glXGetConfig

GLXGETCONFIG()						       GLXGETCONFIG()



NAME
       glXGetConfig - return information about GLX visuals


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

       delim $$

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.  Otherwise, zero is returned.

       attrib 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	 cor-
			     respond   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
			     available.	  Zero	indicates  that	 no auxiliary
			     color buffers exist.

       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 accumula-
			     tion buffer.

       GLX_ACCUM_BLUE_SIZE   Number of bits of blue stored in  the  accumula-
			     tion 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,	Pseu-
       doColor,	 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  Pseudo-
       Color 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 exten-
       sion.

       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




							       GLXGETCONFIG()