From d31881bf4e0a6f26efd0ad3715e0abf2804f0abd Mon Sep 17 00:00:00 2001
From: Neil Puttock <n.puttock@gmail.com>
Date: Sun, 14 Sep 2008 21:23:25 +0100
Subject: [PATCH] Break-alignable metronome marks.

---
 lily/metronome-engraver.cc | 42 ++++++++++++++++++++++++++++++++++++--
 scm/define-grobs.scm       | 10 +++++++++
 2 files changed, 50 insertions(+), 2 deletions(-)

diff --git a/lily/metronome-engraver.cc b/lily/metronome-engraver.cc
index 9d585af827..f3f04f1d3c 100644
--- a/lily/metronome-engraver.cc
+++ b/lily/metronome-engraver.cc
@@ -42,6 +42,9 @@ protected:
   SCM last_duration_;
   SCM last_count_;
   SCM last_text_;
+
+  DECLARE_ACKNOWLEDGER (break_aligned);
+  DECLARE_ACKNOWLEDGER (break_alignment);
   
 protected:
   virtual void derived_mark () const;
@@ -65,13 +68,43 @@ Metronome_mark_engraver::derived_mark () const
   scm_gc_mark (last_text_);
 }
 
+void
+Metronome_mark_engraver::acknowledge_break_aligned (Grob_info inf)
+{
+  Grob *s = inf.grob ();
+  if (text_
+      && !text_->get_parent (X_AXIS)
+      && dynamic_cast<Item *> (s)
+      && (s->get_property_data ("break-align-symbol")
+	  == text_->get_property_data ("break-align-symbol")))
+    text_->set_parent (s, X_AXIS);
+}
+
+void
+Metronome_mark_engraver::acknowledge_break_alignment (Grob_info inf)
+{
+  Grob *s = inf.grob ();
+  if (text_
+      && dynamic_cast<Item *> (s))
+    {
+      text_->set_parent (s, X_AXIS);
+    }
+}
+
+
 void
 Metronome_mark_engraver::stop_translation_timestep ()
 {
   if (text_)
     {
-      Grob *mc = unsmob_grob (get_property ("currentMusicalColumn"));
-      text_->set_parent (mc, X_AXIS);
+      /*
+	Problem: how to set musical columns as parent
+	when there's no breakable object of interest nearby?
+	We don't want metronome marks aligned to paper columns.
+       
+	Grob *mc = unsmob_grob (get_property ("currentMusicalColumn"));
+	text_->set_parent (mc, X_AXIS);
+      */
       text_->set_object ("side-support-elements",
 			 grob_list_to_grob_array (get_property ("stavesFound")));
       text_ = 0;
@@ -108,6 +141,11 @@ Metronome_mark_engraver::process_music ()
   last_text_ = text;
 }
 
+
+
+ADD_ACKNOWLEDGER (Metronome_mark_engraver, break_aligned);
+ADD_ACKNOWLEDGER (Metronome_mark_engraver, break_alignment);
+
 ADD_TRANSLATOR (Metronome_mark_engraver,
 		/* doc */
 		"Engrave metronome marking.  This delegates the formatting"
diff --git a/scm/define-grobs.scm b/scm/define-grobs.scm
index 2860bc3e6a..88883dc48e 100644
--- a/scm/define-grobs.scm
+++ b/scm/define-grobs.scm
@@ -1162,10 +1162,19 @@
 	(side-axis . ,Y)
 	(stencil . ,ly:text-interface::print)
 	(Y-offset . ,ly:side-position-interface::y-aligned-side)
+	(X-offset . ,(ly:make-simple-closure
+		      `(,+
+			,(ly:make-simple-closure
+			  (list ly:break-alignable-interface::self-align-callback))
+			,(ly:make-simple-closure
+			  (list ly:self-alignment-interface::x-aligned-on-self)))))
+	(self-alignment-X . -1)
+	(break-align-symbols . (time-signature))
 	(meta . ((class . Item)
 		 (interfaces . (font-interface
 				metronome-mark-interface
 				side-position-interface
+				break-alignable-interface
 				text-interface))))))
 
     (MultiMeasureRest
@@ -2091,6 +2100,7 @@
 	(break-align-anchor
 	 . ,ly:break-aligned-interface::calc-extent-aligned-anchor)
 	(break-align-symbol . time-signature)
+	(break-align-anchor-alignment . ,LEFT)
 	(break-visibility . ,all-visible)
 	(extra-spacing-height . (-1.0 . 1.0))
 	(non-musical . #t)
-- 
2.39.2