/*
This file is part of LilyPond, the GNU music typesetter.
- Copyright (C) 2007--2011 Joe Neeman <joeneeman@gmail.com>
+ Copyright (C) 2007--2014 Joe Neeman <joeneeman@gmail.com>
LilyPond is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
along with LilyPond. If not, see <http://www.gnu.org/licenses/>.
*/
+/*
+ Springs help chains of objects, such as the notes in a line of music,
+ distribute themselves evenly.
+ Each spring decides the length from the reference point of one object
+ along the line to the reference point of the next, based on a force
+ applied to the entire chain (see Spring::length() for details):
+ length = distance_ + flexibility * force
+
+ distance_ is the ideal separation between reference points
+ inverse_stretch_strength_ is the flexibility when the force is stretching
+ inverse_compress_strength_ is the flexibility when the force is compressing
+ min_distance_ sets a lower limit on length
+
+ Typically, the force applied to a list of objects ranges from about
+ -1 to about 1, though there are no set limits.
+*/
+
#include "spring.hh"
Spring::Spring ()
// Conceptually, this should be +inf, but 0.0 meets the requirements
// of Simple_spacer and creates fewer cases of 0.0*inf to handle.
blocking_force_ = 0.0;
+ else if (inverse_compress_strength_ > 0.0)
+ blocking_force_ = (min_distance_ - distance_) / inverse_compress_strength_;
else
- if (inverse_compress_strength_ > 0.0)
- blocking_force_ = (min_distance_ - distance_) / inverse_compress_strength_;
- else
- blocking_force_ = 0.0;
+ blocking_force_ = 0.0;
}
/* scale a spring, but in a way that doesn't violate min_distance */
void
-Spring::operator*= (Real r)
+Spring::operator *= (Real r)
{
distance_ = max (min_distance_, distance_ * r);
inverse_compress_strength_ = max (0.0, distance_ - min_distance_);
- inverse_stretch_strength_ *= 0.8;
+ inverse_stretch_strength_ *= r;
update_blocking_force ();
}
bool
-Spring::operator> (Spring const &other) const
+Spring::operator > (Spring const &other) const
{
return blocking_force_ > other.blocking_force_;
}
min_distance = max (springs[i].min_distance (), min_distance);
}
- avg_stretch /= springs.size ();
- avg_compress /= springs.size ();
- avg_distance /= springs.size ();
+ avg_stretch /= Real (springs.size ());
+ avg_compress /= Real (springs.size ());
+ avg_distance /= Real (springs.size ());
avg_distance = max (min_distance + 0.3, avg_distance);
Spring ret = Spring (avg_distance, min_distance);
blocking_force_ = -infinity_f;
min_distance_ = length (f);
- distance_ = max (distance_, min_distance_);
update_blocking_force ();
}
Real force = max (f, blocking_force_);
Real inv_k = force < 0.0 ? inverse_compress_strength_ : inverse_stretch_strength_;
- if (isinf(force))
+ if (isinf (force))
{
programming_error ("cruelty to springs");
force = 0.0;