Exclusive Fullscreen Mode

[Roland Plüss]

On 09/06/2010 08:17 PM, Tomas Carnecky wrote:
> On 9/6/10 5:53 PM, Roland Plüss wrote:
>>  I tried searching on the Internet for informations on how to take over
>> the screen using Xlib. I think here about fullscreen exclusive access
>> like for example SDLMAME does it. I stumbled so far though only on one
>> single mentioning of an Xlib call which should allow switching a window
>> into a FullscreenExclusiveMode. I could though find nothing about such a
>> call nor this FullscreenExclusiveMode. Has anybody an idea what this
>> FullscreenExclusiveMode could be or in general how one can make a window
>> take over the entire screen?
> X11 doesn't have a 'fullscreen' mode like windows. What you have to do
> is: resize and move the window so that it covers the whole screen.
> However, some window managers won't let you place windows wherever you
> want (because they also want to draw window decorations etc), so the
> modern way to fullscreen your application is to tell the window manager.
> The window manager will then resize your window and make sure it's on
> top of all other windows. You can do that by setting _NET_WM_STATE to
> _NET_WM_STATE_FULLSCREEN. See [1] and/or google 'ewmh fullscreen' or
> variations thereof.
>
> tom
>
> [1]: http://standards.freedesktop.org/wm-spec/wm-spec-latest.html#id2551694
That sounds like a plan. Thanks for the link there. I've got two
questions left about the topic of fullscreen with X.

1) What about changing resolution?
SDLMAME as far as I know changes the resolution while full screen and
some games do this too (typically commercial ones like UT*, Quake* and
company). I read somewhere that only root is allowed to change
resolution on-the-fly. Another place states only resolutions in the
xorg.conf are valid. What's the ground truth in this case? Can one
change resolution dynamically from a client application?

2) What about performance while fullscreen?
I'm here testing on a KDE4 system with Compositing enabled to test for a
typical case found at actual users. I notice that performance tends to
dwindle down a lot with Compositing enabled. While fullscreen
compositing would not really be required. According to the text in [1]
though the window is just placed on top of all others so compositing
would still be running. So has this fullscreen an influence on
performance? Do WMs like KDE switch compositing while something is
fullscreen or stays it the same?

Quite some questions but it would be interesting to know (if somebody
knows here that is).

-- 
Mit freundlichen Grüssen
Plüss Roland

Leader und Head Programmer
- Game: Epsylon ( http://www.indiedb.com/games/epsylon ,
http://epsylon.rptd.ch )
- Game Engine: Drag[en]gine ( http://www.indiedb.com/engines/dragengine
, http://dragengine.rptd.ch )
- Normal Map Generator: DENormGen ( http://epsylon.rptd.ch/denormgen.php
) and others

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