glFlush - force execution of GL commands in finite time

glFlush
	glFlush() -> None

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 GL	commands is complete.

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

glFinish