lily/midi-def.cc

   1 /*
   2   midi-def.cc -- implement midi output def functions
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 1997--2004 Jan Nieuwenhuizen <janneke@gnu.org>
   7
   8 */
   9 #include <math.h>
  10
  11 #include "misc.hh"
  12 #include "output-def.hh"
  13 #include "moment.hh"
  14 #include "warn.hh"
  15 #include "scm-hash.hh"
  16
  17
  18
  19 int
  20 get_tempo (Output_def * def,
  21            Moment one_beat_mom)
  22 {
  23   SCM wis  = ly_symbol2scm ("whole-in-seconds");
  24   Moment *w = unsmob_moment (def->lookup_variable (wis));
  25
  26   Moment wholes_per_min = Moment (60);
  27   if (!w)
  28     {
  29       programming_error  ("wholes-in-seconds not set.");
  30       wholes_per_min /= 4;
  31     }
  32   else
  33     {
  34       wholes_per_min /= *w;
  35     }
  36
  37   int beats_per_min =  int ((wholes_per_min / one_beat_mom).main_part_);
  38   return int (beats_per_min);
  39 }
  40
  41 void
  42 set_tempo (Output_def * def,
  43            Moment one_beat_mom,
  44            int beats_per_minute_i)
  45 {
  46   Moment beats_per_second = Moment (beats_per_minute_i) / Moment (60);
  47
  48   Moment m = Moment (1)/Moment (beats_per_second * one_beat_mom);
  49   def->set_variable (ly_symbol2scm ("whole-in-seconds"), m.smobbed_copy ());
  50 }
  51