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

From: Erik Dahlström <ed@opera.com>
Date: Fri, 27 Feb 2009 09:54:18 +0100
To: "www-style@w3.org" <www-style@w3.org>
Cc: www-svg <www-svg@w3.org>
Message-ID: <op.upz5osvidhsuf5@gnorps.linkoping.osa>
Hello CSS WG.

Cameron McCormack <cam@mcc.id.au> wrote:

  The SVG Working Group spent some time last week reviewing the CSS
  Transitions and Animations modules.  At this stage, we won’t be sending
  an official single review mail from the group, but instead we’ll send
  some individual comments.  Below are some comments from me on
  Transitions, although it is reasonably safe to assume that other members
  of the SVG WG agree with them too.  (Comments on CSS Animations are

The same goes for this mail, I've left out some points already covered by Cameron. The review was based on the Editor's draft 10 February 2009[1].

== 5.2 "Properties from SVG" == 

The list of properties here is incomplete, and incompatible with the SVG CSS properties that are defined to be animatable. E.g audio-level, line-increment, and a bunch of properties that aren't naturally interpolable, e.g fill-rule.

Why not simply refer to the SVG specifications for which such properties are animatable? 

== 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?

== 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.

What's the rationale for not using the <Clockvalue> syntax?

== 3 Transition Events == 

Would one always get a 'transitionend' event, even if the duration was 0?

How about if a duration was close to 0 and the implementation was too busy to actually apply the transition, and there was another transition on the same property starting at some minor timedelta ahead? Would you still get the 'transitionend' event on the first one?

What's the rationale for not using (extending if need be) the TimeEvent interface[4]?

== 4 Animation of property types ==

What happens if you want to interpolate two values that have different units? Is that something that can never happen?

Color interpolation in svg takes into account the 'color-interpolation' property[5], why does transitions not use that as well?

What's the rationale for wanting to interpolate HSL color values in RGB space?


[1] http://dev.w3.org/cvsweb/~checkout~/csswg/css3-transitions/Overview.html?rev=1.1&content-type=text/html;%20charset=iso-8859-1
[2] http://www.w3.org/TR/CSS21/aural.html#times
[3] http://www.w3.org/TR/SVG11/animate.html#ClockValueSyntax
[4] http://www.w3.org/TR/2001/REC-smil-animation-20010904/#DOMSupport
[5] http://www.w3.org/TR/SVG11/painting.html#ColorInterpolationProperty

Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Friday, 27 February 2009 08:53:03 UTC

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