bidi.c 63.1 KB
Newer Older
Eli Zaretskii's avatar
Eli Zaretskii committed
1
/* Low-level bidirectional buffer-scanning functions for GNU Emacs.
2
   Copyright (C) 2000, 2001, 2004, 2005, 2009	Free Software Foundation, Inc.
Eli Zaretskii's avatar
Eli Zaretskii committed
3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

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 2, 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; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA.  */

22 23 24
/* Written by Eli Zaretskii <eliz@gnu.org>.

   A sequential implementation of the Unicode Bidirectional algorithm,
Eli Zaretskii's avatar
Eli Zaretskii committed
25 26 27 28 29 30 31 32 33 34 35 36 37 38
   as per UAX#9, a part of the Unicode Standard.

   Unlike the reference and most other implementations, this one is
   designed to be called once for every character in the buffer.

   The main entry point is bidi_get_next_char_visually.  Each time it
   is called, it finds the next character in the visual order, and
   returns its information in a special structure.  The caller is then
   expected to process this character for display or any other
   purposes, and call bidi_get_next_char_visually for the next
   character.  See the comments in bidi_get_next_char_visually for
   more details about its algorithm that finds the next visual-order
   character by resolving their levels on the fly.

39 40 41 42
   If you want to understand the code, you will have to read it
   together with the relevant portions of UAX#9.  The comments include
   references to UAX#9 rules, for that very reason.

Eli Zaretskii's avatar
Eli Zaretskii committed
43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66
   A note about references to UAX#9 rules: if the reference says
   something like "X9/Retaining", it means that you need to refer to
   rule X9 and to its modifications decribed in the "Implementation
   Notes" section of UAX#9, under "Retaining Format Codes".  */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>

#ifdef HAVE_STRING_H
#include <string.h>
#endif

#include "lisp.h"
#include "buffer.h"
#include "character.h"
#include "dispextern.h"

static int bidi_initialized = 0;

static Lisp_Object bidi_type_table;

67
/* FIXME: Remove these when bidi_explicit_dir_char uses a lookup table.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
68 69 70 71 72 73 74 75 76
#define LRM_CHAR   0x200E
#define RLM_CHAR   0x200F
#define LRE_CHAR   0x202A
#define RLE_CHAR   0x202B
#define PDF_CHAR   0x202C
#define LRO_CHAR   0x202D
#define RLO_CHAR   0x202E

#define BIDI_EOB   -1
77
#define BIDI_BOB   -2		/* FIXME: Is this needed? */
Eli Zaretskii's avatar
Eli Zaretskii committed
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98

/* Local data structures.  (Look in dispextern.h for the rest.)  */

/* What we need to know about the current paragraph.  */
struct bidi_paragraph_info {
  int start_bytepos;	/* byte position where it begins */
  int end_bytepos;	/* byte position where it ends */
  int embedding_level;	/* its basic embedding level */
  bidi_dir_t base_dir;	/* its base direction */
};

/* Data type for describing the bidirectional character categories.  */
typedef enum {
  UNKNOWN_BC,
  NEUTRAL,
  WEAK,
  STRONG
} bidi_category_t;

int bidi_ignore_explicit_marks_for_paragraph_level = 1;

99 100
static Lisp_Object fallback_paragraph_start_re, fallback_paragraph_separate_re;
static Lisp_Object Qparagraph_start, Qparagraph_separate;
Eli Zaretskii's avatar
Eli Zaretskii committed
101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122

