Improve locked narrowing around low-level hooks.

* src/buffer.c (syms_of_buffer): Two new variables,
'long-line-locked-narrowing-region-size' and
'long-line-locked-narrowing-bol-search-limit', to make the locked
narrowing around low-level hooks configurable.

Increase the default value of 'long-line-threshold'.  After
carefully considering the (few) bug reports about long line
optimizations, I concluded that the previous default value was too
low.

* src/xdisp.c (get_locked_narrowing_begv)
(get_locked_narrowing_zv): Two new functions.
(handle_fontified_prop, reseat): Use them.

* src/keyboard.c (safe_run_hooks_maybe_narrowed): Use them.

* src/dispextern.h (struct it): Add two new fields to store the
values returned by these functions.
Make them externally visible.

* src/editfns.c: (Fsave_restriction): Update docstring.

1 files changed, 6 insertions, 5 deletions

diff --git a/src/editfns.c b/src/editfns.c
index f73331fb53c..e6b66209b8b 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -2659,7 +2659,7 @@ DEFUN ("delete-and-extract-region", Fdelete_and_extract_region,
    the (uninterned) Qoutermost_narrowing tag and records the narrowing
    bounds that were set by the user and that are visible on display.
    This alist is used internally by narrow-to-region, widen,
-   narrowing-lock and narrowing-unlock.  */
+   narrowing-lock, narrowing-unlock and save-restriction.  */
 static Lisp_Object narrowing_locks;
 
 /* Retrieve one of the BEGV/ZV bounds of a narrowing in BUF from the
@@ -3061,11 +3061,12 @@ DEFUN ("save-restriction", Fsave_restriction, Ssave_restriction, 0, UNEVALLED, 0
        doc: /* Execute BODY, saving and restoring current buffer's restrictions.
 The buffer's restrictions make parts of the beginning and end invisible.
 \(They are set up with `narrow-to-region' and eliminated with `widen'.)
-This special form, `save-restriction', saves the current buffer's restrictions
-when it is entered, and restores them when it is exited.
+This special form, `save-restriction', saves the current buffer's
+restrictions, as well as their locks if they have been locked with
+`narrowing-lock', when it is entered, and restores them when it is exited.
 So any `narrow-to-region' within BODY lasts only until the end of the form.
-The old restrictions settings are restored
-even in case of abnormal exit (throw or error).
+The old restrictions settings are restored even in case of abnormal exit
+\(throw or error).
 
 The value returned is the value of the last form in BODY.