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Re: [css3-transitions][css3-animations] There is an animationstart event but no transitionstart

From: Simon Fraser <smfr@me.com>
Date: Wed, 09 Jun 2010 08:43:47 -0700
Cc: www-style list <www-style@w3.org>
Message-id: <584DC7D7-CFAE-4E62-93C1-E80A30639A36@me.com>
To: Sylvain Galineau <sylvaing@microsoft.com>
On Jun 8, 2010, at 8:13 PM, Sylvain Galineau wrote:

> I thought the reason(s) why there was no transitionstart event have been mentioned either here or on the telcon but am having no
> luck locating the relevant post. So why the discrepancy ?

Initially we had no events for transitions. This was bowing to the "animation is behavior and therefore should not be in CSS" crowd, for whom we thought that more events would be an indication that we saw animation as behavior too.

In addition, relying on events firing when using transitions in complex content can lead to problems, because you have to be sure that a transition will actually run when you expect it to. Transitions will not run (and therefore no events will fire) if the value of the property you are expecting to change does not actually change.

We added events for animations from the start, because
1) we expected animations to be used in richer content which needs more notifications about when animations are running
2) animations run explicitly, so the events will always fire when you expect them too.

The transitionEnd event was added later, as we discovered its utility.

I have nothing against adding a transitionStart event.

Simon
Received on Wednesday, 9 June 2010 15:44:40 GMT

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