Re: [XBL] CSS support for XBL 2.0 user agents: Yes or no?

On Fri, 6 Oct 2006, Karl Dubost wrote:
> Le 6 oct. 06 à 10:20, Ian Hickson a écrit :
> > On Thu, 5 Oct 2006 karl@w3.org wrote:
> > > 
> > > # XBL user agents that do not support CSS should not render the XBL
> > > # elements.
> > > 
> > > Though earlier in the specification, it is said:
> > > 
> > > # The element attribute of the binding element and the includes attribute
> > > # of the content element, if specified, must be parsed according to the
> > > # rules in the Selectors specification. [SELECTORS]
> > 
> > I do not understand the reference to the part of the specification 
> > that mentions Selectors above. What about it?
> 
> In http://www.w3.org/TR/2006/WD-xbl-20060907/#attributes
> 	The element attribute of the binding element and the includes
> 	attribute of the content element, if specified, must be parsed
> 	according to the rules in the Selectors specification. [SELECTORS]
> 
> User Agents have to implement CSS 3 Selectors to parse the value of 
> "element" attribute and the value of "includes" attribute.

Oh. I understand the confusion. There is no specification called "CSS3 
Selectors"; the Selectors specification is an independent specification 
and not considered part of CSS. It is possible to implement Selectors 
without implementing CSS -- indeed, an example of this would be 
implementation of XBL that doesn't support alternative presentations. It 
has to implement Selectors, but doesn't have to implement the CSS 
rendering model or any of its properties.


> > > The XBL 2 specification has to define what "do not support CSS" 
> > > means. Which level, and/or which individual modules?
> > 
> > It doesn't really matter -- the specification gives two options, one 
> > for CSS-aware UAs, and one for CSS-unaware UAs. Whether or not a 
> > particular UA supports CSS or not is up to the UA's vendor, really; 
> > the result either way as far as XBL is concerned is the same. 
> > Basically this is just requiring a behaviour and then describing it in 
> > terms of CSS, so that it can be overridden in CSS contexts.
> > 
> > Let me know if this doesn't satisfy you.
> 
> A user agent which is "not CSS-aware" and then might not implement CSS 3 
> Selectors will not be able to process the values of the attributes.

Hopefully the above clarifies that it is possible to implement Selectors 
without implementing CSS.


> The CSS specifications mentionned in the document are
> 
> 	- CSS3 Basic User Interface Module
> 	- Media Queries
> 	- Selectors

Media Queries are also not part of CSS, but are an independent 
specification. (You can tell which specifications are part of CSS and 
which are not because the CSS specifications have "CSS" in their titles.)

-- 
Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
Things that are impossible just take longer.   `._.-(,_..'--(,_..'`-.;.'