More small edits for doc/lispref
[emacs.git] / src / bidi.c
blobb3479b17b168a3177f599d77b7c15cab7bcfab48
1 /* Low-level bidirectional buffer/string-scanning functions for GNU Emacs.
2 Copyright (C) 2000-2001, 2004-2005, 2009-2012
3 Free Software Foundation, Inc.
5 This file is part of GNU Emacs.
7 GNU Emacs is free software: you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation, either version 3 of the License, or
10 (at your option) any later version.
12 GNU Emacs is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
20 /* Written by Eli Zaretskii <eliz@gnu.org>.
22 A sequential implementation of the Unicode Bidirectional algorithm,
23 (UBA) as per UAX#9, a part of the Unicode Standard.
25 Unlike the reference and most other implementations, this one is
26 designed to be called once for every character in the buffer or
27 string.
29 The main entry point is bidi_move_to_visually_next. Each time it
30 is called, it finds the next character in the visual order, and
31 returns its information in a special structure. The caller is then
32 expected to process this character for display or any other
33 purposes, and call bidi_move_to_visually_next for the next
34 character. See the comments in bidi_move_to_visually_next for more
35 details about its algorithm that finds the next visual-order
36 character by resolving their levels on the fly.
38 Two other entry points are bidi_paragraph_init and
39 bidi_mirror_char. The first determines the base direction of a
40 paragraph, while the second returns the mirrored version of its
41 argument character.
43 A few auxiliary entry points are used to initialize the bidi
44 iterator for iterating an object (buffer or string), push and pop
45 the bidi iterator state, and save and restore the state of the bidi
46 cache.
48 If you want to understand the code, you will have to read it
49 together with the relevant portions of UAX#9. The comments include
50 references to UAX#9 rules, for that very reason.
52 A note about references to UAX#9 rules: if the reference says
53 something like "X9/Retaining", it means that you need to refer to
54 rule X9 and to its modifications described in the "Implementation
55 Notes" section of UAX#9, under "Retaining Format Codes". */
57 #include <config.h>
58 #include <stdio.h>
59 #include <setjmp.h>
61 #include "lisp.h"
62 #include "buffer.h"
63 #include "character.h"
64 #include "dispextern.h"
66 static int bidi_initialized = 0;
68 static Lisp_Object bidi_type_table, bidi_mirror_table;
70 #define LRM_CHAR 0x200E
71 #define RLM_CHAR 0x200F
72 #define BIDI_EOB -1
74 /* Data type for describing the bidirectional character categories. */
75 typedef enum {
76 UNKNOWN_BC,
77 NEUTRAL,
78 WEAK,
79 STRONG
80 } bidi_category_t;
82 /* UAX#9 says to search only for L, AL, or R types of characters, and
83 ignore RLE, RLO, LRE, and LRO, when determining the base paragraph
84 level. Yudit indeed ignores them. This variable is therefore set
85 by default to ignore them, but setting it to zero will take them
86 into account. */
87 extern int bidi_ignore_explicit_marks_for_paragraph_level EXTERNALLY_VISIBLE;
88 int bidi_ignore_explicit_marks_for_paragraph_level = 1;
90 static Lisp_Object paragraph_start_re, paragraph_separate_re;
91 static Lisp_Object Qparagraph_start, Qparagraph_separate;
94 /***********************************************************************
95 Utilities
96 ***********************************************************************/
98 /* Return the bidi type of a character CH, subject to the current
99 directional OVERRIDE. */
100 static inline bidi_type_t
101 bidi_get_type (int ch, bidi_dir_t override)
103 bidi_type_t default_type;
105 if (ch == BIDI_EOB)
106 return NEUTRAL_B;
107 if (ch < 0 || ch > MAX_CHAR)
108 abort ();
110 default_type = (bidi_type_t) XINT (CHAR_TABLE_REF (bidi_type_table, ch));
111 /* Every valid character code, even those that are unassigned by the
112 UCD, have some bidi-class property, according to
113 DerivedBidiClass.txt file. Therefore, if we ever get UNKNOWN_BT
114 (= zero) code from CHAR_TABLE_REF, that's a bug. */
115 if (default_type == UNKNOWN_BT)
116 abort ();
118 if (override == NEUTRAL_DIR)
119 return default_type;
121 switch (default_type)
123 /* Although UAX#9 does not tell, it doesn't make sense to
124 override NEUTRAL_B and LRM/RLM characters. */
125 case NEUTRAL_B:
126 case LRE:
127 case LRO:
128 case RLE:
129 case RLO:
130 case PDF:
131 return default_type;
132 default:
133 switch (ch)
135 case LRM_CHAR:
136 case RLM_CHAR:
137 return default_type;
138 default:
139 if (override == L2R) /* X6 */
140 return STRONG_L;
141 else if (override == R2L)
142 return STRONG_R;
143 else
144 abort (); /* can't happen: handled above */
149 static inline void
150 bidi_check_type (bidi_type_t type)
152 xassert (UNKNOWN_BT <= type && type <= NEUTRAL_ON);
155 /* Given a bidi TYPE of a character, return its category. */
156 static inline bidi_category_t
157 bidi_get_category (bidi_type_t type)
159 switch (type)
161 case UNKNOWN_BT:
162 return UNKNOWN_BC;
163 case STRONG_L:
164 case STRONG_R:
165 case STRONG_AL:
166 case LRE:
167 case LRO:
168 case RLE:
169 case RLO:
170 return STRONG;
171 case PDF: /* ??? really?? */
172 case WEAK_EN:
173 case WEAK_ES:
174 case WEAK_ET:
175 case WEAK_AN:
176 case WEAK_CS:
177 case WEAK_NSM:
178 case WEAK_BN:
179 return WEAK;
180 case NEUTRAL_B:
181 case NEUTRAL_S:
182 case NEUTRAL_WS:
183 case NEUTRAL_ON:
184 return NEUTRAL;
185 default:
186 abort ();
190 /* Return the mirrored character of C, if it has one. If C has no
191 mirrored counterpart, return C.
192 Note: The conditions in UAX#9 clause L4 regarding the surrounding
193 context must be tested by the caller. */
195 bidi_mirror_char (int c)
197 Lisp_Object val;
199 if (c == BIDI_EOB)
200 return c;
201 if (c < 0 || c > MAX_CHAR)
202 abort ();
204 val = CHAR_TABLE_REF (bidi_mirror_table, c);
205 if (INTEGERP (val))
207 int v = XINT (val);
209 if (v < 0 || v > MAX_CHAR)
210 abort ();
212 return v;
215 return c;
218 /* Determine the start-of-run (sor) directional type given the two
219 embedding levels on either side of the run boundary. Also, update
220 the saved info about previously seen characters, since that info is
221 generally valid for a single level run. */
222 static inline void
223 bidi_set_sor_type (struct bidi_it *bidi_it, int level_before, int level_after)
225 int higher_level = (level_before > level_after ? level_before : level_after);
227 /* The prev_was_pdf gork is required for when we have several PDFs
228 in a row. In that case, we want to compute the sor type for the
229 next level run only once: when we see the first PDF. That's
230 because the sor type depends only on the higher of the two levels
231 that we find on the two sides of the level boundary (see UAX#9,
232 clause X10), and so we don't need to know the final embedding
233 level to which we descend after processing all the PDFs. */
234 if (!bidi_it->prev_was_pdf || level_before < level_after)
235 /* FIXME: should the default sor direction be user selectable? */
236 bidi_it->sor = ((higher_level & 1) != 0 ? R2L : L2R);
237 if (level_before > level_after)
238 bidi_it->prev_was_pdf = 1;
240 bidi_it->prev.type = UNKNOWN_BT;
241 bidi_it->last_strong.type = bidi_it->last_strong.type_after_w1
242 = bidi_it->last_strong.orig_type = UNKNOWN_BT;
243 bidi_it->prev_for_neutral.type = (bidi_it->sor == R2L ? STRONG_R : STRONG_L);
244 bidi_it->prev_for_neutral.charpos = bidi_it->charpos;
245 bidi_it->prev_for_neutral.bytepos = bidi_it->bytepos;
246 bidi_it->next_for_neutral.type = bidi_it->next_for_neutral.type_after_w1
247 = bidi_it->next_for_neutral.orig_type = UNKNOWN_BT;
248 bidi_it->ignore_bn_limit = -1; /* meaning it's unknown */
251 /* Push the current embedding level and override status; reset the
252 current level to LEVEL and the current override status to OVERRIDE. */
253 static inline void
254 bidi_push_embedding_level (struct bidi_it *bidi_it,
255 int level, bidi_dir_t override)
257 bidi_it->stack_idx++;
258 xassert (bidi_it->stack_idx < BIDI_MAXLEVEL);
259 bidi_it->level_stack[bidi_it->stack_idx].level = level;
260 bidi_it->level_stack[bidi_it->stack_idx].override = override;
263 /* Pop the embedding level and directional override status from the
264 stack, and return the new level. */
265 static inline int
266 bidi_pop_embedding_level (struct bidi_it *bidi_it)
268 /* UAX#9 says to ignore invalid PDFs. */
269 if (bidi_it->stack_idx > 0)
270 bidi_it->stack_idx--;
271 return bidi_it->level_stack[bidi_it->stack_idx].level;
274 /* Record in SAVED_INFO the information about the current character. */
275 static inline void
276 bidi_remember_char (struct bidi_saved_info *saved_info,
277 struct bidi_it *bidi_it)
279 saved_info->charpos = bidi_it->charpos;
280 saved_info->bytepos = bidi_it->bytepos;
281 saved_info->type = bidi_it->type;
282 bidi_check_type (bidi_it->type);
283 saved_info->type_after_w1 = bidi_it->type_after_w1;
284 bidi_check_type (bidi_it->type_after_w1);
285 saved_info->orig_type = bidi_it->orig_type;
286 bidi_check_type (bidi_it->orig_type);
289 /* Copy the bidi iterator from FROM to TO. To save cycles, this only
290 copies the part of the level stack that is actually in use. */
291 static inline void
292 bidi_copy_it (struct bidi_it *to, struct bidi_it *from)
294 int i;
296 /* Copy everything except the level stack and beyond. */
297 memcpy (to, from, offsetof (struct bidi_it, level_stack[0]));
299 /* Copy the active part of the level stack. */
300 to->level_stack[0] = from->level_stack[0]; /* level zero is always in use */
301 for (i = 1; i <= from->stack_idx; i++)
302 to->level_stack[i] = from->level_stack[i];
306 /***********************************************************************
307 Caching the bidi iterator states
308 ***********************************************************************/
310 #define BIDI_CACHE_CHUNK 200
311 static struct bidi_it *bidi_cache;
312 static ptrdiff_t bidi_cache_size = 0;
313 enum { elsz = sizeof (struct bidi_it) };
314 static ptrdiff_t bidi_cache_idx; /* next unused cache slot */
315 static ptrdiff_t bidi_cache_last_idx; /* slot of last cache hit */
316 static ptrdiff_t bidi_cache_start = 0; /* start of cache for this
317 "stack" level */
319 /* 5-slot stack for saving the start of the previous level of the
320 cache. xdisp.c maintains a 5-slot stack for its iterator state,
321 and we need the same size of our stack. */
322 static ptrdiff_t bidi_cache_start_stack[IT_STACK_SIZE];
323 static int bidi_cache_sp;
325 /* Size of header used by bidi_shelve_cache. */
326 enum
328 bidi_shelve_header_size
329 = (sizeof (bidi_cache_idx) + sizeof (bidi_cache_start_stack)
330 + sizeof (bidi_cache_sp) + sizeof (bidi_cache_start)
331 + sizeof (bidi_cache_last_idx))
334 /* Reset the cache state to the empty state. We only reset the part
335 of the cache relevant to iteration of the current object. Previous
336 objects, which are pushed on the display iterator's stack, are left
337 intact. This is called when the cached information is no more
338 useful for the current iteration, e.g. when we were reseated to a
339 new position on the same object. */
340 static inline void
341 bidi_cache_reset (void)
343 bidi_cache_idx = bidi_cache_start;
344 bidi_cache_last_idx = -1;
347 /* Shrink the cache to its minimal size. Called when we init the bidi
348 iterator for reordering a buffer or a string that does not come
349 from display properties, because that means all the previously
350 cached info is of no further use. */
351 static inline void
352 bidi_cache_shrink (void)
354 if (bidi_cache_size > BIDI_CACHE_CHUNK)
356 bidi_cache
357 = (struct bidi_it *) xrealloc (bidi_cache, BIDI_CACHE_CHUNK * elsz);
358 bidi_cache_size = BIDI_CACHE_CHUNK;
360 bidi_cache_reset ();
363 static inline void
364 bidi_cache_fetch_state (ptrdiff_t idx, struct bidi_it *bidi_it)
366 int current_scan_dir = bidi_it->scan_dir;
368 if (idx < bidi_cache_start || idx >= bidi_cache_idx)
369 abort ();
371 bidi_copy_it (bidi_it, &bidi_cache[idx]);
372 bidi_it->scan_dir = current_scan_dir;
373 bidi_cache_last_idx = idx;
376 /* Find a cached state with a given CHARPOS and resolved embedding
377 level less or equal to LEVEL. if LEVEL is -1, disregard the
378 resolved levels in cached states. DIR, if non-zero, means search
379 in that direction from the last cache hit. */
380 static inline ptrdiff_t
381 bidi_cache_search (EMACS_INT charpos, int level, int dir)
383 ptrdiff_t i, i_start;
385 if (bidi_cache_idx > bidi_cache_start)
387 if (bidi_cache_last_idx == -1)
388 bidi_cache_last_idx = bidi_cache_idx - 1;
389 if (charpos < bidi_cache[bidi_cache_last_idx].charpos)
391 dir = -1;
392 i_start = bidi_cache_last_idx - 1;
394 else if (charpos > (bidi_cache[bidi_cache_last_idx].charpos
395 + bidi_cache[bidi_cache_last_idx].nchars - 1))
397 dir = 1;
398 i_start = bidi_cache_last_idx + 1;
400 else if (dir)
401 i_start = bidi_cache_last_idx;
402 else
404 dir = -1;
405 i_start = bidi_cache_idx - 1;
408 if (dir < 0)
410 /* Linear search for now; FIXME! */
411 for (i = i_start; i >= bidi_cache_start; i--)
412 if (bidi_cache[i].charpos <= charpos
413 && charpos < bidi_cache[i].charpos + bidi_cache[i].nchars
414 && (level == -1 || bidi_cache[i].resolved_level <= level))
415 return i;
417 else
419 for (i = i_start; i < bidi_cache_idx; i++)
420 if (bidi_cache[i].charpos <= charpos
421 && charpos < bidi_cache[i].charpos + bidi_cache[i].nchars
422 && (level == -1 || bidi_cache[i].resolved_level <= level))
423 return i;
427 return -1;
430 /* Find a cached state where the resolved level changes to a value
431 that is lower than LEVEL, and return its cache slot index. DIR is
432 the direction to search, starting with the last used cache slot.
