This introduces an algorithmic improvement and many cleanups in the page
breaking code. The algorithmic improvement is that we are able to adjust
line-counts on either side of a forced page break independently. This
code is contained in the Page_breaking class and abstracted nicely so
all subclasses can benefit.

"make web" works and output-distance.py doesn't find any changed files.

2006-08-17  Joe Neeman  <[EMAIL PROTECTED]>

        * lily/paper-column-engraver.cc (finalize): make the end of a score
        breakable by default. This is to balance out a change in behaviour
        of the page-turn-breaker which no longer makes the end of a score
        breakable.

        * lily/paper-book.cc (pages): set the systems_ once the pages are
        broken

        * lily/page-turn-page-breaking.cc (calc_subproblem): use the new
        Page_breaking interface.

        * lily/page-breaking.cc (class Page_breaking): make the interface
        more consistent and provide abstractions for dealing with
        Line_divisions.

        * lily/optimal-page-breaking.cc (solve): use a more straightforward
        algorithm. Use the new interface to Page_breaking.
Index: ChangeLog
===================================================================
RCS file: /sources/lilypond/lilypond/ChangeLog,v
retrieving revision 1.5241
diff -u -r1.5241 ChangeLog
--- ChangeLog	14 Aug 2006 08:30:20 -0000	1.5241
+++ ChangeLog	16 Aug 2006 21:35:04 -0000
@@ -1,3 +1,23 @@
+2006-08-17  Joe Neeman  <[EMAIL PROTECTED]>
+
+	* lily/paper-column-engraver.cc (finalize): make the end of a score
+	breakable by default. This is to balance out a change in behaviour
+	of the page-turn-breaker which no longer makes the end of a score
+	breakable.
+
+	* lily/paper-book.cc (pages): set the systems_ once the pages are
+	broken
+
+	* lily/page-turn-page-breaking.cc (calc_subproblem): use the new
+	Page_breaking interface.
+
+	* lily/page-breaking.cc (class Page_breaking): make the interface
+	more consistent and provide abstractions for dealing with
+	Line_divisions.
+
+	* lily/optimal-page-breaking.cc (solve): use a more straightforward
+	algorithm. Use the new interface to Page_breaking.
+
 2006-08-14  Mats Bengtsson  <[EMAIL PROTECTED]>
 
 	* scripts/lilypond-book.py (output): Remove obsolete(!?)
Index: lily/optimal-page-breaking.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/optimal-page-breaking.cc,v
retrieving revision 1.1
diff -u -r1.1 optimal-page-breaking.cc
--- lily/optimal-page-breaking.cc	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/optimal-page-breaking.cc	16 Aug 2006 21:35:04 -0000
@@ -1,5 +1,5 @@
 /*
-  optimal-page-breaking.hh -- implement a page-breaker that
+  optimal-page-breaking.cc -- implement a page-breaker that
   will break pages in such a way that both horizontal and
   vertical spacing will be acceptable
 
@@ -16,8 +16,15 @@
 #include "prob.hh"
 #include "system.hh"
 
+static bool
+break_p (Grob *g)
+{
+  (void) g; /* shutup warning */
+  return false;
+}
+
 Optimal_page_breaking::Optimal_page_breaking (Paper_book *pb)
-  : Page_breaking (pb, false)
+  : Page_breaking (pb, break_p)
 {
 }
 
@@ -26,9 +33,9 @@
 }
 
 Spacing_result
-Optimal_page_breaking::try_page_spacing (vector<vsize> line_count)
+Optimal_page_breaking::try_page_spacing (Line_division const &line_count)
 {
-  vector<Line_details> lines = get_line_details (0, breaks_.size () - 1, line_count);
+  vector<Line_details> lines = line_details (0, breaks_.size () - 1, line_count);
   Real page_h = page_height (1, false); // FIXME
   SCM force_sym = ly_symbol2scm ("blank-last-page-force");
   Real blank_force = robust_scm2double (book_->paper_->lookup_variable (force_sym), 0);
@@ -65,108 +72,60 @@
   return ret;
 }
 
-/* The algorithm is as follows:
-   1) break everything into its preferred number of lines
-   2) decrease the number of lines until we've decreased
-      the number of pages
-   3) increase the number of lines until we've increased
-      the number of pages
-   Take the best score we've found
-*/
 SCM
 Optimal_page_breaking::solve ()
 {
-  vector<vsize> ideal_line_count;
-  vector<vsize> max_line_count;
-  vector<vsize> min_line_count;
-  vector<vsize> last_best_line_count;
-  vector<vsize> best_line_count;
-  vsize last_line_total = 0;
-
-  calc_system_count_bounds (0, breaks_.size () - 1, &min_line_count, &max_line_count);
-  ideal_line_count.resize (all_.size (), 1);
-  for (vsize i = 0; i < all_.size (); i++)
+  vsize end = breaks_.size () - 1;
+  vsize min_sys_count = min_system_count (0, end);
+  vsize max_sys_count = max_system_count (0, end);
+  vsize max_page_count = INT_MAX;
+  vsize cur_page_count = 0;
+  Spacing_result best;
+  Line_division best_division;
+  Line_division lower_bound;
+
+  for (vsize sys_count = min_sys_count;
+       cur_page_count <= max_page_count && sys_count <= max_sys_count;
+       sys_count++)
     {
-      if (all_[i].pscore_)
-	ideal_line_count[i] = line_breaking_[i].get_best_solution (0, VPOS).size ();
-      last_line_total += ideal_line_count[i];
-    }
-
-  Spacing_result best_result = try_page_spacing (ideal_line_count);
-  vsize original_page_count = best_result.systems_per_page_.size ();
-  best_line_count = ideal_line_count;
-  last_best_line_count = ideal_line_count;
-
-  Direction d = original_page_count > 1 ? DOWN : UP;
-  vector<vector<vsize> > div;
-  Spacing_result this_best_result;
-  do {
-    do {
-      vector<vsize> blank;
-
-      vector<vsize> this_best_line_count;
-      this_best_result.demerits_ = infinity_f;
-
-      last_line_total += d;
-      div.clear ();
-      divide_systems (last_line_total,
-		      d == DOWN ? min_line_count       : last_best_line_count,
-		      d == DOWN ? last_best_line_count : max_line_count,
-		      &div, &blank);
-
-      for (vsize i = 0; i < div.size (); i++)
+      Real this_best_demerits = infinity_f;
+      vector<Line_division> div = line_divisions (0, end, sys_count, lower_bound);
+      for (vsize d = 0; d < div.size (); d++)
 	{
-	  Spacing_result cur = try_page_spacing (div[i]);
-	  if (cur.demerits_ < this_best_result.demerits_)
+	  Spacing_result cur = try_page_spacing (div[d]);
+	  cur_page_count = cur.systems_per_page_.size ();
+	  if (cur.demerits_ < best.demerits_)
 	    {
-	      this_best_result = cur;
-	      this_best_line_count = div[i];
+	      best = cur;
+	      best_division = div[d];
 	    }
-	}
-      last_best_line_count = this_best_line_count;
 
