Pages¶

Pages represent states with usually different visual displays. For instance, one page could be a fixation stimulus, presenting a single centered dot. The experiment could then be carried on to an animated display, for instance a moving grating. Then a question can be asked to the subject, before coming back to the first state.

Painting a page¶

Defining a visual display for a page can be done by setting its onPaint property:

Page {
    name: "fixation"
    onPaint: {
        painter.setBrush(color);
        painter.drawEllipse(/* […] */);
    }
}

The onPaint function is called with a painter argument which wraps a QPainter object from Qt.

Animated pages¶

By setting the animated property of a page, one can define video to be displayed. Animated pages use the same function, onPaint to define the content of the frames, but with an additional argument, frameNumber. You must also define the duration property to specify for how long the page should be animated:

Page {
    name : "frames"
    animated : true
    duration : 400
    onPaint : {
        paintDots (painter, frameNumber);
    }
}

Here paintDots is a user-defined function of the experiment.

Key events¶

By default a fixed page will be presented until the user press Enter or the Space bar. You can configure the set of keys a fixed frame will wait for, using the acceptedKey property, which takes an array of key names, or specify a duration for the presentation, with duration.

Keyboard events can also be listened to by defining a onKeyPress handler in the page properties:

Page {
    acceptedKeys : ["Left", "Right"]
    onKeyPress : {
        correct = clockwise ? key == "Left" : key == "Right";
    }
}

Transitions¶

By default the next page to be shown in an experiment is simply the page following the current one in the order of declaration, and the trial will be ended when arriving at the last page. The page order can be modified by calling the showPage function, for instance inside a signal handler:

onKeyPress : {
    showPage(correct ? correctPage : incorrectPage)
}

You can also define a page to end the current trial by setting its last property.