lily/simple-spacer.cc

   1 /*
   2   simple-spacer.cc -- implement Simple_spacer
   3
   4   source file of the GNU LilyPond music typesetter
   5
   6   (c) 1999--2001 Han-Wen Nienhuys <hanwen@cs.uu.nl>
   7
   8   TODO:
   9   - add support for different stretch/shrink constants?
  10
  11 */
  12
  13 #include <math.h>
  14 #include <libc-extension.hh>
  15
  16 #include "simple-spacer.hh"
  17 #include "paper-column.hh"
  18 #include "spring.hh"
  19 #include "rod.hh"
  20 #include "warn.hh"
  21 #include "column-x-positions.hh"
  22 #include "spaceable-element.hh"
  23 #include "dimensions.hh"
  24
  25 Simple_spacer::Simple_spacer ()
  26 {
  27   force_f_ = 0.;
  28   indent_f_ =0.0;
  29   default_space_f_ = 20 PT;
  30 }
  31
  32 void
  33 Simple_spacer::add_rod (int l, int r, Real dist)
  34 {
  35   if (isinf (dist) || isnan (dist))
  36     {
  37       programming_error ("Weird minimum distance. Ignoring");
  38       return;
  39     }
  40
  41
  42   Real c = range_stiffness (l,r);
  43   Real d = range_ideal_len (l,r);
  44   Real block_stretch = dist - d;
  45
  46   Real block_force = c * block_stretch;
  47   force_f_ = force_f_ >? block_force;
  48
  49   for (int i=l; i < r; i++)
  50     springs_[i].block_force_f_ = block_force >?
  51       springs_[i].block_force_f_ ;
  52 }
  53
  54 Real
  55 Simple_spacer::range_ideal_len (int l, int r)   const
  56 {
  57   Real d =0.;
  58   for (int i=l; i < r; i++)
  59     d += springs_[i].ideal_f_;
  60   return d;
  61 }
  62
  63 Real
  64 Simple_spacer::range_stiffness (int l, int r) const
  65 {
  66   Real den =0.0;
  67   for (int i=l; i < r; i++)
  68     den += 1 / springs_[i].hooke_f_;
  69
  70   return 1 / den;
  71 }
  72
  73 Real
  74 Simple_spacer::active_blocking_force () const
  75 {
  76   Real bf = - infinity_f;
  77   for (int i=0; i < springs_.size (); i++)
  78     if (springs_[i].active_b_)
  79       {
  80         bf = bf >? springs_[i].block_force_f_;
  81       }
  82   return bf;
  83 }
  84
  85 Real
  86 Simple_spacer::active_springs_stiffness () const
  87 {
  88   Real den = 0.0;
  89   for (int i=0; i < springs_.size (); i++)
  90     if (springs_[i].active_b_)
  91       {
  92         den += 1 / springs_[i].hooke_f_;
  93       }
  94   return 1/den;
  95 }
  96
  97 void
  98 Simple_spacer::set_active_states ()
  99 {
 100   // safe, since
 101   // force is only copied.
