Corrected on_line for better ledger lines for different staves.

Signed-off-by: Neil Puttock <n.puttock@gmail.com>

4 files changed, 81 insertions, 3 deletions

diff --git a/input/regression/ledger-lines-varying-staves.ly b/input/regression/ledger-lines-varying-staves.ly
new file mode 100644
index 0000000000..26c0b4ad69
--- /dev/null
+++ b/input/regression/ledger-lines-varying-staves.ly
@@ -0,0 +1,51 @@
+\version "2.11.52"
+\header {
+  texidoc = "Ledger lines should appear at every other location
+for a variety of staves using both @code{line-count} and
+@code{line-positions}."
+}
+
+notes = \relative c' {
+  \time 3/4
+  c2. | d | e | f
+  g2. | a | b | c
+  d2. | e | f | g
+  a2.
+}
+
+\new Staff {
+  % upper and lower lines both odd
+  #(define mylines '(-1 0 1))
+  \override Staff.StaffSymbol #'line-count = #(length mylines)
+  \override Staff.StaffSymbol #'line-positions = #mylines
+  \notes
+}
+
+\new Staff {
+  % upper and lower lines both even
+  #(define mylines '(-2 0 2))
+  \override Staff.StaffSymbol #'line-positions = #mylines
+
+  \override Staff.StaffSymbol #'line-count = #(length mylines)
+  \notes
+}
+
+\new Staff {
+  % lower line odd, upper line even
+  #(define mylines '(-1 0 2))
+  \override Staff.StaffSymbol #'line-positions = #mylines
+  \override Staff.StaffSymbol #'line-count = #(length mylines)
+  \notes
+}
+
+\new Staff {
+  % odd line count
+  \override Staff.StaffSymbol #'line-count = #5
+  \notes
+}
+
+\new Staff {
+  % even line count
+  \override Staff.StaffSymbol #'line-count = #4
+  \notes
+}
diff --git a/lily/include/staff-symbol.hh b/lily/include/staff-symbol.hh
index 4dacde8b53..6791e7be1c 100644
--- a/lily/include/staff-symbol.hh
+++ b/lily/include/staff-symbol.hh
@@ -24,6 +24,7 @@ public:
   
   static int get_steps (Grob *);
   static int line_count (Grob *);
+  static bool on_line (Grob *me, int pos);
   DECLARE_SCHEME_CALLBACK (print, (SCM));
   DECLARE_SCHEME_CALLBACK (height, (SCM));  
   DECLARE_GROB_INTERFACE();
diff --git a/lily/staff-symbol-referencer.cc b/lily/staff-symbol-referencer.cc
index e8ef99f9dd..d623bd35b3 100644
--- a/lily/staff-symbol-referencer.cc
+++ b/lily/staff-symbol-referencer.cc
@@ -35,8 +35,7 @@ Staff_symbol_referencer::on_staff_line (Grob *me)
 bool
 Staff_symbol_referencer::on_line (Grob *me, int pos)
 {
-  int sz = line_count (me) - 1;
-  return ((pos + sz) % 2) == 0;
+  return Staff_symbol::on_line (me, pos);
 }
 
 bool
diff --git a/lily/staff-symbol.cc b/lily/staff-symbol.cc
index d4aa9e116c..6fefc48010 100644
--- a/lily/staff-symbol.cc
+++ b/lily/staff-symbol.cc
@@ -167,8 +167,35 @@ Staff_symbol::height  (SCM smob)
   return ly_interval2scm (y_ext);
 }
 
+bool
+Staff_symbol::on_line (Grob *me, int pos)
+{
+  SCM line_positions = me->get_property ("line-positions");
+  if (scm_is_pair (line_positions))
+    {
+      Real min_line = HUGE_VAL;
+      Real max_line = -HUGE_VAL;
+      for (SCM s = line_positions; scm_is_pair (s); s = scm_cdr (s))
+	{
+	  Real current_line = scm_to_double (scm_car (s));
+	  if (pos == current_line)
+	    return true;
+	  if (current_line > max_line)
+	    max_line = current_line;
+	  if (current_line < min_line)
+	    min_line = current_line;
+	
+	}
+      if (pos < min_line)
+	return (( (int) (rint (pos - min_line)) % 2) == 0);
+      if (pos > max_line)
+	return (( (int) (rint (pos - max_line)) % 2) == 0);
 
-
+      return false;
+    }
+  else
+    return ((abs (pos + line_count (me)) % 2) == 1);
+}
 
 ADD_INTERFACE (Staff_symbol,
 	       "This spanner draws the lines of a staff.  A staff symbol"