Retrospective commit.

These are the original changes made by Kenichi Handa on the old
pre Emacs 22 emacs-bidi branch.

src/ChangeLog.bidi

+2005-12-03  Eli Zaretskii  <eliz@gnu.org>
+
+	* bidi.c: Include stdio.h unconditionally.  Fix and elaborate
+	commentary.  Add Copyright blurb.
+
+2004-03-08  Kenichi Handa  <handa@m17n.org>
+
+	* xdisp.c (reseat_1): Call bidi_init_it with a previous position.
+
+	* bidi.c (bidi_init_it): Set bidi_it->ch_len even if POS > 0.
+
+2004-03-04  Kenichi Handa  <handa@m17n.org>
+
+	The following changes are to support bidirectional text display.
+
+	* Makefile.in (obj): Include bidi.o.
+	(bidi.o): New target.
+
+	* bidi.c: New file.
+
+	* buffer.h (struct buffer): New member bidi_display_reordering.
+
+	* buffer.c (init_buffer_once): Initialize bidi_display_reordering.
+	(syms_of_buffer): Declarations of Lisp variables
+	default-bidi-display-reordering and bidi-display-reordering.
+
+	* dispextern.h (BIDI_MAXLEVEL): New macro.
+	(bidi_type_t, bidi_dir_t): New types.
+	(bidi_saved_info, bidi_stack, bidi_it): New structs.
+	(struct it): New members bidi_p and bidi_it.
+	(bidi_init_it): Extern it.
+	(bidi_get_next_char_visually): Extern it.
+
+	* dispnew.c (direct_output_forward_char): Give up if we need bidi
+	processing or buffer's direction is right-to-left.
+
+	* xdisp.c (init_iterator): Initialize it->bidi_p.
+	(reseat_1): Cal bidi_init_it and bidi_get_next_char_visually if
+	necessary.
+	(set_iterator_to_next): Cal bidi_get_next_char_visually if
+	necessary.
+
+
+;; Local Variables:
+;; coding: utf-8
+;; add-log-time-zone-rule: t
+;; End:
+
+    Copyright (C) 2007, 2008, 2009  Free Software Foundation, Inc.
+
+  This file is part of GNU Emacs.
+
+  GNU Emacs is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 3 of the License, or
+  (at your option) any later version.
+
+  GNU Emacs is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.

src/Makefile.in

@@ -560,6 +560,7 @@ FONT_DRIVERS = xfont.o
 /* lastfile must follow all files
    whose initialized data areas should be dumped as pure by dump-emacs.  */
 obj=    dispnew.o frame.o scroll.o xdisp.o menu.o $(XMENU_OBJ) window.o \
+	bidi.o \
 	charset.o coding.o category.o ccl.o character.o chartab.o \
 	cm.o term.o terminal.o xfaces.o $(XOBJ) $(GTK_OBJ) $(DBUS_OBJ) \
 	emacs.o keyboard.o macros.o keymap.o sysdep.o \
@@ -1052,6 +1053,7 @@ doc.o: buildobj.h
 
 atimer.o: atimer.c atimer.h syssignal.h systime.h lisp.h blockinput.h \
  $(config_h)
+bidi.o: bidi.c buffer.h character.h
 buffer.o: buffer.c buffer.h region-cache.h commands.h window.h \
    $(INTERVALS_H) blockinput.h atimer.h systime.h character.h \
    indent.h keyboard.h coding.h keymap.h frame.h lisp.h $(config_h)

src/buffer.c

@@ -5186,7 +5186,8 @@ init_buffer_once ()
   buffer_defaults.truncate_lines = Qnil;
   buffer_defaults.word_wrap = Qnil;
   buffer_defaults.ctl_arrow = Qt;
-  buffer_defaults.direction_reversed = Qnil;
+  buffer_defaults.enable_bidi_display = Qnil;
+  buffer_defaults.orientation_reversed = Qnil;
   buffer_defaults.cursor_type = Qt;
   buffer_defaults.extra_line_spacing = Qnil;
   buffer_defaults.cursor_in_non_selected_windows = Qt;
@@ -5271,7 +5272,8 @@ init_buffer_once ()
   XSETFASTINT (buffer_local_flags.syntax_table, idx); ++idx;
   XSETFASTINT (buffer_local_flags.cache_long_line_scans, idx); ++idx;
   XSETFASTINT (buffer_local_flags.category_table, idx); ++idx;
-  XSETFASTINT (buffer_local_flags.direction_reversed, idx); ++idx;
+  XSETFASTINT (buffer_local_flags.enable_bidi_display, idx); ++idx;
+  XSETFASTINT (buffer_local_flags.orientation_reversed, idx); ++idx;
   XSETFASTINT (buffer_local_flags.buffer_file_coding_system, idx);
   /* Make this one a permanent local.  */
   buffer_permanent_local_flags[idx++] = 1;
@@ -5528,10 +5530,15 @@ This is the same as (default-value 'abbrev-mode).  */);
 		     doc: /* Default value of `ctl-arrow' for buffers that do not override it.
 This is the same as (default-value 'ctl-arrow).  */);
 
