OpenSesame non-slip timing

# Specify how long you want the trial the last. Make sure that trials do not last
# longer!
trial_duration = 3000

# Get a trial id
trial_id = self.get_check('trial_id', default=0)

# For the first trial, just note the time
if trial_id == 0:
    exp.set('first_trial_timestamp', self.time())
    time_to_pad = 0

# For the other trials, wait until the the trial should start, based on the time
# of the first trial and the trial duration
else:
    time_to_pad = self.get('first_trial_timestamp') + trial_id * trial_duration - self.time()
    if time_to_pad > 0:
        self.sleep(time_to_pad)

# Remember the trial id and padding time
exp.set('trial_id', trial_id+1)
exp.set('time_to_pad', time_to_pad)