Fix bug #9470 with slow redisplay in huge single-paragraph buffers.

 src/bidi.c (MAX_PARAGRAPH_SEARCH): New macro.
 (bidi_find_paragraph_start): Search back for paragraph beginning
 at most MAX_PARAGRAPH_SEARCH lines; if not found, return BEGV_BYTE.
 (bidi_move_to_visually_next): Only trigger paragraph-related
 computations when the last character is a newline or at EOB, not
 just any NEUTRAL_B.
 src/xdisp.c (reseat_at_next_visible_line_start): Keep information
 about the current paragraph and restore it after the call to
 reseat.

1 files changed, 11 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d09c970bc03..a6d890cd149 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,16 @@
 2011-09-17  Eli Zaretskii  <eliz@gnu.org>
 
+        * xdisp.c (reseat_at_next_visible_line_start): Keep information
+        about the current paragraph and restore it after the call to
+        reseat.
+
+        * bidi.c (MAX_PARAGRAPH_SEARCH): New macro.
+        (bidi_find_paragraph_start): Search back for paragraph beginning
+        at most MAX_PARAGRAPH_SEARCH lines; if not found, return BEGV_BYTE.
+        (bidi_move_to_visually_next): Only trigger paragraph-related
+        computations when the last character is a newline or at EOB, not
+        just any NEUTRAL_B.  (Bug#9470)
+
         * xdisp.c (set_cursor_from_row): Don't invoke special treatment of
         truncated lines if point is covered by a display string.  (Bug#9524)