433 If DIR is zero, we search backwards from the last occupied cache
434 slot. BEFORE, if non-zero, means return the index of the slot that
435 is ``before'' the level change in the search direction. That is,
436 given the cached levels like this:
438 1122333442211
439 AB C
441 and assuming we are at the position cached at the slot marked with
442 C, searching backwards (DIR = -1) for LEVEL = 2 will return the
443 index of slot B or A, depending whether BEFORE is, respectively,
444 non-zero or zero. */
445 static ptrdiff_t
446 bidi_cache_find_level_change (int level, int dir, int before)
448 if (bidi_cache_idx)
450 ptrdiff_t i = dir ? bidi_cache_last_idx : bidi_cache_idx - 1;
451 int incr = before ? 1 : 0;
453 xassert (!dir || bidi_cache_last_idx >= 0);
455 if (!dir)
456 dir = -1;
457 else if (!incr)
458 i += dir;
460 if (dir < 0)
462 while (i >= bidi_cache_start + incr)
464 if (bidi_cache[i - incr].resolved_level >= 0
465 && bidi_cache[i - incr].resolved_level < level)
466 return i;
467 i--;
470 else
472 while (i < bidi_cache_idx - incr)
474 if (bidi_cache[i + incr].resolved_level >= 0
475 && bidi_cache[i + incr].resolved_level < level)
476 return i;
477 i++;
482 return -1;
485 static inline void
486 bidi_cache_ensure_space (ptrdiff_t idx)
488 /* Enlarge the cache as needed. */
489 if (idx >= bidi_cache_size)
491 /* The bidi cache cannot be larger than the largest Lisp string
492 or buffer. */
493 ptrdiff_t string_or_buffer_bound
494 = max (BUF_BYTES_MAX, STRING_BYTES_BOUND);
496 /* Also, it cannot be larger than what C can represent. */
497 ptrdiff_t c_bound
498 = (min (PTRDIFF_MAX, SIZE_MAX) - bidi_shelve_header_size) / elsz;
500 bidi_cache
501 = xpalloc (bidi_cache, &bidi_cache_size,
502 max (BIDI_CACHE_CHUNK, idx - bidi_cache_size + 1),
503 min (string_or_buffer_bound, c_bound), elsz);
507 static inline void
508 bidi_cache_iterator_state (struct bidi_it *bidi_it, int resolved)
510 ptrdiff_t idx;
512 /* We should never cache on backward scans. */
513 if (bidi_it->scan_dir == -1)
514 abort ();
515 idx = bidi_cache_search (bidi_it->charpos, -1, 1);
517 if (idx < 0)
519 idx = bidi_cache_idx;
520 bidi_cache_ensure_space (idx);
521 /* Character positions should correspond to cache positions 1:1.
522 If we are outside the range of cached positions, the cache is
523 useless and must be reset. */
524 if (idx > bidi_cache_start &&
525 (bidi_it->charpos > (bidi_cache[idx - 1].charpos
526 + bidi_cache[idx - 1].nchars)
527 || bidi_it->charpos < bidi_cache[bidi_cache_start].charpos))
529 bidi_cache_reset ();
530 idx = bidi_cache_start;
532 if (bidi_it->nchars <= 0)
533 abort ();
534 bidi_copy_it (&bidi_cache[idx], bidi_it);
535 if (!resolved)
536 bidi_cache[idx].resolved_level = -1;
538 else
540 /* Copy only the members which could have changed, to avoid
541 costly copying of the entire struct. */
542 bidi_cache[idx].type = bidi_it->type;
543 bidi_check_type (bidi_it->type);
544 bidi_cache[idx].type_after_w1 = bidi_it->type_after_w1;
545 bidi_check_type (bidi_it->type_after_w1);
546 if (resolved)
547 bidi_cache[idx].resolved_level = bidi_it->resolved_level;
548 else
549 bidi_cache[idx].resolved_level = -1;
550 bidi_cache[idx].invalid_levels = bidi_it->invalid_levels;
551 bidi_cache[idx].invalid_rl_levels = bidi_it->invalid_rl_levels;
552 bidi_cache[idx].next_for_neutral = bidi_it->next_for_neutral;
553 bidi_cache[idx].next_for_ws = bidi_it->next_for_ws;
554 bidi_cache[idx].ignore_bn_limit = bidi_it->ignore_bn_limit;
555 bidi_cache[idx].disp_pos = bidi_it->disp_pos;
556 bidi_cache[idx].disp_prop = bidi_it->disp_prop;
559 bidi_cache_last_idx = idx;
560 if (idx >= bidi_cache_idx)
561 bidi_cache_idx = idx + 1;
564 static inline bidi_type_t
565 bidi_cache_find (EMACS_INT charpos, int level, struct bidi_it *bidi_it)
567 ptrdiff_t i = bidi_cache_search (charpos, level, bidi_it->scan_dir);
569 if (i >= bidi_cache_start)
571 bidi_dir_t current_scan_dir = bidi_it->scan_dir;
573 bidi_copy_it (bidi_it, &bidi_cache[i]);
574 bidi_cache_last_idx = i;
575 /* Don't let scan direction from the cached state override
576 the current scan direction. */
577 bidi_it->scan_dir = current_scan_dir;
578 return bidi_it->type;
581 return UNKNOWN_BT;
584 static inline int
585 bidi_peek_at_next_level (struct bidi_it *bidi_it)
587 if (bidi_cache_idx == bidi_cache_start || bidi_cache_last_idx == -1)
588 abort ();
589 return bidi_cache[bidi_cache_last_idx + bidi_it->scan_dir].resolved_level;
593 /***********************************************************************
594 Pushing and popping the bidi iterator state
595 ***********************************************************************/
597 /* Push the bidi iterator state in preparation for reordering a
598 different object, e.g. display string found at certain buffer
599 position. Pushing the bidi iterator boils down to saving its
600 entire state on the cache and starting a new cache "stacked" on top
601 of the current cache. */
602 void
603 bidi_push_it (struct bidi_it *bidi_it)
605 /* Save the current iterator state in its entirety after the last
606 used cache slot. */
607 bidi_cache_ensure_space (bidi_cache_idx);
608 memcpy (&bidi_cache[bidi_cache_idx++], bidi_it, sizeof (struct bidi_it));
610 /* Push the current cache start onto the stack. */
611 xassert (bidi_cache_sp < IT_STACK_SIZE);
612 bidi_cache_start_stack[bidi_cache_sp++] = bidi_cache_start;
614 /* Start a new level of cache, and make it empty. */
615 bidi_cache_start = bidi_cache_idx;
616 bidi_cache_last_idx = -1;
619 /* Restore the iterator state saved by bidi_push_it and return the
620 cache to the corresponding state. */
621 void
622 bidi_pop_it (struct bidi_it *bidi_it)
624 if (bidi_cache_start <= 0)
625 abort ();
627 /* Reset the next free cache slot index to what it was before the
628 call to bidi_push_it. */
629 bidi_cache_idx = bidi_cache_start - 1;
631 /* Restore the bidi iterator state saved in the cache. */
632 memcpy (bidi_it, &bidi_cache[bidi_cache_idx], sizeof (struct bidi_it));
634 /* Pop the previous cache start from the stack. */
635 if (bidi_cache_sp <= 0)
636 abort ();
637 bidi_cache_start = bidi_cache_start_stack[--bidi_cache_sp];
639 /* Invalidate the last-used cache slot data. */
640 bidi_cache_last_idx = -1;
643 static ptrdiff_t bidi_cache_total_alloc;
645 /* Stash away a copy of the cache and its control variables. */
646 void *
647 bidi_shelve_cache (void)
649 unsigned char *databuf;
650 ptrdiff_t alloc;
652 /* Empty cache. */
653 if (bidi_cache_idx == 0)
654 return NULL;
656 alloc = (bidi_shelve_header_size
657 + bidi_cache_idx * sizeof (struct bidi_it));
658 databuf = xmalloc (alloc);
659 bidi_cache_total_alloc += alloc;
661 memcpy (databuf, &bidi_cache_idx, sizeof (bidi_cache_idx));
662 memcpy (databuf + sizeof (bidi_cache_idx),
663 bidi_cache, bidi_cache_idx * sizeof (struct bidi_it));
664 memcpy (databuf + sizeof (bidi_cache_idx)
665 + bidi_cache_idx * sizeof (struct bidi_it),
666 bidi_cache_start_stack, sizeof (bidi_cache_start_stack));
667 memcpy (databuf + sizeof (bidi_cache_idx)
668 + bidi_cache_idx * sizeof (struct bidi_it)
669 + sizeof (bidi_cache_start_stack),
670 &bidi_cache_sp, sizeof (bidi_cache_sp));
671 memcpy (databuf + sizeof (bidi_cache_idx)
672 + bidi_cache_idx * sizeof (struct bidi_it)
673 + sizeof (bidi_cache_start_stack) + sizeof (bidi_cache_sp),
674 &bidi_cache_start, sizeof (bidi_cache_start));
675 memcpy (databuf + sizeof (bidi_cache_idx)
676 + bidi_cache_idx * sizeof (struct bidi_it)
677 + sizeof (bidi_cache_start_stack) + sizeof (bidi_cache_sp)
678 + sizeof (bidi_cache_start),
679 &bidi_cache_last_idx, sizeof (bidi_cache_last_idx));
681 return databuf;
684 /* Restore the cache state from a copy stashed away by
685 bidi_shelve_cache, and free the buffer used to stash that copy.
