OpenGL man pages
glFlush - force execution of GL commands in finite time
void glFlush( void )
Different GL implementations buffer commands in several different
locations, including network buffers and the graphics accelerator itself.
glFlush empties all of these buffers, causing all issued commands to be
executed as quickly as they are accepted by the actual rendering engine.
Though this execution may not be completed in any particular time period,
it does complete in finite time.
Because any GL program might be executed over a network, or on an
accelerator that buffers commands, all programs should call glFlush
whenever they count on having all of their previously issued commands
completed. For example, call glFlush before waiting for user input that
depends on the generated image.
glFlush can return at any time. It does not wait until the execution of
all previously issued OpenGL commands is complete.
GL_INVALID_OPERATION is generated if glFlush is executed between the
execution of glBegin and the corresponding execution of glEnd.
Fri Dec 6 11:18:03 EST 1996
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