summaryrefslogtreecommitdiff
path: root/buffer.c
blob: 332a8a278a061d4d3c0a8ca13f57af9d73d2e5ad (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
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
// Text buffers - These store the contents of a file.
// NOTE: All text editing should be done through the two functions
// buffer_insert_text_at_pos and buffer_delete_chars_at_pos

// this is a macro so we get -Wformat warnings
#define buffer_seterr(buffer, ...) \
	snprintf(buffer->error, sizeof buffer->error - 1, __VA_ARGS__)

bool buffer_haserr(TextBuffer *buffer) {
	return buffer->error[0] != '\0';
}

// returns the buffer's last error
char const *buffer_geterr(TextBuffer *buffer) {
	return buffer->error;
}

void buffer_clearerr(TextBuffer *buffer) {
	*buffer->error = '\0';
}

// set the buffer's error to indicate that we're out of memory
static void buffer_out_of_mem(TextBuffer *buffer) {
	buffer_seterr(buffer, "Out of memory.");
}


static void buffer_edit_free(BufferEdit *edit) {
	free(edit->prev_text);
}

static void buffer_clear_redo_history(TextBuffer *buffer) {
	arr_foreach_ptr(buffer->redo_history, BufferEdit, edit) {
		buffer_edit_free(edit);
	}
	arr_clear(buffer->redo_history);
	// if the write pos is in the redo history,
	if (buffer->undo_history_write_pos > arr_len(buffer->undo_history))
		buffer->undo_history_write_pos = U32_MAX; // get rid of it
}

static void buffer_clear_undo_history(TextBuffer *buffer) {
	arr_foreach_ptr(buffer->undo_history, BufferEdit, edit) {
		buffer_edit_free(edit);
	}
	arr_clear(buffer->undo_history);
	buffer->undo_history_write_pos = U32_MAX;
}

static void buffer_clear_undo_redo(TextBuffer *buffer) {
	buffer_clear_undo_history(buffer);
	buffer_clear_redo_history(buffer);
}

bool buffer_empty(TextBuffer *buffer) {
	return buffer->nlines == 1 && buffer->lines[0].len == 0;
}

char const *buffer_get_filename(TextBuffer *buffer) {
	return buffer->filename;
}

bool buffer_is_untitled(TextBuffer *buffer) {
	return streq(buffer->filename, TED_UNTITLED);
}

// add this edit to the undo history
static void buffer_append_edit(TextBuffer *buffer, BufferEdit const *edit) {
	// whenever an edit is made, clear the redo history
	buffer_clear_redo_history(buffer);
	
	arr_add(buffer->undo_history, *edit);
	if (!buffer->undo_history) buffer_out_of_mem(buffer);
}

// add this edit to the redo history
static void buffer_append_redo(TextBuffer *buffer, BufferEdit const *edit) {
	arr_add(buffer->redo_history, *edit);
	if (!buffer->redo_history) buffer_out_of_mem(buffer);
}

static void *buffer_malloc(TextBuffer *buffer, size_t size) {
	void *ret = malloc(size);
	if (!ret) buffer_out_of_mem(buffer);
	return ret;
}

static void *buffer_calloc(TextBuffer *buffer, size_t n, size_t size) {
	void *ret = calloc(n, size);
	if (!ret) buffer_out_of_mem(buffer);
	return ret;
}

static void *buffer_realloc(TextBuffer *buffer, void *p, size_t new_size) {
	void *ret = realloc(p, new_size);
	if (!ret) buffer_out_of_mem(buffer);
	return ret;
}

static char *buffer_strdup(TextBuffer *buffer, char const *src) {
	char *dup = str_dup(src);
	if (!dup) buffer_out_of_mem(buffer);
	return dup;
}

void buffer_create(TextBuffer *buffer, Ted *ted) {
	memset(buffer, 0, sizeof *buffer);
	buffer->store_undo_events = true;
	buffer->ted = ted;
}


void line_buffer_create(TextBuffer *buffer, Ted *ted) {
	buffer_create(buffer, ted);
	buffer->is_line_buffer = true;
	if ((buffer->lines = buffer_calloc(buffer, 1, sizeof *buffer->lines))) {
		buffer->nlines = 1;
		buffer->lines_capacity = 1;
	}
}

// ensures that `p` refers to a valid position.
static void buffer_pos_validate(TextBuffer *buffer, BufferPos *p) {
	if (p->line >= buffer->nlines)
		p->line = buffer->nlines - 1;
	u32 line_len = buffer->lines[p->line].len;
	if (p->index > line_len)
		p->index = line_len;
}

static void buffer_validate_cursor(TextBuffer *buffer) {
	buffer_pos_validate(buffer, &buffer->cursor_pos);
}

static bool buffer_pos_valid(TextBuffer *buffer, BufferPos p) {
	return p.line < buffer->nlines && p.index <= buffer->lines[p.line].len;
}

// are there any unsaved changes?
bool buffer_unsaved_changes(TextBuffer *buffer) {
	if (buffer_is_untitled(buffer) && buffer_empty(buffer))
		return false; // don't worry about empty untitled buffers
	return arr_len(buffer->undo_history) != buffer->undo_history_write_pos;
}

// code point at position.
// returns 0 if the position is invalid. note that it can also return 0 for a valid position, if there's a null character there
char32_t buffer_char_at_pos(TextBuffer *buffer, BufferPos p) {
	if (p.line >= buffer->nlines)
		return 0; // invalid (line too large)
	
	Line *line = &buffer->lines[p.line];
	if (p.index < line->len) {
		return line->str[p.index];
	} else if (p.index > line->len) {
		// invalid (col too large)
		return 0;
	} else {
		return '\n';
	}
}

// returns 0 if pos is at the start of a line
char32_t buffer_char_before_pos(TextBuffer *buffer, BufferPos pos) {
	assert(buffer_pos_valid(buffer, pos));
	if (pos.index == 0) return 0;
	return buffer->lines[pos.line].str[pos.index - 1];
}

// returns 0 if pos is at the end of a line (unlike buffer_char_at_pos)
char32_t buffer_char_after_pos(TextBuffer *buffer, BufferPos pos) {
	assert(buffer_pos_valid(buffer, pos));
	Line *line = &buffer->lines[pos.line];
	if (pos.index >= line->len) return 0;
	return line->str[pos.index];
}

// returns the character to the left of the cursor, or 0 if the cursor at the start of the line.
char32_t buffer_char_before_cursor(TextBuffer *buffer) {
	return buffer_char_before_pos(buffer, buffer->cursor_pos);
}

// returns 0 if cursor is at end of line
char32_t buffer_char_after_cursor(TextBuffer *buffer) {
	return buffer_char_after_pos(buffer, buffer->cursor_pos);
}

BufferPos buffer_start_of_file(TextBuffer *buffer) {
	(void)buffer;
	return (BufferPos){.line = 0, .index = 0};
}

BufferPos buffer_end_of_file(TextBuffer *buffer) {
	return (BufferPos){.line = buffer->nlines - 1, .index = buffer->lines[buffer->nlines-1].len};
}

// Get the font used for this buffer.
static inline Font *buffer_font(TextBuffer *buffer) {
	return buffer->ted->font;
}

// Get the settings used for this buffer.
static inline Settings const *buffer_settings(TextBuffer *buffer) {
	return &buffer->ted->settings;
}

// what programming language is this?
Language buffer_language(TextBuffer *buffer) {
	Settings const *settings = buffer_settings(buffer);
	char const *filename = buffer->filename;
	if (!filename)
		return LANG_NONE;
	size_t filename_len = strlen(filename);

	for (u16 l = 0; l < LANG_COUNT; ++l) {
		char const *extensions = settings->language_extensions[l];
		if (extensions) {
			// extensions is a string with commas separating each extension.
			size_t len = 0;
			for (char const *p = extensions; *p; p += len) {
				if (*p == ',') ++p; // move past comma
				len = strcspn(p, ",");
				if (filename_len >= len && strncmp(&filename[filename_len - len], p, len) == 0) {
					// found a match!
					return (Language)l;
				}
			}
		}
	}
	// no extensions matched
	return LANG_NONE;
}

// NOTE: this string will be invalidated when the line is edited!!!
// only use it briefly!!
static String32 buffer_get_line(TextBuffer *buffer, u32 line_number) {
	Line *line = &buffer->lines[line_number];
	return (String32) {
		.str = line->str, .len = line->len
	};
}

// Returns a simple checksum of the buffer.
// This is only used for testing, and shouldn't be relied on.
static u64 buffer_checksum(TextBuffer *buffer) {
	u64 sum = 0x40fdd49b58ee4b15; // some random prime number
	for (Line *line = buffer->lines, *end = line + buffer->nlines; line != end; ++line) {
		for (char32_t *p = line->str, *p_end = p + line->len; p != p_end; ++p) {
			sum += *p;
			sum *= 0xf033ae1b58e6562f; // another random prime number
			sum += 0x6fcc63c3d38a2bb9; // another random prime number
		}
	}
	return sum;
}

// Get some number of characters of text from the given position in the buffer.
// Returns the number of characters gotten.
// You can pass NULL for text if you just want to know how many characters *could* be accessed before the
// end of the file.
size_t buffer_get_text_at_pos(TextBuffer *buffer, BufferPos pos, char32_t *text, size_t nchars) {
	if (!buffer_pos_valid(buffer, pos)) {
		return 0; // invalid position. no chars for you!
	}
	char32_t *p = text;
	size_t chars_left = nchars;
	Line *line = &buffer->lines[pos.line], *end = buffer->lines + buffer->nlines;
	u32 index = pos.index;
	while (chars_left) {
		u32 chars_from_this_line = line->len - index;
		if (chars_left <= chars_from_this_line) {
			if (p) memcpy(p, line->str + index, chars_left * sizeof *p);
			chars_left = 0;
		} else {
			if (p) {
				memcpy(p, line->str + index, chars_from_this_line * sizeof *p);
				p += chars_from_this_line;
				*p++ = '\n';
			}
			chars_left -= chars_from_this_line+1;
		}
		
		index = 0;
		++line;
		if (chars_left && line == end) {
			// reached end of file before getting full text
			break;
		}
	}
	return nchars - chars_left;
}

// returns a UTF-32 string of at most `nchars` code points from `buffer` starting at `pos`
// the string should be str32_free'd.
String32 buffer_get_str32_text_at_pos(TextBuffer *buffer, BufferPos pos, size_t nchars) {
	String32 s32 = {0};
	size_t len = buffer_get_text_at_pos(buffer, pos, NULL, nchars);
	if (len) {
		char32_t *str = buffer_calloc(buffer, len, sizeof *str);
		if (str) {
			buffer_get_text_at_pos(buffer, pos, str, nchars);
			s32.str = str;
			s32.len = len;
		}
	}
	return s32;
}

