When you generate the C source code, an empty signal handler function should be output in the callbacks.c file. You can add your code to this function.

Make sure you place your configure.in test before the call to AC_OUTPUT.

Note that this does not work if you are using libglade. The corresponding code for libglade would be:

void
on_button1_clicked                     (GtkButton       *button,
                                        gpointer         user_data)
{
  GladeXML* xml;
  GtkWidget* entry1;

  xml = glade_get_widget_tree (GTK_WIDGET (button1));
  entry1 = glade_xml_get_widget (xml, "entry1");

  ...
}
      

  main_window = gtk_object_get_data (GTK_OBJECT (dialog), "main_window");
      

You need to be careful to ensure that the pointer is always valid. If the window being pointed to is destroyed, make sure you no longer use the pointer to it or your application may crash.

Then add a handler to callbacks.c. You can get the index of the selected item just like the previous answer:

static void
on_option_selected (GtkMenuShell *menu_shell,
                    gpointer data)
{
  GtkWidget *active_item;
  gint item_index;

  active_item = gtk_menu_get_active (GTK_MENU (menu_shell));
  item_index = g_list_index (menu_shell->children, active_item);

  g_print ("In on_option_selected active: %i\n", item_index);
}