Fix parts 1 & 2 of bug #10183 with RTL headings in Org mode.

 src/xdisp.c (handle_invisible_prop): If the invisible text ends just
 before a newline, prepare the bidi iterator for consuming the
 newline, and keep the current paragraph direction.

2 files changed, 37 insertions, 20 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index ed47da2caa1..efba68d99d6 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2011-12-03  Eli Zaretskii  <eliz@gnu.org>
+
+        * xdisp.c (handle_invisible_prop): If the invisible text ends just
+        before a newline, prepare the bidi iterator for consuming the
+        newline, and keep the current paragraph direction.  (Bug#10183)
+
 2011-12-02  Juri Linkov  <juri@jurta.org>
 
         * search.c (Fword_search_regexp): New Lisp function created from
diff --git a/src/xdisp.c b/src/xdisp.c
index c9b9b5c5e88..b9741d97d30 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4093,26 +4093,37 @@ handle_invisible_prop (struct it *it)
           if (it->bidi_p && newpos < ZV)
             {
               EMACS_INT bpos = CHAR_TO_BYTE (newpos);
-
-              if (FETCH_BYTE (bpos) == '\n'
-                  || (newpos > BEGV && FETCH_BYTE (bpos - 1) == '\n'))
+              int on_newline = FETCH_BYTE (bpos) == '\n';
+              int after_newline =
+                newpos <= BEGV || FETCH_BYTE (bpos - 1) == '\n';
+
+              /* If the invisible text ends on a newline or on a
+                 character after a newline, we can avoid the costly,
+                 character by character, bidi iteration to NEWPOS, and
+                 instead simply reseat the iterator there.  That's
+                 because all bidi reordering information is tossed at
+                 the newline.  This is a big win for modes that hide
+                 complete lines, like Outline, Org, etc.  */
+              if (on_newline || after_newline)
                 {
-                  /* If the invisible text ends on a newline or the
-                     character after a newline, we can avoid the
-                     costly, character by character, bidi iteration to
-                     newpos, and instead simply reseat the iterator
-                     there.  That's because all bidi reordering
-                     information is tossed at the newline.  This is a
-                     big win for modes that hide complete lines, like
-                     Outline, Org, etc.  (Implementation note: the
-                     call to reseat_1 is necessary, because it signals
-                     to the bidi iterator that it needs to reinit its
-                     internal information when the next element for
-                     display is requested.  */
                   struct text_pos tpos;
+                  bidi_dir_t pdir = it->bidi_it.paragraph_dir;
 
                   SET_TEXT_POS (tpos, newpos, bpos);
                   reseat_1 (it, tpos, 0);
+                  /* If we reseat on a newline, we need to prep the
+                     bidi iterator for advancing to the next character
+                     after the newline, keeping the current paragraph
+                     direction (so that PRODUCE_GLYPHS does TRT wrt
+                     prepending/appending glyphs to a glyph row).  */
+                  if (on_newline)
+                    {
+                      it->bidi_it.first_elt = 0;
+                      it->bidi_it.paragraph_dir = pdir;
+                      it->bidi_it.ch = '\n';
+                      it->bidi_it.nchars = 1;
+                      it->bidi_it.ch_len = 1;
+                    }
                 }
               else      /* Must use the slow method.  */
                 {
@@ -4121,11 +4132,11 @@ handle_invisible_prop (struct it *it)
                      non-base embedding level.  Therefore, we need to
                      skip invisible text using the bidi iterator,
                      starting at IT's current position, until we find
-                     ourselves outside the invisible text.  Skipping
-                     invisible text _after_ bidi iteration avoids
-                     affecting the visual order of the displayed text
-                     when invisible properties are added or
-                     removed.  */
+                     ourselves outside of the invisible text.
+                     Skipping invisible text _after_ bidi iteration
+                     avoids affecting the visual order of the
+                     displayed text when invisible properties are
+                     added or removed.  */
                   if (it->bidi_it.first_elt && it->bidi_it.charpos < ZV)
                     {
                       /* If we were `reseat'ed to a new paragraph,