+
+
+/*
+ should use offset callback!
+ */
+MAKE_SCHEME_CALLBACK (Staff_symbol_referencer,callback,2);
+SCM
+Staff_symbol_referencer::callback (SCM element_smob, SCM)
+{
+ Grob *me = unsmob_grob (element_smob);
+
+
+ SCM pos = me->get_grob_property ("staff-position");
+ Real off =0.0;
+ if (gh_number_p (pos))
+ {
+ Real space = Staff_symbol_referencer::staff_space (me);
+ off = gh_scm2double (pos) * space/2.0;
+ }
+
+ me->set_grob_property ("staff-position", gh_double2scm (0.0));
+
+ return gh_double2scm (off);
+}
+
+ /*
+
+ This sets the position relative to the center of the staff symbol.
+
+ The function is hairy, because it can be callled in two situations:
+
+ 1. There is no staff yet; we must set staff-position
+
+ 2. There is a staff, and perhaps someone even applied a
+ translate_axis (). Then we must compensate for the translation
+
+ In either case, we set a callback to be sure that our new position
+ will be extracted from staff-position
+
+ */
+void
+Staff_symbol_referencer::set_position (Grob*me,Real p)
+{
+ Grob * st = staff_symbol_l (me);
+ if (st && me->common_refpoint (st, Y_AXIS))
+ {
+ Real oldpos = position_f (me);
+ me->set_grob_property ("staff-position", gh_double2scm (p - oldpos));
+ }
+ else
+ {
+ me->set_grob_property ("staff-position",
+ gh_double2scm (p));
+
+ }
+
+ if (me->has_offset_callback_b (Staff_symbol_referencer::callback_proc, Y_AXIS))
+ return ;
+
+ me->add_offset_callback (Staff_symbol_referencer::callback_proc, Y_AXIS);
+}
+
+/*
+ half of the height, in staff space.
+ */