
 ==============================================================================
    Environment variables which affect rendering with ACL Mesa Device Driver 
 ==============================================================================


- ACLOPT_HWIDX:
    <n>		- index number of hardware to be used for rendering.
		  If not defined or -1, the application exits after the
		  avaliable hardware gets listed.

    Which value to use as index could be simply find out by starting the
    rendering application - the list of available hardware would appear so you
    can gather the index number you need, define the ACLOPT_HWIDX and start
    application again.

- ACLOPT_RUNMODE:
    off		- turn off ACL driver
    win		- render into window
    full	- render fullscreen (DEFAULT)

- ACLOPT_VIDMODE:
    off		- use current screen resoulution (DEFAULT)
    on		- switch to the best resolutions (only fullscreen)

    This requires VIDMODE X extension, which alows you to switch the X screen
    between different resolutions, as defined in XF86Config. You would define
    a set of modelines for your favourite applications after which MLX can
    switch to the best fitting one. An example XF86Config could be found in
    mlx/misc directory.

- ACLOPT_XDGA:
    off		- usage of X DGA extension off
    on		- use X DGA to save X server screen (DEFAULT, only fullscreen)

    If you set this off, the default saving of X screen layout through usage of
    the DGA X extension is disabled and you'll probably have to repaint your X
    screen after rendering operation finished. If you, for example, want to
    play with some GLUT demos, you should disable X DGA, to be able to access
    GLUT menus. If you don't have DGA extension, X screen layout cannot be
    protected. Superuser rights for DGA are NOT REQUIRED anymore, because the
    DGA function which access /dev/mem is not used !

- ACLOPT_QUAKE:
    off		- quake hacks off (DEFAULT)
    on		- quake hacks on

- ACLOPT_DBUFF:
    bb		- bit-blit double buffering (DEFAULT)
    bp		- color bit-planes double buffering
    scr		- fullscreen double buffering (only in fullscreen mode)

    The slowest methode for double buffering is 'bitblit', but this method is
    supported on almost every graphic hardware. Faster than 'bitblit' would be
    'bitplane' double buffering, where the visibility of bitplanes in color
    buffer is switched on buffer swap event. This method doesn't require an
    extra off-screen VRAM, but the color formats which could be used with this
    method are rare. Last and fastest method is 'screen' double buffering,
    where the whole visible screen is switched with an alternate screen through
    single hardware command.

