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Re: animate-elem-46-t.svg

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Wed, 09 Jun 2010 14:48:40 -0400
Message-ID: <4C0FE208.9080907@mit.edu>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
CC: www-svg@w3.org
On 6/9/10 1:08 PM, Dr. Olaf Hoffmann wrote:
> In doubt to address a feature in this, one can use attributeType="XML".
> attributeType="CSS" addresses the CSS like structures.

Yes.

> At this point it does not really matter, who defined the property or
> the attribute. If it exists, one can apply an animation effect to
> it independently.

Well, that's the issue here, no?  At what point is the string in the 
SMIL attribute converted into a value?  Who's responsible for defining 
the conversion?

> However, the CSS type on SMIL animation uses this final
> result from applying the CSS cascade as underlying value -
> or another animation of the same type.

Yes, I understand that.  That's not the issue here.

> Altogether all this is unpleasantly complex.

Well, sure.  That's why we're having this discussion.

>> Is that true, though?  SMIL explicitly talks about attributeType="CSS"
>> in terms of the override stylesheet and so forth; the behavior of that
>> is defined by CSSOM and CSS, not by the host language.
>
> The host language defines the meaning of attributes and properties
> (roughly what you put in and what you get out of the SMIL machine
> and what presentation the output might cause).

I'm not looking for "meaning"; I'm looking for syntax constraints.  Can 
you please cite where the SMIL spec says what defines the syntax of 
attributeType="CSS" animations, if anywhere?

> In detail, we can have this choice:
> normal |<number>  |<length>  |<percentage>  | inherit
> therefore here 2px is not the same as 2.

Right.  Neither is it for CSS syntax in general, of course; it's just 
that here the value space includes both positive integers and lengths, 
which it doesn't for most properties.

The question, again, is the point at which conversion from strings to 
values happens and the rules to be used.

> SMIL itself does not claim, that 2px is the same as 2.

OK.

> To be able to animate values="2;2px;2%" continuously,
> something outside of SMIL is required to get the same unit
> for all values to calculate the animation effect.

So is the "something outside" basically responsible for converting those 
strings to values?

What exactly does the override stylesheet language in SMIL3 (which seems 
clear enough to me, for what it's worth, but I want to make sure I'm not 
missing something) mean to you?

> Without additional information from the host language,
> SMIL animation falls back to calcMode discrete,
> no continuous animation.

That doesn't matter for my purposes; I don't care how the interpolation 
between values happens; I care about what the values mean to start with 
and how the UA is supposed to determine what values the strings 
correspond to.

-Boris
Received on Wednesday, 9 June 2010 18:49:14 GMT

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