Auto draw stimulus with custom draw logic

Coding
1

I am trying to debug some eyetracker issues and am interested in making a stimulus object to help me do this by showing the gaze position on the screen in real time (similar to what’s in the demos).

I want this to be an object I can just drop into any script to help debug without having to add logic to update the position and draw it everywhere throughout the script. I thought a clever way to do this might be to subclass a PsychoPy stimulus object, extend the draw method to pull gaze position data from the eyetracker, and then set autoDraw to be True. However I’ve run into a number of issues.

Here is a simple example of what I thought might work:

class GazeStim(GratingStim):

    def __init__(self, win, tracker):

        self.tracker = tracker
        super(GratingStim, self).__init__(win)
        self.setAutoDraw(True)

    def draw(self):

        gaze = self.tracker.getLastGazePosition()
        if isinstance(gaze, (tuple, list)):
            gaze = pix2deg(np.array(gaze), self.win.monitor)
            self.pos = gaze
            self.opacity = 1
        else:
            self.opacity = 0

        super(GratingStim, self).draw()

However this fails with:

Traceback (most recent call last):
  File "experiment.py", line 630, in <module>
    main(sys.argv[1:])
  File "experiment.py", line 87, in main
    experiment_loop(p, win, stims, design, tracker)
  File "experiment.py", line 178, in experiment_loop
    stims["instruct"].draw()
  File "/Users/mwaskom/anaconda/envs/psychopy/lib/python2.7/site-packages/cregg-0.1.dev0-py2.7.egg/cregg/main.py", line 239, in draw
    self.win.flip()
  File "/Users/mwaskom/anaconda/envs/psychopy/lib/python2.7/site-packages/psychopy/visual/window.py", line 541, in flip
    thisStim.draw()
  File "experiment.py", line 134, in draw
    super(GratingStim, self).draw()
  File "/Users/mwaskom/anaconda/envs/psychopy/lib/python2.7/site-packages/psychopy/visual/basevisual.py", line 929, in draw
    raise NotImplementedError('Stimulus classes must override visual.BaseVisualStim.draw')
NotImplementedError: Stimulus classes must override visual.BaseVisualStim.draw

which I find confusing.

Has anyone implemented this sort of thing or can someone provide some tips for the right way to approach this task?

2

Nice idea and you’re doing nearly all the right things but I think you’re calling the the super-class of the GratingStim, rather than the super of your sub-class. The super of GratingStim doesn’t have draw() implemented so complains.

Change the line super(GratingStim, self).draw() to be either

super(GazeStim, self).draw()

or possibly just

GratingStim.draw(self)
3

Ah, yes. Thanks for catching that. Guess it’s why they removed the confusing arguments to super in Python 3…