static void
bidi_initialize ()
{
  /* FIXME: This should come from the Unicode Database.  */
  struct {
    int from, to;
    bidi_type_t type;
  } bidi_type[] =
      { { 0x0000, 0x0008, WEAK_BN },
	{ 0x0009, 0x0000, NEUTRAL_S },
	{ 0x000A, 0x0000, NEUTRAL_B },
	{ 0x000B, 0x0000, NEUTRAL_S },
	{ 0x000C, 0x0000, NEUTRAL_WS },
	{ 0x000D, 0x0000, NEUTRAL_B },
	{ 0x000E, 0x001B, WEAK_BN },
	{ 0x001C, 0x001E, NEUTRAL_B },
	{ 0x001F, 0x0000, NEUTRAL_S },
	{ 0x0020, 0x0000, NEUTRAL_WS },
	{ 0x0021, 0x0022, NEUTRAL_ON },
	{ 0x0023, 0x0025, WEAK_ET },
	{ 0x0026, 0x002A, NEUTRAL_ON },
123
	{ 0x002B, 0x0000, WEAK_ES },
Eli Zaretskii's avatar
Eli Zaretskii committed
124
	{ 0x002C, 0x0000, WEAK_CS },
125 126
	{ 0x002D, 0x0000, WEAK_ES },
	{ 0x002E, 0x002F, WEAK_CS },
Eli Zaretskii's avatar
Eli Zaretskii committed
127 128 129 130 131 132 133 134 135 136 137 138
	{ 0x0030, 0x0039, WEAK_EN },
	{ 0x003A, 0x0000, WEAK_CS },
	{ 0x003B, 0x0040, NEUTRAL_ON },
	{ 0x005B, 0x0060, NEUTRAL_ON },
	{ 0x007B, 0x007E, NEUTRAL_ON },
	{ 0x007F, 0x0084, WEAK_BN },
	{ 0x0085, 0x0000, NEUTRAL_B },
	{ 0x0086, 0x009F, WEAK_BN },
	{ 0x00A0, 0x0000, WEAK_CS },
	{ 0x00A1, 0x0000, NEUTRAL_ON },
	{ 0x00A2, 0x00A5, WEAK_ET },
	{ 0x00A6, 0x00A9, NEUTRAL_ON },
139 140 141
	{ 0x00AB, 0x00AC, NEUTRAL_ON },
	{ 0x00AD, 0x0000, WEAK_BN },
	{ 0x00AE, 0x00Af, NEUTRAL_ON },
Eli Zaretskii's avatar
Eli Zaretskii committed
142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166
	{ 0x00B0, 0x00B1, WEAK_ET },
	{ 0x00B2, 0x00B3, WEAK_EN },
	{ 0x00B4, 0x0000, NEUTRAL_ON },
	{ 0x00B6, 0x00B8, NEUTRAL_ON },
	{ 0x00B9, 0x0000, WEAK_EN },
	{ 0x00BB, 0x00BF, NEUTRAL_ON },
	{ 0x00D7, 0x0000, NEUTRAL_ON },
	{ 0x00F7, 0x0000, NEUTRAL_ON },
	{ 0x02B9, 0x02BA, NEUTRAL_ON },
	{ 0x02C2, 0x02CF, NEUTRAL_ON },
	{ 0x02D2, 0x02DF, NEUTRAL_ON },
	{ 0x02E5, 0x02ED, NEUTRAL_ON },
	{ 0x0300, 0x036F, WEAK_NSM },
	{ 0x0374, 0x0375, NEUTRAL_ON },
	{ 0x037E, 0x0385, NEUTRAL_ON },
	{ 0x0387, 0x0000, NEUTRAL_ON },
	{ 0x03F6, 0x0000, NEUTRAL_ON },
	{ 0x0483, 0x0489, WEAK_NSM },
	{ 0x058A, 0x0000, NEUTRAL_ON },
	{ 0x0591, 0x05BD, WEAK_NSM },
	{ 0x05BE, 0x0000, STRONG_R },
	{ 0x05BF, 0x0000, WEAK_NSM },
	{ 0x05C0, 0x0000, STRONG_R },
	{ 0x05C1, 0x05C2, WEAK_NSM },
	{ 0x05C3, 0x0000, STRONG_R },
167 168 169
	{ 0x05C4, 0x05C5, WEAK_NSM },
	{ 0x05C6, 0x0000, STRONG_R },
	{ 0x05C7, 0x0000, WEAK_NSM },
Eli Zaretskii's avatar
Eli Zaretskii committed
170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388
	{ 0x05D0, 0x05F4, STRONG_R },
	{ 0x060C, 0x0000, WEAK_CS },
	{ 0x061B, 0x064A, STRONG_AL },
	{ 0x064B, 0x0655, WEAK_NSM },
	{ 0x0660, 0x0669, WEAK_AN },
	{ 0x066A, 0x0000, WEAK_ET },
	{ 0x066B, 0x066C, WEAK_AN },
	{ 0x066D, 0x066F, STRONG_AL },
	{ 0x0670, 0x0000, WEAK_NSM },
	{ 0x0671, 0x06D5, STRONG_AL },
	{ 0x06D6, 0x06DC, WEAK_NSM },
	{ 0x06DD, 0x0000, STRONG_AL },
	{ 0x06DE, 0x06E4, WEAK_NSM },
	{ 0x06E5, 0x06E6, STRONG_AL },
	{ 0x06E7, 0x06E8, WEAK_NSM },
	{ 0x06E9, 0x0000, NEUTRAL_ON },
	{ 0x06EA, 0x06ED, WEAK_NSM },
	{ 0x06F0, 0x06F9, WEAK_EN },
	{ 0x06FA, 0x070D, STRONG_AL },
	{ 0x070F, 0x0000, WEAK_BN },
	{ 0x0710, 0x0000, STRONG_AL },
	{ 0x0711, 0x0000, WEAK_NSM },
	{ 0x0712, 0x072C, STRONG_AL },
	{ 0x0730, 0x074A, WEAK_NSM },
	{ 0x0780, 0x07A5, STRONG_AL },
	{ 0x07A6, 0x07B0, WEAK_NSM },
	{ 0x07B1, 0x0000, STRONG_AL },
	{ 0x0901, 0x0902, WEAK_NSM },
	{ 0x093C, 0x0000, WEAK_NSM },
	{ 0x0941, 0x0948, WEAK_NSM },
	{ 0x094D, 0x0000, WEAK_NSM },
	{ 0x0951, 0x0954, WEAK_NSM },
	{ 0x0962, 0x0963, WEAK_NSM },
	{ 0x0981, 0x0000, WEAK_NSM },
	{ 0x09BC, 0x0000, WEAK_NSM },
	{ 0x09C1, 0x09C4, WEAK_NSM },
	{ 0x09CD, 0x0000, WEAK_NSM },
	{ 0x09E2, 0x09E3, WEAK_NSM },
	{ 0x09F2, 0x09F3, WEAK_ET },
	{ 0x0A02, 0x0000, WEAK_NSM },
	{ 0x0A3C, 0x0000, WEAK_NSM },
	{ 0x0A41, 0x0A4D, WEAK_NSM },
	{ 0x0A70, 0x0A71, WEAK_NSM },
	{ 0x0A81, 0x0A82, WEAK_NSM },
	{ 0x0ABC, 0x0000, WEAK_NSM },
	{ 0x0AC1, 0x0AC8, WEAK_NSM },
	{ 0x0ACD, 0x0000, WEAK_NSM },
	{ 0x0B01, 0x0000, WEAK_NSM },
	{ 0x0B3C, 0x0000, WEAK_NSM },
	{ 0x0B3F, 0x0000, WEAK_NSM },
	{ 0x0B41, 0x0B43, WEAK_NSM },
	{ 0x0B4D, 0x0B56, WEAK_NSM },
	{ 0x0B82, 0x0000, WEAK_NSM },
	{ 0x0BC0, 0x0000, WEAK_NSM },
	{ 0x0BCD, 0x0000, WEAK_NSM },
	{ 0x0C3E, 0x0C40, WEAK_NSM },
	{ 0x0C46, 0x0C56, WEAK_NSM },
	{ 0x0CBF, 0x0000, WEAK_NSM },
	{ 0x0CC6, 0x0000, WEAK_NSM },
	{ 0x0CCC, 0x0CCD, WEAK_NSM },
	{ 0x0D41, 0x0D43, WEAK_NSM },
	{ 0x0D4D, 0x0000, WEAK_NSM },
	{ 0x0DCA, 0x0000, WEAK_NSM },
	{ 0x0DD2, 0x0DD6, WEAK_NSM },
	{ 0x0E31, 0x0000, WEAK_NSM },
	{ 0x0E34, 0x0E3A, WEAK_NSM },
	{ 0x0E3F, 0x0000, WEAK_ET },
	{ 0x0E47, 0x0E4E, WEAK_NSM },
	{ 0x0EB1, 0x0000, WEAK_NSM },
	{ 0x0EB4, 0x0EBC, WEAK_NSM },
	{ 0x0EC8, 0x0ECD, WEAK_NSM },
	{ 0x0F18, 0x0F19, WEAK_NSM },
	{ 0x0F35, 0x0000, WEAK_NSM },
	{ 0x0F37, 0x0000, WEAK_NSM },
	{ 0x0F39, 0x0000, WEAK_NSM },
	{ 0x0F3A, 0x0F3D, NEUTRAL_ON },
	{ 0x0F71, 0x0F7E, WEAK_NSM },
	{ 0x0F80, 0x0F84, WEAK_NSM },
	{ 0x0F86, 0x0F87, WEAK_NSM },
	{ 0x0F90, 0x0FBC, WEAK_NSM },
	{ 0x0FC6, 0x0000, WEAK_NSM },
	{ 0x102D, 0x1030, WEAK_NSM },
	{ 0x1032, 0x1037, WEAK_NSM },
	{ 0x1039, 0x0000, WEAK_NSM },
	{ 0x1058, 0x1059, WEAK_NSM },
	{ 0x1680, 0x0000, NEUTRAL_WS },
	{ 0x169B, 0x169C, NEUTRAL_ON },
	{ 0x1712, 0x1714, WEAK_NSM },
	{ 0x1732, 0x1734, WEAK_NSM },
	{ 0x1752, 0x1753, WEAK_NSM },
	{ 0x1772, 0x1773, WEAK_NSM },
	{ 0x17B7, 0x17BD, WEAK_NSM },
	{ 0x17C6, 0x0000, WEAK_NSM },
	{ 0x17C9, 0x17D3, WEAK_NSM },
	{ 0x17DB, 0x0000, WEAK_ET },
	{ 0x1800, 0x180A, NEUTRAL_ON },
	{ 0x180B, 0x180D, WEAK_NSM },
	{ 0x180E, 0x0000, WEAK_BN },
	{ 0x18A9, 0x0000, WEAK_NSM },
	{ 0x1FBD, 0x0000, NEUTRAL_ON },
	{ 0x1FBF, 0x1FC1, NEUTRAL_ON },
	{ 0x1FCD, 0x1FCF, NEUTRAL_ON },
	{ 0x1FDD, 0x1FDF, NEUTRAL_ON },
	{ 0x1FED, 0x1FEF, NEUTRAL_ON },
	{ 0x1FFD, 0x1FFE, NEUTRAL_ON },
	{ 0x2000, 0x200A, NEUTRAL_WS },
	{ 0x200B, 0x200D, WEAK_BN },
	{ 0x200F, 0x0000, STRONG_R },
	{ 0x2010, 0x2027, NEUTRAL_ON },
	{ 0x2028, 0x0000, NEUTRAL_WS },
	{ 0x2029, 0x0000, NEUTRAL_B },
	{ 0x202A, 0x0000, LRE },
	{ 0x202B, 0x0000, RLE },
	{ 0x202C, 0x0000, PDF },
	{ 0x202D, 0x0000, LRO },
	{ 0x202E, 0x0000, RLO },
	{ 0x202F, 0x0000, NEUTRAL_WS },
	{ 0x2030, 0x2034, WEAK_ET },
	{ 0x2035, 0x2057, NEUTRAL_ON },
	{ 0x205F, 0x0000, NEUTRAL_WS },
	{ 0x2060, 0x206F, WEAK_BN },
	{ 0x2070, 0x0000, WEAK_EN },
	{ 0x2074, 0x2079, WEAK_EN },
	{ 0x207A, 0x207B, WEAK_ET },
	{ 0x207C, 0x207E, NEUTRAL_ON },
	{ 0x2080, 0x2089, WEAK_EN },
	{ 0x208A, 0x208B, WEAK_ET },
	{ 0x208C, 0x208E, NEUTRAL_ON },
	{ 0x20A0, 0x20B1, WEAK_ET },
	{ 0x20D0, 0x20EA, WEAK_NSM },
	{ 0x2100, 0x2101, NEUTRAL_ON },
	{ 0x2103, 0x2106, NEUTRAL_ON },
	{ 0x2108, 0x2109, NEUTRAL_ON },
	{ 0x2114, 0x0000, NEUTRAL_ON },
	{ 0x2116, 0x2118, NEUTRAL_ON },
	{ 0x211E, 0x2123, NEUTRAL_ON },
	{ 0x2125, 0x0000, NEUTRAL_ON },
	{ 0x2127, 0x0000, NEUTRAL_ON },
	{ 0x2129, 0x0000, NEUTRAL_ON },
	{ 0x212E, 0x0000, WEAK_ET },
	{ 0x2132, 0x0000, NEUTRAL_ON },
	{ 0x213A, 0x0000, NEUTRAL_ON },
	{ 0x2140, 0x2144, NEUTRAL_ON },
	{ 0x214A, 0x215F, NEUTRAL_ON },
	{ 0x2190, 0x2211, NEUTRAL_ON },
	{ 0x2212, 0x2213, WEAK_ET },
	{ 0x2214, 0x2335, NEUTRAL_ON },
	{ 0x237B, 0x2394, NEUTRAL_ON },
	{ 0x2396, 0x244A, NEUTRAL_ON },
	{ 0x2460, 0x249B, WEAK_EN },
	{ 0x24EA, 0x0000, WEAK_EN },
	{ 0x24EB, 0x2FFB, NEUTRAL_ON },
	{ 0x3000, 0x0000, NEUTRAL_WS },
	{ 0x3001, 0x3004, NEUTRAL_ON },
	{ 0x3008, 0x3020, NEUTRAL_ON },
	{ 0x302A, 0x302F, WEAK_NSM },
	{ 0x3030, 0x0000, NEUTRAL_ON },
	{ 0x3036, 0x3037, NEUTRAL_ON },
	{ 0x303D, 0x303F, NEUTRAL_ON },
	{ 0x3099, 0x309A, WEAK_NSM },
	{ 0x309B, 0x309C, NEUTRAL_ON },
	{ 0x30A0, 0x0000, NEUTRAL_ON },
	{ 0x30FB, 0x0000, NEUTRAL_ON },
	{ 0x3251, 0x325F, NEUTRAL_ON },
	{ 0x32B1, 0x32BF, NEUTRAL_ON },
	{ 0xA490, 0xA4C6, NEUTRAL_ON },
	{ 0xFB1D, 0x0000, STRONG_R },
	{ 0xFB1E, 0x0000, WEAK_NSM },
	{ 0xFB1F, 0xFB28, STRONG_R },
	{ 0xFB29, 0x0000, WEAK_ET },
	{ 0xFB2A, 0xFB4F, STRONG_R },
	{ 0xFB50, 0xFD3D, STRONG_AL },
	{ 0xFD3E, 0xFD3F, NEUTRAL_ON },
	{ 0xFD50, 0xFDFC, STRONG_AL },
	{ 0xFE00, 0xFE23, WEAK_NSM },
	{ 0xFE30, 0xFE4F, NEUTRAL_ON },
	{ 0xFE50, 0x0000, WEAK_CS },
	{ 0xFE51, 0x0000, NEUTRAL_ON },
	{ 0xFE52, 0x0000, WEAK_CS },
	{ 0xFE54, 0x0000, NEUTRAL_ON },
	{ 0xFE55, 0x0000, WEAK_CS },
	{ 0xFE56, 0xFE5E, NEUTRAL_ON },
	{ 0xFE5F, 0x0000, WEAK_ET },
	{ 0xFE60, 0xFE61, NEUTRAL_ON },
	{ 0xFE62, 0xFE63, WEAK_ET },
	{ 0xFE64, 0xFE68, NEUTRAL_ON },
	{ 0xFE69, 0xFE6A, WEAK_ET },
	{ 0xFE6B, 0x0000, NEUTRAL_ON },
	{ 0xFE70, 0xFEFC, STRONG_AL },
	{ 0xFEFF, 0x0000, WEAK_BN },
	{ 0xFF01, 0xFF02, NEUTRAL_ON },
	{ 0xFF03, 0xFF05, WEAK_ET },
	{ 0xFF06, 0xFF0A, NEUTRAL_ON },
	{ 0xFF0B, 0x0000, WEAK_ET },
	{ 0xFF0C, 0x0000, WEAK_CS },
	{ 0xFF0D, 0x0000, WEAK_ET },
	{ 0xFF0E, 0x0000, WEAK_CS },
	{ 0xFF0F, 0x0000, WEAK_ES },
	{ 0xFF10, 0xFF19, WEAK_EN },
	{ 0xFF1A, 0x0000, WEAK_CS },
	{ 0xFF1B, 0xFF20, NEUTRAL_ON },
	{ 0xFF3B, 0xFF40, NEUTRAL_ON },
	{ 0xFF5B, 0xFF65, NEUTRAL_ON },
	{ 0xFFE0, 0xFFE1, WEAK_ET },
	{ 0xFFE2, 0xFFE4, NEUTRAL_ON },
	{ 0xFFE5, 0xFFE6, WEAK_ET },
	{ 0xFFE8, 0xFFEE, NEUTRAL_ON },
	{ 0xFFF9, 0xFFFB, WEAK_BN },
	{ 0xFFFC, 0xFFFD, NEUTRAL_ON },
	{ 0x1D167, 0x1D169, WEAK_NSM },
	{ 0x1D173, 0x1D17A, WEAK_BN },
	{ 0x1D17B, 0x1D182, WEAK_NSM },
	{ 0x1D185, 0x1D18B, WEAK_NSM },
	{ 0x1D1AA, 0x1D1AD, WEAK_NSM },
	{ 0x1D7CE, 0x1D7FF, WEAK_EN },
	{ 0xE0001, 0xE007F, WEAK_BN } };
  int i;

