glXWaitVideoSyncSGI(3G)

NAME
     glXWaitVideoSyncSGI - wait for vertical retrace


C SPECIFICATION
     int glXWaitVideoSyncSGI( int divisor,
                              int remainder,
                              unsigned int *count )


PARAMETERS
     divisor

     remainder  glXWaitVideoSyncSGI puts the calling process to sleep until
                the value of the vertical retrace counter modulo divisor
                equals remainder.


     count      Pointer to variable which receives the value of the vertical
                retrace counter when the calling process wakes up.


DESCRIPTION
     glXWaitVideoSyncSGI is part of the SGI_video_sync extension.  This
     extension provides a way to synchronize with the video frame rate of a
     monitor (in the case of an interlaced display, the synchronization is
     actually with the field rate).

     A vertical retrace precedes the display of each video frame.  The kernel
     maintains a 32-bit unsigned integer counter for each graphics pipe in the
     system.  This counter is initialized via the /usr/gfx/gfxinit command,
     and incremented upon each vertical retrace.  Since all the video output
     channels of a graphics pipe must be genlocked, one counter suffices for
     all the monitors driven by a pipe.

     A process can query or sleep on the counter of the graphics pipe
     associated with its current OpenGL rendering context, provided that the
     rendering context is direct.  (See glXCreateContext.)

     glXWaitVideoSyncSGI puts the calling process to sleep until the vertical
     retrace counter modulo divisor equals remainder.  When this condition is
     met it places the value of the vertical retrace counter in the location
     referenced by count and returns zero.

     If the current context is not direct, glXWaitVideoSyncSGI returns
     GLX_BAD_CONTEXT_SGI.  If divisor is less than or equal to zero,
     glXWaitVideoSyncSGI returns GLX_BAD_VALUE_SGI.  If remainder is less than
     zero, or greater than or equal to divisor, glXWaitVideoSyncSGI returns
     GLX_BAD_VALUE_SGI.
MACHINE DEPENDENCIES
     glXWaitVideoSyncSGI is not supported on Personal Iris or VGX and VGXT
     systems.


SEE ALSO
     glXGetVideoSyncSGI, glXCreateContext, glXQueryVersion, glGetString