686 JUST_FREE non-zero means free the buffer, but don't restore the
687 cache; used when the corresponding iterator is discarded instead of
688 being restored. */
689 void
690 bidi_unshelve_cache (void *databuf, int just_free)
692 unsigned char *p = databuf;
694 if (!p)
696 if (!just_free)
698 /* A NULL pointer means an empty cache. */
699 bidi_cache_start = 0;
700 bidi_cache_sp = 0;
701 bidi_cache_reset ();
704 else
706 if (just_free)
708 ptrdiff_t idx;
710 memcpy (&idx, p, sizeof (bidi_cache_idx));
711 bidi_cache_total_alloc
712 -= bidi_shelve_header_size + idx * sizeof (struct bidi_it);
714 else
716 memcpy (&bidi_cache_idx, p, sizeof (bidi_cache_idx));
717 bidi_cache_ensure_space (bidi_cache_idx);
718 memcpy (bidi_cache, p + sizeof (bidi_cache_idx),
719 bidi_cache_idx * sizeof (struct bidi_it));
720 memcpy (bidi_cache_start_stack,
721 p + sizeof (bidi_cache_idx)
722 + bidi_cache_idx * sizeof (struct bidi_it),
723 sizeof (bidi_cache_start_stack));
724 memcpy (&bidi_cache_sp,
725 p + sizeof (bidi_cache_idx)
726 + bidi_cache_idx * sizeof (struct bidi_it)
727 + sizeof (bidi_cache_start_stack),
728 sizeof (bidi_cache_sp));
729 memcpy (&bidi_cache_start,
730 p + sizeof (bidi_cache_idx)
731 + bidi_cache_idx * sizeof (struct bidi_it)
732 + sizeof (bidi_cache_start_stack) + sizeof (bidi_cache_sp),
733 sizeof (bidi_cache_start));
734 memcpy (&bidi_cache_last_idx,
735 p + sizeof (bidi_cache_idx)
736 + bidi_cache_idx * sizeof (struct bidi_it)
737 + sizeof (bidi_cache_start_stack) + sizeof (bidi_cache_sp)
738 + sizeof (bidi_cache_start),
739 sizeof (bidi_cache_last_idx));
740 bidi_cache_total_alloc
741 -= (bidi_shelve_header_size
742 + bidi_cache_idx * sizeof (struct bidi_it));
745 xfree (p);
750 /***********************************************************************
751 Initialization
752 ***********************************************************************/
753 static void
754 bidi_initialize (void)
756 bidi_type_table = uniprop_table (intern ("bidi-class"));
757 if (NILP (bidi_type_table))
758 abort ();
759 staticpro (&bidi_type_table);
761 bidi_mirror_table = uniprop_table (intern ("mirroring"));
762 if (NILP (bidi_mirror_table))
763 abort ();
764 staticpro (&bidi_mirror_table);
766 Qparagraph_start = intern ("paragraph-start");
767 staticpro (&Qparagraph_start);
768 paragraph_start_re = Fsymbol_value (Qparagraph_start);
769 if (!STRINGP (paragraph_start_re))
770 paragraph_start_re = build_string ("\f\\|[ \t]*$");
771 staticpro (&paragraph_start_re);
772 Qparagraph_separate = intern ("paragraph-separate");
773 staticpro (&Qparagraph_separate);
774 paragraph_separate_re = Fsymbol_value (Qparagraph_separate);
775 if (!STRINGP (paragraph_separate_re))
776 paragraph_separate_re = build_string ("[ \t\f]*$");
777 staticpro (&paragraph_separate_re);
779 bidi_cache_sp = 0;
780 bidi_cache_total_alloc = 0;
782 bidi_initialized = 1;
785 /* Do whatever UAX#9 clause X8 says should be done at paragraph's
786 end. */
787 static inline void
788 bidi_set_paragraph_end (struct bidi_it *bidi_it)
790 bidi_it->invalid_levels = 0;
791 bidi_it->invalid_rl_levels = -1;
792 bidi_it->stack_idx = 0;
793 bidi_it->resolved_level = bidi_it->level_stack[0].level;
796 /* Initialize the bidi iterator from buffer/string position CHARPOS. */
797 void
798 bidi_init_it (EMACS_INT charpos, EMACS_INT bytepos, int frame_window_p,
799 struct bidi_it *bidi_it)
801 if (! bidi_initialized)
802 bidi_initialize ();
803 if (charpos >= 0)
804 bidi_it->charpos = charpos;
805 if (bytepos >= 0)
806 bidi_it->bytepos = bytepos;
807 bidi_it->frame_window_p = frame_window_p;
808 bidi_it->nchars = -1; /* to be computed in bidi_resolve_explicit_1 */
809 bidi_it->first_elt = 1;
810 bidi_set_paragraph_end (bidi_it);
811 bidi_it->new_paragraph = 1;
812 bidi_it->separator_limit = -1;
813 bidi_it->type = NEUTRAL_B;
814 bidi_it->type_after_w1 = NEUTRAL_B;
815 bidi_it->orig_type = NEUTRAL_B;
816 bidi_it->prev_was_pdf = 0;
817 bidi_it->prev.type = bidi_it->prev.type_after_w1
818 = bidi_it->prev.orig_type = UNKNOWN_BT;
819 bidi_it->last_strong.type = bidi_it->last_strong.type_after_w1
820 = bidi_it->last_strong.orig_type = UNKNOWN_BT;
821 bidi_it->next_for_neutral.charpos = -1;
822 bidi_it->next_for_neutral.type
823 = bidi_it->next_for_neutral.type_after_w1
824 = bidi_it->next_for_neutral.orig_type = UNKNOWN_BT;
825 bidi_it->prev_for_neutral.charpos = -1;
826 bidi_it->prev_for_neutral.type
827 = bidi_it->prev_for_neutral.type_after_w1
828 = bidi_it->prev_for_neutral.orig_type = UNKNOWN_BT;
829 bidi_it->sor = L2R; /* FIXME: should it be user-selectable? */
830 bidi_it->disp_pos = -1; /* invalid/unknown */
831 bidi_it->disp_prop = 0;
832 /* We can only shrink the cache if we are at the bottom level of its
833 "stack". */
834 if (bidi_cache_start == 0)
835 bidi_cache_shrink ();
836 else
837 bidi_cache_reset ();
840 /* Perform initializations for reordering a new line of bidi text. */
841 static void
842 bidi_line_init (struct bidi_it *bidi_it)
844 bidi_it->scan_dir = 1; /* FIXME: do we need to have control on this? */
845 bidi_it->resolved_level = bidi_it->level_stack[0].level;
846 bidi_it->level_stack[0].override = NEUTRAL_DIR; /* X1 */
847 bidi_it->invalid_levels = 0;
848 bidi_it->invalid_rl_levels = -1;
849 /* Setting this to zero will force its recomputation the first time
850 we need it for W5. */
851 bidi_it->next_en_pos = 0;
852 bidi_it->next_en_type = UNKNOWN_BT;
853 bidi_it->next_for_ws.type = UNKNOWN_BT;
854 bidi_set_sor_type (bidi_it,
855 (bidi_it->paragraph_dir == R2L ? 1 : 0),
856 bidi_it->level_stack[0].level); /* X10 */
858 bidi_cache_reset ();
862 /***********************************************************************
863 Fetching characters
864 ***********************************************************************/
866 /* Count bytes in string S between BEG/BEGBYTE and END. BEG and END
867 are zero-based character positions in S, BEGBYTE is byte position
868 corresponding to BEG. UNIBYTE, if non-zero, means S is a unibyte
869 string. */
870 static inline EMACS_INT
871 bidi_count_bytes (const unsigned char *s, const EMACS_INT beg,
872 const EMACS_INT begbyte, const EMACS_INT end, int unibyte)
874 EMACS_INT pos = beg;
875 const unsigned char *p = s + begbyte, *start = p;
877 if (unibyte)
878 p = s + end;
879 else
881 if (!CHAR_HEAD_P (*p))
882 abort ();
884 while (pos < end)
886 p += BYTES_BY_CHAR_HEAD (*p);
887 pos++;
891 return p - start;
894 /* Fetch and returns the character at byte position BYTEPOS. If S is
895 non-NULL, fetch the character from string S; otherwise fetch the
896 character from the current buffer. UNIBYTE non-zero means S is a
897 unibyte string. */
898 static inline int
899 bidi_char_at_pos (EMACS_INT bytepos, const unsigned char *s, int unibyte)
901 if (s)
903 if (unibyte)
904 return s[bytepos];
905 else
906 return STRING_CHAR (s + bytepos);
908 else
909 return FETCH_MULTIBYTE_CHAR (bytepos);
912 /* Fetch and return the character at BYTEPOS/CHARPOS. If that
913 character is covered by a display string, treat the entire run of
914 covered characters as a single character, either u+2029 or u+FFFC,
915 and return their combined length in CH_LEN and NCHARS. DISP_POS
916 specifies the character position of the next display string, or -1
917 if not yet computed. When the next character is at or beyond that
918 position, the function updates DISP_POS with the position of the
919 next display string. DISP_PROP non-zero means that there's really
920 a display string at DISP_POS, as opposed to when we searched till
921 DISP_POS without finding one. If DISP_PROP is 2, it means the
922 display spec is of the form `(space ...)', which is replaced with
923 u+2029 to handle it as a paragraph separator. STRING->s is the C
924 string to iterate, or NULL if iterating over a buffer or a Lisp
925 string; in the latter case, STRING->lstring is the Lisp string. */
926 static inline int
927 bidi_fetch_char (EMACS_INT bytepos, EMACS_INT charpos, EMACS_INT *disp_pos,
928 int *disp_prop, struct bidi_string_data *string,
929 int frame_window_p, EMACS_INT *ch_len, EMACS_INT *nchars)
931 int ch;
932 EMACS_INT endpos
933 = (string->s || STRINGP (string->lstring)) ? string->schars : ZV;
934 struct text_pos pos;
935 int len;
937 /* If we got past the last known position of display string, compute
938 the position of the next one. That position could be at CHARPOS. */
939 if (charpos < endpos && charpos > *disp_pos)
941 SET_TEXT_POS (pos, charpos, bytepos);
942 *disp_pos = compute_display_string_pos (&pos, string, frame_window_p,
943 disp_prop);
946 /* Fetch the character at BYTEPOS. */
947 if (charpos >= endpos)
949 ch = BIDI_EOB;
950 *ch_len = 1;
951 *nchars = 1;
952 *disp_pos = endpos;
953 *disp_prop = 0;
955 else if (charpos >= *disp_pos && *disp_prop)
957 EMACS_INT disp_end_pos;
959 /* We don't expect to find ourselves in the middle of a display
960 property. Hopefully, it will never be needed. */
961 if (charpos > *disp_pos)
962 abort ();
963 /* Text covered by `display' properties and overlays with
964 display properties or display strings is handled as a single
965 character that represents the entire run of characters
966 covered by the display property. */
967 if (*disp_prop == 2)
969 /* `(space ...)' display specs are handled as paragraph
970 separators for the purposes of the reordering; see UAX#9
971 section 3 and clause HL1 in section 4.3 there. */
972 ch = 0x2029;
974 else
976 /* All other display specs are handled as the Unicode Object
977 Replacement Character. */
978 ch = 0xFFFC;
980 disp_end_pos = compute_display_string_end (*disp_pos, string);
981 if (disp_end_pos < 0)
983 /* Somebody removed the display string from the buffer
984 behind our back. Recover by processing this buffer
985 position as if no display property were present there to
986 begin with. */
987 *disp_prop = 0;
988 goto normal_char;
990 *nchars = disp_end_pos - *disp_pos;
991 if (*nchars <= 0)
992 abort ();
993 if (string->s)
994 *ch_len = bidi_count_bytes (string->s, *disp_pos, bytepos,
995 disp_end_pos, string->unibyte);
996 else if (STRINGP (string->lstring))
997 *ch_len = bidi_count_bytes (SDATA (string->lstring), *disp_pos,
998 bytepos, disp_end_pos, string->unibyte);
999 else
1000 *ch_len = CHAR_TO_BYTE (disp_end_pos) - bytepos;
1002 else
1004 normal_char:
1005 if (string->s)
1008 if (!string->unibyte)
1010 ch = STRING_CHAR_AND_LENGTH (string->s + bytepos, len);
1011 *ch_len = len;
1013 else
1015 ch = UNIBYTE_TO_CHAR (string->s[bytepos]);
1016 *ch_len = 1;
1019 else if (STRINGP (string->lstring))
1021 if (!string->unibyte)
1023 ch = STRING_CHAR_AND_LENGTH (SDATA (string->lstring) + bytepos,
1024 len);
1025 *ch_len = len;
1027 else
1029 ch = UNIBYTE_TO_CHAR (SREF (string->lstring, bytepos));
1030 *ch_len = 1;
1033 else
1035 ch = STRING_CHAR_AND_LENGTH (BYTE_POS_ADDR (bytepos), len);
1036 *ch_len = len;
1038 *nchars = 1;
1041 /* If we just entered a run of characters covered by a display
1042 string, compute the position of the next display string. */
1043 if (charpos + *nchars <= endpos && charpos + *nchars > *disp_pos
1044 && *disp_prop)
1046 SET_TEXT_POS (pos, charpos + *nchars, bytepos + *ch_len);
1047 *disp_pos = compute_display_string_pos (&pos, string, frame_window_p,
1048 disp_prop);
1051 return ch;
1055 /***********************************************************************
1056 Determining paragraph direction
1057 ***********************************************************************/
1059 /* Check if buffer position CHARPOS/BYTEPOS is the end of a paragraph.
