summaryrefslogtreecommitdiffstats
path: root/generic/tkTextIndex.c
blob: 7d900ee7c6efe70fac44b2a0bc4a37cb47e61bdc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
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
167
168
169
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
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
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
456
457
458
459
460
461
462
463
464
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
500
501
502
503
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
529
530
531
532
533
534
535
536
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
689
690
691
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
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
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
1011
1012
1013
1014
1015
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
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
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
1276
1277
1278
1279
1280
1281
1282
1283
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
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
/*
 * tkTextIndex.c --
 *
 *	This module provides functions that manipulate indices for text
 *	widgets.
 *
 * Copyright (c) 1992-1994 The Regents of the University of California.
 * Copyright (c) 1994-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tkTextIndex.c,v 1.33 2008/12/05 09:33:12 patthoyts Exp $
 */

#include "default.h"
#include "tkInt.h"
#include "tkText.h"

/*
 * Index to use to select last character in line (very large integer):
 */

#define LAST_CHAR 1000000

/*
 * Modifiers for index parsing: 'display', 'any' or nothing.
 */

#define TKINDEX_NONE	0
#define TKINDEX_DISPLAY	1
#define TKINDEX_ANY	2

/*
 * Forward declarations for functions defined later in this file:
 */

static const char *	ForwBack(TkText *textPtr, const char *string,
			    TkTextIndex *indexPtr);
static const char *	StartEnd(TkText *textPtr, const char *string,
			    TkTextIndex *indexPtr);
static int		GetIndex(Tcl_Interp *interp, TkSharedText *sharedPtr,
			    TkText *textPtr, const char *string,
			    TkTextIndex *indexPtr, int *canCachePtr);

/*
 * The "textindex" Tcl_Obj definition:
 */

static void		DupTextIndexInternalRep(Tcl_Obj *srcPtr,
			    Tcl_Obj *copyPtr);
static void		FreeTextIndexInternalRep(Tcl_Obj *listPtr);
static int		SetTextIndexFromAny(Tcl_Interp *interp,
			    Tcl_Obj *objPtr);
static void		UpdateStringOfTextIndex(Tcl_Obj *objPtr);

/*
 * Accessor macros for the "textindex" type.
 */

#define GET_TEXTINDEX(objPtr) \
	((TkTextIndex *) (objPtr)->internalRep.twoPtrValue.ptr1)
#define GET_INDEXEPOCH(objPtr) \
	(PTR2INT((objPtr)->internalRep.twoPtrValue.ptr2))
#define SET_TEXTINDEX(objPtr, indexPtr) \
	((objPtr)->internalRep.twoPtrValue.ptr1 = (void *) (indexPtr))
#define SET_INDEXEPOCH(objPtr, epoch) \
	((objPtr)->internalRep.twoPtrValue.ptr2 = INT2PTR(epoch))

/*
 * Define the 'textindex' object type, which Tk uses to represent indices in
 * text widgets internally.
 */

const Tcl_ObjType tkTextIndexType = {
    "textindex",		/* name */
    FreeTextIndexInternalRep,	/* freeIntRepProc */
    DupTextIndexInternalRep,	/* dupIntRepProc */
    NULL,			/* updateStringProc */
    SetTextIndexFromAny		/* setFromAnyProc */
};

static void
FreeTextIndexInternalRep(
    Tcl_Obj *indexObjPtr)	/* TextIndex object with internal rep to
				 * free. */
{
    TkTextIndex *indexPtr = GET_TEXTINDEX(indexObjPtr);
    if (indexPtr->textPtr != NULL) {
	if (--indexPtr->textPtr->refCount == 0) {
	    /*
	     * The text widget has been deleted and we need to free it now.
	     */

	    ckfree((char *) (indexPtr->textPtr));
	}
    }
    ckfree((char *) indexPtr);
}

static void
DupTextIndexInternalRep(
    Tcl_Obj *srcPtr,		/* TextIndex obj with internal rep to copy. */
    Tcl_Obj *copyPtr)		/* TextIndex obj with internal rep to set. */
{
    int epoch;
    TkTextIndex *dupIndexPtr, *indexPtr;

    dupIndexPtr = (TkTextIndex *) ckalloc(sizeof(TkTextIndex));
    indexPtr = GET_TEXTINDEX(srcPtr);
    epoch = GET_INDEXEPOCH(srcPtr);

    dupIndexPtr->tree = indexPtr->tree;
    dupIndexPtr->linePtr = indexPtr->linePtr;
    dupIndexPtr->byteIndex = indexPtr->byteIndex;

    SET_TEXTINDEX(copyPtr, dupIndexPtr);
    SET_INDEXEPOCH(copyPtr, epoch);
}

/*
 * This will not be called except by TkTextNewIndexObj below. This is because
 * if a TkTextIndex is no longer valid, it is not possible to regenerate the
 * string representation.
 */

static void
UpdateStringOfTextIndex(
    Tcl_Obj *objPtr)
{
    char buffer[TK_POS_CHARS];
    register int len;

    const TkTextIndex *indexPtr = GET_TEXTINDEX(objPtr);

    len = TkTextPrintIndex(indexPtr->textPtr, indexPtr, buffer);

    objPtr->bytes = ckalloc((unsigned) len + 1);
    strcpy(objPtr->bytes, buffer);
    objPtr->length = len;
}

static int
SetTextIndexFromAny(
    Tcl_Interp *interp,		/* Used for error reporting if not NULL. */
    Tcl_Obj *objPtr)		/* The object to convert. */
{
    Tcl_AppendResult(interp, "can't convert value to textindex except "
	    "via TkTextGetIndexFromObj API", -1);
    return TCL_ERROR;
}

/*
 *---------------------------------------------------------------------------
 *
 * MakeObjIndex --
 *
 *	This function generates a Tcl_Obj description of an index, suitable
 *	for reading in again later. If the 'textPtr' is NULL then we still
 *	generate an index object, but it's internal description is deemed
 *	non-cacheable, and therefore effectively useless (apart from as a
 *	temporary memory storage). This is used for indices whose meaning is
 *	very temporary (like @0,0 or the name of a mark or tag). The mapping
 *	from such strings/objects to actual TkTextIndex pointers is not stable
 *	to minor text widget changes which we do not track (we track
 *	insertions and deletions).
 *
 * Results:
 *	A pointer to an allocated TkTextIndex which will be freed
 *	automatically when the Tcl_Obj is used for other purposes.
 *
 * Side effects:
 *	A small amount of memory is allocated.
 *
 *---------------------------------------------------------------------------
 */

static TkTextIndex *
MakeObjIndex(
    TkText *textPtr,		/* Information about text widget. */
    Tcl_Obj *objPtr,		/* Object containing description of
				 * position. */
    const TkTextIndex *origPtr)	/* Pointer to index. */
{
    TkTextIndex *indexPtr = (TkTextIndex *) ckalloc(sizeof(TkTextIndex));

    indexPtr->tree = origPtr->tree;
    indexPtr->linePtr = origPtr->linePtr;
    indexPtr->byteIndex = origPtr->byteIndex;
    SET_TEXTINDEX(objPtr, indexPtr);
    objPtr->typePtr = &tkTextIndexType;
    indexPtr->textPtr = textPtr;

    if (textPtr != NULL) {
	textPtr->refCount++;
	SET_INDEXEPOCH(objPtr, textPtr->sharedTextPtr->stateEpoch);
    } else {
	SET_INDEXEPOCH(objPtr, 0);
    }
    return indexPtr;
}

const TkTextIndex *
TkTextGetIndexFromObj(
    Tcl_Interp *interp,		/* Use this for error reporting. */
    TkText *textPtr,		/* Information about text widget. */
    Tcl_Obj *objPtr)		/* Object containing description of
				 * position. */
{
    TkTextIndex index;
    TkTextIndex *indexPtr = NULL;
    int cache;

    if (objPtr->typePtr == &tkTextIndexType) {
	int epoch;

	indexPtr = GET_TEXTINDEX(objPtr);
	epoch = GET_INDEXEPOCH(objPtr);

	if (epoch == textPtr->sharedTextPtr->stateEpoch) {
	    if (indexPtr->textPtr == textPtr) {
		return indexPtr;
	    }
	}
    }

