lily/time-signature-engraver.cc

   1 /*
   2   time_signature-reg.cc -- implement Time_signature_engraver
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c)  1997--2001 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7 */
   8
   9 #include "time-signature.hh"
  10 #include "command-request.hh"
  11 #include "engraver.hh"
  12
  13
  14 #include "engraver-group-engraver.hh"
  15
  16
  17 /**
  18   generate time_signatures.
  19   */
  20 class Time_signature_engraver : public Engraver
  21 {
  22   Item * time_signature_p_;
  23   SCM last_time_fraction_;
  24
  25 protected:
  26   virtual void stop_translation_timestep ();
  27   virtual void create_grobs ();
  28 public:
  29   TRANSLATOR_DECLARATIONS(Time_signature_engraver);
  30
  31 };
  32
  33
  34 Time_signature_engraver::Time_signature_engraver ()
  35 {
  36   time_signature_p_ =0;
  37   last_time_fraction_ = SCM_BOOL_F;
  38 }
  39
  40 void
  41 Time_signature_engraver::create_grobs ()
  42 {
  43   /*
  44     not rigorously safe, since the value might get GC'd and
  45     reallocated in the same spot */
  46   SCM fr= get_property ("timeSignatureFraction");
  47   if (!time_signature_p_ && last_time_fraction_ != fr)
  48     {
  49       last_time_fraction_ = fr;
  50       time_signature_p_ = new Item (get_property ("TimeSignature"));
  51       time_signature_p_->set_grob_property ("fraction",fr);
  52
  53       if (time_signature_p_)
  54         announce_grob (time_signature_p_, 0);
  55     }
  56
  57 }
  58
  59
  60
  61 void
  62 Time_signature_engraver::stop_translation_timestep ()
  63 {
  64   if (time_signature_p_)
  65     {
  66       typeset_grob (time_signature_p_);
  67       time_signature_p_ =0;
  68     }
  69 }
  70
  71
  72
  73
  74
  75 ENTER_DESCRIPTION(Time_signature_engraver,
  76 /* descr */       "Create a TimeSignature whenever @code{timeSignatureFraction} changes",
  77 /* creats*/       "TimeSignature",
  78 /* acks  */       "",
  79 /* reads */       "",
  80 /* write */       "");