]> git.donarmstrong.com Git - lilypond.git/blobdiff - lily/page-layout-problem.cc
Fix 1240.
[lilypond.git] / lily / page-layout-problem.cc
index 61a7ebb90168cf26a747bdee0f31b269b50b7cb8..7292126ddcf52ee2d3f9030304792824cc36064d 100644 (file)
@@ -1,20 +1,32 @@
 /*
-  page-layout-problem.cc -- space systems nicely on a page. If systems can
-  be stretched, do that too.
+  This file is part of LilyPond, the GNU music typesetter.
 
-  source file of the GNU LilyPond music typesetter
+  Copyright (C) 2009--2010 Joe Neeman <joeneeman@gmail.com>
 
-  (c) 2009 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/>.
 */
 
 #include "page-layout-problem.hh"
 
 #include "align-interface.hh"
+#include "axis-group-interface.hh"
 #include "hara-kiri-group-spanner.hh"
 #include "international.hh"
 #include "item.hh"
 #include "output-def.hh"
 #include "paper-book.hh"
+#include "paper-column.hh"
 #include "pointer-group-interface.hh"
 #include "prob.hh"
 #include "skyline-pair.hh"
@@ -26,6 +38,8 @@ Page_layout_problem::Page_layout_problem (Paper_book *pb, SCM page_scm, SCM syst
   Prob *page = unsmob_prob (page_scm);
   header_height_ = 0;
   footer_height_ = 0;
+  header_padding_ = 0;
+  footer_padding_ = 0;
   page_height_ = 100;
 
   if (page)
@@ -43,34 +57,39 @@ Page_layout_problem::Page_layout_problem (Paper_book *pb, SCM page_scm, SCM syst
   // below the top of the printable area.
   bottom_skyline_.set_minimum_height (-header_height_);
 
-  SCM between_system_spacing = SCM_EOL;
-  SCM after_title_spacing = SCM_EOL;
-  SCM before_title_spacing = SCM_EOL;
-  SCM between_title_spacing = SCM_EOL;
+  SCM system_system_spacing = SCM_EOL;
+  SCM score_system_spacing = SCM_EOL;
+  SCM markup_system_spacing = SCM_EOL;
+  SCM score_markup_spacing = SCM_EOL;
+  SCM markup_markup_spacing = SCM_EOL;
 
-  // first_system_spacing controls the spring from the top of the printable
+  // top_system_spacing controls the spring from the top of the printable
   // area to the first staff. It allows the user to control the offset of
   // the first staff (as opposed to the top of the first system) from the
-  // top of the page. Similarly for last_system_spacing.
-  SCM first_system_spacing = SCM_EOL;
-  SCM last_system_spacing = SCM_EOL;
+  // top of the page. Similarly for last_bottom_spacing.
+  SCM top_system_spacing = SCM_EOL;
+  SCM last_bottom_spacing = SCM_EOL;
   if (pb && pb->paper_)
     {
       Output_def *paper = pb->paper_;
-      between_system_spacing = paper->c_variable ("between-system-spacing");
-      after_title_spacing = paper->c_variable ("after-title-spacing");
-      before_title_spacing = paper->c_variable ("before-title-spacing");
-      between_title_spacing = paper->c_variable ("between-title-spacing");
-      last_system_spacing = paper->c_variable ("last-system-spacing");
-      first_system_spacing = paper->c_variable ("first-system-spacing");
+      system_system_spacing = paper->c_variable ("system-system-spacing");
+      score_system_spacing = paper->c_variable ("score-system-spacing");
+      markup_system_spacing = paper->c_variable ("markup-system-spacing");
+      score_markup_spacing = paper->c_variable ("score-markup-spacing");
+      markup_markup_spacing = paper->c_variable ("markup-markup-spacing");
+      last_bottom_spacing = paper->c_variable ("last-bottom-spacing");
+      top_system_spacing = paper->c_variable ("top-system-spacing");
       if (scm_is_pair (systems) && unsmob_prob (scm_car (systems)))
-       first_system_spacing = paper->c_variable ("first-system-title-spacing");
+       top_system_spacing = paper->c_variable ("top-markup-spacing");
 
