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Re: [CSSWG] Release Candidate for CSS Namespaces Test Suite

From: Leif Halvard Silli <xn--mlform-iua@xn--mlform-iua.no>
Date: Tue, 29 Sep 2009 15:11:39 +0200
Message-ID: <4AC2078B.3030307@xn--mlform-iua.no>
To: Øyvind Stenhaug <oyvinds@opera.com>
CC: public-css-testsuite@w3.org
Øyvind Stenhaug On 09-09-29 12.04:

> On Tue, 29 Sep 2009 03:42:13 +0200, Leif Halvard Silli  
> <xn--mlform-iua@målform.no> wrote:
> 
>>   UAs generally support omitted '*' just fine, except - it turns out -  
>> when used with namespaces: current release of Firefox and Opera will  
>> then not even accept the selector as _valid_. As a consequence the "bar"  
>> selector of the following rules gets ignored (since Firefox/Opera think  
>> the preceding selector is invalid):
>>
>>   *|[foo], bar{} *|.foo, bar{} *|#foo, bar{} *|:first-child, bar{}
> 
> These "foo" constructs don't seem to be allowed by the Selectors grammar  
> (<http://www.w3.org/TR/css3-selectors/#w3cselgrammar>).


   In pointing to that grammar, do you then refer to the following 
3 lines - or do you also refer to something more than that in that 
grammar? The 3 lines:

     universal
       : [ namespace_prefix ]? '*'
       ;

   If this is all you refer to, then please note that the 
[namespace_prefix] is a 0 or 1 option. And that there are no 
special rules defined here w.r.t. whether there is - or isn't - a 
namespace prefix. Thus, if these 3 lines are all that you refer 
to, and if your reading of the rule is correct, then we would also 
have to conclude that the following example, which is based on an 
example from the Universal selector section - and which the draft 
  directly says is _legal_ [see below], actually is illegal:

   [hreflang|=en]{color:lime}

   And thus, if this is the case - if the grammar says that this 
rule is wrong, then the grammar is not in tune with the prose of 
the draft - or with common implementations either.


Let me go through what the prose says:

   The prose says 
[http://w3.org/TR/css3-selectors/#universal-selector]:

     "If the universal selector is not the only component of
      a sequence of simple selectors, the * may be omitted."

     Examples:

     *[hreflang|=en] and [hreflang|=en] are equivalent,
     [ snip ]

   The logical conclusion to this is that [hreflang|=en] is - in 
fact - a universal selector. Because, according to CSS 2.1, every 
simple selector is either a universal selector or type selector 
[http://w3.org/TR/CSS21/selector.html#selector-syntax].

   The next section of CSS3 selectors talks about universal 
selectors and namespaces 
[http://w3.org/TR/css3-selectors/#univnmsp]. All of the examples 
in that section types the "*" directly - but we cannot conclude 
from that, that the "*" _has_ to be typed directly.

   Here are the example section in full:

     ns|* all elements in namespace ns
      *|* all elements
       |* all elements without a namespace
        * if no default namespace has been specified, this
          is equivalent to *|*. Otherwise it is equivalent
          to ns|* where ns is the default namespace.

   Here it is said that "*" is equivalent to "*|*". The logical 
conclusion is "*|*" and "*" are equivalent also when the universal 
selector is omitted.

   Thus it is logical that *|*[hreflang|=en] and *|[hreflang|=en] 
are equivalent with *[hreflang|=en]' and [hreflang|=en] - see the 
first example that I quoted.

   Further below, the draft speaks about attribute selectors, 
including namespaces and attribute selectors 
[http://w3.org/TR/css3-selectors/#attrnmsp].  Here the draft *does 
not* discuss *|[attr]. Instead it discusses [ns|attr]. This, if 
you ask me, confirms that a lone [attr] is a legal, universal 
selector also when it is written as *|[attr].

   The Selectors Level 3 draft could need an update that makes 
clear that it is permitted to write *|[attr] (or that directly 
forbids it, if that should become the solution - I hope not, and 
see no reason to do it - on the contrary [more on that later, if 
need be ...]).

   All this confirms that it is correct to warn against omitting 
the "*", as I believe Selectors Level 3 does. But it also points 
to a language problem: When the draft speaks about attribute 
selectors, then it does - in one way - actually speak about 
universal and/or type selectors. Perhaps the draft should say 
that, whenever an attribute selector is not attached to a type 
selector or to the "*", then it represents - in fact - a universal 
selector.
-- 
leif halvard silli
Received on Tuesday, 29 September 2009 13:12:26 GMT

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