summaryrefslogtreecommitdiff
path: root/src/rail_cmd.cpp
blob: 1292a65230e5f4a9b6194e5380563d0fcd52ed77 (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
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
/* $Id$ */

/** @file rail_cmd.cpp */

#include "stdafx.h"
#include "openttd.h"
#include "bridge_map.h"
#include "bridge.h"
#include "cmd_helper.h"
#include "debug.h"
#include "tile_cmd.h"
#include "rail_map.h"
#include "road_map.h"
#include "landscape.h"
#include "town_map.h"
#include "tunnel_map.h"
#include "viewport_func.h"
#include "command_func.h"
#include "pathfind.h"
#include "engine.h"
#include "town.h"
#include "station.h"
#include "sprite.h"
#include "depot.h"
#include "waypoint.h"
#include "rail.h"
#include "newgrf.h"
#include "yapf/yapf.h"
#include "newgrf_engine.h"
#include "newgrf_callbacks.h"
#include "newgrf_station.h"
#include "train.h"
#include "misc/autoptr.hpp"
#include "variables.h"
#include "autoslope.h"
#include "transparency.h"
#include "water.h"
#include "tunnelbridge_map.h"
#include "window_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "signal_func.h"
#include "tunnelbridge.h"

#include "table/sprites.h"
#include "table/strings.h"
#include "table/railtypes.h"
#include "table/track_land.h"

const byte _track_sloped_sprites[14] = {
	14, 15, 22, 13,
	 0, 21, 17, 12,
	23,  0, 18, 20,
	19, 16
};


/*         4
 *     ---------
 *    |\       /|
 *    | \    1/ |
 *    |  \   /  |
 *    |   \ /   |
 *  16|    \    |32
 *    |   / \2  |
 *    |  /   \  |
 *    | /     \ |
 *    |/       \|
 *     ---------
 *         8
 */



/* MAP2 byte:    abcd???? => Signal On? Same coding as map3lo
 * MAP3LO byte:  abcd???? => Signal Exists?
 *               a and b are for diagonals, upper and left,
 *               one for each direction. (ie a == NE->SW, b ==
 *               SW->NE, or v.v., I don't know. b and c are
 *               similar for lower and right.
 * MAP2 byte:    ????abcd => Type of ground.
 * MAP3LO byte:  ????abcd => Type of rail.
 * MAP5:         00abcdef => rail
 *               01abcdef => rail w/ signals
 *               10uuuuuu => unused
 *               11uuuudd => rail depot
 */


void *EnsureNoTrainOnTrackProc(Vehicle *v, void *data)
{
	TrackBits rail_bits = *(TrackBits *)data;

	if (v->type != VEH_TRAIN) return NULL;

	if ((v->u.rail.track != rail_bits) && !TracksOverlap(v->u.rail.track | rail_bits)) return NULL;

	_error_message = VehicleInTheWayErrMsg(v);
	return v;
}

/**
 * Tests if a vehicle interacts with the specified track.
 * All track bits interact except parallel TRACK_BIT_HORZ or TRACK_BIT_VERT.
 *
 * @param tile The tile.
 * @param track The track.
 */
static bool EnsureNoTrainOnTrack(TileIndex tile, Track track)
{
	TrackBits rail_bits = TrackToTrackBits(track);

	return VehicleFromPos(tile, &rail_bits, &EnsureNoTrainOnTrackProc) == NULL;
}

static bool CheckTrackCombination(TileIndex tile, TrackBits to_build, uint flags)
{
	TrackBits current; // The current track layout
	TrackBits future;  // The track layout we want to build
	_error_message = STR_1001_IMPOSSIBLE_TRACK_COMBINATION;

	if (!IsPlainRailTile(tile)) return false;

	/* So, we have a tile with tracks on it (and possibly signals). Let's see
	 * what tracks first */
	current = GetTrackBits(tile);
	future = current | to_build;

	/* Are we really building something new? */
	if (current == future) {
		/* Nothing new is being built */
		_error_message = STR_1007_ALREADY_BUILT;
		return false;
	}

	/* Let's see if we may build this */
	if (flags & DC_NO_RAIL_OVERLAP || HasSignals(tile)) {
		/* If we are not allowed to overlap (flag is on for ai players or we have
		 * signals on the tile), check that */
		return future == TRACK_BIT_HORZ || future == TRACK_BIT_VERT;
	} else {
		/* Normally, we may overlap and any combination is valid */
		return true;
	}
}


