activate_focus() is a method that will emit the activate signal from the child widget having focus at the point that the method is called. In GTK+, each widget has one signal which has activate signal status; the signal with this status has the ability to respond to events generated from the keyboard. If you do not have that widget-specific activate signal connected to the widget with focus, nothing will be fired.

The widget that is most likely to be used in this situation is probably GtkButton, which has "clicked" as its activate signal.

See also: Signals and Events in the PHP-GTK userguide, activate_default() , set_focus() , "activate".