  bidi_type_table = Fmake_char_table (Qnil, make_number (STRONG_L));
389
  staticpro (&bidi_type_table);
Eli Zaretskii's avatar
Eli Zaretskii committed
390 391

  for (i = 0; i < sizeof bidi_type / sizeof bidi_type[0]; i++)
392 393
    char_table_set_range (bidi_type_table, bidi_type[i].from,
			  bidi_type[i].to ? bidi_type[i].to : bidi_type[i].from,
Eli Zaretskii's avatar
Eli Zaretskii committed
394
			  make_number (bidi_type[i].type));
395 396 397 398 399 400 401 402 403 404 405 406 407 408 409

  fallback_paragraph_start_re =
    XSYMBOL (Fintern_soft (build_string ("paragraph-start"), Qnil))->value;
  if (!STRINGP (fallback_paragraph_start_re))
    fallback_paragraph_start_re = build_string ("\f\\|[ \t]*$");
  staticpro (&fallback_paragraph_start_re);
  Qparagraph_start = intern ("paragraph-start");
  staticpro (&Qparagraph_start);
  fallback_paragraph_separate_re =
    XSYMBOL (Fintern_soft (build_string ("paragraph-separate"), Qnil))->value;
  if (!STRINGP (fallback_paragraph_separate_re))
    fallback_paragraph_separate_re = build_string ("[ \t\f]*$");
  staticpro (&fallback_paragraph_separate_re);
  Qparagraph_separate = intern ("paragraph-separate");
  staticpro (&Qparagraph_separate);
Eli Zaretskii's avatar
Eli Zaretskii committed
410 411 412
  bidi_initialized = 1;
}

413 414
/* Return the bidi type of a character CH, subject to the current
   directional OVERRIDE.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
415
bidi_type_t
416
bidi_get_type (int ch, bidi_dir_t override)
Eli Zaretskii's avatar
Eli Zaretskii committed
417
{
418 419
  bidi_type_t default_type;

