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Re: Media types (are qualifiers lost?)

From: Al Gilman <asgilman@access.digex.net>
Date: Thu, 30 Oct 1997 18:10:07 -0500 (EST)
Message-Id: <199710302310.SAA27744@access2.digex.net>
To: w3c-css-wg@w3.org, w3c-wai-hc@w3.org (HC team)
to follow up on what Jason White said:

> I would like to summarise briefly in this forum the media type issue which
> I raised on the IG list yesterday.
> 
> The problem, essentially, is that if media type values are truncated prior
> to being matched against the media type of the output device, then so soon
> as parameterized values are introduced, the truncation which is mandated
> by the current HTML 4.0 draft will result in different media types being
> treated as identical. For example:
> media="screen enlarged" and media="print enlarged"
> become:
> media="screen" and media="print" respectively. Furthermore, since "screen"
> is the default media type, a style sheet without an explicit media type
> value would be applied as part of the cascade, even if the default style
> sheet was of type media="screen enlarged"
> 
> I do not regard this as a desirable result from the standpoint of
> accessibility.
> 
> 

I am copying w3c-css-wg on this as I think we need to be clear
both with HTML and with CSS2 on what happens, here.

The way I read the spec there is only the appearance of a
problem, not an actual problem.

In my reading of the October 24 draft for HTML 4 it does say that
HTML user agents must be capable of doing the parsing that strips
trailing qualifiers to isolate the base type and that they may
ignore media type entries which do not match a predefined base
type.

I do not believe that the present specification language requires
a browser to ignore media subtypes or parameters, or that it
requires a browser even to ignore off-the-wall media types such
as if the HDML people don't want to subtype "tty" but instead
start releasing stylesheets calling for a "hhd" medium, the HTML
spec as written will let a browser process that style if it
wishes.

Dave?  Chris?  Am I reading this right?

As I read it, the whole point of the "future versions of HTML may
define...  parametric" explanation is to say that browsers
designed to this spec have to be compatible with media type
indications that contain subtype or parameter qualifiers.

This spec doesn't require them to honor such qualifiers in any
way.  But it doesn't stop them, either.  CSS2 or the Browser
Guidelines could ask for specific functions relating to media
type qualifiers and it would be entirely consistent with this
specification language.

-- Al Gilman
Received on Thursday, 30 October 1997 18:10:24 EST

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