Glade + Python how to close second window

Question

I am trying to write simple aplication with two windows using Glade+Python. Take look at my code please. Start file:

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk
from handlers import *

builder = Gtk.Builder.new_from_file("okno1.glade")
window = builder.get_object("okno") #Main window of the application
window_about = builder.get_object("okno2") #second window of the application - should not be shown at the beginning

builder.connect_signals(Handlers()) #here i connect class "Handlers" which make some actions with signals from both windows
window.connect("delete-event", Gtk.main_quit) # i connect "delete-event" with main window. If we close it, whole app should be closed - works as it should
window_about.connect("delete-event", Gtk.Window.hide) #Here is problematic line....
Gtk.main()

And file with handler class:

class Handlers:

def okno_button_clicked_cb(self, widget):
    '''this method takes care about button on main window'''
    widget.show_all()
    
def okno2_button_clicked_cb(self, widget):
    '''this method takes care about button on second window'''
    widget.hide()

Working app loks like this:

Thare is main Window on left. If I click on the button on it, window on right appears. If I click button on second window - it dissapears. When I click again button on main window second window appears - everything works fine. But if I click "X" button on the top of second window, second window dissapear, and if I click again button on main window, second window appears but without its button.... Where is the problem???? I think something is wrong with "delete event" of second window (window_about). But what should I use instead of Gtk.Window.hide????

Please help, I am completely out of ideas :-(

P.S. here is "okno1.glade":

<?xml version="1.0" encoding="UTF-8"?>
<!-- Generated with glade 3.20.4 -->
<interface>
  <requires lib="gtk+" version="3.20"/>
  <object class="GtkWindow" id="okno">
    <property name="visible">True</property>
    <property name="can_focus">False</property>
    <property name="default_width">440</property>
    <property name="default_height">250</property>
    <child>
      <object class="GtkFixed">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <child>
          <object class="GtkButton" id="okno_button">
            <property name="label" translatable="yes">otworz durgie okno</property>
            <property name="width_request">100</property>
            <property name="height_request">80</property>
            <property name="visible">True</property>
            <property name="can_focus">True</property>
            <property name="receives_default">True</property>
            <signal name="clicked" handler="okno_button_clicked_cb" object="okno2" swapped="no"/>
          </object>
          <packing>
            <property name="x">232</property>
            <property name="y">134</property>
          </packing>
        </child>
      </object>
    </child>
    <child type="titlebar">
      <placeholder/>
    </child>
  </object>
  <object class="GtkWindow" id="okno2">
    <property name="can_focus">False</property>
    <property name="modal">True</property>
    <property name="default_width">440</property>
    <property name="default_height">250</property>
    <child>
      <object class="GtkFixed">
        <property name="visible">True</property>
        <property name="can_focus">False</property>
        <child>
          <object class="GtkButton" id="okno2_button">
            <property name="label" translatable="yes">zamknij okno
</property>
            <property name="width_request">100</property>
            <property name="height_request">80</property>
            <property name="visible">True</property>
            <property name="can_focus">True</property>
            <property name="receives_default">True</property>
            <signal name="clicked" handler="okno2_button_clicked_cb" object="okno2" swapped="no"/>
          </object>
          <packing>
            <property name="x">237</property>
            <property name="y">132</property>
          </packing>
        </child>
      </object>
    </child>
    <child type="titlebar">
      <placeholder/>
    </child>
  </object>
</interface>

Answer 1

I'll explain the problem and its solution, but if you just want the solution without the explanation, the full solution code is at the end of the answer.

---

Here's the problem. You probably notice that, when you click okno_button, the terminal prints an error message:

TypeError: Gtk.Widget.hide() takes exactly 1 argument (2 given)

This means that when Gtk calls the hide() function that you connected to the delete-event signal, it's giving it two arguments, instead of one. In this case, the one argument is self, since hide() is a class method. When the window is closed (and the delete-event signal is sent), hide() is getting two arguments: self, and the window-close event.

The solution to this error message is to write a separate function that does take two arguments. Here is a simple example:

def hide_window(window, event):
    window.hide()

However, if you use this function instead of hide() (window_about.connect("delete-event", hide_window)), the button still disappears. This is because Gtk's delete-event deletes the window (no surprise there).

To prevent the window from deleting itself, you can return True at the end of your hide_window() function. Using return True at the end of a callback function tells Gtk not to react to the event; that you've already taken care of it. This is a nice trick that comes in especially handy in things like text editors, where programmers want to override the default behaviors of a text widget.

---

All that being said, here is the full working code, with the hide_window() function that only hides the window when it's closed; the window isn't deleted.

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk
from handlers import *

def hide_window(window, event):
    window.hide()
    return True

builder = Gtk.Builder.new_from_file("okno1.glade")
window = builder.get_object("okno")
window_about = builder.get_object("okno2")

builder.connect_signals(Handlers())
window.connect("delete-event", Gtk.main_quit)
window_about.connect("delete-event", hide_window)
Gtk.main()