       // Note: the page height here does _not_ reserve space for headers and
-      // footers. This is because we want to anchor the first-system-spacing
+      // footers. This is because we want to anchor the top-system-spacing
       // spring at the _top_ of the header.
       page_height_ -= robust_scm2double (paper->c_variable ("top-margin"), 0)
        + robust_scm2double (paper->c_variable ("bottom-margin"), 0);
+
+      read_spacing_spec (top_system_spacing, &header_padding_, ly_symbol2scm ("padding"));
+      read_spacing_spec (last_bottom_spacing, &footer_padding_, ly_symbol2scm ("padding"));
     }
   bool last_system_was_title = false;
 
@@ -88,9 +107,15 @@ Page_layout_problem::Page_layout_problem (Paper_book *pb, SCM page_scm, SCM syst
              continue;
            }
 
-         SCM spec = first ? first_system_spacing
-           : (last_system_was_title ? after_title_spacing : between_system_spacing);
-         Spring spring (first ? 0 : 1, 0.0);
+         SCM spec = system_system_spacing;
+         if (first)
+           spec = top_system_spacing;
+         else if (last_system_was_title)
+           spec = markup_system_spacing;
+         else if (0 == Paper_column::get_rank (sys->get_bound (LEFT)))
+           spec = score_system_spacing;
+
+         Spring spring (0, 0);
          Real padding = 0.0;
          alter_spring_from_spacing_spec (spec, &spring);
          read_spacing_spec (spec, &padding, ly_symbol2scm ("padding"));
@@ -100,9 +125,9 @@ Page_layout_problem::Page_layout_problem (Paper_book *pb, SCM page_scm, SCM syst
        }
       else if (Prob *p = unsmob_prob (scm_car (s)))
        {
-         SCM spec = first ? first_system_spacing
-           : (last_system_was_title ? between_title_spacing : before_title_spacing);
-         Spring spring (first ? 0 : 1, 0.0);
+         SCM spec = first ? top_system_spacing
+           : (last_system_was_title ? markup_markup_spacing : score_markup_spacing);
+         Spring spring (0, 0);
          Real padding = 0.0;
          alter_spring_from_spacing_spec (spec, &spring);
          read_spacing_spec (spec, &padding, ly_symbol2scm ("padding"));
@@ -116,10 +141,30 @@ Page_layout_problem::Page_layout_problem (Paper_book *pb, SCM page_scm, SCM syst
 
   Spring last_spring (0, 0);
   Real last_padding = 0;
-  alter_spring_from_spacing_spec (last_system_spacing, &last_spring);
-  read_spacing_spec (last_system_spacing, &last_padding, ly_symbol2scm ("padding"));
+  alter_spring_from_spacing_spec (last_bottom_spacing, &last_spring);
+  read_spacing_spec (last_bottom_spacing, &last_padding, ly_symbol2scm ("padding"));
   last_spring.ensure_min_distance (last_padding - bottom_skyline_.max_height () + footer_height_);
   springs_.push_back (last_spring);
+
+  if (elements_.size ())
+    {
+      Real bottom_padding = 0;
+
+      // TODO: junk bottom-space now that we have last-bottom-spacing?
+      // bottom-space has the flexibility that one can do it per-system.
+      // NOTE: bottom-space is misnamed since it is not stretchable space.
+      if (Prob *p = elements_.back ().prob)
+       bottom_padding = robust_scm2double (p->get_property ("bottom-space"), 0);
+      else if (elements_.back ().staves.size ())
+       {
+         SCM details = get_details (elements_.back ());
+         bottom_padding = robust_scm2double (ly_assoc_get (ly_symbol2scm ("bottom-space"),
+                                                           details,
+                                                           SCM_BOOL_F),
+                                             0.0);
+       }
+      page_height_ -= bottom_padding;
+    }
 }
 
 void
@@ -134,32 +179,18 @@ Page_layout_problem::set_footer_height (Real height)
   footer_height_ = height;
 }
 
