release: 0.0.73pre

[lilypond.git] / lily / beam.cc

diff --git a/lily/beam.cc b/lily/beam.cc
index 990299823511f19eec471a63ea9542afbf33a899..d4f741d78893dd82a1451ed98d0e6b8b811de791 100644 (file)
--- a/lily/beam.cc
+++ b/lily/beam.cc
@@ -1,14 +1,13 @@
 /*
   beam.cc -- implement Beam
 
-  source file of the GNU GNU LilyPond music typesetter
+  source file of the GNU LilyPond music typesetter
 
   (c) 1997 Han-Wen Nienhuys <hanwen@stack.nl>
 
   TODO
 
-  Less hairy code. Better slope calculations.
-  knee: ([\stem 1; c8 \stem -1; c8]
+  Less hairy code.  knee: ([\stem 1; c8 \stem -1; c8]
   
 */
 
@@ -69,7 +68,6 @@ Stem_info::Stem_info(Stem const *s)
     // huh? why do i need the / 2
 //    Real interbeam_f = s->paper()->interbeam_f();
     Real interbeam_f = s->paper()->interbeam_f() / 2;
-    Real interline_f = s->paper()->interline_f();
            
     /* well eh, huh?
     idealy_f_  = dir_i_ * s->stem_start_f() + beams_i_ * interbeam_f; 
@@ -169,14 +167,23 @@ Beam::solve_slope()
        Stem_info info(i);
        sinfo.push(info);
     }
-    Real leftx = sinfo[0].x;
-    Least_squares l;
-    for (int i=0; i < sinfo.size(); i++) {
-       sinfo[i].x -= leftx;
-       l.input.push(Offset(sinfo[i].x, sinfo[i].idealy_f_));
-    }
+    if (! sinfo.size() )
+       slope = left_pos = 0;
+    else if (sinfo.size() == 1) {
+       slope = 0;
+       left_pos = sinfo[0].idealy_f_;
+    } else {
+       
+       Real leftx = sinfo[0].x;
+       Least_squares l;
+       for (int i=0; i < sinfo.size(); i++) {
+           sinfo[i].x -= leftx;
+           l.input.push(Offset(sinfo[i].x, sinfo[i].idealy_f_));
+       }
 
-    l.minimise(slope, left_pos);
+       l.minimise(slope, left_pos);
+    }
+    
     Real dy = 0.0;
     for (int i=0; i < sinfo.size(); i++) {
        Real y = sinfo[i].x * slope + left_pos;
@@ -189,7 +196,12 @@ Beam::solve_slope()
     left_pos *= dir_i_;    
 
     slope *= dir_i_;
-    slope = 0.6 * tanh(slope);  // damping
+
+    /*
+      This neat trick is by Werner Lemberg, damped = tanh(slope) corresponds
+      with some tables in [Wanske]
+     */
+    slope = 0.6 * tanh(slope);  
 
                                // ugh
     Real sl = slope*paper()->internote_f();