// see buffer_get_str32_text_at_pos. returns NULL on failure (out of memory)
// the returned string should be free'd
char *buffer_get_utf8_text_at_pos(TextBuffer *buffer, BufferPos pos, size_t nchars) {
	String32 s32 = buffer_get_str32_text_at_pos(buffer, pos, nchars);
	char *ret = str32_to_utf8_cstr(s32);
	if (!ret) buffer_out_of_mem(buffer);
	str32_free(&s32);
	return ret;
}

// Puts a UTF-8 string containing the contents of the buffer into out.
// Returns the number of bytes.
// To use, first pass NULL for out to get the number of bytes you need to allocate.
size_t buffer_contents_utf8(TextBuffer *buffer, char *out) {
	size_t size = 0;
	char *p = out, x[4];
	for (Line *line = buffer->lines, *end = line + buffer->nlines; line != end; ++line) {
		char32_t *str = line->str;
		for (u32 i = 0, len = line->len; i < len; ++i) {
			size_t bytes = unicode_utf32_to_utf8(p ? p : x, str[i]);
			if (p) p += bytes;
			size += bytes;
		}
		if (line != end - 1) {
			// newline
			if (p) *p++ = '\n';
			size += 1;
		}
	}
	return size;
}

static BufferPos buffer_pos_advance(TextBuffer *buffer, BufferPos pos, size_t nchars) {
	buffer_pos_validate(buffer, &pos);
	size_t chars_left = nchars;
	Line *line = &buffer->lines[pos.line], *end = buffer->lines + buffer->nlines;
	u32 index = pos.index;
	while (line != end) {
		u32 chars_from_this_line = line->len - index;
		if (chars_left <= chars_from_this_line) {
			index += (u32)chars_left;
			pos.index = index;
			pos.line = (u32)(line - buffer->lines);
			return pos;
		}
		chars_left -= chars_from_this_line+1; // +1 for newline
		index = 0;
		++line;
	}
	return buffer_end_of_file(buffer);
}


// returns "p2 - p1", that is, the number of characters between p1 and p2.
static i64 buffer_pos_diff(TextBuffer *buffer, BufferPos p1, BufferPos p2) {
	assert(buffer_pos_valid(buffer, p1));
	assert(buffer_pos_valid(buffer, p2));

	if (p1.line == p2.line) {
		// p1 and p2 are in the same line
		return (i64)p2.index - p1.index;
	}
	i64 factor = 1;
	if (p1.line > p2.line) {
		// switch positions so p2 has the later line
		BufferPos tmp = p1;
		p1 = p2;
		p2 = tmp;
		factor = -1;
	}

	assert(p2.line > p1.line);
	i64 chars_at_end_of_p1_line = buffer->lines[p1.line].len - p1.index + 1; // + 1 for newline
	i64 chars_at_start_of_p2_line = p2.index;
	i64 chars_in_lines_in_between = 0;
	// now we need to add up the lengths of the lines between p1 and p2
	for (Line *line = buffer->lines + (p1.line + 1), *end = buffer->lines + p2.line; line != end; ++line) {
		chars_in_lines_in_between += line->len + 1; // +1 for newline
	}
	i64 total = chars_at_end_of_p1_line + chars_in_lines_in_between + chars_at_start_of_p2_line;
	return total * factor;
}

// returns:
// -1 if p1 comes before p2
// +1 if p1 comes after p2
// 0  if p1 = p2
// faster than buffer_pos_diff (constant time)
static int buffer_pos_cmp(BufferPos p1, BufferPos p2) {
	if (p1.line < p2.line) {
		return -1;
	} else if (p1.line > p2.line) {
		return +1;
	} else {
		if (p1.index < p2.index) {
			return -1;
		} else if (p1.index > p2.index) {
			return +1;
		} else {
			return 0;
		}
	}
}

static bool buffer_pos_eq(BufferPos p1, BufferPos p2) {
	return p1.line == p2.line && p1.index == p2.index;
}

static BufferPos buffer_pos_min(BufferPos p1, BufferPos p2) {
	return buffer_pos_cmp(p1, p2) < 0 ? p1 : p2;
}

static BufferPos buffer_pos_max(BufferPos p1, BufferPos p2) {
	return buffer_pos_cmp(p1, p2) > 0 ? p1 : p2;
}

static void buffer_pos_print(BufferPos p) {
	printf("[" U32_FMT ":" U32_FMT "]", p.line, p.index);
}

static Status buffer_edit_create(TextBuffer *buffer, BufferEdit *edit, BufferPos start, u32 prev_len, u32 new_len) {
	edit->time = time_get_seconds();
	if (prev_len == 0)
		edit->prev_text = NULL; // if there's no previous text, don't allocate anything
	else
		edit->prev_text = calloc(1, prev_len * sizeof *edit->prev_text);
	if (prev_len == 0 || edit->prev_text) {
		edit->pos = start;
		edit->prev_len = prev_len;
		edit->new_len = new_len;
		if (prev_len) {
			size_t chars_gotten = buffer_get_text_at_pos(buffer, start, edit->prev_text, prev_len);
			edit->prev_len = (u32)chars_gotten; // update the previous length, in case it went past the end of the file
		}
		return true;
	} else {
		return false;
	}
}


static void buffer_edit_print(BufferEdit *edit) {
	buffer_pos_print(edit->pos);
	printf(" (" U32_FMT " chars): ", edit->prev_len);
	for (size_t i = 0; i < edit->prev_len; ++i) {
		char32_t c = edit->prev_text[i];
		if (c == '\n')
			printf("\\n");
		else
			printf("%lc", (wint_t)c);
	}
	printf(" => " U32_FMT " chars.\n", edit->new_len);
}

static void buffer_print_undo_history(TextBuffer *buffer) {
	printf("-----------------\n");
	arr_foreach_ptr(buffer->undo_history, BufferEdit, e)
		buffer_edit_print(e);
}

// add this edit to the undo history
// call this before actually changing buffer
static void buffer_edit(TextBuffer *buffer, BufferPos start, u32 prev_len, u32 new_len) {
	BufferEdit edit = {0};
	if (buffer_edit_create(buffer, &edit, start, prev_len, new_len)) {
		edit.chain = buffer->chaining_edits;
		if (buffer->will_chain_edits) buffer->chaining_edits = true;
		buffer_append_edit(buffer, &edit);
	}
}

// change the capacity of edit->prev_text
static Status buffer_edit_resize_prev_text(TextBuffer *buffer, BufferEdit *edit, u32 new_capacity) {
	assert(edit->prev_len <= new_capacity);
	if (new_capacity == 0) {
		free(edit->prev_text);
		edit->prev_text = NULL;
	} else {
		char32_t *new_text = buffer_realloc(buffer, edit->prev_text, new_capacity * sizeof *new_text);
		if (new_text) {
			edit->prev_text = new_text;
		} else {
			return false;
		}
	}
	return true;
}

// does this edit actually make a difference to the buffer?
static bool buffer_edit_does_anything(TextBuffer *buffer, BufferEdit *edit) {
	if (edit->prev_len == edit->new_len) {
		// @OPTIMIZE: compare directly to the buffer contents, rather than extracting them temporarily
		// into new_text.
		char32_t *new_text = buffer_calloc(buffer, edit->new_len, sizeof *new_text);
		if (new_text) {
			size_t len = buffer_get_text_at_pos(buffer, edit->pos, new_text, edit->new_len);
			assert(len == edit->new_len);
			int cmp = memcmp(edit->prev_text, new_text, len * sizeof *new_text);
			free(new_text);
			return cmp != 0;
		} else {
			return false;
		}
	} else {
		return true;
	}
}

// has enough time passed since the last edit that we should create a new one?
static bool buffer_edit_split(TextBuffer *buffer) {
	BufferEdit *last_edit = arr_lastp(buffer->undo_history);
	if (!last_edit) return true;
	if (buffer->will_chain_edits) return true;
	if (buffer->chaining_edits) return false;
	double curr_time = time_get_seconds();
	double undo_time_cutoff = buffer_settings(buffer)->undo_save_time; // only keep around edits for this long (in seconds).
	return curr_time - last_edit->time > undo_time_cutoff;
}

// removes the last edit in the undo history if it doesn't do anything
static void buffer_remove_last_edit_if_empty(TextBuffer *buffer) {
	if (buffer->store_undo_events) {
		BufferEdit *last_edit = arr_lastp(buffer->undo_history);
		if (last_edit && !buffer_edit_does_anything(buffer, last_edit)) {
			buffer_edit_free(last_edit);
			arr_remove_last(buffer->undo_history);
		}
	}
}

// returns true if allocation was succesful
static Status buffer_line_set_len(TextBuffer *buffer, Line *line, u32 new_len) {
	if (new_len >= 8) {
		u32 curr_capacity = (u32)1 << (32 - util_count_leading_zeroes(line->len));

		if (new_len >= curr_capacity) {
			u8 leading_zeroes = util_count_leading_zeroes(new_len);
			if (leading_zeroes == 0) {
				// this line is too big
				return false;
			} else {
				u32 new_capacity = (u32)1 << (32 - leading_zeroes);
				assert(new_capacity > new_len);
				char32_t *new_str = buffer_realloc(buffer, line->str, new_capacity * sizeof *line->str);
				if (!new_str) {
					// allocation failed ):
					return false;
				}
				// allocation successful
				line->str = new_str;
			}
		}
	} else if (line->len == 0) {
		// start by allocating 8 code points
		line->str = buffer_malloc(buffer, 8 * sizeof *line->str);
		if (!line->str) {
			// ):
			return false;
		}
	}
	line->len = new_len;
	return true;
}

// grow capacity of lines array
// returns true if successful
static Status buffer_lines_set_min_capacity(TextBuffer *buffer, Line **lines, u32 *lines_capacity, u32 minimum_capacity) {
	while (minimum_capacity >= *lines_capacity) {
		// allocate more lines
		u32 new_capacity = *lines_capacity * 2;
		Line *new_lines = buffer_realloc(buffer, *lines, new_capacity * sizeof(Line));
		if (new_lines) {
			*lines = new_lines;
			// zero new lines
			memset(new_lines + *lines_capacity, 0, (new_capacity - *lines_capacity) * sizeof(Line));
			*lines_capacity = new_capacity;
		} else {
			return false;
		}
	}
	return true;
}

static void buffer_line_append_char(TextBuffer *buffer, Line *line, char32_t c) {
	if (buffer_line_set_len(buffer, line, line->len + 1))
		line->str[line->len-1] = c;
}

static void buffer_line_free(Line *line) {
	free(line->str);
}

// Free a buffer. Once a buffer is freed, you can call buffer_create on it again.
// Does not free the pointer `buffer` (buffer might not have even been allocated with malloc)
void buffer_free(TextBuffer *buffer) {
	Line *lines = buffer->lines;
	u32 nlines = buffer->nlines;
	for (u32 i = 0; i < nlines; ++i) {
		buffer_line_free(&lines[i]);
	}
	free(lines);
	free(buffer->filename);

	arr_foreach_ptr(buffer->undo_history, BufferEdit, edit)
		buffer_edit_free(edit);
	arr_foreach_ptr(buffer->redo_history, BufferEdit, edit)
		buffer_edit_free(edit);

	arr_free(buffer->undo_history);
	arr_free(buffer->redo_history);
	memset(buffer, 0, sizeof *buffer);
}

