Ends of barlines are hidden in staff lines. (issue4809057)

[lemniskata . bernoullego]

Reviewers: hanwenn,

Message:

http://lists.gnu.org/archive/html/lilypond-devel/2011-07/msg01051.html
2011/7/27 Han-Wen Nienhuys <address@hidden>:

> > > Due to rounding, PDF viewers can err
> > > the placement of the barline by a pixel.
> > > [so that it looks like sticking out of staff]

> You can make the problem disappear by

> - hard coding the output to a certain resolution
> - making the bar go to the middle of the staffline,
>    rather than the outside.

> both have disadvantages.

This patch does the second thing.  What disadvantages do you see besides
what happens when barline and staff have different colors?

cheers,
Janek

Description:
Ends of barlines are hidden in staff lines.

Barlines are made a little shorter, so that the end of the barline
doesn't touch
the outer edge of staff line - it ends in the middle of staff line now.
This prevets artifacts in pdf viewing and printing.

Please review this at http://codereview.appspot.com/4809057/

Affected files:
  M lily/bar-line.cc
  M lily/include/staff-symbol-referencer.hh
  M lily/staff-symbol-referencer.cc


Index: lily/bar-line.cc
diff --git a/lily/bar-line.cc b/lily/bar-line.cc
index  
a2d6588726bb823c03075ca65dc35b663ecffaa3..64ca4d0dbd7bbb80f8c8aa87e4ec8966e2d7e58d  
100644
--- a/lily/bar-line.cc
+++ b/lily/bar-line.cc
@@ -34,8 +34,22 @@ Bar_line::calc_bar_extent (SCM smob)
   Interval result;
   Grob *me = unsmob_grob (smob);
   if (Grob *staff = Staff_symbol_referencer::get_staff_symbol (me))
-    result = staff->extent (staff, Y_AXIS);
-
+    {
+      result = staff->extent (staff, Y_AXIS);
+
+      /* Due to rounding problems, barlines extending to the outermost  
edges
+         of the staff lines appear wrongly in on-screen display
+         (and, to a lesser extent, in print) - they stick out a pixel.
+         The solution is to extend barlines only to the middle
+         of the staff line - unless they have different colors,
+         when it would be undesirable.
+      */
+      SCM bar_line_color = me->get_property ("color");
+      SCM staff_color = Staff_symbol_referencer::color (me);
+      if (bar_line_color == staff_color)
+       result *= (1 - 0.5 * (Staff_symbol_referencer::line_thickness (me) /
+                             Staff_symbol_referencer::staff_radius (me)));
+    }
   return ly_interval2scm (result);
 }

Index: lily/include/staff-symbol-referencer.hh
diff --git a/lily/include/staff-symbol-referencer.hh  
b/lily/include/staff-symbol-referencer.hh
index  
ed6156c62c78b1a1acae8423c1906d6e10cf8226..39889f2388f7a0111bad4c8d41207a5c26444641  
100644
--- a/lily/include/staff-symbol-referencer.hh
+++ b/lily/include/staff-symbol-referencer.hh
@@ -40,6 +40,7 @@ public:
      typeface. ie. leading is vertical space.
   */
   static Real line_thickness (Grob *);
+  static SCM color (Grob *);
   static Real staff_space (Grob *);
   static Grob *get_staff_symbol (Grob *);
   static bool on_line (Grob *, int);
Index: lily/staff-symbol-referencer.cc
diff --git a/lily/staff-symbol-referencer.cc  
b/lily/staff-symbol-referencer.cc
index  
2939e0c0614fdb035fe5a62409c4708f7bbf03ee..fcf7c3b76a900ce0bbd33fd4e08da8f3c1fcca6c  
100644
--- a/lily/staff-symbol-referencer.cc
+++ b/lily/staff-symbol-referencer.cc
@@ -63,6 +63,15 @@ Staff_symbol_referencer::staff_space (Grob *me)
   return 1.0;
 }

+SCM
+Staff_symbol_referencer::color (Grob *me)
+{
+  Grob *st = get_staff_symbol (me);
+  if (st)
+    return st->get_property ("color");
+  return ly_symbol2scm ("black");
+}
+
 Real
 Staff_symbol_referencer::line_thickness (Grob *me)
 {