lily/output-property-engraver.cc

   1 /*
   2   output-property-engraver.cc --  implement Output_property_engraver
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 2000--2001 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7
   8  */
   9
  10 #include "engraver.hh"
  11 #include "grob.hh"
  12 #include "output-property-music-iterator.hh"
  13
  14 class Output_property_engraver : public Engraver
  15 {
  16 public:
  17   VIRTUAL_COPY_CONS (Translator);
  18 protected:
  19
  20   /*
  21     should do this with \once and \push ?
  22
  23
  24       \property Voice.outputProperties \push #pred = #modifier
  25
  26       where both MODIFIER and PRED are functions taking a
  27       grob.
  28
  29    */
  30
  31
  32   Link_array<Music> props_;
  33
  34   virtual void stop_translation_timestep ();
  35   virtual void acknowledge_grob (Grob_info);
  36   virtual bool try_music (Music*);
  37 };
  38
  39
  40 bool
  41 Output_property_engraver::try_music (Music* m)
  42 {
  43   if (m->get_mus_property ("iterator-ctor") ==
  44       Output_property_music_iterator::constructor_cxx_function)
  45     {
  46       props_.push (m);
  47       return true;
  48     }
  49   return false;
  50 }
  51
  52 void
  53 Output_property_engraver::acknowledge_grob (Grob_info inf)
  54 {
  55   for (int i=props_.size (); i--;)
  56     {
  57       Music * o = props_[i];
  58       SCM pred = o->get_mus_property ("predicate");
  59
  60       /*
  61         should typecheck pred.
  62        */
  63       SCM result=gh_apply (pred,
  64                            gh_list (inf.elem_l_->self_scm (), SCM_UNDEFINED));
  65       if (to_boolean (result))
  66         {
  67           SCM sym = o->get_mus_property ("symbol");
  68           SCM val = o->get_mus_property ("value");
  69           inf.elem_l_->set_grob_property (sym, val);
  70         }
  71     }
  72 }
  73
  74 void
  75 Output_property_engraver::stop_translation_timestep ()
  76 {
  77   props_.clear ();
  78 }
  79
  80 ADD_THIS_TRANSLATOR (Output_property_engraver);