-      if (this_best_result.demerits_ < best_result.demerits_)
-	{
-	  best_line_count = this_best_line_count;
-	  best_result = this_best_result;
+	  if (cur.demerits_ < this_best_demerits)
+	    {
+	      this_best_demerits = cur.demerits_;
+	      lower_bound = div[d];
+	    }
+
+	  vector<Line_details> det = line_details (0, end, div[d]);
+	  bool all_lines_stretched = true;
+	  for (vsize i = 0; i < det.size (); i++)
+	    if (det[i].force_ < 0)
+	      all_lines_stretched = false;
+
+	  if (all_lines_stretched)
+	    max_page_count = cur_page_count + 1;
 	}
-    } while (div.size () && this_best_result.systems_per_page_.size () == original_page_count);
+    }
 
-    /* we're finished decreasing system count, let's try raising it */
-    last_best_line_count = ideal_line_count;
-    last_line_total = 0;
-    for (vsize i = 0; i < ideal_line_count.size (); i++)
-      last_line_total += ideal_line_count[i];
+  break_into_pieces (0, end, best_division);
+  vector<SCM> lines = systems ();
+  SCM lines_scm = SCM_EOL;
 
-  } while (flip (&d) != DOWN);
+  for (vsize i = 0; i < lines.size (); i++)
+    lines_scm = scm_cons (lines[i], lines_scm);
+  lines_scm = scm_reverse (lines_scm);
 
-  SCM lines = make_lines (best_line_count);
-  SCM pages = make_pages (best_result.systems_per_page_, lines);
+  SCM pages = make_pages (best.systems_per_page_, lines_scm);
   return pages;
 }
 
-SCM
-Optimal_page_breaking::make_lines (vector<vsize> line_count)
-{
-  assert (line_count.size () == all_.size ());
-
-  SCM ret = SCM_EOL;
-  for (vsize i = 0; i < all_.size (); i++)
-    {
-      if (all_[i].pscore_)
-	{
-	  vector<Column_x_positions> line_brk = line_breaking_[i].get_solution (0, VPOS, line_count[i]);
-	  System *sys = all_[i].pscore_->root_system ();
-
-	  sys->break_into_pieces (line_brk);
-	  ret = scm_append (scm_list_2 (ret, scm_vector_to_list (sys->get_paper_systems ())));
-	}
-      else
-	{
-	  SCM l = scm_cons (all_[i].prob_->self_scm (), SCM_EOL);
-	  ret = scm_append (scm_list_2 (ret, l));
-	  all_[i].prob_->unprotect ();
-	}
-    }
-  return ret;
-}
Index: lily/page-breaking-scheme.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/page-breaking-scheme.cc,v
retrieving revision 1.1
diff -u -r1.1 page-breaking-scheme.cc
--- lily/page-breaking-scheme.cc	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/page-breaking-scheme.cc	16 Aug 2006 21:35:04 -0000
@@ -28,3 +28,4 @@
   Optimal_page_breaking b (unsmob_paper_book (pb));
   return b.solve ();
 }
+
Index: lily/page-breaking.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/page-breaking.cc,v
retrieving revision 1.1
diff -u -r1.1 page-breaking.cc
--- lily/page-breaking.cc	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/page-breaking.cc	16 Aug 2006 21:35:05 -0000
@@ -1,6 +1,6 @@
 /*
   page-breaking.cc -- implement a superclass and utility
-  functions for use by various page-breaking algorithms
+  functions shared by various page-breaking algorithms
 
   source file of the GNU LilyPond music typesetter
 
@@ -19,27 +19,6 @@
 #include "system.hh"
 #include "warn.hh"
 
-System_spec::System_spec (Paper_score *ps, int break_count)
-{
-  pscore_ = ps;
-  prob_ = 0;
-  score_break_count_ = break_count;
-}
-
-System_spec::System_spec (Prob *pb)
-{
-  pscore_ = 0;
-  prob_ = pb;
-  score_break_count_ = 0;
-}
-
-System_spec::System_spec ()
-{
-  pscore_ = 0;
-  prob_ = 0;
-  score_break_count_ = 0;
-}
-
 /* for Page_breaking, the start index (when we are dealing with the stuff
    between a pair of breakpoints) refers to the break_ index of the end of
    the previous page. So the system index of the start of the current page
@@ -47,21 +26,22 @@
    it. */
 