/** Valid TrackBits on a specific (non-steep)-slope without foundation */
static const TrackBits _valid_tracks_without_foundation[15] = {
	TRACK_BIT_ALL,
	TRACK_BIT_RIGHT,
	TRACK_BIT_UPPER,
	TRACK_BIT_X,

	TRACK_BIT_LEFT,
	TRACK_BIT_NONE,
	TRACK_BIT_Y,
	TRACK_BIT_LOWER,

	TRACK_BIT_LOWER,
	TRACK_BIT_Y,
	TRACK_BIT_NONE,
	TRACK_BIT_LEFT,

	TRACK_BIT_X,
	TRACK_BIT_UPPER,
	TRACK_BIT_RIGHT,
};

/** Valid TrackBits on a specific (non-steep)-slope with leveled foundation */
static const TrackBits _valid_tracks_on_leveled_foundation[15] = {
	TRACK_BIT_NONE,
	TRACK_BIT_LEFT,
	TRACK_BIT_LOWER,
	TRACK_BIT_Y | TRACK_BIT_LOWER | TRACK_BIT_LEFT,

	TRACK_BIT_RIGHT,
	TRACK_BIT_ALL,
	TRACK_BIT_X | TRACK_BIT_LOWER | TRACK_BIT_RIGHT,
	TRACK_BIT_ALL,

	TRACK_BIT_UPPER,
	TRACK_BIT_X | TRACK_BIT_UPPER | TRACK_BIT_LEFT,
	TRACK_BIT_ALL,
	TRACK_BIT_ALL,

	TRACK_BIT_Y | TRACK_BIT_UPPER | TRACK_BIT_RIGHT,
	TRACK_BIT_ALL,
	TRACK_BIT_ALL
};

/**
 * Checks if a track combination is valid on a specific slope and returns the needed foundation.
 *
 * @param tileh Tile slope.
 * @param bits  Trackbits.
 * @return Needed foundation or FOUNDATION_INVALID if track/slope combination is not allowed.
 */
Foundation GetRailFoundation(Slope tileh, TrackBits bits)
{
	if (bits == TRACK_BIT_NONE) return FOUNDATION_NONE;

	if (IsSteepSlope(tileh)) {
		/* Test for inclined foundations */
		if (bits == TRACK_BIT_X) return FOUNDATION_INCLINED_X;
		if (bits == TRACK_BIT_Y) return FOUNDATION_INCLINED_Y;

		/* Get higher track */
		Corner highest_corner = GetHighestSlopeCorner(tileh);
		TrackBits higher_track = CornerToTrackBits(highest_corner);

		/* Only higher track? */
		if (bits == higher_track) return HalftileFoundation(highest_corner);

		/* Overlap with higher track? */
		if (TracksOverlap(bits | higher_track)) return FOUNDATION_INVALID;

		/* either lower track or both higher and lower track */
		return ((bits & higher_track) != 0 ? FOUNDATION_STEEP_BOTH : FOUNDATION_STEEP_LOWER);
	} else {
		if ((~_valid_tracks_without_foundation[tileh] & bits) == 0) return FOUNDATION_NONE;

		bool valid_on_leveled = ((~_valid_tracks_on_leveled_foundation[tileh] & bits) == 0);

		Corner track_corner;
		switch (bits) {
			case TRACK_BIT_LEFT:  track_corner = CORNER_W; break;
			case TRACK_BIT_LOWER: track_corner = CORNER_S; break;
			case TRACK_BIT_RIGHT: track_corner = CORNER_E; break;
			case TRACK_BIT_UPPER: track_corner = CORNER_N; break;

			case TRACK_BIT_HORZ:
				if (tileh == SLOPE_N) return HalftileFoundation(CORNER_N);
				if (tileh == SLOPE_S) return HalftileFoundation(CORNER_S);
				return (valid_on_leveled ? FOUNDATION_LEVELED : FOUNDATION_INVALID);

			case TRACK_BIT_VERT:
				if (tileh == SLOPE_W) return HalftileFoundation(CORNER_W);
				if (tileh == SLOPE_E) return HalftileFoundation(CORNER_E);
				return (valid_on_leveled ? FOUNDATION_LEVELED : FOUNDATION_INVALID);

