[gtkmm] Dialog demo: Add a non-modal dialog

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 14ef6f16b3300d04c5c177a3397e6f5ec82700f4
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Mon Aug 22 18:23:55 2022 +0200

    Dialog demo: Add a non-modal dialog
    
    Fixes #123

 demos/gtk-demo/example_dialog.cc | 40 +++++++++++++++++++++++++++++++++-------
 1 file changed, 33 insertions(+), 7 deletions(-)
---
diff --git a/demos/gtk-demo/example_dialog.cc b/demos/gtk-demo/example_dialog.cc
index d1eee62c..ad026c4d 100644
--- a/demos/gtk-demo/example_dialog.cc
+++ b/demos/gtk-demo/example_dialog.cc
@@ -4,8 +4,6 @@
  */
 
 #include <gtkmm.h>
-#include <gtk/gtk.h>
-#include <stdio.h>
 
 class Dialog_Interactive;
 
@@ -19,14 +17,18 @@ protected:
   //Signal handlers:
   void on_button_message();
   void on_button_interactive();
+  void on_button_non_modal();
   void on_message_response(int response_id, Gtk::MessageDialog* dialog);
   void on_interactive_response(int response_id, Dialog_Interactive* dialog);
+  void on_non_modal_response(int response_id, Gtk::MessageDialog* dialog);
 
   //Member widgets:
   Gtk::Frame m_Frame;
   Gtk::Box m_VBox, m_VBox2;
   Gtk::Box m_HBox, m_HBox2;
-  Gtk::Button m_Button_Message, m_Button_Interactive;
+  Gtk::Button m_Button_Message;
+  Gtk::Button m_Button_Interactive;
+  Gtk::Button m_Button_NonModal;
   Gtk::Grid m_Grid;
   Gtk::Label m_Label1, m_Label2;
   Gtk::Entry m_Entry1, m_Entry2;
@@ -66,6 +68,7 @@ Example_Dialog::Example_Dialog()
   m_HBox2(Gtk::Orientation::HORIZONTAL, 8),
   m_Button_Message("_Message Dialog", true),
   m_Button_Interactive("_Interactive Dialog", true),
+  m_Button_NonModal("_Non-modal Dialog", true),
   m_Label1("_Entry 1", true),
   m_Label2("E_ntry 2", true)
 {
@@ -79,20 +82,18 @@ Example_Dialog::Example_Dialog()
   m_VBox.set_margin(8);
   m_Frame.set_child(m_VBox);
 
-
   /* Standard message dialog */
   m_VBox.append(m_HBox);
   m_Button_Message.signal_clicked().connect(sigc::mem_fun(*this, &Example_Dialog::on_button_message));
   m_HBox.append(m_Button_Message);
   m_VBox.append(*Gtk::make_managed<Gtk::Separator>(Gtk::Orientation::HORIZONTAL));
 
-
   /* Interactive dialog*/
   m_VBox.append(m_HBox2);
   m_Button_Interactive.signal_clicked().connect(sigc::mem_fun(*this, 
&Example_Dialog::on_button_interactive));
   m_HBox2.append(m_VBox2);
   m_VBox2.append(m_Button_Interactive);
-
+  m_VBox.append(*Gtk::make_managed<Gtk::Separator>(Gtk::Orientation::HORIZONTAL));
 
   m_Grid.set_row_spacing(4);
   m_Grid.set_column_spacing(4);
@@ -105,6 +106,12 @@ Example_Dialog::Example_Dialog()
   m_Grid.attach(m_Label2, 0, 1);
   m_Grid.attach(m_Entry2, 1, 1);
   m_Label2.set_mnemonic_widget(m_Entry2);
+
+  // Non-modal message dialog,
+  // i.e. a dialog that does not freeze the rest of the application.
+  m_VBox.append(m_Button_NonModal);
+  m_Button_NonModal.signal_clicked().connect(sigc::mem_fun(
+    *this, &Example_Dialog::on_button_non_modal));
 }
 
 Example_Dialog::~Example_Dialog()
@@ -132,6 +139,17 @@ void Example_Dialog::on_button_interactive()
   pDialog->show();
 }
 
+void Example_Dialog::on_button_non_modal()
+{
+  const Glib::ustring strMessage = "Non-modal message box.";
+  auto dialog = Gtk::make_managed<Gtk::MessageDialog>(*this, strMessage,
+    /* use_markup= */ false, Gtk::MessageType::INFO, Gtk::ButtonsType::OK, /* modal= */ false);
+  dialog->set_destroy_with_parent(true);
+  dialog->signal_response().connect(sigc::bind(
+    sigc::mem_fun(*this, &Example_Dialog::on_non_modal_response), dialog));
+  dialog->show();
+}
+
 void Example_Dialog::on_message_response(int /* response_id */, Gtk::MessageDialog* dialog)
 {
   m_count++;
@@ -148,6 +166,15 @@ void Example_Dialog::on_interactive_response(int response_id, Dialog_Interactive
   delete dialog;
 }
 
+void Example_Dialog::on_non_modal_response(int /* response_id */, Gtk::MessageDialog* dialog)
+{
+  // Delete the non-modal dialog.
+  // If the Example_Dialog is deleted without first responding to the non-modal
+  // dialog, the non-modal dialog is deleted with Example_Dialog, because it's
+  // a managed widget which is destroyed with its parent.
+  delete dialog;
+}
+
 Dialog_Interactive::Dialog_Interactive(Gtk::Window& parent, const Glib::ustring& entry1, const 
Glib::ustring& entry2)
 : Gtk::Dialog("Interactive Dialog", parent, true),
   m_HBox(Gtk::Orientation::HORIZONTAL, 8),
@@ -191,4 +218,3 @@ Glib::ustring Dialog_Interactive::get_entry2() const
 Dialog_Interactive::~Dialog_Interactive()
 {
 }
-