-Grob*
-Page_layout_problem::find_vertical_alignment (System *sys)
-{
-  extract_grob_set (sys, "elements", elts);
-  for (vsize i = 0; i < elts.size (); ++i)
-    if (Align_interface::has_interface (elts[i]))
-      return elts[i];
-
-  return 0;
-}
-
 void
 Page_layout_problem::append_system (System *sys, Spring const& spring, Real padding)
 {
-  Grob *align = find_vertical_alignment (sys);
+  Grob *align = sys->get_vertical_alignment ();
   if (!align)
-    {
-      sys->programming_error ("no VerticalAlignment in system: can't do vertical spacing");
-      return;
-    }
+    return;
 
   align->set_property ("positioning-done", SCM_BOOL_T);
 
   extract_grob_set (align, "elements", all_elts);
   vector<Grob*> elts = filter_dead_elements (all_elts);
-  vector<Real> minimum_offsets = Align_interface::get_minimum_translations (align, elts, Y_AXIS,
+  vector<Real> minimum_offsets = Align_interface::get_minimum_translations (align, elts, Y_AXIS, false,
                                                                            false, 0, 0);
 
   Skyline up_skyline (UP);
@@ -191,9 +222,6 @@ Page_layout_problem::append_system (System *sys, Spring const& spring, Real padd
          // we are only adding springs _between_ staves here.
          if (!found_spaceable_staff)
            {
-             if (i > 0)
-               add_loose_lines_as_spaceable_lines (elts, minimum_offsets, 0, i-1);
-
              found_spaceable_staff = true;
              last_spaceable_staff = i;
              continue;
@@ -204,7 +232,7 @@ Page_layout_problem::append_system (System *sys, Spring const& spring, Real padd
          alter_spring_from_spacing_spec (spec, &spring);
 
          springs_.push_back (spring);
-         Real min_distance = minimum_offsets[last_spaceable_staff] - minimum_offsets[i];
+         Real min_distance = (found_spaceable_staff ? minimum_offsets[last_spaceable_staff] : 0) - minimum_offsets[i];
          springs_.back ().ensure_min_distance (min_distance);
 
          if (scm_is_pair (manual_dists))
@@ -222,59 +250,21 @@ Page_layout_problem::append_system (System *sys, Spring const& spring, Real padd
          last_spaceable_staff = i;
        }
     }
-  // Any loose lines hanging off the end are treated as spaceable
-  // lines.  This might give slightly weird results if the hanging
-  // systems have staff-affinity != UP.  It's not quite clear what
-  // should happen in that case, though.
-  if (last_spaceable_staff + 1 < elts.size ())
-    add_loose_lines_as_spaceable_lines (elts, minimum_offsets,
-                                       found_spaceable_staff ? last_spaceable_staff + 1 : 0,
-                                       elts.size () - 1);
+
   // Corner case: there was only one staff, and it wasn't spaceable.
   // Mark it spaceable, because we do not allow non-spaceable staves
   // to be at the top or bottom of a system.
-  else if (!found_spaceable_staff && elts.size ())
+  if (!found_spaceable_staff && elts.size ())
     mark_as_spaceable (elts[0]);
 }
 
-// first and  last are inclusive
-void
-Page_layout_problem::add_loose_lines_as_spaceable_lines (vector<Grob*> const& elts,
-                                                        vector<Real> const& minimum_offsets,
-                                                        vsize first, vsize last)
-{
-  vsize start = first;
-  vsize end = last;
-  if (start > 0)
-    --start;
-  if (end + 1 < elts.size ())
-    ++end;
-  
-  for (vsize i = start; i < end; ++i)
-    {
-      SCM spec = get_spacing_spec (elts[i], elts[i+1]);
-      Spring spring (1.0, 0.0);
-      alter_spring_from_spacing_spec (spec, &spring);
-      if (spec == SCM_BOOL_F)
-       {
-         spring.set_inverse_compress_strength (10000);
-         spring.set_inverse_stretch_strength (10000);
-       }
-
-      Real min_distance = minimum_offsets[i] - minimum_offsets[i+1];
-      spring.ensure_min_distance (min_distance);
-      springs_.push_back (spring);
-    }
-
-  for (vsize i = first; i <= last; ++i)
-    mark_as_spaceable (elts[i]);
-}
-
 void
 Page_layout_problem::append_prob (Prob *prob, Spring const& spring, Real padding)
 {
   Skyline_pair *sky = Skyline_pair::unsmob (prob->get_property ("vertical-skylines"));
   Real minimum_distance = 0;
+  bool tight_spacing = to_boolean (prob->get_property ("tight-spacing"));
+
   if (sky)
     {
       minimum_distance = (*sky)[UP].distance (bottom_skyline_);
@@ -288,10 +278,17 @@ Page_layout_problem::append_prob (Prob *prob, Spring const& spring, Real padding
       bottom_skyline_.clear ();
       bottom_skyline_.set_minimum_height (iv[DOWN]);
     }
-  minimum_distance += padding;
 
