Retrospective commit from 2009-1219.

Fix reordering of Arabic text in etc/HELLO.
Extend .gdbinit commands to support bidirectional display.

 buffer.c (Fbuffer_swap_text): Swap the values of
 bidi_display_reordering and bidi_paragraph_direction.

 bidi.c (bidi_resolve_weak): Fix nesting of conditions for Wn
 processing.  Move W3 after W1 and W2.  Simplify W4 because it is
 now always after W1.

 .gdbinit (pbiditype): New command.
 (pgx): Use it to display bidi level and type of the glyph.

4 files changed, 141 insertions, 97 deletions

diff --git a/src/.gdbinit b/src/.gdbinit
index e8a64f5dfe4..61e3da6c68c 100644
--- a/src/.gdbinit
+++ b/src/.gdbinit
@@ -447,6 +447,33 @@ document pwin
 Pretty print window structure w.
 end
 
+define pbiditype
+  if ($arg0 == 1)
+    printf "L"
+  end
+  if ($arg0 == 2)
+    printf "R"
+  end
+  if ($arg0 == 3)
+    printf "EN"
+  end
+  if ($arg0 == 4)
+    printf "AN"
+  end
+  if ($arg0 == 5)
+    printf "BN"
+  end
+  if ($arg0 == 6)
+    printf "B"
+  end
+  if ($arg0 < 1 || $arg0 > 6)
+    printf "%d??", $arg0
+  end
+end
+document pbiditype
+Print textual description of bidi type given as first argument.
+end
+
 define pgx
   set $g = $arg0
   # CHAR_GLYPH
@@ -475,6 +502,11 @@ define pgx
   else
     printf " pos=%d", $g->charpos
   end
+  # For characters, print their resolved level and bidi type
+  if ($g->type == 0)
+    printf " blev=%d,btyp=", $g->resolved_level
+    pbiditype $g->bidi_type
+  end
   printf " w=%d a+d=%d+%d", $g->pixel_width, $g->ascent, $g->descent
   # If not DEFAULT_FACE_ID
   if ($g->face_id != 0)
diff --git a/src/ChangeLog.bidi b/src/ChangeLog.bidi
index ef911354df8..b9fb7457cfd 100644
--- a/src/ChangeLog.bidi
+++ b/src/ChangeLog.bidi
@@ -1,3 +1,15 @@
+2009-12-19  Eli Zaretskii  <eliz@gnu.org>
+
+        * buffer.c (Fbuffer_swap_text): Swap the values of
+        bidi_display_reordering and bidi_paragraph_direction.
+
+        * bidi.c (bidi_resolve_weak): Fix nesting of conditions for Wn
+        processing.  Move W3 after W1 and W2.  Simplify W4 because it is
+        now always after W1.
+
+        * .gdbinit (pbiditype): New command.
+        (pgx): Use it to display bidi level and type of the glyph.
+
 2009-12-12  Eli Zaretskii  <eliz@gnu.org>
 
