Use region cache to speedup bidi_find_paragraph_start.

* src/buffer.h (struct buffer): New member bidi_paragraph_cache.
Rename cache_long_line_scans to cache_long_scans.
* src/buffer.c (bset_cache_long_line_scans): Rename to
bset_cache_long_scans.
(Fget_buffer_create, Fmake_indirect_buffer, Fkill_buffer)
(Fbuffer_swap_text, init_buffer_once): Take bidi_paragraph_cache
into account.
(syms_of_buffer): Rename cache-long-line-scans to
cache-long-scans.  Adjust docstring.
* src/search.c (newline_cache_on_off):
* src/indent.c (width_run_cache_on_off): Adjust users.
* src/bidi.c (bidi_paragraph_cache_on_off): New function.
(bidi_find_paragraph_start): Use bidi_paragraph_cache if needed.
* src/insdel.c (prepare_to_modify_buffer): Invalidate
bidi_paragraph_cache if enabled.
* doc/lispref/positions.texi (Motion by Screen Lines):
* doc/lispref/display.texi (Truncation): Rename `cache-long-line-scans'
to `cache-long-scans'.

3 files changed, 9 insertions, 3 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index 82bc279fa5b..0aac5235a29 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,9 @@
+2013-08-06  Dmitry Antipov  <dmantipov@yandex.ru>
+
+        * positions.texi (Motion by Screen Lines):
+        * display.texi (Truncation): Rename `cache-long-line-scans'
+        to `cache-long-scans'.
+
 2013-08-05  Xue Fuqiao  <xfq.free@gmail.com>
 
         * windows.texi (Window Start and End): Add an index.
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index c5068425c66..59a6f5ce340 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -217,9 +217,9 @@ over the @code{line-prefix} variable.  @xref{Special Properties}.
 continuation to display them, computing the continuation lines can
 make redisplay slow.  The column computation and indentation functions
 also become slow.  Then you might find it advisable to set
-@code{cache-long-line-scans} to @code{t}.
+@code{cache-long-scans} to @code{t}.
 
-@defvar cache-long-line-scans
+@defvar cache-long-scans
 If this variable is non-@code{nil}, various indentation and motion
 functions, and Emacs redisplay, cache the results of scanning the
 buffer, and consult the cache to avoid rescanning regions of the buffer
diff --git a/doc/lispref/positions.texi b/doc/lispref/positions.texi
index e8b6166f63c..119ad98a53d 100644
--- a/doc/lispref/positions.texi
+++ b/doc/lispref/positions.texi
@@ -483,7 +483,7 @@ Display}.
   These functions scan text to determine where screen lines break, and
 thus take time proportional to the distance scanned.  If you intend to
 use them heavily, Emacs provides caches which may improve the
-performance of your code.  @xref{Truncation, cache-long-line-scans}.
+performance of your code.  @xref{Truncation, cache-long-scans}.
 
 @defun vertical-motion count &optional window
 This function moves point to the start of the screen line @var{count}