 /* Turn a break index into the sys index that starts the next page */
-vsize Page_breaking::next_system (vsize start) const
+vsize Page_breaking::next_system (Break_position const &break_pos) const
 {
-  vsize sys = breaks_[start].sys_;
+  vsize sys = break_pos.sys_;
 
-  if (sys == VPOS) /* beginning of the piece */
+  if (sys == VPOS) /* beginning of the book */
     return 0;
-  if (all_[sys].pscore_ && all_[sys].score_break_count_ > breaks_[start].score_break_)
+  if (all_[sys].pscore_ && !break_pos.score_ender_)
     return sys; /* the score overflows the previous page */
   return sys + 1; /* this page starts with a new sys */
 }
 
-Page_breaking::Page_breaking (Paper_book *pb, bool allow_intra_score_breaks)
+Page_breaking::Page_breaking (Paper_book *pb, Break_p break_p)
 {
   book_ = pb;
-  create_system_list (allow_intra_score_breaks);
+  create_system_list ();
+  find_chunks_and_breaks (break_p);
 }
 
 Page_breaking::~Page_breaking ()
@@ -70,67 +50,96 @@
 
 /* translate indices into breaks_ into start-end parameters for the line breaker */
 void
-Page_breaking::line_breaker_args (vsize i, vsize *start, vsize *end)
+Page_breaking::line_breaker_args (vsize sys,
+				  Break_position const &start,
+				  Break_position const &end,
+				  vsize *line_breaker_start,
+				  vsize *line_breaker_end)
 {
-  assert (all_[i].pscore_);
-  assert (next_system (*start) <= i && i <= breaks_[*end].sys_);
+  assert (all_[sys].pscore_);
+  assert (next_system (start) <= sys && sys <= end.sys_);
 
-  vsize start_col = 0;
-  vsize end_col = VPOS;
-
-  if (breaks_[*start].sys_ == i)
-    start_col = breaks_[*start].score_break_;
-  if (breaks_[*end].sys_ == i)
-    end_col = breaks_[*end].score_break_;
+  if (start.sys_ == sys)
+    *line_breaker_start = start.score_break_;
+  else
+    *line_breaker_start = 0;
 
-  assert (end_col && (end_col == VPOS || end_col <= all_[breaks_[*end].sys_].score_break_count_));
-  *start = start_col;
-  *end = end_col;
+  if (end.sys_ == sys)
+    *line_breaker_end = end.score_break_;
+  else
+    *line_breaker_end = VPOS;
 }
 
-vector<Column_x_positions>
-Page_breaking::get_line_breaks (vsize i, vsize sys_count, vsize start, vsize end)
+void
+Page_breaking::break_into_pieces (vsize start_break, vsize end_break, Line_division const &div)
 {
-  assert (all_[i].pscore_);
-  line_breaker_args (i, &start, &end);
-  return line_breaking_[i].get_solution (start, end, sys_count);
+  vector<Break_position> chunks = chunk_list (start_break, end_break);
+  assert (chunks.size () == div.size () + 1);
+
+  for (vsize i = 0; i < chunks.size () - 1; i++)
+    {
+      vsize sys = next_system (chunks[i]);
+      if (all_[sys].pscore_)
+	{
+	  vsize start;
+	  vsize end;
+	  line_breaker_args (sys, chunks[i], chunks[i+1], &start, &end);
+
+	  vector<Column_x_positions> pos = line_breaking_[sys].get_solution (start, end, div[i]);
+	  all_[sys].pscore_->root_system ()->break_into_pieces (pos);
+	}
+    }
 }
 
-vector<Line_details>
-Page_breaking::get_line_details (vsize start_break, vsize end_break, vector<vsize> const &div)
+vector<SCM>
+Page_breaking::systems ()
 {
-  vector<Line_details> ret;
-
-  for (vsize i = next_system (start_break); i <= breaks_[end_break].sys_; i++)
+  vector<SCM> ret;
+  for (vsize sys = 0; sys < all_.size (); sys++)
     {
-      if (all_[i].pscore_)
+      if (all_[sys].pscore_)
 	{
-	  vsize div_index = i - next_system (start_break);
-	  vsize start = start_break;
-	  vsize end = end_break;
-
-	  line_breaker_args (i, &start, &end);
-	  vector<Line_details> l = line_breaking_[i].get_details (start, end, div[div_index]);
-	  ret.insert (ret.end (), l.begin (), l.end ());
+	  SCM lines = all_[sys].pscore_->root_system ()->get_paper_systems ();
+	  vsize line_count = scm_c_vector_length (lines);
+
+	  for (vsize i = 0; i < line_count; i++)
+	    ret.push_back (scm_c_vector_ref (lines, i));
 	}
       else
-	ret.push_back (Line_details (all_[i].prob_));
+	{
+	  ret.push_back (all_[sys].prob_->self_scm ());
+	  all_[sys].prob_->unprotect ();
+	}
     }
   return ret;
 }
 
-vsize
-Page_breaking::get_min_systems (vsize i, vsize start, vsize end)
+vector<Line_details>
+Page_breaking::line_details (vsize start_break, vsize end_break, Line_division const &div)
 {
-  line_breaker_args (i, &start, &end);
-  return line_breaking_[i].get_min_systems (start, end);
-}
+  vector<Break_position> chunks = chunk_list (start_break, end_break);
+  vector<Line_details> ret;
+  assert (chunks.size () == div.size () + 1);
 
