Issue 630/4: Let Grace_engraver react mostly to GraceChange events

When GraceChange events are not available, this reverts to grace processing
at initialization or at the engraver's process_music call.

diff --git a/lily/grace-engraver.cc b/lily/grace-engraver.cc
index 5afe21e00275561886650dc9ae91e36cbb02d96e..a0962da8889e3fbe0039df940c622aea2662de5a 100644 (file)
--- a/lily/grace-engraver.cc
+++ b/lily/grace-engraver.cc
@@ -19,21 +19,26 @@
 
 #include "engraver.hh"
 #include "context.hh"
+#include "dispatcher.hh"
+#include "listener.hh"
 #include "warn.hh"
 #include "grob-properties.hh"
+#include "stream-event.hh"
+#include "translator.icc"
 
 class Grace_engraver : public Engraver
 {
+  Moment last_moment_;
+  SCM grace_settings_;
   void consider_change_grace_settings ();
 protected:
-  void start_translation_timestep ();
   virtual void derived_mark () const;
-  virtual void initialize ();
+  virtual void process_music ();
+  virtual void start_translation_timestep ();
+  virtual void finalize ();
 
   TRANSLATOR_DECLARATIONS (Grace_engraver);
-  Moment last_moment_;
-  SCM grace_settings_;
-public:
+  DECLARE_LISTENER (grace_change);
 };
 
 Grace_engraver::Grace_engraver ()
@@ -42,17 +47,52 @@ Grace_engraver::Grace_engraver ()
   last_moment_ = Moment (Rational (-1, 1));
 }
 
+// The iterator should usually come before process_music
+IMPLEMENT_LISTENER (Grace_engraver, grace_change);
 void
-Grace_engraver::initialize ()
+Grace_engraver::grace_change (SCM)
 {
   consider_change_grace_settings ();
 }
 
+// if we are in grace time already on initialization, it is unlikely
+// that we'll receive a GraceChange event from the grace iterator yet,
+// so we want to start into grace mode anyway.  The downside is that
+// this will get us confused when given something like
+//
+// \new Voice { \oneVoice \grace { c''8 8 } g'1 }
+//
+// where \grace executes its actions already before \oneVoice, causing
+// different stem directions.
+
+void
+Grace_engraver::start_translation_timestep ()
+{
+  // Only on startup
+  if (last_moment_ == Rational (-1))
+    consider_change_grace_settings ();
+}
+
+// If the grace iterator has moved off to some other context, we might
+// not get to see the ChangeContext event.  In that case, we still
+// want to change into or out of grace mode settings as appropriate
+
+void
+Grace_engraver::process_music ()
+{
+  // We may have lost connection to the iterator in which case we
+  // still need to call consider_change_grace_settings in particular
+  // in order to get out of grace mode again
+  if (last_moment_ != now_mom ())
+    consider_change_grace_settings ();
+}
+
 void
 Grace_engraver::consider_change_grace_settings ()
 {
   Moment now = now_mom ();
-  if (last_moment_.grace_part_ && !now.grace_part_)
+
+  if (!now.grace_part_)
     {
       for (SCM s = grace_settings_; scm_is_pair (s); s = scm_cdr (s))
         {
@@ -63,10 +103,9 @@ Grace_engraver::consider_change_grace_settings ()
 
           Grob_property_info (Context::unsmob (context), grob).matched_pop (cell);
         }
-
       grace_settings_ = SCM_EOL;
     }
-  else if (!last_moment_.grace_part_ && now.grace_part_)
+  else if (!last_moment_.grace_part_)
     {
       SCM settings = get_property ("graceSettings");
 
@@ -97,25 +136,31 @@ Grace_engraver::consider_change_grace_settings ()
                                + ly_symbol2string (context_name));
         }
     }
-
-  last_moment_ = now_mom ();
+  if (last_moment_ == Rational (-1))
+    {
+      Dispatcher *d = context ()->event_source ();
+      d->add_listener (GET_LISTENER (grace_change), ly_symbol2scm ("GraceChange"));
+    }
+  last_moment_ = now;
 }
 
 void
-Grace_engraver::derived_mark () const
+Grace_engraver::finalize ()
 {
-  scm_gc_mark (grace_settings_);
-  Engraver::derived_mark ();
+  if (last_moment_ != Rational (-1))
+    {
+      Dispatcher *d = context ()->event_source ();
+      d->remove_listener (GET_LISTENER (grace_change), ly_symbol2scm ("GraceChange"));
+    }
 }
 
 void
-Grace_engraver::start_translation_timestep ()
+Grace_engraver::derived_mark () const
 {
-  consider_change_grace_settings ();
+  scm_gc_mark (grace_settings_);
+  Engraver::derived_mark ();
 }
 
-#include "translator.icc"
-
 ADD_TRANSLATOR (Grace_engraver,
                 /* doc */
                 "Set font size and other properties for grace notes.",

diff --git a/ly/engraver-init.ly b/ly/engraver-init.ly
index a222e6a7bae768bce128a57c74dac0322df5e2a9..a04145ba0c56716f46b9db86ee6724b75f69ba4c 100644 (file)
--- a/ly/engraver-init.ly
+++ b/ly/engraver-init.ly
@@ -209,7 +209,8 @@ subscripts, slurs, ties, and rests.
 
 You have to instantiate this explicitly if you want to have
 multiple voices on the same staff."
-
+  %% Grace_engraver sets properties, it must come first.
+  \consists "Grace_engraver"
   \consists "Font_size_engraver"
 
   \consists "Pitched_trill_engraver"
@@ -265,7 +266,6 @@ multiple voices on the same staff."
   \consists "Slur_engraver"
   \consists "Tie_engraver"
   \consists "Tuplet_engraver"
-  \consists "Grace_engraver"
   \consists "Instrument_switch_engraver"
 }