[css-animations] Should really a reversed animation use the reversed timing function?

The current draft says the following about reversed animations:
"*When an animation is played in reverse the timing functions are also

Assuming that current browsers' implementation of the draft are correct,
then when using animation-direction:alternate what happens is the following
(tested on Chrome and Firefox):

i.e. the timing function (which in this case is approximately a
cubic-bezier(1,0,1,0)) is reversed into a cubic-bezier(0,1,0,1).
At first I doubted that this was the intended meaning of "reversed timing
function", but seeing that Chrome and Firefox do the same, I guess that
must be it.

However, I wonder, wouldn't it be more useful and intuitive to do it like
i.e. to use the same timing function as is, without reversing it.

Let me show you an example that illustrates why this second approach could
be more useful.
When you are using a step function like step-start, the sequence of forward
and reversed animations look like this:

The function step-start is reversed into a step-end alternately and the
result is that the animation stays at the end state all the time.
But, obviously, this is not what you want when using

What you really want is this:

i.e. the same step-start function is used for both the forward and reversed
animations all the way.
I hope it makes sense. Please give it a thought.


Received on Wednesday, 25 May 2016 06:19:58 UTC