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--2004 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9 #include "time-signature.hh"
  10 #include "warn.hh"
  11
  12 #include "engraver.hh"
  13 #include "engraver-group-engraver.hh"
  14 #include "misc.hh"
  15
  16 /**
  17   generate time_signatures.
  18   */
  19 class Time_signature_engraver : public Engraver
  20 {
  21   Item *time_signature_;
  22   SCM last_time_fraction_;
  23
  24 protected:
  25   virtual void stop_translation_timestep ();
  26   virtual void process_music ();
  27 public:
  28   TRANSLATOR_DECLARATIONS (Time_signature_engraver);
  29 };
  30
  31
  32 Time_signature_engraver::Time_signature_engraver ()
  33 {
  34   time_signature_ = 0;
  35   last_time_fraction_ = SCM_BOOL_F;
  36 }
  37
  38 void
  39 Time_signature_engraver::process_music ()
  40 {
  41   /*
  42     not rigorously safe, since the value might get GC'd and
  43     reallocated in the same spot */
  44   SCM fr = get_property ("timeSignatureFraction");
  45   if (!time_signature_
  46       && last_time_fraction_ != fr
  47       && scm_is_pair (fr))
  48     {
  49       int den = scm_to_int (scm_cdr (fr));
  50       if (den != (1 << intlog2 (den)))
  51         {
  52           /*
  53             Todo: should make typecheck?
  54
  55             OTOH, Tristan Keuris writes 8/20 in his Intermezzi.
  56            */
  57           warning (_f ("Found strange time signature %d/%d.",
  58                       den,
  59                       scm_to_int (scm_car (fr))
  60                       ));
  61         }
  62
  63
  64       last_time_fraction_ = fr;
  65       time_signature_ = make_item ("TimeSignature",SCM_EOL);
  66       time_signature_->set_property ("fraction",fr);
  67     }
  68 }
  69
  70 void
  71 Time_signature_engraver::stop_translation_timestep ()
  72 {
  73   time_signature_ = 0;
  74 }
  75
  76
  77 ENTER_DESCRIPTION (Time_signature_engraver,
  78 /* descr */       "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  79 /* creats*/       "TimeSignature",
  80 /* accepts */     "",
  81 /* acks  */      "",
  82 /* reads */       "",
  83 /* write */       "");