   Spring spring_copy = spring;
-  spring_copy.ensure_min_distance (minimum_distance);
+  if (tight_spacing)
+    {
+      spring_copy.set_min_distance (minimum_distance);
+      spring_copy.set_inverse_stretch_strength (0.0);
+      spring_copy.set_distance (0.0);
+    }
+  else
+    spring_copy.ensure_min_distance (minimum_distance + padding);
+
   springs_.push_back (spring_copy);
   elements_.push_back (Element (prob));
 }
@@ -304,31 +301,12 @@ Page_layout_problem::solve_rod_spring_problem (bool ragged)
   for (vsize i = 0; i < springs_.size (); ++i)
     spacer.add_spring (springs_[i]);
 
-  Real bottom_padding = 0;
-  Interval first_staff_iv (0, 0);
-  Interval last_staff_iv (0, 0);
-  if (elements_.size ())
-    {
-      first_staff_iv = first_staff_extent (elements_[0]);
-      last_staff_iv = last_staff_extent (elements_.back ());
-
-      // TODO: junk bottom-space now that we have last-spring-spacing?
-      // bottom-space has the flexibility that one can do it per-system.
-      // NOTE: bottom-space is misnamed since it is not stretchable space.
-      if (Prob *p = elements_.back ().prob)
-       bottom_padding = robust_scm2double (p->get_property ("bottom-space"), 0);
-      else if (elements_.back ().staves.size ())
-       {
-         SCM details = get_details (elements_.back ());
-         bottom_padding = robust_scm2double (ly_assoc_get (ly_symbol2scm ("bottom-space"),
-                                                           details,
-                                                           SCM_BOOL_F),
-                                             0.0);
-       }
-    }
-
-  spacer.solve (page_height_ - bottom_padding, ragged);
+  spacer.solve (page_height_, ragged);
   solution_ = spacer.spring_positions ();
+
+  if (!spacer.fits ())
+    warning (_f ("couldn't fit music on page: overflow is %f",
+                spacer.configuration_length(spacer.force()) - page_height_));
 }
 
 // The solution_ vector stores the position of every live VerticalAxisGroup
@@ -344,12 +322,38 @@ Page_layout_problem::find_system_offsets ()
 
   // spring_idx 0 is the top of the page. Interesting values start from 1.
   vsize spring_idx = 1;
+  vector<Grob*> loose_lines;
+  vector<Real> loose_line_min_distances;
+  Grob *last_spaceable_line = 0;
+  Real last_spaceable_line_translation = 0;
+  Interval last_title_extent;
   for (vsize i = 0; i < elements_.size (); ++i)
     {
       if (elements_[i].prob)
        {
          *tail = scm_cons (scm_from_double (solution_[spring_idx]), SCM_EOL);
          tail = SCM_CDRLOC (*tail);
+         Interval prob_extent = unsmob_stencil (elements_[i].prob->get_property ("stencil"))->extent (Y_AXIS);
+
+         // Lay out any non-spaceable lines between this line and
+         // the last one.
+         if (loose_lines.size ())
+           {
+             Interval loose_extent = loose_lines.back ()->extent (loose_lines.back (), Y_AXIS);
+             Real min_distance = -loose_extent[DOWN] + prob_extent[UP]; // TODO: include padding/minimum-distance
+
+             loose_line_min_distances.push_back (min_distance);
+             loose_lines.push_back (0);
+
+             distribute_loose_lines (loose_lines, loose_line_min_distances,
+                                     last_spaceable_line_translation, -solution_[spring_idx]);
+             loose_lines.clear ();
+             loose_line_min_distances.clear ();
+           }
+
+         last_spaceable_line = 0;
+         last_spaceable_line_translation = -solution_[spring_idx];
+         last_title_extent = prob_extent;
          spring_idx++;
        }
       else
@@ -370,14 +374,12 @@ Page_layout_problem::find_system_offsets ()
 
