Allows slurs to break at barlines.

lily/phrasing-slur-engraver.cc

Index: lily/phrasing-slur-engraver.cc
diff --git a/lily/phrasing-slur-engraver.cc b/lily/phrasing-slur-engraver.cc
index 7e6c3c63fe3d8b0e026022e2ad555d767ca4dfda..2830f4a3dc29a4b488b2fb47e6dc26958bbe54e6 100644
--- a/lily/phrasing-slur-engraver.cc
+++ b/lily/phrasing-slur-engraver.cc
@@ -52,9 +52,11 @@ class Phrasing_slur_engraver : public Engraver
   vector<Grob *> slurs_;
   vector<Grob *> end_slurs_;
   vector<Grob_info> objects_to_acknowledge_;
+  Stream_event *break_slur_;
 
 protected:
   DECLARE_TRANSLATOR_LISTENER (phrasing_slur);
+  DECLARE_TRANSLATOR_LISTENER (break_phrasing_slur);
   DECLARE_ACKNOWLEDGER (inline_accidental);
   DECLARE_ACKNOWLEDGER (fingering);
   DECLARE_ACKNOWLEDGER (note_column);
@@ -102,6 +104,13 @@ Phrasing_slur_engraver::listen_phrasing_slur (Stream_event *ev)
                                      "phrasing-slur-event", int (d)));
 }
 
+IMPLEMENT_TRANSLATOR_LISTENER (Phrasing_slur_engraver, break_phrasing_slur);
+void
+Phrasing_slur_engraver::listen_break_phrasing_slur (Stream_event *ev)
+{
+  ASSIGN_EVENT_ONCE (break_slur_, ev);
+}
+
 void
 Phrasing_slur_engraver::acknowledge_note_column (Grob_info info)
 {
@@ -181,6 +190,34 @@ Phrasing_slur_engraver::finalize ()
 void
 Phrasing_slur_engraver::process_music ()
 {
+  if (break_slur_
+      && unsmob_grob (get_property ("currentCommandColumn")))
+    {
+      for (vsize i = slurs_.size (); i--;)
+        {
+          Grob *ccc = unsmob_grob (get_property ("currentCommandColumn"));
+          Spanner *s = dynamic_cast<Spanner *> (slurs_[i]);
+          s->set_bound (RIGHT, ccc);
+          announce_end_grob (s, SCM_EOL);
+          slurs_.erase (slurs_.begin () + i);
+          if (robust_scm2dir (break_slur_->get_property ("side-to-junk"), CENTER) == LEFT)
+            s->suicide ();
+
+          if (robust_scm2dir (break_slur_->get_property ("side-to-junk"), CENTER) != RIGHT)
+            {
+              SCM spanner_id = s->get_property ("spanner-id");
+              Spanner *slur = make_spanner ("Slur", s->self_scm ());
+              slur->set_property ("spanner-id", spanner_id);
+              if (scm_is_number (s->get_property_data ("direction")))
+                set_grob_direction (slur, robust_scm2dir (s->get_property ("direction"), UP));
+              slur->set_bound (LEFT, ccc);
+              slurs_.push_back (slur);
+            }
+        }
+    }
+  else if (to_boolean (get_property ("breakSlurHere")))
+    warning ("no current command column to break slur");
+
   for (vsize i = 0; i < stop_events_.size (); i++)
     {
       Stream_event *ev = stop_events_[i];
@@ -305,6 +342,7 @@ Phrasing_slur_engraver::stop_translation_timestep ()
   end_slurs_.clear ();
   start_events_.clear ();
   stop_events_.clear ();
+  break_slur_ = 0;
 }
 
 ADD_ACKNOWLEDGER (Phrasing_slur_engraver, inline_accidental);