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[css3-animations] animation-timing-function

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Sat, 4 Apr 2009 15:03:36 +0100
To: www-style@w3.org
Message-Id: <200904041603.36622.Dr.O.Hoffmann@gmx.de>
Hello, 

this comment is about:
http://www.w3.org/TR/2009/WD-css3-animations-20090320/#animation-timing-function_tag


a) I think, it would be useful to provide a method for
discrete animations as well, this is much better than
to force authors to use some approximation like this:

@keyframes 'something' {

    0% {
      left: 0px;
    }

    19.9999999999999999999999999999% {
      left: 0px;
    }
   20% {
      left: 100px;
    }


    59.9999999999999999999999999999% {
      left: 100px;
    }
    60% {
      left: 200px;
    }


    100% {
      left: 200px;
    }

  }



b) If the animation-timing-function is not specified for each
keyframe, does the cubic curve apply to the complete animation-duration
as a whole or does it apply for each interval specified by the keyframes
separately?
The prose "The ‘animation-timing-function’ property describes how the 
animation will progress over one cycle of its duration" seems to implicate
the first interpretation, "For a keyframed animation, 
the ‘animation-timing-function’ applies between keyframes, not over the 
entire animation." seems to implicate the second interpretation.

The sentences "For example, in the case of an ease-in-out timing function, 
an animation will ease in at the start of the keyframe and ease out at the end 
of the keyframe. A ‘animation-timing-function’ defined within a keyframe 
block applies to that keyframe, otherwise the timing function specified for 
the animation is used." are even more confusing, because section 2 seems
to define keyframes as points in time, not as intervals, therefore it is not
obvious, what the 'start' and 'end' of a keyframe might mean - maybe
the begin and end of the time interval between two keyframes within the
animation? - then the wording should be improved ;o)

By the way, is the time interval model end exclusive as for SMIL?
Currently I think, with this simple CSS-animations there will be no
visible effect, but this may change, if the draft grows in the next
versions.


Olaf
Received on Saturday, 4 April 2009 14:10:17 GMT

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