Doc changes for cache-long-scans

Ref: http://debbugs.gnu.org/15797#65

* doc/lispref/display.texi (Truncation):
* doc/lispref/positions.texi (Screen Lines): Do not mention cache-long-scans.

* src/buffer.c (cache-long-scans): Doc fix.

* etc/NEWS: Related edit.

6 files changed, 20 insertions, 5 deletions

diff --git a/doc/lispref/ChangeLog b/doc/lispref/ChangeLog
index b38256a4492..eff328caa60 100644
--- a/doc/lispref/ChangeLog
+++ b/doc/lispref/ChangeLog
@@ -1,3 +1,8 @@
+2014-02-06  Glenn Morris  <rgm@gnu.org>
+
+        * display.texi (Truncation):
+        * positions.texi (Screen Lines): Do not mention cache-long-scans.
+
 2014-01-31  Juri Linkov  <juri@jurta.org>
 
         * searching.texi (String Search): Incremental word search fixes.
diff --git a/doc/lispref/display.texi b/doc/lispref/display.texi
index 9123e940e08..7d52ad7207b 100644
--- a/doc/lispref/display.texi
+++ b/doc/lispref/display.texi
@@ -214,6 +214,7 @@ A line prefix may also be specified for regions of text using the
 over the @code{line-prefix} variable.  @xref{Special Properties}.
 @end defvar
 
+@ignore
   If your buffer contains only very short lines, you might find it
 advisable to set @code{cache-long-scans} to @code{nil}.
 
@@ -227,6 +228,7 @@ Turning off the cache speeds up processing of short lines somewhat.
 
 This variable is automatically buffer-local in every buffer.
 @end defvar
+@end ignore
 
 @node The Echo Area
 @section The Echo Area
diff --git a/doc/lispref/positions.texi b/doc/lispref/positions.texi
index 9a9152b4044..f83173e2038 100644
--- a/doc/lispref/positions.texi
+++ b/doc/lispref/positions.texi
@@ -486,9 +486,11 @@ flag, and display table may vary between windows).  @xref{Usual
 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-scans}.
+thus take time proportional to the distance scanned.
+@ignore
+If you intend to use them heavily, Emacs provides caches which may
+improve the performance of your code.  @xref{Truncation, cache-long-scans}.
+@end ignore
 
 @defun vertical-motion count &optional window
 This function moves point to the start of the screen line @var{count}
diff --git a/etc/NEWS b/etc/NEWS
index 7f58284d978..ea2287e0f5e 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -240,9 +240,9 @@ to be printed in other formats (octal, hexadecimal, and character).
 ** `write-region-inhibit-fsync' now defaults to t in batch mode.
 
 +++
-** `cache-long-line-scans' has been renamed to `cache-long-scans'
+** `cache-long-line-scans' is now non-nil, and renamed to `cache-long-scans',
 because it affects caching of paragraph scanning results as well.
-Also, it is now enabled by default.
+There is no reason to set this to nil except for debugging purposes.
 
 ---
 ** The option `set-mark-default-inactive' has been deleted.
diff --git a/src/ChangeLog b/src/ChangeLog
index 2df6c99edc1..925cb4625a2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,7 @@
+2014-02-06  Glenn Morris  <rgm@gnu.org>
+
+        * buffer.c (cache-long-scans): Doc fix.
+
 2014-02-05  Eli Zaretskii  <eliz@gnu.org>
 
         * w32fns.c (Fw32_shell_execute): Doc fix.
diff --git a/src/buffer.c b/src/buffer.c
index 33bd80d3f4f..cbf7291e3c8 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -6130,6 +6130,8 @@ If the value of the variable is t, undo information is not recorded.  */);
   DEFVAR_PER_BUFFER ("cache-long-scans", &BVAR (current_buffer, cache_long_scans), Qnil,
                      doc: /* Non-nil means that Emacs should use caches in attempt to speedup buffer scans.
 
+There is no reason to set this to nil except for debugging purposes.
+
 Normally, the line-motion functions work by scanning the buffer for
 newlines.  Columnar operations (like `move-to-column' and
 `compute-motion') also work by scanning the buffer, summing character