lily/time-signature-engraver.cc

   1 /*
   2   time-signature-engraver.cc -- implement Time_signature_engraver
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 1997--2005 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9 #include "time-signature.hh"
  10 #include "warn.hh"
  11 #include "engraver-group-engraver.hh"
  12 #include "misc.hh"
  13
  14 /**
  15   generate time_signatures.
  16   */
  17 class Time_signature_engraver : public Engraver
  18 {
  19   Item *time_signature_;
  20   SCM last_time_fraction_;
  21
  22 protected:
  23   virtual void stop_translation_timestep ();
  24   virtual void process_music ();
  25 public:
  26   TRANSLATOR_DECLARATIONS (Time_signature_engraver);
  27 };
  28
  29
  30 Time_signature_engraver::Time_signature_engraver ()
  31 {
  32   time_signature_ = 0;
  33   last_time_fraction_ = SCM_BOOL_F;
  34 }
  35
  36 void
  37 Time_signature_engraver::process_music ()
  38 {
  39   /*
  40     not rigorously safe, since the value might get GC'd and
  41     reallocated in the same spot */
  42   SCM fr = get_property ("timeSignatureFraction");
  43   if (!time_signature_
  44       && last_time_fraction_ != fr
  45       && scm_is_pair (fr))
  46     {
  47       int den = scm_to_int (scm_cdr (fr));
  48       if (den != (1 << intlog2 (den)))
  49         {
  50           /*
  51             Todo: should make typecheck?
  52
  53             OTOH, Tristan Keuris writes 8/20 in his Intermezzi.
  54            */
  55           warning (_f ("Found strange time signature %d/%d.",
  56                       den,
  57                       scm_to_int (scm_car (fr))
  58                       ));
  59         }
  60
  61
  62       last_time_fraction_ = fr;
  63       time_signature_ = make_item ("TimeSignature",SCM_EOL);
  64       time_signature_->set_property ("fraction",fr);
  65     }
  66 }
  67
  68 void
  69 Time_signature_engraver::stop_translation_timestep ()
  70 {
  71   time_signature_ = 0;
  72 }
  73
  74
  75 ADD_TRANSLATOR (Time_signature_engraver,
  76 /* descr */       "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  77 /* creats*/       "TimeSignature",
  78 /* accepts */     "",
  79 /* acks  */      "",
  80 /* reads */       "",
  81 /* write */       "");