// clear contents, undo history, etc. of a buffer
void buffer_clear(TextBuffer *buffer) {
	bool is_line_buffer = buffer->is_line_buffer;
	Ted *ted = buffer->ted;
	char error[sizeof buffer->error];
	memcpy(error, buffer->error, sizeof error);
	buffer_free(buffer);
	if (is_line_buffer) {
		line_buffer_create(buffer, ted);
	} else {
		buffer_create(buffer, ted);
	}
	memcpy(buffer->error, error, sizeof error);
}


// print the contents of a buffer to stdout
static void buffer_print(TextBuffer const *buffer) {
	printf("\033[2J\033[;H"); // clear terminal screen
	Line *lines = buffer->lines;
	u32 nlines = buffer->nlines;
	
	for (u32 i = 0; i < nlines; ++i) {
		Line *line = &lines[i];
		for (u32 j = 0; j < line->len; ++j) {
			// on windows, this will print characters outside the Basic Multilingual Plane incorrectly
			// but this function is just for debugging anyways
			putwchar((wchar_t)line->str[j]);
		}
	}
	fflush(stdout);
}

static u32 buffer_index_to_column(TextBuffer *buffer, u32 line, u32 index) {
	char32_t *str = buffer->lines[line].str;
	u32 col = 0;
	uint tab_width = buffer_settings(buffer)->tab_width;
	for (u32 i = 0; i < index; ++i) {
		switch (str[i]) {
		case '\t': {
			do
				++col;
			while (col % tab_width);
		} break;
		default:
			++col;
			break;
		}
	}
	return col;
}

static u32 buffer_column_to_index(TextBuffer *buffer, u32 line, u32 column) {
	if (line >= buffer->nlines) {
		assert(0);
		return 0;
	}
	char32_t *str = buffer->lines[line].str;
	u32 len = buffer->lines[line].len;
	u32 col = 0;
	uint tab_width = buffer_settings(buffer)->tab_width;
	for (u32 i = 0; i < len; ++i) {
		switch (str[i]) {
		case '\t': {
			do {
				if (col == column)
					return i;
				++col;
			} while (col % tab_width);
		} break;
		default:
			if (col == column)
				return i;
			++col;
			break;
		}
	}
	return len;
}

// returns the number of lines of text in the buffer into *lines (if not NULL),
// and the number of columns of text, i.e. the number of columns in the longest line displayed, into *cols (if not NULL)
void buffer_text_dimensions(TextBuffer *buffer, u32 *lines, u32 *columns) {
	if (lines) {
		*lines = buffer->nlines;
	}
	if (columns) {
		u32 longest_line = 0;
		// which line on screen is the longest?
		for (u32 l = buffer->first_line_on_screen; l <= buffer->last_line_on_screen && l < buffer->nlines; ++l) {
			Line *line = &buffer->lines[l];
			longest_line = max_u32(longest_line, line->len);
		}
		*columns = longest_line;
	}
}


// returns the number of rows of text that can fit in the buffer
float buffer_display_lines(TextBuffer *buffer) {
	return (buffer->y2 - buffer->y1) / text_font_char_height(buffer_font(buffer));
}

// returns the number of columns of text that can fit in the buffer
float buffer_display_cols(TextBuffer *buffer) {
	return (buffer->x2 - buffer->x1) / text_font_char_width(buffer_font(buffer));
}

// make sure we don't scroll too far
static void buffer_correct_scroll(TextBuffer *buffer) {
	if (buffer->scroll_x < 0)
		buffer->scroll_x = 0;
	if (buffer->scroll_y < 0)
		buffer->scroll_y = 0;
	u32 nlines, ncols;
	buffer_text_dimensions(buffer, &nlines, &ncols);
	double max_scroll_x = (double)ncols  - buffer_display_cols(buffer);
	max_scroll_x += 2; // allow "overscroll" (makes it so you can see the cursor when it's on the right side of the screen)
	double max_scroll_y = (double)nlines - buffer_display_lines(buffer);
	if (max_scroll_x <= 0) {
		buffer->scroll_x = 0;
	} else if (buffer->scroll_x > max_scroll_x) {
		buffer->scroll_x = max_scroll_x;
	}

	if (max_scroll_y <= 0) {
		buffer->scroll_y = 0;
	} else if (buffer->scroll_y > max_scroll_y) {
		buffer->scroll_y = max_scroll_y;
	}
}

void buffer_scroll(TextBuffer *buffer, double dx, double dy) {
	buffer->scroll_x += dx;
	buffer->scroll_y += dy;
	buffer_correct_scroll(buffer);
}

void buffer_page_up(TextBuffer *buffer, i64 npages) {
	buffer_scroll(buffer, 0, (double)-npages * buffer_display_lines(buffer));
}

void buffer_page_down(TextBuffer *buffer, i64 npages) {
	buffer_scroll(buffer, 0, (double)+npages * buffer_display_lines(buffer));
}

// returns the position of the character at the given position in the buffer.
v2 buffer_pos_to_pixels(TextBuffer *buffer, BufferPos pos) {
	u32 line = pos.line, index = pos.index;
	// we need to convert the index to a column
	u32 col = buffer_index_to_column(buffer, line, index);
	Font *font = buffer_font(buffer);
	float x = (float)((double)col  - buffer->scroll_x) * text_font_char_width(font) + buffer->x1;
	float y = (float)((double)line - buffer->scroll_y) * text_font_char_height(font) + buffer->y1;
	return V2(x, y);
}

// convert pixel coordinates to a position in the buffer, selecting the closest character.
// returns false if the position is not inside the buffer, but still sets *pos to the closest character.
bool buffer_pixels_to_pos(TextBuffer *buffer, v2 pixel_coords, BufferPos *pos) {
	bool ret = true;
	float x = pixel_coords.x, y = pixel_coords.y;
	Font *font = buffer_font(buffer);
	pos->line = pos->index = 0;

	x -= buffer->x1;
	y -= buffer->y1;
	x /= text_font_char_width(font);
	y /= text_font_char_height(font);
	double display_col = (double)x;
	if (display_col < 0) {
		display_col = 0;
		ret = false;
	}
	double display_cols = buffer_display_cols(buffer), display_lines = buffer_display_lines(buffer);
	if (display_col >= display_cols) {
		display_col = display_cols - 1;
		ret = false;
	}
	double display_line = (double)y;
	if (display_line < 0) {
		display_line = 0;
		ret = false;
	}
	if (display_line >= display_lines) {
		display_line = display_lines - 1;
		ret = false;
	}
	
	u32 line = (u32)floor(display_line + buffer->scroll_y);
	if (line >= buffer->nlines) line = buffer->nlines - 1;
	u32 column = (u32)round(display_col + buffer->scroll_x);
	u32 index = buffer_column_to_index(buffer, line, column);
	pos->line = line;
	pos->index = index;
	
	return ret;
}

// clip the rectangle so it's all inside the buffer. returns true if there's any rectangle left.
static bool buffer_clip_rect(TextBuffer *buffer, Rect *r) {
	float x1, y1, x2, y2;
	rect_coords(*r, &x1, &y1, &x2, &y2);
	if (x1 > buffer->x2 || y1 > buffer->y2 || x2 < buffer->x1 || y2 < buffer->y1) {
		r->pos = r->size = V2(0, 0);
		return false;
	}
	if (x1 < buffer->x1) x1 = buffer->x1;
	if (y1 < buffer->y1) y1 = buffer->y1;
	if (x2 > buffer->x2) x2 = buffer->x2;
	if (y2 > buffer->y2) y2 = buffer->y2;
	*r = rect4(x1, y1, x2, y2);
	return true;
}


void buffer_scroll_to_pos(TextBuffer *buffer, BufferPos pos) {
	Settings const *settings = buffer_settings(buffer);
	double line = pos.line;
	double col = buffer_index_to_column(buffer, pos.line, pos.index);
	double display_lines = buffer_display_lines(buffer);
	double display_cols = buffer_display_cols(buffer);
	double scroll_x = buffer->scroll_x, scroll_y = buffer->scroll_y;
	double scrolloff = settings->scrolloff;

	// scroll left if pos is off screen in that direction
	double max_scroll_x = col - scrolloff;
	scroll_x = mind(scroll_x, max_scroll_x);
	// scroll right
	double min_scroll_x = col - display_cols + scrolloff;
	scroll_x = maxd(scroll_x, min_scroll_x);
	// scroll up
	double max_scroll_y = line - scrolloff;
	scroll_y = mind(scroll_y, max_scroll_y);
	// scroll down
	double min_scroll_y = line - display_lines + scrolloff;
	scroll_y = maxd(scroll_y, min_scroll_y);

	buffer->scroll_x = scroll_x;
	buffer->scroll_y = scroll_y;
	buffer_correct_scroll(buffer); // it's possible that min/max_scroll_x/y go too far
}

// if the cursor is offscreen, this will scroll to make it onscreen.
void buffer_scroll_to_cursor(TextBuffer *buffer) {
	buffer_scroll_to_pos(buffer, buffer->cursor_pos);
}

// scroll so that the cursor is in the center of the screen
void buffer_center_cursor(TextBuffer *buffer) {
	double cursor_line = buffer->cursor_pos.line;
	double cursor_col  = buffer_index_to_column(buffer, (u32)cursor_line, buffer->cursor_pos.index);
	double display_lines = buffer_display_lines(buffer);
	double display_cols = buffer_display_cols(buffer);
	
	buffer->scroll_x = cursor_col - display_cols * 0.5;
	buffer->scroll_y = cursor_line - display_lines * 0.5;

	buffer_correct_scroll(buffer);
}

// move left (if `by` is negative) or right (if `by` is positive) by the specified amount.
// returns the signed number of characters successfully moved (it could be less in magnitude than `by` if the beginning of the file is reached)
i64 buffer_pos_move_horizontally(TextBuffer *buffer, BufferPos *p, i64 by) {
	buffer_pos_validate(buffer, p);
	if (by < 0) {
		by = -by;
		i64 by_start = by;
		
		while (by > 0) {
			if (by <= p->index) {
				// no need to go to the previous line
				p->index -= (u32)by;
				by = 0;
			} else {
				by -= p->index;
				p->index = 0;
				if (p->line == 0) {
					// beginning of file reached
					return -(by_start - by);
				}
				--by; // count newline as a character
				// previous line
				--p->line;
				p->index = buffer->lines[p->line].len;
			}
		}
		return -by_start;
	} else if (by > 0) {
		i64 by_start = by;
		if (p->line >= buffer->nlines)
			*p = buffer_end_of_file(buffer); // invalid position; move to end of buffer
		Line *line = &buffer->lines[p->line];
		while (by > 0) {
			if (by <= line->len - p->index) {
				p->index += (u32)by;
				by = 0;
			} else {
				by -= line->len - p->index;
				p->index = line->len;
				if (p->line >= buffer->nlines - 1) {
					// end of file reached
					return by_start - by;
				}
				--by;
				++p->line;
				p->index = 0;
			}
		}
		return by_start;
	}
	return 0;
}