			case TRACK_BIT_X:
				if (IsSlopeWithOneCornerRaised(tileh)) return FOUNDATION_INCLINED_X;
				return (valid_on_leveled ? FOUNDATION_LEVELED : FOUNDATION_INVALID);

			case TRACK_BIT_Y:
				if (IsSlopeWithOneCornerRaised(tileh)) return FOUNDATION_INCLINED_Y;
				return (valid_on_leveled ? FOUNDATION_LEVELED : FOUNDATION_INVALID);

			default:
				return (valid_on_leveled ? FOUNDATION_LEVELED : FOUNDATION_INVALID);
		}
		/* Single diagonal track */

		/* Track must be at least valid on leveled foundation */
		if (!valid_on_leveled) return FOUNDATION_INVALID;

		/* If slope has three raised corners, build leveled foundation */
		if (IsSlopeWithThreeCornersRaised(tileh)) return FOUNDATION_LEVELED;

		/* If neighboured corners of track_corner are lowered, build halftile foundation */
		if ((tileh & SlopeWithThreeCornersRaised(OppositeCorner(track_corner))) == SlopeWithOneCornerRaised(track_corner)) return HalftileFoundation(track_corner);

		/* else special anti-zig-zag foundation */
		return SpecialRailFoundation(track_corner);
	}
}


/**
 * Tests if a track can be build on a tile.
 *
 * @param tileh Tile slope.
 * @param rail_bits Tracks to build.
 * @param existing Tracks already built.
 * @param tile Tile (used for water test)
 * @return Error message or cost for foundation building.
 */
static CommandCost CheckRailSlope(Slope tileh, TrackBits rail_bits, TrackBits existing, TileIndex tile)
{
	/* don't allow building on the lower side of a coast */
	if (IsTileType(tile, MP_WATER) || (IsTileType(tile, MP_RAILWAY) && (GetRailGroundType(tile) == RAIL_GROUND_WATER))) {
		if (!IsSteepSlope(tileh) && ((~_valid_tracks_on_leveled_foundation[tileh] & (rail_bits | existing)) != 0)) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
	}

	Foundation f_new = GetRailFoundation(tileh, rail_bits | existing);

	/* check track/slope combination */
	if ((f_new == FOUNDATION_INVALID) ||
	    ((f_new != FOUNDATION_NONE) && (!_patches.build_on_slopes || _is_old_ai_player))
	   ) return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);

	Foundation f_old = GetRailFoundation(tileh, existing);
	return CommandCost(EXPENSES_CONSTRUCTION, f_new != f_old ? _price.terraform : (Money)0);
}

/* Validate functions for rail building */
static inline bool ValParamTrackOrientation(Track track) {return IsValidTrack(track);}

/** Build a single piece of rail
 * @param tile tile  to build on
 * @param flags operation to perform
 * @param p1 railtype of being built piece (normal, mono, maglev)
 * @param p2 rail track to build
 */
CommandCost CmdBuildSingleRail(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	Slope tileh;
	RailType railtype = (RailType)p1;
	Track track = (Track)p2;
	TrackBits trackbit;
	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost ret;

	if (!ValParamRailtype(railtype) || !ValParamTrackOrientation(track)) return CMD_ERROR;

	tileh = GetTileSlope(tile, NULL);
	trackbit = TrackToTrackBits(track);

	switch (GetTileType(tile)) {
		case MP_RAILWAY:
			if (!CheckTrackCombination(tile, trackbit, flags) ||
					!EnsureNoTrainOnTrack(tile, track)) {
				return CMD_ERROR;
			}
			if (!IsTileOwner(tile, _current_player) ||
					!IsCompatibleRail(GetRailType(tile), railtype)) {
				/* Get detailed error message */
				return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
			}

			ret = CheckRailSlope(tileh, trackbit, GetTrackBits(tile), tile);
			if (CmdFailed(ret)) return ret;
			cost.AddCost(ret);

