GTK Signals (Cont.)

The programmer needs to connect a callback to a signal. Here is how this is done for the top-level window:

 /* When the window is given the "delete_event" signal (this is
  * given by the window manager, usually by the "close" option,
  * or on the titlebar), we ask it to call the delete_event()
  * function as defined above. The data passed to the callback
  * function is NULL and is ignored in the callback function.
  */
 gtk_signal_connect(GTK_OBJECT (main_window), "delete_event",
                    GTK_SIGNAL_FUNC (delete_event), NULL);