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Re: SVGAnimationElement.getStartTime

From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>
Date: Mon, 9 Feb 2009 11:38:24 +0100
To: www-svg@w3.org
Message-Id: <200902091138.24252.Dr.O.Hoffmann@gmx.de>

Cameron McCormack:
>I don’t know if Olaf agrees, but I’d welcome his opinion here.  (The
>test is still unreviewed at this point, so isn’t official.)


Because I do not use scripting in general, I did not care much
about scripting related things yet and I'm not sure, whether this has
to be the same as for the declarative methods, therefore I
will only comment on the last ones as noted in SMIL.

In 'Building the instance times lists'
http://www.w3.org/TR/2005/REC-SMIL2-20051213/smil-timing.html#Timing-EvaluationOfBeginEndTimeLists
it is noted about syncbase-values:

'syncbase-values and media-marker-values are treated similarly. These 
conditions do not yield an instance time unless and until the associated 
syncbase element creates an interval. Each time the syncbase element creates 
a new interval, the condition yields a single instance time. The time plus or 
minus any offset is added to the list.'

My understanding is, that for

     <animate id="a" begin="5s"... />
     <animate id="b" begin="a.begin+2s" ... />
     <animate id="c" begin="b.begin-5s" ... />

the '7s' appears in the list of #b at 5s and '2s' appears in
the list of #c at 7s.
Because of the timing model of SMIL (inclusive begin, exclusive end),
'7s' in the list of #b appears exactly at 5s.
This means expecially, that #c cannot start at 2s, because b.begin
is not yet resolved at 2s (one has to dive a little bit deeper into
SMIL timing to see what happens with this one at 7s).

I think, animate-elem-201-t contains somehow related subtests
(but) including end, for example the third subtest 'Second interval will
start late' could be interesting.

Note, that the SMIL section contains information too, that the
syncbase times are removed under some conditions again - not sure,
if this is relevant for this DOM method at a later time.

And a note for Brian - the old SMIL animation recommendation may
contain some contradictory details/errors about instance time lists and 
related things, fixed in SMIL2, in doubt one has to check this with SMIL 
2 or 3 to get something usable/reliable.
Received on Monday, 9 February 2009 10:44:39 GMT

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