Fix bidirectional redisplay when deletion creates a paragraph start.

 src/insdel.c (invalidate_buffer_caches): When deleting or replacing
 text, invalidate the bidi_paragraph_cache upto and including the
 preceding newline.

2 files changed, 35 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index be4ce13129c..6b6bd06634a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2014-04-14  Eli Zaretskii  <eliz@gnu.org>
+
+        * insdel.c (invalidate_buffer_caches): When deleting or replacing
+        text, invalidate the bidi_paragraph_cache upto and including the
+        preceding newline.
+
 2014-04-13  Paul Eggert  <eggert@cs.ucla.edu>
 
         Port to IRIX 6.5 (Bug#9684).
diff --git a/src/insdel.c b/src/insdel.c
index 30b22ec7b26..ea5f6301501 100644
--- a/src/insdel.c
+++ b/src/insdel.c
@@ -1866,9 +1866,35 @@ invalidate_buffer_caches (struct buffer *buf, ptrdiff_t start, ptrdiff_t end)
                              buf->width_run_cache,
                              start - BUF_BEG (buf), BUF_Z (buf) - end);
   if (buf->bidi_paragraph_cache)
-    invalidate_region_cache (buf,
-                             buf->bidi_paragraph_cache,
-                             start - BUF_BEG (buf), BUF_Z (buf) - end);
+    {
+      if (start != end
+          && start > BUF_BEG (buf))
+        {
+          /* If we are deleting or replacing characters, we could
+             create a paragraph start, because all of the characters
+             from START to the beginning of START's line are
+             whitespace.  Therefore, we must extend the region to be
+             invalidated up to the newline before START.  */
+          ptrdiff_t line_beg = start;
+          ptrdiff_t start_byte = buf_charpos_to_bytepos (buf, start);
+
+          if (BUF_FETCH_BYTE (buf, start_byte - 1) != '\n')
+            {
+              struct buffer *old = current_buffer;
+
+              set_buffer_internal (buf);
+
+              line_beg = find_newline_no_quit (start, start_byte, -1,
+                                               &start_byte);
+              set_buffer_internal (old);
+            }
+          if (line_beg > BUF_BEG (buf))
+            start = line_beg - 1;
+        }
+      invalidate_region_cache (buf,
+                               buf->bidi_paragraph_cache,
+                               start - BUF_BEG (buf), BUF_Z (buf) - end);
+    }
 }
 
 /* These macros work with an argument named `preserve_ptr'