-vsize
-Page_breaking::get_max_systems (vsize i, vsize start, vsize end)
-{
-  line_breaker_args (i, &start, &end);
-  return line_breaking_[i].get_max_systems (start, end);
+  for (vsize i = 0; i < chunks.size () - 1; i++)
+    {
+      vsize sys = next_system (chunks[i]);
+      if (all_[sys].pscore_)
+	{
+	  vsize start;
+	  vsize end;
+	  line_breaker_args (sys, chunks[i], chunks[i+1], &start, &end);
+
+	  vector<Line_details> details = line_breaking_[sys].get_details (start, end, div[i]);
+	  ret.insert (ret.end (), details.begin (), details.end ());
+	}
+      else
+	{
+	  assert (div[i] == 1);
+	  ret.push_back (Line_details (all_[sys].prob_));
+	}
+    }
+  return ret;
 }
 
 Real
@@ -179,105 +188,181 @@
   return scm_reverse (ret);
 }
 
-/* if allow_intra_score_breaks is false, that doesn't necessarily mean that there will
-   be no page turns in the middle of a score, only that we don't give special
-   consideration to any internal part of a score.
+/* The page-turn-page-breaker needs to have a line-breaker between any two
+   columns with non-NULL page-turn-permission.
+
+   The optimal-breaker needs to have a line-breaker between any two columns
+   with page-break-permission = 'force.
 
-   Corollary: if allow_intra_score_breaks is false, any \pageTurn or \noPageTurn commands
-   in the middle of a score will be ignored.
+   By using a grob predicate, we can accommodate both of these uses.
 */
 void
-Page_breaking::create_system_list (bool allow_intra_score_breaks)
+Page_breaking::create_system_list ()
 {
-  breaks_.push_back (Break_position ());
-
   SCM specs = book_->get_system_specs ();
   for (SCM s = specs; s != SCM_EOL; s = scm_cdr (s))
     {
       if (Paper_score *ps = dynamic_cast<Paper_score*> (unsmob_music_output (scm_car (s))))
-        {
-          /* add a breakpoint at the end of the last score, if necessary */
-          if (all_.size () && all_.back ().pscore_)
-            breaks_.push_back (Break_position (all_.size () - 1,
-                                               all_.back ().score_break_count_));
-
-          vector<vsize> score_brk;
-	  if (allow_intra_score_breaks)
-	    score_brk = find_page_break_indices (ps);
-
-          all_.push_back (System_spec (ps, score_brk.size () + 1));
-
-          for (vsize i = 0; i < score_brk.size(); i++)
-            breaks_.push_back (Break_position (all_.size () - 1, i + 1));
-
-          /* include a line breaker at the start of the score */
-          score_brk.insert (score_brk.begin (), 0);
-          line_breaking_.push_back (Constrained_breaking (score_brk));
-          line_breaking_.back ().set_pscore (ps);
-        }
+	all_.push_back (System_spec (ps));
       else
         {
           Prob *pb = unsmob_prob (scm_car (s));
           assert (pb);
 
           pb->protect ();
-          // ignore penalties (from break-before) in favour of using \pageBreak at the
-          // end of the score
-          if (all_.size () && all_.back ().pscore_)
-            breaks_.push_back (Break_position (all_.size () - 1, all_.back ().score_break_count_));
           all_.push_back (System_spec (pb));
-          line_breaking_.push_back (Constrained_breaking ());
         }
     }
+}
 
-  /* add the ending breakpoint */
-  if (all_.back ().pscore_)
-    breaks_.push_back (Break_position (all_.size () - 1, all_.back ().score_break_count_));
-  else
-    breaks_.push_back (Break_position (all_.size () - 1));
+void Page_breaking::find_chunks_and_breaks (Break_p break_p)
+{
+  SCM force_sym = ly_symbol2scm ("force");
+
+  chunks_.push_back (Break_position ());
+  breaks_.push_back (Break_position ());
+
+  for (vsize i = 0; i < all_.size (); i++)
+    {
+      if (all_[i].pscore_)
+	{
+	  vector<Grob*> cols = all_[i].pscore_->root_system ()->columns ();
+	  vector<vsize> line_breaker_columns;
+	  line_breaker_columns.push_back (0);
+
+	  for (vsize j = 0; j < cols.size (); j++)
+	    {
+	      bool last = j == cols.size () - 1;
+	      bool break_point = break_p (cols[j]);
+	      bool chunk_end = cols[i]->get_property ("page-break-permission") == force_sym;
+	      Break_position cur_pos = Break_position (i,
+						       line_breaker_columns.size (),
+						       last);
+
+	      if (break_point || (i == all_.size () - 1 && last))
+		breaks_.push_back (cur_pos);
+	      if (chunk_end || last)
+		chunks_.push_back (cur_pos);
+
+	      if ((break_point || chunk_end) && !last)
+		line_breaker_columns.push_back (j);
+	    }
+	  line_breaking_.push_back (Constrained_breaking (line_breaker_columns));
+	  line_breaking_.back ().set_pscore (all_[i].pscore_);
+	}
+      else
+	{
+	  /* TODO: we want some way of applying Break_p to a prob? */
+	  if (i == all_.size () - 1)
+	    breaks_.push_back (Break_position (i));
+
+	  chunks_.push_back (Break_position (i));
+	  line_breaking_.push_back (Constrained_breaking ());
+	}
+    }
 }
 
-vector<vsize>
-Page_breaking::find_page_break_indices (Paper_score *pscore)
+vector<Break_position>
+Page_breaking::chunk_list (vsize start_index, vsize end_index)
 {
-  vector<Grob*> all = pscore->root_system ()->columns ();
-  vector<vsize> ret;
+  Break_position start = breaks_[start_index];
+  Break_position end = breaks_[end_index];
 
