- * Add a new state for the specified type to the current state set if
- * it is not already present.
+ * 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
+ * #atk_object_ref_state_set. It should not be used to modify the existing state
+ * of an object. See also #atk_object_notify_state_change.