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--2008 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   SCM forced_page_count = book_->paper_->c_variable ("page-count");
  43
  44   set_to_ideal_line_configuration (0, end);
  45
  46   Page_spacing_result best;
  47   vsize page_count = robust_scm2int (forced_page_count, 1);
  48   Line_division ideal_line_division = current_configuration (0);
  49   Line_division best_division = ideal_line_division;
  50   vsize min_sys_count = 1;
  51   vsize ideal_sys_count = system_count ();
  52
  53   if (!scm_is_integer (forced_page_count))
  54     {
  55       /* find out the ideal number of pages */
  56       message (_ ("Finding the ideal number of pages..."));
  57
  58       best = space_systems_on_best_pages (0, first_page_num);
  59       page_count = best.systems_per_page_.size ();
  60
  61       ideal_sys_count = best.system_count ();
  62       min_sys_count = ideal_sys_count - best.systems_per_page_.back ();
  63
  64       if (page_count > 1 && best.systems_per_page_[page_count - 2] > 1)
  65         min_sys_count -= best.systems_per_page_[page_count - 2];
  66
  67       min_sys_count = max (min_sys_count, (vsize)1);
  68     }
  69   else
  70     {
  71       /* todo: the following line will spit out programming errors if the
  72          ideal line spacing doesn't fit on PAGE_COUNT pages */
  73       best = space_systems_on_n_pages (0, page_count, first_page_num);
  74       min_sys_count = page_count;
  75     }
  76
  77   if (page_count == 1)
  78     message (_ ("Fitting music on 1 page..."));
  79   else if (scm_is_integer (forced_page_count))
  80     message (_f ("Fitting music on %d pages...", (int)page_count));
  81   else
  82     message (_f ("Fitting music on %d or %d pages...", (int)page_count-1, (int)page_count));
  83
  84   /* try a smaller number of systems than the ideal number for line breaking */
  85   Line_division bound = ideal_line_division;
  86   for (vsize sys_count = ideal_sys_count; --sys_count >= min_sys_count;)
  87     {
  88       Page_spacing_result best_for_this_sys_count;
  89       set_current_breakpoints (0, end, sys_count, Line_division (), bound);
  90
  91       for (vsize i = 0; i < current_configuration_count (); i++)
  92         {
  93           vsize min_p_count = min_page_count (i, first_page_num);
  94           Page_spacing_result cur;
  95
  96           if (min_p_count == page_count || scm_is_integer (forced_page_count))
  97             cur = space_systems_on_n_pages (i, page_count, first_page_num);
  98           else
  99             cur = space_systems_on_n_or_one_more_pages (i, page_count-1, first_page_num);
 100
 101           if (cur.demerits_ < best_for_this_sys_count.demerits_ || isinf (best_for_this_sys_count.demerits_))
 102             {
 103               best_for_this_sys_count = cur;
 104               bound = current_configuration (i);
 105             }
 106         }
 107
 108       if (best_for_this_sys_count.demerits_ < best.demerits_ || isinf (best.demerits_))
 109         {
 110           best = best_for_this_sys_count;
 111           best_division = bound;
 112         }
 113
 114       /* if the pages are stretched on average, stop trying to reduce sys_count */
 115       if (best_for_this_sys_count.page_count () < page_count
 116           && best_for_this_sys_count.average_force () > 0)
 117         break;
 118
 119
 120       if (isinf (best_for_this_sys_count.demerits_))
 121         break;
 122     }
 123
 124   /* try a larger number of systems than the ideal line breaking number. This
 125      is more or less C&P, but the loop bounds make it difficult to try something
 126      like do {...} while (flip(&d) != UP). */
 127   bound = ideal_line_division;
 128   for (vsize sys_count = ideal_sys_count+1; sys_count <= max_sys_count; sys_count++)
 129     {
 130       Real best_demerits_for_this_sys_count = infinity_f;
 131       set_current_breakpoints (0, end, sys_count, bound);
 132
 133       for (vsize i = 0; i < current_configuration_count (); i++)
 134         {
 135           vsize min_p_count = min_page_count (i, first_page_num);
 136           Page_spacing_result cur;
 137
 138           if (min_p_count > page_count)
 139             continue;
 140           else
 141             cur = space_systems_on_n_pages (i, page_count, first_page_num);
 142
 143           if (cur.demerits_ < best.demerits_ || isinf (best.demerits_))
 144             {
 145               best = cur;
 146               best_division = current_configuration (i);
 147             }
 148
 149           if (cur.demerits_ < best_demerits_for_this_sys_count || isinf (best_demerits_for_this_sys_count))
 150             {
 151               best_demerits_for_this_sys_count = cur.demerits_;
 152               bound = current_configuration (i);
 153             }
 154         }
 155       if (isinf (best_demerits_for_this_sys_count))
 156         break;
 157     }
 158
 159   message (_ ("Drawing systems..."));
 160   break_into_pieces (0, end, best_division);
 161   SCM lines = systems ();
 162   return make_pages (best.systems_per_page_, lines);
 163 }
 164