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Re: [CSS Transitions] Review comments on Editor's Draft Feb 10, 2009

From: Erik Dahlström <ed@opera.com>
Date: Mon, 02 Mar 2009 09:02:06 +0100
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: "www-style@w3.org" <www-style@w3.org>, www-svg <www-svg@w3.org>
Message-ID: <op.up5m9sdtdhsuf5@gnorps.linkoping.osa>
On Fri, 27 Feb 2009 18:07:59 +0100, Tab Atkins Jr. <jackalmage@gmail.com> wrote:

> On Fri, Feb 27, 2009 at 2:54 AM, Erik Dahlström <ed@opera.com> wrote:
>> == 2.1 The ‘transition-property’ Property ==
>>
>> What happens when there's a mismatch between the number of 'transition-property' values and the number of 'transition-duration' values?
>
> Hmm, I don't see it directly in that draft, but it has been brought up
> before that in the case of mismatched argument lengths, the shorter
> lists cycle.  So the following:
>
> transition-property: opacity, color, left;
> transition-duration: 1s, 2s;
>
> is equivalent to:
>
> transition-property: opacity, color, left;
> transition-duration: 1s, 2s, 1s;

That's ok I guess, I have no particular preference for how to deal with this case, just that it should be defined. Would the same behaviour apply for all the other transition-* properties?

>> == 2.2 The ‘transition-duration’ Property ==
>>
>> The property uses <time> values, which is different from <Clockvalue> used for specifying time in SVG[3] and SMIL. The grammar of <time> is undefined, though a guess is that it's from CSS 2.1 [2]. If that is the case, there are a few incompatibilies, e.g the ability to specify time in minutes and hours, or a full timevalue with semicolon separators.

Actually s/semicolon/colon/.

>> What's the rationale for not using the <Clockvalue> syntax?
>
> Is there any reason *to* use such things?  In practice, transitions
> are always measured in milliseconds or small numbers of seconds.

My initial guess was that CSS didn't much like the colon separators, which could also be a reasonable explanation.

> Note that the syntax is not *incompatible*, it's merely *incomplete*.

Fair enough.

> Both <time> and <Clockvalue> use units of s and ms.  Thus it can
> always be expanded to support the full range of <Clockvalue> if
> necessary without breaking anything.

Well, if <time> is intended to be used for other things in the future, then it might still be a good idea to consider adding minutes and hours as units on <time>. Say for example  you wanted to specify the duration of some other type of media, like an audio file.

Cheers
/Erik

-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Monday, 2 March 2009 08:04:55 GMT

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