]> git.donarmstrong.com Git - lilypond.git/blobdiff - lily/page-breaking.cc
Fix 1112.
[lilypond.git] / lily / page-breaking.cc
index b6951925ad7ce7cc518b6b68f90efc225201eb78..aeeb7bb1b7eb555db4f37ea162524178d72c8050 100644 (file)
@@ -1,10 +1,76 @@
 /*
-  page-breaking.cc -- implement a superclass and utility
-  functions shared by various page-breaking algorithms
+  This file is part of LilyPond, the GNU music typesetter.
 
-  source file of the GNU LilyPond music typesetter
+  Copyright (C) 2006--2010 Joe Neeman <joeneeman@gmail.com>
 
-  (c) 2006--2007 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
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  LilyPond is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with LilyPond.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/*
+  This is a utility class for page-breaking algorithms. There are some complex
+  parts of this class, some of which are useful to understand if you intend
+  to write a page breaking algorithm (ie. a subclass of Page_breaking). Most
+  of these complexities were introduced in order to break the problem of
+  page-breaking into simpler subproblems and to hide some of the bookkeeping
+  complexities of page breaking from the page breaking algorithms.
+
+  COMPRESSED LINES
+  There are several functions that actually distribute systems across pages
+  (for example, the space_systems_XXX and pack_systems_XXX functions). If
+  each of these functions had to handle \noPageBreak, it would be a mess.
+  Therefore, we handle \noPageBreak by "compressing" the list of systems
+  before doing any layout: we concatenate any two systems separated by a
+  \noPageBreak into a single system. The page-breaking functions can do their
+  magic without encountering a \noPageBreak; we then "uncompress" the systems
+  at the end. We almost always work with cached_line_details_, which are
+  "compressed."
+
+  CHUNKS
+  The basic operation of a page breaking algorithm is to repeatedly request
+  some systems from the line-breaker and place those systems on some pages.
+  With each repetition, the page breaking algorithm asks the line-breaker for
+  some systems that it thinks will help it achieve a better layout. The
+  Page_breaking class provides functionality to facilitate this in the case
+  that the page breaking algorithm only cares about the number of systems.
+
+  Even if a page breaking algorithm only cares number of systems, there may
+  be many ways to satisfy its request. For example, in a piece with 2 scores
+  and a request for 10 systems, we could return 5 systems from each score or
+  4 from the first and 6 from the second. Even within a score, we might
+  want to try several different line breaking configurations with a fixed
+  system count; if there is a forced \pageBreak, for example, we might wish
+  to tweak the number of systems on both sides of the \pageBreak independently.
+
+  The Page_breaking class takes care of finding these configurations. It
+  divides the piece into "chunks" and sets up the line-breaker in such a way
+  that the number of systems in each chunk can be modified independently.
+  Chunks never cross score boundaries; each title and markup is its own chunk.
+  When a page breaking algorithm requests a number of systems, the Page_breaker
+  stores an array of potential configurations, which the page breaking
+  algorithm can iterate over using current_configuration(vsize).
+
+  LINE_DIVISION
+  A Line_division is simply a way of storing the exact way in which the
+  total number of systems is distributed among chunks. Note that a
+  Line_division may not (in fact, usually will not) describe all of the chunks
+  in the entire book. Rather, it will describe the subset of chunks that lie
+  between some fixed starting and ending point. This subset of chunks changes
+  whenever a page breaking algorithm asks to consider a different pair of
+  starting and ending breakpoints. In particular, a Line_division should be
+  discarded after a call to set_current_breakpoints, since that Line_division
+  refers to a subset of chunks which might be different from the current
+  subset of chunks under consideration.
 */
 
 #include "page-breaking.hh"
@@ -12,6 +78,7 @@
 #include "international.hh"
 #include "item.hh"
 #include "output-def.hh"
+#include "page-layout-problem.hh"
 #include "page-spacing.hh"
 #include "paper-book.hh"
 #include "paper-score.hh"
@@ -32,16 +99,28 @@ compress_lines (const vector<Line_details> &orig)
        {
          Line_details const &old = ret.back ();
          Line_details compressed = orig[i];
-         compressed.extent_[DOWN] = old.extent_[DOWN];
-         compressed.extent_[UP] = old.extent_[UP] + orig[i].extent_.length () + old.padding_;
+         /*
+           We must account for the padding between the lines that we are compressing.
+           The padding values come from "old," which is the upper system here. Note
+           the meaning of tight-spacing: if a system has tight-spacing, then the padding
+           _before_ it is ignored.
+         */
+         Real padding = 0;
+         if (!orig[i].tight_spacing_)
+           padding = orig[i].title_ ? old.title_padding_ : old.padding_;
+
+         compressed.shape_ = old.shape_.piggyback (orig[i].shape_, padding);
+         compressed.first_refpoint_offset_ += compressed.shape_.rest_[UP] - old.shape_.rest_[UP];
          compressed.space_ += old.space_;
          compressed.inverse_hooke_ += old.inverse_hooke_;
 
