make slur behaviour symmetrical for above/below staff

the original code probably missed an fabs and
certainly didn't work for non-standard staves

diff --git a/lily/slur-scoring.cc b/lily/slur-scoring.cc
index d8b713265c7e79e60300bf25c8870ff5616b8a9f..e1025fa545c56c1c20ee0a476355b778229cf336 100644 (file)
--- a/lily/slur-scoring.cc
+++ b/lily/slur-scoring.cc
@@ -595,8 +595,7 @@ Slur_score_state::move_away_from_staffline (Real y,
       * 2.0 / staff_space_;
 
   if (fabs (pos - my_round (pos)) < 0.2
-      && Staff_symbol_referencer::on_line (on_staff, (int) rint (pos))
-      && Staff_symbol_referencer::line_count (on_staff) - 1 >= rint (pos))
+      && Staff_symbol_referencer::on_staff_line (on_staff, (int) rint (pos)))
     y += 1.5 * staff_space_ * dir_ / 10;
 
   return y;