How to update widget dynamically in GTK3 (PyGObject)?

Question

In this example, I'm trying to add another button (or any widget) every time a button is pressed.

from gi.repository import Gtk


class ButtonWindow(Gtk.Window):
    def __init__(self):
        super().__init__(title="Button Demo")
        self.hbox = Gtk.HBox()
        self.add(self.hbox)
        button = Gtk.Button.new_with_label("Click Me")
        button.connect("clicked", self.on_clicked)
        self.hbox.pack_start(button, False, True, 0)

    def on_clicked(self, button):
        print("This prints...")
        button = Gtk.Button.new_with_label("Another button")
        self.hbox.pack_start(button, False, True, 0)  # ... but the new button doesn't appear


win = ButtonWindow()
win.connect("destroy", Gtk.main_quit)
win.show_all()
Gtk.main()

I have tried queue_draw() and other hacks, but nothing has worked so far.

Answer 1

Calling the show_all() method works to update widgets' children. Here is the code with show_all() used, and the added line marked accordingly:

from gi.repository import Gtk


class ButtonWindow(Gtk.Window):
    def __init__(self):
        super().__init__(title="Button Demo")
        self.hbox = Gtk.HBox()
        self.add(self.hbox)
        button = Gtk.Button.new_with_label("Click Me")
        button.connect("clicked", self.on_clicked)
        self.hbox.pack_start(button, False, True, 0)

    def on_clicked(self, button):
        print("This prints...")
        button = Gtk.Button.new_with_label("Another button")
        self.hbox.pack_start(button, False, True, 0)
        self.hbox.show_all() ### ADDED LINE


win = ButtonWindow()
win.connect("destroy", Gtk.main_quit)
win.show_all()
Gtk.main()

So, calling self.hbox.show_all() shows all the children of self.hbox.