-         /* we don't need the force_ field for the vertical spacing,
-            so we use force_ = n to signal that the line was compressed,
-            reducing the number of lines by n (and force_ = 0 otherwise).
-            This makes uncompression much easier. */
-         compressed.force_ = old.force_ + 1;
+         compressed.compressed_lines_count_ = old.compressed_lines_count_ + 1;
+         compressed.compressed_nontitle_lines_count_ =
+           old.compressed_nontitle_lines_count_ + (compressed.title_ ? 0 : 1);
+
+         // compressed.title_ is true if and only if the first of its
+         // compressed lines was a title.
+         compressed.title_ = old.title_;
          ret.back () = compressed;
        }
       else
@@ -67,7 +146,7 @@ uncompress_solution (vector<vsize> const &systems_per_page,
     {
       int compressed_count = 0;
       for (vsize j = start_sys; j < start_sys + systems_per_page[i]; j++)
-       compressed_count += (int)compressed[j].force_;
+       compressed_count += compressed[j].compressed_lines_count_ - 1;
 
       ret.push_back (systems_per_page[i] + compressed_count);
       start_sys += systems_per_page[i];
@@ -97,8 +176,25 @@ Page_breaking::next_system (Break_position const &break_pos) const
 Page_breaking::Page_breaking (Paper_book *pb, Break_predicate is_break)
 {
   book_ = pb;
+  system_count_ = 0;
   ragged_ = to_boolean (pb->paper_->c_variable ("ragged-bottom"));
   ragged_last_ = to_boolean (pb->paper_->c_variable ("ragged-last-bottom"));
+  systems_per_page_ = max (0, robust_scm2int (pb->paper_->c_variable ("systems-per-page"), 0));
+  max_systems_per_page_ = max (0, robust_scm2int (pb->paper_->c_variable ("max-systems-per-page"), 0));
+  min_systems_per_page_ = max (0, robust_scm2int (pb->paper_->c_variable ("min-systems-per-page"), 0));
+  orphan_penalty_ = robust_scm2int (pb->paper_->c_variable ("orphan-penalty"), 100000);
+
+  if (systems_per_page_ && (max_systems_per_page_ || min_systems_per_page_))
+    {
+      warning (_f ("ignoring min-systems-per-page and max-systems-per-page because systems-per-page was set"));
+      min_systems_per_page_ = max_systems_per_page_ = 0;
+    }
+  if (max_systems_per_page_ && min_systems_per_page_ > max_systems_per_page_)
+    {
+      warning (_f ("min-systems-per-page is larger than max-systems-per-page, ignoring both values"));
+      min_systems_per_page_ = max_systems_per_page_ = 0;
+    }
+
   create_system_list ();
   find_chunks_and_breaks (is_break);
 }
@@ -119,6 +215,64 @@ Page_breaking::ragged_last () const
   return ragged_last_;
 }
 
+int
+Page_breaking::systems_per_page () const
+{
+  return systems_per_page_;
+}
+
+int
+Page_breaking::max_systems_per_page () const
+{
+  return max_systems_per_page_;
+}
+
+int
+Page_breaking::min_systems_per_page () const
+{
+  return min_systems_per_page_;
+}
+
+vsize
+Page_breaking::system_count () const
+{
+  return system_count_;
+}
+
+bool
+Page_breaking::too_many_lines (int line_count) const
+{
+  return max_systems_per_page () > 0 && line_count > max_systems_per_page ();
+}
+
+bool
+Page_breaking::too_few_lines (int line_count) const
+{
+  return line_count < min_systems_per_page ();
+}
+
+Real
+Page_breaking::line_count_penalty (int line_count) const
+{
+  if (too_many_lines (line_count))
+    return (line_count - max_systems_per_page ()) * TERRIBLE_SPACING_PENALTY;
+  if (too_few_lines (line_count))
+    return (min_systems_per_page () - line_count) * TERRIBLE_SPACING_PENALTY;
+
+  return 0;
+}
+
+int
+Page_breaking::line_count_status (int line_count) const
+{
+  if (too_many_lines (line_count))
+    return SYSTEM_COUNT_TOO_MANY;
+  if (too_few_lines (line_count))
+    return SYSTEM_COUNT_TOO_FEW;
+
+  return SYSTEM_COUNT_OK;
+}
+
 /* translate indices into breaks_ into start-end parameters for the line breaker */
 void
 Page_breaking::line_breaker_args (vsize sys,
@@ -194,23 +348,33 @@ Page_breaking::systems ()
   return scm_append (scm_reverse (ret));
 }
 
+SCM
+Page_breaking::make_page (int page_num, bool last) const
+{
+  bool last_part = ly_scm2bool (book_->paper_->c_variable ("is-last-bookpart"));
+  SCM mod = scm_c_resolve_module ("scm page");
+  SCM make_page_scm = scm_c_module_lookup (mod, "make-page");
+
+  make_page_scm = scm_variable_ref (make_page_scm);
+
+  return scm_apply_0 (make_page_scm,
+                     scm_list_n (book_->self_scm (),
+                                 ly_symbol2scm ("page-number"), scm_from_int (page_num),
+                                 ly_symbol2scm ("is-last-bookpart"), scm_from_bool (last_part),
+                                 ly_symbol2scm ("is-bookpart-last-page"), scm_from_bool (last),
+                                 SCM_UNDEFINED));
+}
+
 Real
 Page_breaking::page_height (int page_num, bool last) const
 {
   SCM mod = scm_c_resolve_module ("scm page");
+  SCM page = make_page (page_num, last);
   SCM calc_height = scm_c_module_lookup (mod, "calc-printable-height");
-  SCM make_page = scm_c_module_lookup (mod, "make-page");
-
   calc_height = scm_variable_ref (calc_height);
-  make_page = scm_variable_ref (make_page);
 
-  SCM page = scm_apply_0 (make_page, scm_list_n (
-                  book_->self_scm (),
-                  ly_symbol2scm ("page-number"), scm_from_int (page_num),
-                  ly_symbol2scm ("is-last"), scm_from_bool (last),
-                  SCM_UNDEFINED));
   SCM height = scm_apply_1 (calc_height, page, SCM_EOL);
-  return scm_to_double (height) - scm_to_double (book_->paper_->c_variable ("page-top-space"));
+  return scm_to_double (height);
 }
 
 SCM
@@ -226,35 +390,86 @@ Page_breaking::breakpoint_property (vsize breakpoint, char const *str)
 }
 
