http://www.libsdl.es/wiki/doku.php?id=sdl_api:sdl_envvars
SDL environment variables
=========================
last updated: 27 Sept 2001
The following applies to the CVS SDL (the 1.2 branch). This is unofficial,
and the semantics may vary, and some variables might go away.
AUDIODEV
The audio device to use, if SDL_PATH_DSP isn't set.
SDL_AUDIODRIVER
Selects the audio driver for SDL to use. Possible values, in the
order they are tried if this variable is not set:
openbsd (OpenBSD)
dsp (OSS /dev/dsp: Linux, Solaris, BSD etc)
alsa (Linux)
audio (Unix style /dev/audio: SunOS, Solaris etc)
AL (Irix)
artsc (ARTS audio daemon)
esd (esound audio daemon)
nas (NAS audio daemon)
dma (OSS /dev/dsp, using DMA)
dsound (Win32 DirectX)
waveout (Win32 WaveOut)
baudio (BeOS)
sndmgr (MacOS SoundManager)
paud (AIX)
AHI (Amiga)
disk (all; output to file)
SDL_CDROM
A colon-separated list of CD-ROM devices to use, in addition to
the standard devices (typically /dev/cdrom, platform-dependant).
SDL_DEBUG
If set, causes every call to SDL_SetError() to also print an
error message on stderr.
SDL_DISKAUDIOFILE
The name of the output file for the "disk" audio driver. If not
set, the name "sdlaudio.raw" is used.
SDL_DISKAUDIODELAY
For the "disk" audio driver, how long to wait (in ms) before writing
a full sound buffer. The default is 150 ms.
SDL_DSP_NOSELECT
For some audio drivers (alsa, paud, dma and dsp), don't use
select() but a timed method instead. May cure some audio problems,
or cause others.
SDL_ELO_MIN_X
SDL_ELO_MIN_Y
SDL_ELO_MAX_X
SDL_ELO_MAX_Y
Calibration values for the fbcon driver, for the Elographics
touchscreen controller. Default values are 400, 500, 3670, 3540
respectively.
SDL_FBACCEL
If set to 0, disable hardware acceleration in the linux fbcon driver.
SDL_FBDEV
Frame buffer device to use in the linux fbcon driver, instead of
/dev/fb0
SDL_FULLSCREEN_UPDATE
In the ps2gs driver, sets the SDL_ASYNCBLIT flag on the display
surface.
SDL_JOYSTICK_DEVICE
Joystick device to use in the linux joystick driver, in addition
to the usual: /dev/js*, /dev/input/event*, /dev/input/js*
SDL_LINUX_JOYSTICK
Special joystick configuration string for linux. The format is
"name numaxes numhats numballs"
where name is the name string of the joystick (possibly in single
quotes), and the rest are the number of axes, hats and balls
respectively.
SDL_MOUSE_RELATIVE
If set to 0, do not use mouse relative mode in X11. The default is
to use it if the mouse is hidden and input is grabbed.
SDL_MOUSEDEV
The mouse device to use for the linux fbcon driver. If not set,
SDL first tries to use GPM in repeater mode, then various other
devices (/dev/pcaux, /dev/adbmouse, /dev/mouse etc).
SDL_MOUSEDEV_IMPS2
If set, SDL will not try to auto-detect the IMPS/2 protocol of
a PS/2 mouse but use it right away. For the fbcon and ps2gs drivers.
SDL_MOUSEDRV
For the linux fbcon driver: if set to ELO, use the ELO touchscreen
controller as a pointer device
SDL_NO_RAWKBD
For the libvga driver: If set, do not attempt to put the keyboard
in raw mode.
SDL_NOMOUSE
If set, the linux fbcon driver will not use a mouse at all.
SDL_PATH_DSP
The audio device to use. If not set, SDL tries AUDIODEV and then
a platform-dependent default value (/dev/audio o Solaris,
/dev/dsp on Linux etc).
SDL_VIDEODRIVER
Selectes the video driver for SDL to use. Possible values, in the
order they are tried if this variable is not set:
x11
dga (the XFree86 DGA2)
nanox (Linux)
fbcon (Linux)
directfb (Linux)
ps2gs (Playstation 2)
ggi
vgl (BSD)
svgalib (Linux)
aalib
directx (Win32)
windib (Win32)
bwindow (BeOS)
toolbox (MacOS Classic)
DSp (MacOS Classic)
Quartz (MacOS X)
CGX (Amiga)
photon (QNX)
epoc (Epoc)
dummy
SDL_VIDEO_CENTERED
If set, tries to center the SDL window when running in X11 windowed
mode, or using the CyberGrafix driver.
SDL_VIDEO_GL_DRIVER
The openGL driver (shared library) to use for X11. Default is
libGL.so.1
SDL_VIDEO_X11_DGAMOUSE
With XFree86, enables use of DGA mouse if set.
SDL_VIDEO_X11_MOUSEACCEL
For X11, sets the mouse acceleration. The value should be a string
on the form: n/d/t
where n and d are the acceleration numerator/denumerators (so
mouse movement is accelerated by n/d), and t is the threshold
above which acceleration applies (counted as number of pixels
the mouse moves at once).
SDL_VIDEO_X11_NODIRECTCOLOR
If set, don't attempt to use DirectColor visuals even if they are
present. (SDL will use them otherwise for gamma correction).
This is needed with older X servers when using the XVideo extension.
SDL_VIDEO_X11_VISUALID
ID of an X11 visual to use, overriding SDL's default visual selection
algorithm. It can be in decimal or in hex (prefixed by 0x).
SDL_VIDEO_YUV_DIRECT
If set, display YUV overlay directly on the video surface if possible,
instead of on the surface passed to SDL_CreateYUVOverlay().
SDL_VIDEO_YUV_HWACCEL
If not set or set to a nonzero value, SDL will attempt to use
hardware YUV acceleration for video playback.
SDL_WINDOWID
For X11 or Win32, contains the ID number of the window to be used by
SDL instead of creating its own window. Either in decimal or
in hex (prefixed by 0x).
