Graphics

Each task in an AxoPy experiment is given a Container. The container is effectively an empty QWidget from Qt, so you can set up its contents quite flexibly. That is, any valid QWidget or QLayout can be used as the container’s contents, so you can create arbitrarily complex graphics for a task.

To set up graphics for a task, override the Task.prepare_graphics method, which takes the Container as an input argument, then use Container.set_widget() to establish the main widget for the task.

from axopy.task import Task

class CanvasTask(Task):

    def prepare_graphics(self, container):
        # set up graphical widget/layout here
        widget = ...
        container.set_widget(widget)

While you can always set up completely custom graphics using PyQt5 classes directly, AxoPy includes some graphical elements commonly used in human-computer interface experiments, making it possible to write experiments without knowing how to use Qt.

Note

In the examples below, get_qtapp() will be used to demonstrate different graphical widgets and layouts. This function creates or retrieves a QApplication instance. We can then use app.exec_() to run the Qt event loop and test out the graphics code.

Built-In Graphics Widgets

Canvas Graphics

The axopy.gui.canvas module contains a Canvas class which can be directly inserted into a container. You can then add items like a Circle or Text to the canvas. In the context of a task, you can create a canvas as follows:

from axopy.gui.main import get_qtapp
from axopy.gui.canvas import Canvas, Circle

app = get_qtapp()

canvas = Canvas()
canvas.add_item(Circle(0.1, color='red'))

canvas.show()
app.exec_()

All of the built-in items inherit from the Item class, which means they all have a number of properties that can be set, such as the position and visibility.

canvas = Canvas()
circle = Circle(0.1)
canvas.add_item(circle)

# set the x coordinate
circle.x = 0.5
# read the y coordinate
y = circle.y
# hide the circle
circle.hide()

All of the Item classes are actually just wrappers around QGraphicsItem classes. In general, the various subclasses of QGraphicsItem (e.g. QGraphicsEllipseItem) have a large number of methods that may not be exposed by AxoPy, so all items have a qitem attribute pointing to the underlying QGraphicsItem. For example, the Line item wraps a QGraphicsLineItem. In AxoPy, a line is just a solid line with a specific cap style. If you need to customize this behavior, you can use the qitem attribute and dig into the Qt API:

from axopy.gui.canvas import Line

# horizontal line 0.4 units long
line = Line(-0.2, 0, 0.2, 0)

Graphics

Built-In Graphics Widgets

Canvas Graphics

Custom Items