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Re: SVG12: animating transform ref()

From: Ola Andersson <Ola.Andersson@ikivo.com>
Date: Wed, 15 Mar 2006 11:45:48 +0100
Message-ID: <234EB4699C751A4A95DF4FD8D041BBFD053464@SESTHSRV10.zoomon.local>
To: <www-svg@w3.org>, <derhoermi@gmx.net>

Hi Björn,
We're not saying that the snippet below is not allowed.  

  ... transform = 'ref(...)' ...
    animateTransform ... to = '...'

It is allowed and we believe the behavior to be well defined in http://www.w3.org/TR/SVGMobile12/animate.html#AnimateTransformElement. This section says that if you have an animateTransform that needs to consider the underlying value, the underlying value is the identity matrix. So a "to-animation" would interpolate between the identity matrix and the given to value and then post-multiply this with the CTM.Whether 
transform = 'ref(...)' or e.g. transform = 'scale(...)' doesn't matter for the calculations.  
Thanks for your thorough review, please let us know shortly if this does not address your concerns.
/The SVG WG

----
From: Bjoern Hoehrmann <derhoermi@gmx.net> 
Date: Wed, 28 Dec 2005 08:40:51 +0100
To: "Ola Andersson" <Ola.Andersson@ikivo.com> 
Cc: <www-svg@w3.org>, "SVG WG" <w3c-svg-wg@w3.org> 
Message-ID: <trf4r15b530fdksffehc0gv18mjbmoiafb@hive.bjoern.hoehrmann.de> 

* Ola Andersson wrote:
>It is not possible to animate a transform that is of ref() type. We
>believe this is clear in the spec since it says that the type attribute
>on animateTransform can have type = "translate | scale | rotate | skewX
>| skewY". Therefore ref() is not animatable. The WG has now made this
>clearer in the spec by adding the following to the type attribute
>definition: "If type has an unsupported value (e.g. type="foo" or
>type="ref(svg)") the 'animateTransform' element is ignored."

I did not say the specification is unclear about whether the type
attribute allows a value like ref(svg); I don't think the new text
should be there as it seems redundant with other requirements and
I am more concerned about a case like

  ... transform = 'ref(...)' ...
    animateTransform ... to = '...'

which you seem to be saying is disallowed; there does not seem to be
language to that effect in the current draft, and if it is allowed,
the semantics of such an animation aren't really clear to me, e.g.,
whether changes to the CTM would be considered changes to the base
value of the animated transform.
-- 
Björn Höhrmann · mailto:bjoern@hoehrmann.de · http://bjoern.hoehrmann.de
Weinh. Str. 22 · Telefon: +49(0)621/4309674 · http://www.bjoernsworld.de
68309 Mannheim · PGP Pub. KeyID: 0xA4357E78 · http://www.websitedev.de/ 
Received on Wednesday, 15 March 2006 10:44:09 GMT

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