- From: Bert Bos <bert@w3.org>
- Date: Fri, 6 Aug 2010 13:37:13 +0200
- To: www-style@w3.org
On Thursday 29 July 2010 16:05:07 Johannes Koch wrote:
> Hi,
>
> in
> <http://www.w3.org/TR/2009/CR-css3-mediaqueries-20090915/#error-handl
>ing> we read:
>
> Malformed media query. User agents are to handle unexpected tokens
> encountered while parsing a media query by reading until the end
> of the media query, while observing the rules for matching pairs of
> (), [], {}, "", and '', and correctly handling escapes. Media queries
> with unexpected tokens are ignored. [CSS21]
>
> @media (example, all,), speech { /* only applicable to speech
> devices */ }
> @media &test, screen { /* only applicable to screen
> devices */ }
>
> And a little further down:
>
> Media queries are expected to follow the error handling rules of
> the host language as well.
>
>
> In
> <http://www.w3.org/TR/2009/CR-CSS2-20090908/syndata.html#parsing-erro
>rs> we read:
>
> Malformed statements. User agents must handle unexpected tokens
> encountered while parsing a statement by reading until the end of
> the statement, while observing the rules for matching pairs of (),
> [], {}, "", and '', and correctly handling escapes.
Neither of the two examples above is malformed, so this rule doesn't
apply.
>
> and in
> <http://www.w3.org/TR/2009/CR-CSS2-20090908/media.html#at-media-rule>
>:
>
> Invalid statements must be ignored per 4.1.7 "Rule sets,
> declaration blocks, and selectors" and 4.2 "Rules for handling
> parsing errors."
User agents that don't know level 3 of Media Queries will indeed ignore
both examples as a whole, because of this rule.
But user agents that implement level 3 of Media Queries will ignore a
smaller part, viz., just the media query that isn't valid in level 3. A
hypothetical future extension of CSS may still assign a meaning to
those commas and ampersands.
> Is a CSS 2.1 user agent required to ignore both @media rules quoted
> above "by reading until the end of the statement", while a CSS Media
> Queries user agent will only read "until the end of the media query"
> (ignoring "(example, all,)," and "&test,") and apply the set of
> statements to "speech" (1st @media rule) and "screen" (2nd @media
> rule)?
Yes, that is basically it.
Bert
--
Bert Bos ( W 3 C ) http://www.w3.org/
http://www.w3.org/people/bos W3C/ERCIM
bert@w3.org 2004 Rt des Lucioles / BP 93
+33 (0)4 92 38 76 92 06902 Sophia Antipolis Cedex, France
Received on Friday, 6 August 2010 11:37:41 UTC