-  DEFVAR_LISP_NOPRO ("default-direction-reversed",
-                     &buffer_defaults.direction_reversed,
-                     doc: /* Default value of `direction-reversed' for buffers that do not override it.
-This is the same as (default-value 'direction-reversed).  */);
+    DEFVAR_LISP_NOPRO ("default-enable-bidi-display",
+		      &buffer_defaults.enable_bidi_display,
+		      doc: /* *Default value of `enable-bidi-display' for buffers not overriding it.
+This is the same as (default-value 'enable-bidi-display).  */);
+
+  DEFVAR_LISP_NOPRO ("default-orientation-reversed",
+		     &buffer_defaults.orientation_reversed,
+		     doc: /* *Default value of `orientation-reversed' for buffers that do not override it.
+This is the same as (default-value 'orientation-reversed).  */);
 
   DEFVAR_LISP_NOPRO ("default-enable-multibyte-characters",
                      &buffer_defaults.enable_multibyte_characters,
@@ -5789,11 +5796,17 @@ The variable `coding-system-for-write', if non-nil, overrides this variable.
 
 This variable is never applied to a way of decoding a file while reading it.  */);
 
-  DEFVAR_PER_BUFFER ("direction-reversed", &current_buffer->direction_reversed,
-		     Qnil,
-		     doc: /* *Non-nil means lines in the buffer are displayed right to left.  */);
+  DEFVAR_PER_BUFFER ("orientation-reversed",
+		     &current_buffer->orientation_reversed, Qnil,
+		     doc: /* Non-nil means set beginning of lines at the right end of the window.
+See also the variable `enable-bidi-display'.  */);
+
+  DEFVAR_PER_BUFFER ("enable-bidi-display",
+		     &current_buffer->enable_bidi_display, Qnil,
+		     doc: /*Non-nil means display bidi text in correct visual order.
+See also the variable `orientation-reversed'.  */);
 
-  DEFVAR_PER_BUFFER ("truncate-lines", &current_buffer->truncate_lines, Qnil,
+ DEFVAR_PER_BUFFER ("truncate-lines", &current_buffer->truncate_lines, Qnil,
 		     doc: /* *Non-nil means do not display continuation lines.
 Instead, give each line of text just one screen line.
 

src/buffer.h

@@ -658,8 +658,10 @@ struct buffer
   Lisp_Object word_wrap;
   /* Non-nil means display ctl chars with uparrow.  */
   Lisp_Object ctl_arrow;
-  /* Non-nil means display text from right to left.  */
-  Lisp_Object direction_reversed;
+  /* Non-nil means display bidi text in correct visual order.  */
+  Lisp_Object enable_bidi_display;
+  /* Non-nil means set beginning of lines at the right end of windows.  */
+  Lisp_Object orientation_reversed;
   /* Non-nil means do selective display;
      see doc string in syms_of_buffer (buffer.c) for details.  */
   Lisp_Object selective_display;

src/dispextern.h

@@ -1702,6 +1702,79 @@ struct face_cache
 
 extern int face_change_count;
 
+/* For BIDI */
+#define BIDI_MAXLEVEL 64
+
+/* Data type for describing the bidirectional character types.  */
+typedef enum {
+  UNKNOWN_BT,
+  STRONG_L,	/* strong left-to-right */
+  STRONG_R,	/* strong right-to-left */
+  STRONG_AL,	/* arabic right-to-left letter */
+  LRE,		/* left-to-right embedding */
+  LRO,		/* left-to-right override */
+  RLE,		/* right-to-left embedding */
+  RLO,		/* right-to-left override */
+  PDF,		/* pop directional format */
+  WEAK_EN,	/* european number */
+  WEAK_ES,	/* european number separator */
+  WEAK_ET,	/* european number terminator */
+  WEAK_AN,	/* arabic number */
+  WEAK_CS,	/* common separator */
+  WEAK_NSM,	/* non-spacing mark */
+  WEAK_BN,	/* boundary neutral */
+  NEUTRAL_B,	/* paragraph separator */
+  NEUTRAL_S,	/* segment separator */
+  NEUTRAL_WS,	/* whitespace */
+  NEUTRAL_ON	/* other neutrals */
+} bidi_type_t;
+
+/* The basic directionality data type.  */
+typedef enum { NEUTRAL_DIR, L2R, R2L } bidi_dir_t;
+
+/* Data type for storing information about characters we need to
+   remember.  */
+struct bidi_saved_info {
+  int bytepos, charpos;		/* character's buffer position */
+  bidi_type_t type;		/* character bidi type */
+  bidi_type_t orig_type;	/* original type of the character, after W1 */
+  bidi_type_t pristine_type;	/* type as we found it in the buffer */
+};
+
+/* Data type for keeping track of saved embedding levels and override
+   status information.  */
+struct bidi_stack {
+  int level;
+  bidi_dir_t override;
+};
+
+/* Data type for iterating over bidi text.  */
+struct bidi_it {
+  int bytepos;			/* iterator's position in buffer */
+  int charpos;
+  int ch;			/* the character itself */
+  int ch_len;			/* the length of its multibyte sequence */
+  bidi_type_t type;		/* type of this character */
+  bidi_type_t orig_type;	/* original type, after overrides and W1 */
+  bidi_type_t pristine_type;	/* original type, as found in the buffer */
+  int resolved_level;		/* final resolved level of this character */
+  int invalid_levels;		/* how many PDFs should we ignore */
+  int invalid_rl_levels;	/* how many PDFs from RLE/RLO should ignore */
+  int new_paragraph;		/* if non-zero, a new paragraph begins here */
+  int prev_was_pdf;		/* if non-zero, prev char was PDF */
+  struct bidi_saved_info prev;	/* info about the previous character */
+  struct bidi_saved_info last_strong; /* last-seen strong directional char */
+  struct bidi_saved_info next_for_neutral; /* surrounding characters for... */
+  struct bidi_saved_info prev_for_neutral; /* ...resolving neutrals */
+  struct bidi_saved_info next_for_ws; /* character after sequence of ws */
+  int next_en_pos;		/* position of next EN char for ET */
+  int ignore_bn_limit;		/* position until which we should ignore BNs */
+  bidi_dir_t sor;		/* direction of start-of-run in effect */
+  int scan_dir;			/* direction of text scan */
+  int stack_idx;		/* index of current data on the stack */
+  struct bidi_stack level_stack[BIDI_MAXLEVEL]; /* stack of embedding levels */
+};
+
 
