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Re: Animation in SVG 1.1

From: Chris Lilley <chris@w3.org>
Date: Thu, 10 Nov 2005 09:20:14 +0100
Message-ID: <1247162410.20051110092014@w3.org>
To: Cameron McCormack <cam-www-svg@aka.mcc.id.au>
Cc: www-svg@w3.org

On Wednesday, November 9, 2005, 5:49:41 AM, Cameron wrote:

CM> Hi.

CM> SMIL Animation states[1]:

CM>   It is recommended that language specifications disallow manipulation
CM>   of animation element attributes through DOM interfaces after the
CM>   document has begun.

CM>   [...]

CM>   Dynamically changing the attribute values of animation elements
CM>   introduces semantic complications to the model that are not yet
CM>   sufficiently resolved. This constraint may be lifted in a future
CM>   version of SMIL Animation.

CM> but in SVG 1.1[2]:

CM>   Unlike other SVG DOM interfaces, the SVG DOM does not specify
CM>   convenience DOM properties corresponding to the various language
CM>   attributes on SVG's animation elements.  [...] The current method for
CM>   accessing and modifying the attributes on the animation elements is
CM>   to use the standard getAttribute, setAttribute, getAttributeNS and
CM>   setAttributeNS defined in DOM2.

CM> which seems to imply that modifying the animation related attributes on
CM> SVG animation elements is supported.

It is, very much, supported. We found the restriction both undesirable
and unenforceable, so we ensured that manipulation of attributes through
script mid way through an animation was well specified. in fact, it
needs to be anyway because you can have multiple concurrent animations
on the same attribute.

CM>   Is this the case?  If so, have the
CM> "semantic complications" been resolved?  SMIL 2.0 (which I realise isn't
CM> referenced by SVG 1.1, but at least might give an indication of what is
CM> the right thing to do) still leaves it as undefined[3].

SMIL 2.0 pulled out the early work on a SMIL DOM, which was still in
SMIL Animation and was further developed in SVG 1.1. The people
producing SMIL 2.0 players were not very interested in scripting, and
for their simple 'media player' use cases it wasn't that big a priority.

CM> Also, in case an errata document is ever produced(!),

of course

CM>  there is a slight
CM> error in http://www.w3.org/TR/SVG11/animate.html#InterfaceTimeEvent
CM> where the text "defined in SMIL Animation: Supported interfaces" is
CM> repeated.


CM> Thanks,

CM> Cameron

CM> [1]
CM> http://www.w3.org/TR/smil-animation/#Integrating-ConstraintsOnAttributes
CM> [2] http://www.w3.org/TR/SVG11/animate.html#InterfaceSVGAnimationElement
CM> [3]
CM> http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-timing.html#Timing-DOMAttributes

 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Thursday, 10 November 2005 08:20:16 UTC

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