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--2002 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9 #include "time-signature.hh"
  10
  11 #include "engraver.hh"
  12 #include "engraver-group-engraver.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_ && last_time_fraction_ != fr)
  44     {
  45       last_time_fraction_ = fr;
  46       time_signature_ = new Item (get_property ("TimeSignature"));
  47       time_signature_->set_grob_property ("fraction",fr);
  48
  49       if (time_signature_)
  50         announce_grob(time_signature_, SCM_EOL);
  51     }
  52 }
  53
  54 void
  55 Time_signature_engraver::stop_translation_timestep ()
  56 {
  57   if (time_signature_)
  58     {
  59       typeset_grob (time_signature_);
  60       time_signature_ =0;
  61     }
  62 }
  63
  64
  65 ENTER_DESCRIPTION(Time_signature_engraver,
  66 /* descr */       "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  67 /* creats*/       "TimeSignature",
  68 /* accepts */     "",
  69 /* acks  */      "",
  70 /* reads */       "",
  71 /* write */       "");