 SCM
-Page_breaking::make_pages (vector<vsize> lines_per_page, SCM systems)
+Page_breaking::get_page_configuration (SCM systems, int page_num, bool ragged, bool last)
 {
-  SCM layout_module = scm_c_resolve_module ("scm layout-page-layout");
-  SCM page_module = scm_c_resolve_module ("scm page");
+  SCM dummy_page = make_page (page_num, last);
+  Page_layout_problem layout (book_, dummy_page, systems);
+  return scm_is_pair (systems) ? layout.solution (ragged) : SCM_EOL;
+}
 
-  SCM make_page = scm_c_module_lookup (layout_module, "stretch-and-draw-page");
+SCM
+Page_breaking::draw_page (SCM systems, SCM configuration, int page_num, bool last)
+{
+  // Create a stencil for each system.
+  SCM paper_systems = SCM_EOL;
+  for (SCM s = scm_reverse (systems); scm_is_pair (s); s = scm_cdr (s))
+    {
+      SCM paper_system = scm_car (s);
+      if (Grob *g = unsmob_grob (scm_car (s)))
+       {
+         System *sys = dynamic_cast<System*> (g);
+         paper_system = sys->get_paper_system ();
+       }
+
+      paper_systems = scm_cons (paper_system, paper_systems);
+    }
+
+  // Create the page and draw it.
+  SCM page = make_page (page_num, last);
+  SCM page_module = scm_c_resolve_module ("scm page");
   SCM page_stencil = scm_c_module_lookup (page_module, "page-stencil");
-  make_page = scm_variable_ref (make_page);
   page_stencil = scm_variable_ref (page_stencil);
 
-  SCM book = book_->self_scm ();
+  Prob *p = unsmob_prob (page);
+  p->set_property ("lines", paper_systems);
+  p->set_property ("configuration", configuration);
+  scm_apply_1 (page_stencil, page, SCM_EOL);
+
+  return page;
+}
+
+SCM
+Page_breaking::make_pages (vector<vsize> lines_per_page, SCM systems)
+{
   int first_page_number
     = robust_scm2int (book_->paper_->c_variable ("first-page-number"), 1);
   SCM ret = SCM_EOL;
-  SCM label_page_table = SCM_EOL;
+  SCM label_page_table = book_->top_paper ()->c_variable ("label-page-table");
+  if (label_page_table == SCM_UNDEFINED)
+    label_page_table = SCM_EOL;
+
+  // Build a list of (systems . configuration) pairs. Note that we lay out
+  // the staves and find the configurations before drawing anything. Some
+  // grobs (like tuplet brackets) look at their neighbours while drawing
+  // themselves. If this happens before the neighbouring staves have
+  // been laid out, bad side-effects could happen (in particular,
+  // Align_interface::align_to_ideal_distances might be called).
+  SCM systems_and_configs = SCM_EOL;
 
   for (vsize i = 0; i < lines_per_page.size (); i++)
     {
-      SCM page_num = scm_from_int (i + first_page_number);
-      SCM last = scm_from_bool (i == lines_per_page.size () - 1);
-      SCM rag = scm_from_bool (ragged () || (to_boolean (last)
-                                            && ragged_last ()));
+      int page_num = i + first_page_number;
+      bool bookpart_last_page = (i == lines_per_page.size () - 1);
+      bool rag = ragged () || (bookpart_last_page && ragged_last ());
       SCM line_count = scm_from_int (lines_per_page[i]);
       SCM lines = scm_list_head (systems, line_count);
-      SCM page = scm_apply_0 (make_page,
-                             scm_list_n (book, lines, page_num,
-                                         rag, last, SCM_UNDEFINED));
+      SCM config = get_page_configuration (lines, page_num, rag, bookpart_last_page);
+
+      systems_and_configs = scm_cons (scm_cons (lines, config), systems_and_configs);
+      systems = scm_list_tail (systems, line_count);
+    }
+
+  // Now it's safe to make the pages.
+  int page_num = first_page_number + lines_per_page.size () - 1;
+  for (SCM s = systems_and_configs; scm_is_pair (s); s = scm_cdr (s))
+    {
+      SCM lines = scm_caar (s);
+      SCM config = scm_cdar (s);
+      bool bookpart_last_page = (s == systems_and_configs);
+      SCM page = draw_page (lines, config, page_num, bookpart_last_page);
 
       /* collect labels */
+      SCM page_num_scm = scm_from_int (page_num);
       for (SCM l = lines ; scm_is_pair (l)  ; l = scm_cdr (l))
        {
          SCM labels = SCM_EOL;
@@ -267,16 +482,14 @@ Page_breaking::make_pages (vector<vsize> lines_per_page, SCM systems)
            labels = prob->get_property ("labels");
 
          for (SCM lbls = labels ; scm_is_pair (lbls) ; lbls = scm_cdr (lbls))
-           label_page_table = scm_cons (scm_cons (scm_car (lbls), page_num),
+           label_page_table = scm_cons (scm_cons (scm_car (lbls), page_num_scm),
                                         label_page_table);
        }
 
-      scm_apply_1 (page_stencil, page, SCM_EOL);
       ret = scm_cons (page, ret);
-      systems = scm_list_tail (systems, line_count);
+      --page_num;
     }
-  book_->paper_->set_variable (ly_symbol2scm ("label-page-table"), label_page_table);
-  ret = scm_reverse (ret);
+  book_->top_paper ()->set_variable (ly_symbol2scm ("label-page-table"), label_page_table);
   return ret;
 }
 
