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

On Mon, Oct 20, 2014 at 10:29 AM, Sylvain Galineau <galineau@adobe.com> wrote:
>
> On Oct 18, 2014, at 8:29 AM, Simon Fraser <smfr@me.com> wrote:
>
>> 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.
>
> Added this animation-timing-function:
>
>         # When specified in a keyframe, 'animation-timing-function' defines the progression of the
>         # animation between the keyframe and the next keyframe in sorted keyframe selector order, or
>         # the end of the animation if no other keyframe is defined. The specified timing function will
>         # apply over this interval independently of the animation's current direction.
>
> Makes sense?

It makes sense, but I'm not super happy with it. I'll see if I can
wordsmith something for it to make it a little clearer.

~TJ

Received on Monday, 20 October 2014 17:35:07 UTC