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 Time_signature_engraver::Time_signature_engraver ()
  30 {
  31   time_signature_ = 0;
  32   last_time_fraction_ = SCM_BOOL_F;
  33 }
  34
  35 void
  36 Time_signature_engraver::process_music ()
  37 {
  38   /*
  39     not rigorously safe, since the value might get GC'd and
  40     reallocated in the same spot */
  41   SCM fr = get_property ("timeSignatureFraction");
  42   if (!time_signature_
  43       && last_time_fraction_ != fr
  44       && scm_is_pair (fr))
  45     {
  46       int den = scm_to_int (scm_cdr (fr));
  47       if (den != (1 << intlog2 (den)))
  48         {
  49           /*
  50             Todo: should make typecheck?
  51
  52             OTOH, Tristan Keuris writes 8/20 in his Intermezzi.
  53           */
  54           warning (_f ("strange time signature found: %d/%d",
  55                        den,
  56                        scm_to_int (scm_car (fr))));
  57         }
  58
  59       last_time_fraction_ = fr;
  60       time_signature_ = make_item ("TimeSignature", SCM_EOL);
  61       time_signature_->set_property ("fraction", fr);
  62     }
  63 }
  64
  65 void
  66 Time_signature_engraver::stop_translation_timestep ()
  67 {
  68   time_signature_ = 0;
  69 }
  70
  71 ADD_TRANSLATOR (Time_signature_engraver,
  72                 /* descr */ "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  73                 /* creats*/ "TimeSignature",
  74                 /* accepts */ "",
  75                 /* acks  */ "",
  76                 /* reads */ "",
  77                 /* write */ "");