Cache page-height during page breaking.

diff --git a/lily/include/page-breaking.hh b/lily/include/page-breaking.hh
index 58c8de0951a93d82b208b15901a01ff0d36081c1..d34534c1ca4eb462b6c1fb9ff4f1bd8ce270d10e 100644 (file)
--- a/lily/include/page-breaking.hh
+++ b/lily/include/page-breaking.hh
@@ -196,6 +196,9 @@ private:
   vector<Line_details> cached_line_details_;
   vector<Line_details> uncompressed_line_details_;
 
+  mutable vector<Real> page_height_cache_;
+  mutable vector<Real> last_page_height_cache_;
+
   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,

diff --git a/lily/page-breaking.cc b/lily/page-breaking.cc
index d22e999a7f1c0e11aa03cc1340f5eba7da880278..4ac005461c68d66a5e187b8f58138c7a371423f0 100644 (file)
--- a/lily/page-breaking.cc
+++ b/lily/page-breaking.cc
@@ -368,13 +368,33 @@ Page_breaking::make_page (int page_num, bool last) const
 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");
-  calc_height = scm_variable_ref (calc_height);
+  // The caches allow us to store the page heights for any
+  // non-negative page numbers.  We use a negative value in the
+  // cache to signal that that position has not yet been initialized.
+  // This means that we won't cache properly if page_num is negative or
+  // if calc_height returns a negative number.  But that's likely to
+  // be rare, so it shouldn't affect performance.
+  vector<Real>& cache = last ? last_page_height_cache_ : page_height_cache_;
+  if (page_num >= 0 && (int) cache.size () > page_num && cache[page_num] >= 0)
+    return cache[page_num];
+  else
+    {
+      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");
+      calc_height = scm_variable_ref (calc_height);
 
-  SCM height = scm_apply_1 (calc_height, page, SCM_EOL);
-  return scm_to_double (height);
+      SCM height_scm = scm_apply_1 (calc_height, page, SCM_EOL);
+      Real height = scm_to_double (height_scm);
+
+      if (page_num >= 0)
+       {
+         if ((int) cache.size () <= page_num)
+           cache.resize (page_num + 1, -1);
+         cache[page_num] = height;
+       }
+      return height;
+    }
 }
 
 SCM