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Re: animate-elem-46-t.svg

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Tue, 08 Jun 2010 13:55:43 -0400
Message-ID: <4C0E841F.2090906@mit.edu>
To: Daniel Holbert <dholbert@mozilla.com>
CC: "Dr. Olaf Hoffmann" <Dr.O.Hoffmann@gmx.de>, www-svg@w3.org
On 6/8/10 1:29 PM, Daniel Holbert wrote:
> So after having reviewed that link, I think I concede on this issue --
> types.html does indeed say (emphasis added):
> "The common data types for SVG's **properties** and attributes"
> ...and ...
> "The format of a <length> is a <number> **optionally** followed
> immediately by a unit identifier."

This is using "property" in the sense of "something that is set", not 
quite in the CSS sense.

More precisely, the way it seems SVG is meant to work with CSS (insofar 
as it is) is that each element has a number of values that can be 
attached to it.  Associated with each value is a name (e.g. font-size). 
  How the values are derived depends on the syntax used to specify them. 
  In particular, if specified using the CSS syntax, the unit is 
required.  If specified using an XML attribute the unit is not required.

The "format of a <length>" thing is clearly a syntactic requirement; it 
doesn't make any sense to apply it to a raw _value_ (which is, for a 
length, an ordered pair of a number and a unit; the unit may be "user 
units" in SVG).  It does make sense to apply it to string 
representations of property values, so as to derive the in-memory object 
representation.

At least the above is my understanding of the situation.  Please correct 
me if any of the above is wrong.

Now the question I don't know the answer to is what SMIL actually does. 
  In particular, does it operate on value objects, or on strings?  If 
the former, then which rules are supposed to be used to convert those 
strings to value objects and in what cases?

And as a specific example to guide discussion, if you use SMIL to 
animate line-height, what should happen?

-Boris
Received on Tuesday, 8 June 2010 17:56:20 GMT

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