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 (s == ly_symbol2scm ("always")
  31       || (s == SCM_EOL
  32           && to_boolean (get_property ("soloADue"))
  33           && ((daddy_trans_->id_string_.left_string (3) == "two"
  34                && (to_boolean (get_property ("unison"))
  35                    || to_boolean (get_property ("unisilence"))))
  36
  37               /* Maybe this should be optional? */
  38               || to_boolean (get_property ("othersolo")))))
  39     {
  40       i.grob_->suicide ();
  41     }
  42 }
  43 Thread_devnull_engraver::Thread_devnull_engraver(){}
  44
  45 ENTER_DESCRIPTION(Thread_devnull_engraver,
  46 /* descr */       "Kill elements whenever we are Voice called `two' and either "
  47 "unison, unisilence or soloADue is set.@footnote{On unix systems, the "
  48 "file @file{/dev/null} is special device: anything written to it is "
  49 "discarded.}. This engraver works closely together with the part "
  50 "combiner.  When the part combiner notices that two threads are "
  51 "identical, it tells the @code{Thread_devnull_engraver} to discard "
  52 "everything in the second thread. "
  53 ,
  54 /* creats*/       "",
  55 /* accepts */     "",
  56 /* acks  */      "grob-interface",
  57 /* reads */       "",
  58 /* write */       "");