>Psychtoolbox>PsychGLImageProcessing

rval = kPsychDontAutoResetOneshotFlags

Return a flag that you can pass as part of the flipFlags for a call to
Screen(‘Hookfunction’, windowPtr, ‘SetOneshotFlipFlags’, flipFlags);

This flag will prevent the one-shot flip flags from being automatically cleared
after execution of the next Screen(‘Flip’) operation. E.g., flags that won’t
get cleared after Flip are kPsychSkipWaitForFlipOnce, kPsychSkipSwapForFlipOnce,
kPsychSkipTimestampingForFlipOnce, kPsychSkipVsyncForFlipOnce.