@@ -296,14 +509,7 @@ Page_breaking::create_system_list ()
     {
       if (Paper_score *ps = dynamic_cast<Paper_score*> (unsmob_music_output (scm_car (s))))
        {
-         SCM system_count = ps->layout ()->c_variable ("system-count");
-
-         if (scm_is_number (system_count))
-           s = scm_append (scm_list_3 (scm_list_1 (scm_car (s)),
-                                       scm_vector_to_list (ps->get_paper_systems ()),
-                                       scm_cdr (s)));
-         else
-           system_specs_.push_back (System_spec (ps));
+         system_specs_.push_back (System_spec (ps));
        }
       else
         {
@@ -328,13 +534,38 @@ Page_breaking::find_chunks_and_breaks (Break_predicate is_break)
     {
       if (system_specs_[i].pscore_)
        {
-         vector<Grob*> cols
-           = system_specs_[i].pscore_->root_system ()->used_columns ();
+         vector<Grob*> cols = system_specs_[i].pscore_->root_system ()->used_columns ();
+         vector<Grob*> forced_line_break_cols;
+
+         SCM system_count = system_specs_[i].pscore_->layout ()->c_variable ("system-count");
+         if (scm_is_number (system_count))
+           {
+             // With system-count given, the line configuration for
+             // this score is fixed.  We need to ensure that chunk
+             // boundaries only occur at line breaks.
+             Constrained_breaking breaking (system_specs_[i].pscore_);
+             vector<Line_details> details = breaking.line_details (0, VPOS, scm_to_int (system_count));
+
+             for (vsize j = 0; j < details.size (); j++)
+               forced_line_break_cols.push_back (details[j].last_column_);
+           }
+
+         int last_forced_line_break_idx = 0;
+         vsize forced_line_break_idx = 0;
          vector<vsize> line_breaker_columns;
          line_breaker_columns.push_back (0);
 
          for (vsize j = 1; j < cols.size (); j++)
            {
+             if (forced_line_break_cols.size ())
+               {
+                 if (forced_line_break_idx >= forced_line_break_cols.size ()
+                     || forced_line_break_cols[forced_line_break_idx] != cols[j])
+                   continue;
+                 else
+                   forced_line_break_idx++;
+               }
+
              bool last = (j == cols.size () - 1);
              bool break_point = is_break (cols[j]);
              bool chunk_end = cols[j]->get_property ("page-break-permission") == force_sym;
@@ -343,10 +574,22 @@ Page_breaking::find_chunks_and_breaks (Break_predicate is_break)
                                                       cols[j],
                                                       last);
 
+             // NOTE: even in the breaks_ list, forced_line_count_
+             // refers to the number of lines between a
+             // Break_position and the start of that /chunk/.  This
+             // is needed for system_count_bounds to work correctly,
+             // since it mixes Break_positions from breaks_ and
+             // chunks_.
+             if (scm_is_number (system_count))
+               cur_pos.forced_line_count_ = forced_line_break_idx - last_forced_line_break_idx;
+
              if (break_point || (i == system_specs_.size () - 1 && last))
                breaks_.push_back (cur_pos);
              if (chunk_end || last)
-               chunks_.push_back (cur_pos);
+               {
+                 chunks_.push_back (cur_pos);
+                 last_forced_line_break_idx = forced_line_break_idx;
+               }
 
              if ((break_point || chunk_end) && !last)
                line_breaker_columns.push_back (j);
@@ -422,7 +665,10 @@ Page_breaking::system_count_bounds (vector<Break_position> const &chunks,
   for (vsize i = 0; i + 1 < chunks.size (); i++)
     {
       vsize sys = next_system (chunks[i]);
-      if (system_specs_[sys].pscore_)
+
+      if (chunks[i+1].forced_line_count_)
+       ret[i] = chunks[i+1].forced_line_count_;
+      else if (system_specs_[sys].pscore_)
        {
          vsize start;
          vsize end;
@@ -443,6 +689,7 @@ Page_breaking::set_current_breakpoints (vsize start,
                                        Line_division lower_bound,
                                        Line_division upper_bound)
 {
+  system_count_ = system_count;
   current_chunks_ = chunk_list (start, end);
   current_start_breakpoint_ = start;
   current_end_breakpoint_ = end;
@@ -498,18 +745,24 @@ Page_breaking::set_to_ideal_line_configuration (vsize start, vsize end)
   current_start_breakpoint_ = start;
   current_end_breakpoint_ = end;
   clear_line_details_cache ();
+  system_count_ = 0;
 
   Line_division div;
   for (vsize i = 0; i+1 < current_chunks_.size (); i++)
     {
       vsize sys = next_system (current_chunks_[i]);
-      if (system_specs_[sys].pscore_)
+
+      if (current_chunks_[i+1].forced_line_count_)
+       div.push_back (current_chunks_[i+1].forced_line_count_);
+      else if (system_specs_[sys].pscore_)
        {
          line_breaker_args (sys, current_chunks_[i], current_chunks_[i+1], &start, &end);
          div.push_back (line_breaking_[sys].best_solution (start, end).size ());
        }
       else
        div.push_back (1);
+
+      system_count_ += div.back ();
     }
   current_configurations_.clear ();
   current_configurations_.push_back (div);
@@ -527,10 +780,6 @@ Page_breaking::cache_line_details (vsize configuration_index)
   if (cached_configuration_index_ != configuration_index)
     {
       cached_configuration_index_ = configuration_index;
-      SCM padding_scm = book_->paper_->c_variable ("page-breaking-between-system-padding");
-      if (!scm_is_number (padding_scm))
-       padding_scm = book_->paper_->c_variable ("between-system-padding");
-      Real padding = robust_scm2double (padding_scm, 0.0);
 
       Line_division &div = current_configurations_[configuration_index];
       uncompressed_line_details_.clear ();
@@ -549,10 +798,7 @@ Page_breaking::cache_line_details (vsize configuration_index)
          else
            {
              assert (div[i] == 1);
-             uncompressed_line_details_.push_back (Line_details (system_specs_[sys].prob_));
-             uncompressed_line_details_.back ().padding_ =
-                robust_scm2double (system_specs_[sys].prob_->get_property ("next-padding"),
-                                   padding);
+             uncompressed_line_details_.push_back (Line_details (system_specs_[sys].prob_, book_->paper_));
            }
        }
       cached_line_details_ = compress_lines (uncompressed_line_details_);
@@ -606,37 +852,97 @@ Page_breaking::line_divisions_rec (vsize system_count,
     }
 }
 