1060 Value is the non-negative length of the paragraph separator
1061 following the buffer position, -1 if position is at the beginning
1062 of a new paragraph, or -2 if position is neither at beginning nor
1063 at end of a paragraph. */
1064 static EMACS_INT
1065 bidi_at_paragraph_end (EMACS_INT charpos, EMACS_INT bytepos)
1067 Lisp_Object sep_re;
1068 Lisp_Object start_re;
1069 EMACS_INT val;
1071 sep_re = paragraph_separate_re;
1072 start_re = paragraph_start_re;
1074 val = fast_looking_at (sep_re, charpos, bytepos, ZV, ZV_BYTE, Qnil);
1075 if (val < 0)
1077 if (fast_looking_at (start_re, charpos, bytepos, ZV, ZV_BYTE, Qnil) >= 0)
1078 val = -1;
1079 else
1080 val = -2;
1083 return val;
1086 /* On my 2005-vintage machine, searching back for paragraph start
1087 takes ~1 ms per line. And bidi_paragraph_init is called 4 times
1088 when user types C-p. The number below limits each call to
1089 bidi_paragraph_init to about 10 ms. */
1090 #define MAX_PARAGRAPH_SEARCH 7500
1092 /* Find the beginning of this paragraph by looking back in the buffer.
1093 Value is the byte position of the paragraph's beginning, or
1094 BEGV_BYTE if paragraph_start_re is still not found after looking
1095 back MAX_PARAGRAPH_SEARCH lines in the buffer. */
1096 static EMACS_INT
1097 bidi_find_paragraph_start (EMACS_INT pos, EMACS_INT pos_byte)
1099 Lisp_Object re = paragraph_start_re;
1100 EMACS_INT limit = ZV, limit_byte = ZV_BYTE;
1101 EMACS_INT n = 0;
1103 while (pos_byte > BEGV_BYTE
1104 && n++ < MAX_PARAGRAPH_SEARCH
1105 && fast_looking_at (re, pos, pos_byte, limit, limit_byte, Qnil) < 0)
1107 /* FIXME: What if the paragraph beginning is covered by a
1108 display string? And what if a display string covering some
1109 of the text over which we scan back includes
1110 paragraph_start_re? */
1111 pos = find_next_newline_no_quit (pos - 1, -1);
1112 pos_byte = CHAR_TO_BYTE (pos);
1114 if (n >= MAX_PARAGRAPH_SEARCH)
1115 pos_byte = BEGV_BYTE;
1116 return pos_byte;
1119 /* Determine the base direction, a.k.a. base embedding level, of the
1120 paragraph we are about to iterate through. If DIR is either L2R or
1121 R2L, just use that. Otherwise, determine the paragraph direction
1122 from the first strong directional character of the paragraph.
1124 NO_DEFAULT_P non-zero means don't default to L2R if the paragraph
1125 has no strong directional characters and both DIR and
1126 bidi_it->paragraph_dir are NEUTRAL_DIR. In that case, search back
1127 in the buffer until a paragraph is found with a strong character,
1128 or until hitting BEGV. In the latter case, fall back to L2R. This
1129 flag is used in current-bidi-paragraph-direction.
1131 Note that this function gives the paragraph separator the same
1132 direction as the preceding paragraph, even though Emacs generally
1133 views the separator as not belonging to any paragraph. */
1134 void
1135 bidi_paragraph_init (bidi_dir_t dir, struct bidi_it *bidi_it, int no_default_p)
1137 EMACS_INT bytepos = bidi_it->bytepos;
1138 int string_p = bidi_it->string.s != NULL || STRINGP (bidi_it->string.lstring);
1139 EMACS_INT pstartbyte;
1140 /* Note that begbyte is a byte position, while end is a character
1141 position. Yes, this is ugly, but we are trying to avoid costly
1142 calls to BYTE_TO_CHAR and its ilk. */
1143 EMACS_INT begbyte = string_p ? 0 : BEGV_BYTE;
1144 EMACS_INT end = string_p ? bidi_it->string.schars : ZV;
1146 /* Special case for an empty buffer. */
1147 if (bytepos == begbyte && bidi_it->charpos == end)
1148 dir = L2R;
1149 /* We should never be called at EOB or before BEGV. */
1150 else if (bidi_it->charpos >= end || bytepos < begbyte)
1151 abort ();
1153 if (dir == L2R)
1155 bidi_it->paragraph_dir = L2R;
1156 bidi_it->new_paragraph = 0;
1158 else if (dir == R2L)
1160 bidi_it->paragraph_dir = R2L;
1161 bidi_it->new_paragraph = 0;
1163 else if (dir == NEUTRAL_DIR) /* P2 */
1165 int ch;
1166 EMACS_INT ch_len, nchars;
1167 EMACS_INT pos, disp_pos = -1;
1168 int disp_prop = 0;
1169 bidi_type_t type;
1170 const unsigned char *s;
1172 if (!bidi_initialized)
1173 bidi_initialize ();
1175 /* If we are inside a paragraph separator, we are just waiting
1176 for the separator to be exhausted; use the previous paragraph
1177 direction. But don't do that if we have been just reseated,
1178 because we need to reinitialize below in that case. */
1179 if (!bidi_it->first_elt
1180 && bidi_it->charpos < bidi_it->separator_limit)
1181 return;
1183 /* If we are on a newline, get past it to where the next
1184 paragraph might start. But don't do that at BEGV since then
1185 we are potentially in a new paragraph that doesn't yet
1186 exist. */
1187 pos = bidi_it->charpos;
1188 s = (STRINGP (bidi_it->string.lstring)
1189 ? SDATA (bidi_it->string.lstring)
1190 : bidi_it->string.s);
1191 if (bytepos > begbyte
1192 && bidi_char_at_pos (bytepos, s, bidi_it->string.unibyte) == '\n')
1194 bytepos++;
1195 pos++;
1198 /* We are either at the beginning of a paragraph or in the
1199 middle of it. Find where this paragraph starts. */
1200 if (string_p)
1202 /* We don't support changes of paragraph direction inside a
1203 string. It is treated as a single paragraph. */
1204 pstartbyte = 0;
1206 else
1207 pstartbyte = bidi_find_paragraph_start (pos, bytepos);
1208 bidi_it->separator_limit = -1;
1209 bidi_it->new_paragraph = 0;
1211 /* The following loop is run more than once only if NO_DEFAULT_P
1212 is non-zero, and only if we are iterating on a buffer. */
1213 do {
1214 bytepos = pstartbyte;
1215 if (!string_p)
1216 pos = BYTE_TO_CHAR (bytepos);
1217 ch = bidi_fetch_char (bytepos, pos, &disp_pos, &disp_prop,
1218 &bidi_it->string,
1219 bidi_it->frame_window_p, &ch_len, &nchars);
1220 type = bidi_get_type (ch, NEUTRAL_DIR);
1222 for (pos += nchars, bytepos += ch_len;
1223 (bidi_get_category (type) != STRONG)
1224 || (bidi_ignore_explicit_marks_for_paragraph_level
1225 && (type == RLE || type == RLO
1226 || type == LRE || type == LRO));
1227 type = bidi_get_type (ch, NEUTRAL_DIR))
1229 if (pos >= end)
1231 /* Pretend there's a paragraph separator at end of
1232 buffer/string. */
1233 type = NEUTRAL_B;
1234 break;
1236 if (!string_p
1237 && type == NEUTRAL_B
1238 && bidi_at_paragraph_end (pos, bytepos) >= -1)
1239 break;
1240 /* Fetch next character and advance to get past it. */
1241 ch = bidi_fetch_char (bytepos, pos, &disp_pos,
1242 &disp_prop, &bidi_it->string,
1243 bidi_it->frame_window_p, &ch_len, &nchars);
1244 pos += nchars;
1245 bytepos += ch_len;
1247 if ((type == STRONG_R || type == STRONG_AL) /* P3 */
1248 || (!bidi_ignore_explicit_marks_for_paragraph_level
1249 && (type == RLO || type == RLE)))
1250 bidi_it->paragraph_dir = R2L;
1251 else if (type == STRONG_L
1252 || (!bidi_ignore_explicit_marks_for_paragraph_level
1253 && (type == LRO || type == LRE)))
1254 bidi_it->paragraph_dir = L2R;
1255 if (!string_p
1256 && no_default_p && bidi_it->paragraph_dir == NEUTRAL_DIR)
1258 /* If this paragraph is at BEGV, default to L2R. */
1259 if (pstartbyte == BEGV_BYTE)
1260 bidi_it->paragraph_dir = L2R; /* P3 and HL1 */
1261 else
1263 EMACS_INT prevpbyte = pstartbyte;
1264 EMACS_INT p = BYTE_TO_CHAR (pstartbyte), pbyte = pstartbyte;
1266 /* Find the beginning of the previous paragraph, if any. */
1267 while (pbyte > BEGV_BYTE && prevpbyte >= pstartbyte)
1269 /* FXIME: What if p is covered by a display
1270 string? See also a FIXME inside
1271 bidi_find_paragraph_start. */
1272 p--;
1273 pbyte = CHAR_TO_BYTE (p);
1274 prevpbyte = bidi_find_paragraph_start (p, pbyte);
1276 pstartbyte = prevpbyte;
1279 } while (!string_p
1280 && no_default_p && bidi_it->paragraph_dir == NEUTRAL_DIR);
1282 else
1283 abort ();
1285 /* Contrary to UAX#9 clause P3, we only default the paragraph
1286 direction to L2R if we have no previous usable paragraph
1287 direction. This is allowed by the HL1 clause. */
1288 if (bidi_it->paragraph_dir != L2R && bidi_it->paragraph_dir != R2L)
1289 bidi_it->paragraph_dir = L2R; /* P3 and HL1 ``higher-level protocols'' */
1290 if (bidi_it->paragraph_dir == R2L)
1291 bidi_it->level_stack[0].level = 1;
1292 else
1293 bidi_it->level_stack[0].level = 0;
1295 bidi_line_init (bidi_it);