 102   for (int i=0 ; i <springs_.size (); i++)
 103     if (springs_[i].block_force_f_ >= force_f_)
 104       springs_[i].active_b_ = false;
 105 }
 106
 107 Real
 108 Simple_spacer::configuration_length () const
 109 {
 110   Real l =0.;
 111   for (int i=0; i < springs_.size (); i++)
 112     l += springs_[i].length (force_f_);
 113
 114   return l;
 115 }
 116
 117 Real
 118 Spring_description::length (Real f) const
 119 {
 120   if (!active_b_)
 121     f = block_force_f_;
 122   return ideal_f_ + f / hooke_f_ ;
 123 }
 124
 125 bool
 126 Simple_spacer::active_b () const
 127 {
 128    for (int i=0; i < springs_.size (); i++)
 129     if (springs_[i].active_b_)
 130       return true;
 131    return false;
 132 }
 133
 134 void
 135 Simple_spacer::my_solve_linelen ()
 136 {
 137   while (active_b ())
 138     {
 139       force_f_ = active_blocking_force ();
 140       Real conf = configuration_length ();
 141
 142       if (conf < line_len_f_)
 143         {
 144           force_f_ += (line_len_f_  - conf) * active_springs_stiffness ();
 145           break;
 146         }
 147       else
 148         set_active_states ();
 149     }
 150 }
 151
 152
 153 void
 154 Simple_spacer::my_solve_natural_len ()
 155 {
 156   while (active_b ())
 157     {
 158       force_f_ = active_blocking_force () >? 0.0;
 159
 160       if (force_f_ < 1e-8) // ugh.,
 161         break;
 162
 163       set_active_states ();
 164     }
 165 }
 166
 167 void
 168 Simple_spacer::add_columns (Link_array<Grob> cols)
 169 {
 170   for (int i=0; i < cols.size () - 1; i++)
 171     {
 172       SCM spring_params = SCM_UNDEFINED;
 173       for (SCM s = Spaceable_grob::get_ideal_distances (cols[i]);
 174            spring_params == SCM_UNDEFINED && gh_pair_p (s);
 175            s = gh_cdr (s))
 176         {
 177           Grob *other = unsmob_grob (gh_caar (s));
 178           if (other != cols[i+1])
 179             continue;
 180
 181           spring_params = gh_cdar (s);
 182         }
 183
 184       Spring_description desc;
 185       if (spring_params != SCM_UNDEFINED)
 186         {
 187           desc.ideal_f_ = gh_scm2double (gh_car (spring_params));
 188           desc.hooke_f_ = gh_scm2double (gh_cdr (spring_params));
 189         }
 190       else
 191         {
 192           programming_error ("No spring between adjacent columns");
 193           desc.hooke_f_ = 1.0;
 194           desc.ideal_f_ = default_space_f_;
 195         }
 196
 197       if (!desc.sane_b ())
 198         {
 199           programming_error ("Insane spring found. Setting to unit spring.");
 200           desc.hooke_f_ = 1.0;
 201           desc.ideal_f_ = 1.0;
 202         }
 203
 204       desc.block_force_f_ = - desc.hooke_f_ * desc.ideal_f_; // block at distance 0
 205       springs_.push (desc);
 206     }
 207
 208   for (int i=0; i < cols.size () - 1; i++)
 209     {
 210       for (SCM s = Spaceable_grob::get_minimum_distances (cols[i]);
 211            gh_pair_p (s); s = gh_cdr (s))
 212         {
 213           Grob * other = unsmob_grob (gh_caar (s));
 214           int oi = cols.find_i (other);
 215           if (oi >= 0)
 216             {
 217               add_rod (i, oi, gh_scm2double (gh_cdar (s)));
 218             }
 219         }
 220     }
 221
 222   /*
 223     TODO: should support natural length on only the last line.
 224    */
 225   if (line_len_f_ < 0)
 226     my_solve_natural_len ();
 227   else
 228     my_solve_linelen ();
 229 }
 230
 231 void
 232 Simple_spacer::solve (Column_x_positions *positions) const
 233 {
 234   positions->force_f_ = force_f_;
 235
 236   positions->config_.push (indent_f_);
 237   for (int i=0; i <springs_.size (); i++)
 238     {
 239       positions->config_.push (positions->config_.top () + springs_[i].length (force_f_));
 240     }
 241
 242   positions->satisfies_constraints_b_ = (line_len_f_ < 0) || active_b ();
 243 }
 244
 245
 246
 247 Spring_description::Spring_description ()
 248 {
 249   ideal_f_ =0.0;
 250   hooke_f_ =0.0;
 251   active_b_ = true;
 252   block_force_f_ = 0.0;
 253 }
 254
 255
 256 bool
 257 Spring_description::sane_b () const
 258 {
 259   return (hooke_f_ > 0) &&  ! isinf (ideal_f_) && !isnan (ideal_f_);
 260 }
 261
 262