glPollAsyncSGIX(3G)	       OpenGL Reference		   glPollAsyncSGIX(3G)

NAME    [Toc]    [Back]

     glPollAsyncSGIX - poll for	completion of an asynchronous command

C SPECIFICATION    [Toc]    [Back]

     GLint glPollAsyncSGIX( GLuint *markerp )

PARAMETERS    [Toc]    [Back]

     markerp  Returns a	marker for a completed asynchronous command.

DESCRIPTION    [Toc]    [Back]

     glPollAsyncSGIX is	part of	the SGIX_async extension.  This	extension
     provides a	framework within which particular sets of OpenGL commands can
     become "asynchronous" via specific	further	OpenGL extensions.  Currently
     the SGIX_async_pixel extension is the only	such defined extension.

     Asynchronous commands are commands	that may complete out-of-order with
     respect to	other OpenGL commands.	An asynchronous	command	samples	the
     OpenGL state vector when it is issued.  The sampled state includes	the
     results from the complete execution of all	synchronous (normal) commands
     issued prior to the asynchronous command.	However, the results of	an
     asynchronous command (state changes or framebuffer	updates) are not
     necessarily committed in order.  An asynchronous command may commit its
     results any time after the	completion of all synchronous commands issued
     prior to the asynchronous command.	 An implementation may choose to
     execute asynchronous commands in parallel with subsequent commands	or at
     some convenient time in the future.

     Implementations of	asynchronous commands may also be non-blocking.	 For
     example, a	non-blocking query command returns control to the program
     immediately rather	than stalling the program until	the results of the
     query are available.

     Note that this language allows any	particular asynchronous	command	to
     behave exactly as if it were not asynchronous, if the implementation
     chooses.

     glPollAsyncSGIX returns 1 when an asynchronous command has	completed; in
     this case it writes the marker associated with the	completed command into
     the integer referred to by	markerp.  If there are no pending asynchronous
     commands, or if there are pending asynchronous commands but none have
     completed,	glPollAsyncSGIX	returns	0 immediately and does not modify the
     integer referred to by markerp.

     Once OpenGL has reported the completion of	an asynchronous	command	via
     either glFinishAsyncSGIX or glPollAsyncSGIX, the completion status	of the
     command will not be reported again.  If several commands have the same
     marker associated with them, the completion status	of each	command	will
     be	reported separately, although these reports will be indistinguishable.
     The order in which	asynchronous commands are reported is undefined.




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glPollAsyncSGIX(3G)	       OpenGL Reference		   glPollAsyncSGIX(3G)



     A program may guarantee that all outstanding asynchronous commands	have
     completed by calling glFinish.  A call to glFinish	does not cause the
     completion	status of outstanding commands to be reported, so subsequent
     calls to glFinishAsyncSGIX	or glPollAsyncSGIX will	report the status of
     such commands.

ERRORS    [Toc]    [Back]

     GL_INVALID_OPERATION is generated if glPollAsyncSGIX is executed between
     the execution of glBegin and the corresponding execution of glEnd.


MACHINE	DEPENDENCIES
     The SGIX_async and	SGIX_async_pixel extensions are	implemented only on
     Octane2 VPro systems.

SEE ALSO    [Toc]    [Back]

     glAsyncMarkerSGIX,	glDeleteAsyncMarkersSGIX, glFinishAsyncSGIX,
     glGenAsyncMarkersSGIX, glIsAsyncMarkerSGIX, glDrawPixels, glReadPixels,
     glTexImage1D, glTexImage2D, glTexImage3D


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