-  /* we don't include breaks at the beginning and end */
-  for (vsize i = 0; i < all.size () - 1; i++)
-    if (scm_is_symbol (all[i]->get_property ("page-turn-permission")))
-      ret.push_back(i);
+  vsize i;
+  for (i = 0; i < chunks_.size () && chunks_[i] <= start; i++)
+    ;
+
+  vector<Break_position> ret;
+  ret.push_back (start);
+  for (; i < chunks_.size () && chunks_[i] < end; i++)
+    ret.push_back (chunks_[i]);
+  ret.push_back (end);
+  return ret;
+}
 
+vsize
+Page_breaking::min_system_count (vsize start, vsize end)
+{
+  vector<Break_position> chunks = chunk_list (start, end);
+  Line_division div = system_count_bounds (chunks, true);
+  vsize ret = 0;
+
+  for (vsize i = 0; i < div.size (); i++)
+    ret += div[i];
   return ret;
 }
 
-void
-Page_breaking::calc_system_count_bounds (vsize start, vsize end,
-                                            vector<vsize> *min,
-                                            vector<vsize> *max)
+vsize
+Page_breaking::max_system_count (vsize start, vsize end)
+{
+  vector<Break_position> chunks = chunk_list (start, end);
+  Line_division div = system_count_bounds (chunks, false);
+  vsize ret = 0;
+
+  for (vsize i = 0; i < div.size (); i++)
+    ret += div[i];
+  return ret;
+}
+
+Page_breaking::Line_division
+Page_breaking::system_count_bounds (vector<Break_position> const &chunks, bool min)
 {
-  for (vsize i = next_system (start); i <= breaks_[end].sys_; i++)
+  assert (chunks.size () >= 2);
+
+  Line_division ret;
+  ret.resize (chunks.size () - 1, 1);
+
+  for (vsize i = 0; i < chunks.size () - 1; i++)
     {
-      if (all_[i].pscore_)
-        {
-          min->push_back (get_min_systems (i, start, end));
-          max->push_back (get_max_systems (i, start, end));
-        }
-      else
-        {
-          min->push_back (1);
-          max->push_back (1);
-        }
+      vsize sys = next_system (chunks[i]);
+      if (all_[sys].pscore_)
+	{
+	  vsize start;
+	  vsize end;
+	  line_breaker_args (sys, chunks[i], chunks[i+1], &start, &end);
+	  ret[i] = min
+	    ? line_breaking_[sys].get_min_systems (start, end)
+	    : line_breaking_[sys].get_max_systems (start, end);
+	}
     }
+
+  return ret;
+}
+
+vector<Page_breaking::Line_division>
+Page_breaking::line_divisions (vsize start,
+			       vsize end,
+			       vsize system_count,
+			       Line_division lower_bound,
+			       Line_division upper_bound)
+{
+  vector<Break_position> chunks = chunk_list (start, end);
+
+  if (!lower_bound.size ())
+    lower_bound = system_count_bounds (chunks, true);
+  if (!upper_bound.size ())
+    upper_bound = system_count_bounds (chunks, false);
+
+  assert (lower_bound.size () == chunks.size () - 1);
+  assert (upper_bound.size () == chunks.size () - 1);
+
+  vector<Line_division> ret;
+  Line_division work_in_progress;
+
+  line_divisions_rec (system_count,
+		      lower_bound,
+		      upper_bound,
+		      &ret,
+		      &work_in_progress);
+  return ret;
 }
 
-/* calculate all possible ways of dividing system_count between the System_specs */
 void
-Page_breaking::divide_systems (vsize system_count,
-			       vector<vsize> const &min_sys,
-			       vector<vsize> const &max_sys,
-			       vector<vector<vsize> > *result,
-			       vector<vsize> *cur_division)
+Page_breaking::line_divisions_rec (vsize system_count,
+				   Line_division const &min_sys,
+				   Line_division const &max_sys,
+				   vector<Line_division > *result,
+				   Line_division *cur_division)
 {
   vsize my_index = cur_division->size ();
   vsize others_min = 0;
@@ -307,8 +392,7 @@
       if (my_index == min_sys.size () - 1)
         result->push_back (*cur_division);
       else
-        divide_systems (system_count - i, min_sys, max_sys, result, cur_division);
+        line_divisions_rec (system_count - i, min_sys, max_sys, result, cur_division);
       cur_division->pop_back ();
     }
 }
-
Index: lily/page-spacing.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/page-spacing.cc,v
retrieving revision 1.1
diff -u -r1.1 page-spacing.cc
--- lily/page-spacing.cc	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/page-spacing.cc	16 Aug 2006 21:35:05 -0000
@@ -219,43 +219,6 @@
   return ret;
 }
 
-/* for page_count > 2, we use a dynamic algorithm similar to
-   constrained-breaking -- we have a class that stores the intermediate
-   calculations so they can be reused for querying different page counts.
-*/
-
-class Page_spacer
-{
-public:
-  Page_spacer (vector<Line_details> const &lines, Real page_height);
-  Spacing_result solve (vsize page_count);
-
-private:
-  struct Page_spacing_node
-  {
-    Page_spacing_node ()
-    {
-      demerits_ = infinity_f;
-      force_ = infinity_f;
-      penalty_ = infinity_f;
-      prev_ = VPOS;
-    }
-
-    Real demerits_;
-    Real force_;
-    Real penalty_;
-    vsize prev_;
-  };
-
-  Real page_height_;
-  vector<Line_details> lines_;
-  Matrix<Page_spacing_node> state_;
-  vsize max_page_count_;
-
-  void resize (vsize page_count);
-  bool calc_subproblem (vsize page, vsize lines);
-};
-
 Page_spacer::Page_spacer (vector<Line_details> const &lines, Real page_height)
   : lines_ (lines)
 {
@@ -275,6 +238,9 @@
 
   vsize system = lines_.size () - 1;
 
