+ int set_state (const XMLNode&);
+ XMLNode& get_state () const;
+
+ /** Get a string from our state.
+ * @param id property of Object node to look for.
+ * @param prop_name name of the Object property to return.
+ * @param empty if non-0, filled in with true if the property is currently non-existant, otherwise false.
+ * @return value of property `prop_name', or empty.
+ */