Fix bug #9771 with slow redisplay in long lines full of control characters.

 src/bidi.c (bidi_line_init): Initialize next_en_pos to zero, not -1.
 (bidi_resolve_neutral): Don't enter the expensive loop looking for
 non-neutral characters if the current character is a paragraph
 separator (a.k.a. Newline).  This avoids running the same
 expensive loop twice, once when we consume the preceding newline
 and the other time when the line actually needs to be displayed.
 Avoid the loop when we see neutrals on the base embedding level
 following a character whose directionality is the same as the
 paragraph's.  This avoids running the expensive loop when a line
 ends in a long sequence of neutrals, like control characters.
 Add assertion against STRONG_AL type.  Slightly rearrange code
 that determines the type of a neutral given the first non-neutral
 that follows it.
 (bidi_level_of_next_char): Set next_en_pos to zero when
 invalidating its info.

1 files changed, 19 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 07b0418b399..d21e6383764 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,22 @@
+2011-10-18  Eli Zaretskii  <eliz@gnu.org>
+
+        Fix part 3 of bug#9771.
+        * bidi.c (bidi_line_init): Initialize next_en_pos to zero, not -1.
+        (bidi_resolve_neutral): Don't enter the expensive loop looking for
+        non-neutral characters if the current character is a paragraph
+        separator (a.k.a. Newline).  This avoids running the same
+        expensive loop twice, once when we consume the preceding newline
+        and the other time when the line actually needs to be displayed.
+        Avoid the loop when we see neutrals on the base embedding level
+        following a character whose directionality is the same as the
+        paragraph's.  This avoids running the expensive loop when a line
+        ends in a long sequence of neutrals, like control characters.
+        Add assertion against STRONG_AL type.  Slightly rearrange code
+        that determines the type of a neutral given the first non-neutral
+        that follows it.
+        (bidi_level_of_next_char): Set next_en_pos to zero when
+        invalidating its info.
+
 2011-10-17  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (push_display_prop): Determine whether to record string