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[css3-values] double bar syntax and value repetition

From: Erik Dahlstrom <ed@opera.com>
Date: Mon, 07 Jan 2013 17:49:18 +0100
To: "www-style@w3.org" <www-style@w3.org>
Message-ID: <op.wqjvoga2geuyw5@gnorps>
Hi all,

I have a question about the component value syntax, more specifically the
double bars, ||, that can separate values in CSS syntax, used e.g in the
background property[1]. The CSS3 values and units spec[2] states that:

[[ A double bar (||) separates two or more options: one or more of them
must occur, in any order. ]]

What is the expected result is when an option is repeated? I don't see a
clear answer in the spec. (The same spec text is also duplicated in CSS3
Syntax [3]).

My interpretation is that options cannot be repeated, but the spec text
"one or more of them must occur" makes it seem as though e.g "paint-order:
fill fill" is allowed (from SVG2 'paint-order' property [4] which also
uses the || syntax).

How about adding something to clarify that options can only occur once in
the given set? E.g:

[[ A double bar (||) separates two or more options: one or more of them
must occur, in any order. Each option can occur at most one time. ]]



[1] http://www.w3.org/TR/css3-background/#the-background
[2] http://www.w3.org/TR/css3-values/#component-combinators
[3] http://www.w3.org/TR/css3-syntax/
[4] https://svgwg.org/svg2-draft/painting.html#PaintOrderProperty


-- 
Erik Dahlstrom, Core Technology Developer, Opera Software
Co-Chair, W3C SVG Working Group
Personal blog: http://my.opera.com/macdev_ed
Received on Monday, 7 January 2013 16:49:48 GMT

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