1299 /***********************************************************************
1300 Resolving explicit and implicit levels.
1301 The rest of this file constitutes the core of the UBA implementation.
1302 ***********************************************************************/
1304 static inline int
1305 bidi_explicit_dir_char (int ch)
1307 bidi_type_t ch_type;
1309 if (!bidi_initialized)
1310 abort ();
1311 ch_type = (bidi_type_t) XINT (CHAR_TABLE_REF (bidi_type_table, ch));
1312 return (ch_type == LRE || ch_type == LRO
1313 || ch_type == RLE || ch_type == RLO
1314 || ch_type == PDF);
1317 /* A helper function for bidi_resolve_explicit. It advances to the
1318 next character in logical order and determines the new embedding
1319 level and directional override, but does not take into account
1320 empty embeddings. */
1321 static int
1322 bidi_resolve_explicit_1 (struct bidi_it *bidi_it)
1324 int curchar;
1325 bidi_type_t type;
1326 int current_level;
1327 int new_level;
1328 bidi_dir_t override;
1329 int string_p = bidi_it->string.s != NULL || STRINGP (bidi_it->string.lstring);
1331 /* If reseat()'ed, don't advance, so as to start iteration from the
1332 position where we were reseated. bidi_it->bytepos can be less
1333 than BEGV_BYTE after reseat to BEGV. */
1334 if (bidi_it->bytepos < (string_p ? 0 : BEGV_BYTE)
1335 || bidi_it->first_elt)
1337 bidi_it->first_elt = 0;
1338 if (string_p)
1340 const unsigned char *p
1341 = (STRINGP (bidi_it->string.lstring)
1342 ? SDATA (bidi_it->string.lstring)
1343 : bidi_it->string.s);
1345 if (bidi_it->charpos < 0)
1346 bidi_it->charpos = 0;
1347 bidi_it->bytepos = bidi_count_bytes (p, 0, 0, bidi_it->charpos,
1348 bidi_it->string.unibyte);
1350 else
1352 if (bidi_it->charpos < BEGV)
1353 bidi_it->charpos = BEGV;
1354 bidi_it->bytepos = CHAR_TO_BYTE (bidi_it->charpos);
1357 /* Don't move at end of buffer/string. */
1358 else if (bidi_it->charpos < (string_p ? bidi_it->string.schars : ZV))
1360 /* Advance to the next character, skipping characters covered by
1361 display strings (nchars > 1). */
1362 if (bidi_it->nchars <= 0)
1363 abort ();
1364 bidi_it->charpos += bidi_it->nchars;
1365 if (bidi_it->ch_len == 0)
1366 abort ();
1367 bidi_it->bytepos += bidi_it->ch_len;
1370 current_level = bidi_it->level_stack[bidi_it->stack_idx].level; /* X1 */
1371 override = bidi_it->level_stack[bidi_it->stack_idx].override;
1372 new_level = current_level;
1374 if (bidi_it->charpos >= (string_p ? bidi_it->string.schars : ZV))
1376 curchar = BIDI_EOB;
1377 bidi_it->ch_len = 1;
1378 bidi_it->nchars = 1;
1379 bidi_it->disp_pos = (string_p ? bidi_it->string.schars : ZV);
1380 bidi_it->disp_prop = 0;
1382 else
1384 /* Fetch the character at BYTEPOS. If it is covered by a
1385 display string, treat the entire run of covered characters as
1386 a single character u+FFFC. */
1387 curchar = bidi_fetch_char (bidi_it->bytepos, bidi_it->charpos,
1388 &bidi_it->disp_pos, &bidi_it->disp_prop,
1389 &bidi_it->string, bidi_it->frame_window_p,
1390 &bidi_it->ch_len, &bidi_it->nchars);
1392 bidi_it->ch = curchar;
1394 /* Don't apply directional override here, as all the types we handle
1395 below will not be affected by the override anyway, and we need
1396 the original type unaltered. The override will be applied in
1397 bidi_resolve_weak. */
1398 type = bidi_get_type (curchar, NEUTRAL_DIR);
1399 bidi_it->orig_type = type;
1400 bidi_check_type (bidi_it->orig_type);
1402 if (type != PDF)
1403 bidi_it->prev_was_pdf = 0;
1405 bidi_it->type_after_w1 = UNKNOWN_BT;
1407 switch (type)
1409 case RLE: /* X2 */
1410 case RLO: /* X4 */
1411 bidi_it->type_after_w1 = type;
1412 bidi_check_type (bidi_it->type_after_w1);
1413 type = WEAK_BN; /* X9/Retaining */
1414 if (bidi_it->ignore_bn_limit <= -1)
1416 if (current_level <= BIDI_MAXLEVEL - 4)
1418 /* Compute the least odd embedding level greater than
1419 the current level. */
1420 new_level = ((current_level + 1) & ~1) + 1;
1421 if (bidi_it->type_after_w1 == RLE)
1422 override = NEUTRAL_DIR;
1423 else
1424 override = R2L;
1425 if (current_level == BIDI_MAXLEVEL - 4)
1426 bidi_it->invalid_rl_levels = 0;
1427 bidi_push_embedding_level (bidi_it, new_level, override);
1429 else
1431 bidi_it->invalid_levels++;
1432 /* See the commentary about invalid_rl_levels below. */
1433 if (bidi_it->invalid_rl_levels < 0)
1434 bidi_it->invalid_rl_levels = 0;
1435 bidi_it->invalid_rl_levels++;
1438 else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
1439 || (bidi_it->next_en_pos > bidi_it->charpos
1440 && bidi_it->next_en_type == WEAK_EN))
1441 type = WEAK_EN;
1442 break;
1443 case LRE: /* X3 */
1444 case LRO: /* X5 */
1445 bidi_it->type_after_w1 = type;
1446 bidi_check_type (bidi_it->type_after_w1);
1447 type = WEAK_BN; /* X9/Retaining */
1448 if (bidi_it->ignore_bn_limit <= -1)
1450 if (current_level <= BIDI_MAXLEVEL - 5)
1452 /* Compute the least even embedding level greater than
1453 the current level. */
1454 new_level = ((current_level + 2) & ~1);
1455 if (bidi_it->type_after_w1 == LRE)
1456 override = NEUTRAL_DIR;
1457 else
1458 override = L2R;
1459 bidi_push_embedding_level (bidi_it, new_level, override);
1461 else
1463 bidi_it->invalid_levels++;
1464 /* invalid_rl_levels counts invalid levels encountered
1465 while the embedding level was already too high for
1466 LRE/LRO, but not for RLE/RLO. That is because
1467 there may be exactly one PDF which we should not
1468 ignore even though invalid_levels is non-zero.
1469 invalid_rl_levels helps to know what PDF is
1470 that. */
1471 if (bidi_it->invalid_rl_levels >= 0)
1472 bidi_it->invalid_rl_levels++;
1475 else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
1476 || (bidi_it->next_en_pos > bidi_it->charpos
1477 && bidi_it->next_en_type == WEAK_EN))
1478 type = WEAK_EN;
1479 break;
1480 case PDF: /* X7 */
1481 bidi_it->type_after_w1 = type;
1482 bidi_check_type (bidi_it->type_after_w1);
1483 type = WEAK_BN; /* X9/Retaining */
1484 if (bidi_it->ignore_bn_limit <= -1)
1486 if (!bidi_it->invalid_rl_levels)
1488 new_level = bidi_pop_embedding_level (bidi_it);
1489 bidi_it->invalid_rl_levels = -1;
1490 if (bidi_it->invalid_levels)
1491 bidi_it->invalid_levels--;
1492 /* else nothing: UAX#9 says to ignore invalid PDFs */
1494 if (!bidi_it->invalid_levels)
1495 new_level = bidi_pop_embedding_level (bidi_it);
1496 else
1498 bidi_it->invalid_levels--;
1499 bidi_it->invalid_rl_levels--;
1502 else if (bidi_it->prev.type_after_w1 == WEAK_EN /* W5/Retaining */
1503 || (bidi_it->next_en_pos > bidi_it->charpos
1504 && bidi_it->next_en_type == WEAK_EN))
1505 type = WEAK_EN;
1506 break;
1507 default:
1508 /* Nothing. */
1509 break;
1512 bidi_it->type = type;
1513 bidi_check_type (bidi_it->type);
1515 return new_level;
1518 /* Given an iterator state in BIDI_IT, advance one character position
1519 in the buffer/string to the next character (in the logical order),
1520 resolve any explicit embeddings and directional overrides, and
1521 return the embedding level of the character after resolving
1522 explicit directives and ignoring empty embeddings. */
1523 static int
1524 bidi_resolve_explicit (struct bidi_it *bidi_it)
1526 int prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
1527 int new_level = bidi_resolve_explicit_1 (bidi_it);
1528 EMACS_INT eob = bidi_it->string.s ? bidi_it->string.schars : ZV;
1529 const unsigned char *s
1530 = (STRINGP (bidi_it->string.lstring)
1531 ? SDATA (bidi_it->string.lstring)
1532 : bidi_it->string.s);
1534 if (prev_level < new_level
1535 && bidi_it->type == WEAK_BN
1536 && bidi_it->ignore_bn_limit == -1 /* only if not already known */
1537 && bidi_it->charpos < eob /* not already at EOB */
1538 && bidi_explicit_dir_char (bidi_char_at_pos (bidi_it->bytepos
1539 + bidi_it->ch_len, s,
1540 bidi_it->string.unibyte)))
1542 /* Avoid pushing and popping embedding levels if the level run
1543 is empty, as this breaks level runs where it shouldn't.
1544 UAX#9 removes all the explicit embedding and override codes,
1545 so empty embeddings disappear without a trace. We need to
1546 behave as if we did the same. */
1547 struct bidi_it saved_it;
1548 int level = prev_level;
1550 bidi_copy_it (&saved_it, bidi_it);
1552 while (bidi_explicit_dir_char (bidi_char_at_pos (bidi_it->bytepos
1553 + bidi_it->ch_len, s,
1554 bidi_it->string.unibyte)))
1556 /* This advances to the next character, skipping any
1557 characters covered by display strings. */
1558 level = bidi_resolve_explicit_1 (bidi_it);
1559 /* If string.lstring was relocated inside bidi_resolve_explicit_1,
1560 a pointer to its data is no longer valid. */
1561 if (STRINGP (bidi_it->string.lstring))
1562 s = SDATA (bidi_it->string.lstring);
1565 if (bidi_it->nchars <= 0)
1566 abort ();
1567 if (level == prev_level) /* empty embedding */
1568 saved_it.ignore_bn_limit = bidi_it->charpos + bidi_it->nchars;
1569 else /* this embedding is non-empty */
1570 saved_it.ignore_bn_limit = -2;
1572 bidi_copy_it (bidi_it, &saved_it);
1573 if (bidi_it->ignore_bn_limit > -1)
1575 /* We pushed a level, but we shouldn't have. Undo that. */
1576 if (!bidi_it->invalid_rl_levels)
1578 new_level = bidi_pop_embedding_level (bidi_it);
1579 bidi_it->invalid_rl_levels = -1;
1580 if (bidi_it->invalid_levels)
1581 bidi_it->invalid_levels--;
1583 if (!bidi_it->invalid_levels)
1584 new_level = bidi_pop_embedding_level (bidi_it);
1585 else
1587 bidi_it->invalid_levels--;
1588 bidi_it->invalid_rl_levels--;
1593 if (bidi_it->type == NEUTRAL_B) /* X8 */
1595 bidi_set_paragraph_end (bidi_it);
1596 /* This is needed by bidi_resolve_weak below, and in L1. */
1597 bidi_it->type_after_w1 = bidi_it->type;
1598 bidi_check_type (bidi_it->type_after_w1);
1601 return new_level;
1604 /* Advance in the buffer/string, resolve weak types and return the
1605 type of the next character after weak type resolution. */
1606 static bidi_type_t
1607 bidi_resolve_weak (struct bidi_it *bidi_it)
1609 bidi_type_t type;
1610 bidi_dir_t override;
1611 int prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
1612 int new_level = bidi_resolve_explicit (bidi_it);
1613 int next_char;
1614 bidi_type_t type_of_next;
1615 struct bidi_it saved_it;
1616 EMACS_INT eob
1617 = ((STRINGP (bidi_it->string.lstring) || bidi_it->string.s)
1618 ? bidi_it->string.schars : ZV);
1620 type = bidi_it->type;
1621 override = bidi_it->level_stack[bidi_it->stack_idx].override;
1623 if (type == UNKNOWN_BT
1624 || type == LRE
1625 || type == LRO
1626 || type == RLE
1627 || type == RLO
1628 || type == PDF)
1629 abort ();
1631 if (new_level != prev_level
1632 || bidi_it->type == NEUTRAL_B)
1634 /* We've got a new embedding level run, compute the directional
1635 type of sor and initialize per-run variables (UAX#9, clause
1636 X10). */
1637 bidi_set_sor_type (bidi_it, prev_level, new_level);
1639 else if (type == NEUTRAL_S || type == NEUTRAL_WS
1640 || type == WEAK_BN || type == STRONG_AL)
1641 bidi_it->type_after_w1 = type; /* needed in L1 */
1642 bidi_check_type (bidi_it->type_after_w1);
1644 /* Level and directional override status are already recorded in
1645 bidi_it, and do not need any change; see X6. */
1646 if (override == R2L) /* X6 */
1647 type = STRONG_R;
1648 else if (override == L2R)
1649 type = STRONG_L;
1650 else
1652 if (type == WEAK_NSM) /* W1 */
1654 /* Note that we don't need to consider the case where the
1655 prev character has its type overridden by an RLO or LRO,
1656 because then either the type of this NSM would have been
1657 also overridden, or the previous character is outside the
1658 current level run, and thus not relevant to this NSM.
