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Re: Proposal: Fix discrete to animation in SVG 1.1 Second Edition

From: Cameron McCormack <cam@mcc.id.au>
Date: Mon, 28 Mar 2011 11:18:04 +1300
To: Brian Birtles <birtles@gmail.com>
Cc: www-svg <www-svg@w3.org>, www-smil@w3.org
Message-ID: <20110327221804.GA5006@wok.mcc.id.au>
Hi Brian.

I have SVG-ACTION-3013 to look into this.  I believe the changes are
good, and I like your proposed wording but have comment on it:

Brian Birtles:
> Proposed change:
> ----------------
> 
> In section 19.2.9 'Attributes that define animation values over time'
> change the paragraph:
> 
>   The processing rules for the variants of from/by/to animations are described
>   in Animation function values.
> 
> to:
> 
>   The processing rules for the variants of from/by/to animations are
>   described in Animation function values with the following exception.
> 
>   In order to provide intuitive and consistent behavior when the starting
>   value of an animation is explicitly specified by a "from" attribute (e.g.
>   "from-to animation") and when the underlying value is used (e.g. "to
>   animation") the behavior of discrete to-animation in SVG deviates from the
>   definition in SMIL Animation.

This paragraph confused me on first read.  I think it would be slightly
clearer like this:

  In order to provide behavior that is intuitive and consistent between
  discrete animations with an explicitly specified "from" attribute
  (e.g. "from-to animation") and those where the underlying value is
  used (e.g. "to animation"), the behavior of discrete to-animation in
  SVG deviates from the definition in SMIL Animation.

>   As with a discrete from-to animatiom, a discrete to animation will set the
>   underlying value for the first half of the simple duration (or, if a
>   keyTimes list is provided, until the offset into the simple duration
>   specified by the second value in the keyTimes list) and the "to" value for
>   the remainder of the simple duration.
…
> Interoperability:
> -----------------
> 
> Opera 11.01, Batik 1.7, and WebKit nightly build r80213 (3 Mar 2011)
> all provide identical animation for both of the provided examples.
> i.e. they do not conform to the specified behaviour but follow this
> proposal.
> 
> (I note however that Opera and WebKit appear to ignore keyTimes in this case.)

I made a simple test, too:

  http://dev.w3.org/SVG/profiles/1.1F2/test/svg/animate-elem-92-t.svg

I would prefer to make this change only if we test it (by approving the
above test) and if we have at least two passing implementations of it.
As you mention, Opera and WebKit ignore keyTimes on discrete to-
animations, so of the above implementations (which are the only ones I
currently have access to that implement animation) only Batik passes the
test.

-- 
Cameron McCormack ≝ http://mcc.id.au/
Received on Sunday, 27 March 2011 22:19:50 GMT

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