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Media types vs. conformance/performance?

From: Bjoern Hoehrmann <derhoermi@gmx.net>
Date: Sun, 1 Oct 2000 18:49:08 +0200
Message-ID: <001b01c02bc8$39f84780$662790d4@de>
To: <www-style@w3.org>
Hi,

[...]
| In general, the following points must be observed by a user
| agent claiming conformance to this specification:
[...]
|  2. For each source document, it must attempt to retrieve all
|     associated style sheets that are appropriate for the
|     supported media types.
[...]

It is impossible to do so, if the user-agent does not retrieve _all_
associated style sheets since a screen media style sheet may may include
a style sheet for aural media and that style sheet may include one for
tty media and so on. For example

  <link rel="stylesheet" media="aural" href="foo.css" />

Where foo.css is like

  @import url("beautiful.css") screen;

and foo.css includes

  @import url("tv.css") tv;

So it makes very small sense to define a media type when linking a style
sheet. Authors must use @media rules to define the media type of a style
sheet.

[...]
| So that user agents can avoid retrieving resources for unsupported
| media types, authors may specify media-dependent @import rules.
[...]

This is an invalid statement. Authors must define media="all" if rules
apply to all media types. The default value of the media attribute in
(X)HTML and so XML is "screen".

Now let's say I'm using a screen media user-agent and tell it to print
the document. What media type is the user-agent of now? Screen and print
or just screen? What if the user-agent is only a print media user-agent
and never presents anything on any screen? Is the user-agent then also
of type screen and print? Or should the user-agent ignore all rules for
screen media when printing? This leads me as an author to say I always
have to declare media="all" if the style sheet is not very special for a
certain media. What style sheets apply for handheld media? What style
sheets apply if this handhelds attempts to print the document?

Or should the user-agent not care about media types and apply all
properties for the supported media groups? If so, it makes no sense at
all to define media types.

If a tv media user-agent attempts to print a document and has to apply
all rules for tv, screen and print media how do the rules cascade? By
there order, specifity and so on? So a screen media style sheet may
override a print media style sheet when the user-agent prints the
document?

I hope i have missed something, I appreciate any comment, regards,
--
Björn Höhrmann ^ mailto:bjoern@hoehrmann.de ^ http://www.bjoernsworld.de
am Badedeich 7 ° Telefon: +49(0)4667/981ASK ° http://bjoern.hoehrmann.de
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Received on Sunday, 1 October 2000 12:55:41 GMT

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