gboolean atk_state_set_add_state ( AtkStateSet* set, AtkStateType type )
Adds the state of the specified type to the state set if it is not already present.
Note that because an
AtkStateSet is a read-only object, this method should
be used to add a state to a newly-created set which will then be returned by
of an object. See also #atk_object_notify_state_change.