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keyTimes query

From: Brian Birtles <birtles@gmail.com>
Date: Sat, 22 Oct 2005 10:26:53 +1000
Message-ID: <65fa1620510211726s53fd8588p@mail.gmail.com>
To: www-smil@w3.org

Dear all,

I hope this is the correct forum for asking about two issues which I
think need clarification in the SMIL Animation and SMIL 2
specifications. If not, please excuse this message.

1. In seciton 3.2.3 of the SMIL Animation specification the keyTimes
attribute is described and the following constraint is given:

"For linear and spline animation, the first time value in the list
must be 0, and the last time value in the list must be 1."

Later in that section, the following example is given:

<animate attributeName="foo" from="10" to="20"
     dur="10s" keyTimes="0.0; 0.7"
     calcMode="spline" keySplines=".5 0 .5 1" />

The behaviour of the example is given as "The keyTimes values cause
the value of 20 to be reached at 7 seconds, and to hold there for the
remainder of the 10 second simple duration."

This seems to contradict the constraint provided earlier. Perhaps this
is a special case for from-to animation but I can't find a reference
to such an exception elsewhere.

2. In the same section (3.2.3) the following example is given of the
keyTimes attribute:

<animateColor attributeName="color" dur="10s" calcMode="discrete"
     values="green; yellow; red" keyTimes="0.0; 0.5;" />

Firstly, the trailing semi-colon in the keyTimes value seems out of
place but perhaps it is my understanding of the following explanation
that is at fault:

'This example also shows how keyTimes values can interact with an
indefinite duration. The value of the "color" attribute will be set to
green for 5 seconds, and then to yellow for 5 seconds, and then will
remain red for the remainder of the document, since the (unspecified)
duration defaults to "indefinite".'

I first thought that perhaps the "unspecified duration" referred to
the missing keyTime but nowhere else is it mentioned that keyTimes can
be indefinite. Furthermore I would not expect that such a keyTime
specification can extend the duration of the <animateColor> element
beyond its specified duration of 10s but the description says it "will
remain red for the remainder of the document."

Thankyou for any clarification you can offer. I am attempting to
contribute SMIL Animation to Mozilla's on-going SVG implementation.


Brian Birtles.
Received on Saturday, 22 October 2005 06:53:12 UTC

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