420 421
  if (ch == BIDI_EOB)
    return NEUTRAL_B;
422 423
  if (ch < 0 || ch > MAX_CHAR)
    abort ();
424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455

  default_type = (bidi_type_t) XINT (CHAR_TABLE_REF (bidi_type_table, ch));

  if (override == NEUTRAL_DIR)
    return default_type;

  switch (default_type)
    {
      /* Although UAX#9 does not tell, it doesn't make sense to
	 override NEUTRAL_B and LRM/RLM characters.  */
      case NEUTRAL_B:
      case LRE:
      case LRO:
      case RLE:
      case RLO:
      case PDF:
	return default_type;
      default:
	switch (ch)
	  {
	    case LRM_CHAR:
	    case RLM_CHAR:
	      return default_type;
	    default:
	      if (override == L2R) /* X6 */
		return STRONG_L;
	      else if (override == R2L)
		return STRONG_R;
	      else
		abort ();	/* can't happen: handled above */
	  }
    }
Eli Zaretskii's avatar
Eli Zaretskii committed
456 457
}

458 459 460 461 462 463 464
void
bidi_check_type (bidi_type_t type)
{
  if (type < UNKNOWN_BT || type > NEUTRAL_ON)
    abort ();
}

Eli Zaretskii's avatar
Eli Zaretskii committed
465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499
/* Given a bidi TYPE of a character, return its category.  */
bidi_category_t
bidi_get_category (bidi_type_t type)
{
  switch (type)
    {
      case UNKNOWN_BT:
	return UNKNOWN_BC;
      case STRONG_L:
      case STRONG_R:
      case STRONG_AL:
      case LRE:
      case LRO:
      case RLE:
      case RLO:
	return STRONG;
      case PDF:		/* ??? really?? */
      case WEAK_EN:
      case WEAK_ES:
      case WEAK_ET:
      case WEAK_AN:
      case WEAK_CS:
      case WEAK_NSM:
      case WEAK_BN:
	return WEAK;
      case NEUTRAL_B:
      case NEUTRAL_S:
      case NEUTRAL_WS:
      case NEUTRAL_ON:
	return NEUTRAL;
      default:
	abort ();
    }
}

500 501 502 503
/* Return the mirrored character of C, if any.

   Note: The conditions in UAX#9 clause L4 must be tested by the
   caller.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528
/* FIXME: exceedingly temporary!  Should consult the Unicode database
   of character properties.  */
int
bidi_mirror_char (int c)
{
  static const char mirrored_pairs[] = "()<>[]{}";
  const char *p = strchr (mirrored_pairs, c);

  if (p)
    {
      size_t i = p - mirrored_pairs;

      if ((i & 1) == 0)
	return mirrored_pairs[i + 1];
      else
	return mirrored_pairs[i - 1];
    }
  return c;
}

/* Copy the bidi iterator from FROM to TO.  To save cycles, this only
   copies the part of the level stack that is actually in use.  */
static inline void
bidi_copy_it (struct bidi_it *to, struct bidi_it *from)
{
529
  int save_first_elt = to->first_elt;
Eli Zaretskii's avatar
Eli Zaretskii committed
530 531 532 533
  int i;

  /* Copy everything except the level stack.  */
  memcpy (to, from, ((int)&((struct bidi_it *)0)->level_stack[0]));
534 535 536
  to->first_elt = save_first_elt;
  if (to->first_elt != 0 && to->first_elt != 1)
    to->first_elt = 0;
Eli Zaretskii's avatar
Eli Zaretskii committed
537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688

  /* Copy the active part of the level stack.  */
  to->level_stack[0] = from->level_stack[0]; /* level zero is always in use */
  for (i = 1; i <= from->stack_idx; i++)
    to->level_stack[i] = from->level_stack[i];
}

/* Caching the bidi iterator states.  */

static struct bidi_it bidi_cache[1000]; /* FIXME: make this dynamically allocated! */
static int bidi_cache_idx;
static int bidi_cache_last_idx;

static inline void
bidi_cache_reset (void)
{
  bidi_cache_idx = 0;
  bidi_cache_last_idx = -1;
}

static inline void
bidi_cache_fetch_state (int idx, struct bidi_it *bidi_it)
{
  int current_scan_dir = bidi_it->scan_dir;

  if (idx < 0 || idx >= bidi_cache_idx)
    abort ();

  bidi_copy_it (bidi_it, &bidi_cache[idx]);
  bidi_it->scan_dir = current_scan_dir;
  bidi_cache_last_idx = idx;
}

/* Find a cached state with a given CHARPOS and resolved embedding
   level less or equal to LEVEL.  if LEVEL is -1, disregard the
   resolved levels in cached states.  DIR, if non-zero, means search
   in that direction from the last cache hit.  */
static inline int
bidi_cache_search (int charpos, int level, int dir)
{
  int i, i_start;

  if (bidi_cache_idx)
    {
      if (charpos < bidi_cache[bidi_cache_last_idx].charpos)
	dir = -1;
      else if (charpos > bidi_cache[bidi_cache_last_idx].charpos)
	dir = 1;
      if (dir)
	i_start = bidi_cache_last_idx;
      else
	{
	  dir = -1;
	  i_start = bidi_cache_idx - 1;
	}

      if (dir < 0)
	{
	  /* Linear search for now; FIXME!  */
	  for (i = i_start; i >= 0; i--)
	    if (bidi_cache[i].charpos == charpos
		&& (level == -1 || bidi_cache[i].resolved_level <= level))
	      return i;
	}
      else
	{
	  for (i = i_start; i < bidi_cache_idx; i++)
	    if (bidi_cache[i].charpos == charpos
		&& (level == -1 || bidi_cache[i].resolved_level <= level))
	      return i;
	}
    }

  return -1;
}

/* Find a cached state where the resolved level changes to a value
   that is lower than LEVEL, and return its cache slot index.  DIR is
   the direction to search, starting with the last used cache slot.
   BEFORE, if non-zero, means return the index of the slot that is
   ``before'' the level change in the search direction.  That is,
   given the cached levels like this:

	 1122333442211
	  AB        C

   and assuming we are at the position cached at the slot marked with
   C, searching backwards (DIR = -1) for LEVEL = 2 will return the
   index of slot B or A, depending whether BEFORE is, respectively,
   non-zero or zero.  */
static int
bidi_cache_find_level_change (int level, int dir, int before)
{
  if (bidi_cache_idx)
    {
      int i = dir ? bidi_cache_last_idx : bidi_cache_idx - 1;
      int incr = before ? 1 : 0;

      if (!dir)
	dir = -1;
      else if (!incr)
	i += dir;

      if (dir < 0)
	{
	  while (i >= incr)
	    {
	      if (bidi_cache[i - incr].resolved_level >= 0
		  && bidi_cache[i - incr].resolved_level < level)
		return i;
	      i--;
	    }
	}
      else
	{
	  while (i < bidi_cache_idx - incr)
	    {
	      if (bidi_cache[i + incr].resolved_level >= 0
		  && bidi_cache[i + incr].resolved_level < level)
		return i;
	      i++;
	    }
	}
    }

  return -1;
}

static inline void
bidi_cache_iterator_state (struct bidi_it *bidi_it, int resolved)
{
  int idx;

