C SPECIFICATION

       int glXGetConfig( Display *dpy,
                         XVisualInfo *visua )

PARAMETERS

       dpy    Specifies the connection to the X server.

       visua  Specifies  the  visual  to  be  queried.   It is a pointer to an
              XVisualInfo structure, not a visual ID or a pointer to a Visual.

       _param3
              Specifies the visual attribute to be returned.

       _param4
              Returns the requested value.

DESCRIPTION

       glXGetConfig  sets  _param4  to  the  _param3  value  of windows or GLX
       pixmaps created with respect to visua.  glXGetConfig returns  an  error
       code if it fails for any reason.  Otherwise, zero is returned.

       _param3 is one of the following:


       GLX_USE_GL            True  if  OpenGL  rendering  is supported by this
                             visual, False otherwise.

       GLX_BUFFER_SIZE       Number of bits per color buffer.  For RGBA  visu-
                             als,  GLX_BUFFER_SIZE is the sum of GLX_RED_SIZE,
                             GLX_GREEN_SIZE,        GLX_BLUE_SIZE,         and
                             GLX_ALPHA_SIZE.    For   color   index   visuals,
                             GLX_BUFFER_SIZE is the size of the color indexes.

       GLX_LEVEL             Frame  buffer level of the visual.  Level zero is
                             the default frame buffer.  Positive levels corre-
                             spond  to  frame buffers that overlay the default
                             buffer, and negative levels correspond  to  frame
                             buffers that underlay the default buffer.

       GLX_RGBA              True if color buffers store red, green, blue, and
                             alpha values.  False if they store color indexes.

       GLX_DOUBLEBUFFER      True  if  color buffers exist in front/back pairs
                             that can be swapped, False otherwise.

       GLX_STEREO            True if color buffers exist in left/right  pairs,
                             False otherwise.

       GLX_AUX_BUFFERS       Number of auxiliary color buffers that are avail-
                             able.  Zero indicates  that  no  auxiliary  color

       GLX_DEPTH_SIZE        Number of bits in the depth buffer.

       GLX_STENCIL_SIZE      Number of bits in the stencil buffer.

       GLX_ACCUM_RED_SIZE    Number  of bits of red stored in the accumulation
                             buffer.

       GLX_ACCUM_GREEN_SIZE  Number of bits of green stored in  the  accumula-
                             tion buffer.

       GLX_ACCUM_BLUE_SIZE   Number of bits of blue stored in the accumulation
                             buffer.

       GLX_ACCUM_ALPHA_SIZE  Number of bits of alpha stored in  the  accumula-
                             tion buffer.

       The  X  protocol allows a single visual ID to be instantiated with dif-
       ferent numbers of bits per pixel.  Windows or GLX pixmaps that will  be
       rendered with OpenGL, however, must be instantiated with a color buffer
       depth of GLX_BUFFER_SIZE.

       Although a GLX implementation can export many visuals that  support  GL
       rendering,  it  must support at least one RGBA visual. This visual must
       have at least one color buffer, a stencil buffer of at least 1  bit,  a
       depth  buffer  of  at least 12 bits, and an accumulation buffer.  Alpha
       bitplanes are optional in this visual.  However, its color buffer  size
       must  be  as  great  as  that  of  the  deepest TrueColor, DirectColor,
       PseudoColor, or StaticColor visual supported on level zero, and it must
       itself be made available on level zero.

       In  addition,  if  the  X  server  exports a PseudoColor or StaticColor
       visual on framebuffer level 0, a color index visual is also required on
       that  level.   It must have at least one color buffer, a stencil buffer
       of at least 1 bit, and a depth buffer of at least 12 bits.  This visual
       must  have  as  many  color  bitplanes  as  the  deepest PseudoColor or
       StaticColor visual supported on level 0.

       Applications are best written to select the visual  that  most  closely
       meets  their requirements.  Creating windows or GLX pixmaps with unnec-
       essary buffers can result in reduced rendering performance as  well  as
       poor resource allocation.

NOTES

       XVisualInfo  is  defined  in  Xutil.h.  It is a structure that includes
       visual, visualID, screen, and depth elements.

ERRORS

       GLX_NO_EXTENSION is returned if dpy does not support the GLX extension.

       GLX_BAD_SCREEN  is  returned if the screen of visua does not correspond
       to a screen.