GTK+ is a system that relies on signals and callback functions. A signal is a notification to your application that the user has performed some action. When a signal is emitted, you can tell GTK+ to run a function named a callback function.
To connect a signal, you can use
g_signal_connect(). This function accepts four parameters. The first is the
GObject you are watching for the signal. The
signal_name is a string representing the signal; a list of signal names can be found in the tables throughout this appendix.
gulong g_signal_connect (gpointer object, const gchar *signal_name, GCallback handler, gpointer data);
The third parameter is the name ...