  /* We should never cache on backward scans.  */
  if (bidi_it->scan_dir == -1)
    abort ();
  idx = bidi_cache_search (bidi_it->charpos, -1, 1);

  if (idx < 0)
    {
      idx = bidi_cache_idx;
      if (idx > sizeof (bidi_cache) / sizeof (bidi_cache[0]) - 1)
	abort ();
      bidi_copy_it (&bidi_cache[idx], bidi_it);
      if (!resolved)
	bidi_cache[idx].resolved_level = -1;
    }
  else
    {
      /* Copy only the members which could have changed, to avoid
	 costly copying of the entire struct.  */
      bidi_cache[idx].type = bidi_it->type;
689
      bidi_check_type (bidi_it->type);
690 691
      bidi_cache[idx].type_after_w1 = bidi_it->type_after_w1;
      bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735
      if (resolved)
	bidi_cache[idx].resolved_level = bidi_it->resolved_level;
      else
	bidi_cache[idx].resolved_level = -1;
      bidi_cache[idx].invalid_levels = bidi_it->invalid_levels;
      bidi_cache[idx].invalid_rl_levels = bidi_it->invalid_rl_levels;
      bidi_cache[idx].next_for_neutral = bidi_it->next_for_neutral;
      bidi_cache[idx].next_for_ws = bidi_it->next_for_ws;
      bidi_cache[idx].ignore_bn_limit = bidi_it->ignore_bn_limit;
    }

  bidi_cache_last_idx = idx;
  if (idx >= bidi_cache_idx)
    bidi_cache_idx = idx + 1;
}

static inline bidi_type_t
bidi_cache_find (int charpos, int level, struct bidi_it *bidi_it)
{
  int i = bidi_cache_search (charpos, level, bidi_it->scan_dir);

  if (i >= 0)
    {
      bidi_dir_t current_scan_dir = bidi_it->scan_dir;

      *bidi_it = bidi_cache[i];
      bidi_cache_last_idx = i;
      /* Don't let scan direction from from the cached state override
	 the current scan direction.  */
      bidi_it->scan_dir = current_scan_dir;
      return bidi_it->type;
    }

  return UNKNOWN_BT;
}

static inline int
bidi_peek_at_next_level (struct bidi_it *bidi_it)
{
  if (bidi_cache_idx == 0 || bidi_cache_last_idx == -1)
    abort ();
  return bidi_cache[bidi_cache_last_idx + bidi_it->scan_dir].resolved_level;
}

736 737 738 739 740 741
/* Check if buffer position CHARPOS/BYTEPOS is the end of a paragraph.
   Value is the non-negative length of the paragraph separator
   following the buffer position, -1 if position is at the beginning
   of a new paragraph, or -2 if position is neither at beginning nor
   at end of a paragraph.  */
EMACS_INT
742
bidi_at_paragraph_end (EMACS_INT charpos, EMACS_INT bytepos)
Eli Zaretskii's avatar
Eli Zaretskii committed
743
{
744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762
  Lisp_Object sep_re = Fbuffer_local_value (Qparagraph_separate,
					    Fcurrent_buffer ());
  Lisp_Object start_re = Fbuffer_local_value (Qparagraph_start,
					      Fcurrent_buffer ());
  EMACS_INT val;

  if (!STRINGP (sep_re))
    sep_re = fallback_paragraph_separate_re;
  if (!STRINGP (start_re))
    start_re = fallback_paragraph_start_re;

  val = fast_looking_at (sep_re, charpos, bytepos, ZV, ZV_BYTE, Qnil);
  if (val < 0)
    {
      if (fast_looking_at (start_re, charpos, bytepos, ZV, ZV_BYTE, Qnil) >= 0)
	val = -1;
      else
	val = -2;
    }
Eli Zaretskii's avatar
Eli Zaretskii committed
763

764
  return val;
Eli Zaretskii's avatar
Eli Zaretskii committed
765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782
}

/* Determine the start-of-run (sor) directional type given the two
   embedding levels on either side of the run boundary.  Also, update
   the saved info about previously seen characters, since that info is
   generally valid for a single level run.  */
static inline void
bidi_set_sor_type (struct bidi_it *bidi_it, int level_before, int level_after)
{
  int higher_level = level_before > level_after ? level_before : level_after;

  /* The prev_was_pdf gork is required for when we have several PDFs
     in a row.  In that case, we want to compute the sor type for the
     next level run only once: when we see the first PDF.  That's
     because the sor type depends only on the higher of the two levels
     that we find on the two sides of the level boundary (see UAX#9,
     clause X10), and so we don't need to know the final embedding
     level to which we descend after processing all the PDFs.  */
783
  if (!bidi_it->prev_was_pdf || level_before < level_after)
Eli Zaretskii's avatar
Eli Zaretskii committed
784 785 786 787 788 789
    /* FIXME: should the default sor direction be user selectable?  */
    bidi_it->sor = (higher_level & 1) != 0 ? R2L : L2R;
  if (level_before > level_after)
    bidi_it->prev_was_pdf = 1;

  bidi_it->prev.type = UNKNOWN_BT;
790 791
  bidi_it->last_strong.type = bidi_it->last_strong.type_after_w1 =
    bidi_it->last_strong.orig_type = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
792 793 794
  bidi_it->prev_for_neutral.type = bidi_it->sor == R2L ? STRONG_R : STRONG_L;
  bidi_it->prev_for_neutral.charpos = bidi_it->charpos;
  bidi_it->prev_for_neutral.bytepos = bidi_it->bytepos;
795 796
  bidi_it->next_for_neutral.type = bidi_it->next_for_neutral.type_after_w1 =
    bidi_it->next_for_neutral.orig_type = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
797 798 799
  bidi_it->ignore_bn_limit = 0; /* meaning it's unknown */
}

800
static void
801 802 803 804 805 806 807 808 809
bidi_line_init (struct bidi_it *bidi_it)
{
  bidi_it->scan_dir = 1; /* FIXME: do we need to have control on this? */
  bidi_it->resolved_level = bidi_it->level_stack[0].level;
  bidi_it->level_stack[0].override = NEUTRAL_DIR; /* X1 */
  bidi_it->invalid_levels = 0;
  bidi_it->invalid_rl_levels = -1;
  bidi_it->next_en_pos = -1;
  bidi_it->next_for_ws.type = UNKNOWN_BT;
810 811
  bidi_set_sor_type (bidi_it,
		     bidi_it->paragraph_dir == R2L ? 1 : 0,
812 813 814 815 816 817 818 819
		     bidi_it->level_stack[0].level); /* X10 */

  bidi_cache_reset ();
}

/* Find the beginning of this paragraph by looking back in the buffer.
   Value is the byte position of the paragraph's beginning.  */
static EMACS_INT
820
bidi_find_paragraph_start (EMACS_INT pos, EMACS_INT pos_byte)
821
{
822
  Lisp_Object re = Fbuffer_local_value (Qparagraph_start, Fcurrent_buffer ());
823 824 825 826 827 828 829
  EMACS_INT limit = ZV, limit_byte = ZV_BYTE;

  if (!STRINGP (re))
    re = fallback_paragraph_start_re;
  while (pos_byte > BEGV_BYTE
	 && fast_looking_at (re, pos, pos_byte, limit, limit_byte, Qnil) < 0)
    {
830 831
      pos = find_next_newline_no_quit (pos - 1, -1);
      pos_byte = CHAR_TO_BYTE (pos);
832
    }
833
  return pos_byte;
834 835
}

836
/* Determine the direction, a.k.a. base embedding level, of the
837 838 839 840 841 842 843
   paragraph we are about to iterate through.  If DIR is either L2R or
   R2L, just use that.  Otherwise, determine the paragraph direction
   from the first strong character of the paragraph.