         * dispextern.h (struct it): New members prev_stop and
diff --git a/src/bidi.c b/src/bidi.c
index 102326b41e8..d18629279d6 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -1342,123 +1342,121 @@ bidi_resolve_weak (struct bidi_it *bidi_it)
     type = STRONG_R;
   else if (override == L2R)
     type = STRONG_L;
-  else if (type == STRONG_AL)
-    type = STRONG_R;            /* W3 */
-  else if (type == WEAK_NSM)    /* W1 */
-    {
-      /* Note that we don't need to consider the case where the prev
-         character has its type overridden by an RLO or LRO: such
-         characters are outside the current level run, and thus not
-         relevant to this NSM.  Thus, NSM gets the orig_type of the
-         previous character.  */
-      if (bidi_it->prev.type != UNKNOWN_BT)
-        type = bidi_it->prev.orig_type;
-      else if (bidi_it->sor == R2L)
-        type = STRONG_R;
-      else if (bidi_it->sor == L2R)
-        type = STRONG_L;
-      else /* shouldn't happen! */
-        abort ();
-      if (type == WEAK_EN       /* W2 after W1 */
-          && bidi_it->last_strong.type_after_w1 == STRONG_AL)
-        type = WEAK_AN;
-    }
-  else if (type == WEAK_EN      /* W2 */
-           && bidi_it->last_strong.type_after_w1 == STRONG_AL)
-    type = WEAK_AN;
-  else if ((type == WEAK_ES
-            && (bidi_it->prev.type_after_w1 == WEAK_EN           /* W4 */
-                && (bidi_it->prev.orig_type == WEAK_EN
-                    || bidi_it->prev.orig_type == WEAK_NSM)))    /* aft W1 */
-           || (type == WEAK_CS
-               && ((bidi_it->prev.type_after_w1 == WEAK_EN
-                    && (bidi_it->prev.orig_type == WEAK_EN       /* W4 */
-                        || bidi_it->prev.orig_type == WEAK_NSM)) /* a/W1 */
-                   || bidi_it->prev.type_after_w1 == WEAK_AN)))  /* W4 */
+  else
     {
-      next_char =
-        bidi_it->bytepos + bidi_it->ch_len >= ZV_BYTE
-        ? BIDI_EOB : FETCH_CHAR (bidi_it->bytepos + bidi_it->ch_len);
-      type_of_next = bidi_get_type (next_char, override);
-
-      if (type_of_next == WEAK_BN
-          || bidi_explicit_dir_char (next_char))
+      if (type == WEAK_NSM)     /* W1 */
         {
-          bidi_copy_it (&saved_it, bidi_it);
-          while (bidi_resolve_explicit (bidi_it) == new_level
-                 && bidi_it->type == WEAK_BN)
-            ;
-          type_of_next = bidi_it->type;
-          bidi_copy_it (bidi_it, &saved_it);
-        }
-
-      /* If the next character is EN, but the last strong-type
-         character is AL, that next EN will be changed to AN when we
-         process it in W2 above.  So in that case, this ES should not
-         be changed into EN.  */
-      if (type == WEAK_ES
-          && type_of_next == WEAK_EN
-          && bidi_it->last_strong.type_after_w1 != STRONG_AL)
-        type = WEAK_EN;
-      else if (type == WEAK_CS)
-        {
-          if (bidi_it->prev.type_after_w1 == WEAK_AN
-              && (type_of_next == WEAK_AN
-                  /* If the next character is EN, but the last
-                     strong-type character is AL, EN will be later
-                     changed to AN when we process it in W2 above.  So
-                     in that case, this ES should not be changed into
-                     EN.  */
-                  || (type_of_next == WEAK_EN
-                      && bidi_it->last_strong.type_after_w1 == STRONG_AL)))
-            type = WEAK_AN;
-          else if (bidi_it->prev.type_after_w1 == WEAK_EN
-                   && type_of_next == WEAK_EN
-                   && bidi_it->last_strong.type_after_w1 != STRONG_AL)
-            type = WEAK_EN;
+          /* Note that we don't need to consider the case where the
+             prev character has its type overridden by an RLO or LRO:
+             such characters are outside the current level run, and
+             thus not relevant to this NSM.  Thus, NSM gets the
+             orig_type of the previous character.  */
+          if (bidi_it->prev.type != UNKNOWN_BT)
+            type = bidi_it->prev.orig_type;
+          else if (bidi_it->sor == R2L)
+            type = STRONG_R;
+          else if (bidi_it->sor == L2R)
+            type = STRONG_L;
+          else /* shouldn't happen! */
+            abort ();
         }
-    }
-  else if (type == WEAK_ET      /* W5: ET with EN before or after it */
-           || type == WEAK_BN)  /* W5/Retaining */
-    {
-      if (bidi_it->prev.type_after_w1 == WEAK_EN /* ET/BN with EN before it */
-          || bidi_it->next_en_pos > bidi_it->charpos)
-        type = WEAK_EN;
-      /* W5: ET with EN after it.  */
-      else
+      if (type == WEAK_EN       /* W2 */
+          && bidi_it->last_strong.type_after_w1 == STRONG_AL)
+        type = WEAK_AN;
+      else if (type == STRONG_AL) /* W3 */
+        type = STRONG_R;
+      else if ((type == WEAK_ES /* W4 */
+                && bidi_it->prev.type_after_w1 == WEAK_EN
+                && bidi_it->prev.orig_type == WEAK_EN)
+               || (type == WEAK_CS
+                   && ((bidi_it->prev.type_after_w1 == WEAK_EN
+                        && bidi_it->prev.orig_type == WEAK_EN)
+                       || bidi_it->prev.type_after_w1 == WEAK_AN)))
         {
-          EMACS_INT en_pos = bidi_it->charpos + 1;
-
           next_char =
             bidi_it->bytepos + bidi_it->ch_len >= ZV_BYTE
             ? BIDI_EOB : FETCH_CHAR (bidi_it->bytepos + bidi_it->ch_len);
           type_of_next = bidi_get_type (next_char, override);
 
