pyplot with GTK3

An example of how to use pyplot to manage your figure windows, but modify the GUI by accessing the underlying GTK widgets.

import matplotlib
matplotlib.use('GTK3Agg')  # or 'GTK3Cairo'
import matplotlib.pyplot as plt

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk


fig, ax = plt.subplots()
ax.plot([1, 2, 3], 'ro-', label='easy as 1 2 3')
ax.plot([1, 4, 9], 'gs--', label='easy as 1 2 3 squared')
ax.legend()

manager = fig.canvas.manager
# you can access the window or vbox attributes this way
toolbar = manager.toolbar
vbox = manager.vbox

# now let's add a button to the toolbar
button = Gtk.Button(label='Click me')
button.show()
button.connect('clicked', lambda button: print('hi mom'))

toolitem = Gtk.ToolItem()
toolitem.show()
toolitem.set_tooltip_text('Click me for fun and profit')
toolitem.add(button)

pos = 8  # where to insert this in the toolbar
toolbar.insert(toolitem, pos)

# now let's add a widget to the vbox
label = Gtk.Label()
label.set_markup('Drag mouse over axes for position')
label.show()
vbox.pack_start(label, False, False, 0)
vbox.reorder_child(toolbar, -1)


def update(event):
    if event.xdata is None:
        label.set_markup('Drag mouse over axes for position')
    else:
        label.set_markup(
            f'<span color="#ef0000">x,y=({event.xdata}, {event.ydata})</span>')


fig.canvas.mpl_connect('motion_notify_event', update)

plt.show()