+void
+Page_breaking::compute_line_heights ()
+{
+  Real prev_hanging = 0;
+  Real prev_hanging_begin = 0;
+  Real prev_hanging_rest = 0;
+  Real prev_refpoint_hanging = 0;
+  for (vsize i = 0; i < cached_line_details_.size (); i++)
+    {
+      Line_shape shape = cached_line_details_[i].shape_;
+      Real a = shape.begin_[UP];
+      Real b = shape.rest_[UP];
+      bool title = cached_line_details_[i].title_;
+      Real refpoint_hanging = max (prev_hanging_begin + a, prev_hanging_rest + b);
+
+      if (i > 0)
+       {
+         Real padding = 0;
+         if (!cached_line_details_[i].tight_spacing_)
+           padding = title
+             ? cached_line_details_[i-1].title_padding_
+             : cached_line_details_[i-1].padding_;
+         Real min_dist = title
+           ? cached_line_details_[i-1].title_min_distance_
+           : cached_line_details_[i-1].min_distance_;
+         refpoint_hanging = max (refpoint_hanging + padding,
+                                 prev_refpoint_hanging + min_dist
+                                 + cached_line_details_[i].first_refpoint_offset_);
+       }
+
+      Real hanging_begin = refpoint_hanging - shape.begin_[DOWN];
+      Real hanging_rest = refpoint_hanging - shape.rest_[DOWN];
+      Real hanging = max (hanging_begin, hanging_rest);
+      cached_line_details_[i].tallness_ = hanging - prev_hanging;
+      prev_hanging = hanging;
+      prev_hanging_begin = hanging_begin;
+      prev_hanging_rest = hanging_rest;
+      prev_refpoint_hanging = refpoint_hanging;
+    }
+}
+
 vsize
 Page_breaking::min_page_count (vsize configuration, vsize first_page_num)
 {
   vsize ret = 1;
+  vsize page_starter = 0;
   Real cur_rod_height = 0;
   Real cur_spring_height = 0;
   Real cur_page_height = page_height (first_page_num, false);
+  int line_count = 0;
 
   cache_line_details (configuration);
+  compute_line_heights ();
+
+  if (cached_line_details_.size ())
+    cur_page_height -= min_whitespace_at_top_of_page (cached_line_details_[0]);
+
   for (vsize i = 0; i < cached_line_details_.size (); i++)
     {
-      Real ext_len = cached_line_details_[i].extent_.length ();
-      Real next_rod_height = cur_rod_height + ext_len
-       + ((cur_rod_height > 0) ? cached_line_details_[i].padding_: 0);
-      Real next_spring_height = cur_spring_height + cached_line_details_[i].space_;
-      Real next_height = next_rod_height + (ragged () ? next_spring_height : 0);
+      Real ext_len;
+      if (cur_rod_height > 0)
+       ext_len = cached_line_details_[i].tallness_;
+      else
+       ext_len = cached_line_details_[i].full_height();
 
+      Real next_rod_height = cur_rod_height + ext_len;
+      Real next_spring_height = cur_spring_height + cached_line_details_[i].space_;
+      Real next_height = next_rod_height + (ragged () ? next_spring_height : 0)
+       + min_whitespace_at_bottom_of_page (cached_line_details_[i]);
+      int next_line_count = line_count + cached_line_details_[i].compressed_nontitle_lines_count_;
 
-      if ((next_height > cur_page_height && cur_rod_height > 0)
+      if ((!too_few_lines (line_count) && (next_height > cur_page_height && cur_rod_height > 0))
+         || too_many_lines (next_line_count)
          || (i > 0
              && cached_line_details_[i-1].page_permission_ == ly_symbol2scm ("force")))
        {
-         cur_rod_height = ext_len;
+         line_count = cached_line_details_[i].compressed_nontitle_lines_count_;
+         cur_rod_height = cached_line_details_[i].full_height();
          cur_spring_height = cached_line_details_[i].space_;
+         page_starter = i;
+
          cur_page_height = page_height (first_page_num + ret, false);
+         cur_page_height -= min_whitespace_at_top_of_page (cached_line_details_[i]);
+
          ret++;
        }
       else
        {
          cur_rod_height = next_rod_height;
          cur_spring_height = next_spring_height;
+         line_count = next_line_count;
        }
     }
 
@@ -654,30 +960,47 @@ Page_breaking::min_page_count (vsize configuration, vsize first_page_num)
   */
 
   cur_page_height = page_height (first_page_num + ret - 1, true);
+  cur_page_height -= min_whitespace_at_top_of_page (cached_line_details_[page_starter]);
+  cur_page_height -= min_whitespace_at_bottom_of_page (cached_line_details_.back ());
+
   Real cur_height = cur_rod_height + ((ragged_last () || ragged ()) ? cur_spring_height : 0);
-  if (cur_height > cur_page_height
+  if (!too_few_lines (line_count - cached_line_details_.back ().compressed_nontitle_lines_count_)
+      && cur_height > cur_page_height
       /* don't increase the page count if the last page had only one system */
-      && cur_rod_height > cached_line_details_.back ().extent_.length ())
+      && cur_rod_height > cached_line_details_.back ().full_height ())
     ret++;
 
   assert (ret <= cached_line_details_.size ());
   return ret;
 }
 
+// If systems_per_page_ is positive, we don't really try to space on N pages;
+// we just put the requested number of systems on each page and penalize
+// if the result doesn't have N pages.
 Page_spacing_result
 Page_breaking::space_systems_on_n_pages (vsize configuration, vsize n, vsize first_page_num)
 {
   Page_spacing_result ret;
-  assert (n >= min_page_count (configuration, first_page_num));
+
+  if (systems_per_page_ > 0)
+    {
+      Page_spacing_result ret = space_systems_with_fixed_number_per_page (configuration, first_page_num);
+      ret.demerits_ += (ret.force_.size () == n) ? 0 : BAD_SPACING_PENALTY;
+      return ret;
+    }
 