    /*
     * The object is either not an index type or referred to a different text
     * widget, or referred to the correct widget, but it is out of date (text
     * has been added/deleted since).
     */

    if (GetIndex(interp, NULL, textPtr, Tcl_GetString(objPtr), &index,
	    &cache) != TCL_OK) {
	return NULL;
    }

    if (objPtr->typePtr != NULL) {
	if (objPtr->bytes == NULL) {
	    objPtr->typePtr->updateStringProc(objPtr);
	}
	if (objPtr->typePtr->freeIntRepProc != NULL) {
	    objPtr->typePtr->freeIntRepProc(objPtr);
	}
    }

    return MakeObjIndex((cache ? textPtr : NULL), objPtr, &index);
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextNewIndexObj --
 *
 *	This function generates a Tcl_Obj description of an index, suitable
 *	for reading in again later. The index generated is effectively stable
 *	to all except insertion/deletion operations on the widget.
 *
 * Results:
 *	A new Tcl_Obj with refCount zero.
 *
 * Side effects:
 *	A small amount of memory is allocated.
 *
 *---------------------------------------------------------------------------
 */

Tcl_Obj *
TkTextNewIndexObj(
    TkText *textPtr,		/* Text widget for this index */
    const TkTextIndex *indexPtr)/* Pointer to index. */
{
    Tcl_Obj *retVal;

    retVal = Tcl_NewObj();
    retVal->bytes = NULL;

    /*
     * Assumption that the above call returns an object with:
     * retVal->typePtr == NULL
     */

    MakeObjIndex(textPtr, retVal, indexPtr);

    /*
     * Unfortunately, it isn't possible for us to regenerate the string
     * representation so we have to create it here, while we can be sure the
     * contents of the index are still valid.
     */

    UpdateStringOfTextIndex(retVal);
    return retVal;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextMakePixelIndex --
 *
 *	Given a pixel index and a byte index, look things up in the B-tree and
 *	fill in a TkTextIndex structure.
 *
 *	The valid input range for pixelIndex is from 0 to the number of pixels
 *	in the widget-1. Anything outside that range will be rounded to the
 *	closest acceptable value.
 *
 * Results:
 *
 *	The structure at *indexPtr is filled in with information about the
 *	character at pixelIndex (or the closest existing character, if the
 *	specified one doesn't exist), and the number of excess pixels is
 *	returned as a result. This means if the given pixel index is exactly
 *	correct for the top-edge of the indexPtr, then zero will be returned,
 *	and otherwise we will return the calculation 'desired pixelIndex' -
 *	'actual pixel index of indexPtr'.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextMakePixelIndex(
    TkText *textPtr,		/* The Text Widget */
    int pixelIndex,		/* Pixel-index of desired line (0 means first
				 * pixel of first line of text). */
    TkTextIndex *indexPtr)	/* Structure to fill in. */
{
    int pixelOffset = 0;

    indexPtr->tree = textPtr->sharedTextPtr->tree;
    indexPtr->textPtr = textPtr;

    if (pixelIndex < 0) {
	pixelIndex = 0;
    }
    indexPtr->linePtr = TkBTreeFindPixelLine(textPtr->sharedTextPtr->tree,
	    textPtr, pixelIndex, &pixelOffset);

    /*
     * 'pixelIndex' was too large, so we try again, just to find the last
     * pixel in the window.
     */

    if (indexPtr->linePtr == NULL) {
	int lastMinusOne = TkBTreeNumPixels(textPtr->sharedTextPtr->tree,
		textPtr)-1;

	indexPtr->linePtr = TkBTreeFindPixelLine(textPtr->sharedTextPtr->tree,
		textPtr, lastMinusOne, &pixelOffset);
	indexPtr->byteIndex = 0;
	return pixelOffset;
    }
    indexPtr->byteIndex = 0;

    if (pixelOffset <= 0) {
	return 0;
    }
    return TkTextMeasureDown(textPtr, indexPtr, pixelOffset);
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextMakeByteIndex --
 *
 *	Given a line index and a byte index, look things up in the B-tree and
 *	fill in a TkTextIndex structure.
 *
 * Results:
 *	The structure at *indexPtr is filled in with information about the
 *	character at lineIndex and byteIndex (or the closest existing
 *	character, if the specified one doesn't exist), and indexPtr is
 *	returned as result.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

TkTextIndex *
TkTextMakeByteIndex(
    const TkTextBTree tree,	/* Tree that lineIndex and byteIndex refer
				 * to. */
    const TkText *textPtr,
    int lineIndex,		/* Index of desired line (0 means first line
				 * of text). */
    int byteIndex,		/* Byte index of desired character. */
    TkTextIndex *indexPtr)	/* Structure to fill in. */
{
    TkTextSegment *segPtr;
    int index;
    const char *p, *start;
    Tcl_UniChar ch;

    indexPtr->tree = tree;
    if (lineIndex < 0) {
	lineIndex = 0;
	byteIndex = 0;
    }
    if (byteIndex < 0) {
	byteIndex = 0;
    }
    indexPtr->linePtr = TkBTreeFindLine(tree, textPtr, lineIndex);
    if (indexPtr->linePtr == NULL) {
	indexPtr->linePtr = TkBTreeFindLine(tree, textPtr,
		TkBTreeNumLines(tree, textPtr));
	byteIndex = 0;
    }
    if (byteIndex == 0) {
	indexPtr->byteIndex = byteIndex;
	return indexPtr;
    }

    /*
     * Verify that the index is within the range of the line and points to a
     * valid character boundary.
     */

    index = 0;
    for (segPtr = indexPtr->linePtr->segPtr; ; segPtr = segPtr->nextPtr) {
	if (segPtr == NULL) {
	    /*
	     * Use the index of the last character in the line. Since the last
	     * character on the line is guaranteed to be a '\n', we can back
	     * up a constant sizeof(char) bytes.
	     */

	    indexPtr->byteIndex = index - sizeof(char);
	    break;
	}
	if (index + segPtr->size > byteIndex) {
	    indexPtr->byteIndex = byteIndex;
	    if ((byteIndex > index) && (segPtr->typePtr == &tkTextCharType)) {
		/*
		 * Prevent UTF-8 character from being split up by ensuring
		 * that byteIndex falls on a character boundary. If the index
		 * falls in the middle of a UTF-8 character, it will be
		 * adjusted to the end of that UTF-8 character.
		 */

		start = segPtr->body.chars + (byteIndex - index);
		p = Tcl_UtfPrev(start, segPtr->body.chars);
		p += Tcl_UtfToUniChar(p, &ch);
		indexPtr->byteIndex += p - start;
	    }
	    break;
	}
	index += segPtr->size;
    }
    return indexPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextMakeCharIndex --
 *
 *	Given a line index and a character index, look things up in the B-tree
 *	and fill in a TkTextIndex structure.
 *
 * Results:
 *	The structure at *indexPtr is filled in with information about the
 *	character at lineIndex and charIndex (or the closest existing
 *	character, if the specified one doesn't exist), and indexPtr is
 *	returned as result.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

TkTextIndex *
TkTextMakeCharIndex(
    TkTextBTree tree,		/* Tree that lineIndex and charIndex refer
				 * to. */
    TkText *textPtr,
    int lineIndex,		/* Index of desired line (0 means first line
				 * of text). */
    int charIndex,		/* Index of desired character. */
    TkTextIndex *indexPtr)	/* Structure to fill in. */
{
    register TkTextSegment *segPtr;
    char *p, *start, *end;
    int index, offset;
    Tcl_UniChar ch;

    indexPtr->tree = tree;
    if (lineIndex < 0) {
	lineIndex = 0;
	charIndex = 0;
    }
    if (charIndex < 0) {
	charIndex = 0;
    }
    indexPtr->linePtr = TkBTreeFindLine(tree, textPtr, lineIndex);
    if (indexPtr->linePtr == NULL) {
	indexPtr->linePtr = TkBTreeFindLine(tree, textPtr,
		TkBTreeNumLines(tree, textPtr));
	charIndex = 0;
    }