-          if (type_of_next == WEAK_ET
-              || type_of_next == WEAK_BN
+          if (type_of_next == WEAK_BN
               || bidi_explicit_dir_char (next_char))
             {
               bidi_copy_it (&saved_it, bidi_it);
               while (bidi_resolve_explicit (bidi_it) == new_level
-                     && (bidi_it->type == WEAK_BN || bidi_it->type == WEAK_ET))
+                     && bidi_it->type == WEAK_BN)
                 ;
               type_of_next = bidi_it->type;
-              en_pos = bidi_it->charpos;
               bidi_copy_it (bidi_it, &saved_it);
             }
-          if (type_of_next == WEAK_EN)
+
+          /* If the next character is EN, but the last strong-type
+             character is AL, that next EN will be changed to AN when
+             we process it in W2 above.  So in that case, this ES
+             should not be changed into EN.  */
+          if (type == WEAK_ES
+              && type_of_next == WEAK_EN
+              && bidi_it->last_strong.type_after_w1 != STRONG_AL)
+            type = WEAK_EN;
+          else if (type == WEAK_CS)
             {
-              /* If the last strong character is AL, the EN we've
-                 found will become AN when we get to it (W2). */
-              if (bidi_it->last_strong.type_after_w1 != STRONG_AL)
+              if (bidi_it->prev.type_after_w1 == WEAK_AN
+                  && (type_of_next == WEAK_AN
+                      /* If the next character is EN, but the last
+                         strong-type character is AL, EN will be later
+                         changed to AN when we process it in W2 above.
+                         So in that case, this ES should not be
+                         changed into EN.  */
+                      || (type_of_next == WEAK_EN
+                          && bidi_it->last_strong.type_after_w1 == STRONG_AL)))
+                type = WEAK_AN;
+              else if (bidi_it->prev.type_after_w1 == WEAK_EN
+                       && type_of_next == WEAK_EN
+                       && bidi_it->last_strong.type_after_w1 != STRONG_AL)
+                type = WEAK_EN;
+            }
+        }
+      else if (type == WEAK_ET  /* W5: ET with EN before or after it */
+               || type == WEAK_BN)      /* W5/Retaining */
+        {
+          if (bidi_it->prev.type_after_w1 == WEAK_EN /* ET/BN w/EN before it */
+              || bidi_it->next_en_pos > bidi_it->charpos)
+            type = WEAK_EN;
+          else                  /* W5: ET/BN with EN after it.  */
+            {
+              EMACS_INT en_pos = bidi_it->charpos + 1;
+
+              next_char =
+                bidi_it->bytepos + bidi_it->ch_len >= ZV_BYTE
+                ? BIDI_EOB : FETCH_CHAR (bidi_it->bytepos + bidi_it->ch_len);
+              type_of_next = bidi_get_type (next_char, override);
+
+              if (type_of_next == WEAK_ET
+                  || type_of_next == WEAK_BN
+                  || bidi_explicit_dir_char (next_char))
+                {
+                  bidi_copy_it (&saved_it, bidi_it);
+                  while (bidi_resolve_explicit (bidi_it) == new_level
+                         && (bidi_it->type == WEAK_BN
+                             || bidi_it->type == WEAK_ET))
+                    ;
+                  type_of_next = bidi_it->type;
+                  en_pos = bidi_it->charpos;
+                  bidi_copy_it (bidi_it, &saved_it);
+                }
+              if (type_of_next == WEAK_EN)
                 {
-                  type = WEAK_EN;
-                  /* Remember this EN position, to speed up processing
-                     of the next ETs.  */
-                  bidi_it->next_en_pos = en_pos;
+                  /* If the last strong character is AL, the EN we've
+                     found will become AN when we get to it (W2). */
+                  if (bidi_it->last_strong.type_after_w1 != STRONG_AL)
+                    {
+                      type = WEAK_EN;
+                      /* Remember this EN position, to speed up processing
+                         of the next ETs.  */
+                      bidi_it->next_en_pos = en_pos;
+                    }
+                  else if (type == WEAK_BN)
+                    type = NEUTRAL_ON; /* W6/Retaining */
                 }
-              else if (type == WEAK_BN)
-                type = NEUTRAL_ON; /* W6/Retaining */
             }
         }
     }
diff --git a/src/buffer.c b/src/buffer.c
index 521fe9b5019..ce9dc1c274d 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2261,6 +2261,8 @@ DEFUN ("buffer-swap-text", Fbuffer_swap_text, Sbuffer_swap_text,
   swapfield (undo_list, Lisp_Object);
   swapfield (mark, Lisp_Object);
   swapfield (enable_multibyte_characters, Lisp_Object);
+  swapfield (bidi_display_reordering, Lisp_Object);
+  swapfield (bidi_paragraph_direction, Lisp_Object);
   /* FIXME: Not sure what we should do with these *_marker fields.
      Hopefully they're just nil anyway.  */
   swapfield (pt_marker, Lisp_Object);