prop_bag = bonobo_property_bag_new(get_prop, set_prop, math_view);
bonobo_control_set_properties(control, BONOBO_OBJREF(prop_bag), NULL);
prop_bag = bonobo_property_bag_new(get_prop, set_prop, math_view);
bonobo_control_set_properties(control, BONOBO_OBJREF(prop_bag), NULL);