Re: [css-animations] How animation-timing-function in keyframe rule interacts with direction

On Oct 18, 2014, at 12:05 am, Tab Atkins Jr. <jackalmage@gmail.com> wrote:

> On Fri, Oct 17, 2014 at 7:09 PM, Simon Fraser <smfr@me.com> wrote:
>> On Oct 16, 2014, at 2:47 PM, Sylvain Galineau <galineau@adobe.com> wrote:
>>> We should resolve the issue raised by dbaron [1] (Bug 14805 [2])
>>> 
>>> If we have:
>>> 
>>>      @keyframes timings {
>>>              25% { animation-timing-function: linear; }
>>>              40% { animation-timing-function: ease-out; }
>>>      }
>>> 
>>> ..then when the animation moves forward we expect linear to apply between 25% and 40%. But if the animation is moving backward e.g. due to an animation-direction: alternate then we also want linear to apply between 40% and 25%.
>>> 
>>> Objections?
>>> 
>>> 
>>> [1] http://lists.w3.org/Archives/Public/www-style/2011Mar/0744.html
>>> [2] https://www.w3.org/Bugs/Public/show_bug.cgi?id=14805
>> 
>> 
>> I don’t think that’s right. The reverse animation should be a mirror-image of the forward animation, so the reverse animation should be linear for the last 25% of its travel.
> 
> Maybe you misread?  The forward animation is not linear in its first
> 25%, it's whatever the 'animation' property sets as its timing
> function.  The forward animation is linear between 25% and 40%, so the
> reverse animation should be linear between 40% and 25% (counting
> backwards).

You’re right, I missed the missing 0% keyframe.

Simon