			/* If the rail types don't match, try to convert only if engines of
			 * the present rail type are powered on the new rail type. */
			if (GetRailType(tile) != railtype && HasPowerOnRail(GetRailType(tile), railtype)) {
				ret = DoCommand(tile, tile, railtype, flags, CMD_CONVERT_RAIL);
				if (CmdFailed(ret)) return ret;
				cost.AddCost(ret);
			}

			if (flags & DC_EXEC) {
				SetRailGroundType(tile, RAIL_GROUND_BARREN);
				SetTrackBits(tile, GetTrackBits(tile) | trackbit);
			}
			break;

		case MP_ROAD:
#define M(x) (1 << (x))
			/* Level crossings may only be built on these slopes */
			if (!HasBit(M(SLOPE_SEN) | M(SLOPE_ENW) | M(SLOPE_NWS) | M(SLOPE_NS) | M(SLOPE_WSE) | M(SLOPE_EW) | M(SLOPE_FLAT), tileh)) {
				return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
			}
#undef M

			if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;

			if (IsNormalRoad(tile)) {
				if (HasRoadWorks(tile)) return_cmd_error(STR_ROAD_WORKS_IN_PROGRESS);

				if (GetDisallowedRoadDirections(tile) != DRD_NONE) return_cmd_error(STR_ERR_CROSSING_ON_ONEWAY_ROAD);

				RoadTypes roadtypes = GetRoadTypes(tile);
				RoadBits road = GetRoadBits(tile, ROADTYPE_ROAD);
				RoadBits tram = GetRoadBits(tile, ROADTYPE_TRAM);
				switch (roadtypes) {
					default: break;
					case ROADTYPES_TRAM:
						/* Tram crossings must always have road. */
						if (flags & DC_EXEC) SetRoadOwner(tile, ROADTYPE_ROAD, _current_player);
						roadtypes |= ROADTYPES_ROAD;
						break;

					case ROADTYPES_ROADTRAM: if (road == tram) break;
						/* FALL THROUGH */
					case ROADTYPES_ROADHWAY: // Road and highway are incompatible in this case
					case ROADTYPES_TRAMHWAY: // Tram and highway are incompatible in this case
					case ROADTYPES_ALL:      // Also incompatible
						return CMD_ERROR;
				}

				road |= tram | GetRoadBits(tile, ROADTYPE_HWAY);

				if ((track == TRACK_X && road == ROAD_Y) ||
						(track == TRACK_Y && road == ROAD_X)) {
					if (flags & DC_EXEC) {
						MakeRoadCrossing(tile, GetRoadOwner(tile, ROADTYPE_ROAD), GetRoadOwner(tile, ROADTYPE_TRAM), GetRoadOwner(tile, ROADTYPE_HWAY), _current_player, (track == TRACK_X ? AXIS_Y : AXIS_X), railtype, roadtypes, GetTownIndex(tile));
						UpdateLevelCrossing(tile, false);
					}
					break;
				}
			}

			if (IsLevelCrossing(tile) && GetCrossingRailBits(tile) == trackbit) {
				return_cmd_error(STR_1007_ALREADY_BUILT);
			}
			/* FALLTHROUGH */

		default:
			/* Will there be flat water on the lower halftile? */
			bool water_ground = IsTileType(tile, MP_WATER) && IsSlopeWithOneCornerRaised(tileh);

			ret = CheckRailSlope(tileh, trackbit, TRACK_BIT_NONE, tile);
			if (CmdFailed(ret)) return ret;
			cost.AddCost(ret);

			ret = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
			if (CmdFailed(ret)) return ret;
			cost.AddCost(ret);

			if (water_ground) {
				cost.AddCost(-_price.clear_water);
				cost.AddCost(_price.clear_roughland);
			}

			if (flags & DC_EXEC) {
				MakeRailNormal(tile, _current_player, trackbit, railtype);
				if (water_ground) SetRailGroundType(tile, RAIL_GROUND_WATER);
			}
			break;
	}

	if (flags & DC_EXEC) {
		MarkTileDirtyByTile(tile);
		AddTrackToSignalBuffer(tile, track, _current_player);
		YapfNotifyTrackLayoutChange(tile, track);
	}

	return cost.AddCost(RailBuildCost(railtype));
}

/** Remove a single piece of track
 * @param tile tile to remove track from
 * @param flags operation to perform
 * @param p1 unused
 * @param p2 rail orientation
 */
CommandCost CmdRemoveSingleRail(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	Track track = (Track)p2;
	TrackBits trackbit;
	CommandCost cost(EXPENSES_CONSTRUCTION, _price.remove_rail );
	bool crossing = false;

	if (!ValParamTrackOrientation((Track)p2)) return CMD_ERROR;
	trackbit = TrackToTrackBits(track);