    /*
     * Verify that the index is within the range of the line. If not, just use
     * the index of the last character in the line.
     */

    index = 0;
    for (segPtr = indexPtr->linePtr->segPtr; ; segPtr = segPtr->nextPtr) {
	if (segPtr == NULL) {
	    /*
	     * Use the index of the last character in the line. Since the last
	     * character on the line is guaranteed to be a '\n', we can back
	     * up a constant sizeof(char) bytes.
	     */

	    indexPtr->byteIndex = index - sizeof(char);
	    break;
	}
	if (segPtr->typePtr == &tkTextCharType) {
	    /*
	     * Turn character offset into a byte offset.
	     */

	    start = segPtr->body.chars;
	    end = start + segPtr->size;
	    for (p = start; p < end; p += offset) {
		if (charIndex == 0) {
		    indexPtr->byteIndex = index;
		    return indexPtr;
		}
		charIndex--;
		offset = Tcl_UtfToUniChar(p, &ch);
		index += offset;
	    }
	} else {
	    if (charIndex < segPtr->size) {
		indexPtr->byteIndex = index;
		break;
	    }
	    charIndex -= segPtr->size;
	    index += segPtr->size;
	}
    }
    return indexPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexToSeg --
 *
 *	Given an index, this function returns the segment and offset within
 *	segment for the index.
 *
 * Results:
 *	The return value is a pointer to the segment referred to by indexPtr;
 *	this will always be a segment with non-zero size. The variable at
 *	*offsetPtr is set to hold the integer offset within the segment of the
 *	character given by indexPtr.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

TkTextSegment *
TkTextIndexToSeg(
    const TkTextIndex *indexPtr,/* Text index. */
    int *offsetPtr)		/* Where to store offset within segment, or
				 * NULL if offset isn't wanted. */
{
    TkTextSegment *segPtr;
    int offset;

    for (offset = indexPtr->byteIndex, segPtr = indexPtr->linePtr->segPtr;
	    offset >= segPtr->size;
	    offset -= segPtr->size, segPtr = segPtr->nextPtr) {
	/* Empty loop body. */
    }
    if (offsetPtr != NULL) {
	*offsetPtr = offset;
    }
    return segPtr;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextSegToOffset --
 *
 *	Given a segment pointer and the line containing it, this function
 *	returns the offset of the segment within its line.
 *
 * Results:
 *	The return value is the offset (within its line) of the first
 *	character in segPtr.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextSegToOffset(
    const TkTextSegment *segPtr,/* Segment whose offset is desired. */
    const TkTextLine *linePtr)	/* Line containing segPtr. */
{
    const TkTextSegment *segPtr2;
    int offset = 0;

    for (segPtr2 = linePtr->segPtr; segPtr2 != segPtr;
	    segPtr2 = segPtr2->nextPtr) {
	offset += segPtr2->size;
    }
    return offset;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextGetObjIndex --
 *
 *	Simpler wrapper around the string based function, but could be
 *	enhanced with a new object type in the future.
 *
 * Results:
 *	see TkTextGetIndex
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextGetObjIndex(
    Tcl_Interp *interp,		/* Use this for error reporting. */
    TkText *textPtr,		/* Information about text widget. */
    Tcl_Obj *idxObj,		/* Object containing textual description of
				 * position. */
    TkTextIndex *indexPtr)	/* Index structure to fill in. */
{
    return GetIndex(interp, NULL, textPtr, Tcl_GetString(idxObj), indexPtr,
	    NULL);
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextSharedGetObjIndex --
 *
 *	Simpler wrapper around the string based function, but could be
 *	enhanced with a new object type in the future.
 *
 * Results:
 *	see TkTextGetIndex
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextSharedGetObjIndex(
    Tcl_Interp *interp,		/* Use this for error reporting. */
    TkSharedText *sharedTextPtr,/* Information about text widget. */
    Tcl_Obj *idxObj,		/* Object containing textual description of
				 * position. */
    TkTextIndex *indexPtr)	/* Index structure to fill in. */
{
    return GetIndex(interp, sharedTextPtr, NULL, Tcl_GetString(idxObj),
	    indexPtr, NULL);
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextGetIndex --
 *
 *	Given a string, return the index that is described.
 *
 * Results:
 *	The return value is a standard Tcl return result. If TCL_OK is
 *	returned, then everything went well and the index at *indexPtr is
 *	filled in; otherwise TCL_ERROR is returned and an error message is
 *	left in the interp's result.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextGetIndex(
    Tcl_Interp *interp,		/* Use this for error reporting. */
    TkText *textPtr,		/* Information about text widget. */
    const char *string,		/* Textual description of position. */
    TkTextIndex *indexPtr)	/* Index structure to fill in. */
{
    return GetIndex(interp, NULL, textPtr, string, indexPtr, NULL);
}

/*
 *---------------------------------------------------------------------------
 *
 * GetIndex --
 *
 *	Given a string, return the index that is described.
 *
 * Results:
 *	The return value is a standard Tcl return result. If TCL_OK is
 *	returned, then everything went well and the index at *indexPtr is
 *	filled in; otherwise TCL_ERROR is returned and an error message is
 *	left in the interp's result.
 *
 *	If *canCachePtr is non-NULL, and everything went well, the integer it
 *	points to is set to 1 if the indexPtr is something which can be
 *	cached, and zero otherwise.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static int
GetIndex(
    Tcl_Interp *interp,		/* Use this for error reporting. */
    TkSharedText *sharedPtr,
    TkText *textPtr,		/* Information about text widget. */
    const char *string,		/* Textual description of position. */
    TkTextIndex *indexPtr,	/* Index structure to fill in. */
    int *canCachePtr)		/* Pointer to integer to store whether we can
				 * cache the index (or NULL). */
{
    char *p, *end, *endOfBase;
    TkTextIndex first, last;
    int wantLast, result;
    char c;
    const char *cp;
    Tcl_DString copy;
    int canCache = 0;

    if (sharedPtr == NULL) {
	sharedPtr = textPtr->sharedTextPtr;
    }

    /*
     *---------------------------------------------------------------------
     * Stage 1: check to see if the index consists of nothing but a mark name.
     * We do this check now even though it's also done later, in order to
     * allow mark names that include funny characters such as spaces or "+1c".
     *---------------------------------------------------------------------
     */

    if (TkTextMarkNameToIndex(textPtr, string, indexPtr) == TCL_OK) {
	goto done;
    }

    /*
     *------------------------------------------------
     * Stage 2: start again by parsing the base index.
     *------------------------------------------------
     */

    indexPtr->tree = sharedPtr->tree;

    /*
     * First look for the form "tag.first" or "tag.last" where "tag" is the
     * name of a valid tag. Try to use up as much as possible of the string in
     * this check (strrchr instead of strchr below). Doing the check now, and
     * in this way, allows tag names to include funny characters like "@" or
     * "+1c".
     */

    Tcl_DStringInit(&copy);
    p = strrchr(Tcl_DStringAppend(&copy, string, -1), '.');
    if (p != NULL) {
	TkTextSearch search;
	TkTextTag *tagPtr;
	Tcl_HashEntry *hPtr = NULL;
	const char *tagName;

	if ((p[1] == 'f') && (strncmp(p+1, "first", 5) == 0)) {
	    wantLast = 0;
	    endOfBase = p+6;
	} else if ((p[1] == 'l') && (strncmp(p+1, "last", 4) == 0)) {
	    wantLast = 1;
	    endOfBase = p+5;
	} else {
	    goto tryxy;
	}

	tagPtr = NULL;
	tagName = Tcl_DStringValue(&copy);
	if (((p - tagName) == 3) && !strncmp(tagName, "sel", 3)) {
	    /*
	     * Special case for sel tag which is not stored in the hash table.
	     */

	    tagPtr = textPtr->selTagPtr;
	} else {
	    *p = 0;
	    hPtr = Tcl_FindHashEntry(&sharedPtr->tagTable, tagName);
	    *p = '.';
	    if (hPtr != NULL) {
		tagPtr = Tcl_GetHashValue(hPtr);
	    }
	}

	if (tagPtr == NULL) {
	    goto tryxy;
	}

	TkTextMakeByteIndex(sharedPtr->tree, textPtr, 0, 0, &first);
	TkTextMakeByteIndex(sharedPtr->tree, textPtr,
		TkBTreeNumLines(sharedPtr->tree, textPtr), 0, &last);
	TkBTreeStartSearch(&first, &last, tagPtr, &search);
	if (!TkBTreeCharTagged(&first, tagPtr) && !TkBTreeNextTag(&search)) {
	    if (tagPtr == textPtr->selTagPtr) {
		tagName = "sel";
	    } else {
		tagName = Tcl_GetHashKey(&sharedPtr->tagTable, hPtr);
	    }
	    Tcl_ResetResult(interp);
	    Tcl_AppendResult(interp,
		    "text doesn't contain any characters tagged with \"",
		    tagName, "\"", NULL);
	    Tcl_DStringFree(&copy);
	    return TCL_ERROR;
	}
	*indexPtr = search.curIndex;
	if (wantLast) {
	    while (TkBTreeNextTag(&search)) {
		*indexPtr = search.curIndex;
	    }
	}
	goto gotBase;
    }

  tryxy:
    if (string[0] == '@') {
	/*
	 * Find character at a given x,y location in the window.
	 */

	int x, y;

	cp = string+1;
	x = strtol(cp, &end, 0);
	if ((end == cp) || (*end != ',')) {
	    goto error;
	}
	cp = end+1;
	y = strtol(cp, &end, 0);
	if (end == cp) {
	    goto error;
	}
	TkTextPixelIndex(textPtr, x, y, indexPtr, NULL);
	endOfBase = end;
	goto gotBase;
    }

    if (isdigit(UCHAR(string[0])) || (string[0] == '-')) {
	int lineIndex, charIndex;