// same as buffer_pos_move_horizontally, but for up and down.
i64 buffer_pos_move_vertically(TextBuffer *buffer, BufferPos *pos, i64 by) {
	buffer_pos_validate(buffer, pos);
	// moving up/down should preserve the column, not the index.
	// consider:
	// tab|hello world
	// tab|tab|more text
	// the character above the 'm' is the 'o', not the 'e'
	if (by < 0) {
		by = -by;
		u32 column = buffer_index_to_column(buffer, pos->line, pos->index);
		if (pos->line < by) {
			i64 ret = pos->line;
			pos->line = 0;
			return -ret;
		}
		pos->line -= (u32)by;
		pos->index = buffer_column_to_index(buffer, pos->line, column);
		u32 line_len = buffer->lines[pos->line].len;
		if (pos->index >= line_len) pos->index = line_len;
		return -by;
	} else if (by > 0) {
		u32 column = buffer_index_to_column(buffer, pos->line, pos->index);
		if (pos->line + by >= buffer->nlines) {
			i64 ret = buffer->nlines-1 - pos->line;
			pos->line = buffer->nlines-1;
			return ret;
		}
		pos->line += (u32)by;
		pos->index = buffer_column_to_index(buffer, pos->line, column);
		u32 line_len = buffer->lines[pos->line].len;
		if (pos->index >= line_len) pos->index = line_len;
		return by;
	}
	return 0;
}

i64 buffer_pos_move_left(TextBuffer *buffer, BufferPos *pos, i64 by) {
	return -buffer_pos_move_horizontally(buffer, pos, -by);
}

i64 buffer_pos_move_right(TextBuffer *buffer, BufferPos *pos, i64 by) {
	return +buffer_pos_move_horizontally(buffer, pos, +by);
}

i64 buffer_pos_move_up(TextBuffer *buffer, BufferPos *pos, i64 by) {
	return -buffer_pos_move_vertically(buffer, pos, -by);
}

i64 buffer_pos_move_down(TextBuffer *buffer, BufferPos *pos, i64 by) {
	return +buffer_pos_move_vertically(buffer, pos, +by);
}

void buffer_cursor_move_to_pos(TextBuffer *buffer, BufferPos pos) {
	buffer_pos_validate(buffer, &pos);
	buffer->cursor_pos = pos;
	buffer->selection = false;
	buffer_scroll_to_cursor(buffer);
}

i64 buffer_cursor_move_left(TextBuffer *buffer, i64 by) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_left(buffer, &cur_pos, by);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

i64 buffer_cursor_move_right(TextBuffer *buffer, i64 by) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_right(buffer, &cur_pos, by);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

i64 buffer_cursor_move_up(TextBuffer *buffer, i64 by) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_up(buffer, &cur_pos, by);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

i64 buffer_cursor_move_down(TextBuffer *buffer, i64 by) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_down(buffer, &cur_pos, by);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

// Is this character a "word" character?
// This determines how buffer_pos_move_words (i.e. ctrl+left/right) works
static bool is_word(char32_t c) {
	return c > WCHAR_MAX || c == '_' || iswalnum((wint_t)c);
}

static bool is_space(char32_t c) {
	return c > WCHAR_MAX || iswspace((wint_t)c);
}

// move left / right by the specified number of words
// returns the number of words successfully moved forward
i64 buffer_pos_move_words(TextBuffer *buffer, BufferPos *pos, i64 nwords) {
	buffer_pos_validate(buffer, pos);
	if (nwords > 0) {
		for (i64 i = 0; i < nwords; ++i) { // move forward one word `nwords` times
			Line *line = &buffer->lines[pos->line];
			u32 index = pos->index;
			char32_t const *str = line->str;
			if (index == line->len) {
				if (pos->line >= buffer->nlines - 1) {
					// end of file reached
					return i;
				} else {
					// end of line reached; move to next line
					++pos->line;
					pos->index = 0;
				}
			} else {
				// move past any whitespace before the word
				while (index < line->len && is_space(str[index]))
					++index;
				
				bool starting_isword = is_word(str[index]) != 0;
				for (; index < line->len && !is_space(str[index]); ++index) {
					bool this_isword = is_word(str[index]) != 0;
					if (this_isword != starting_isword) {
						// either the position *was* on an alphanumeric character and now it's not
						// or it wasn't and now it is.
						break;
					}
				}
				
				// move past any whitespace after the word
				while (index < line->len && is_space(str[index]))
					++index;
				pos->index = index;
			}
		}
		return nwords;
	} else if (nwords < 0) {
		nwords = -nwords;
		for (i64 i = 0; i < nwords; ++i) {
			Line *line = &buffer->lines[pos->line];
			u32 index = pos->index;
			char32_t const *str = line->str;
			if (index == 0) {
				if (pos->line == 0) {
					// start of file reached
					return i;
				} else {
					// start of line reached; move to previous line
					--pos->line;
					pos->index = buffer->lines[pos->line].len;
				}
			} else {
				--index;

				while (index > 0 && is_space(str[index])) // skip whitespace after word
					--index;
				if (index > 0) {
					bool starting_isword = is_word(str[index]) != 0;
					while (true) {
						bool this_isword = is_word(str[index]) != 0;
						if (is_space(str[index]) || this_isword != starting_isword) {
							++index;
							break;
						}
						if (index == 0) break;
						--index;
					}
				}
				pos->index = index;
			}
		}
	}
	return 0;
}

i64 buffer_pos_move_left_words(TextBuffer *buffer, BufferPos *pos, i64 nwords) {
	return -buffer_pos_move_words(buffer, pos, -nwords);
}

i64 buffer_pos_move_right_words(TextBuffer *buffer, BufferPos *pos, i64 nwords) {
	return +buffer_pos_move_words(buffer, pos, +nwords);
}

i64 buffer_cursor_move_left_words(TextBuffer *buffer, i64 nwords) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_left_words(buffer, &cur_pos, nwords);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

i64 buffer_cursor_move_right_words(TextBuffer *buffer, i64 nwords) {
	BufferPos cur_pos = buffer->cursor_pos;
	i64 ret = buffer_pos_move_right_words(buffer, &cur_pos, nwords);
	buffer_cursor_move_to_pos(buffer, cur_pos);
	return ret;
}

// Returns the position corresponding to the start of the given line.
BufferPos buffer_pos_start_of_line(TextBuffer *buffer, u32 line) {
	(void)buffer;
	return (BufferPos){
		.line = line,
		.index = 0
	};
}

BufferPos buffer_pos_end_of_line(TextBuffer *buffer, u32 line) {
	return (BufferPos){
		.line = line,
		.index = buffer->lines[line].len
	};
}

void buffer_cursor_move_to_start_of_line(TextBuffer *buffer) {
	buffer_cursor_move_to_pos(buffer, buffer_pos_start_of_line(buffer, buffer->cursor_pos.line));
}

void buffer_cursor_move_to_end_of_line(TextBuffer *buffer) {
	buffer_cursor_move_to_pos(buffer, buffer_pos_end_of_line(buffer, buffer->cursor_pos.line));
}

void buffer_cursor_move_to_start_of_file(TextBuffer *buffer) {
	buffer_cursor_move_to_pos(buffer, buffer_start_of_file(buffer));
}

void buffer_cursor_move_to_end_of_file(TextBuffer *buffer) {
	buffer_cursor_move_to_pos(buffer, buffer_end_of_file(buffer));
}


static void buffer_lines_modified(TextBuffer *buffer, u32 first_line, u32 last_line) {
	assert(last_line >= first_line);
	buffer->modified = true;
	if (first_line < buffer->frame_earliest_line_modified)
		buffer->frame_earliest_line_modified = first_line;
	if (last_line > buffer->frame_latest_line_modified)
		buffer->frame_latest_line_modified = last_line;
}

// insert `number` empty lines starting at index `where`.
static Status buffer_insert_lines(TextBuffer *buffer, u32 where, u32 number) {
	assert(!buffer->is_line_buffer);

	u32 old_nlines = buffer->nlines;
	u32 new_nlines = old_nlines + number;
	if (buffer_lines_set_min_capacity(buffer, &buffer->lines, &buffer->lines_capacity, new_nlines)) {
		assert(where <= old_nlines);
		// make space for new lines
		memmove(buffer->lines + where + (new_nlines - old_nlines),
			buffer->lines + where,
			(old_nlines - where) * sizeof *buffer->lines);
		// zero new lines
		memset(buffer->lines + where, 0, number * sizeof *buffer->lines);
		buffer->nlines = new_nlines;
		return true;
	}
	return false;
}

// inserts the given text, returning the position of the end of the text
BufferPos buffer_insert_text_at_pos(TextBuffer *buffer, BufferPos pos, String32 str) {
	if (buffer->view_only)
		return pos;
	if (str.len > U32_MAX) {
		buffer_seterr(buffer, "Inserting too much text (length: %zu).", str.len);
		BufferPos ret = {0,0};
		return ret;
	}

	if (buffer->is_line_buffer) {
		// remove all the newlines from str.
		str32_remove_all_instances_of_char(&str, '\n');
	}

	if (str.len == 0) {
		// no text to insert
		return pos;
	}

	if (buffer->store_undo_events) {
		BufferEdit *last_edit = arr_lastp(buffer->undo_history);
		i64 where_in_last_edit = last_edit ? buffer_pos_diff(buffer, last_edit->pos, pos) : -1;
		// create a new edit, rather than adding to the old one if:
		bool create_new_edit = where_in_last_edit < 0 || where_in_last_edit > last_edit->new_len // insertion is happening outside the previous edit,
			|| buffer_edit_split(buffer); // or enough time has elapsed to warrant a new one.

		if (create_new_edit) {
			// create a new edit for this insertion
			buffer_edit(buffer, pos, 0, (u32)str.len);
		} else {
			// merge this edit into the previous one.
			last_edit->new_len += (u32)str.len;
		}

