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Re: Projection media type in fullscreen browser mode

From: Aryeh Gregor <Simetrical+w3c@gmail.com>
Date: Tue, 18 Aug 2009 16:55:39 -0400
Message-ID: <7c2a12e20908181355s79880a7ahbe5c26fb3dc0043f@mail.gmail.com>
To: Øyvind Stenhaug <oyvinds@opera.com>, Bert Bos <bert@w3.org>
Cc: www-style@w3.org
On Tue, Aug 18, 2009 at 1:04 PM, Øyvind Stenhaug<oyvinds@opera.com> wrote:
> I suppose it could be described as "falling back" to screen rendering if no
> projection style is available. The standard does not seem to disallow this,
> though I can see how it could be unexpected.

>From that perspective, it would be similar to Opera Mobile trying to
use screen stylesheets if no handheld stylesheets are given.  That
does sound reasonable.  On the other hand, if it results in authors
feeling like they should just tack ",projection" onto every screen
stylesheet, something is wrong.

> Well, in this case we would be in projection mode, so it wouldn't really be
> appropriate to add styles if they are not intended to be used for
> projection. Either that, or the projection rules that were added in the
> first place were wrong or insufficient.
> However, it might be a good idea for the browser to allow the user a choice
> between just "regular" full-screen and projection mode. I've raised this to
> our desktop team as a possible improvement.

All I can say is that when we stopped serving the stylesheets as
"screen,projection", we quickly got a bug filed by an Opera user who
complained that stylesheets stopped working in full-screen mode:


We're now forced to append ",projection" everywhere, despite the fact
that we don't actually intend for the output to be used for
projectors, and haven't tested our stylesheets on projectors, and are
serving exactly the same CSS for screen and projection.

On Tue, Aug 18, 2009 at 2:27 PM, Bert Bos<bert@w3.org> wrote:
> Maybe what is confusing is that Opera chose to call it "Full Screen" in
> the menu, while it is called "projection" in HTML. It is in fact doing
> the same as "Print Preview," "Small Screen" and "User Mode": switch to
> a different mode of interacting with the document and perhaps to a
> different style sheet as well. ("Small Screen" corresponds to
> the 'handheld' mode.)
> Opera has the widest choice of modes nowadays, but it wasn't the first
> to provide a mode switch: that was MacIE. (But Opera wins with its "Fit
> to Width" mode: this mode is enough to make many fixed-width pages
> flexible again, without having to go as far as "User Mode." When I use
> Opera, it is often because of this feature.)

I agree that these modes are very nice, and haven't run into any
problems with them as a web developer.  I did try contacting an Opera
developer first, but got no response (maybe he was away or lost my
e-mail), so I thought I'd solicit broader comment on whether this
behavior complies with the spec, at least.  I'd be happy to continue
this discussion in some Opera-specific forum (a bug tracker or private
e-mail or whatever) if people think that's more appropriate.

> No, quite the opposite. Only the user knows if he wants to read the page
> on his phone, on paper, on a computer screen, or projected.

Yes, but only the author knows whether he's made a special stylesheet
that he intends to be used for projection, or whether he only has a
screen stylesheet available.  In the latter case, the browser could
intelligently adapt the screen stylesheet to projection (which is what
Opera in fact does).

The problem seems to be something like:

1) Someone creates a stylesheet with media type "screen,projection"
for some reason, maybe copy-pasted from somewhere, when he really
means "screen".

2) Someone else (or the same person) tries adding a stylesheet to the
same page, with media type "screen".

3) Users complain that the second stylesheet doesn't work in Opera
full-screen mode.

4) The stylesheet is changed to be served as "screen,projection".
Return to (1).

I guess it's not a problem if (1) doesn't happen.  I'll see if I can
fix up MediaWiki here to not serve projection stylesheets anywhere.
But the problem isn't unique to us, as Googling shows:


The second link says Eric Meyer is in the habit of using
"screen,projection" for all his stylesheets for exactly this reason,
even if they're really only intended or tested for screen use.

(Do older versions of Opera not use screen stylesheets at all in
full-screen mode?  Some of the discussions I've found suggest that.
That would explain how (1) came about in the first place.)

> The author
> can suggest different styles that are adapted for the different media,
> but it is the user who chooses. It would he bad if upon loading a page
> I get a message "Sorry, this page can only be projected" or worse: it
> automatically turns my projector on...

Of course nothing like that should happen.  If the author indicates
the page is not intended to be projected, the browser is still free to
try adapting it for projection in some nonstandard way.
Received on Tuesday, 18 August 2009 21:00:43 UTC

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