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Re: [css-animations] Does animation-fill-mode apply when animation-iteration-count is 0?

From: Sylvain Galineau <galineau@adobe.com>
Date: Wed, 20 Aug 2014 20:13:21 +0000
To: Brian Birtles <bbirtles@mozilla.com>
CC: Tab Atkins Jr. <jackalmage@gmail.com>, "<www-style@w3.org>" <www-style@w3.org>
Message-ID: <27273CD2-675D-472C-80C0-F68B7111F56B@adobe.com>

On Aug 18, 2014, at 9:30 PM, Brian Birtles <bbirtles@mozilla.com> wrote:

> On 2014/08/19 9:26, Tab Atkins Jr. wrote:
>> On Mon, Aug 18, 2014 at 5:05 PM, Sylvain Galineau <galineau@adobe.com> wrote:
>>> Resurrecting an old open issue [1].
>>> 
>>> I'm specifically proposing to resolve that it does apply per Řyvind's response [2].
>> 
>> Yes, it definitely should.  If you don't want an animation, don't set one.
> 
> Agreed.
> 
>>> Note that whether start/end events fire in this case is indeed related though covered by separate issues though opinions on that bit are welcome. For now my higher-order bit is to resolve on whether animation-fill-mode is respected in this case.
>> 
>> Ignoring any legacy constraints, I think they should fire.
> 
> Agreed.
> 
> We should avoid discontinuities where possible, particularly since animation-iteration-count is not necessarily an integer.
> 
> The same is true of zero-duration animations.

Right. In fact, we have prose that says animation-iteration-count:0 behaves like a 0s duration. And animation-duration says:

	# If the <time> is 0s, like the initial value, the keyframes of 	
	# the animation have no effect, but the animation itself still 
	# occurs instantaneously. That is, animation-fill-mode applies 
	# as normal, filling backwards or forwards as appropriate, and 
	# animation events still fire.

In other words, animation-iteration-count:0 will show the 0% keyframe when there is an animation-delay and animation-fill-mode is either 'backwards' or 'both. After the delay expires, the animation runs instantaneously and then uses the values defined by the 100%/to keyframe if animation-fill-mode is set to 'forwards' or 'both'.

I think this is all implied but it might not hurt clarifying this interaction. 
Received on Wednesday, 20 August 2014 20:13:55 UTC

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