	}

	u32 line_idx = pos.line;
	u32 index = pos.index;
	Line *line = &buffer->lines[line_idx];

	// `text` could consist of multiple lines, e.g. U"line 1\nline 2",
	// so we need to go through them one by one
	u32 n_added_lines = (u32)str32_count_char(str, '\n');
	if (n_added_lines) {
		if (buffer_insert_lines(buffer, line_idx + 1, n_added_lines)) {
			line = &buffer->lines[line_idx]; // fix pointer
			// move any text past the cursor on this line to the last added line.
			Line *last_line = &buffer->lines[line_idx + n_added_lines];
			u32 chars_moved = line->len - index;
			if (chars_moved) {
				if (buffer_line_set_len(buffer, last_line, chars_moved)) {
					memcpy(last_line->str, line->str + index, chars_moved * sizeof(char32_t));
					line->len  -= chars_moved;
				}
			}
		}
	}


	while (str.len) {
		u32 text_line_len = (u32)str32chr(str, '\n');
		u32 old_len = line->len;
		u32 new_len = old_len + text_line_len;
		if (new_len > old_len) { // handles both overflow and empty text lines
			if (buffer_line_set_len(buffer, line, new_len)) {
				// make space for text
				memmove(line->str + index + (new_len - old_len),
					line->str + index,
					(old_len - index) * sizeof(char32_t));
				// insert text
				memcpy(line->str + index, str.str, text_line_len * sizeof(char32_t));
			}

			str.str += text_line_len;
			str.len -= text_line_len;
			index += text_line_len;
		}
		if (str.len) {
			// we've got a newline.
			line_idx += 1;
			index = 0;
			++line;
			++str.str;
			--str.len;
		}
	}

	// We need to put this after the end so the emptiness-checking is done after the edit is made.
	buffer_remove_last_edit_if_empty(buffer);

	buffer_lines_modified(buffer, pos.line, line_idx);

	BufferPos b = {.line = line_idx, .index = index};
	return b;
}

// Select (or add to selection) everything between the cursor and pos, and move the cursor to pos
void buffer_select_to_pos(TextBuffer *buffer, BufferPos pos) {
	if (!buffer->selection)
		buffer->selection_pos = buffer->cursor_pos;
	buffer_cursor_move_to_pos(buffer, pos);
	buffer->selection = !buffer_pos_eq(buffer->cursor_pos, buffer->selection_pos); // disable selection if cursor_pos = selection_pos.
}

// Like shift+left in most editors, move cursor nchars chars to the left, selecting everything in between
void buffer_select_left(TextBuffer *buffer, i64 nchars) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_left(buffer, &cpos, nchars);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_right(TextBuffer *buffer, i64 nchars) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_right(buffer, &cpos, nchars);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_down(TextBuffer *buffer, i64 nchars) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_down(buffer, &cpos, nchars);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_up(TextBuffer *buffer, i64 nchars) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_up(buffer, &cpos, nchars);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_left_words(TextBuffer *buffer, i64 nwords) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_left_words(buffer, &cpos, nwords);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_right_words(TextBuffer *buffer, i64 nwords) {
	BufferPos cpos = buffer->cursor_pos;
	buffer_pos_move_right_words(buffer, &cpos, nwords);
	buffer_select_to_pos(buffer, cpos);
}

void buffer_select_to_start_of_line(TextBuffer *buffer) {
	buffer_select_to_pos(buffer, buffer_pos_start_of_line(buffer, buffer->cursor_pos.line));
}

void buffer_select_to_end_of_line(TextBuffer *buffer) {
	buffer_select_to_pos(buffer, buffer_pos_end_of_line(buffer, buffer->cursor_pos.line));
}

void buffer_select_to_start_of_file(TextBuffer *buffer) {
	buffer_select_to_pos(buffer, buffer_start_of_file(buffer));
}

void buffer_select_to_end_of_file(TextBuffer *buffer) {
	buffer_select_to_pos(buffer, buffer_end_of_file(buffer));
}

// select the word the cursor is inside of
void buffer_select_word(TextBuffer *buffer) {
	BufferPos start_pos = buffer->cursor_pos, end_pos = buffer->cursor_pos;
	buffer_pos_move_left_words(buffer, &start_pos, 1);
	buffer_pos_move_right_words(buffer, &end_pos, 1);
	buffer_cursor_move_to_pos(buffer, end_pos);
	buffer_select_to_pos(buffer, start_pos);
}

// select the line the cursor is currently on
void buffer_select_line(TextBuffer *buffer) {
	u32 line = buffer->cursor_pos.line;
	if (line == buffer->nlines - 1)
		buffer_cursor_move_to_pos(buffer, buffer_pos_end_of_line(buffer, line));
	else
		buffer_cursor_move_to_pos(buffer, buffer_pos_start_of_line(buffer, line + 1));
	buffer_select_to_pos(buffer, buffer_pos_start_of_line(buffer, line));
}

void buffer_select_all(TextBuffer *buffer) {
	buffer_cursor_move_to_pos(buffer, buffer_start_of_file(buffer));
	buffer_select_to_pos(buffer, buffer_end_of_file(buffer));
}

// stop selecting
void buffer_disable_selection(TextBuffer *buffer) {
	if (buffer->selection) {
		buffer->cursor_pos = buffer->selection_pos;
		buffer->selection = false;
	}
}

static void buffer_shorten_line(Line *line, u32 new_len) {
	assert(line->len >= new_len);
	line->len = new_len; // @OPTIMIZE(memory): decrease line capacity
}

// decrease the number of lines in the buffer.
// DOES NOT DO ANYTHING TO THE LINES REMOVED! YOU NEED TO FREE THEM YOURSELF!
static void buffer_shorten(TextBuffer *buffer, u32 new_nlines) {
	buffer->nlines = new_nlines; // @OPTIMIZE(memory): decrease lines capacity
}

// delete `nlines` lines starting from index `first_line_idx`
static void buffer_delete_lines(TextBuffer *buffer, u32 first_line_idx, u32 nlines) {
	assert(first_line_idx < buffer->nlines);
	assert(first_line_idx+nlines <= buffer->nlines);
	Line *first_line = &buffer->lines[first_line_idx];
	Line *end = first_line + nlines;

	for (Line *l = first_line; l != end; ++l) {
		buffer_line_free(l);
	}
	memmove(first_line, end, (size_t)(buffer->lines + buffer->nlines - end) * sizeof(Line));
}

void buffer_delete_chars_at_pos(TextBuffer *buffer, BufferPos pos, i64 nchars_) {
	if (buffer->view_only) return;
	if (nchars_ < 0) {
		buffer_seterr(buffer, "Deleting negative characters (specifically, " I64_FMT ").", nchars_);
		return;
	}
	if (nchars_ <= 0) return;

	if (nchars_ > U32_MAX) nchars_ = U32_MAX;
	u32 nchars = (u32)nchars_;

	// Correct nchars in case it goes past the end of the file.
	// Why do we need to correct it?
	// When generating undo events, we allocate nchars characters of memory (see buffer_edit below).
	// Not doing this might also cause other bugs, best to keep it here just in case.
	nchars = (u32)buffer_get_text_at_pos(buffer, pos, NULL, nchars);

	if (buffer->store_undo_events) {
		// we need to make sure the undo history keeps track of the edit.
		// we will either combine it with the previous BufferEdit, or create a new
		// one with just this deletion.
		
		BufferEdit *last_edit = arr_lastp(buffer->undo_history);
		BufferPos edit_start = {0}, edit_end = {0};
		if (last_edit) {
			edit_start = last_edit->pos;
			edit_end = buffer_pos_advance(buffer, edit_start, last_edit->new_len);
		}
		BufferPos del_start = pos, del_end = buffer_pos_advance(buffer, del_start, nchars);

		bool create_new_edit = 
			!last_edit || // if there is no previous edit to combine it with
			buffer_pos_cmp(del_end, edit_start) < 0 || // or if delete does not overlap last_edit
			buffer_pos_cmp(del_start, edit_end) > 0 ||
			buffer_edit_split(buffer); // or if enough time has passed to warrant a new edit

		if (create_new_edit) {
			// create a new edit
			buffer_edit(buffer, pos, nchars, 0);
		} else {
			if (buffer_pos_cmp(del_start, edit_start) < 0) {
				// if we delete characters before the last edit, add them onto the start of prev_text.
				i64 chars_before_edit = buffer_pos_diff(buffer, del_start, edit_start);
				assert(chars_before_edit > 0);
				u32 updated_prev_len = (u32)(chars_before_edit + last_edit->prev_len);
				if (buffer_edit_resize_prev_text(buffer, last_edit, updated_prev_len)) {
					// make space
					memmove(last_edit->prev_text + chars_before_edit, last_edit->prev_text, last_edit->prev_len * sizeof(char32_t));
					// prepend these chracters to the edit's text
					buffer_get_text_at_pos(buffer, del_start, last_edit->prev_text, (size_t)chars_before_edit);

					last_edit->prev_len = updated_prev_len;
				}
				// move edit position back, because we started deleting from an earlier point
				last_edit->pos = del_start;
			}
			if (buffer_pos_cmp(del_end, edit_end) > 0) {
				// if we delete characters after the last edit, add them onto the end of prev_text.
				i64 chars_after_edit = buffer_pos_diff(buffer, edit_end, del_end);
				assert(chars_after_edit > 0);
				u32 updated_prev_len = (u32)(chars_after_edit + last_edit->prev_len);
				if (buffer_edit_resize_prev_text(buffer, last_edit, updated_prev_len)) {
					// append these characters to the edit's text
					buffer_get_text_at_pos(buffer, edit_end, last_edit->prev_text + last_edit->prev_len, (size_t)chars_after_edit);
					last_edit->prev_len = updated_prev_len;
				}
			}
			
			// we might have deleted text inside the edit.
			i64 new_text_del_start = buffer_pos_diff(buffer, edit_start, del_start);
			if (new_text_del_start < 0) new_text_del_start = 0;
			i64 new_text_del_end = buffer_pos_diff(buffer, edit_start, del_end);
			if (new_text_del_end > last_edit->new_len) new_text_del_end = last_edit->new_len;
			if (new_text_del_end > new_text_del_start) {
				// shrink length to get rid of that text
				last_edit->new_len -= (u32)(new_text_del_end - new_text_del_start);
			}
		}

	}

	u32 line_idx = pos.line;
	u32 index = pos.index;
	Line *line = &buffer->lines[line_idx], *lines_end = &buffer->lines[buffer->nlines];
	if (nchars + index > line->len) {
		// delete rest of line
		nchars -= line->len - index + 1; // +1 for the newline that got deleted
		buffer_shorten_line(line, index);

