X-Git-Url: https://git.donarmstrong.com/?a=blobdiff_plain;f=lily%2Fspring.cc;h=1f250546db354d31f41a7cfb344a011281af7524;hb=7c83ac2d86066ca8f41260d37e792e166ad5dbb6;hp=8b137891791fe96927ad78e64b0aad7bded08bdc;hpb=ce521e79fd7669b45c8c1132e4b5693a03b5d90a;p=lilypond.git

diff --git a/lily/spring.cc b/lily/spring.cc
index 8b13789179..1f250546db 100644
--- a/lily/spring.cc
+++ b/lily/spring.cc
@@ -1 +1,167 @@
+/*
+  spring.cc -- declare Spring
 
+  source file of the GNU LilyPond music typesetter
+
+  (c) 2007 Joe Neeman <joeneeman@gmail.com>
+*/
+
+#include "spring.hh"
+
+Spring::Spring ()
+{
+  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::operator*= (Real r)
+{
+  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_;
+}
+
+/* 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)
+{
+  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 ();
+    }
+}
+
+void
+Spring::set_min_distance (Real d)
+{
+  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;
+}