   Note that this gives the paragraph separator the same direction as
   the preceding paragraph, even though Emacs generally views the
   separartor as not belonging to any paragraph.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
844 845 846
void
bidi_paragraph_init (bidi_dir_t dir, struct bidi_it *bidi_it)
{
847
  EMACS_INT bytepos = bidi_it->bytepos;
848

849 850 851 852
  /* We should never be called at EOB or before BEGV.  */
  if (bytepos >= ZV_BYTE || bytepos < BEGV_BYTE)
    abort ();

853 854 855 856 857 858 859 860 861 862
  if (dir == L2R)
    {
      bidi_it->paragraph_dir = L2R;
      bidi_it->new_paragraph = 0;
    }
  else if (dir == R2L)
    {
      bidi_it->paragraph_dir = R2L;
      bidi_it->new_paragraph = 0;
    }
Eli Zaretskii's avatar
Eli Zaretskii committed
863 864
  else if (dir == NEUTRAL_DIR)	/* P2 */
    {
865 866 867
      int ch, ch_len;
      EMACS_INT pos;
      bidi_type_t type;
868 869 870 871 872 873 874 875
      EMACS_INT sep_len;

      /* If we are inside a paragraph separator, we are just waiting
	 for the separator to be exhausted; use the previous paragraph
	 direction.  */
      if (bidi_it->charpos < bidi_it->separator_limit)
	return;

876 877
      /* If we are on a newline, get past it to where the next
	 paragraph might start.  */
878
      pos = bidi_it->charpos;
879
      if (FETCH_CHAR (bytepos) == '\n')
880
	{
881
	  bytepos++;
882
	  pos++;
883
	}
884 885 886 887

      /* We are either at the beginning of a paragraph or in the
	 middle of it.  Find where this paragraph starts.  */
      bytepos = bidi_find_paragraph_start (pos, bytepos);
888 889 890

      /* We should always be at the beginning of a new line at this
	 point.  */
891
      if (!(bytepos == BEGV_BYTE || FETCH_CHAR (bytepos - 1) == '\n'))
892 893
	abort ();

894 895
      bidi_it->separator_limit = -1;
      bidi_it->new_paragraph = 0;
896 897
      ch = FETCH_CHAR (bytepos);
      ch_len = CHAR_BYTES (ch);
898
      pos = BYTE_TO_CHAR (bytepos);
899
      type = bidi_get_type (ch, NEUTRAL_DIR);
Eli Zaretskii's avatar
Eli Zaretskii committed
900

901
      for (pos++, bytepos += ch_len;
Eli Zaretskii's avatar
Eli Zaretskii committed
902 903 904 905 906 907 908 909
	   /* NOTE: UAX#9 says to search only for L, AL, or R types of
	      characters, and ignore RLE, RLO, LRE, and LRO.  However,
	      I'm not sure it makes sense to omit those 4; should try
	      with and without that to see the effect.  */
	   (bidi_get_category (type) != STRONG)
	     || (bidi_ignore_explicit_marks_for_paragraph_level
		 && (type == RLE || type == RLO
		     || type == LRE || type == LRO));
910
	   type = bidi_get_type (ch, NEUTRAL_DIR))
Eli Zaretskii's avatar
Eli Zaretskii committed
911
	{
912
	  if (type == NEUTRAL_B && bidi_at_paragraph_end (pos, bytepos) >= -1)
Eli Zaretskii's avatar
Eli Zaretskii committed
913 914 915 916
	    break;
	  FETCH_CHAR_ADVANCE (ch, pos, bytepos);
	}
      if (type == STRONG_R || type == STRONG_AL) /* P3 */
917 918 919
	bidi_it->paragraph_dir = R2L;
      else if (type == STRONG_L)
	bidi_it->paragraph_dir = L2R;
Eli Zaretskii's avatar
Eli Zaretskii committed
920
    }
921 922
  else
    abort ();
Eli Zaretskii's avatar
Eli Zaretskii committed
923

924 925 926
  /* Contrary to UAX#9 clause P3, we only default the paragraph
     direction to L2R if we have no previous usable paragraph
     direction.  */
927
  if (bidi_it->paragraph_dir == NEUTRAL_DIR)
928
    bidi_it->paragraph_dir = L2R; /* P3 and ``higher protocols'' */
929
  if (bidi_it->paragraph_dir == R2L)
930
    bidi_it->level_stack[0].level = 1;
931
  else
932
    bidi_it->level_stack[0].level = 0;
933 934

  bidi_line_init (bidi_it);
Eli Zaretskii's avatar
Eli Zaretskii committed
935 936
}

937 938
/* Do whatever UAX#9 clause X8 says should be done at paragraph's
   end.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
939 940 941 942 943 944 945 946 947
static inline void
bidi_set_paragraph_end (struct bidi_it *bidi_it)
{
  bidi_it->invalid_levels = 0;
  bidi_it->invalid_rl_levels = -1;
  bidi_it->stack_idx = 0;
  bidi_it->resolved_level = bidi_it->level_stack[0].level;
}

948
/* Initialize the bidi iterator from buffer position CHARPOS.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
949
void
950
bidi_init_it (EMACS_INT charpos, EMACS_INT bytepos, struct bidi_it *bidi_it)
Eli Zaretskii's avatar
Eli Zaretskii committed
951 952 953
{
  if (! bidi_initialized)
    bidi_initialize ();
954 955
  bidi_it->charpos = charpos;
  bidi_it->bytepos = bytepos;
956 957 958
  bidi_it->first_elt = 1;
  bidi_set_paragraph_end (bidi_it);
  bidi_it->new_paragraph = 1;
959
  bidi_it->separator_limit = -1;
960
  bidi_it->paragraph_dir = NEUTRAL_DIR;
Eli Zaretskii's avatar
Eli Zaretskii committed
961
  bidi_it->type = NEUTRAL_B;
962
  bidi_it->type_after_w1 = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
963 964
  bidi_it->orig_type = UNKNOWN_BT;
  bidi_it->prev_was_pdf = 0;
965 966 967
  bidi_it->prev.type = bidi_it->prev.type_after_w1 = UNKNOWN_BT;
  bidi_it->last_strong.type = bidi_it->last_strong.type_after_w1 =
    bidi_it->last_strong.orig_type = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
968 969
  bidi_it->next_for_neutral.charpos = -1;
  bidi_it->next_for_neutral.type =
970 971
    bidi_it->next_for_neutral.type_after_w1 =
    bidi_it->next_for_neutral.orig_type = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
972 973
  bidi_it->prev_for_neutral.charpos = -1;
  bidi_it->prev_for_neutral.type =
974 975
    bidi_it->prev_for_neutral.type_after_w1 =
    bidi_it->prev_for_neutral.orig_type = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010
  bidi_it->sor = L2R;	 /* FIXME: should it be user-selectable? */
}

/* Push the current embedding level and override status; reset the
   current level to LEVEL and the current override status to OVERRIDE.  */
static inline void
bidi_push_embedding_level (struct bidi_it *bidi_it,
			   int level, bidi_dir_t override)
{
  bidi_it->stack_idx++;
  if (bidi_it->stack_idx >= BIDI_MAXLEVEL)
    abort ();
  bidi_it->level_stack[bidi_it->stack_idx].level = level;
  bidi_it->level_stack[bidi_it->stack_idx].override = override;
}

/* Pop the embedding level and directional override status from the
   stack, and return the new level.  */
static inline int
bidi_pop_embedding_level (struct bidi_it *bidi_it)
{
  /* UAX#9 says to ignore invalid PDFs.  */
  if (bidi_it->stack_idx > 0)
    bidi_it->stack_idx--;
  return bidi_it->level_stack[bidi_it->stack_idx].level;
}

/* Record in SAVED_INFO the information about the current character.  */
static inline void
bidi_remember_char (struct bidi_saved_info *saved_info,
		    struct bidi_it *bidi_it)
{
  saved_info->charpos = bidi_it->charpos;
  saved_info->bytepos = bidi_it->bytepos;
  saved_info->type = bidi_it->type;
1011
  bidi_check_type (bidi_it->type);
1012 1013
  saved_info->type_after_w1 = bidi_it->type_after_w1;
  bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1014
  saved_info->orig_type = bidi_it->orig_type;
1015
  bidi_check_type (bidi_it->orig_type);
Eli Zaretskii's avatar
Eli Zaretskii committed
1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058
}

/* Resolve the type of a neutral character according to the type of
   surrounding strong text and the current embedding level.  */
static inline bidi_type_t
bidi_resolve_neutral_1 (bidi_type_t prev_type, bidi_type_t next_type, int lev)
{
  /* N1: European and Arabic numbers are treated as though they were R.  */
  if (next_type == WEAK_EN || next_type == WEAK_AN)
    next_type = STRONG_R;
  if (prev_type == WEAK_EN || prev_type == WEAK_AN)
    prev_type = STRONG_R;

  if (next_type == prev_type)	/* N1 */
    return next_type;
  else if ((lev & 1) == 0)	/* N2 */
    return STRONG_L;
  else
    return STRONG_R;
}

static inline int
bidi_explicit_dir_char (int c)
{
  /* FIXME: this should be replaced with a lookup table with suitable
     bits set, like standard C ctype macros do.  */
  return (c == LRE_CHAR || c == LRO_CHAR
	  || c == RLE_CHAR || c == RLO_CHAR || c == PDF_CHAR);
}

