Linux dual monitor: Don't stretch fullscreen over all monitors in SDL games (psychonauts, ftl, superhexagon)

[EDIT] Some time after I wrote this, I also found this article:
http://www.maketecheasier.com/run-fullscreen-games-in-linux-with-dual-monitors/
which is a lot nicer written.

Hello everybody!

I'm using two monitors on my Linux machine: The 13" 1366x768px inbuilt one of my laptop and my 24" full hd monitor. I don't need to say, that those do not really match to display one application over both of them. Unfortunately though, many games based on the well known sdl library try to do exactly this: When in fullscreen, they only offer me resolutions like "3286x1080" after the notebook's resolution (nothing in between). When opening in windowed mode, they calculate the middle of the screen by taking both screens into consideration, thus opening between them.
All I want to do, though, is having fullscreen games opening with full hd resolution on my external monitor, and windowed games in the middle of just this monitor.

I was quite happy lately, when I discovered that wine/crossover will open all windows on the external monitor if I tell xrandr, that it is my "--primary" screen, using "xrandr --output HDMI-0 --primary". This doesn't work for native, sdl-based games of course, although it kind of fits in here, so I thought to mention it.

So, today I got my bluetooth controller and I really wanted to play psychonauts with it. It, too, featured the said issue, and this time I just didn't want to give up. After some heavy googling, I finally came up with the SDL_VIDEO_FULLSCREEN_HEAD variable mentioned HERE (archwiki ftw!), and -thank god- it worked as expected. So for you it is:

$: SDL_VIDEO_FULLSCREEN_HEAD=0 ~/.steam/root/SteamApps/common/Psychonauts/Psychonauts

I hope this helps someone out there. I wish happy gaming.
Sincerely

suluke

Related: 
A topic on a mailing list also discussing a similar solution can be found here: http://icculus.org/pipermail/psychonauts/2012-June/000000.html

XFCE suddenly not applying any themes any more

Hello people out there!

Recently I faced some strange behaviour with my Xfce 4 (.10) after I had plugged in a beamer. On first login after startup it wouldn't apply the window theme I set, nor would it use my preferred icon theme.
Also, setting the theme again with the xfce settings dialog (xfce4-appearance-settings) would not have any effect. Logging out and logging in again solved the issue temporarily, though.

Usually I already use a dual monitor setup and the beamer just switched place with my desktop monitor. So this was obviously a dual or multi monitor problem, and the first place I looked in for error messages was ~/.xsession-errors. There I encountered a line saying:

"The program 'xfsettingsd' received an X Window System error"

So the error occured in xfsettingsd, which also explained why using the settings dialogs hadn't had any effect later on.
Luckily, google would directly lead me to https://bugzilla.redhat.com/show_bug.cgi?id=867455 when searching for this error message, where I found the solution:
By simply deleting

.config/xfce4/xfconf/xfce-perchannel-xml/displays.xml

I was able to fix the error. As mentioned in the bug report, the file was recreated. Nevertheless I recommend to backup the file, since one never knows if such a file contains additional configuration markup you would maybe want to have access to later.

I hope this information can help somebody. If you want to thank me or want me to add something or maybe have any suggestions for improvements, I would be glad if you left me a comment.

Until then, see you soon

suluke