   cache_line_details (configuration);
-  if (n > cached_line_details_.size ())
-    return Page_spacing_result ();
-  if (n == 1)
+  bool valid_n = (n >= min_page_count (configuration, first_page_num)
+                 && n <= cached_line_details_.size ());
+
+  if (!valid_n)
+    programming_error ("number of pages is out of bounds");
+
+  if (n == 1 && valid_n)
     ret = space_systems_on_1_page (cached_line_details_,
                                   page_height (first_page_num, is_last ()),
                                   ragged () || (is_last () && ragged_last ()));
-  else if (n == 2)
+  else if (n == 2 && valid_n)
     ret = space_systems_on_2_pages (configuration, first_page_num);
   else
     {
@@ -691,20 +1014,46 @@ Page_breaking::space_systems_on_n_pages (vsize configuration, vsize n, vsize fir
 Real
 Page_breaking::blank_page_penalty () const
 {
-  SCM penalty_sym = is_last () ? ly_symbol2scm ("blank-last-page-force") : ly_symbol2scm ("blank-page-force");
+  SCM penalty_sym;
+
+  if (is_last ())
+    penalty_sym = ly_symbol2scm ("blank-last-page-force");
+  else if (ends_score ())
+    penalty_sym = ly_symbol2scm ("blank-after-score-page-force");
+  else
+    penalty_sym = ly_symbol2scm ("blank-page-force");
+
+  Break_position const &pos = breaks_[current_end_breakpoint_];
+  if (Paper_score *ps = system_specs_[pos.system_spec_index_].pscore_)
+    return robust_scm2double (ps->layout ()->lookup_variable (penalty_sym), 0.0);
+
   return robust_scm2double (book_->paper_->lookup_variable (penalty_sym), 0.0);
 }
 
+// If systems_per_page_ is positive, we don't really try to space on N
+// or N+1 pages; see the comment to space_systems_on_n_pages.
 Page_spacing_result
-Page_breaking::space_systems_on_n_or_one_more_pages (vsize configuration, vsize n, vsize first_page_num)
+Page_breaking::space_systems_on_n_or_one_more_pages (vsize configuration, vsize n, vsize first_page_num,
+                                                    Real penalty_for_fewer_pages)
 {
   Page_spacing_result n_res;
   Page_spacing_result m_res;
 
+  if (systems_per_page_ > 0)
+    {
+      Page_spacing_result ret = space_systems_with_fixed_number_per_page (configuration, first_page_num);
+      ret.demerits_ += (ret.force_.size () == n || ret.force_.size () == (n-1)) ? 0 : BAD_SPACING_PENALTY;
+      return ret;
+    }
+
   cache_line_details (configuration);
   vsize min_p_count = min_page_count (configuration, first_page_num);
+  bool valid_n = n >= min_p_count || n <= cached_line_details_.size ();
 
-  if (n == 1)
+  if (!valid_n)
+    programming_error ("both page counts are out of bounds");
+
+  if (n == 1 && valid_n)
     {
       bool rag = ragged () || (is_last () && ragged_last ());
       Real height = page_height (first_page_num, is_last ());
@@ -718,20 +1067,20 @@ Page_breaking::space_systems_on_n_or_one_more_pages (vsize configuration, vsize
     {
       Page_spacer ps (cached_line_details_, first_page_num, this);
       
-      if (n >= min_p_count)
+      if (n >= min_p_count || !valid_n)
        n_res = ps.solve (n);
-      if (n < cached_line_details_.size ())
+      if (n < cached_line_details_.size () || !valid_n)
        m_res = ps.solve (n+1);
     }
 
   m_res = finalize_spacing_result (configuration, m_res);
   n_res = finalize_spacing_result (configuration, n_res);
 
-  Real penalty = blank_page_penalty ();
-  n_res.demerits_ += penalty;
+  Real page_spacing_weight = robust_scm2double (book_->paper_->c_variable ("page-spacing-weight"), 10);
+  n_res.demerits_ += penalty_for_fewer_pages * page_spacing_weight;
 
   if (n_res.force_.size ())
-    n_res.force_.back () += penalty;
+    n_res.force_.back () += penalty_for_fewer_pages;
 
   return (m_res.demerits_ < n_res.demerits_) ? m_res : n_res;
 }
@@ -740,34 +1089,84 @@ Page_spacing_result
 Page_breaking::space_systems_on_best_pages (vsize configuration, vsize first_page_num)
 {
   vsize min_p_count = min_page_count (configuration, first_page_num);
-  Real odd_pages_penalty = blank_page_penalty ();
 
   cache_line_details (configuration);
   Page_spacer ps (cached_line_details_, first_page_num, this);
   Page_spacing_result best = ps.solve (min_p_count);
-  best.force_.back () += (min_p_count % 2) ? odd_pages_penalty : 0;
-  best.demerits_ += (min_p_count % 2) ? odd_pages_penalty : 0;
 
   for (vsize i = min_p_count+1; i <= cached_line_details_.size (); i++)
     {
       Page_spacing_result cur = ps.solve (i);
-      cur.demerits_ += (i % 2) ? odd_pages_penalty : 0;
       if (cur.demerits_ < best.demerits_)
        best = cur;
     }
 
