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