Screen('Flip')

Psychtoolbox › Screen.{mex*,dll} subfunction

Flip front and back display surfaces in sync with vertical retrace and return
timestamps. "windowPtr" is the id of the onscreen window whose content should be
shown at flip time. "when" specifies when to flip: If set to zero (default), it
will flip on the next possible retrace.If set to a value when > 0, it will flip
at the first retrace after system time 'when' has been reached."dontclear" If
set to 1, flip will not clear the framebuffer after Flip - this allows
incremental drawing of stimuli. The default is zero, which will clear the
framebuffer to background color after each flip. A value of 2 will prevent Flip
from doing anything to the framebuffer after flip. This leaves the job of
setting up the buffer to you - the framebuffer is in an undefined state after
flip. "dontsync" If set to zero (default), Flip will sync to the vertical
retrace and will pause Matlabs executionuntil the Flip has happened. If set to
1, Flip will still synchronize stimulus onset to the vertical retrace, butwill
*not* wait for the flip to happen: Flip returns immediately and all returned
timestamps are invalid. A value of 2will cause Flip to show the stimulus
*immediately* without waiting/syncing to the vertical retrace. "multiflip"
defaults to zero: If set to a value greater than zero, Flip will flip *all*
onscreen windows instead of just the specified one. This allows to synchronize
stimulus onset on multiple displays, e.g., for multidisplay stereo setups or
haploscopes. You need to (somehow) synchronize all attached displays for this to
operate tear-free. Flip (optionally) returns a high-precision estimate of the
system time (in seconds) when the actual flip has happened in the return
argument 'VBLTimestamp'. An estimate of Stimulus-onset time is returned in
'StimulusOnsetTime'. Beampos is the position of the monitor scanning beam when
the time measurement was taken (useful for correctness tests). FlipTimestamp is
a timestamp taken at the end of Flip's execution. Use the difference between
FlipTimestamp and VBLTimestamp to get an estimate of how long Flips execution
takes. This is useful to get a feeling for the timing error if you try to sync
Matlabs execution to the retrace, e.g., for triggering acquisition devices like
EEG, fMRI, or for starting playback of a sound. "Missed" indicates if the
requested presentation deadline for your stimulus has been missed. A negative
value means that dead- lines have been satisfied. Positive values indicate a
deadline-miss. The automatic detection of deadline-miss is not fool-proof - it
can report false positives and also false negatives, although it should work
fairly well with most experimental setups. If you are picky about timing, please
use the provided timestamps or additional methods to exercise your own tests.