+  if (isinf (state_.at (system, page_count-1).demerits_))
+    return Spacing_result (); /* bad number of pages */
+
   ret.penalty_ = state_.at (system, page_count-1).penalty_
     + lines_.back ().page_penalty_ + lines_.back ().turn_penalty_;
 
@@ -430,6 +396,7 @@
 
   Page_spacer ps (compressed_lines, page_height);
   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 <= compressed_lines.size (); i++)
Index: lily/page-turn-page-breaking.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/page-turn-page-breaking.cc,v
retrieving revision 1.1
diff -u -r1.1 page-turn-page-breaking.cc
--- lily/page-turn-page-breaking.cc	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/page-turn-page-breaking.cc	16 Aug 2006 21:35:05 -0000
@@ -18,8 +18,14 @@
 #include "system.hh"
 #include "warn.hh"
 
+static bool
+break_p (Grob *g)
+{
+  return scm_is_symbol (g->get_property ("page-turn-permission"));
+}
+
 Page_turn_page_breaking::Page_turn_page_breaking (Paper_book *pb)
-  : Page_breaking (pb, true)
+  : Page_breaking (pb, break_p)
 {
 }
 
@@ -52,7 +58,7 @@
 Page_turn_page_breaking::put_systems_on_pages (vsize start,
 					       vsize end,
 					       vector<Line_details> const &lines,
-					       vector<vsize> const &div,
+					       Line_division const &div,
 					       int page_number)
 {
   bool last = end == breaks_.size () - 1;
@@ -111,46 +117,26 @@
           p_num = f_p_num + p_count + ((f_p_num > 1) ? p_count % 2 : 0);
         }
 
-      vector<vsize> min_systems;
-      vector<vsize> max_systems;
-      vsize min_system_count = 0;
-      vsize max_system_count = 0;
-      this_start_best.demerits_ = infinity_f;
-      calc_system_count_bounds (start, end, &min_systems, &max_systems);
+      Line_division min_division;
+      Line_division max_division;
 
-      /* heuristic: we've prepended some music, only the first system is allowed
-         to get more lines */
-      if (this_start_best.page_count_ == 2 && this_start_best.div_.size ())
-        {
-          vsize ds = max_systems.size () - this_start_best.div_.size ();
-          for (vsize i = ds + 1; i < max_systems.size (); i++)
-            {
-              assert (this_start_best.div_[i - ds] <= max_systems[i]);
-              max_systems[i] = this_start_best.div_[i - ds];
-            }
-        }
-
-      for (vsize i = 0; i < min_systems.size (); i++)
-        {
-          min_system_count += min_systems[i];
-          max_system_count += max_systems[i];
-        }
+      vsize min_sys_count = min_system_count (start, end);
+      vsize max_sys_count = max_system_count (start, end);
+      this_start_best.demerits_ = infinity_f;
 
       bool ok_page = true;
 
       /* heuristic: we've just added a breakpoint, we'll need at least as
          many systems as before */
-      min_system_count = max (min_system_count, prev_best_system_count);
-      for (vsize sys_count = min_system_count; sys_count <= max_system_count && ok_page; sys_count++)
+      min_sys_count = max (min_sys_count, prev_best_system_count);
+      for (vsize sys_count = min_sys_count; sys_count <= max_sys_count && ok_page; sys_count++)
         {
-          vector<vector<vsize> > div;
-          vector<vsize> blank;
+	  vector<Line_division> div = line_divisions (start, end, sys_count, min_division, max_division);
           bool found = false;
-          divide_systems (sys_count, min_systems, max_systems, &div, &blank);
 
           for (vsize d = 0; d < div.size (); d++)
             {
-	      vector<Line_details> line = get_line_details (start, end, div[d]);
+	      vector<Line_details> line = line_details (start, end, div[d]);
 
               cur = put_systems_on_pages (start, end, line, div[d], p_num);
 
@@ -169,6 +155,10 @@
                   found = true;
                   this_start_best = cur;
                   prev_best_system_count = sys_count;
+
+		  /* heuristic: if we increase the number of systems, we can bound the
+		     division from below by our current best division */
+		  min_division = div[d];
                 }
             }
           if (!found && this_start_best.too_many_lines_)
@@ -222,39 +212,15 @@
       vsize start = n > 0 ? soln[n-1].break_pos_ : 0;
       vsize end = soln[n].break_pos_;
 
-      /* break each score into pieces */
-      for (vsize i = next_system (start); i <= breaks_[end].sys_; i++)
-        {
-          vsize d = i - next_system (start);
-          if (all_[i].pscore_)
-            {
-              vector<Column_x_positions> line_brk;
-
-              line_brk = get_line_breaks (i, soln[n].div_[d], start, end);
-              all_[i].pscore_->root_system ()->break_into_pieces (line_brk);
-              assert (line_brk.size () == soln[n].div_[d]);
-            }
-        }
+      break_into_pieces (start, end, soln[n].div_);
     }
+
+  vector<SCM> lines = systems ();
   SCM ret = SCM_EOL;
-  SCM *tail = &ret;
-  for (vsize i = 0; i < all_.size (); i++)
-    {
-      if (all_[i].pscore_)
-        for (SCM s = scm_vector_to_list (all_[i].pscore_->root_system ()->get_paper_systems ());
-              scm_is_pair (s); s = scm_cdr (s))
-          {
-            *tail = scm_cons (scm_car (s), SCM_EOL);
-            tail = SCM_CDRLOC (*tail);
-          }
-      else
-        {
-          *tail = scm_cons (all_[i].prob_->self_scm (), SCM_EOL);
-          all_[i].prob_->unprotect ();
-          tail = SCM_CDRLOC (*tail);
-        }
-    }
-  return ret;
+  for (vsize i = 0; i < lines.size (); i++)
+    ret = scm_cons (lines[i], ret);
+
+  return scm_reverse (ret);
 }
 
