X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fspring.cc;h=cd63afa6702bc4b4ba9c59ce6ecca61512a920e8;hb=5b4b0d6e9a197e8f9eb085b7c2ad78b8be3e5cfc;hp=ae5f33da74af49aa03598182b5bc9ad6ae1bcf15;hpb=d7416352b825c3e9b4858e1ddcf14f0c00e26d89;p=lilypond.git

diff --git a/lily/spring.cc b/lily/spring.cc
index ae5f33da74..cd63afa670 100644
--- a/lily/spring.cc
+++ b/lily/spring.cc
@@ -1,42 +1,167 @@
-/*   
-  spring.cc --  implement Spring
-  
+/*
+  spring.cc -- declare Spring
+
   source file of the GNU LilyPond music typesetter
-  
-  (c) 1999--2000 Han-Wen Nienhuys <hanwen@cs.uu.nl>
-  
- */
+
+  (c) 2007--2008 Joe Neeman <joeneeman@gmail.com>
+*/
 
 #include "spring.hh"
-#include "debug.hh"
-#include "item.hh"
-#include "paper-column.hh"
 
 Spring::Spring ()
 {
-  item_l_drul_[LEFT]  =item_l_drul_[RIGHT] =0;
-  distance_f_ =0.;
-  strength_f_ =1.0;
+  distance_ = 1.0;
+  min_distance_ = 1.0;
+  inverse_stretch_strength_ = 1.0;
+  inverse_compress_strength_ = 1.0;
+
+  update_blocking_force ();
+}
+
+Spring::Spring (Real dist, Real min_dist)
+{
+  distance_ = 1.0;
+  min_distance_ = 1.0;
+
+  set_distance (dist);
+  set_min_distance (min_dist);
+  set_default_strength ();
+  update_blocking_force ();
+}
+
+void
+Spring::update_blocking_force ()
+{
+  if (distance_ == min_distance_)
+    blocking_force_ = 0.0;
+  else
+    blocking_force_ = (min_distance_ - distance_) / inverse_compress_strength_;
 }
 
+/* scale a spring, but in a way that doesn't violate min_distance */
 void
-Spring::add_to_cols ()
+Spring::operator*= (Real r)
 {
-  item_l_drul_[LEFT]->column_l ()->add_spring (item_l_drul_[RIGHT]->column_l (), distance_f_, strength_f_);
+  distance_ = max (min_distance_, distance_ * r);
+  inverse_compress_strength_ = distance_ - min_distance_;
+  inverse_stretch_strength_ *= 0.8;
 }
 
+bool
+Spring::operator> (Spring const &other) const
+{
+  return blocking_force_ > other.blocking_force_;
+}
 
-Column_spring::Column_spring ()
+/* merge springs, basically by averaging them, but leave a little headroom
+   above the largest minimum distance so that things don't get too cramped */
+Spring
+merge_springs (vector<Spring> const &springs)
 {
-  other_l_ = 0;
-  distance_f_ =0;
-  strength_f_ =1.0;
+  Real avg_distance = 0;
+  Real min_distance = 0;
+  Real avg_stretch = 0;
+  Real avg_compress = 0;
+
+  for (vsize i = 0; i < springs.size (); i++)
+    {
+      avg_distance += springs[i].distance ();
+      avg_stretch += springs[i].inverse_stretch_strength ();
+      avg_compress += 1 / springs[i].inverse_compress_strength ();
+      min_distance = max (springs[i].min_distance (), min_distance);
+    }
+
+  avg_stretch /= springs.size ();
+  avg_compress /= springs.size ();
+  avg_distance /= springs.size ();
+  avg_distance = max (min_distance + 0.3, avg_distance);
+
+  Spring ret = Spring (avg_distance, min_distance);
+  ret.set_inverse_stretch_strength (avg_stretch);
+  ret.set_inverse_compress_strength (1 / avg_compress);
+
+  return ret;
 }
 
+void
+Spring::set_distance (Real d)
+{
+  if (d < 0 || isinf (d) || isnan (d))
+    programming_error ("insane spring distance requested, ignoring it");
+  else
+    {
+      min_distance_ = min (min_distance_, d);
+      distance_ = d;
+      update_blocking_force ();
+    }
+}
 
-int
-Column_spring::compare (Column_spring const & r1, Column_spring const &r2)
+void
+Spring::set_min_distance (Real d)
 {
-  return r1.other_l_->rank_i() - r2.other_l_->rank_i();
+  if (d < 0 || isinf (d) || isnan (d))
+    programming_error ("insane spring min_distance requested, ignoring it");
+  else
+    {
+      min_distance_ = d;
+      distance_ = max (distance_, min_distance_);
+      update_blocking_force ();
+    }
 }
 
+void
+Spring::set_inverse_stretch_strength (Real f)
+{
+  if (isinf (f) || isnan (f) || f < 0)
+    programming_error ("insane spring constant");
+  else
+    inverse_stretch_strength_ = f;
+}
+
+void
+Spring::set_inverse_compress_strength (Real f)
+{
+  if (isinf (f) || isnan (f) || f < 0)
+    programming_error ("insane spring constant");
+  else
+    inverse_compress_strength_ = f;
+
+  update_blocking_force ();
+}
+
+void
+Spring::set_blocking_force (Real f)
+{
+  if (isinf (f) || isnan (f))
+    {
+      programming_error ("insane blocking force");
+      return;
+    }
+
+  blocking_force_ = -infinity_f;
+  min_distance_ = length (f);
+  distance_ = max (distance_, min_distance_);
+  update_blocking_force ();
+}
+
+void
+Spring::set_default_strength ()
+{
+  inverse_compress_strength_ = distance_ - min_distance_;
+  inverse_stretch_strength_ = distance_ - min_distance_;
+}
+
+Real
+Spring::length (Real f) const
+{
+  Real force = max (f, blocking_force_);
+  Real inv_k = force < 0.0 ? inverse_compress_strength_ : inverse_stretch_strength_;
+
+  if (isinf (force))
+    {
+      programming_error ("cruelty to springs");
+      force = 0.0;
+    }
+
+  return distance_ + force * inv_k;
+}