/* A helper function for bidi_resolve_explicit.  It advances to the
   next character in logical order and determines the new embedding
   level and directional override, but does not take into account
   empty embeddings.  */
static int
bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
{
  int curchar;
  bidi_type_t type;
  int current_level;
  int new_level;
  bidi_dir_t override;

1059 1060
  if (bidi_it->bytepos < BEGV_BYTE	/* after reseat to BEGV? */
      || bidi_it->first_elt)
1061
    {
1062 1063 1064 1065
      bidi_it->first_elt = 0;
      if (bidi_it->charpos < BEGV)
	bidi_it->charpos = BEGV;
      bidi_it->bytepos = CHAR_TO_BYTE (bidi_it->charpos);
1066
    }
1067
  else if (bidi_it->bytepos < ZV_BYTE)	/* don't move at ZV */
Eli Zaretskii's avatar
Eli Zaretskii committed
1068 1069
    {
      bidi_it->charpos++;
1070 1071
      if (bidi_it->ch_len == 0)
	abort ();
Eli Zaretskii's avatar
Eli Zaretskii committed
1072 1073 1074 1075 1076 1077 1078 1079 1080
      bidi_it->bytepos += bidi_it->ch_len;
    }

  current_level = bidi_it->level_stack[bidi_it->stack_idx].level; /* X1 */
  override = bidi_it->level_stack[bidi_it->stack_idx].override;
  new_level = current_level;

  /* in case it is a unibyte character (not yet implemented) */
  /* _fetch_multibyte_char_len = 1; */
1081 1082 1083 1084 1085 1086 1087 1088 1089 1090
  if (bidi_it->bytepos >= ZV_BYTE)
    {
      curchar = BIDI_EOB;
      bidi_it->ch_len = 1;
    }
  else
    {
      curchar = FETCH_CHAR (bidi_it->bytepos);
      bidi_it->ch_len = CHAR_BYTES (curchar);
    }
Eli Zaretskii's avatar
Eli Zaretskii committed
1091 1092
  bidi_it->ch = curchar;

1093 1094 1095 1096 1097
  /* Don't apply directional override here, as all the types we handle
     below will not be affected by the override anyway, and we need
     the original type unaltered.  The override will be applied in
     bidi_resolve_weak.  */
  type = bidi_get_type (curchar, NEUTRAL_DIR);
1098 1099
  bidi_it->orig_type = type;
  bidi_check_type (bidi_it->orig_type);
Eli Zaretskii's avatar
Eli Zaretskii committed
1100 1101 1102 1103

  if (type != PDF)
    bidi_it->prev_was_pdf = 0;

1104
  bidi_it->type_after_w1 = UNKNOWN_BT;
Eli Zaretskii's avatar
Eli Zaretskii committed
1105 1106 1107 1108 1109

  switch (type)
    {
      case RLE:	/* X2 */
      case RLO:	/* X4 */
1110 1111
	bidi_it->type_after_w1 = type;
	bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1112 1113 1114 1115 1116 1117 1118 1119
	type = WEAK_BN; /* X9/Retaining */
	if (bidi_it->ignore_bn_limit <= 0)
	  {
	    if (current_level <= BIDI_MAXLEVEL - 4)
	      {
		/* Compute the least odd embedding level greater than
		   the current level.  */
		new_level = ((current_level + 1) & ~1) + 1;
1120
		if (bidi_it->type_after_w1 == RLE)
Eli Zaretskii's avatar
Eli Zaretskii committed
1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136
		  override = NEUTRAL_DIR;
		else
		  override = R2L;
		if (current_level == BIDI_MAXLEVEL - 4)
		  bidi_it->invalid_rl_levels = 0;
		bidi_push_embedding_level (bidi_it, new_level, override);
	      }
	    else
	      {
		bidi_it->invalid_levels++;
		/* See the commentary about invalid_rl_levels below.  */
		if (bidi_it->invalid_rl_levels < 0)
		  bidi_it->invalid_rl_levels = 0;
		bidi_it->invalid_rl_levels++;
	      }
	  }
1137
	else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
Eli Zaretskii's avatar
Eli Zaretskii committed
1138 1139 1140 1141 1142
		 || bidi_it->next_en_pos > bidi_it->charpos)
	  type = WEAK_EN;
	break;
      case LRE:	/* X3 */
      case LRO:	/* X5 */
1143 1144
	bidi_it->type_after_w1 = type;
	bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1145 1146 1147 1148 1149 1150 1151 1152
	type = WEAK_BN; /* X9/Retaining */
	if (bidi_it->ignore_bn_limit <= 0)
	  {
	    if (current_level <= BIDI_MAXLEVEL - 5)
	      {
		/* Compute the least even embedding level greater than
		   the current level.  */
		new_level = ((current_level + 2) & ~1);
1153
		if (bidi_it->type_after_w1 == LRE)
Eli Zaretskii's avatar
Eli Zaretskii committed
1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172
		  override = NEUTRAL_DIR;
		else
		  override = L2R;
		bidi_push_embedding_level (bidi_it, new_level, override);
	      }
	    else
	      {
		bidi_it->invalid_levels++;
		/* invalid_rl_levels counts invalid levels encountered
		   while the embedding level was already too high for
		   LRE/LRO, but not for RLE/RLO.  That is because
		   there may be exactly one PDF which we should not
		   ignore even though invalid_levels is non-zero.
		   invalid_rl_levels helps to know what PDF is
		   that.  */
		if (bidi_it->invalid_rl_levels >= 0)
		  bidi_it->invalid_rl_levels++;
	      }
	  }
1173
	else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
Eli Zaretskii's avatar
Eli Zaretskii committed
1174 1175 1176 1177
		 || bidi_it->next_en_pos > bidi_it->charpos)
	  type = WEAK_EN;
	break;
      case PDF:	/* X7 */
1178 1179
	bidi_it->type_after_w1 = type;
	bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198
	type = WEAK_BN; /* X9/Retaining */
	if (bidi_it->ignore_bn_limit <= 0)
	  {
	    if (!bidi_it->invalid_rl_levels)
	      {
		new_level = bidi_pop_embedding_level (bidi_it);
		bidi_it->invalid_rl_levels = -1;
		if (bidi_it->invalid_levels)
		  bidi_it->invalid_levels--;
		/* else nothing: UAX#9 says to ignore invalid PDFs */
	      }
	    if (!bidi_it->invalid_levels)
	      new_level = bidi_pop_embedding_level (bidi_it);
	    else
	      {
		bidi_it->invalid_levels--;
		bidi_it->invalid_rl_levels--;
	      }
	  }
1199
	else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
Eli Zaretskii's avatar
Eli Zaretskii committed
1200 1201 1202 1203 1204 1205 1206 1207 1208
		 || bidi_it->next_en_pos > bidi_it->charpos)
	  type = WEAK_EN;
	break;
      default:
	/* Nothing.  */
	break;
    }

  bidi_it->type = type;
1209
  bidi_check_type (bidi_it->type);
Eli Zaretskii's avatar
Eli Zaretskii committed
1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227

  return new_level;
}

/* Given an iterator state in BIDI_IT, advance one character position
   in the buffer to the next character (in the logical order), resolve
   any explicit embeddings and directional overrides, and return the
   embedding level of the character after resolving explicit
   directives and ignoring empty embeddings.  */
static int
bidi_resolve_explicit (struct bidi_it *bidi_it)
{
  int prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
  int new_level  = bidi_resolve_explicit_1 (bidi_it);