	/*
	 * Base is identified with line and character indices.
	 */

	lineIndex = strtol(string, &end, 0) - 1;
	if ((end == string) || (*end != '.')) {
	    goto error;
	}
	p = end+1;
	if ((*p == 'e') && (strncmp(p, "end", 3) == 0)) {
	    charIndex = LAST_CHAR;
	    endOfBase = p+3;
	} else {
	    charIndex = strtol(p, &end, 0);
	    if (end == p) {
		goto error;
	    }
	    endOfBase = end;
	}
	TkTextMakeCharIndex(sharedPtr->tree, textPtr, lineIndex, charIndex,
		indexPtr);
	canCache = 1;
	goto gotBase;
    }

    for (p = Tcl_DStringValue(&copy); *p != 0; p++) {
	if (isspace(UCHAR(*p)) || (*p == '+') || (*p == '-')) {
	    break;
	}
    }
    endOfBase = p;
    if (string[0] == '.') {
	/*
	 * See if the base position is the name of an embedded window.
	 */

	c = *endOfBase;
	*endOfBase = 0;
	result = TkTextWindowIndex(textPtr, Tcl_DStringValue(&copy), indexPtr);
	*endOfBase = c;
	if (result != 0) {
	    goto gotBase;
	}
    }
    if ((string[0] == 'e')
	    && (strncmp(string, "end",
	    (size_t) (endOfBase-Tcl_DStringValue(&copy))) == 0)) {
	/*
	 * Base position is end of text.
	 */

	TkTextMakeByteIndex(sharedPtr->tree, textPtr,
		TkBTreeNumLines(sharedPtr->tree, textPtr), 0, indexPtr);
	canCache = 1;
	goto gotBase;
    } else {
	/*
	 * See if the base position is the name of a mark.
	 */

	c = *endOfBase;
	*endOfBase = 0;
	result = TkTextMarkNameToIndex(textPtr, Tcl_DStringValue(&copy),
		indexPtr);
	*endOfBase = c;
	if (result == TCL_OK) {
	    goto gotBase;
	}

	/*
	 * See if the base position is the name of an embedded image.
	 */

	c = *endOfBase;
	*endOfBase = 0;
	result = TkTextImageIndex(textPtr, Tcl_DStringValue(&copy), indexPtr);
	*endOfBase = c;
	if (result != 0) {
	    goto gotBase;
	}
    }
    goto error;

    /*
     *-------------------------------------------------------------------
     * Stage 3: process zero or more modifiers. Each modifier is either a
     * keyword like "wordend" or "linestart", or it has the form "op count
     * units" where op is + or -, count is a number, and units is "chars" or
     * "lines".
     *-------------------------------------------------------------------
     */

  gotBase:
    cp = endOfBase;
    while (1) {
	while (isspace(UCHAR(*cp))) {
	    cp++;
	}
	if (*cp == 0) {
	    break;
	}

	if ((*cp == '+') || (*cp == '-')) {
	    cp = ForwBack(textPtr, cp, indexPtr);
	} else {
	    cp = StartEnd(textPtr, cp, indexPtr);
	}
	if (cp == NULL) {
	    goto error;
	}
    }
    Tcl_DStringFree(&copy);

  done:
    if (canCachePtr != NULL) {
	*canCachePtr = canCache;
    }
    if (indexPtr->linePtr == NULL) {
	Tcl_Panic("Bad index created");
    }
    return TCL_OK;

  error:
    Tcl_DStringFree(&copy);
    Tcl_ResetResult(interp);
    Tcl_AppendResult(interp, "bad text index \"", string, "\"", NULL);
    return TCL_ERROR;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextPrintIndex --
 *
 *	This function generates a string description of an index, suitable for
 *	reading in again later.
 *
 * Results:
 *	The characters pointed to by string are modified. Returns the number
 *	of characters in the string.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextPrintIndex(
    const TkText *textPtr,
    const TkTextIndex *indexPtr,/* Pointer to index. */
    char *string)		/* Place to store the position. Must have at
				 * least TK_POS_CHARS characters. */
{
    TkTextSegment *segPtr;
    TkTextLine *linePtr;
    int numBytes, charIndex;

    numBytes = indexPtr->byteIndex;
    charIndex = 0;
    linePtr = indexPtr->linePtr;

    for (segPtr = linePtr->segPtr; ; segPtr = segPtr->nextPtr) {
	if (segPtr == NULL) {
	    /*
	     * Two logical lines merged into one display line through eliding
	     * of a newline.
	     */

	    linePtr = TkBTreeNextLine(NULL, linePtr);
	    segPtr = linePtr->segPtr;
	}
	if (numBytes <= segPtr->size) {
	    break;
	}
	if (segPtr->typePtr == &tkTextCharType) {
	    charIndex += Tcl_NumUtfChars(segPtr->body.chars, segPtr->size);
	} else {
	    charIndex += segPtr->size;
	}
	numBytes -= segPtr->size;
    }

    if (segPtr->typePtr == &tkTextCharType) {
	charIndex += Tcl_NumUtfChars(segPtr->body.chars, numBytes);
    } else {
	charIndex += numBytes;
    }

    return sprintf(string, "%d.%d",
	    TkBTreeLinesTo(textPtr, indexPtr->linePtr) + 1, charIndex);
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexCmp --
 *
 *	Compare two indices to see which one is earlier in the text.
 *
 * Results:
 *	The return value is 0 if index1Ptr and index2Ptr refer to the same
 *	position in the file, -1 if index1Ptr refers to an earlier position
 *	than index2Ptr, and 1 otherwise.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextIndexCmp(
    const TkTextIndex*index1Ptr,/* First index. */
    const TkTextIndex*index2Ptr)/* Second index. */
{
    int line1, line2;

    if (index1Ptr->linePtr == index2Ptr->linePtr) {
	if (index1Ptr->byteIndex < index2Ptr->byteIndex) {
	    return -1;
	} else if (index1Ptr->byteIndex > index2Ptr->byteIndex) {
	    return 1;
	} else {
	    return 0;
	}
    }

    /*
     * Assumption here that it is ok for comparisons to reflect the full
     * B-tree and not just the portion that is available to any client. This
     * should be true because the only indexPtr's we should be given are ones
     * which are valid for the current client.
     */

    line1 = TkBTreeLinesTo(NULL, index1Ptr->linePtr);
    line2 = TkBTreeLinesTo(NULL, index2Ptr->linePtr);
    if (line1 < line2) {
	return -1;
    }
    if (line1 > line2) {
	return 1;
    }
    return 0;
}

/*
 *---------------------------------------------------------------------------
 *
 * ForwBack --
 *
 *	This function handles +/- modifiers for indices to adjust the index
 *	forwards or backwards.
 *
 * Results:
 *	If the modifier in string is successfully parsed then the return value
 *	is the address of the first character after the modifier, and
 *	*indexPtr is updated to reflect the modifier. If there is a syntax
 *	error in the modifier then NULL is returned.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

static const char *
ForwBack(
    TkText *textPtr,		/* Information about text widget. */
    const char *string,		/* String to parse for additional info about
				 * modifier (count and units). Points to "+"
				 * or "-" that starts modifier. */
    TkTextIndex *indexPtr)	/* Index to update as specified in string. */
{
    register const char *p, *units;
    char *end;
    int count, lineIndex, modifier;
    size_t length;

    /*
     * Get the count (how many units forward or backward).
     */

    p = string+1;
    while (isspace(UCHAR(*p))) {
	p++;
    }
    count = strtol(p, &end, 0);
    if (end == p) {
	return NULL;
    }
    p = end;
    while (isspace(UCHAR(*p))) {
	p++;
    }