 SCM
Index: lily/paper-book.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/paper-book.cc,v
retrieving revision 1.133
diff -u -r1.133 paper-book.cc
--- lily/paper-book.cc	8 Aug 2006 10:01:22 -0000	1.133
+++ lily/paper-book.cc	16 Aug 2006 21:35:05 -0000
@@ -382,6 +382,20 @@
   pages_ = SCM_EOL;
   SCM proc = paper_->c_variable ("page-breaking");
   pages_ = scm_apply_0 (proc, scm_list_1(self_scm ()));
+
+  /* set systems_ from the pages */
+  if (systems_ == SCM_BOOL_F)
+    {
+      systems_ = SCM_EOL;
+      for (SCM p = pages_; p != SCM_EOL; p = scm_cdr (p))
+	{
+	  Prob *page = unsmob_prob (scm_car (p));
+	  SCM systems = page->get_property ("lines");
+
+	  systems_ = scm_append (scm_list_2 (systems_, systems));
+	}
+    }
+
   return pages_;
 }
 
Index: lily/paper-column-engraver.cc
===================================================================
RCS file: /sources/lilypond/lilypond/lily/paper-column-engraver.cc,v
retrieving revision 1.21
diff -u -r1.21 paper-column-engraver.cc
--- lily/paper-column-engraver.cc	8 Aug 2006 10:01:22 -0000	1.21
+++ lily/paper-column-engraver.cc	16 Aug 2006 21:35:05 -0000
@@ -43,6 +43,11 @@
     {
       command_column_->set_property ("line-break-permission", ly_symbol2scm ("allow"));
       system_->set_bound (RIGHT, command_column_);
+
+      /* FIXME: for now, we just make the end of any score page-turnable.
+	 There needs to be a better policy...
+      */
+      command_column_->set_property ("page-turn-permission", ly_symbol2scm ("allow"));
     }
 }
 
Index: lily/include/optimal-page-breaking.hh
===================================================================
RCS file: /sources/lilypond/lilypond/lily/include/optimal-page-breaking.hh,v
retrieving revision 1.1
diff -u -r1.1 optimal-page-breaking.hh
--- lily/include/optimal-page-breaking.hh	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/include/optimal-page-breaking.hh	16 Aug 2006 21:35:06 -0000
@@ -23,8 +23,7 @@
   virtual ~Optimal_page_breaking ();
 
 private:
-  SCM make_lines (vector<vsize> line_count);
-  Spacing_result try_page_spacing (vector<vsize> line_count);
+  Spacing_result try_page_spacing (Line_division const&);
 };
 
 #endif /* OPTIMAL_PAGE_BREAKING_HH */
Index: lily/include/page-breaking.hh
===================================================================
RCS file: /sources/lilypond/lilypond/lily/include/page-breaking.hh,v
retrieving revision 1.1
diff -u -r1.1 page-breaking.hh
--- lily/include/page-breaking.hh	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/include/page-breaking.hh	16 Aug 2006 21:35:06 -0000
@@ -17,66 +17,112 @@
  */
 struct System_spec
 {
-  System_spec (Paper_score*, int);
-  System_spec (Prob*);
-  System_spec ();
+  System_spec (Paper_score *ps)
+  {
+    pscore_ = ps;
+    prob_ = NULL;
+  }
+
+  System_spec (Prob *pb)
+  {
+    prob_ = pb;
+    pscore_ = NULL;
+  }
+
+  System_spec ()
+  {
+    pscore_ = NULL;
+    prob_ = NULL;
+  }
 
   Paper_score *pscore_;
   Prob *prob_;
-
-  vsize score_break_count_; /* for scores, this is the number of start-points our line-
-                               breaker has */
 };
 
 struct Break_position
 {
-  vsize sys_; /* the index in our all_ list */
+  vsize sys_; /* our index in the all_ list */
   vsize score_break_; /* if sys_ is a score, then we start at the score_brk_'th
                          possible page-break in the score */
+  bool score_ender_;
 
-  Break_position (vsize s=VPOS, vsize brk=VPOS)
+  Break_position (vsize s=VPOS, vsize brk=VPOS, bool end=false)
   {
     sys_ = s;
     score_break_ = brk;
+    score_ender_ = end;
+  }
+
+  bool operator< (const Break_position &other)
+  {
+    return (sys_ == VPOS && other.sys_ != VPOS)
+      || (sys_ < other.sys_)
+      || (sys_ == other.sys_ && score_break_ < other.score_break_);
+  }
+
+  bool operator<= (const Break_position &other)
+  {
+    return (sys_ == VPOS)
+      || (sys_ < other.sys_ && other.sys_ != VPOS)
+      || (sys_ == other.sys_ && score_break_ <= other.score_break_);
   }
 };
 
 class Page_breaking
 {
 public:
+  typedef bool (*Break_p) (Grob *);
+  typedef vector<vsize> Line_division;
   virtual SCM solve () = 0;
 
