gtk-sharp 2.10.0.0 Gtk# is thread aware, but not thread safe; See the Gtk# Thread Programming for details. Event sender. Event arguments. Event handler. The event utilizes this delegate: Event data is passed via the parameter. To attach a to an event, add the FocusChildSetHandler instance to the event. The methods referenced by the FocusChildSetHandler instance are invoked whenever the event is raised, until the FocusChildSetHandler is removed from the event. System.Delegate System.Void