    /*
     * Find the end of this modifier (next space or + or - character), then
     * check if there is a textual 'display' or 'any' modifier. These
     * modifiers can be their own word (in which case they can be abbreviated)
     * or they can follow on to the actual unit in a single word (in which
     * case no abbreviation is allowed). So, 'display lines', 'd lines',
     * 'displaylin' are all ok, but 'dline' is not.
     */

    units = p;
    while ((*p != '\0') && !isspace(UCHAR(*p)) && (*p != '+') && (*p != '-')) {
	p++;
    }
    length = p - units;
    if ((*units == 'd') &&
	    (strncmp(units, "display", (length > 7 ? 7 : length)) == 0)) {
	modifier = TKINDEX_DISPLAY;
	if (length > 7) {
	    p -= (length - 7);
	}
    } else if ((*units == 'a') &&
	    (strncmp(units, "any", (length > 3 ? 3 : length)) == 0)) {
	modifier = TKINDEX_ANY;
	if (length > 3) {
	    p -= (length - 3);
	}
    } else {
	modifier = TKINDEX_NONE;
    }

    /*
     * If we had a modifier, which we interpreted ok, so now forward to the
     * actual units.
     */

    if (modifier != TKINDEX_NONE) {
	while (isspace(UCHAR(*p))) {
	    p++;
	}
	units = p;
	while (*p!='\0' && !isspace(UCHAR(*p)) && *p!='+' && *p!='-') {
	    p++;
	}
	length = p - units;
    }

    /*
     * Finally parse the units.
     */

    if ((*units == 'c') && (strncmp(units, "chars", length) == 0)) {
	TkTextCountType type;

	if (modifier == TKINDEX_NONE) {
	    type = COUNT_INDICES;
	} else if (modifier == TKINDEX_ANY) {
	    type = COUNT_CHARS;
	} else {
	    type = COUNT_DISPLAY_CHARS;
	}

	if (*string == '+') {
	    TkTextIndexForwChars(textPtr, indexPtr, count, indexPtr, type);
	} else {
	    TkTextIndexBackChars(textPtr, indexPtr, count, indexPtr, type);
	}
    } else if ((*units == 'i') && (strncmp(units, "indices", length) == 0)) {
	TkTextCountType type;

	if (modifier == TKINDEX_DISPLAY) {
	    type = COUNT_DISPLAY_INDICES;
	} else {
	    type = COUNT_INDICES;
	}

	if (*string == '+') {
	    TkTextIndexForwChars(textPtr, indexPtr, count, indexPtr, type);
	} else {
	    TkTextIndexBackChars(textPtr, indexPtr, count, indexPtr, type);
	}
    } else if ((*units == 'l') && (strncmp(units, "lines", length) == 0)) {
	if (modifier == TKINDEX_DISPLAY) {
	    /*
	     * Find the appropriate pixel offset of the current position
	     * within its display line. This also has the side-effect of
	     * moving indexPtr, but that doesn't matter since we will do it
	     * again below.
	     *
	     * Then find the right display line, and finally calculated the
	     * index we want in that display line, based on the original pixel
	     * offset.
	     */

	    int xOffset, forward;

	    if (TkTextIsElided(textPtr, indexPtr, NULL)) {
		/*
		 * Go forward to the first non-elided index.
		 */

		TkTextIndexForwChars(textPtr, indexPtr, 0, indexPtr,
			COUNT_DISPLAY_INDICES);
	    }

	    /*
	     * Unlike the Forw/BackChars code, the display line code is
	     * sensitive to whether we are genuinely going forwards or
	     * backwards. So, we need to determine that. This is important in
	     * the case where we have "+ -3 displaylines", for example.
	     */

	    if ((count < 0) ^ (*string == '-')) {
		forward = 0;
	    } else {
		forward = 1;
	    }

	    count = abs(count);
	    if (count == 0) {
		return p;
	    }

	    if (forward) {
		TkTextFindDisplayLineEnd(textPtr, indexPtr, 1, &xOffset);
		while (count-- > 0) {
		    /*
		     * Go to the end of the line, then forward one char/byte
		     * to get to the beginning of the next line.
		     */

		    TkTextFindDisplayLineEnd(textPtr, indexPtr, 1, NULL);
		    TkTextIndexForwChars(textPtr, indexPtr, 1, indexPtr,
			    COUNT_DISPLAY_INDICES);
		}
	    } else {
		TkTextFindDisplayLineEnd(textPtr, indexPtr, 0, &xOffset);
		while (count-- > 0) {
		    /*
		     * Go to the beginning of the line, then backward one
		     * char/byte to get to the end of the previous line.
		     */

		    TkTextFindDisplayLineEnd(textPtr, indexPtr, 0, NULL);
		    TkTextIndexBackChars(textPtr, indexPtr, 1, indexPtr,
			    COUNT_DISPLAY_INDICES);
		}
		TkTextFindDisplayLineEnd(textPtr, indexPtr, 0, NULL);
	    }

	    /*
	     * This call assumes indexPtr is the beginning of a display line
	     * and moves it to the 'xOffset' position of that line, which is
	     * just what we want.
	     */

	    TkTextIndexOfX(textPtr, xOffset, indexPtr);
	} else {
	    lineIndex = TkBTreeLinesTo(textPtr, indexPtr->linePtr);
	    if (*string == '+') {
		lineIndex += count;
	    } else {
		lineIndex -= count;

		/*
		 * The check below retains the character position, even if the
		 * line runs off the start of the file. Without it, the
		 * character position will get reset to 0 by TkTextMakeIndex.
		 */

		if (lineIndex < 0) {
		    lineIndex = 0;
		}
	    }

	    /*
	     * This doesn't work quite right if using a proportional font or
	     * UTF-8 characters with varying numbers of bytes, or if there are
	     * embedded windows, images, etc. The cursor will bop around,
	     * keeping a constant number of bytes (not characters) from the
	     * left edge (but making sure not to split any UTF-8 characters),
	     * regardless of the x-position the index corresponds to. The
	     * proper way to do this is to get the x-position of the index and
	     * then pick the character at the same x-position in the new line.
	     */

	    TkTextMakeByteIndex(indexPtr->tree, textPtr, lineIndex,
		    indexPtr->byteIndex, indexPtr);
	}
    } else {
	return NULL;
    }
    return p;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexForwBytes --
 *
 *	Given an index for a text widget, this function creates a new index
 *	that points "count" bytes ahead of the source index.
 *
 * Results:
 *	*dstPtr is modified to refer to the character "count" bytes after
 *	srcPtr, or to the last character in the TkText if there aren't "count"
 *	bytes left.
 *
 *	In this latter case, the function returns '1' to indicate that not all
 *	of 'byteCount' could be used.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextIndexForwBytes(
    const TkText *textPtr,
    const TkTextIndex *srcPtr,	/* Source index. */
    int byteCount,		/* How many bytes forward to move. May be
				 * negative. */
    TkTextIndex *dstPtr)	/* Destination index: gets modified. */
{
    TkTextLine *linePtr;
    TkTextSegment *segPtr;
    int lineLength;

    if (byteCount < 0) {
	TkTextIndexBackBytes(textPtr, srcPtr, -byteCount, dstPtr);
	return 0;
    }

    *dstPtr = *srcPtr;
    dstPtr->byteIndex += byteCount;
    while (1) {
	/*
	 * Compute the length of the current line.
	 */

	lineLength = 0;
	for (segPtr = dstPtr->linePtr->segPtr; segPtr != NULL;
		segPtr = segPtr->nextPtr) {
	    lineLength += segPtr->size;
	}

	/*
	 * If the new index is in the same line then we're done. Otherwise go
	 * on to the next line.
	 */

	if (dstPtr->byteIndex < lineLength) {
	    return 0;
	}
	dstPtr->byteIndex -= lineLength;
	linePtr = TkBTreeNextLine(textPtr, dstPtr->linePtr);
	if (linePtr == NULL) {
	    dstPtr->byteIndex = lineLength - 1;
	    return 1;
	}
	dstPtr->linePtr = linePtr;
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexForwChars --
 *
 *	Given an index for a text widget, this function creates a new index
 *	that points "count" items of type given by "type" ahead of the source
 *	index. "count" can be zero, which is useful in the case where one
 *	wishes to move forward by display (non-elided) chars or indices or one
 *	wishes to move forward by chars, skipping any intervening indices. In
 *	this case dstPtr will point to the first acceptable index which is
 *	encountered.
 *
 * Results:
 *	*dstPtr is modified to refer to the character "count" items after
 *	srcPtr, or to the last character in the TkText if there aren't
 *	sufficient items left in the widget.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

void
TkTextIndexForwChars(
    const TkText *textPtr,	/* Overall information about text widget. */
    const TkTextIndex *srcPtr,	/* Source index. */
    int charCount,		/* How many characters forward to move. May
				 * be negative. */
    TkTextIndex *dstPtr,	/* Destination index: gets modified. */
    TkTextCountType type)	/* The type of item to count */
{
    TkTextLine *linePtr;
    TkTextSegment *segPtr;
    TkTextElideInfo *infoPtr = NULL;
    int byteOffset;
    char *start, *end, *p;
    Tcl_UniChar ch;
    int elide = 0;
    int checkElided = (type & COUNT_DISPLAY);

    if (charCount < 0) {
	TkTextIndexBackChars(textPtr, srcPtr, -charCount, dstPtr, type);
	return;
    }
    if (checkElided) {
	infoPtr = (TkTextElideInfo *) ckalloc(sizeof(TkTextElideInfo));
	elide = TkTextIsElided(textPtr, srcPtr, infoPtr);
    }

