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Re: Proposal: Fix frozen to-animation

From: Brian Birtles <birtles@gmail.com>
Date: Fri, 25 Mar 2011 20:48:36 +0900
Message-ID: <AANLkTiked3ZbCN9J1PmvVsLKsBp53Vhkc6y=o9VNp7K5@mail.gmail.com>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
Cc: www-svg@w3.org
Dear Olaf,

Thank you very much for your response! I will follow it up below.

2011/3/25 Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>:
> The proposed behaviour is available already, if no to-animation is
> used, therefore if authors need this behaviour, they can simply use
> values animations.

I do not believe it is already available. If we have:

  <animate attributeName="y" values="100; 50; 100; 150; 100" dur="2s"
  <animate attributeName="y" begin="a.click" to="100" dur="2s"
repeatCount="0.75" fill="freeze"/>

I would like to clamp this animation gradually to 100 with a
to-animation, but should the clamping function finish part-way through
its simple duration it should constrain the underlying animation to
the extent that it is applied. I'm not aware of a way to achieve this
result with values animation without knowledge of both the underlying
animation function and without synchronisation with its timing.

Admittedly, the currently defined behaviour also cannot be achieved
with other constructs (since it too depends on the values and timing
of the underlying animations) but I believe the currently defined
behaviour is both less intuitive and less useful and if it is
required, easier to simulate (with a set animation given the
appropriate to value).

> I think, the attempts (as for discrete animation) to change to-animations
> and the bugs in several current viewers indicates a general misconception of
> such implementations to treat it as an ordinary animation.
> ...
> Because [to animation] is defined to be different to
> values-animations, it should be no surprise, that it behaves different and
> needs a different implementation - this is the whole point about it ;o)

This proposal does not attempt to make to-animation behave like other
animation types. Rather, it makes to-animation consistent with itself.
That is, it removes a special case formula that only applies when a
to-animation is frozen and instead defers to normal to-animation
behaviour. (If anything, it makes to animation more special, not

Best regards,

Received on Friday, 25 March 2011 11:49:08 UTC

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