don't force double buffering

[sdl_omap.git] / README.OMAP

(some) OMAP hardware support for SDL
by notaz (notasas@gmail.com)


About
-----

This is a quick SDL driver to make use of some OMAP features, namely double
buffering and hardware scaler.

The backstory of this is that SDL on Pandora console was suffering from tearing
and stuttering problems because SDL default x11 driver doesn't work that well
there. Almost 6 months have passed after pandora's release, no improved
SDL versions appeared (not blaming anyone here, pandora's availability was low
and there where were several SDL improvement in the works though). This
encouraged me to create this quick version until something better appears
(if ever).

Although this was created for pandora, there is nothing preventing this to work
on other OMAP platforms as well (well, nothing intentional at least).


Usage / environment
-------------------

To enable this driver, SDL_VIDEODRIVER environment variable must be set to
"omapdss". It can be set by calling setenv() in the code, but it's better to
just set it in launcher script so that it can be changed easily without
recompiling as needed:
---
#!/bin/sh
export SDL_VIDEODRIVER=omapdss
./your_program_here
---

Other environment variables:

SDL_OMAP_LAYER_SIZE:
  Output layer size. Regardless what you set with SDL_SetVideoMode(), output
  will be scaled to this size using hardware. Valid values:
    "WxH", for example "640x480"
    "fullscreen" to cover whole screen.

SDL_OMAP_VSYNC:
  Enables waiting for vertical sync on SDL_Flip() calls.
  Set to "1" to enable, "0" to disable.

SDL_OMAP_DEFAULT_MODE:
  If the app doesn't specify resolution in SDL_SetVideoMode(), then use this.
  Should be specified in "WxH" format, for example "640x480".

SDL_OMAP_FORCE_DOUBLEBUF:
  This can force double buffering to on, which can help to eliminate tearing.
  Note that if app isn't updating whole buffer each frame, it will glitch.
  This is the same as specifying SDL_DOUBLEBUF to SDL_SetVideoMode.


Config file
-----------

Optionally a file named "omapsdl.cfg" can be created in the game's working
directory. It has lower priority than environment variables, and has these
options (only when omapdss driver is active):

# same as SDL_OMAP_VSYNC
force_vsync = 1/0

# same as SDL_OMAP_FORCE_DOUBLEBUF
force_doublebuf = 1/0

# can be used to bind a key to SDL keysym, good for quick ports.
# Example:
# bind ev_home = sdlk_space
bind ev_<evdev_key> = <sdl_key>


Source
------

Available at git://notaz.gp2x.de/~notaz/sdl_omap.git