-  return finalize_spacing_result (configuration, best);
+  Page_spacing_result ret = finalize_spacing_result (configuration, best);
+  return ret;
+}
+
+Page_spacing_result
+Page_breaking::space_systems_with_fixed_number_per_page (vsize configuration,
+                                                        vsize first_page_num)
+{
+  Page_spacing_result res;
+  Page_spacing space (page_height (first_page_num, false), this);
+  vsize line = 0;
+  vsize page = 0;
+  vsize page_first_line = 0;
+
+  cache_line_details (configuration);
+  while (line < cached_line_details_.size ())
+    {
+      page++;
+      space.clear ();
+      space.resize (page_height (first_page_num + page, false));
+
+      int system_count_on_this_page = 0;
+      while (system_count_on_this_page < systems_per_page_
+            && line < cached_line_details_.size ())
+       {
+         Line_details const &cur_line = cached_line_details_[line];
+         space.append_system (cur_line);
+         system_count_on_this_page += cur_line.compressed_nontitle_lines_count_;
+         line++;
+
+         if (cur_line.page_permission_ == ly_symbol2scm ("force"))
+           break;
+       }
+
+      res.systems_per_page_.push_back (line - page_first_line);
+
+      res.force_.push_back (space.force_);
+      res.penalty_ += cached_line_details_[line-1].page_penalty_;
+      if (system_count_on_this_page != systems_per_page_)
+       {
+         res.penalty_ += TERRIBLE_SPACING_PENALTY;
+         res.system_count_status_ |= ((system_count_on_this_page < systems_per_page_))
+           ? SYSTEM_COUNT_TOO_FEW : SYSTEM_COUNT_TOO_MANY;
+       }
+
+      page_first_line = line;
+    }
+
+  /* Recalculate forces for the last page because we know now that is
+     really the last page. */
+  space.resize (page_height (first_page_num + page, true));
+  res.force_.back () = space.force_;
+  return finalize_spacing_result (configuration, res);
 }
 
 Page_spacing_result
 Page_breaking::pack_systems_on_least_pages (vsize configuration, vsize first_page_num)
 {
+  // TODO: add support for min/max-systems-per-page.
   Page_spacing_result res;
   vsize page = 0;
   vsize page_first_line = 0;
-  Page_spacing space (page_height (first_page_num, false));
+  Page_spacing space (page_height (first_page_num, false), this);
 
   cache_line_details (configuration);
+  compute_line_heights ();
   for (vsize line = 0; line < cached_line_details_.size (); line++)
     {
       Real prev_force = space.force_;
@@ -831,7 +1230,7 @@ Page_breaking::finalize_spacing_result (vsize configuration, Page_spacing_result
 
   Real line_force = 0;
   Real line_penalty = 0;
-  Real page_force = 0;
+  Real page_demerits = res.penalty_;
   Real page_weighting = robust_scm2double (book_->paper_->c_variable ("page-spacing-weight"), 10);
 
   for (vsize i = 0; i < uncompressed_line_details_.size (); i++)
@@ -843,10 +1242,8 @@ Page_breaking::finalize_spacing_result (vsize configuration, Page_spacing_result
   for (vsize i = 0; i < res.force_.size (); i++)
     {
       Real f = res.force_[i];
-      if (isinf (f) && res.systems_per_page_[i] == 1)
-       f = 20000;
 
-      page_force += f * f;
+      page_demerits += min(f*f, BAD_SPACING_PENALTY);
     }
 
   /* for a while we tried averaging page and line forces across pages instead
@@ -854,7 +1251,7 @@ Page_breaking::finalize_spacing_result (vsize configuration, Page_spacing_result
      with a very bad page force (for example because of a forced page break),
      the page breaker will put in a _lot_ of pages so that the bad force
      becomes averaged out over many pages. */
-  res.demerits_ = line_force + line_penalty + (page_force + res.penalty_) * page_weighting;
+  res.demerits_ = line_force + line_penalty + page_demerits * page_weighting;
   return res;
 
 }
@@ -869,15 +1266,20 @@ Page_breaking::finalize_spacing_result (vsize configuration, Page_spacing_result
 Page_spacing_result
 Page_breaking::space_systems_on_1_page (vector<Line_details> const &lines, Real page_height, bool ragged)
 {
-  Page_spacing space (page_height);
+  Page_spacing space (page_height, this);
   Page_spacing_result ret;
+  int line_count = 0;
 
   for (vsize i = 0; i < lines.size (); i++)
-    space.append_system (lines[i]);
+    {
+      space.append_system (lines[i]);
+      line_count += lines[i].compressed_nontitle_lines_count_;
+    }
 
   ret.systems_per_page_.push_back (lines.size ());
   ret.force_.push_back (ragged ? min (space.force_, 0.0) : space.force_);
-  ret.penalty_ = lines.back ().page_penalty_ + lines.back ().turn_penalty_;
+  ret.penalty_ = line_count_penalty (line_count) + lines.back ().page_penalty_ + lines.back ().turn_penalty_;
+  ret.system_count_status_ |= line_count_status (line_count);
 
   /* don't do finalize_spacing_result () because we are only an internal function */
   return ret;
@@ -904,29 +1306,54 @@ Page_breaking::space_systems_on_2_pages (vsize configuration, vsize first_page_n
        p1.systems_per_page_.push_back (p2.systems_per_page_[0]);
        p1.force_.push_back (p2.force_[0]);
        p1.penalty_ += p2.penalty_ - cached_line_details_[i].turn_penalty_;
+       p1.system_count_status_ |= p2.system_count_status_;
        return p1;
       }
 
   vector<Real> page1_force;
   vector<Real> page2_force;
-  Page_spacing page1 (page1_height);
-  Page_spacing page2 (page2_height);
+
+  // page1_penalty and page2_penalty store the penalties based
+  // on min-systems-per-page and max-systems-per-page.
+  vector<Real> page1_penalty;
+  vector<Real> page2_penalty;
+
+  // page1_status and page2_status keep track of whether the min-systems-per-page
+  // and max-systems-per-page constraints are satisfied.
+  vector<int> page1_status;
+  vector<int> page2_status;
+
+  Page_spacing page1 (page1_height, this);
+  Page_spacing page2 (page2_height, this);
+  int page1_line_count = 0;
+  int page2_line_count = 0;
 
   page1_force.resize (cached_line_details_.size () - 1, infinity_f);
   page2_force.resize (cached_line_details_.size () - 1, infinity_f);
+  page1_penalty.resize (cached_line_details_.size () - 1, infinity_f);
+  page2_penalty.resize (cached_line_details_.size () - 1, infinity_f);
+  page1_status.resize (cached_line_details_.size () - 1, 0);
+  page2_status.resize (cached_line_details_.size () - 1, 0);
 