    *dstPtr = *srcPtr;

    /*
     * Find seg that contains src byteIndex. Move forward specified number of
     * chars.
     */

    if (checkElided) {
	/*
	 * In this case we have already calculated the information we need, so
	 * no need to use TkTextIndexToSeg()
	 */

	segPtr = infoPtr->segPtr;
	byteOffset = dstPtr->byteIndex - infoPtr->segOffset;
    } else {
	segPtr = TkTextIndexToSeg(dstPtr, &byteOffset);
    }

    while (1) {
	/*
	 * Go through each segment in line looking for specified character
	 * index.
	 */

	for ( ; segPtr != NULL; segPtr = segPtr->nextPtr) {
	    /*
	     * If we do need to pay attention to the visibility of
	     * characters/indices, check that first. If the current segment
	     * isn't visible, then we simply continue the loop.
	     */

	    if (checkElided && ((segPtr->typePtr == &tkTextToggleOffType)
		    || (segPtr->typePtr == &tkTextToggleOnType))) {
		TkTextTag *tagPtr = segPtr->body.toggle.tagPtr;

		/*
		 * The elide state only changes if this tag is either the
		 * current highest priority tag (and is therefore being
		 * toggled off), or it's a new tag with higher priority.
		 */

		if (tagPtr->elideString != NULL) {
		    infoPtr->tagCnts[tagPtr->priority]++;
		    if (infoPtr->tagCnts[tagPtr->priority] & 1) {
			infoPtr->tagPtrs[tagPtr->priority] = tagPtr;
		    }

		    if (tagPtr->priority >= infoPtr->elidePriority) {
			if (segPtr->typePtr == &tkTextToggleOffType) {
			    /*
			     * If it is being toggled off, and it has an elide
			     * string, it must actually be the current highest
			     * priority tag, so this check is redundant:
			     */

			    if (tagPtr->priority != infoPtr->elidePriority) {
				Tcl_Panic("Bad tag priority being toggled off");
			    }

			    /*
			     * Find previous elide tag, if any (if not then
			     * elide will be zero, of course).
			     */

			    elide = 0;
			    while (--infoPtr->elidePriority > 0) {
				if (infoPtr->tagCnts[infoPtr->elidePriority]
					& 1) {
				    elide = infoPtr->tagPtrs
					    [infoPtr->elidePriority]->elide;
				    break;
				}
			    }
			} else {
			    elide = tagPtr->elide;
			    infoPtr->elidePriority = tagPtr->priority;
			}
		    }
		}
	    }

	    if (!elide) {
		if (segPtr->typePtr == &tkTextCharType) {
		    start = segPtr->body.chars + byteOffset;
		    end = segPtr->body.chars + segPtr->size;
		    for (p = start; p < end; p += Tcl_UtfToUniChar(p, &ch)) {
			if (charCount == 0) {
			    dstPtr->byteIndex += (p - start);
			    goto forwardCharDone;
			}
			charCount--;
		    }
		} else if (type & COUNT_INDICES) {
		    if (charCount < segPtr->size - byteOffset) {
			dstPtr->byteIndex += charCount;
			goto forwardCharDone;
		    }
		    charCount -= segPtr->size - byteOffset;
		}
	    }

	    dstPtr->byteIndex += segPtr->size - byteOffset;
	    byteOffset = 0;
	}

	/*
	 * Go to the next line. If we are at the end of the text item, back up
	 * one byte (for the terminal '\n' character) and return that index.
	 */

	linePtr = TkBTreeNextLine(textPtr, dstPtr->linePtr);
	if (linePtr == NULL) {
	    dstPtr->byteIndex -= sizeof(char);
	    goto forwardCharDone;
	}
	dstPtr->linePtr = linePtr;
	dstPtr->byteIndex = 0;
	segPtr = dstPtr->linePtr->segPtr;
    }

  forwardCharDone:
    if (infoPtr != NULL) {
	TkTextFreeElideInfo(infoPtr);
	ckfree((char *) infoPtr);
    }
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexCount --
 *
 *	Given an ordered pair of indices in a text widget, this function
 *	counts how many characters (not bytes) are between the two indices.
 *
 *	It is illegal to call this function with unordered indices.
 *
 *	Note that 'textPtr' is only used if we need to check for elided
 *	attributes, i.e. if type is COUNT_DISPLAY_INDICES or
 *	COUNT_DISPLAY_CHARS.
 *
 * Results:
 *	The number of characters in the given range, which meet the
 *	appropriate 'type' attributes.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextIndexCount(
    const TkText *textPtr,	/* Overall information about text widget. */
    const TkTextIndex *indexPtr1,
				/* Index describing location of character from
				 * which to count. */
    const TkTextIndex *indexPtr2,
				/* Index describing location of last character
				 * at which to stop the count. */
    TkTextCountType type)	/* The kind of indices to count. */
{
    TkTextLine *linePtr1;
    TkTextSegment *segPtr, *seg2Ptr = NULL;
    TkTextElideInfo *infoPtr = NULL;
    int byteOffset, maxBytes, count = 0, elide = 0;
    int checkElided = (type & COUNT_DISPLAY);

    /*
     * Find seg that contains src index, and remember how many bytes not to
     * count in the given segment.
     */

    segPtr = TkTextIndexToSeg(indexPtr1, &byteOffset);
    linePtr1 = indexPtr1->linePtr;

    seg2Ptr = TkTextIndexToSeg(indexPtr2, &maxBytes);

    if (checkElided) {
	infoPtr = (TkTextElideInfo *) ckalloc(sizeof(TkTextElideInfo));
	elide = TkTextIsElided(textPtr, indexPtr1, infoPtr);
    }

    while (1) {
	/*
	 * Go through each segment in line adding up the number of characters.
	 */

	for ( ; segPtr != NULL; segPtr = segPtr->nextPtr) {
	    /*
	     * If we do need to pay attention to the visibility of
	     * characters/indices, check that first. If the current segment
	     * isn't visible, then we simply continue the loop.
	     */

	    if (checkElided) {
		if ((segPtr->typePtr == &tkTextToggleOffType)
			|| (segPtr->typePtr == &tkTextToggleOnType)) {
		    TkTextTag *tagPtr = segPtr->body.toggle.tagPtr;

		    /*
		     * The elide state only changes if this tag is either the
		     * current highest priority tag (and is therefore being
		     * toggled off), or it's a new tag with higher priority.
		     */

		    if (tagPtr->elideString != NULL) {
			infoPtr->tagCnts[tagPtr->priority]++;
			if (infoPtr->tagCnts[tagPtr->priority] & 1) {
			    infoPtr->tagPtrs[tagPtr->priority] = tagPtr;
			}
			if (tagPtr->priority >= infoPtr->elidePriority) {
			    if (segPtr->typePtr == &tkTextToggleOffType) {
				/*
				 * If it is being toggled off, and it has an
				 * elide string, it must actually be the
				 * current highest priority tag, so this check
				 * is redundant:
				 */

				if (tagPtr->priority!=infoPtr->elidePriority) {
				    Tcl_Panic("Bad tag priority being toggled off");
				}

