wrote:

> keep in mind that
>
> -20%, 20% { top: 10px; animation-timing-function: ease-out; }
>
> should not ignore the 20% keyframe, but ignore the -20% keyframe

I dont' think this follows from the current editor's draft, or at the very  
least it's not at all clear.
"The keyframe selector for a keyframe style rule consists of a  
comma-separated list of percentage values or the keywords ‘from’ or ‘to’"
"If a keyframe selector specifies negative percentage values or values  
higher than 100%, then the keyframe will be ignored."
I read that as saying that if the comma-separated list contains negative  
percentage values or values >100%, the entire rule (selector + block) is  
ignored. I suppose it's possible to read it differently.

For consistency with regular declaration blocks, I think it would probably  
make the most sense if percentage values outside the interval [0%, 100%]  
were treated as invalid and caused the entire thing to be dropped, similar  
to the way ":first-child, :foo { top: 10px; }" gets dropped. This is what  
the ED seems to imply to me, but as mentioned it's not very clear.

The alternative you describe, which also seems to be the approach taken by  
Firefox, doesn't seem quite so consistent, but I suppose it's not too bad.  
It would basically be like "div, foo { top: 10px; }" where it's somehow  
known that a document can never contain any elements of type "foo".

> also, note the CSS2.1 Errata s.4.3.1 [1]

Thanks, but this doesn't affect the syntax chapter. Looks like it should  
have, though, as pointed out in the replies to  
<http://lists.w3.org/Archives/Public/www-style/2012May/0727.html>.

-- 
Øyvind Stenhaug
Core Norway, Opera Software ASA
Received on Wednesday, 10 October 2012 12:22:32 GMT

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