Program quits correctly

app_win_2_back.cpp

@@ -1,6 +1,7 @@
 #include "app_win_2_back.hpp"
 #include "hello_world.hpp"
 #include <iostream>
+#include <glibmm/miscutils.h>
 
 namespace gui_to_app {
     AppWin2Back::AppWin2Back() : Gtk::Application("org.billy_adventures.character_sheet", Flags::HANDLES_OPEN) {
@@ -22,7 +23,7 @@ namespace gui_to_app {
             std::cerr << "Error occured while loading menu bar's.\n";
         } else {
             set_menubar(menu_bar);
-            add_action("quit", sigc::mem_fun(*this, &AppWin2Back::quit));
+            add_action("quit", sigc::mem_fun(*this, &AppWin2Back::on_quit));
             set_accel_for_action("app.quit", "<Ctrl>q");
         }
     }
@@ -54,8 +55,16 @@ namespace gui_to_app {
             main_window->set_show_menubar(true);
             main_window->set_visible(true);
         } else {
-            quit();
+            on_quit();
         }
     }
 
+    void AppWin2Back::on_quit() {
+        auto windows = get_windows();
+        for (auto *window: windows) {
+            window->set_visible(false);
+        }
+        quit();
+    }
+
 } // gui_to_app

app_win_2_back.hpp

@@ -1,7 +1,8 @@
 #ifndef LEARNGTK4_APP_WIN_2_BACK_HPP
 #define LEARNGTK4_APP_WIN_2_BACK_HPP
 
-#include <gtkmm.h>
+#include <gtkmm/application.h>
+#include <glibmm/refptr.h>
 
 namespace learn_gtkmm4 {
     class HelloWorld;
@@ -23,6 +24,8 @@ namespace gui_to_app {
         void on_activate() final;
 
     private:
+        void on_quit();
+
         learn_gtkmm4::HelloWorld *main_window{ nullptr };
     };