Third-party plugins

napari-matplotlib provides a ready-to-go widget with a Matplotlib toolbar and figure to third party plugin developers. This widget is customised to match the theme of the main napari window.

The widget can be found at napari_matplotlib.base.NapariMPLWidget. This class inherits from QWidget.

The recommended way to use NapariMPLWidget is inside a new widget, adding it to the layout. This means you can add additional elements to your plugin layout alongside the Matplotlib figure. Here’s a short example:

from qtpy.QtWidgets import QWidget
from napari_matplotlib.base import NapariMPLWidget

class MyPlugin(QWidget):
    def __init__(self, napari_viewer: napari.viewer.Viewer, parent=None):
        super().__init__(parent=parent)

        # Any custom setup for your custom widget
        ...

        # Set up the plot widget
        plot_widget =  NapariMPLWidget(napari_viewer, parent=self)
        self.layout().addWidget(plot_widget)

The following properties and methods are useful for working with the figure and any axes within the widget:

• figure provides access to the figure

• add_single_axes() adds a single axes to the figure, which can be accessed using the .axes attribute.

Working with napari layers

When either the layer selection or z-step in the napari viewer is changed clear() and draw() are called in turn. By default these do nothing, and are designed to be overriden by plugins to automatically re-draw any figures within the widget. Plugins can also override on_update_layers() to do something when the layer selection changes. This can be used to do something without clearing or re-drawing any plots.

Validating layer numbers and types

By default draw() will be called when any number of any type of napari layers are selected. The n_layers_input and input_layer_types class variables can be overriden to specify the number of selected napari layers and valid layer types that are taken as input. If the number of selected layers and their types do not match up with these class variables, no re-draw is called.