Check if a previously scheduled asynchronous flip operation has completed (see
Screen AsyncFlipBegin? for help).
This command will check for completion on onscreen window “windowPtr”, then
return the result of the operation, ie. all the stimulus onset timestamps and
other diagnostic information. See help for Screen Flip? for explanation of the
returned info. If the operation hasn’t completed yet, it will return a
‘VBLTimestamp’ of zero and you’ll have to retry later. If you call this function
without having called ‘AsyncFlipBegin’ before, it will return the results of the
last completed flip, regardless if it was a synchronous Screen(‘Flip’) or an
asynchronous flip long finished ago.
Screen(‘AsyncFlipEnd’) provides a blocking version of this command – one that
pauses until the operation completes if the referenced operation hasn’t