 
 
@@ -2233,6 +2306,12 @@ struct it
 
   /* Face of the right fringe glyph.  */
   unsigned right_user_fringe_face_id : FACE_ID_BITS;
+
+  /* 1 means we need bidi processing.  */
+  int bidi_p;
+
+  /* For iterating over bidi text.  */
+  struct bidi_it bidi_it;
 };
 
 
@@ -2704,6 +2783,12 @@ extern EMACS_INT tool_bar_button_relief;
 			  Function Prototypes
  ***********************************************************************/
 
+/* Defined in bidi.c */
+
+extern void bidi_init_it P_ ((int pos, bidi_dir_t dir,
+			      struct bidi_it *bidi_it));
+extern void bidi_get_next_char_visually P_ ((struct bidi_it *bidi_it));
+
 /* Defined in xdisp.c */
 
 struct glyph_row *row_containing_pos P_ ((struct window *, int,

src/dispnew.c

@@ -3776,8 +3776,12 @@ direct_output_forward_char (n)
   if (!display_completed || cursor_in_echo_area)
     return 0;
 
-  /* Give up if the buffer's direction is reversed.  */
-  if (!NILP (XBUFFER (w->buffer)->direction_reversed))
+  /* Give up if we need bidi display.  */
+  if (!NILP (XBUFFER (w->buffer)->enable_bidi_display))
+    return 0;
+
+  /* Give up if the buffer's orientation is reversed.  */
+  if (!NILP (XBUFFER (w->buffer)->orientation_reversed))
     return 0;
 
   /* Can't use direct output if highlighting a region.  */

src/xdisp.c

@@ -2658,6 +2658,9 @@ init_iterator (it, w, charpos, bytepos, row, base_face_id)
   /* Are multibyte characters enabled in current_buffer?  */
   it->multibyte_p = !NILP (current_buffer->enable_multibyte_characters);
 
+  /* Do we need multibyte processing?  */
+  it->bidi_p = !NILP (current_buffer->enable_bidi_display);
+
   /* Non-zero if we should highlight the region.  */
   highlight_region_p
     = (!NILP (Vtransient_mark_mode)
@@ -5515,6 +5518,16 @@ reseat_1 (it, pos, set_stop_p)
   it->string_from_display_prop_p = 0;
   it->face_before_selective_p = 0;
 
+  if (it->bidi_p)
+    {
+      bidi_init_it (pos.charpos - 1, L2R, &it->bidi_it);
+      bidi_get_next_char_visually (&it->bidi_it);
+
+      pos.charpos = it->bidi_it.charpos;
+      pos.bytepos = it->bidi_it.bytepos;
+      it->current.pos = it->position = pos;
+    }
+
   if (set_stop_p)
     it->stop_charpos = CHARPOS (pos);
 }
@@ -6078,8 +6091,18 @@ set_iterator_to_next (it, reseat_p)
       else
 	{
 	  xassert (it->len != 0);
-	  IT_BYTEPOS (*it) += it->len;
-	  IT_CHARPOS (*it) += 1;
+
+	  if (! it->bidi_p)
+	    {
+	      IT_BYTEPOS (*it) += it->len;
+	      IT_CHARPOS (*it) += 1;
+	    }
+	  else
+	    {
+	      bidi_get_next_char_visually (&it->bidi_it);
+	      IT_BYTEPOS (*it) = it->bidi_it.charpos;
+	      IT_CHARPOS (*it) = it->bidi_it.bytepos;
+	    }
 	  xassert (IT_BYTEPOS (*it) == CHAR_TO_BYTE (IT_CHARPOS (*it)));
 	}
       break;