glXGetConfig - return information about GLX visuals



C SPECIFICATION

       int glXGetConfig( Display *dpy,
                         XVisualInfo *vis,
                         int attrib,
                         int *value )



PARAMETERS

       dpy     Specifies the connection to the X server.

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

       attrib  Specifies the visual attribute to be returned.

       value   Returns the requested value.


DESCRIPTION

       glXGetConfig  sets value to the attrib value of windows or
       GLX pixmaps created with  respect  to  vis.   glXGetConfig
       returns  an error code if it fails for any reason.  Other-
       wise, zero is returned.

       attrib is one of the following:


       GLX_USE_GL            True if  OpenGL  rendering  is  sup-
                             ported  by this visual, False other-
                             wise.

       GLX_BUFFER_SIZE       Number of  bits  per  color  buffer.
                             For RGBA visuals, 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  correspond
                             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.

       GLX_RED_SIZE          Number of bits of red stored in each
                             color buffer.  Undefined if GLX_RGBA
                             is False.

       GLX_GREEN_SIZE        Number of bits of  green  stored  in
                             each  color  buffer.   Undefined  if
                             GLX_RGBA is False.

       GLX_BLUE_SIZE         Number of bits  of  blue  stored  in
                             each  color  buffer.   Undefined  if
                             GLX_RGBA is False.

       GLX_ALPHA_SIZE        Number of bits of  alpha  stored  in
                             each  color  buffer.   Undefined  if
                             GLX_RGBA is False.

       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 accumulation 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 accumulation buffer.

       The X protocol allows a single visual ID to  be  instanti-
       ated with different 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  bit-
       planes  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 avail-
       able on level zero.

       In  addition,  if  the  X  server exports a PseudoColor or
       StaticColor visual on framebuffer level 0, a  color  index
       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 vis does not
       correspond to a screen.

       GLX_BAD_ATTRIBUTE is returned if attrib is not a valid GLX
       attribute.

       GLX_BAD_VISUAL  is returned if vis doesn't support GLX and
       an attribute other than GLX_USE_GL is requested.


SEE ALSO

       glXChooseVisual, glXCreateContext




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