prevent collision of ligatures and next note (issue 6740046)

[benko . pal]

Reviewers: ,

Message:
mensural-ligatures.ly is listed as changed - that is not surprising,
although I couldn't tell in advance _how_ it will change.  what is a bit
more surprising that I can't tell even now, having seen the regtest
comparison.

Description:
prevent collision of ligatures and next note

Please review this at http://codereview.appspot.com/6740046/

Affected files:
  M lily/mensural-ligature-engraver.cc
  M scm/define-grobs.scm


Index: lily/mensural-ligature-engraver.cc
diff --git a/lily/mensural-ligature-engraver.cc  
b/lily/mensural-ligature-engraver.cc
index  
35b8614b0d62fa2a657510c68b9ac3fc35e37144..848ca0cb4b003a11a0e3cc63cbfe78f1065d7a0a  
100644
--- a/lily/mensural-ligature-engraver.cc
+++ b/lily/mensural-ligature-engraver.cc
@@ -64,9 +64,11 @@ public:
   TRANSLATOR_DECLARATIONS (Mensural_ligature_engraver);

 private:
-  void transform_heads (vector<Grob_info> primitives);
-  void propagate_properties (Spanner *ligature, vector<Grob_info>  
primitives);
-  void fold_up_primitives (vector<Grob_info> primitives);
+  void transform_heads (vector<Grob_info> const &primitives);
+  void propagate_properties (Spanner *ligature,
+                             vector<Grob_info> const &primitives);
+  void fold_up_primitives (Spanner *ligature,
+                           vector<Grob_info> const &primitives);
 };

 IMPLEMENT_TRANSLATOR_LISTENER (Mensural_ligature_engraver, ligature);
@@ -89,7 +91,7 @@ Mensural_ligature_engraver::create_ligature_spanner ()
 }

 void
-Mensural_ligature_engraver::transform_heads (vector<Grob_info> primitives)
+Mensural_ligature_engraver::transform_heads (vector<Grob_info> const  
&primitives)
 {
   if (primitives.size () < 2)
     {
@@ -336,7 +338,7 @@ Mensural_ligature_engraver::transform_heads  
(vector<Grob_info> primitives)
  */
 void
 Mensural_ligature_engraver::propagate_properties (Spanner *ligature,
-                                                  vector<Grob_info>  
primitives)
+                                                  vector<Grob_info> const  
&primitives)
 {
   Real thickness
     = robust_scm2double (ligature->get_property ("thickness"), 1.3);
@@ -349,6 +351,7 @@ Mensural_ligature_engraver::propagate_properties  
(Spanner *ligature,
   Real maxima_head_width
     = Font_interface::get_default_font (ligature)->
       find_by_name ("noteheads.sM3ligmensural").extent (X_AXIS).length ();
+  Real min_length = 0.0;

   Item *prev_primitive = NULL;
   for (vsize i = 0; i < primitives.size (); i++)
@@ -362,9 +365,11 @@ Mensural_ligature_engraver::propagate_properties  
(Spanner *ligature,
         {
         case MLP_BREVIS:
         case MLP_LONGA:
+          min_length += head_width;
           primitive->set_property ("head-width", scm_from_double  
(head_width));
           break;
         case MLP_MAXIMA:
+          min_length += maxima_head_width;
           primitive->set_property ("head-width",
                                    scm_from_double (maxima_head_width));
           break;
@@ -377,6 +382,7 @@ Mensural_ligature_engraver::propagate_properties  
(Spanner *ligature,
           {
             SCM flexa_scm = primitive->get_property ("flexa-width");
             Real const flexa_width = robust_scm2double (flexa_scm, 2.0);
+            min_length += flexa_width + thickness;
             SCM head_width = scm_from_double (0.5 * (flexa_width +  
thickness));
             primitive->set_property ("head-width", head_width);
             prev_primitive->set_property ("head-width", head_width);
@@ -390,10 +396,13 @@ Mensural_ligature_engraver::propagate_properties  
(Spanner *ligature,

       prev_primitive = primitive;
     }
+
+  ligature->set_property ("minimum-length", scm_from_double (min_length));
 }

 void
-Mensural_ligature_engraver::fold_up_primitives (vector<Grob_info>  
primitives)
+Mensural_ligature_engraver::fold_up_primitives (Spanner *ligature,
+                                                vector<Grob_info> const  
&primitives)
 {
   Item *first = 0;
   Real distance = 0.0;
@@ -416,7 +425,7 @@ Mensural_ligature_engraver::fold_up_primitives  
(vector<Grob_info> primitives)
       Real head_width = scm_to_double (current->get_property  
("head-width"));
       distance += head_width - thickness;

-      if (Rhythmic_head::dot_count (current) > 0)
+      if (size_t const dot_count = Rhythmic_head::dot_count (current))
         /*
           Move dots above/behind the ligature.
           dots should also avoid staff lines.
@@ -452,6 +461,12 @@ Mensural_ligature_engraver::fold_up_primitives  
(vector<Grob_info> primitives)
               else if (delta == 1 || delta == -1)
                 vert_shift -= delta * staff_space;
             }
+          else
+            ligature->set_property
+              ("minimum-length",
+               scm_from_double
+               (head_width*dot_count + robust_scm2double
+                (ligature->get_property ("minimum-length"), 0.0)));

           dot_gr->translate_axis (vert_shift, Y_AXIS);

@@ -470,7 +485,7 @@ Mensural_ligature_engraver::build_ligature (Spanner  
*ligature,
 {
   transform_heads (primitives);
   propagate_properties (ligature, primitives);
-  fold_up_primitives (primitives);
+  fold_up_primitives (ligature, primitives);
 }

 ADD_ACKNOWLEDGER (Mensural_ligature_engraver, rest);
Index: scm/define-grobs.scm
diff --git a/scm/define-grobs.scm b/scm/define-grobs.scm
index  
28bc6d04d4199d2f0528b3b5ecce554f7ff93f68..1ebd9c34e88263d05d7b92dccb541b848e62d332  
100644
--- a/scm/define-grobs.scm
+++ b/scm/define-grobs.scm
@@ -1343,6 +1343,7 @@

     (MensuralLigature
      . (
+       (springs-and-rods . ,ly:spanner::set-spacing-rods)
        (stencil . ,ly:mensural-ligature::print)
        (thickness . 1.3)
        (meta . ((class . Spanner)