Sent by Jens Wedin on 29 October 2004 08:08
Thanks for the thorough answer :)
Jens Wedin
-----Original Message-----
From: Syntactic: Jim Wilkinson [EMAIL-REMOVED]]
Sent: den 28 oktober 2004 20:16
To: Wedin, Jens; [EMAIL-REMOVED]
Subject: Re: [css-d] loading of media css files
Hi Jens,
This just goes to show that you can't believe everything you read on the
Web (including this e-mail). Both authors are wishfully describing theory
rather than actual practice when it comes to browser behaviour and we all
know there's a big gap.
I know this seems basic but let me recap, because your two quoted sources
have over-simplified the issues. A browser (user agent) resides on a
processor. That processor will have one or more output devices (media)
attached, e.g. a screen; a small (handheld-type) screen; a printer; a
projector; a loudspeaker. The UA has to know (or assume) which devices are
(or may be) available and which it is capable of supporting through CSS
media types. Sometimes a UA can allow an output device to emulate another,
e.g. a screen can emulate a printer (in print-preview mode), whilst Opera
allows a screen to emulate a projector or a handheld-type screen.
The commonest example is a UA on a PC (or Mac) with a screen, a
print-preview facility and usually a printer. The UA has to load any print
stylesheets at the outset because the user could conceivably go off-line
before doing a print-preview or actually printing.
The mention of imported stylesheets (@import) is irrelevant here. A UA has
the option of downloading a stylesheet, depending on its media type(s),
whether it is <link>ed or @imported - it makes no difference.
So, in practice, it's desirable for a PC-based UA to download print
stylesheets unconditionally. By extension, Opera must also download any
projection or handheld stylesheets.
What *isn't* desirable is for a UA to download stylesheets for media types
that it can't support. For example, no PC-based UA except Opera should
download a handheld or projection stylesheet; whilst a handheld-based UA
should never download a screen-only stylesheet. Here's the bad news: they
do. For example, I've proved for myself that IE PC downloads handheld
stylesheets even though it can do nothing with them; whilst several
handheld-based UAs not only download screen-only stylesheets but wrongly
apply them to the handheld medium! What a mess.
The Wiki page may be of interest:-
http://css-discuss.incutio.com/?page=MediaStylesheets
Sorry I can't give you better news!
--
Jim Wilkinson
Cardiff, Wales UK
Opera e-mail client: http://www.opera.com/m2/
______________________________________________________________________
css-discuss [EMAIL-REMOVED]]
http://www.css-discuss.org/mailman/listinfo/css-d
List wiki/FAQ -- http://css-discuss.incutio.com/
Supported by evolt.org -- http://www.evolt.org/help_support_evolt/