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[css3-values] Syntax of attribute values for attr()

From: Simon Sapin <simon.sapin@kozea.fr>
Date: Sun, 17 Feb 2013 19:46:20 +0100
Message-ID: <5121257C.2090404@kozea.fr>
To: www-style@w3.org
Hi,

attr() defines a few <type-or-unit> keywords that determine how to parse 
an attribute value. Each keyword definition starts with either:

1. The attribute value will be parsed as the contents of a CSS <string>
2. The attribute value must parse as a (X) CSS token


Does "parsing as <string>" mean interpreting CSS backslash-escapes? I 
think it should not, but the current spec text is unclear. Not 
interpreting escapes means that the <string>ís value is exactly as would 
be returned by element.getAttribute(name). HTML and XML already have an 
escaping mechanism, adding one is not necessary.


"Parsing as a token" should fail if the tokenizer returns more than one 
token. But what about leading and trailing whitespace? I think they 
should be removed/ignored but again the spec is unclear. What about CSS 
comments? I think this should be consistent with "presentational hint" 
attributes, and [1] seems to indicate that they should not be allowed 
there. (Search for "SVG wart". Not sure if it also applies to non-SVG 
attributes.)

[1] http://lists.w3.org/Archives/Public/www-style/2013Feb/0402.html

The tokenizer does not even emit comment tokens in the current 
css3-syntax ED. We might need to change that because of the above.


Finally, I think that attr(foo url) should also remove leading and 
trailing whitespace from the attribute value, in order to be consistent 
with HTMLís concept of "valid URL potentially surrounded by spaces" used 
for href attributes.

http://www.w3.org/TR/html5/links.html#attr-hyperlink-href
http://www.w3.org/TR/html5/infrastructure.html#valid-url-potentially-surrounded-by-spaces


Note that all of these are clarifications rather than changes, so being 
in CR should not be a problem.


Cheers,
-- 
Simon Sapin
Received on Sunday, 17 February 2013 18:46:46 GMT

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