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[SVGMobile12] SVGT12-183: Rules for handling "unsupported" values don't work when properties are syntactically correct and specified using W3C mechanisms other than SVG attributes

From: Ian Hickson <ian@hixie.ch>
Date: Thu, 8 Dec 2005 23:38:18 +0000 (UTC)
To: www-svg@w3.org
Message-ID: <Pine.LNX.4.62.0512082334110.17886@dhalsim.dreamhost.com>


SVG 1.2 defines the 'fill' and 'stroke' properties as taking the values 
defined as <paint>. One of the possible values is <iri>. The definition 
says that if the IRI reference is not valid, it must be considered as 
unsupported and processed as if it hadn't been specified.

However, properties are conceptually always specified. For instance, if a 
CSS3 stylesheet (or an SVG 1.1 document rendered in a UA that supports the 
SVG 1.1 <style> element) contained the following rule:

  circle { fill: url(data:,notvalid); }

...then the computed value of 'fill' on a <circle> element matching that 
rule would be 'url(data:,notvalid)', regardless of whether that was valid 
or not valid on a particular element.

It becomes impossible, therefore, to process the 'fill' property "as if it 
hadn't been specified", since by definition computed values of properties 
are always "specified"; at parse time it is not possible to determine the 
validity of a particular value beyond its conformance to the CSS syntax.

Please correct the specification so that unsupported values of <paint> 
have implementable handling, e.g. requiring that unsupported values be 
treated as 'black'.

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'
Received on Thursday, 8 December 2005 23:38:28 GMT

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