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

From: Hr Gwea <hrg.wea@gmail.com>
Date: Tue, 24 May 2016 14:38:22 -0300
Message-ID: <CAE++px--sE=sZk=0nA0BTKo6YCxfNX4utK_a9LZbE+WG8+2p=Q@mail.gmail.com>
To: www-style@w3.org
The current draft says the following about reversed animations:
"*When an animation is played in reverse the timing functions are also
reversed*"

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
this:
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
animation-direction:alternate.

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.
‚Äč
I hope it makes sense. Please give it a thought.

Regards.

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

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