		Line *last_line; // last line in lines deleted
		for (last_line = line + 1; last_line < lines_end && nchars > last_line->len; ++last_line) {
			nchars -= last_line->len+1;
		}
		if (last_line == lines_end) {
			assert(nchars == 0); // we already shortened nchars to go no further than the end of the file
			// delete everything to the end of the file
			for (u32 idx = line_idx + 1; idx < buffer->nlines; ++idx) {
				buffer_line_free(&buffer->lines[idx]);
			}
			buffer_shorten(buffer, line_idx + 1);
		} else {
			// join last_line[nchars:] to line.
			u32 last_line_chars_left = (u32)(last_line->len - nchars);
			u32 old_len = line->len;
			if (buffer_line_set_len(buffer, line, old_len + last_line_chars_left)) {
				memcpy(line->str + old_len, last_line->str + nchars, last_line_chars_left * sizeof(char32_t));
			}
			// remove all lines between line + 1 and last_line (inclusive).
			buffer_delete_lines(buffer, line_idx + 1, (u32)(last_line - line));

			u32 lines_removed = (u32)(last_line - line);
			buffer_shorten(buffer, buffer->nlines - lines_removed);
		}
	} else {
		// just delete characters from this line
		memmove(line->str + index, line->str + index + nchars, (size_t)(line->len - (nchars + index)) * sizeof(char32_t));
		line->len -= nchars;
	}

	buffer_remove_last_edit_if_empty(buffer);
	
	// cursor position could have been invalidated by this edit
	buffer_validate_cursor(buffer);

	buffer_lines_modified(buffer, line_idx, line_idx);
}

// Delete characters between the given buffer positions. Returns number of characters deleted.
i64 buffer_delete_chars_between(TextBuffer *buffer, BufferPos p1, BufferPos p2) {
	buffer_pos_validate(buffer, &p1);
	buffer_pos_validate(buffer, &p2);
	i64 nchars = buffer_pos_diff(buffer, p1, p2);
	if (nchars < 0) {
		// swap positions if p1 comes after p2
		nchars = -nchars;
		BufferPos tmp = p1;
		p1 = p2;
		p2 = tmp;
	}
	buffer_delete_chars_at_pos(buffer, p1, nchars);
	return nchars;
}

// Delete the current buffer selection. Returns the number of characters deleted.
i64 buffer_delete_selection(TextBuffer *buffer) {
	i64 ret = 0;
	if (buffer->selection) {
		ret = buffer_delete_chars_between(buffer, buffer->selection_pos, buffer->cursor_pos);
		buffer_cursor_move_to_pos(buffer, buffer_pos_min(buffer->selection_pos, buffer->cursor_pos)); // move cursor to whichever endpoint comes first
		buffer->selection = false;
	}
	return ret;
}

void buffer_insert_text_at_cursor(TextBuffer *buffer, String32 str) {
	buffer_delete_selection(buffer); // delete any selected text
	BufferPos endpos = buffer_insert_text_at_pos(buffer, buffer->cursor_pos, str);
	buffer_cursor_move_to_pos(buffer, endpos);
}

void buffer_insert_char_at_cursor(TextBuffer *buffer, char32_t c) {
	String32 s = {&c, 1};
	buffer_insert_text_at_cursor(buffer, s);
}

void buffer_insert_utf8_at_cursor(TextBuffer *buffer, char const *utf8) {
	String32 s32 = str32_from_utf8(utf8);
	if (s32.str) {
		buffer_insert_text_at_cursor(buffer, s32);
		str32_free(&s32);
	}
}

// insert newline at cursor and auto-indent
void buffer_newline(TextBuffer *buffer) {
	Settings const *settings = buffer_settings(buffer);
	BufferPos cursor_pos = buffer->cursor_pos;
	String32 line = buffer_get_line(buffer, cursor_pos.line);
	u32 whitespace_len;
	for (whitespace_len = 0; whitespace_len < line.len; ++whitespace_len) {
		if (line.str[whitespace_len] != ' ' && line.str[whitespace_len] != '\t')
			break; // found end of indentation
	}
	if (settings->auto_indent) {
		// newline + auto-indent
		char32_t *text = buffer_calloc(buffer, whitespace_len + 1, sizeof *text); // @OPTIMIZE: don't allocate on heap if whitespace_len is small
		if (text) {
			text[0] = '\n';
			memcpy(&text[1], line.str, whitespace_len * sizeof *text);
			buffer_insert_text_at_cursor(buffer, str32(text, whitespace_len + 1));
			free(text);
		}
	} else {
		// just newline
		buffer_insert_char_at_cursor(buffer, '\n');
	}
}

void buffer_delete_chars_at_cursor(TextBuffer *buffer, i64 nchars) {
	if (buffer->selection)
		buffer_delete_selection(buffer);
	else
		buffer_delete_chars_at_pos(buffer, buffer->cursor_pos, nchars);
}

i64 buffer_backspace_at_pos(TextBuffer *buffer, BufferPos *pos, i64 ntimes) {
	i64 n = buffer_pos_move_left(buffer, pos, ntimes);
	buffer_delete_chars_at_pos(buffer, *pos, n);
	return n;
}

// returns number of characters backspaced
i64 buffer_backspace_at_cursor(TextBuffer *buffer, i64 ntimes) {
	if (buffer->selection)
		return buffer_delete_selection(buffer);
	else
		return buffer_backspace_at_pos(buffer, &buffer->cursor_pos, ntimes);
}

void buffer_delete_words_at_pos(TextBuffer *buffer, BufferPos pos, i64 nwords) {
	BufferPos pos2 = pos;
	buffer_pos_move_right_words(buffer, &pos2, nwords);
	buffer_delete_chars_between(buffer, pos, pos2);
}

void buffer_delete_words_at_cursor(TextBuffer *buffer, i64 nwords) {
	if (buffer->selection)
		buffer_delete_selection(buffer);
	else
		buffer_delete_words_at_pos(buffer, buffer->cursor_pos, nwords);
}

void buffer_backspace_words_at_pos(TextBuffer *buffer, BufferPos *pos, i64 nwords) {
	BufferPos pos2 = *pos;
	buffer_pos_move_left_words(buffer, pos, nwords);
	buffer_delete_chars_between(buffer, pos2, *pos);
}

void buffer_backspace_words_at_cursor(TextBuffer *buffer, i64 nwords) {
	if (buffer->selection)
		buffer_delete_selection(buffer);
	else
		buffer_backspace_words_at_pos(buffer, &buffer->cursor_pos, nwords);
}

// puts the inverse edit into `inverse`
static Status buffer_undo_edit(TextBuffer *buffer, BufferEdit const *edit, BufferEdit *inverse) {
	bool success = false;
	bool prev_store_undo_events = buffer->store_undo_events;
	// temporarily disable saving of undo events so we don't add the inverse edit
	// to the undo history
	buffer->store_undo_events = false;

	// create inverse edit
	if (buffer_edit_create(buffer, inverse, edit->pos, edit->new_len, edit->prev_len)) {
		buffer_delete_chars_at_pos(buffer, edit->pos, (i64)edit->new_len);
		String32 str = {edit->prev_text, edit->prev_len};
		buffer_insert_text_at_pos(buffer, edit->pos, str);
		success = true;
	}

	buffer->store_undo_events = prev_store_undo_events;
	return success;
}

static void buffer_cursor_to_edit(TextBuffer *buffer, BufferEdit *edit) {
	buffer->selection = false;
	buffer_cursor_move_to_pos(buffer,
		buffer_pos_advance(buffer, edit->pos, edit->prev_len));
	buffer_center_cursor(buffer); // whenever we undo an edit, put the cursor in the center, to make it clear where the undo happened
}

// a <-b <-c
// c <-b <-a

void buffer_undo(TextBuffer *buffer, i64 ntimes) {
	bool chain_next = false;
	for (i64 i = 0; i < ntimes; ++i) {
		BufferEdit *edit = arr_lastp(buffer->undo_history);
		if (edit) {
			bool chain = edit->chain;
			BufferEdit inverse = {0};
			if (buffer_undo_edit(buffer, edit, &inverse)) {
				inverse.chain = chain_next;
				if (i == ntimes - 1) {
					// if we're on the last undo, put cursor where edit is
					buffer_cursor_to_edit(buffer, edit);
				}

				buffer_append_redo(buffer, &inverse);
				buffer_edit_free(edit);
				arr_remove_last(buffer->undo_history);
			}
			if (chain) --i;
			chain_next = chain;
		} else break;
	}
}

void buffer_redo(TextBuffer *buffer, i64 ntimes) {
	bool chain_next = false;
	for (i64 i = 0; i < ntimes; ++i) {
		BufferEdit *edit = arr_lastp(buffer->redo_history);
		if (edit) {
			bool chain = edit->chain;
			BufferEdit inverse = {0};
			if (buffer_undo_edit(buffer, edit, &inverse)) {
				inverse.chain = chain_next;
				if (i == ntimes - 1)
					buffer_cursor_to_edit(buffer, edit);
				
				// NOTE: we can't just use buffer_append_edit, because that clears the redo history
				arr_add(buffer->undo_history, inverse);
				if (!buffer->undo_history) buffer_out_of_mem(buffer);

				buffer_edit_free(edit);
				arr_remove_last(buffer->redo_history);
			}
			if (chain) --i;
			chain_next = chain;
		} else break;
	}
}

void buffer_copy_or_cut(TextBuffer *buffer, bool cut) {
	if (buffer->selection) {
		BufferPos pos1 = buffer_pos_min(buffer->selection_pos, buffer->cursor_pos);
		BufferPos pos2 = buffer_pos_max(buffer->selection_pos, buffer->cursor_pos);
		i64 selection_len = buffer_pos_diff(buffer, pos1, pos2);
		char *text = buffer_get_utf8_text_at_pos(buffer, pos1, (size_t)selection_len);
		if (text) {
			int err = SDL_SetClipboardText(text);
			free(text);
			if (err < 0) {
				buffer_seterr(buffer, "Couldn't get clipboard contents: %s", SDL_GetError());
			} else {
				// text copied successfully
				if (cut) {
					buffer_delete_selection(buffer);
				}
			}
		}
	}
}

void buffer_copy(TextBuffer *buffer) {
	buffer_copy_or_cut(buffer, false);
}

void buffer_cut(TextBuffer *buffer) {
	buffer_copy_or_cut(buffer, true);
}

void buffer_paste(TextBuffer *buffer) {
	if (SDL_HasClipboardText()) {
		char *text = SDL_GetClipboardText();
		if (text) {
			String32 str = str32_from_utf8(text);
			if (str.len) {
				buffer_insert_text_at_cursor(buffer, str);
				str32_free(&str);
			}
			SDL_free(text);
		}
	}
}