   /* find the page 1 and page 2 forces for each page-breaking position */
   for (vsize i = 0; i < page1_force.size (); i++)
     {
       page1.append_system (cached_line_details_[i]);
       page2.prepend_system (cached_line_details_[cached_line_details_.size () - 1 - i]);
+      page1_line_count += cached_line_details_[i].compressed_nontitle_lines_count_;
+      page2_line_count += cached_line_details_[cached_line_details_.size () - 1 - i].compressed_nontitle_lines_count_;
+
       page1_force[i] = (ragged1 && page1.force_ < 0 && i > 0) ? infinity_f : page1.force_;
+      page1_penalty[i] = line_count_penalty (page1_line_count);
+      page1_status[i] = line_count_status (page1_line_count);
 
       if (ragged2)
        page2_force[page2_force.size () - 1 - i] =
          (page2.force_ < 0 && i + 1 < page1_force.size ()) ? infinity_f : 0;
       else
        page2_force[page2_force.size () - 1 - i] = page2.force_;
+      page2_penalty[page2_penalty.size () - 1 - i] = line_count_penalty (page2_line_count);
+      page2_status[page2_penalty.size () - 1 - i] = line_count_status (page2_line_count);
     }
 
   /* find the position that minimises the sum of the page forces */
@@ -935,8 +1362,12 @@ Page_breaking::space_systems_on_2_pages (vsize configuration, vsize first_page_n
   for (vsize i = 0; i < page1_force.size (); i++)
     {
       Real f = page1_force[i] * page1_force[i] + page2_force[i] * page2_force[i];
-      Real uneven = 2 * (page1_force[i] - page2_force[i]);
-      Real dem = uneven * uneven + f
+
+      // NOTE: we treat max-systems-per-page and min-systems-per-page as soft
+      // constraints. That is, we penalize harshly when they don't happen
+      // but we don't completely reject.
+      Real dem = f
+       + page1_penalty[i] + page2_penalty[i]
        + cached_line_details_[i+1].page_penalty_
        + cached_line_details_.back ().page_penalty_ + cached_line_details_.back ().turn_penalty_;
       if (dem < best_demerits)
@@ -951,9 +1382,11 @@ Page_breaking::space_systems_on_2_pages (vsize configuration, vsize first_page_n
   ret.systems_per_page_.push_back (cached_line_details_.size () - best_sys_count);
   ret.force_.push_back (page1_force[best_sys_count-1]);
   ret.force_.push_back (page2_force[best_sys_count-1]);
+  ret.system_count_status_ = page1_status[best_sys_count-1] | page2_status[best_sys_count-1];
   ret.penalty_ = cached_line_details_[best_sys_count-1].page_penalty_
     + cached_line_details_.back ().page_penalty_
-    + cached_line_details_.back ().turn_penalty_;
+    + cached_line_details_.back ().turn_penalty_
+    + page1_penalty[best_sys_count-1] + page2_penalty[best_sys_count-1];
 
   /* don't do finalize_spacing_result () because we are only an internal function */
   return ret;
@@ -982,8 +1415,64 @@ Page_breaking::is_last () const
   return current_end_breakpoint_ == last_break_position ();
 }
 
+bool
+Page_breaking::ends_score () const
+{
+  return breaks_[current_end_breakpoint_].score_ender_;
+}
+
 vsize
 Page_breaking::last_break_position () const
 {
   return breaks_.size () - 1;  
 }
+
+// This gives the minimum distance between the top of the
+// printable area (ie. the bottom of the top-margin) and
+// the extent box of the topmost system.
+Real
+Page_breaking::min_whitespace_at_top_of_page (Line_details const &line) const
+{
+  SCM first_system_spacing = book_->paper_->c_variable ("top-system-spacing");
+  if (line.title_)
+    first_system_spacing = book_->paper_->c_variable ("top-title-spacing");
+
+  Real min_distance = -infinity_f;
+  Real padding = 0;
+
+  Page_layout_problem::read_spacing_spec (first_system_spacing,
+                                         &min_distance,
+                                         ly_symbol2scm ("minimum-distance"));
+  Page_layout_problem::read_spacing_spec (first_system_spacing,
+                                         &padding,
+                                         ly_symbol2scm ("padding"));
+
+  // FIXME: take into account the height of the header
+  Real translate = max (line.shape_.begin_[UP], line.shape_.rest_[UP]);
+  return max (0.0, max (padding, min_distance - translate));
+}
+
+Real
+Page_breaking::min_whitespace_at_bottom_of_page (Line_details const &line) const
+{
+  SCM last_system_spacing = book_->paper_->c_variable ("bottom-system-spacing");
+  Real min_distance = -infinity_f;
+  Real padding = 0;
+
+  Page_layout_problem::read_spacing_spec (last_system_spacing,
+                                         &min_distance,
+                                         ly_symbol2scm ("minimum-distance"));
+  Page_layout_problem::read_spacing_spec (last_system_spacing,
+                                         &padding,
+                                         ly_symbol2scm ("padding"));
+
+  // FIXME: take into account the height of the footer
+  Real translate = min (line.shape_.begin_[DOWN], line.shape_.rest_[DOWN]);
+  return max (0.0, max (padding, min_distance + translate));
+}
+
+int
+Page_breaking::orphan_penalty () const
+{
+  return orphan_penalty_;
+}