				/*
				 * Find previous elide tag, if any (if not
				 * then elide will be zero, of course).
				 */

				elide = 0;
				while (--infoPtr->elidePriority > 0) {
				    if (infoPtr->tagCnts[
					    infoPtr->elidePriority] & 1) {
					elide = infoPtr->tagPtrs[
						infoPtr->elidePriority]->elide;
					break;
				    }
				}
			    } else {
				elide = tagPtr->elide;
				infoPtr->elidePriority = tagPtr->priority;
			    }
			}
		    }
		}
		if (elide) {
		    if (segPtr == seg2Ptr) {
			goto countDone;
		    }
		    byteOffset = 0;
		    continue;
		}
	    }

	    if (segPtr->typePtr == &tkTextCharType) {
		int byteLen = segPtr->size - byteOffset;
		register unsigned char *str = (unsigned char *)
			segPtr->body.chars + byteOffset;
		register int i;

		if (segPtr == seg2Ptr) {
		    if (byteLen > (maxBytes - byteOffset)) {
			byteLen = maxBytes - byteOffset;
		    }
		}
		i = byteLen;

		/*
		 * This is a speed sensitive function, so run specially over
		 * the string to count continuous ascii characters before
		 * resorting to the Tcl_NumUtfChars call. This is a long form
		 * of:
		 *
		 *   stringPtr->numChars =
		 *	     Tcl_NumUtfChars(objPtr->bytes, objPtr->length);
		 */

		while (i && (*str < 0xC0)) {
		    i--;
		    str++;
		}
		count += byteLen - i;
		if (i) {
		    count += Tcl_NumUtfChars(segPtr->body.chars + byteOffset
			    + (byteLen - i), i);
		}
	    } else {
		if (type & COUNT_INDICES) {
		    int byteLen = segPtr->size - byteOffset;

		    if (segPtr == seg2Ptr) {
			if (byteLen > (maxBytes - byteOffset)) {
			    byteLen = maxBytes - byteOffset;
			}
		    }
		    count += byteLen;
		}
	    }
	    if (segPtr == seg2Ptr) {
		goto countDone;
	    }
	    byteOffset = 0;
	}

	/*
	 * Go to the next line. If we are at the end of the text item, back up
	 * one byte (for the terminal '\n' character) and return that index.
	 */

	linePtr1 = TkBTreeNextLine(textPtr, linePtr1);
	if (linePtr1 == NULL) {
	    Tcl_Panic("Reached end of text widget when counting characters");
	}
	segPtr = linePtr1->segPtr;
    }

  countDone:
    if (infoPtr != NULL) {
	TkTextFreeElideInfo(infoPtr);
	ckfree((char *) infoPtr);
    }
    return count;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexBackBytes --
 *
 *	Given an index for a text widget, this function creates a new index
 *	that points "count" bytes earlier than the source index.
 *
 * Results:
 *	*dstPtr is modified to refer to the character "count" bytes before
 *	srcPtr, or to the first character in the TkText if there aren't
 *	"count" bytes earlier than srcPtr.
 *
 *	Returns 1 if we couldn't use all of 'byteCount' because we have run
 *	into the beginning or end of the text, and zero otherwise.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

int
TkTextIndexBackBytes(
    const TkText *textPtr,
    const TkTextIndex *srcPtr,	/* Source index. */
    int byteCount,		/* How many bytes backward to move. May be
				 * negative. */
    TkTextIndex *dstPtr)	/* Destination index: gets modified. */
{
    TkTextSegment *segPtr;
    int lineIndex;

    if (byteCount < 0) {
	return TkTextIndexForwBytes(textPtr, srcPtr, -byteCount, dstPtr);
    }

    *dstPtr = *srcPtr;
    dstPtr->byteIndex -= byteCount;
    lineIndex = -1;
    while (dstPtr->byteIndex < 0) {
	/*
	 * Move back one line in the text. If we run off the beginning of the
	 * file then just return the first character in the text.
	 */

	if (lineIndex < 0) {
	    lineIndex = TkBTreeLinesTo(textPtr, dstPtr->linePtr);
	}
	if (lineIndex == 0) {
	    dstPtr->byteIndex = 0;
	    return 1;
	}
	lineIndex--;
	dstPtr->linePtr = TkBTreeFindLine(dstPtr->tree, textPtr, lineIndex);

	/*
	 * Compute the length of the line and add that to dstPtr->charIndex.
	 */

	for (segPtr = dstPtr->linePtr->segPtr; segPtr != NULL;
		segPtr = segPtr->nextPtr) {
	    dstPtr->byteIndex += segPtr->size;
	}
    }
    return 0;
}

/*
 *---------------------------------------------------------------------------
 *
 * TkTextIndexBackChars --
 *
 *	Given an index for a text widget, this function creates a new index
 *	that points "count" items of type given by "type" earlier than the
 *	source index. "count" can be zero, which is useful in the case where
 *	one wishes to move backward by display (non-elided) chars or indices
 *	or one wishes to move backward by chars, skipping any intervening
 *	indices. In this case the returned index *dstPtr will point just
 *	_after_ the first acceptable index which is encountered.
 *
 * Results:
 *	*dstPtr is modified to refer to the character "count" items before
 *	srcPtr, or to the first index in the window if there aren't sufficient
 *	items earlier than srcPtr.
 *
 * Side effects:
 *	None.
 *
 *---------------------------------------------------------------------------
 */

void
TkTextIndexBackChars(
    const TkText *textPtr,	/* Overall information about text widget. */
    const TkTextIndex *srcPtr,	/* Source index. */
    int charCount,		/* How many characters backward to move. May
				 * be negative. */
    TkTextIndex *dstPtr,	/* Destination index: gets modified. */
    TkTextCountType type)	/* The type of item to count */
{
    TkTextSegment *segPtr, *oldPtr;
    TkTextElideInfo *infoPtr = NULL;
    int lineIndex, segSize;
    const char *p, *start, *end;
    int elide = 0;
    int checkElided = (type & COUNT_DISPLAY);

    if (charCount < 0) {
	TkTextIndexForwChars(textPtr, srcPtr, -charCount, dstPtr, type);
	return;
    }
    if (checkElided) {
	infoPtr = (TkTextElideInfo *) ckalloc(sizeof(TkTextElideInfo));
	elide = TkTextIsElided(textPtr, srcPtr, infoPtr);
    }

    *dstPtr = *srcPtr;

    /*
     * Find offset within seg that contains byteIndex. Move backward specified
     * number of chars.
     */

    lineIndex = -1;

    segSize = dstPtr->byteIndex;

    if (checkElided) {
	segPtr = infoPtr->segPtr;
	segSize -= infoPtr->segOffset;
    } else {
	TkTextLine *linePtr = dstPtr->linePtr;
	for (segPtr = linePtr->segPtr; ; segPtr = segPtr->nextPtr) {
	    if (segPtr == NULL) {
		/*
		 * Two logical lines merged into one display line through
		 * eliding of a newline.
		 */

		linePtr = TkBTreeNextLine(NULL, linePtr);
		segPtr = linePtr->segPtr;
	    }
	    if (segSize <= segPtr->size) {
		break;
	    }
	    segSize -= segPtr->size;
	}
    }

    /*
     * Now segPtr points to the segment containing the starting index.
     */

    while (1) {
	/*
	 * If we do need to pay attention to the visibility of
	 * characters/indices, check that first. If the current segment isn't
	 * visible, then we simply continue the loop.
	 */

	if (checkElided && ((segPtr->typePtr == &tkTextToggleOffType)
		|| (segPtr->typePtr == &tkTextToggleOnType))) {
	    TkTextTag *tagPtr = segPtr->body.toggle.tagPtr;

	    /*
	     * The elide state only changes if this tag is either the current
	     * highest priority tag (and is therefore being toggled off), or
	     * it's a new tag with higher priority.
	     */

	    if (tagPtr->elideString != NULL) {
		infoPtr->tagCnts[tagPtr->priority]++;
		if (infoPtr->tagCnts[tagPtr->priority] & 1) {
		    infoPtr->tagPtrs[tagPtr->priority] = tagPtr;
		}
		if (tagPtr->priority >= infoPtr->elidePriority) {
		    if (segPtr->typePtr == &tkTextToggleOnType) {
			/*
			 * If it is being toggled on, and it has an elide
			 * string, it must actually be the current highest
			 * priority tag, so this check is redundant:
			 */

			if (tagPtr->priority != infoPtr->elidePriority) {
			    Tcl_Panic("Bad tag priority being toggled on");
			}

