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GLXCHOOSEVISUAL()                                            GLXCHOOSEVISUAL()




NAME

       glXChooseVisual - return a visual that matches specified attributes



C SPECIFICATION

       XVisualInfo* glXChooseVisual( Display *dpy,
                                     int screen,
                                     int *attribList )

       delim $$


PARAMETERS

       dpy         Specifies the connection to the X server.

       screen      Specifies the screen number.

       attribList  Specifies   a   list  of  boolean  attributes  and  integer
                   attribute/value pairs.  The last attribute must be None.


DESCRIPTION

       glXChooseVisual returns a pointer to an XVisualInfo structure  describ-
       ing  the  visual  that best meets a minimum specification.  The boolean
       GLX attributes of the visual that is returned will match the  specified
       values,  and  the integer GLX attributes will meet or exceed the speci-
       fied minimum values.  If all  other  attributes  are  equivalent,  then
       TrueColor  and  PseudoColor  visuals have priority over DirectColor and
       StaticColor visuals, respectively.  If  no  conforming  visual  exists,
       NULL  is  returned.   To  free  the data returned by this function, use
       XFree.

       All boolean GLX attributes default to False  except  GLX_USE_GL,  which
       defaults to True.  All integer GLX attributes default to zero.  Default
       specifications are superseded by  attributes  included  in  attribList.
       Boolean  attributes  included  in attribList are understood to be True.
       Integer attributes and enumerated type attributes are followed  immedi-
       ately  by the corresponding desired or minimum value.  The list must be
       terminated with None.

       The interpretations of the various GLX visual attributes  are  as  fol-
       lows:

       GLX_USE_GL            Ignored.   Only visuals that can be rendered with
                             GLX are considered.

       GLX_BUFFER_SIZE       Must be followed by a  nonnegative  integer  that
                             indicates  the  desired  color index buffer size.
                             The smallest index buffer of at least the  speci-
                             fied  size  is preferred.  Ignored if GLX_RGBA is
                             asserted.

       GLX_LEVEL             Must be followed by an integer buffer-level spec-
                             ification.    This   specification   is   honored
                             exactly.  Buffer level zero  corresponds  to  the
                             main  frame  buffer of the display.  Buffer level
                             one is the first overlay frame buffer, level  two
                             the second overlay frame buffer, and so on.  Neg-
                             ative buffer levels correspond to underlay  frame
                             buffers.

       GLX_RGBA              If  present, only TrueColor and DirectColor visu-
                             als are considered.  Otherwise, only  PseudoColor
                             and StaticColor visuals are considered.

       GLX_DOUBLEBUFFER      If present, only double-buffered visuals are con-
                             sidered.   Otherwise, only single-buffered  visu-
                             als are considered.

       GLX_STEREO            If  present,  only stereo visuals are considered.
                             Otherwise, only monoscopic  visuals  are  consid-
                             ered.

       GLX_AUX_BUFFERS       Must  be  followed  by a nonnegative integer that
                             indicates  the  desired   number   of   auxiliary
                             buffers.   Visuals  with  the  smallest number of
                             auxiliary buffers that meets or exceeds the spec-
                             ified number are preferred.

       GLX_RED_SIZE          Must  be  followed  by a nonnegative minimum size
                             specification.  If this value is zero, the small-
                             est  available  red  buffer is preferred.  Other-
                             wise, the largest  available  red  buffer  of  at
                             least the minimum size is preferred.

       GLX_GREEN_SIZE        Must  be  followed  by a nonnegative minimum size
                             specification.  If this value is zero, the small-
                             est  available green buffer is preferred.  Other-
                             wise, the largest available green  buffer  of  at
                             least the minimum size is preferred.

       GLX_BLUE_SIZE         Must  be  followed  by a nonnegative minimum size
                             specification.  If this value is zero, the small-
                             est  available  blue buffer is preferred.  Other-
                             wise, the largest available  blue  buffer  of  at
                             least the minimum size is preferred.

       GLX_ALPHA_SIZE        Must  be  followed  by a nonnegative minimum size
                             specification.  If this value is zero, the small-
                             est  available alpha buffer is preferred.  Other-
                             wise, the largest available alpha  buffer  of  at
                             least the minimum size is preferred.

       GLX_DEPTH_SIZE        Must  be  followed  by a nonnegative minimum size
                             specification.  If this value  is  zero,  visuals
                             with  no  depth buffer are preferred.  Otherwise,
                             the largest available depth buffer  of  at  least
                             the minimum size is preferred.

       GLX_STENCIL_SIZE      Must  be  followed  by a nonnegative integer that
                             indicates the  desired  number  of  stencil  bit-
                             planes.   The smallest stencil buffer of at least
                             the specified size is preferred.  If the  desired
                             value is zero, visuals with no stencil buffer are
                             preferred.

       GLX_ACCUM_RED_SIZE    Must be followed by a  nonnegative  minimum  size
                             specification.   If  this  value is zero, visuals
                             with no red accumulation  buffer  are  preferred.
                             Otherwise,  the largest possible red accumulation
                             buffer of at least the minimum size is preferred.

       GLX_ACCUM_GREEN_SIZE  Must  be  followed  by a nonnegative minimum size
                             specification.  If this value  is  zero,  visuals
                             with  no green accumulation buffer are preferred.
                             Otherwise, the largest possible  green  accumula-
                             tion  buffer of at least the minimum size is pre-
                             ferred.

       GLX_ACCUM_BLUE_SIZE   Must be followed by a  nonnegative  minimum  size
                             specification.   If  this  value is zero, visuals
                             with no blue accumulation buffer  are  preferred.
                             Otherwise, the largest possible blue accumulation
                             buffer of at least the minimum size is preferred.

       GLX_ACCUM_ALPHA_SIZE  Must  be  followed  by a nonnegative minimum size
                             specification.  If this value  is  zero,  visuals
                             with  no alpha accumulation buffer are preferred.
                             Otherwise, the largest possible  alpha  accumula-
                             tion  buffer of at least the minimum size is pre-
                             ferred.


EXAMPLES

       attribList =
                   {GLX_RGBA,    GLX_RED_SIZE,    4,    GLX_GREEN_SIZE,     4,
                   GLX_BLUE_SIZE, 4, None};

       Specifies  a single-buffered RGB visual in the normal frame buffer, not
       an overlay or underlay buffer.  The returned visual supports  at  least
       four  bits each of red, green, and blue, and possibly no bits of alpha.
       It does not support color index mode, double-buffering, or stereo  dis-
       play.   It  may  or may not have one or more auxiliary color buffers, a
       depth buffer, a stencil buffer, or an accumulation buffer.


NOTES

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

       glXChooseVisual  is  implemented  as  a  client-side utility using only
       XGetVisualInfo and glXGetConfig.  Calls to these two  routines  can  be
       used  to  implement  selection  algorithms  other  than the generic one
       implemented by glXChooseVisual.

       GLX implementers are strongly discouraged,  but  not  proscribed,  from
       changing  the  selection algorithm used by glXChooseVisual.  Therefore,
       selections may change  from  release  to  release  of  the  client-side
       library.

       There  is  no  direct filter for picking only visuals that support GLX-
       Pixmaps.  GLXPixmaps are supported for visuals whose GLX_BUFFER_SIZE is
       one of the pixmap depths supported by the X server.


ERRORS

       NULL is returned if an undefined GLX attribute is encountered in attri-
       bList.


SEE ALSO

       glXCreateContext(3), glXGetConfig(3)



                                                             GLXCHOOSEVISUAL()

Mac OS X 10.4 X11 - Generated Sat Apr 30 05:14:12 CDT 2005
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