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--2006 Han-Wen Nienhuys <hanwen@xs4all.nl>
   7 */
   8
   9 #include "engraver-group.hh"
  10
  11 #include "international.hh"
  12 #include "misc.hh"
  13 #include "time-signature.hh"
  14 #include "warn.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 derived_mark () const;
  26   void stop_translation_timestep ();
  27   void process_music ();
  28 public:
  29   TRANSLATOR_DECLARATIONS (Time_signature_engraver);
  30 };
  31
  32 void
  33 Time_signature_engraver::derived_mark () const
  34 {
  35   scm_gc_mark (last_time_fraction_);
  36 }
  37
  38 Time_signature_engraver::Time_signature_engraver ()
  39 {
  40   time_signature_ = 0;
  41   last_time_fraction_ = SCM_BOOL_F;
  42 }
  43
  44 void
  45 Time_signature_engraver::process_music ()
  46 {
  47   /*
  48     not rigorously safe, since the value might get GC'd and
  49     reallocated in the same spot */
  50   SCM fr = get_property ("timeSignatureFraction");
  51   if (!time_signature_
  52       && last_time_fraction_ != fr
  53       && scm_is_pair (fr))
  54     {
  55       int den = scm_to_int (scm_cdr (fr));
  56       if (den != (1 << intlog2 (den)))
  57         {
  58           /*
  59             Todo: should make typecheck?
  60
  61             OTOH, Tristan Keuris writes 8/20 in his Intermezzi.
  62           */
  63           warning (_f ("strange time signature found: %d/%d",
  64                        den,
  65                        scm_to_int (scm_car (fr))));
  66         }
  67
  68       last_time_fraction_ = fr;
  69       time_signature_ = make_item ("TimeSignature", SCM_EOL);
  70       time_signature_->set_property ("fraction", fr);
  71     }
  72 }
  73
  74 void
  75 Time_signature_engraver::stop_translation_timestep ()
  76 {
  77   time_signature_ = 0;
  78 }
  79
  80 #include "translator.icc"
  81
  82 ADD_TRANSLATOR (Time_signature_engraver,
  83                 /* doc */ "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  84                 /* create */ "TimeSignature",
  85                 /* read */ "",
  86                 /* write */ "");