+ if (get_property_data ("vertical-skylines") == SCM_EOL)
+ set_property ("vertical-skylines", Grob::simple_vertical_skylines_from_extents_proc);
+ if (get_property_data ("horizontal-skylines") == SCM_EOL)
+ set_property ("horizontal-skylines", Grob::simple_horizontal_skylines_from_extents_proc);