g_signal_connect . The second argument for this function is detailed_signal : a string of the form “signal-name::detail”. source :http://library.gnome.org/devel/gobject/unstable/gobject-Signals.html GtkWidget is the base class for all widgets. “expose-event” is an signal and the signal list is available at http://library.gnome.org/devel/gtk/unstable/GtkWidget.html