			/*
			 * Find previous elide tag, if any (if not then elide
			 * will be zero, of course).
			 */

			elide = 0;
			while (--infoPtr->elidePriority > 0) {
			    if (infoPtr->tagCnts[infoPtr->elidePriority] & 1) {
				elide = infoPtr->tagPtrs[
					infoPtr->elidePriority]->elide;
				break;
			    }
			}
		    } else {
			elide = tagPtr->elide;
			infoPtr->elidePriority = tagPtr->priority;
		    }
		}
	    }
	}

	if (!elide) {
	    if (segPtr->typePtr == &tkTextCharType) {
		start = segPtr->body.chars;
		end = segPtr->body.chars + segSize;
		for (p = end; ; p = Tcl_UtfPrev(p, start)) {
		    if (charCount == 0) {
			dstPtr->byteIndex -= (end - p);
			goto backwardCharDone;
		    }
		    if (p == start) {
			break;
		    }
		    charCount--;
		}
	    } else {
		if (type & COUNT_INDICES) {
		    if (charCount <= segSize) {
			dstPtr->byteIndex -= charCount;
			goto backwardCharDone;
		    }
		    charCount -= segSize;
		}
	    }
	}
	dstPtr->byteIndex -= segSize;

	/*
	 * Move back into previous segment.
	 */

	oldPtr = segPtr;
	segPtr = dstPtr->linePtr->segPtr;
	if (segPtr != oldPtr) {
	    for ( ; segPtr->nextPtr != oldPtr; segPtr = segPtr->nextPtr) {
		/* Empty body. */
	    }
	    segSize = segPtr->size;
	    continue;
	}

	/*
	 * Move back to previous line.
	 */

	if (lineIndex < 0) {
	    lineIndex = TkBTreeLinesTo(textPtr, dstPtr->linePtr);
	}
	if (lineIndex == 0) {
	    dstPtr->byteIndex = 0;
	    goto backwardCharDone;
	}
	lineIndex--;
	dstPtr->linePtr = TkBTreeFindLine(dstPtr->tree, textPtr, lineIndex);

	/*
	 * Compute the length of the line and add that to dstPtr->byteIndex.
	 */

	oldPtr = dstPtr->linePtr->segPtr;
	for (segPtr = oldPtr; segPtr != NULL; segPtr = segPtr->nextPtr) {
	    dstPtr->byteIndex += segPtr->size;
	    oldPtr = segPtr;
	}
	segPtr = oldPtr;
	segSize = segPtr->size;
    }

  backwardCharDone:
    if (infoPtr != NULL) {
	TkTextFreeElideInfo(infoPtr);
	ckfree((char *) infoPtr);
    }
}

/*
 *----------------------------------------------------------------------
 *
 * StartEnd --
 *
 *	This function handles modifiers like "wordstart" and "lineend" to
 *	adjust indices forwards or backwards.
 *
 * Results:
 *	If the modifier is successfully parsed then the return value is the
 *	address of the first character after the modifier, and *indexPtr is
 *	updated to reflect the modifier. If there is a syntax error in the
 *	modifier then NULL is returned.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */

static const char *
StartEnd(
    TkText *textPtr,		/* Information about text widget. */
    const char *string,		/* String to parse for additional info about
				 * modifier (count and units). Points to first
				 * character of modifer word. */
    TkTextIndex *indexPtr)	/* Index to modify based on string. */
{
    const char *p;
    size_t length;
    register TkTextSegment *segPtr;
    int modifier;

    /*
     * Find the end of the modifier word.
     */

    for (p = string; isalnum(UCHAR(*p)); p++) {
	/* Empty loop body. */
    }

    length = p-string;
    if ((*string == 'd') &&
	    (strncmp(string, "display", (length > 7 ? 7 : length)) == 0)) {
	modifier = TKINDEX_DISPLAY;
	if (length > 7) {
	    p -= (length - 7);
	}
    } else if ((*string == 'a') &&
	    (strncmp(string, "any", (length > 3 ? 3 : length)) == 0)) {
	modifier = TKINDEX_ANY;
	if (length > 3) {
	    p -= (length - 3);
	}
    } else {
	modifier = TKINDEX_NONE;
    }

    /*
     * If we had a modifier, which we interpreted ok, so now forward to the
     * actual units.
     */

    if (modifier != TKINDEX_NONE) {
	while (isspace(UCHAR(*p))) {
	    p++;
	}
	string = p;
	while ((*p!='\0') && !isspace(UCHAR(*p)) && (*p!='+') && (*p!='-')) {
	    p++;
	}
	length = p - string;
    }

    if ((*string == 'l') && (strncmp(string, "lineend", length) == 0)
	    && (length >= 5)) {
	if (modifier == TKINDEX_DISPLAY) {
	    TkTextFindDisplayLineEnd(textPtr, indexPtr, 1, NULL);
	} else {
	    indexPtr->byteIndex = 0;
	    for (segPtr = indexPtr->linePtr->segPtr; segPtr != NULL;
		    segPtr = segPtr->nextPtr) {
		indexPtr->byteIndex += segPtr->size;
	    }

	    /*
	     * We know '\n' is encoded with a single byte index.
	     */

	    indexPtr->byteIndex -= sizeof(char);
	}
    } else if ((*string == 'l') && (strncmp(string, "linestart", length) == 0)
	    && (length >= 5)) {
	if (modifier == TKINDEX_DISPLAY) {
	    TkTextFindDisplayLineEnd(textPtr, indexPtr, 0, NULL);
	} else {
	    indexPtr->byteIndex = 0;
	}
    } else if ((*string == 'w') && (strncmp(string, "wordend", length) == 0)
	    && (length >= 5)) {
	int firstChar = 1;
	int offset;

	/*
	 * If the current character isn't part of a word then just move
	 * forward one character. Otherwise move forward until finding a
	 * character that isn't part of a word and stop there.
	 */

	if (modifier == TKINDEX_DISPLAY) {
	    TkTextIndexForwChars(textPtr, indexPtr, 0, indexPtr,
		    COUNT_DISPLAY_INDICES);
	}
	segPtr = TkTextIndexToSeg(indexPtr, &offset);
	while (1) {
	    int chSize = 1;

	    if (segPtr->typePtr == &tkTextCharType) {
		Tcl_UniChar ch;

		chSize = Tcl_UtfToUniChar(segPtr->body.chars + offset, &ch);
		if (!Tcl_UniCharIsWordChar(ch)) {
		    break;
		}
		firstChar = 0;
	    }
	    offset += chSize;
	    indexPtr->byteIndex += chSize;
	    if (offset >= segPtr->size) {
		segPtr = TkTextIndexToSeg(indexPtr, &offset);
	    }
	}
	if (firstChar) {
	    if (modifier == TKINDEX_DISPLAY) {
		TkTextIndexForwChars(textPtr, indexPtr, 1, indexPtr,
			COUNT_DISPLAY_INDICES);
	    } else {
		TkTextIndexForwChars(NULL, indexPtr, 1, indexPtr,
			COUNT_INDICES);
	    }
	}
    } else if ((*string == 'w') && (strncmp(string, "wordstart", length) == 0)
	    && (length >= 5)) {
	int firstChar = 1;
	int offset;

	if (modifier == TKINDEX_DISPLAY) {
	    TkTextIndexForwChars(NULL, indexPtr, 0, indexPtr,
		    COUNT_DISPLAY_INDICES);
	}

	/*
	 * Starting with the current character, look for one that's not part
	 * of a word and keep moving backward until you find one. Then if the
	 * character found wasn't the first one, move forward again one
	 * position.
	 */

	segPtr = TkTextIndexToSeg(indexPtr, &offset);
	while (1) {
	    int chSize = 1;

	    if (segPtr->typePtr == &tkTextCharType) {
		Tcl_UniChar ch;

		Tcl_UtfToUniChar(segPtr->body.chars + offset, &ch);
		if (!Tcl_UniCharIsWordChar(ch)) {
		    break;
		}
		if (offset > 0) {
		    chSize = (segPtr->body.chars + offset
			    - Tcl_UtfPrev(segPtr->body.chars + offset,
			    segPtr->body.chars));
		}
		firstChar = 0;
	    }
	    offset -= chSize;
	    indexPtr->byteIndex -= chSize;
	    if (offset < 0) {
		if (indexPtr->byteIndex < 0) {
		    indexPtr->byteIndex = 0;
		    goto done;
		}
		segPtr = TkTextIndexToSeg(indexPtr, &offset);
	    }
	}

	if (!firstChar) {
	    if (modifier == TKINDEX_DISPLAY) {
		TkTextIndexForwChars(textPtr, indexPtr, 1, indexPtr,
			COUNT_DISPLAY_INDICES);
	    } else {
		TkTextIndexForwChars(NULL, indexPtr, 1, indexPtr,
			COUNT_INDICES);
	    }
	}
    } else {
	return NULL;
    }

  done:
    return p;
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */