From eb71b343f91d1fbe1842f653fb285e12934ed072 Mon Sep 17 00:00:00 2001
From: Joe Neeman <joeneeman@gmail.com>
Date: Thu, 6 Aug 2009 07:57:41 +1000
Subject: [PATCH] Fix 462.

Mark invisible barlines as loose columns.
---
 input/regression/spacing-empty-bar.ly   | 10 ++++++++++
 lily/paper-column.cc                    |  1 +
 lily/spacing-determine-loose-columns.cc | 26 ++++++++++++++++++++-----
 lily/spacing-spanner.cc                 |  2 +-
 scm/define-grob-properties.scm          |  2 ++
 5 files changed, 35 insertions(+), 6 deletions(-)
 create mode 100644 input/regression/spacing-empty-bar.ly

diff --git a/input/regression/spacing-empty-bar.ly b/input/regression/spacing-empty-bar.ly
new file mode 100644
index 0000000000..3a8cd9c435
--- /dev/null
+++ b/input/regression/spacing-empty-bar.ly
@@ -0,0 +1,10 @@
+\version "2.13.4"
+
+\header {
+  texidoc = "Empty barlines do not affect spacing."
+}
+
+{
+  c'4 c' \bar "" c' c' \break
+  \repeat unfold 10 { c' c' c' c' \bar "" \noBreak }
+}
\ No newline at end of file
diff --git a/lily/paper-column.cc b/lily/paper-column.cc
index e8533e9453..3308cf251c 100644
--- a/lily/paper-column.cc
+++ b/lily/paper-column.cc
@@ -365,6 +365,7 @@ ADD_INTERFACE (Paper_column,
 	       "line-break-system-details "
 	       "line-break-penalty "
 	       "line-break-permission "
+	       "maybe-loose "
 	       "page-break-penalty "
 	       "page-break-permission "
 	       "page-turn-penalty "
diff --git a/lily/spacing-determine-loose-columns.cc b/lily/spacing-determine-loose-columns.cc
index 7aa42caece..90db1e01e1 100644
--- a/lily/spacing-determine-loose-columns.cc
+++ b/lily/spacing-determine-loose-columns.cc
@@ -47,8 +47,7 @@ is_loose_column (Grob *l, Grob *col, Grob *r, Spacing_options const *options)
     }
 
   
-  if (Paper_column::is_musical (col)
-      || Paper_column::is_breakable (col))
+  if (Paper_column::is_musical (col))
     return false;
 
   /*
@@ -79,8 +78,11 @@ is_loose_column (Grob *l, Grob *col, Grob *r, Spacing_options const *options)
   if (!l_neighbor || !r_neighbor)
     return false;
 
-  if (l == l_neighbor && r == r_neighbor)
-    return false;
+  /* If a non-empty column (ie. not \bar "") is placed nicely in series with
+     its neighbor (ie. no funny polyphonic stuff), don't make it loose.
+  */
+  if (l == l_neighbor && r == r_neighbor && col->extent (col, X_AXIS).length () > 0)
+     return false;
 
   /*
     Only declare loose if the bounds make a little sense.  This means
@@ -106,7 +108,12 @@ is_loose_column (Grob *l, Grob *col, Grob *r, Spacing_options const *options)
 	      Grob *h = gelts[j];
 
 	      if (h && h->get_property ("break-align-symbol") == ly_symbol2scm ("staff-bar"))
-		return false;
+		{
+		  extract_grob_set (h, "elements", helts);
+		  for (vsize k = helts.size (); k--;)
+		    if ("" != robust_scm2string (helts[k]->get_property ("glyph-name"), ""))
+		      return false;
+		}
 	    }
 	}
     }
@@ -185,6 +192,15 @@ Spacing_spanner::prune_loose_columns (Grob *me,
       bool loose = (i > 0 && i + 1 < cols->size ())
 	&& is_loose_column (cols->at (i - 1), c, cols->at (i + 1), options);
 
+      /* Breakable columns never get pruned; even if they are loose,
+        their broken pieces are not.  However, we mark them so that
+        the spacing can take their mid-line looseness into account. */
+      if (loose && Paper_column::is_breakable (c))
+	{
+	  loose = false;
+	  c->set_property ("maybe-loose", SCM_BOOL_T);
+	}
+
       if (loose)
 	{
 	  Grob *right_neighbor = unsmob_grob (c->get_object ("right-neighbor"));
diff --git a/lily/spacing-spanner.cc b/lily/spacing-spanner.cc
index 274905faf5..cc5170de79 100644
--- a/lily/spacing-spanner.cc
+++ b/lily/spacing-spanner.cc
@@ -168,7 +168,7 @@ Spacing_spanner::generate_pair_spacing (Grob *me,
   if (Paper_column::is_musical (left_col))
     {
       if (!Paper_column::is_musical (right_col)
-	  && options->float_nonmusical_columns_
+	  && (options->float_nonmusical_columns_ || to_boolean (right_col->get_property ("maybe-loose")))
 	  && after_right_col
 	  && Paper_column::is_musical (after_right_col))
 	{
diff --git a/scm/define-grob-properties.scm b/scm/define-grob-properties.scm
index ac09201044..bdd702bce9 100644
--- a/scm/define-grob-properties.scm
+++ b/scm/define-grob-properties.scm
@@ -1004,6 +1004,8 @@ supported by this object.  It is initialized from the @code{meta} field.")
 
      (least-squares-dy ,number? "The ideal beam slope, without damping.")
 
+     (maybe-loose ,boolean? "Used to mark a breakable column that is
+loose if and only if it is in the middle of a line.")
      (meta ,list? "Provide meta information.  It is an alist with the
 entries @code{name} and @code{interfaces}.")
      (minimum-distances ,list? "A list of rods that have the format
-- 
2.39.5