1659 This is why NSM gets the type_after_w1 of the previous
1660 character. */
1661 if (bidi_it->prev.type_after_w1 != UNKNOWN_BT
1662 /* if type_after_w1 is NEUTRAL_B, this NSM is at sor */
1663 && bidi_it->prev.type_after_w1 != NEUTRAL_B)
1664 type = bidi_it->prev.type_after_w1;
1665 else if (bidi_it->sor == R2L)
1666 type = STRONG_R;
1667 else if (bidi_it->sor == L2R)
1668 type = STRONG_L;
1669 else /* shouldn't happen! */
1670 abort ();
1672 if (type == WEAK_EN /* W2 */
1673 && bidi_it->last_strong.type_after_w1 == STRONG_AL)
1674 type = WEAK_AN;
1675 else if (type == STRONG_AL) /* W3 */
1676 type = STRONG_R;
1677 else if ((type == WEAK_ES /* W4 */
1678 && bidi_it->prev.type_after_w1 == WEAK_EN
1679 && bidi_it->prev.orig_type == WEAK_EN)
1680 || (type == WEAK_CS
1681 && ((bidi_it->prev.type_after_w1 == WEAK_EN
1682 && bidi_it->prev.orig_type == WEAK_EN)
1683 || bidi_it->prev.type_after_w1 == WEAK_AN)))
1685 const unsigned char *s
1686 = (STRINGP (bidi_it->string.lstring)
1687 ? SDATA (bidi_it->string.lstring)
1688 : bidi_it->string.s);
1690 next_char = (bidi_it->charpos + bidi_it->nchars >= eob
1691 ? BIDI_EOB
1692 : bidi_char_at_pos (bidi_it->bytepos + bidi_it->ch_len,
1693 s, bidi_it->string.unibyte));
1694 type_of_next = bidi_get_type (next_char, override);
1696 if (type_of_next == WEAK_BN
1697 || bidi_explicit_dir_char (next_char))
1699 bidi_copy_it (&saved_it, bidi_it);
1700 while (bidi_resolve_explicit (bidi_it) == new_level
1701 && bidi_it->type == WEAK_BN)
1703 type_of_next = bidi_it->type;
1704 bidi_copy_it (bidi_it, &saved_it);
1707 /* If the next character is EN, but the last strong-type
1708 character is AL, that next EN will be changed to AN when
1709 we process it in W2 above. So in that case, this ES
1710 should not be changed into EN. */
1711 if (type == WEAK_ES
1712 && type_of_next == WEAK_EN
1713 && bidi_it->last_strong.type_after_w1 != STRONG_AL)
1714 type = WEAK_EN;
1715 else if (type == WEAK_CS)
1717 if (bidi_it->prev.type_after_w1 == WEAK_AN
1718 && (type_of_next == WEAK_AN
1719 /* If the next character is EN, but the last
1720 strong-type character is AL, EN will be later
1721 changed to AN when we process it in W2 above.
1722 So in that case, this ES should not be
1723 changed into EN. */
1724 || (type_of_next == WEAK_EN
1725 && bidi_it->last_strong.type_after_w1 == STRONG_AL)))
1726 type = WEAK_AN;
1727 else if (bidi_it->prev.type_after_w1 == WEAK_EN
1728 && type_of_next == WEAK_EN
1729 && bidi_it->last_strong.type_after_w1 != STRONG_AL)
1730 type = WEAK_EN;
1733 else if (type == WEAK_ET /* W5: ET with EN before or after it */
1734 || type == WEAK_BN) /* W5/Retaining */
1736 if (bidi_it->prev.type_after_w1 == WEAK_EN) /* ET/BN w/EN before it */
1737 type = WEAK_EN;
1738 else if (bidi_it->next_en_pos > bidi_it->charpos
1739 && bidi_it->next_en_type != WEAK_BN)
1741 if (bidi_it->next_en_type == WEAK_EN) /* ET/BN with EN after it */
1742 type = WEAK_EN;
1744 else if (bidi_it->next_en_pos >=0)
1746 EMACS_INT en_pos = bidi_it->charpos + bidi_it->nchars;
1747 const unsigned char *s = (STRINGP (bidi_it->string.lstring)
1748 ? SDATA (bidi_it->string.lstring)
1749 : bidi_it->string.s);
1751 if (bidi_it->nchars <= 0)
1752 abort ();
1753 next_char
1754 = (bidi_it->charpos + bidi_it->nchars >= eob
1755 ? BIDI_EOB
1756 : bidi_char_at_pos (bidi_it->bytepos + bidi_it->ch_len, s,
1757 bidi_it->string.unibyte));
1758 type_of_next = bidi_get_type (next_char, override);
1760 if (type_of_next == WEAK_ET
1761 || type_of_next == WEAK_BN
1762 || bidi_explicit_dir_char (next_char))
1764 bidi_copy_it (&saved_it, bidi_it);
1765 while (bidi_resolve_explicit (bidi_it) == new_level
1766 && (bidi_it->type == WEAK_BN
1767 || bidi_it->type == WEAK_ET))
1769 type_of_next = bidi_it->type;
1770 en_pos = bidi_it->charpos;
1771 bidi_copy_it (bidi_it, &saved_it);
1773 /* Remember this position, to speed up processing of the
1774 next ETs. */
1775 bidi_it->next_en_pos = en_pos;
1776 if (type_of_next == WEAK_EN)
1778 /* If the last strong character is AL, the EN we've
1779 found will become AN when we get to it (W2). */
1780 if (bidi_it->last_strong.type_after_w1 == STRONG_AL)
1781 type_of_next = WEAK_AN;
1782 else if (type == WEAK_BN)
1783 type = NEUTRAL_ON; /* W6/Retaining */
1784 else
1785 type = WEAK_EN;
1787 else if (type_of_next == NEUTRAL_B)
1788 /* Record the fact that there are no more ENs from
1789 here to the end of paragraph, to avoid entering the
1790 loop above ever again in this paragraph. */
1791 bidi_it->next_en_pos = -1;
1792 /* Record the type of the character where we ended our search. */
1793 bidi_it->next_en_type = type_of_next;
1798 if (type == WEAK_ES || type == WEAK_ET || type == WEAK_CS /* W6 */
1799 || (type == WEAK_BN
1800 && (bidi_it->prev.type_after_w1 == WEAK_CS /* W6/Retaining */
1801 || bidi_it->prev.type_after_w1 == WEAK_ES
1802 || bidi_it->prev.type_after_w1 == WEAK_ET)))
1803 type = NEUTRAL_ON;
1805 /* Store the type we've got so far, before we clobber it with strong
1806 types in W7 and while resolving neutral types. But leave alone
1807 the original types that were recorded above, because we will need
1808 them for the L1 clause. */
1809 if (bidi_it->type_after_w1 == UNKNOWN_BT)
1810 bidi_it->type_after_w1 = type;
1811 bidi_check_type (bidi_it->type_after_w1);
1813 if (type == WEAK_EN) /* W7 */
1815 if ((bidi_it->last_strong.type_after_w1 == STRONG_L)
1816 || (bidi_it->last_strong.type == UNKNOWN_BT && bidi_it->sor == L2R))
1817 type = STRONG_L;
1820 bidi_it->type = type;
1821 bidi_check_type (bidi_it->type);
1822 return type;
1825 /* Resolve the type of a neutral character according to the type of
1826 surrounding strong text and the current embedding level. */
1827 static inline bidi_type_t
1828 bidi_resolve_neutral_1 (bidi_type_t prev_type, bidi_type_t next_type, int lev)
1830 /* N1: European and Arabic numbers are treated as though they were R. */
1831 if (next_type == WEAK_EN || next_type == WEAK_AN)
1832 next_type = STRONG_R;
1833 if (prev_type == WEAK_EN || prev_type == WEAK_AN)
1834 prev_type = STRONG_R;
1836 if (next_type == prev_type) /* N1 */
1837 return next_type;
1838 else if ((lev & 1) == 0) /* N2 */
1839 return STRONG_L;
1840 else
1841 return STRONG_R;
1844 static bidi_type_t
1845 bidi_resolve_neutral (struct bidi_it *bidi_it)
1847 int prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
1848 bidi_type_t type = bidi_resolve_weak (bidi_it);
1849 int current_level = bidi_it->level_stack[bidi_it->stack_idx].level;
1851 if (!(type == STRONG_R
1852 || type == STRONG_L
1853 || type == WEAK_BN
1854 || type == WEAK_EN
1855 || type == WEAK_AN
1856 || type == NEUTRAL_B
1857 || type == NEUTRAL_S
1858 || type == NEUTRAL_WS
1859 || type == NEUTRAL_ON))
1860 abort ();
1862 if ((type != NEUTRAL_B /* Don't risk entering the long loop below if
1863 we are already at paragraph end. */
1864 && bidi_get_category (type) == NEUTRAL)
1865 || (type == WEAK_BN && prev_level == current_level))
1867 if (bidi_it->next_for_neutral.type != UNKNOWN_BT)
1868 type = bidi_resolve_neutral_1 (bidi_it->prev_for_neutral.type,
1869 bidi_it->next_for_neutral.type,
1870 current_level);
1871 /* The next two "else if" clauses are shortcuts for the
1872 important special case when we have a long sequence of
1873 neutral or WEAK_BN characters, such as whitespace or nulls or
1874 other control characters, on the base embedding level of the
1875 paragraph, and that sequence goes all the way to the end of
1876 the paragraph and follows a character whose resolved
1877 directionality is identical to the base embedding level.