// if an error occurs, buffer is left untouched (except for the error field) and the function returns false.
Status buffer_load_file(TextBuffer *buffer, char const *filename) {
	FILE *fp = fopen(filename, "rb");
	bool success = true;
	if (fp) {
		fseek(fp, 0, SEEK_END);
		long file_pos = ftell(fp);
		size_t file_size = (size_t)file_pos;
		fseek(fp, 0, SEEK_SET);
		if (file_pos == -1 || file_pos == LONG_MAX) {
			buffer_seterr(buffer, "Couldn't get file position. There is something wrong with the file '%s'.", filename);
			success = false;
		} else if (file_size > 10L<<20) {
			buffer_seterr(buffer, "File too big (size: %zu).", file_size);
			success = false;
		} else {
			u8 *file_contents = buffer_calloc(buffer, 1, file_size);
			if (file_contents) {
				u32 lines_capacity = 4;
				Line *lines = buffer_calloc(buffer, lines_capacity, sizeof *buffer->lines); // initial lines
				if (lines) {
					u32 nlines = 1;
					size_t bytes_read = fread(file_contents, 1, file_size, fp);
					if (bytes_read == file_size) {
						char32_t c = 0;
						for (u8 *p = file_contents, *end = p + file_size; p != end; ) {
							if (*p == '\r' && p != end-1 && p[1] == '\n') {
								// CRLF line endings
								p += 2;
								c = '\n';
							} else {
								size_t n = unicode_utf8_to_utf32(&c, (char *)p, (size_t)(end - p));
								if (n == 0) {
									// null character
									c = 0;
									++p;
								} else if (n == (size_t)(-1)) {
									// invalid UTF-8
									success = false;
									buffer_seterr(buffer, "Invalid UTF-8 (position: %td).", p - file_contents);
									break;
								} else {
									p += n;
								}
							}
							if (c == '\n') {
								if (buffer_lines_set_min_capacity(buffer, &lines, &lines_capacity, nlines + 1))
									++nlines;
							} else {
								u32 line_idx = nlines - 1;
								Line *line = &lines[line_idx];
								buffer_line_append_char(buffer, line, c);
							}
						}
						if (success) {
							char *filename_copy = buffer_strdup(buffer, filename);
							if (!filename_copy) success = false;
							if (success) {
								// everything is good
								buffer_clear(buffer);
								buffer->lines = lines;
								buffer->nlines = nlines;
								buffer->frame_earliest_line_modified = 0;
								buffer->frame_latest_line_modified = nlines - 1;
								buffer->lines_capacity = lines_capacity;
								buffer->filename = filename_copy;
								buffer->last_write_time = time_last_modified(buffer->filename);
								if (!(fs_path_permission(filename) & FS_PERMISSION_WRITE)) {
									// can't write to this file; make the buffer view only.
									buffer->view_only = true;
								}
							}
						}
					} else {
						success = false;
					}
					if (!success) {
						// something went wrong; we need to free all the memory we used
						for (u32 i = 0; i < nlines; ++i)
							buffer_line_free(&lines[i]);
						free(lines);
					}
				}
				free(file_contents);
			}
			if (ferror(fp)) {	
				buffer_seterr(buffer, "Error reading from file.");
				success = false;
			}
		}
		if (fclose(fp) != 0) {
			buffer_seterr(buffer, "Error closing file.");
			success = false;
		}
	} else {
		buffer_seterr(buffer, "Couldn't open file %s: %s.", filename, strerror(errno));
		success = false;
	}
	return success;
}

// Reloads the file loaded in the buffer.
// Note that this clears undo history, etc.
void buffer_reload(TextBuffer *buffer) {
	if (buffer->filename && !buffer_is_untitled(buffer)) {
		BufferPos cursor_pos = buffer->cursor_pos;
		float x1 = buffer->x1, y1 = buffer->y1, x2 = buffer->x2, y2 = buffer->y2;
		double scroll_x = buffer->scroll_x; double scroll_y = buffer->scroll_y;
		if (buffer_load_file(buffer, buffer->filename)) {
			buffer->x1 = x1; buffer->y1 = y1; buffer->x2 = x2; buffer->y2 = y2;
			buffer->cursor_pos = cursor_pos;
			buffer->scroll_x = scroll_x;
			buffer->scroll_y = scroll_y;
			buffer_validate_cursor(buffer);
			buffer_correct_scroll(buffer);
		}
	}
}

// has this buffer been changed by another program since last save?
bool buffer_externally_changed(TextBuffer *buffer) {
	if (!buffer->filename || buffer_is_untitled(buffer))
		return false;
	return !timespec_eq(buffer->last_write_time, time_last_modified(buffer->filename));
}

void buffer_new_file(TextBuffer *buffer, char const *filename) {
	buffer_clear(buffer);

	buffer->filename = buffer_strdup(buffer, filename);
	buffer->lines_capacity = 4;
	buffer->lines = buffer_calloc(buffer, buffer->lines_capacity, sizeof *buffer->lines);
	buffer->nlines = 1;
}

// Save the buffer to its current filename. This will rewrite the entire file, regardless of
// whether there are any unsaved changes.
bool buffer_save(TextBuffer *buffer) {
	Settings const *settings = buffer_settings(buffer);
	if (!buffer->is_line_buffer && buffer->filename) {
		if (buffer->view_only) {
			buffer_seterr(buffer, "Can't save view-only file.");
			return false;
		}

		FILE *out = fopen(buffer->filename, "wb");
		if (out) {
			if (settings->auto_add_newline) {
				Line *last_line = &buffer->lines[buffer->nlines - 1];
				if (last_line->len) {
					// if the last line isn't empty, add a newline to the end of the file
					char32_t c = '\n';
					String32 s = {&c, 1};
					buffer_insert_text_at_pos(buffer, buffer_end_of_file(buffer), s);
				}
			}

			for (u32 i = 0; i < buffer->nlines; ++i) {
				Line *line = &buffer->lines[i];
				for (char32_t *p = line->str, *p_end = p + line->len; p != p_end; ++p) {
					char utf8[4] = {0};
					size_t bytes = unicode_utf32_to_utf8(utf8, *p);
					if (bytes != (size_t)-1) {
						if (fwrite(utf8, 1, bytes, out) != bytes) {
							buffer_seterr(buffer, "Couldn't write to %s.", buffer->filename);
						}
					}
				}

				if (i != buffer->nlines-1) {
					putc('\n', out);
				}
			}
			if (ferror(out)) {
				if (!buffer_haserr(buffer))
					buffer_seterr(buffer, "Couldn't write to %s.", buffer->filename);
			}
			if (fclose(out) != 0) {
				if (!buffer_haserr(buffer))
					buffer_seterr(buffer, "Couldn't close file %s.", buffer->filename);
			}
			buffer->last_write_time = time_last_modified(buffer->filename);
			bool success = !buffer_haserr(buffer);
			if (success)
				buffer->undo_history_write_pos = arr_len(buffer->undo_history);
			return success;
		} else {
			buffer_seterr(buffer, "Couldn't open file %s for writing: %s.", buffer->filename, strerror(errno));
			return false;
		}
	} else {
		// user tried to save line buffer. whatever
		return true;
	}
}

// save, but with a different file name
bool buffer_save_as(TextBuffer *buffer, char const *new_filename) {
	char *prev_filename = buffer->filename;
	if ((buffer->filename = buffer_strdup(buffer, new_filename))) {
		if (buffer_save(buffer)) {
			free(prev_filename);
			return true;
		} else {
			free(buffer->filename);
			buffer->filename = prev_filename;
			return false;
		}
	} else {
		return false;
	}
}

// for debugging
#if DEBUG
static void buffer_pos_check_valid(TextBuffer *buffer, BufferPos p) {
	assert(p.line < buffer->nlines);
	assert(p.index <= buffer->lines[p.line].len);
}

// perform a series of checks to make sure the buffer doesn't have any invalid values
void buffer_check_valid(TextBuffer *buffer) {
	assert(buffer->nlines);
	buffer_pos_check_valid(buffer, buffer->cursor_pos);
	if (buffer->selection) {
		buffer_pos_check_valid(buffer, buffer->selection_pos);
		// you shouldn't be able to select nothing
		assert(!buffer_pos_eq(buffer->cursor_pos, buffer->selection_pos));
	}
}
#else
void buffer_check_valid(TextBuffer *buffer) {
	(void)buffer;
}
#endif

u32 buffer_first_rendered_line(TextBuffer *buffer) {
	return (u32)buffer->scroll_y;
}

u32 buffer_last_rendered_line(TextBuffer *buffer) {
	u32 line = buffer_first_rendered_line(buffer) + (u32)buffer_display_lines(buffer) + 1;
	return clamp_u32(line, 0, buffer->nlines);
}

// Render the text buffer in the given rectangle
void buffer_render(TextBuffer *buffer, Rect r) {
	float x1, y1, x2, y2;
	rect_coords(r, &x1, &y1, &x2, &y2);
	// Correct the scroll, because the window size might have changed
	buffer_correct_scroll(buffer);

	Font *font = buffer_font(buffer);
	u32 nlines = buffer->nlines;
	Line *lines = buffer->lines;
	float char_width = text_font_char_width(font),
		char_height = text_font_char_height(font);

	Ted *ted = buffer->ted;
	Settings const *settings = buffer_settings(buffer);
	u32 const *colors = settings->colors;
	float const padding = settings->padding;
	float const border_thickness = settings->border_thickness;

	u32 start_line = buffer_first_rendered_line(buffer); // line to start rendering from
	Rect bounding_box = rect4(x1, y1, x2, y2);
	
	float render_start_y = y1 - (float)(buffer->scroll_y - start_line) * char_height; // where the 1st line is rendered

	// line numbering
	if (!buffer->is_line_buffer && settings->line_numbers) {
		float line_number_width = ndigits_u64(buffer->nlines) * char_width + padding;

		TextRenderState text_state = text_render_state_default;
		text_state.min_y = y1;
		text_state.max_y = y2;

		float y = render_start_y;
		u32 cursor_line = buffer->cursor_pos.line;
		for (u32 line = start_line; line < nlines; ++line) {
			char str[32] = {0};
			strbuf_printf(str, U32_FMT, line + 1); // convert line number to string
			float x = x1 + line_number_width - (float)strlen(str) * char_width; // right justify
			// set color
			rgba_u32_to_floats(colors[line == cursor_line ? COLOR_CURSOR_LINE_NUMBER : COLOR_LINE_NUMBERS],
				text_state.color);
			text_state.x = x; text_state.y = y;
			text_utf8_with_state(font, &text_state, str);
			y += char_height;
			if (y > y2) break;
		}

		x1 += line_number_width;
		x1 += 2; // a little bit of padding
		// line separating line numbers from text
		gl_geometry_rect(rect(V2(x1, y1), V2(border_thickness, y2 - y1)), colors[COLOR_LINE_NUMBERS_SEPARATOR]);
		x1 += border_thickness;
	}

	buffer->x1 = x1; buffer->y1 = y1; buffer->x2 = x2; buffer->y2 = y2;

