lily/optimal-page-breaking.cc

   1 /*
   2   optimal-page-breaking.cc -- implement a page-breaker that
   3   will break pages in such a way that both horizontal and
   4   vertical spacing will be acceptable
   5
   6   source file of the GNU LilyPond music typesetter
   7
   8   (c) 2006--2007 Joe Neeman <joeneeman@gmail.com>
   9 */
  10
  11 #include "international.hh"
  12 #include "optimal-page-breaking.hh"
  13 #include "output-def.hh"
  14 #include "page-spacing.hh"
  15 #include "paper-book.hh"
  16 #include "paper-score.hh"
  17 #include "prob.hh"
  18 #include "system.hh"
  19
  20 static bool
  21 is_break (Grob *g)
  22 {
  23   (void) g; /* shutup warning */
  24   return false;
  25 }
  26
  27 Optimal_page_breaking::Optimal_page_breaking (Paper_book *pb)
  28   : Page_breaking (pb, is_break)
  29 {
  30 }
  31
  32 Optimal_page_breaking::~Optimal_page_breaking ()
  33 {
  34 }
  35
  36 SCM
  37 Optimal_page_breaking::solve ()
  38 {
  39   vsize end = last_break_position ();
  40   vsize max_sys_count = max_system_count (0, end);
  41   vsize first_page_num = robust_scm2int (book_->paper_->c_variable ("first-page-number"), 1);
  42
  43   /* find out the ideal number of pages */
  44   message (_ ("Finding the ideal number of pages..."));
  45   set_to_ideal_line_configuration (0, end);
  46
  47   Page_spacing_result best = space_systems_on_best_pages (0, first_page_num);
  48   vsize page_count = best.systems_per_page_.size ();
  49   Line_division ideal_line_division = current_configuration (0);
  50   Line_division best_division = ideal_line_division;
  51
  52   vsize ideal_sys_count = best.system_count ();
  53   vsize min_sys_count = ideal_sys_count - best.systems_per_page_.back ();
  54
  55   if (page_count > 1)
  56     min_sys_count -= best.systems_per_page_[page_count - 2];
  57
  58   if (page_count == 1)
  59     message (_ ("Fitting music on 1 page..."));
  60   else
  61     message (_f ("Fitting music on %d or %d pages...", (int)page_count-1, (int)page_count));
  62
  63   /* try a smaller number of systems than the ideal number for line breaking */
  64   Line_division bound = ideal_line_division;
  65   for (vsize sys_count = ideal_sys_count; --sys_count >= min_sys_count;)
  66     {
  67       Page_spacing_result best_for_this_sys_count;
  68       set_current_breakpoints (0, end, sys_count, Line_division (), bound);
  69
  70       for (vsize i = 0; i < current_configuration_count (); i++)
  71         {
  72           vsize min_p_count = min_page_count (i, first_page_num);
  73           Page_spacing_result cur;
  74
  75           if (min_p_count > page_count)
  76             continue;
  77           else if (min_p_count == page_count)
  78             cur = space_systems_on_n_pages (i, page_count, first_page_num);
  79           else
  80             cur = space_systems_on_n_or_one_more_pages (i, page_count-1, first_page_num);
  81
  82           if (cur.demerits_ < best_for_this_sys_count.demerits_ || isinf (best_for_this_sys_count.demerits_))
  83             {
  84               best_for_this_sys_count = cur;
  85               bound = current_configuration (i);
  86             }
  87         }
  88
  89       if (best_for_this_sys_count.demerits_ < best.demerits_ || isinf (best.demerits_))
  90         {
  91           best = best_for_this_sys_count;
  92           best_division = bound;
  93         }
  94
  95       /* if the pages are stretched on average, stop trying to reduce sys_count */
  96       if (best_for_this_sys_count.page_count () < page_count
  97           && best_for_this_sys_count.average_force () > 0)
  98         break;
  99
 100
 101       if (isinf (best_for_this_sys_count.demerits_))
 102         break;
 103     }
 104
 105   /* try a larger number of systems than the ideal line breaking number. This
 106      is more or less C&P, but the loop bounds make it difficult to try something
 107      like do {...} while (flip(&d) != UP). */
 108   bound = ideal_line_division;
 109   for (vsize sys_count = ideal_sys_count+1; sys_count <= max_sys_count; sys_count++)
 110     {
 111       Real best_demerits_for_this_sys_count = infinity_f;
 112       set_current_breakpoints (0, end, sys_count, bound);
 113
 114       for (vsize i = 0; i < current_configuration_count (); i++)
 115         {
 116           vsize min_p_count = min_page_count (i, first_page_num);
 117           Page_spacing_result cur;
 118
 119           if (min_p_count > page_count)
 120             continue;
 121           else
 122             cur = space_systems_on_n_pages (i, page_count, first_page_num);
 123
 124           if (cur.demerits_ < best.demerits_ || isinf (best.demerits_))
 125             {
 126               best = cur;
 127               best_division = current_configuration (i);
 128             }
 129
 130           if (cur.demerits_ < best_demerits_for_this_sys_count || isinf (best_demerits_for_this_sys_count))
 131             {
 132               best_demerits_for_this_sys_count = cur.demerits_;
 133               bound = current_configuration (i);
 134             }
 135         }
 136       if (isinf (best_demerits_for_this_sys_count))
 137         break;
 138     }
 139
 140   message ("Drawing systems...");
 141   break_into_pieces (0, end, best_division);
 142   SCM lines = systems ();
 143   return make_pages (best.systems_per_page_, lines);
 144 }
 145