1878 (This is what happens in a buffer with plain L2R text that
1879 happens to include long sequences of control characters.) By
1880 virtue of N1, the result of examining this long sequence will
1881 always be either STRONG_L or STRONG_R, depending on the base
1882 embedding level. So we use this fact directly instead of
1883 entering the expensive loop in the "else" clause. */
1884 else if (current_level == 0
1885 && bidi_it->prev_for_neutral.type == STRONG_L
1886 && !bidi_explicit_dir_char (bidi_it->ch))
1887 type = bidi_resolve_neutral_1 (bidi_it->prev_for_neutral.type,
1888 STRONG_L, current_level);
1889 else if (/* current level is 1 */
1890 current_level == 1
1891 /* base embedding level is also 1 */
1892 && bidi_it->level_stack[0].level == 1
1893 /* previous character is one of those considered R for
1894 the purposes of W5 */
1895 && (bidi_it->prev_for_neutral.type == STRONG_R
1896 || bidi_it->prev_for_neutral.type == WEAK_EN
1897 || bidi_it->prev_for_neutral.type == WEAK_AN)
1898 && !bidi_explicit_dir_char (bidi_it->ch))
1899 type = bidi_resolve_neutral_1 (bidi_it->prev_for_neutral.type,
1900 STRONG_R, current_level);
1901 else
1903 /* Arrrgh!! The UAX#9 algorithm is too deeply entrenched in
1904 the assumption of batch-style processing; see clauses W4,
1905 W5, and especially N1, which require to look far forward
1906 (as well as back) in the buffer/string. May the fleas of
1907 a thousand camels infest the armpits of those who design
1908 supposedly general-purpose algorithms by looking at their
1909 own implementations, and fail to consider other possible
1910 implementations! */
1911 struct bidi_it saved_it;
1912 bidi_type_t next_type;
1914 if (bidi_it->scan_dir == -1)
1915 abort ();
1917 bidi_copy_it (&saved_it, bidi_it);
1918 /* Scan the text forward until we find the first non-neutral
1919 character, and then use that to resolve the neutral we
1920 are dealing with now. We also cache the scanned iterator
1921 states, to salvage some of the effort later. */
1922 bidi_cache_iterator_state (bidi_it, 0);
1923 do {
1924 /* Record the info about the previous character, so that
1925 it will be cached below with this state. */
1926 if (bidi_it->type_after_w1 != WEAK_BN /* W1/Retaining */
1927 && bidi_it->type != WEAK_BN)
1928 bidi_remember_char (&bidi_it->prev, bidi_it);
1929 type = bidi_resolve_weak (bidi_it);
1930 /* Paragraph separators have their levels fully resolved
1931 at this point, so cache them as resolved. */
1932 bidi_cache_iterator_state (bidi_it, type == NEUTRAL_B);
1933 /* FIXME: implement L1 here, by testing for a newline and
1934 resetting the level for any sequence of whitespace
1935 characters adjacent to it. */
1936 } while (!(type == NEUTRAL_B
1937 || (type != WEAK_BN
1938 && bidi_get_category (type) != NEUTRAL)
1939 /* This is all per level run, so stop when we
1940 reach the end of this level run. */
1941 || (bidi_it->level_stack[bidi_it->stack_idx].level
1942 != current_level)));
1944 bidi_remember_char (&saved_it.next_for_neutral, bidi_it);
1946 switch (type)
1948 case STRONG_L:
1949 case STRONG_R:
1950 case STRONG_AL:
1951 /* Actually, STRONG_AL cannot happen here, because
1952 bidi_resolve_weak converts it to STRONG_R, per W3. */
1953 xassert (type != STRONG_AL);
1954 next_type = type;
1955 break;
1956 case WEAK_EN:
1957 case WEAK_AN:
1958 /* N1: ``European and Arabic numbers are treated as
1959 though they were R.'' */
1960 next_type = STRONG_R;
1961 break;
1962 case WEAK_BN:
1963 if (!bidi_explicit_dir_char (bidi_it->ch))
1964 abort (); /* can't happen: BNs are skipped */
1965 /* FALLTHROUGH */
1966 case NEUTRAL_B:
1967 /* Marched all the way to the end of this level run.
1968 We need to use the eor type, whose information is
1969 stored by bidi_set_sor_type in the prev_for_neutral
1970 member. */
1971 if (saved_it.type != WEAK_BN
1972 || bidi_get_category (bidi_it->prev.type_after_w1) == NEUTRAL)
1973 next_type = bidi_it->prev_for_neutral.type;
1974 else
1976 /* This is a BN which does not adjoin neutrals.
1977 Leave its type alone. */
1978 bidi_copy_it (bidi_it, &saved_it);
1979 return bidi_it->type;
1981 break;
1982 default:
1983 abort ();
1985 type = bidi_resolve_neutral_1 (saved_it.prev_for_neutral.type,
1986 next_type, current_level);
1987 saved_it.next_for_neutral.type = next_type;
1988 saved_it.type = type;
1989 bidi_check_type (next_type);
1990 bidi_check_type (type);
1991 bidi_copy_it (bidi_it, &saved_it);
1994 return type;
1997 /* Given an iterator state in BIDI_IT, advance one character position
1998 in the buffer/string to the next character (in the logical order),
1999 resolve the bidi type of that next character, and return that
2000 type. */
2001 static bidi_type_t
2002 bidi_type_of_next_char (struct bidi_it *bidi_it)
2004 bidi_type_t type;
2006 /* This should always be called during a forward scan. */
2007 if (bidi_it->scan_dir != 1)
2008 abort ();
2010 /* Reset the limit until which to ignore BNs if we step out of the
2011 area where we found only empty levels. */
2012 if ((bidi_it->ignore_bn_limit > -1
2013 && bidi_it->ignore_bn_limit <= bidi_it->charpos)
2014 || (bidi_it->ignore_bn_limit == -2
2015 && !bidi_explicit_dir_char (bidi_it->ch)))
2016 bidi_it->ignore_bn_limit = -1;
2018 type = bidi_resolve_neutral (bidi_it);
2020 return type;
2023 /* Given an iterator state BIDI_IT, advance one character position in
2024 the buffer/string to the next character (in the current scan
2025 direction), resolve the embedding and implicit levels of that next
2026 character, and return the resulting level. */
2027 static int
2028 bidi_level_of_next_char (struct bidi_it *bidi_it)
2030 bidi_type_t type;
2031 int level, prev_level = -1;
2032 struct bidi_saved_info next_for_neutral;
2033 EMACS_INT next_char_pos = -2;
2035 if (bidi_it->scan_dir == 1)
2037 EMACS_INT eob
2038 = ((bidi_it->string.s || STRINGP (bidi_it->string.lstring))
2039 ? bidi_it->string.schars : ZV);
2041 /* There's no sense in trying to advance if we hit end of text. */
2042 if (bidi_it->charpos >= eob)
2043 return bidi_it->resolved_level;
2045 /* Record the info about the previous character. */
2046 if (bidi_it->type_after_w1 != WEAK_BN /* W1/Retaining */
2047 && bidi_it->type != WEAK_BN)
2048 bidi_remember_char (&bidi_it->prev, bidi_it);
2049 if (bidi_it->type_after_w1 == STRONG_R
2050 || bidi_it->type_after_w1 == STRONG_L
2051 || bidi_it->type_after_w1 == STRONG_AL)
2052 bidi_remember_char (&bidi_it->last_strong, bidi_it);
2053 /* FIXME: it sounds like we don't need both prev and
2054 prev_for_neutral members, but I'm leaving them both for now. */
2055 if (bidi_it->type == STRONG_R || bidi_it->type == STRONG_L
2056 || bidi_it->type == WEAK_EN || bidi_it->type == WEAK_AN)
2057 bidi_remember_char (&bidi_it->prev_for_neutral, bidi_it);
2059 /* If we overstepped the characters used for resolving neutrals
2060 and whitespace, invalidate their info in the iterator. */
2061 if (bidi_it->charpos >= bidi_it->next_for_neutral.charpos)
2062 bidi_it->next_for_neutral.type = UNKNOWN_BT;
2063 if (bidi_it->next_en_pos >= 0
2064 && bidi_it->charpos >= bidi_it->next_en_pos)
2066 bidi_it->next_en_pos = 0;
2067 bidi_it->next_en_type = UNKNOWN_BT;
2069 if (bidi_it->next_for_ws.type != UNKNOWN_BT
2070 && bidi_it->charpos >= bidi_it->next_for_ws.charpos)
2071 bidi_it->next_for_ws.type = UNKNOWN_BT;
2073 /* This must be taken before we fill the iterator with the info
2074 about the next char. If we scan backwards, the iterator
2075 state must be already cached, so there's no need to know the
2076 embedding level of the previous character, since we will be
2077 returning to our caller shortly. */
2078 prev_level = bidi_it->level_stack[bidi_it->stack_idx].level;
2080 next_for_neutral = bidi_it->next_for_neutral;
2082 /* Perhaps the character we want is already cached. If it is, the
2083 call to bidi_cache_find below will return a type other than
2084 UNKNOWN_BT. */
2085 if (bidi_cache_idx > bidi_cache_start && !bidi_it->first_elt)
2087 int bob = ((bidi_it->string.s || STRINGP (bidi_it->string.lstring))
2088 ? 0 : 1);
2089 if (bidi_it->scan_dir > 0)
2091 if (bidi_it->nchars <= 0)
2092 abort ();
2093 next_char_pos = bidi_it->charpos + bidi_it->nchars;
2095 else if (bidi_it->charpos >= bob)
2096 /* Implementation note: we allow next_char_pos to be as low as
2097 0 for buffers or -1 for strings, and that is okay because
2098 that's the "position" of the sentinel iterator state we
2099 cached at the beginning of the iteration. */
2100 next_char_pos = bidi_it->charpos - 1;
2101 if (next_char_pos >= bob - 1)
2102 type = bidi_cache_find (next_char_pos, -1, bidi_it);
2103 else
2104 type = UNKNOWN_BT;
2106 else
2107 type = UNKNOWN_BT;
2108 if (type != UNKNOWN_BT)
2110 /* Don't lose the information for resolving neutrals! The
2111 cached states could have been cached before their
2112 next_for_neutral member was computed. If we are on our way
2113 forward, we can simply take the info from the previous
2114 state. */
2115 if (bidi_it->scan_dir == 1
2116 && bidi_it->next_for_neutral.type == UNKNOWN_BT)
2117 bidi_it->next_for_neutral = next_for_neutral;
2119 /* If resolved_level is -1, it means this state was cached
2120 before it was completely resolved, so we cannot return
2121 it. */
2122 if (bidi_it->resolved_level != -1)
2123 return bidi_it->resolved_level;
2125 if (bidi_it->scan_dir == -1)
2126 /* If we are going backwards, the iterator state is already cached
2127 from previous scans, and should be fully resolved. */
2128 abort ();
2130 if (type == UNKNOWN_BT)
2131 type = bidi_type_of_next_char (bidi_it);
2133 if (type == NEUTRAL_B)
2134 return bidi_it->resolved_level;
2136 level = bidi_it->level_stack[bidi_it->stack_idx].level;
2137 if ((bidi_get_category (type) == NEUTRAL /* && type != NEUTRAL_B */)
2138 || (type == WEAK_BN && prev_level == level))
2140 if (bidi_it->next_for_neutral.type == UNKNOWN_BT)
2141 abort ();
2143 /* If the cached state shows a neutral character, it was not
2144 resolved by bidi_resolve_neutral, so do it now. */
2145 type = bidi_resolve_neutral_1 (bidi_it->prev_for_neutral.type,
2146 bidi_it->next_for_neutral.type,
2147 level);
2150 if (!(type == STRONG_R
2151 || type == STRONG_L
2152 || type == WEAK_BN
2153 || type == WEAK_EN
2154 || type == WEAK_AN))
2155 abort ();
2156 bidi_it->type = type;
2157 bidi_check_type (bidi_it->type);
2159 /* For L1 below, we need to know, for each WS character, whether
2160 it belongs to a sequence of WS characters preceding a newline
2161 or a TAB or a paragraph separator. */
2162 if (bidi_it->orig_type == NEUTRAL_WS
2163 && bidi_it->next_for_ws.type == UNKNOWN_BT)
2165 int ch;
2166 EMACS_INT clen = bidi_it->ch_len;
2167 EMACS_INT bpos = bidi_it->bytepos;
2168 EMACS_INT cpos = bidi_it->charpos;
2169 EMACS_INT disp_pos = bidi_it->disp_pos;
2170 EMACS_INT nc = bidi_it->nchars;
2171 struct bidi_string_data bs = bidi_it->string;
2172 bidi_type_t chtype;
2173 int fwp = bidi_it->frame_window_p;
2174 int dpp = bidi_it->disp_prop;
2176 if (bidi_it->nchars <= 0)
2177 abort ();
2178 do {
2179 ch = bidi_fetch_char (bpos += clen, cpos += nc, &disp_pos, &dpp, &bs,
2180 fwp, &clen, &nc);
2181 if (ch == '\n' || ch == BIDI_EOB)
2182 chtype = NEUTRAL_B;
2183 else
2184 chtype = bidi_get_type (ch, NEUTRAL_DIR);
2185 } while (chtype == NEUTRAL_WS || chtype == WEAK_BN
2186 || bidi_explicit_dir_char (ch)); /* L1/Retaining */
2187 bidi_it->next_for_ws.type = chtype;
2188 bidi_check_type (bidi_it->next_for_ws.type);
2189 bidi_it->next_for_ws.charpos = cpos;
2190 bidi_it->next_for_ws.bytepos = bpos;
2193 /* Resolve implicit levels, with a twist: PDFs get the embedding
2194 level of the embedding they terminate. See below for the
2195 reason. */
2196 if (bidi_it->orig_type == PDF
2197 /* Don't do this if this formatting code didn't change the
2198 embedding level due to invalid or empty embeddings. */
2199 && prev_level != level)
2201 /* Don't look in UAX#9 for the reason for this: it's our own
2202 private quirk. The reason is that we want the formatting
2203 codes to be delivered so that they bracket the text of their
2204 embedding. For example, given the text
2206 {RLO}teST{PDF}
2208 we want it to be displayed as
2210 {PDF}STet{RLO}
2212 not as
2214 STet{RLO}{PDF}
2216 which will result because we bump up the embedding level as
2217 soon as we see the RLO and pop it as soon as we see the PDF,
2218 so RLO itself has the same embedding level as "teST", and
2219 thus would be normally delivered last, just before the PDF.