	// get screen coordinates of cursor
	v2 cursor_display_pos = buffer_pos_to_pixels(buffer, buffer->cursor_pos);
	// the rectangle that the cursor is rendered as
	Rect cursor_rect = rect(cursor_display_pos, V2(settings->cursor_width, char_height));

	
	// highlight line cursor is on
	{
		Rect hl_rect = rect(V2(x1, cursor_display_pos.y), V2(x2-x1-1, char_height));
		buffer_clip_rect(buffer, &hl_rect);
		gl_geometry_rect(hl_rect, colors[COLOR_CURSOR_LINE_BG]);
	}

	u32 border_color = colors[COLOR_BORDER]; // color of border around buffer

	// bounding box around buffer
	gl_geometry_rect_border(bounding_box, border_thickness, border_color);
	
	// what x coordinate to start rendering the text from
	float render_start_x = x1 - (float)buffer->scroll_x * char_width;
	u32 column = 0;

	if (buffer->selection) { // draw selection
		BufferPos sel_start = {0}, sel_end = {0};
		int cmp = buffer_pos_cmp(buffer->cursor_pos, buffer->selection_pos);
		if (cmp < 0) {
			// cursor_pos comes first
			sel_start = buffer->cursor_pos;
			sel_end   = buffer->selection_pos;
		} else if (cmp > 0) {
			// selection_pos comes first
			sel_end   = buffer->cursor_pos;
			sel_start = buffer->selection_pos;
		} else assert(0);

		for (u32 line_idx = max_u32(sel_start.line, start_line); line_idx <= sel_end.line; ++line_idx) {
			Line *line = &buffer->lines[line_idx];
			u32 index1 = line_idx == sel_start.line ? sel_start.index : 0;
			u32 index2 = line_idx == sel_end.line ? sel_end.index : line->len;
			assert(index2 >= index1);

			// highlight everything from index1 to index2
			u32 n_columns_highlighted = buffer_index_to_column(buffer, line_idx, index2)
				- buffer_index_to_column(buffer, line_idx, index1);
			if (line_idx != sel_end.line) {
				++n_columns_highlighted; // highlight the newline (otherwise empty higlighted lines wouldn't be highlighted at all).
			}

			if (n_columns_highlighted) {
				BufferPos p1 = {.line = line_idx, .index = index1};
				v2 hl_p1 = buffer_pos_to_pixels(buffer, p1);
				Rect hl_rect = rect(
					hl_p1,
					V2((float)n_columns_highlighted * char_width, char_height)
				);
				buffer_clip_rect(buffer, &hl_rect);
				gl_geometry_rect(hl_rect, colors[buffer->view_only ? COLOR_VIEW_ONLY_SELECTION_BG : COLOR_SELECTION_BG]);
			}
			index1 = 0;
		}
	}
	gl_geometry_draw();

	Language language = buffer_language(buffer);
	// dynamic array of character types, to be filled by syntax_highlight
	SyntaxCharType *char_types = NULL;
	bool syntax_highlighting = language && settings->syntax_highlighting;

	if (buffer->frame_latest_line_modified >= buffer->frame_earliest_line_modified
		&& syntax_highlighting) {
		// update syntax cache
		Line *earliest = &buffer->lines[buffer->frame_earliest_line_modified];
		Line *latest = &buffer->lines[buffer->frame_latest_line_modified];
		Line *buffer_last_line = &buffer->lines[buffer->nlines - 1];
		Line *start = earliest == buffer->lines ? earliest : earliest - 1;

		for (Line *line = start; line != buffer_last_line; ++line) {
			SyntaxState syntax = line->syntax;
			syntax_highlight(&syntax, language, line->str, line->len, NULL);
			if (line > latest && line[1].syntax == syntax) {
				// no further necessary changes to the cache
				break;
			} else {
				line[1].syntax = syntax;
			}
		}
	}
	buffer->frame_earliest_line_modified = U32_MAX;
	buffer->frame_latest_line_modified = 0;


	TextRenderState text_state = text_render_state_default;
	text_state.x = render_start_x;
	text_state.y = render_start_y;
	text_state.min_x = x1;
	text_state.min_y = y1;
	text_state.max_x = x2;
	text_state.max_y = y2;
	if (!syntax_highlighting)
		rgba_u32_to_floats(colors[COLOR_TEXT], text_state.color);

	buffer->first_line_on_screen = start_line;
	for (u32 line_idx = start_line; line_idx < nlines; ++line_idx) {
		Line *line = &lines[line_idx];
		if (arr_len(char_types) < line->len) {
			arr_set_len(char_types, line->len);
		}
		if (syntax_highlighting) {
			SyntaxState syntax_state = line->syntax;
			syntax_highlight(&syntax_state, language, line->str, line->len, char_types);
		}
		for (u32 i = 0; i < line->len; ++i) {
			char32_t c = line->str[i];
			if (syntax_highlighting) {
				SyntaxCharType type = char_types[i];
				rgba_u32_to_floats(colors[syntax_char_type_to_color(type)], text_state.color);
			}
			switch (c) {
			case '\n': assert(0); break;
			case '\r': break; // for CRLF line endings
			case '\t': {
				uint tab_width = settings->tab_width;
				do {
					text_char_with_state(font, &text_state, ' ');
					++column;
				} while (column % tab_width);
			} break;
			default:
				text_char_with_state(font, &text_state, c);
				++column;
				break;
			}
		}

		// next line
		text_state.x = render_start_x;
		if (text_state.y > text_state.max_y) {
			buffer->last_line_on_screen = line_idx;
			// made it to the bottom of the buffer view.
			break;
		}
		text_state.y += text_font_char_height(font);
		column = 0;
	}
	
	arr_free(char_types);

	text_render(font);

	if (buffer == ted->active_buffer) {
		// render cursor
		float time_on = settings->cursor_blink_time_on;
		float time_off = settings->cursor_blink_time_off;
		bool is_on = true;
		if (time_off > 0) {
			double absolute_time = time_get_seconds();
			float period = time_on + time_off;
			// time in period
			double t = fmod(absolute_time, period);
			is_on = t < time_on; // are we in the "on" part of the period?
		}
		
		// highlight matching brackets
		char32_t cursor_bracket = buffer_char_before_cursor(buffer);
		char32_t matching_bracket = syntax_matching_bracket(language, cursor_bracket);
		if (cursor_bracket && matching_bracket) {
			int direction = syntax_is_opening_bracket(language, cursor_bracket) ? +1 : -1;
			int depth = 1;
			BufferPos pos = buffer->cursor_pos;
			buffer_pos_move_left(buffer, &pos, 1);
			while (pos.line >= start_line) {
				if (buffer_pos_move_right(buffer, &pos, direction)) {
					char32_t c = buffer_char_after_pos(buffer, pos);
					if (c == cursor_bracket) depth += 1;
					else if (c == matching_bracket) depth -= 1;
					if (depth == 0) break;
				} else {
					break;
				}
			}
			if (depth == 0) {
				// highlight it
				v2 gl_pos = buffer_pos_to_pixels(buffer, pos);
				Rect hl_rect = rect(gl_pos, V2(char_width, char_height));
				if (buffer_clip_rect(buffer, &hl_rect)) {
					gl_geometry_rect(hl_rect, colors[COLOR_MATCHING_BRACKET_HL]);
				}
			}
		}
		
		
		if (is_on) {
			if (buffer_clip_rect(buffer, &cursor_rect)) {
				// draw cursor
				gl_geometry_rect(cursor_rect, colors[buffer->view_only ? COLOR_VIEW_ONLY_CURSOR : COLOR_CURSOR]);
			}
		}
		gl_geometry_draw();
	}
}

// if you do:
//  buffer_start_edit_chain(buffer)
//  buffer_insert_text_at_pos(buffer, some position, "text1")
//  buffer_insert_text_at_pos(buffer, another position, "text2")
//  buffer_end_edit_chain(buffer)
// pressing ctrl+z will undo both the insertion of text1 and text2.
void buffer_start_edit_chain(TextBuffer *buffer) {
	assert(!buffer->chaining_edits);
	assert(!buffer->will_chain_edits);
	buffer->will_chain_edits = true;
}

void buffer_end_edit_chain(TextBuffer *buffer) {
	buffer->chaining_edits = buffer->will_chain_edits = false;
}

void buffer_indent_lines(TextBuffer *buffer, u32 first_line, u32 last_line) {
	assert(first_line <= last_line);
	buffer_start_edit_chain(buffer);
	for (u32 i = first_line; i <= last_line; ++i) {
		BufferPos pos = {.line = i, .index = 0};
		char32_t c = '\t';
		buffer_insert_text_at_pos(buffer, pos, str32(&c, 1));
	}
	buffer_end_edit_chain(buffer);
}

void buffer_dedent_lines(TextBuffer *buffer, u32 first_line, u32 last_line) {
	assert(first_line <= last_line);
	buffer_start_edit_chain(buffer);
	Settings const *settings = buffer_settings(buffer);
	u8 const tab_width = settings->tab_width;
	
	for (u32 line_idx = first_line; line_idx <= last_line; ++line_idx) {
		Line *line = &buffer->lines[line_idx];
		if (line->len) {
			u32 chars_to_delete = 0;
			if (line->str[0] == '\t') {
				chars_to_delete = 1;
			} else {
				u32 i;
				for (i = 0; i < line->len && i < tab_width; ++i) {
					char32_t c = line->str[i];
					if (c == '\t' || !is32_space(c))
						break;
				}
				chars_to_delete = i;
			}
			if (chars_to_delete) {
				BufferPos pos = {.line = line_idx, .index = 0};
				buffer_delete_chars_at_pos(buffer, pos, chars_to_delete);
			}
		}
	}
	buffer_end_edit_chain(buffer);
}

void buffer_indent_selection(TextBuffer *buffer) {
	if (!buffer->selection) return;
	u32 l1 = buffer->cursor_pos.line;
	u32 l2 = buffer->selection_pos.line;
	sort2_u32(&l1, &l2); // ensure l1 <= l2
	buffer_indent_lines(buffer, l1, l2);
}

void buffer_dedent_selection(TextBuffer *buffer) {
	if (!buffer->selection) return;
	u32 l1 = buffer->cursor_pos.line;
	u32 l2 = buffer->selection_pos.line;
	sort2_u32(&l1, &l2); // ensure l1 <= l2
	buffer_dedent_lines(buffer, l1, l2);
}