NAME
	  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.
	  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 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.	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
				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 instantiated
	  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 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 unnecessary 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 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