lily/thread-devnull-engraver.cc

   1 /*
   2   thread-devnull-engraver.cc -- implement Thread_devnull_engraver
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 2000--2003 Jan Nieuwenhuizen <janneke@gnu.org>
   7 */
   8
   9 #include "engraver.hh"
  10 #include "item.hh"
  11 #include "event.hh"
  12 #include "translator-group.hh"
  13
  14 class Thread_devnull_engraver : public Engraver
  15 {
  16 public:
  17   TRANSLATOR_DECLARATIONS(Thread_devnull_engraver);
  18
  19 protected:
  20   virtual void acknowledge_grob (Grob_info);
  21 };
  22
  23
  24
  25 void
  26 Thread_devnull_engraver::acknowledge_grob (Grob_info i)
  27 {
  28   SCM s = get_property ("devNullThread");
  29
  30 #if 0
  31   /* No need, next if will never be true */
  32   if (s == ly_symbol2scm ("never"))
  33     return;
  34 #endif
  35
  36   if (s == ly_symbol2scm ("always")
  37       || (s == SCM_EOL
  38           && to_boolean (get_property ("soloADue"))
  39           && ((daddy_trans_->id_string_.left_string (3) == "two"
  40                && (to_boolean (get_property ("unison"))
  41                    || to_boolean (get_property ("unisilence"))))
  42
  43               /* Maybe this should be optional? */
  44               || to_boolean (get_property ("othersolo")))))
  45     {
  46       i.grob_->suicide ();
  47     }
  48 }
  49 Thread_devnull_engraver::Thread_devnull_engraver(){}
  50
  51 ENTER_DESCRIPTION(Thread_devnull_engraver,
  52 /* descr */       "Kill elements whenever we are Voice called `two' and either "
  53 "unison, unisilence or soloADue is set.@footnote{On unix systems, the "
  54 "file @file{/dev/null} is special device: anything written to it is "
  55 "discarded.}. This engraver works closely together with the part "
  56 "combiner.  When the part combiner notices that two threads are "
  57 "identical, it tells the @code{Thread_devnull_engraver} to discard "
  58 "everything in the second thread. "
  59 ,
  60 /* creats*/       "",
  61 /* accepts */     "",
  62 /* acks  */      "grob-interface",
  63 /* reads */       "",
  64 /* write */       "");