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Re: Transitions and Animation merging: problem summary

From: Chris Marrin <cmarrin@apple.com>
Date: Fri, 16 Apr 2010 09:41:09 -0700
Message-id: <9F655E94-66D0-480A-80AD-8C943A422143@apple.com>
To: W3C Emailing list for WWW Style <www-style@w3.org>

On Apr 15, 2010, at 11:24 AM, Simon Fraser wrote:

> ...3. Keyframe reversal
> 	It has been suggested that it should be possible to re-use a set
> 	of  @keyframes in reverse.
> 	We think that in many cases this will not produced the results
> 	that the designer intended; keyframes often describe a
> 	non-symmetrical  motion that does not feel right when reversed.

I wanted to reiterate this point a bit. 

There has been discussion that it would be desirable to have reversing transitions in some cases. For instance, if sliding out a menu on hover and you unhover while the transition is running, it would be very convenient to simply stop and slide the menu back in using the same transition running backwards from that point. This sort of transition effect is often simple and linear, possibly with some ease in and/or ease out. So reversing the transition makes sense. It adds to the simplicity of this simple operation. We should explore reversing transitions (but in a separate thread).

Animations are different. They are often carefully crafted paths that perform just what a graphic designer wants. Running them backwards breaks the graphic designer's intent. Imagine you film an actor getting out of a car but later realize that you need a shot of the actor getting INTO the car. You wouldn't run the scene backwards to achieve that effect. That's why we feel reversing animations is not an important effect to get into the spec.

Received on Friday, 16 April 2010 16:41:43 UTC

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