          // Position the staves within this system.
          Real translation = 0;
-         vector<Grob*> loose_lines;
          vector<Real> const& min_offsets = elements_[i].min_offsets;
-         vector<Real> loose_line_min_distances;
-         Grob *last_spaceable_line = 0;
-         Real last_spaceable_line_translation = 0;
+         bool found_spaceable_staff = false;
          for (vsize staff_idx = 0; staff_idx < elements_[i].staves.size (); ++staff_idx)
            {
              Grob *staff = elements_[i].staves[staff_idx];
+             staff->set_property ("system-Y-offset", scm_from_double (-system_position));
 
              if (is_spaceable (staff))
                {
@@ -391,30 +393,52 @@ Page_layout_problem::find_system_offsets ()
                    {
                      loose_line_min_distances.push_back (min_offsets[staff_idx-1] - min_offsets[staff_idx]);
                      loose_lines.push_back (staff);
+
                      distribute_loose_lines (loose_lines, loose_line_min_distances,
-                                             last_spaceable_line_translation, translation);
+                                             last_spaceable_line_translation, translation - system_position);
                      loose_lines.clear ();
                      loose_line_min_distances.clear ();
                    }
                  last_spaceable_line = staff;
-                 last_spaceable_line_translation = translation;
+                 // Negative is down but the translation is relative to the whole page.
+                 last_spaceable_line_translation = -system_position + translation;
 
                  staff->translate_axis (translation, Y_AXIS);
+                 found_spaceable_staff = true;
                }
              else
                {
                  if (loose_lines.empty ())
                    loose_lines.push_back (last_spaceable_line);
 
+                 if (staff_idx)
+                   loose_line_min_distances.push_back (min_offsets[staff_idx-1] - min_offsets[staff_idx]);
+                 else
+                   {
+                     Real min_dist = 0;
+                     if (loose_lines.back ())
+                       min_dist = Axis_group_interface::minimum_distance (loose_lines.back (),
+                                                                          staff,
+                                                                          Y_AXIS);
+                     else if (!last_title_extent.is_empty ())
+                       { // distance to the preceding title
+                         // TODO: add options for controlling the space between a loose line
+                         // and a title/markup preceding it.
+                         min_dist = staff->extent (staff, Y_AXIS)[UP] - last_title_extent[DOWN];
+                       }
+                     else // distance to the top margin
+                       min_dist = header_padding_ + header_height_ + staff->extent (staff, Y_AXIS)[UP];
+
+                     loose_line_min_distances.push_back (min_dist);
+                   }
                  loose_lines.push_back (staff);
-                 loose_line_min_distances.push_back (min_offsets[staff_idx-1] - min_offsets[staff_idx]);
                }
            }
 
          // Corner case: even if a system has no live staves, it still takes up
          // one spring (a system with one live staff also takes up one spring),
          // which we need to increment past.
-         if (elements_[i].staves.empty ())
+         if (!found_spaceable_staff)
            spring_idx++;
 
          *tail = scm_cons (scm_from_double (system_position), SCM_EOL);
@@ -422,6 +446,18 @@ Page_layout_problem::find_system_offsets ()
        }
     }
 
+  if (loose_lines.size ())
+    {
+      Grob *last = loose_lines.back ();
+      Interval last_ext = last->extent (last, Y_AXIS);
+      loose_line_min_distances.push_back (-last_ext[DOWN] + footer_height_ + footer_padding_);
+      loose_lines.push_back (0);
+
+      distribute_loose_lines (loose_lines, loose_line_min_distances,
+                             last_spaceable_line_translation, -page_height_);
+
+    }
+
   assert (spring_idx == solution_.size () - 1);
   return system_offsets;
 }
@@ -429,6 +465,7 @@ Page_layout_problem::find_system_offsets ()
 // Given two lines that are already spaced (the first and last
 // elements of loose_lines), distribute some unspaced lines between
 // them.
+// first_translation and last_translation are relative to the page.
 void
 Page_layout_problem::distribute_loose_lines (vector<Grob*> const &loose_lines,
                                             vector<Real> const &min_distances,
@@ -437,18 +474,10 @@ Page_layout_problem::distribute_loose_lines (vector<Grob*> const &loose_lines,
   Simple_spacer spacer;
   for (vsize i = 0; i + 1 < loose_lines.size (); ++i)
     {
-      SCM spec = get_spacing_spec (loose_lines[i], loose_lines[i+1]);
+      SCM spec = get_spacing_spec (loose_lines[i], loose_lines[i+1], false, 0, INT_MAX);
       Spring spring (1.0, 0.0);
       alter_spring_from_spacing_spec (spec, &spring);
       spring.ensure_min_distance (min_distances[i]);
-
-      if (spec == SCM_BOOL_F)
-       {
-         // Insert a very flexible spring, so it doesn't have much effect.
-         spring.set_inverse_stretch_strength (100000);
-         spring.set_inverse_compress_strength (100000);
-       }
-
       spacer.add_spring (spring);
     }
 
