+ SCM interfaces = me->get_property ("bound-alignment-interfaces");
+
+ for (vsize i = 0; i < elts.size (); i++)
+ for (SCM l = interfaces; scm_is_pair (l); l = scm_cdr (l))
+ if (elts[i]->internal_has_interface (scm_car (l)))
+ new_elts.push_back (elts[i]);
+
+ if (!new_elts.size ())
+ return robust_relative_extent (me, common, a);
+
+ if (!common)
+ common = common_refpoint_of_array (new_elts, me, a);
+
+ return relative_maybe_bound_group_extent (new_elts, common, a, true);
+}
+
+Interval
+Axis_group_interface::sum_partial_pure_heights (Grob *me, int start, int end)
+{
+ Interval iv = begin_of_line_pure_height (me, start);
+ iv.unite (rest_of_line_pure_height (me, start, end));
+
+ return iv;
+}
+
+Interval
+Axis_group_interface::part_of_line_pure_height (Grob *me, bool begin, int start, int end)
+{
+ Spanner *sp = dynamic_cast<Spanner *> (me);
+ SCM cache_symbol = begin
+ ? ly_symbol2scm ("begin-of-line-pure-height")
+ : ly_symbol2scm ("rest-of-line-pure-height");
+ SCM cached = sp->get_cached_pure_property (cache_symbol, start, end);
+ if (scm_is_pair (cached))
+ return robust_scm2interval (cached, Interval (0, 0));
+
+ SCM adjacent_pure_heights = me->get_property ("adjacent-pure-heights");
+ Interval ret;
+
+ if (!scm_is_pair (adjacent_pure_heights))
+ ret = Interval (0, 0);
+ else
+ {
+ SCM these_pure_heights = begin
+ ? scm_car (adjacent_pure_heights)
+ : scm_cdr (adjacent_pure_heights);
+
+ if (scm_is_vector (these_pure_heights))
+ ret = combine_pure_heights (me, these_pure_heights, start, end);
+ else
+ ret = Interval (0, 0);
+ }
+
+ sp->cache_pure_property (cache_symbol, start, end, ly_interval2scm (ret));
+ return ret;
+}
+
+Interval
+Axis_group_interface::begin_of_line_pure_height (Grob *me, int start)
+{
+ return part_of_line_pure_height (me, true, start, start + 1);
+}
+
+Interval
+Axis_group_interface::rest_of_line_pure_height (Grob *me, int start, int end)
+{
+ return part_of_line_pure_height (me, false, start, end);
+}