Adds parenthesized measure numbers at mid-bar breaks.

lily/bar-number-engraver.cc

 /*
   This file is part of LilyPond, the GNU music typesetter.
 
   Copyright (C) 1997--2011 Han-Wen Nienhuys <hanwen@xs4all.nl>
 
   LilyPond is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.
 
@@ skipping 77 matching lines @@
 Bar_number_engraver::process_music ()
 {
   SCM wb = get_property ("whichBar");
 
   if (scm_is_string (wb))
     {
       Moment mp (robust_scm2moment (get_property ("measurePosition"), Moment (0)));
       SCM bn = get_property ("currentBarNumber");
       SCM proc = get_property ("barNumberVisibility");
       if (scm_is_number (bn) && ly_is_procedure (proc)
-          && to_boolean (scm_call_1 (proc, bn)))
+          && to_boolean (scm_call_2 (proc, bn, mp.smobbed_copy ())))
         {
           create_items ();
           SCM alternative_style = get_property ("alternativeNumberingStyle");
           string text_tag = "";
           if (alternative_style == ly_symbol2scm ("numbers-with-letters"))
             {
               if (alternative_event_)
                 {
                   Direction alternative_dir = robust_scm2dir (alternative_event_->get_property ("alternative-dir"), RIGHT);
                   switch (alternative_dir)
@@ skipping 83 matching lines @@
                 "currentBarNumber "
                 "whichBar "
                 "stavesFound "
                 "barNumberFormatter "
                 "barNumberVisibility "
                 "alternativeNumberingStyle ",
 
                 /* write */
                 "currentBarNumber "
                );