2220 The switch below fiddles with the level of PDF so that this
2221 ugly side effect does not happen.
2223 (This is, of course, only important if the formatting codes
2224 are actually displayed, but Emacs does need to display them
2225 if the user wants to.) */
2226 level = prev_level;
2228 else if (bidi_it->orig_type == NEUTRAL_B /* L1 */
2229 || bidi_it->orig_type == NEUTRAL_S
2230 || bidi_it->ch == '\n' || bidi_it->ch == BIDI_EOB
2231 || (bidi_it->orig_type == NEUTRAL_WS
2232 && (bidi_it->next_for_ws.type == NEUTRAL_B
2233 || bidi_it->next_for_ws.type == NEUTRAL_S)))
2234 level = bidi_it->level_stack[0].level;
2235 else if ((level & 1) == 0) /* I1 */
2237 if (type == STRONG_R)
2238 level++;
2239 else if (type == WEAK_EN || type == WEAK_AN)
2240 level += 2;
2242 else /* I2 */
2244 if (type == STRONG_L || type == WEAK_EN || type == WEAK_AN)
2245 level++;
2248 bidi_it->resolved_level = level;
2249 return level;
2252 /* Move to the other edge of a level given by LEVEL. If END_FLAG is
2253 non-zero, we are at the end of a level, and we need to prepare to
2254 resume the scan of the lower level.
2256 If this level's other edge is cached, we simply jump to it, filling
2257 the iterator structure with the iterator state on the other edge.
2258 Otherwise, we walk the buffer or string until we come back to the
2259 same level as LEVEL.
2261 Note: we are not talking here about a ``level run'' in the UAX#9
2262 sense of the term, but rather about a ``level'' which includes
2263 all the levels higher than it. In other words, given the levels
2264 like this:
2266 11111112222222333333334443343222222111111112223322111
2267 A B C
2269 and assuming we are at point A scanning left to right, this
2270 function moves to point C, whereas the UAX#9 ``level 2 run'' ends
2271 at point B. */
2272 static void
2273 bidi_find_other_level_edge (struct bidi_it *bidi_it, int level, int end_flag)
2275 int dir = end_flag ? -bidi_it->scan_dir : bidi_it->scan_dir;
2276 ptrdiff_t idx;
2278 /* Try the cache first. */
2279 if ((idx = bidi_cache_find_level_change (level, dir, end_flag))
2280 >= bidi_cache_start)
2281 bidi_cache_fetch_state (idx, bidi_it);
2282 else
2284 int new_level;
2286 if (end_flag)
2287 abort (); /* if we are at end of level, its edges must be cached */
2289 bidi_cache_iterator_state (bidi_it, 1);
2290 do {
2291 new_level = bidi_level_of_next_char (bidi_it);
2292 bidi_cache_iterator_state (bidi_it, 1);
2293 } while (new_level >= level);
2297 void
2298 bidi_move_to_visually_next (struct bidi_it *bidi_it)
2300 int old_level, new_level, next_level;
2301 struct bidi_it sentinel;
2302 struct gcpro gcpro1;
2304 if (bidi_it->charpos < 0 || bidi_it->bytepos < 0)
2305 abort ();
2307 if (bidi_it->scan_dir == 0)
2309 bidi_it->scan_dir = 1; /* default to logical order */
2312 /* The code below can call eval, and thus cause GC. If we are
2313 iterating a Lisp string, make sure it won't be GCed. */
2314 if (STRINGP (bidi_it->string.lstring))
2315 GCPRO1 (bidi_it->string.lstring);
2317 /* If we just passed a newline, initialize for the next line. */
2318 if (!bidi_it->first_elt
2319 && (bidi_it->ch == '\n' || bidi_it->ch == BIDI_EOB))
2320 bidi_line_init (bidi_it);
2322 /* Prepare the sentinel iterator state, and cache it. When we bump
2323 into it, scanning backwards, we'll know that the last non-base
2324 level is exhausted. */
2325 if (bidi_cache_idx == bidi_cache_start)
2327 bidi_copy_it (&sentinel, bidi_it);
2328 if (bidi_it->first_elt)
2330 sentinel.charpos--; /* cached charpos needs to be monotonic */
2331 sentinel.bytepos--;
2332 sentinel.ch = '\n'; /* doesn't matter, but why not? */
2333 sentinel.ch_len = 1;
2334 sentinel.nchars = 1;
2336 bidi_cache_iterator_state (&sentinel, 1);
2339 old_level = bidi_it->resolved_level;
2340 new_level = bidi_level_of_next_char (bidi_it);
2342 /* Reordering of resolved levels (clause L2) is implemented by
2343 jumping to the other edge of the level and flipping direction of
2344 scanning the text whenever we find a level change. */
2345 if (new_level != old_level)
2347 int ascending = new_level > old_level;
2348 int level_to_search = ascending ? old_level + 1 : old_level;
2349 int incr = ascending ? 1 : -1;
2350 int expected_next_level = old_level + incr;
2352 /* Jump (or walk) to the other edge of this level. */
2353 bidi_find_other_level_edge (bidi_it, level_to_search, !ascending);
2354 /* Switch scan direction and peek at the next character in the
2355 new direction. */
2356 bidi_it->scan_dir = -bidi_it->scan_dir;
2358 /* The following loop handles the case where the resolved level
2359 jumps by more than one. This is typical for numbers inside a
2360 run of text with left-to-right embedding direction, but can
2361 also happen in other situations. In those cases the decision
2362 where to continue after a level change, and in what direction,
2363 is tricky. For example, given a text like below:
2365 abcdefgh
2366 11336622
2368 (where the numbers below the text show the resolved levels),
2369 the result of reordering according to UAX#9 should be this:
2371 efdcghba
2373 This is implemented by the loop below which flips direction
2374 and jumps to the other edge of the level each time it finds
2375 the new level not to be the expected one. The expected level
2376 is always one more or one less than the previous one. */
2377 next_level = bidi_peek_at_next_level (bidi_it);
2378 while (next_level != expected_next_level)
2380 expected_next_level += incr;
2381 level_to_search += incr;
2382 bidi_find_other_level_edge (bidi_it, level_to_search, !ascending);
2383 bidi_it->scan_dir = -bidi_it->scan_dir;
2384 next_level = bidi_peek_at_next_level (bidi_it);
2387 /* Finally, deliver the next character in the new direction. */
2388 next_level = bidi_level_of_next_char (bidi_it);
2391 /* Take note when we have just processed the newline that precedes
2392 the end of the paragraph. The next time we are about to be
2393 called, set_iterator_to_next will automatically reinit the
2394 paragraph direction, if needed. We do this at the newline before
2395 the paragraph separator, because the next character might not be
2396 the first character of the next paragraph, due to the bidi
2397 reordering, whereas we _must_ know the paragraph base direction
2398 _before_ we process the paragraph's text, since the base
2399 direction affects the reordering. */
2400 if (bidi_it->scan_dir == 1
2401 && (bidi_it->ch == '\n' || bidi_it->ch == BIDI_EOB))
2403 /* The paragraph direction of the entire string, once
2404 determined, is in effect for the entire string. Setting the
2405 separator limit to the end of the string prevents
2406 bidi_paragraph_init from being called automatically on this
2407 string. */
2408 if (bidi_it->string.s || STRINGP (bidi_it->string.lstring))
2409 bidi_it->separator_limit = bidi_it->string.schars;
2410 else if (bidi_it->bytepos < ZV_BYTE)
2412 EMACS_INT sep_len
2413 = bidi_at_paragraph_end (bidi_it->charpos + bidi_it->nchars,
2414 bidi_it->bytepos + bidi_it->ch_len);
2415 if (bidi_it->nchars <= 0)
2416 abort ();
2417 if (sep_len >= 0)
2419 bidi_it->new_paragraph = 1;
2420 /* Record the buffer position of the last character of the
2421 paragraph separator. */
2422 bidi_it->separator_limit
2423 = bidi_it->charpos + bidi_it->nchars + sep_len;
2428 if (bidi_it->scan_dir == 1 && bidi_cache_idx > bidi_cache_start)
2430 /* If we are at paragraph's base embedding level and beyond the
2431 last cached position, the cache's job is done and we can
2432 discard it. */
2433 if (bidi_it->resolved_level == bidi_it->level_stack[0].level
2434 && bidi_it->charpos > (bidi_cache[bidi_cache_idx - 1].charpos
2435 + bidi_cache[bidi_cache_idx - 1].nchars - 1))
2436 bidi_cache_reset ();
2437 /* But as long as we are caching during forward scan, we must
2438 cache each state, or else the cache integrity will be
2439 compromised: it assumes cached states correspond to buffer
2440 positions 1:1. */
2441 else
2442 bidi_cache_iterator_state (bidi_it, 1);
2445 if (STRINGP (bidi_it->string.lstring))
2446 UNGCPRO;
2449 /* This is meant to be called from within the debugger, whenever you
2450 wish to examine the cache contents. */
2451 void bidi_dump_cached_states (void) EXTERNALLY_VISIBLE;
2452 void
2453 bidi_dump_cached_states (void)
2455 ptrdiff_t i;
2456 int ndigits = 1;
2458 if (bidi_cache_idx == 0)
2460 fprintf (stderr, "The cache is empty.\n");
2461 return;
2463 fprintf (stderr, "Total of %"pD"d state%s in cache:\n",
2464 bidi_cache_idx, bidi_cache_idx == 1 ? "" : "s");
2466 for (i = bidi_cache[bidi_cache_idx - 1].charpos; i > 0; i /= 10)
2467 ndigits++;
2468 fputs ("ch ", stderr);
2469 for (i = 0; i < bidi_cache_idx; i++)
2470 fprintf (stderr, "%*c", ndigits, bidi_cache[i].ch);
2471 fputs ("\n", stderr);
2472 fputs ("lvl ", stderr);
2473 for (i = 0; i < bidi_cache_idx; i++)
2474 fprintf (stderr, "%*d", ndigits, bidi_cache[i].resolved_level);
2475 fputs ("\n", stderr);
2476 fputs ("pos ", stderr);
2477 for (i = 0; i < bidi_cache_idx; i++)
2478 fprintf (stderr, "%*"pI"d", ndigits, bidi_cache[i].charpos);
2479 fputs ("\n", stderr);