@@ -457,7 +486,10 @@ Page_layout_problem::distribute_loose_lines (vector<Grob*> const &loose_lines,
 
   vector<Real> solution = spacer.spring_positions ();
   for (vsize i = 1; i + 1 < solution.size (); ++i)
-    loose_lines[i]->translate_axis (first_translation - solution[i], Y_AXIS);
+    {
+      Real system_offset = scm_to_double (loose_lines[i]->get_property ("system-Y-offset"));
+      loose_lines[i]->translate_axis (first_translation - solution[i] - system_offset, Y_AXIS);
+    }
 }
 
 SCM
@@ -487,7 +519,9 @@ Page_layout_problem::build_system_skyline (vector<Grob*> const& staves,
 
   assert (staves.size () == minimum_translations.size ());
   Real first_translation = minimum_translations[0];
-  Real last_dy = 0;
+  Real last_spaceable_dy = 0;
+  Real first_spaceable_dy = 0;
+  bool found_spaceable_staff = false;
 
   for (vsize i = 0; i < staves.size (); ++i)
     {
@@ -503,14 +537,25 @@ Page_layout_problem::build_system_skyline (vector<Grob*> const& staves,
          down->raise (-dy);
          down->merge ((*sky)[DOWN]);
          down->raise (dy);
-
-         last_dy = dy;
+       }
+      if (is_spaceable (staves[i]))
+       {
+         if (!found_spaceable_staff)
+           {
+             found_spaceable_staff = true;
+             first_spaceable_dy = dy;
+           }
+         last_spaceable_dy = dy;
        }
     }
 
+  // Leave the up skyline at a position relative
+  // to the top spaceable staff.
+  up->raise (-first_spaceable_dy);
+
   // Leave the down skyline at a position
-  // relative to the bottom staff.
-  down->raise (-last_dy);
+  // relative to the bottom spaceable staff.
+  down->raise (-last_spaceable_dy);
 }
 
 Interval
@@ -582,44 +627,109 @@ Page_layout_problem::read_spacing_spec (SCM spec, Real* dest, SCM sym)
   return false;
 }
 