-  Page_breaking (Paper_book *pb, bool allow_intra_score_breaks);
+  Page_breaking (Paper_book *pb, Break_p);
   virtual ~Page_breaking ();
 
 protected:
-  std::vector<Break_position> breaks_;
-  std::vector<System_spec> all_;
-  std::vector<Constrained_breaking> line_breaking_;
-
   Paper_book *book_;
 
   Real page_height (int page_number, bool last);
   vsize next_system (vsize starting_break_index) const;
-
-  void create_system_list (bool allow_intra_score_breaks);
-  std::vector<vsize> find_page_break_indices (Paper_score *pscore);
+  vsize next_system (Break_position const &break_pos) const;
 
   SCM make_pages (vector<vsize> lines_per_page, SCM lines);
 
-  void calc_system_count_bounds (vsize start, vsize end,
-                                 vector<vsize> *min,
-                                 vector<vsize> *max);
-
-  void divide_systems (vsize system_count, vector<vsize> const &min,
-                                           vector<vsize> const &max,
-                                           vector<vector<vsize> > *result,
-                                           vector<vsize> *cur);
-
-  void line_breaker_args (vsize i, vsize *break_st, vsize *break_end);
-  vsize get_min_systems (vsize sys, vsize break_start, vsize break_end);
-  vsize get_max_systems (vsize sys, vsize break_start, vsize break_end);
-  vector<Column_x_positions> get_line_breaks (vsize sys, vsize sys_count, vsize st, vsize end);
-  vector<Line_details> get_line_details (vsize start_break, vsize end_break, vector<vsize> const &div);
+  vsize min_system_count (vsize start, vsize end);
+  vsize max_system_count (vsize start, vsize end);
+  vector<Line_details> line_details (vsize start, vsize end, Line_division const &div);
+
+  void break_into_pieces (vsize start, vsize end, Line_division const &div);
+  vector<SCM> systems ();
+
+
+  vector<Line_division> line_divisions (vsize start,
+					vsize end,
+					vsize system_count,
+					Line_division lower_bound = Line_division (),
+					Line_division upper_bound = Line_division ());
+
+  vector<Break_position> breaks_;
+
+private:
+  vector<Break_position> chunks_;
+  vector<System_spec> all_;
+  vector<Constrained_breaking> line_breaking_;
+
+  vector<Break_position> chunk_list (vsize start, vsize end);
+  Line_division system_count_bounds (vector<Break_position> const &chunks, bool min);
+  void line_breaker_args (vsize i,
+			  Break_position const &start,
+			  Break_position const &end,
+			  vsize *line_breaker_start,
+			  vsize *line_breaker_end);
+
+  void line_divisions_rec (vsize system_count,
+			   Line_division const &min,
+			   Line_division const &max,
+			   vector<Line_division> *result,
+			   Line_division *cur);
+
+  void create_system_list ();
+  void find_chunks_and_breaks (Break_p);
 };
 #endif /* PAGE_BREAKING_HH */
Index: lily/include/page-spacing.hh
===================================================================
RCS file: /sources/lilypond/lilypond/lily/include/page-spacing.hh,v
retrieving revision 1.1
diff -u -r1.1 page-spacing.hh
--- lily/include/page-spacing.hh	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/include/page-spacing.hh	16 Aug 2006 21:35:06 -0000
@@ -21,10 +21,47 @@
   Spacing_result ()
   {
     penalty_ = 0;
-    demerits_ = 0;
+    demerits_ = infinity_f;
   }
 };
 
+/* for page_count > 2, we use a dynamic algorithm similar to
+   constrained-breaking -- we have a class that stores the intermediate
+   calculations so they can be reused for querying different page counts.
+*/
+
+class Page_spacer
+{
+public:
+  Page_spacer (vector<Line_details> const &lines, Real page_height);
+  Spacing_result solve (vsize page_count);
+
+private:
+  struct Page_spacing_node
+  {
+    Page_spacing_node ()
+    {
+      demerits_ = infinity_f;
+      force_ = infinity_f;
+      penalty_ = infinity_f;
+      prev_ = VPOS;
+    }
+
+    Real demerits_;
+    Real force_;
+    Real penalty_;
+    vsize prev_;
+  };
+
+  Real page_height_;
+  vector<Line_details> lines_;
+  Matrix<Page_spacing_node> state_;
+  vsize max_page_count_;
+
+  void resize (vsize page_count);
+  bool calc_subproblem (vsize page, vsize lines);
+};
+
 Spacing_result
 space_systems_on_min_pages (vector<Line_details> const&,
 			    Real page_height,
Index: lily/include/page-turn-page-breaking.hh
===================================================================
RCS file: /sources/lilypond/lilypond/lily/include/page-turn-page-breaking.hh,v
retrieving revision 1.1
diff -u -r1.1 page-turn-page-breaking.hh
--- lily/include/page-turn-page-breaking.hh	8 Aug 2006 10:01:22 -0000	1.1
+++ lily/include/page-turn-page-breaking.hh	16 Aug 2006 21:35:06 -0000
@@ -45,7 +45,7 @@
     Real demerits_;
     vsize break_pos_; /* index into breaks_ */
 
-    vector<vsize> div_;  /* our division of systems between scores on this page */
+    Line_division div_;
     vector<vsize> system_count_; /* systems per page */
 
     Break_node ()
@@ -59,12 +59,12 @@
     }
   };
 
-  std::vector<Break_node> state_;
+  vector<Break_node> state_;
 
   Break_node put_systems_on_pages (vsize start,
 				   vsize end,
 				   vector<Line_details> const &lines,
-				   vector<vsize> const &system_div,
+				   Line_division const &div,
 				   int page_number);
 
   SCM make_lines (vector<Break_node> *breaks);
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