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Re: SVG Presentational Attributes, attributeType="CSS" vs "XML": same or different?

From: Daniel Holbert <dholbert@mozilla.com>
Date: Fri, 22 Jan 2010 11:06:46 -0800
Message-ID: <4B59F746.5050802@mozilla.com>
To: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>
CC: www-svg@w3.org
Thanks for the feedback! I think I think I agree that Opera's behavior 
is the most sane and is what was probably intended.  At this point, 
that's the behavior I'll be shooting for with my patch for Mozilla.

However, I still think that both SVG 1.1 & SVG 1.2Tiny are misleading on 
this point and need additional clarification.  Details below...

On 01/22/2010 02:55 AM, Dr. Olaf Hoffmann wrote:
> I cannot see a problem with this:
>   >  Animation of presentation attributes is equivalent to animating the
>   >  corresponding property. Thus, the same effect occurs from animating
>   >  the presentation attribute with attributeType="XML" as occurs with
>   >  animating the corresponding property with attributeType="CSS".
>
> Of course, there is itself no different effect, if it is interpreted
> correctly, what 'effect' means).

I disagree -- in some situations, Opera (which you say is most correct) 
yields an unquestionably different effect, regardless of what you define 
"effect" to mean.

In the test I provided[1], compare cases (e) vs (f).  The only textual 
difference betwen those two is attributeType=XML vs CSS -- one animates 
the presentation attribute, and one animates the corresponding property. 
According to the quoted block above, that should "produce the same 
effect", and yet Opera (which you say is most correct) produces very 
different visual results.  On every level, that's a *different effect*.

If Opera's behavior is indeed correct, then I don't think it's "effect" 
that needs clarifying -- I think it's rather the situations under which 
the above-quoted block applies.

It looks like SVG 1.2 Mobile tried to clarify this a bit by adding the 
caveat "In the absence of style sheets" (which explains away the 
distinction between (e) vs (f) described above).  But that's not 
generally sufficient -- it also needs an additional caveat, saying 
something like this:

    In the absence of any other animations targeting the
    presentation attribute and corresponding property...

In situations covered by that additional caveat, then yes, I'd agree 
that attributeType="XML"/"CSS" should have the "same effect".  *Without* 
that caveat, though, it's unclear what should happen when CSS and XML 
animations interact, in cases like (a) and (b) from my testcase. (In 
fact, the implication right now is that they should be treated as 
indistinguishable -- i.e. that they should add to each other, etc.)

> If one manages to isolate a simple enough sample,
> the visible result can be the same.

Right -- and my point is that if the spec is going to declare two things 
as having "the same effect", and as being "equivalent", it needs to more 
clearly define the ("simple" as you say) situations in which that is 
true.  I believe the caveat I provided above (or something similar) 
would fix the ambiguity.

Thanks for the response,
~Daniel
[1] 
http://people.mozilla.org/~dholbert/tests/smil/compat_tests/xmlVsCssChart_v1.svg
Received on Friday, 22 January 2010 19:07:20 GMT

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