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Projection media type in fullscreen browser mode

From: Aryeh Gregor <Simetrical+w3c@gmail.com>
Date: Mon, 17 Aug 2009 17:59:28 -0400
Message-ID: <7c2a12e20908171459l5b824c36tad3d6411f627706a@mail.gmail.com>
To: www-style@w3.org
Cc: Brion Vibber <brion@wikimedia.org>
Most or all browsers have a "fullscreen" mode, where the user can hit
F11 to make the browser and OS UI vanish and give the web page content
the whole screen.  I tried this simple test on Chrome, Opera, Firefox,
and IE:

<!doctype html>
<style media=screen>body { color: red }</style>
<style media=projection>body { text-decoration: underline }</style>

Chrome, Firefox, and IE all displayed the text "Hello" in red, both in
fullscreen mode and normal mode.  Opera displayed it red in normal
mode, but black and underlined in fullscreen mode.  In other words,
Opera (but only Opera) interprets full-screen mode as being projection
instead of screen.

The normative definition of "projection" in CSS 2.1 is:

"Intended for projected presentations, for example projectors. Please
consult the section on paged media for information about formatting
issues that are specific to paged media."

Since fullscreen mode on a desktop computer does not use a projector,
it doesn't meet the definition given here.  Projection is classified
as a paged media type, but AFAIK, fullscreen mode in all browsers (in
particular, including Opera) permits continuous scrolling, with no
paging.  The description suggests to me that "projection" is meant to
encompass only PowerPoint-style media, which are interactive but

Which of the browsers here, if any, are behaving incorrectly?
Currently there's no interoperability on this point.  If you want
stylesheets to work in all browsers consistently, you have to either
not give a media type, or use "screen,projection".

As an author, there is no situation I can think of in which I'd ever
want to use "screen" rather than "screen,projection" if Opera's
interpretation is correct.  I'd have users getting different
stylesheets if they just want to view the content fullscreen.
Googling "Opera fullscreen" suggests that a number of other web
authors/developers were surprised by this decision by Opera as well,
and expected screen stylesheets to be used in fullscreen mode.  This
suggests to me that Opera's interpretation is erroneous.

But in that case, when are browsers actually supposed to use the
projection media type rather than screen?  I assume they don't have
reliable access to the type of output device, and I doubt people want
things displaying differently on projectors anyway.  Perhaps the
projection type is unnecessary?
Received on Monday, 17 August 2009 22:00:07 UTC

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