Embedding in GTK4 with a navigation toolbar

Demonstrate NavigationToolbar with GTK4 accessed via pygobject.

import gi
gi.require_version('Gtk', '4.0')
from gi.repository import Gtk

from matplotlib.backends.backend_gtk4 import (
    NavigationToolbar2GTK4 as NavigationToolbar)
from matplotlib.backends.backend_gtk4agg import (
    FigureCanvasGTK4Agg as FigureCanvas)
from matplotlib.figure import Figure
import numpy as np


def on_activate(app):
    win = Gtk.ApplicationWindow(application=app)
    win.set_default_size(400, 300)
    win.set_title("Embedding in GTK4")

    fig = Figure(figsize=(5, 4), dpi=100)
    ax = fig.add_subplot(1, 1, 1)
    t = np.arange(0.0, 3.0, 0.01)
    s = np.sin(2*np.pi*t)
    ax.plot(t, s)

    vbox = Gtk.Box(orientation=Gtk.Orientation.VERTICAL)
    win.set_child(vbox)

    # Add canvas to vbox
    canvas = FigureCanvas(fig)  # a Gtk.DrawingArea
    canvas.set_hexpand(True)
    canvas.set_vexpand(True)
    vbox.append(canvas)

    # Create toolbar
    toolbar = NavigationToolbar(canvas)
    vbox.append(toolbar)

    win.show()


app = Gtk.Application(
    application_id='org.matplotlib.examples.EmbeddingInGTK4PanZoom')
app.connect('activate', on_activate)
app.run(None)