Psychtoolbox>Screen.{mex*} subfunction

Tell Psychtoolbox that no further drawing commands will be issued to ‘windowPtr’
before the next Screen(‘Flip’) or Screen(‘AsyncFlipBegin’) command.

This is a hint that allows to optimize drawing performance on some occasions.
Don’t issue this command multiple times between a Flip, it will degrade
performance or even cause undefined stimulus display!

You must provide the same value for ‘dontclear’ flag that you’re going to pass
to the following Flip command, if you pass such an optional flag to the Flip

You can time the execution of all drawing commands between the most recent Flip
and this command by setting the optional flag sync=1. In that case, telapsed is
the elapsed time at drawing completion. Don’t set the sync - Flag for real
experiments, it will degrade performance!

Some recent graphics cards provide a more fine-grained way to measure the time
spent drawing and processing your stimulus. See the help of ‘Screen
GetWindowInfo?’ about ‘infoType’ settings 5 and 6 on how to use that mechanism.
That method also has the advantage of measuring precise without degrading
overall performance.

###See also: Flip AsyncFlipBegin