  if (prev_level < new_level
      && bidi_it->type == WEAK_BN
      && bidi_it->ignore_bn_limit == 0 /* only if not already known */
1228
      && bidi_it->ch != BIDI_EOB       /* not already at EOB */
Eli Zaretskii's avatar
Eli Zaretskii committed
1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275
      && bidi_explicit_dir_char (FETCH_CHAR (bidi_it->bytepos
					     + bidi_it->ch_len)))
    {
      /* Avoid pushing and popping embedding levels if the level run
	 is empty, as this breaks level runs where it shouldn't.
	 UAX#9 removes all the explicit embedding and override codes,
	 so empty embeddings disappear without a trace.  We need to
	 behave as if we did the same.  */
      struct bidi_it saved_it;
      int level = prev_level;

      bidi_copy_it (&saved_it, bidi_it);

      while (bidi_explicit_dir_char (FETCH_CHAR (bidi_it->bytepos
						 + bidi_it->ch_len)))
	{
	  level = bidi_resolve_explicit_1 (bidi_it);
	}

      if (level == prev_level)	/* empty embedding */
	saved_it.ignore_bn_limit = bidi_it->charpos + 1;
      else			/* this embedding is non-empty */
	saved_it.ignore_bn_limit = -1;

      bidi_copy_it (bidi_it, &saved_it);
      if (bidi_it->ignore_bn_limit > 0)
	{
	  /* We pushed a level, but we shouldn't have.  Undo that. */
	  if (!bidi_it->invalid_rl_levels)
	    {
	      new_level = bidi_pop_embedding_level (bidi_it);
	      bidi_it->invalid_rl_levels = -1;
	      if (bidi_it->invalid_levels)
		bidi_it->invalid_levels--;
	    }
	  if (!bidi_it->invalid_levels)
	    new_level = bidi_pop_embedding_level (bidi_it);
	  else
	    {
	      bidi_it->invalid_levels--;
	      bidi_it->invalid_rl_levels--;
	    }
	}
    }

  if (bidi_it->type == NEUTRAL_B)	/* X8 */
    {
1276 1277 1278 1279 1280 1281 1282
      /* End of buffer does _not_ indicate a new paragraph is coming.
	 Otherwise, each character inserted at EOB will be processed
	 as starting a new paragraph.  */
      if (bidi_it->bytepos < ZV_BYTE)
	bidi_set_paragraph_end (bidi_it);
      /* This is needed by bidi_resolve_weak below, and in L1.  */
      bidi_it->type_after_w1 = bidi_it->type;
1283
      bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322
    }

  return new_level;
}

/* Advance in the buffer, resolve weak types and return the type of
   the next character after weak type resolution.  */
bidi_type_t
bidi_resolve_weak (struct bidi_it *bidi_it)
{
  bidi_type_t type;
  bidi_dir_t override;
  int prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
  int new_level  = bidi_resolve_explicit (bidi_it);
  int next_char;
  bidi_type_t type_of_next;
  struct bidi_it saved_it;

  type = bidi_it->type;
  override = bidi_it->level_stack[bidi_it->stack_idx].override;

  if (type == UNKNOWN_BT
      || type == LRE
      || type == LRO
      || type == RLE
      || type == RLO
      || type == PDF)
    abort ();

  if (new_level != prev_level
      || bidi_it->type == NEUTRAL_B)
    {
      /* We've got a new embedding level run, compute the directional
         type of sor and initialize per-run variables (UAX#9, clause
         X10).  */
      bidi_set_sor_type (bidi_it, prev_level, new_level);
    }
  else if (type == NEUTRAL_S || type == NEUTRAL_WS
	   || type == WEAK_BN || type == STRONG_AL)
1323 1324
    bidi_it->type_after_w1 = type;	/* needed in L1 */
  bidi_check_type (bidi_it->type_after_w1);
Eli Zaretskii's avatar
Eli Zaretskii committed
1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338

  /* Level and directional override status are already recorded in
     bidi_it, and do not need any change; see X6.  */
  if (override == R2L)		/* X6 */
    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
1339 1340
	 relevant to this NSM.  Thus, NSM gets the orig_type of the
	 previous character.  */
Eli Zaretskii's avatar
Eli Zaretskii committed
1341
      if (bidi_it->prev.type != UNKNOWN_BT)
1342
	type = bidi_it->prev.orig_type;
Eli Zaretskii's avatar
Eli Zaretskii committed
1343 1344 1345 1346 1347 1348 1349
      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 */
1350
	  && bidi_it->last_strong.type_after_w1 == STRONG_AL)
Eli Zaretskii's avatar
Eli Zaretskii committed
1351 1352 1353
	type = WEAK_AN;
    }
  else if (type == WEAK_EN	/* W2 */
1354
	   && bidi_it->last_strong.type_after_w1 == STRONG_AL)
Eli Zaretskii's avatar
Eli Zaretskii committed
1355 1356
    type = WEAK_AN;
  else if ((type == WEAK_ES
1357 1358 1359
	    && (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 */
Eli Zaretskii's avatar
Eli Zaretskii committed
1360
	   || (type == WEAK_CS
1361 1362 1363 1364
	       && ((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 */
Eli Zaretskii's avatar
Eli Zaretskii committed
1365
    {
1366 1367 1368
      next_char =
	bidi_it->bytepos + bidi_it->ch_len >= ZV_BYTE
	? BIDI_EOB : FETCH_CHAR (bidi_it->bytepos + bidi_it->ch_len);
1369
      type_of_next = bidi_get_type (next_char, override);
Eli Zaretskii's avatar
Eli Zaretskii committed
1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387

      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)
	    ;
	  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
1388
	  && bidi_it->last_strong.type_after_w1 != STRONG_AL)
Eli Zaretskii's avatar
Eli Zaretskii committed
1389 1390 1391
	type = WEAK_EN;
      else if (type == WEAK_CS)
	{
1392
	  if (bidi_it->prev.type_after_w1 == WEAK_AN
Eli Zaretskii's avatar
Eli Zaretskii committed
1393 1394 1395 1396 1397 1398 1399
	      && (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
1400
		      && bidi_it->last_strong.type_after_w1 == STRONG_AL)))
Eli Zaretskii's avatar
Eli Zaretskii committed
1401
	    type = WEAK_AN;
1402
	  else if (bidi_it->prev.type_after_w1 == WEAK_EN
Eli Zaretskii's avatar
Eli Zaretskii committed
1403
		   && type_of_next == WEAK_EN
1404
		   && bidi_it->last_strong.type_after_w1 != STRONG_AL)
Eli Zaretskii's avatar
Eli Zaretskii committed
1405 1406 1407 1408 1409 1410
	    type = WEAK_EN;
	}
    }
  else if (type == WEAK_ET	/* W5: ET with EN before or after it */
	   || type == WEAK_BN)	/* W5/Retaining */
    {
1411
      if (bidi_it->prev.type_after_w1 == WEAK_EN /* ET/BN with EN before it */
Eli Zaretskii's avatar
Eli Zaretskii committed
1412 1413 1414 1415 1416
	  || bidi_it->next_en_pos > bidi_it->charpos)
	type = WEAK_EN;
      /* W5: ET with EN after it.  */
      else
	{
1417
	  EMACS_INT en_pos = bidi_it->charpos + 1;
Eli Zaretskii's avatar
Eli Zaretskii committed
1418

1419 1420 1421
	  next_char =
	    bidi_it->bytepos + bidi_it->ch_len >= ZV_BYTE
	    ? BIDI_EOB : FETCH_CHAR (bidi_it->bytepos + bidi_it->ch_len);
1422
	  type_of_next = bidi_get_type (next_char, override);
Eli Zaretskii's avatar
Eli Zaretskii committed
1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439

	  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)
	    {
	      /* If the last strong character is AL, the EN we've
		 found will become AN when we get to it (W2). */
1440
	      if (bidi_it->last_strong.type_after_w1 != STRONG_AL)
Eli Zaretskii's avatar
Eli Zaretskii committed
1441 1442 1443 1444 1445 1446 1447 1448