How can I port this gtk construct to gtkmm?

[Jef Driesen <jefdriesen hotmail com>]

I am writing my first gtkmm application (actually my first GUI 
application). To get familiar with the toolkit (both gtk and gtkmm), I 
studied the code of some existing applications. And in one of those 
applications I found a construct that I would like to use in my own 
application, but I don't know how to port the gtk code to gtkmm.

The main application contains a treeview and a secondary dialog is used 
to edit the treeview entries. But if you try to edit an entry that is 
already "open", the existing dialog is activated instead of creating a 
new one (see code snippet below). How can I do this in C++?

And how do I automatically destroy the dialog after clicking the (close) 
button?

/* myobject_treeview.c */

GtkWidget* main_window = ...;
myobject* obj = ...;
GtkWidget* dialog = myobject_dialog_new (main_window, obj);
gtk_widget_show (dialog);

/* myobject_dialog.c */

static GHashTable *dialogs = NULL;

GtkWidget* myobject_dialog_new (GtkWidget* parent, myobject* obj)
{
   if (!dialogs) {
      dialogs = g_hash_table_new (NULL, NULL);
   }

   dialog = g_hash_table_lookup (dialogs, obj);
   if (dialog) {
      gtk_window_present (GTK_WINDOW (dialog));
      return dialog;
   }

   dialog = gtk_dialog_new ();

   g_hash_table_insert (dialogs, obj, dialog);

   g_signal_connect (close_button,
            "clicked",
            G_CALLBACK (myobject_dialog_close_clicked_cb),
            dialog);

   g_signal_connect (dialog,
            "destroy",
            G_CALLBACK (myobject_dialog_destroy_cb),
            obj);

   g_signal_connect_object (parent,
            "destroy",
            G_CALLBACK (myobject_dialog_parent_destroy_cb),
            dialog,
            0);
}

static void
myobject_dialog_destroy_cb (GtkWidget *parent, myobject *obj)
{
   g_hash_table_remove (dialogs, obj);
}

static void
myobject_dialog_parent_destroy_cb (GtkWidget *parent, GtkWidget *dialog)
{
   gtk_widget_destroy (dialog);
}

static void
myobject_dialog_close_clicked_cb (GtkWidget *button, GtkWidget *dialog)
{
   gtk_widget_destroy (dialog);
}