Item *lgr = get_x_bound_item (me, LEFT, dir);
Item *rgr = get_x_bound_item (me, RIGHT, dir);
Real x0 = robust_relative_extent (lgr, commonx, X_AXIS)[LEFT];
Real x1 = robust_relative_extent (rgr, commonx, X_AXIS)[RIGHT];
Item *lgr = get_x_bound_item (me, LEFT, dir);
Item *rgr = get_x_bound_item (me, RIGHT, dir);
Real x0 = robust_relative_extent (lgr, commonx, X_AXIS)[LEFT];
Real x1 = robust_relative_extent (rgr, commonx, X_AXIS)[RIGHT];