-// Returns the spacing spec connecting BEFORE to AFTER.  A return
-// value of SCM_BOOL_F means that there should be no spring (in
-// practice, this means that we use a very flexible spring).
+// If there is a forced, fixed spacing between BEFORE and AFTER, return it.
+// Otherwise, return -infinity_f.
+// If after is spaceable, it is the (spaceable_index + 1)th spaceable grob in
+// its alignment.
+Real
+Page_layout_problem::get_fixed_spacing (Grob *before, Grob *after, int spaceable_index, bool pure, int start, int end)
+{
+  SCM spec = Page_layout_problem::get_spacing_spec (before, after, pure, start, end);
+  Real ret = -infinity_f;
+  Real stretchability = 0;
+  if (Page_layout_problem::read_spacing_spec (spec, &stretchability, ly_symbol2scm ("stretchability"))
+      && stretchability == 0)
+    Page_layout_problem::read_spacing_spec (spec, &ret, ly_symbol2scm ("space"));
+
+  // If we're pure, then paper-columns have not had their systems set,
+  // and so elts[i]->get_system () is unreliable.
+  System *sys = pure ? Grob::get_system (before) : before->get_system ();
+  Grob *left_bound = sys ? sys->get_maybe_pure_bound (LEFT, pure, start, end) : 0;
+
+  if (is_spaceable (before) && is_spaceable (after) && left_bound)
+    {
+      SCM details = left_bound->get_property ("line-break-system-details");
+      SCM manual_dists = ly_assoc_get (ly_symbol2scm ("alignment-distances"), details, SCM_EOL);
+      if (scm_is_pair (manual_dists))
+       {
+         SCM forced = robust_list_ref (spaceable_index - 1, manual_dists);
+         if (scm_is_number (forced))
+           ret = max (ret, scm_to_double (forced));
+       }
+    }
+  return ret;
+}
+
+static SCM
+add_stretchability (SCM alist, Real stretch)
+{
+  if (!scm_is_pair (scm_sloppy_assq (ly_symbol2scm ("stretchability"), alist)))
+    return scm_acons (ly_symbol2scm ("stretchability"), scm_from_double (stretch), alist);
+
+  return alist;
+}
+
+// We want to put a large stretch between a non-spaceable line and its
+// non-affinity staff. We want to put an even larger stretch between
+// a non-spaceable line and the top/bottom of the page. That way,
+// a spacing-affinity UP line at the bottom of the page will still be
+// placed close to its staff.
+const double LARGE_STRETCH = 10e5;
+const double HUGE_STRETCH = 10e7;
+
+// Returns the spacing spec connecting BEFORE to AFTER.
 SCM
-Page_layout_problem::get_spacing_spec (Grob *before, Grob *after)
+Page_layout_problem::get_spacing_spec (Grob *before, Grob *after, bool pure, int start, int end)
 {
+  // If there are no spacing wishes, return a very flexible spring.
+  // This will occur, for example, if there are lyrics at the bottom of
+  // the page, in which case we don't want the spring from the lyrics to
+  // the bottom of the page to have much effect.
+  if (!before || !after)
+    return add_stretchability (SCM_EOL, HUGE_STRETCH);
+
   if (is_spaceable (before))
     {
       if (is_spaceable (after))
-       return before->get_property ("next-staff-spacing");
+       return before->get_maybe_pure_property ("next-staff-spacing", pure, start, end);
       else
        {
-         Direction affinity = to_dir (after->get_property ("staff-affinity"));
-         return (affinity == DOWN) ? SCM_BOOL_F : after->get_property ("inter-staff-spacing");
+         Direction affinity = to_dir (after->get_maybe_pure_property ("staff-affinity", pure, start, end));
+         return (affinity == DOWN)
+           ? add_stretchability (after->get_maybe_pure_property ("non-affinity-spacing", pure, start, end),
+                                 LARGE_STRETCH)
+           : after->get_maybe_pure_property ("inter-staff-spacing", pure, start, end);
        }
     }
   else
     {
       if (is_spaceable (after))
        {
-         Direction affinity = to_dir (before->get_property ("staff-affinity"));
-         return (affinity == UP) ? SCM_BOOL_F : before->get_property ("inter-staff-spacing");
+         Direction affinity = to_dir (before->get_maybe_pure_property ("staff-affinity", pure, start, end));
+         return (affinity == UP)
+           ? add_stretchability (before->get_maybe_pure_property ("non-affinity-spacing", pure, start, end),
+                                 LARGE_STRETCH)
+           : before->get_maybe_pure_property ("inter-staff-spacing", pure, start, end);
        }
       else
        {
-         Direction before_affinity = to_dir (before->get_property ("staff-affinity"));
-         Direction after_affinity = to_dir (after->get_property ("staff-affinity"));
+         Direction before_affinity = to_dir (before->get_maybe_pure_property ("staff-affinity", pure, start, end));
+         Direction after_affinity = to_dir (after->get_maybe_pure_property ("staff-affinity", pure, start, end));
          if (after_affinity > before_affinity)
            {
              warning (_ ("staff-affinities should only decrease"));
              after_affinity = before_affinity;
            }
          if (before_affinity != UP)
-           return before->get_property ("inter-loose-line-spacing");
+           return before->get_maybe_pure_property ("inter-loose-line-spacing", pure, start, end);
          else if (after_affinity != DOWN)
-           return before->get_property ("inter-loose-line-spacing");
+           return before->get_maybe_pure_property ("inter-loose-line-spacing", pure, start, end);
+         return add_stretchability (before->get_maybe_pure_property ("non-affinity-spacing", pure, start, end),
+                                    LARGE_STRETCH);
        }
     }
+
+  assert (0);
   return SCM_BOOL_F;
 }