/*
- simple-spacer.cc -- implement Simple_spacer
+ simple-spacer.cc -- implement Simple_spacer
source file of the GNU LilyPond music typesetter
(c) 1999 Han-Wen Nienhuys <hanwen@cs.uu.nl>
+
+ TODO:
+ - add support for different stretch/shrink constants?
+ - Use force as a minimizing function, and use it to discourage mixes of
+ wide and tight lines.
- */
+*/
+
+
+#include "simple-spacer.hh"
+#include "paper-column.hh"
+#include "spring.hh"
+#include "rod.hh"
+#include "warn.hh"
+#include "column-x-positions.hh"
+
+Simple_spacer::Simple_spacer ()
+{
+ force_f_ = 0.;
+}
+
+void
+Simple_spacer::add_rod (int l, int r, Real dist)
+{
+ Real c = range_stiffness (l,r);
+ Real d = range_ideal_len (l,r);
+ Real block_stretch = dist - d;
+
+ Real block_force = c * block_stretch;
+ force_f_ = force_f_ >? block_force;
+
+ for (int i=l; i < r; i++)
+ springs_[i].block_force_f_ = block_force >?
+ springs_[i].block_force_f_ ;
+}
+
+Real
+Simple_spacer::range_ideal_len (int l, int r) const
+{
+ Real d =0.;
+ for (int i=l; i < r; i++)
+ d += springs_[i].ideal_f_;
+ return d;
+}
+
+Real
+Simple_spacer::range_stiffness (int l, int r) const
+{
+ Real den =0.0;
+ for (int i=l; i < r; i++)
+ den += 1 / springs_[i].hooke_f_;
+
+ return 1 / den;
+}
+
+Real
+Simple_spacer::active_blocking_force () const
+{
+ Real bf = - infinity_f;
+ for (int i=0; i < springs_.size (); i++)
+ if (springs_[i].active_b_)
+ {
+ bf = bf >? springs_[i].block_force_f_;
+ }
+ return bf;
+}
+
+Real
+Simple_spacer::active_springs_stiffness () const
+{
+ Real den = 0.0;
+ for (int i=0; i < springs_.size (); i++)
+ if (springs_[i].active_b_)
+ {
+ den += 1 / springs_[i].hooke_f_;
+ }
+ return 1/den;
+}
+
+void
+Simple_spacer::set_active_states ()
+{
+ // safe, since
+ // force is only copied.
+ for (int i=0 ; i <springs_.size (); i++)
+ if (springs_[i].block_force_f_ >= force_f_)
+ springs_[i].active_b_ = false;
+}
+
+Real
+Simple_spacer::configuration_length () const
+{
+ Real l =0.;
+ for (int i=0; i < springs_.size (); i++)
+ l += springs_[i].length (force_f_);
+
+ return l;
+}
+
+Real
+Spring_description::length (Real f) const
+{
+ if (!active_b_)
+ f = block_force_f_;
+ return ideal_f_ + f / hooke_f_ ;
+}
+
+bool
+Simple_spacer::active_b () const
+{
+ for (int i=0; i < springs_.size (); i++)
+ if (springs_[i].active_b_)
+ return true;
+ return false;
+}
+
+void
+Simple_spacer::my_solve_linelen ()
+{
+ while (active_b ())
+ {
+ force_f_ = active_blocking_force ();
+ Real conf = configuration_length ();
+
+ if (conf < line_len_f_)
+ {
+ force_f_ += (line_len_f_ - conf) * active_springs_stiffness ();
+ break;
+ }
+ else
+ set_active_states ();
+ }
+}
+
+
+void
+Simple_spacer::my_solve_natural_len ()
+{
+ while (active_b ())
+ {
+ force_f_ = active_blocking_force () >? 0.0;
+
+ if (force_f_ < 1e-8) // ugh.,
+ break;
+
+ set_active_states ();
+ }
+}
+
+void
+Simple_spacer::add_columns (Link_array<Paper_column> cols)
+{
+ for (int i=0; i < cols.size () - 1; i++)
+ {
+ Paper_column * c = cols [i];
+ Column_spring *to_next = 0;
+ for (int j =0; !to_next && j < c->spring_arr_drul_[RIGHT].size( ); j++)
+ {
+ Column_spring &sp = c->spring_arr_drul_[RIGHT] [j];
+ if (sp.other_l_ != cols[i+1])
+ continue;
+
+ to_next = &sp;
+ }
+
+ Spring_description desc;
+ if (to_next)
+ {
+ desc.hooke_f_ = to_next->strength_f_;
+ desc.ideal_f_ = to_next->distance_f_;
+ }
+ else
+ {
+ desc.hooke_f_ = 1.0;
+ desc.ideal_f_ = default_space_f_;
+ }
+ desc.block_force_f_ = - desc.hooke_f_ * desc.ideal_f_; // block at distance 0
+ springs_.push (desc);
+ }
+
+ for (int i=0; i < cols.size () - 1; i++)
+ {
+ Array<Column_rod> * rods = &cols [i]->minimal_dists_arr_drul_[RIGHT];
+ for (int j =0; j < rods->size( ); j++)
+ {
+ int oi = cols.find_i (rods->elem (j).other_l_ );
+ if (oi >= 0)
+ {
+ add_rod (i, oi, rods->elem (j).distance_f_);
+ }
+ }
+ }
+
+ if (line_len_f_ < 0)
+ my_solve_natural_len ();
+ else
+ my_solve_linelen ();
+}
+
+void
+Simple_spacer::solve (Column_x_positions *positions) const
+{
+ positions->energy_f_ = energy_f (); // abs (force_f_);
+ positions->config_.push (indent_f_);
+ for (int i=0; i <springs_.size (); i++)
+ {
+ positions->config_.push (positions->config_.top () + springs_[i].length (force_f_));
+ }
+
+ positions->satisfies_constraints_b_ = active_b ();
+}
+
+void
+Simple_spacer::lower_bound_solution (Column_x_positions * posns) const
+{
+ solve (posns);
+}
+
+
+Spring_description::Spring_description( )
+{
+ ideal_f_ =0.0;
+ hooke_f_ =0.0;
+ active_b_ = true;
+ block_force_f_ = 0.0;
+}
+
+Real
+Spring_description::energy_f (Real force) const
+{
+ Real stretch = (force >? block_force_f_) / hooke_f_;
+ Real e = 0.5 * stretch * stretch * hooke_f_;
+
+ /*
+ be harder to compress.
+ */
+ if (stretch < 0)
+ e *= 4;
+
+ return e;
+}
+Real
+Simple_spacer::energy_f () const
+{
+ Real e =0.;
+ for (int i=0; i <springs_.size (); i++)
+ e += springs_[i].energy_f (force_f_);
+
+ return e;
+}
projects / lilypond.git / blobdiff