+ return scm_from_double (0.0);
+}
+
+
+
+SCM
+Self_alignment_interface::centered_on_object (Grob *him, Axis a)
+{
+ return scm_from_double (robust_relative_extent (him, him, a).center ());
+}
+
+
+MAKE_SCHEME_CALLBACK (Self_alignment_interface, centered_on_x_parent, 1);
+SCM
+Self_alignment_interface::centered_on_x_parent (SCM smob)
+{
+ return centered_on_object (unsmob_grob (smob)->get_parent (X_AXIS), X_AXIS);
+}
+
+
+MAKE_SCHEME_CALLBACK (Self_alignment_interface, centered_on_y_parent, 1);
+SCM
+Self_alignment_interface::centered_on_y_parent (SCM smob)
+{
+ return centered_on_object (unsmob_grob (smob)->get_parent (Y_AXIS), Y_AXIS);
+}
+
+
+MAKE_SCHEME_CALLBACK (Self_alignment_interface, x_centered_on_y_parent, 1);
+SCM
+Self_alignment_interface::x_centered_on_y_parent (SCM smob)
+{
+ return centered_on_object (unsmob_grob (smob)->get_parent (Y_AXIS), X_AXIS);
+}
+
+MAKE_SCHEME_CALLBACK (Self_alignment_interface, aligned_on_x_parent,1);
+SCM
+Self_alignment_interface::aligned_on_x_parent (SCM smob)
+{
+ return aligned_on_parent (unsmob_grob (smob), X_AXIS);
+}
+
+MAKE_SCHEME_CALLBACK (Self_alignment_interface, aligned_on_y_parent,1);
+SCM
+Self_alignment_interface::aligned_on_y_parent (SCM smob)
+{
+ return aligned_on_parent (unsmob_grob (smob), Y_AXIS);
+}
+
+SCM
+Self_alignment_interface::aligned_on_parent (Grob *me, Axis a)
+{
+ Grob *him = me->get_parent (a);
+ if (Paper_column::has_interface (him))
+ return scm_from_double (0.0);
+
+ Interval he = him->extent (him, a);
+
+ SCM sym = (a == X_AXIS) ? ly_symbol2scm ("self-alignment-X")
+ : ly_symbol2scm ("self-alignment-Y");
+ SCM align_prop (me->internal_get_property (sym));
+
+ if (!scm_is_number (align_prop))
+ return scm_from_int (0);
+
+ Real x = 0.0;
+ Real align = scm_to_double (align_prop);
+
+ Interval ext (me->extent (me, a));
+ if (ext.is_empty ())
+ programming_error ("cannot align on self: empty element");
+ else
+ x -= ext.linear_combination (align);
+
+ if (!he.is_empty ())
+ x += he.linear_combination (align);
+
+ return scm_from_double (x);
+}
+
+void
+Self_alignment_interface::set_center_parent (Grob *me, Axis a)
+{
+ add_offset_callback (me,
+ (a==X_AXIS) ? centered_on_x_parent_proc : centered_on_y_parent_proc,
+ a);
+}
+
+void
+Self_alignment_interface::set_align_self (Grob *me, Axis a)
+{
+ add_offset_callback (me,
+ (a==X_AXIS) ? x_aligned_on_self_proc : y_aligned_on_self_proc,
+ a);