MirOS Manual: glXGetConfig(3)


GLXGETCONFIG()      UNIX Programmer's Manual       GLXGETCONFIG()

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.

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GLXGETCONFIG()      UNIX Programmer's Manual       GLXGETCONFIG()

     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

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GLXGETCONFIG()      UNIX Programmer's Manual       GLXGETCONFIG()

     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 Sta-
     ticColor 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 Sta-
     ticColor 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

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