Binding extra arguments
If you use one signal handler to catch the same signal from several widgets, you might like that signal handler to receive some extra information. For instance, you might want to know which button was clicked. You can do this with sigc::bind(). Here's some code from the helloworld2 example.
m_button1.signal_clicked().connect( sigc::bind<Glib::ustring>( sigc::mem_fun(*this, &HelloWorld::on_button_clicked), "button 1") );
virtual void on_button_clicked(Glib::ustring data);
sigc::bind() is not commonly used, but you might find it helpful sometimes. If you are familiar with GTK+ programming then you have probably noticed that this is similar to the extra gpointer data arguments which all GTK+ callbacks have. This is generally overused in GTK+ to pass information that should be stored as member data in a derived widget, but widget derivation is very difficult in C. We have far less need of this hack in gtkmm.