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[Params] Concerned about animating/scripting changes to parameters

From: Jeff Schiller <codedread@gmail.com>
Date: Wed, 17 Jun 2009 13:33:31 -0500
Message-ID: <da131fde0906171133j19cc167dg72ec04da783d35b0@mail.gmail.com>
To: www-svg <www-svg@w3.org>
@name and @value on <param> are animatable?  Really?  Can you also
change the names and values of params via script?  Statements in
section 3.4 seem to inline with that: "If the parameter information
changes, all ‘param’ attribute values must be updated to reflect the
new values, and any rendering changes must be applied."  The primer
does not hint at the DOM API or the scriptability/animatability of
param values (and names!).

I had envisioned this spec as describing a one-time 'pre-processing'
step as opposed to parameters which are living and can be altered by
script/animation at run-time.  In my opinion this brings a whole lot
more complexity that I don't particularly need.

So can you clarify, in the following example

  <circle id="circ" fill="param(foo)" stroke="param(bar)" />

  <use xlink:href="#circ">
    <param name="bar" value="red">
      <set attributeName="value" to="green" dur="2s" />
    </param>
    <param name="foo" value="blue">
      <set attributeName="name" to="bar" dur="2s" />
    </param>
  </use>

If this timeline is correct:

  t=0s: circle is blue with red stroke
  t=2s: circle is ... black with blue stroke?

It seems to me that this would not be very fun for implementers as
they'd have to remember after param-resolving step what parameter
those values came from.  When a param's name changes they'll have to
reset all attributes which were previously referencing that parameter,
etc.

Regards,
Jeff
Received on Wednesday, 17 June 2009 18:34:05 GMT

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