line.turn_permission_ = min_permission (line.page_permission_,
line.turn_permission_);
+ // TODO: see the hack regarding begin_of_line and
+ // rest_of_line extents in align-interface. Perhaps we
+ // should do the same thing here so that the effect extends
+ // between systems as well as within systems. It isn't as
+ // crucial here, however, because the effect is largest when
+ // dealing with large systems.
line.extent_ = (extent.is_empty ()
|| isnan (extent[LEFT])
|| isnan (extent[RIGHT]))