	/* Need to read tile owner now because it may change when the rail is removed
	 * Also, in case of floods, _current_player != owner
	 * There may be invalid tiletype even in exec run (when removing long track),
	 * so do not call GetTileOwner(tile) in any case here */
	Owner owner = INVALID_OWNER;

	switch (GetTileType(tile)) {
		case MP_ROAD: {
			if (!IsLevelCrossing(tile) ||
					GetCrossingRailBits(tile) != trackbit ||
					(_current_player != OWNER_WATER && !CheckTileOwnership(tile)) ||
					(!(flags & DC_BANKRUPT) && !EnsureNoVehicleOnGround(tile))) {
				return CMD_ERROR;
			}

			if (flags & DC_EXEC) {
				owner = GetTileOwner(tile);
				MakeRoadNormal(tile, GetCrossingRoadBits(tile), GetRoadTypes(tile), GetTownIndex(tile), GetRoadOwner(tile, ROADTYPE_ROAD), GetRoadOwner(tile, ROADTYPE_TRAM), GetRoadOwner(tile, ROADTYPE_HWAY));
			}
			break;
		}

		case MP_RAILWAY: {
			TrackBits present;

			if (!IsPlainRailTile(tile) ||
					(_current_player != OWNER_WATER && !CheckTileOwnership(tile)) ||
					!EnsureNoTrainOnTrack(tile, track)) {
				return CMD_ERROR;
			}

			present = GetTrackBits(tile);
			if ((present & trackbit) == 0) return CMD_ERROR;
			if (present == (TRACK_BIT_X | TRACK_BIT_Y)) crossing = true;

			/* Charge extra to remove signals on the track, if they are there */
			if (HasSignalOnTrack(tile, track))
				cost.AddCost(DoCommand(tile, track, 0, flags, CMD_REMOVE_SIGNALS));

			if (flags & DC_EXEC) {
				owner = GetTileOwner(tile);
				present ^= trackbit;
				if (present == 0) {
					Slope tileh = GetTileSlope(tile, NULL);
					/* If there is flat water on the lower halftile, convert the tile to shore so the water remains */
					if (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh)) {
						MakeShore(tile);
					} else {
						DoClearSquare(tile);
					}
				} else {
					SetTrackBits(tile, present);
				}
			}
			break;
		}

		default: return CMD_ERROR;
	}

	if (flags & DC_EXEC) {
		/* if we got that far, 'owner' variable is set correctly */
		assert(IsValidPlayer(owner));

		MarkTileDirtyByTile(tile);
		if (crossing) {
			/* crossing is set when only TRACK_BIT_X and TRACK_BIT_Y are set. As we
			 * are removing one of these pieces, we'll need to update signals for
			 * both directions explicitly, as after the track is removed it won't
			 * 'connect' with the other piece. */
			AddTrackToSignalBuffer(tile, TRACK_X, owner);
			AddTrackToSignalBuffer(tile, TRACK_Y, owner);
			YapfNotifyTrackLayoutChange(tile, TRACK_X);
			YapfNotifyTrackLayoutChange(tile, TRACK_Y);
		} else {
			AddTrackToSignalBuffer(tile, track, owner);
			YapfNotifyTrackLayoutChange(tile, track);
		}
	}

	return cost;
}


/**
 * Called from water_cmd if a non-flat rail-tile gets flooded and should be converted to shore.
 * The function floods the lower halftile, if the tile has a halftile foundation.
 *
 * @param t The tile to flood.
 * @return true if something was flooded.
 */
bool FloodHalftile(TileIndex t)
{
	bool flooded = false;
	if (GetRailGroundType(t) == RAIL_GROUND_WATER) return flooded;

	Slope tileh = GetTileSlope(t, NULL);
	TrackBits rail_bits = GetTrackBits(t);

	if (IsSlopeWithOneCornerRaised(tileh)) {
		TrackBits lower_track = CornerToTrackBits(OppositeCorner(GetHighestSlopeCorner(tileh)));

		TrackBits to_remove = lower_track & rail_bits;
		if (to_remove != 0) {
			_current_player = OWNER_WATER;
			if (CmdFailed(DoCommand(t, 0, FIND_FIRST_BIT(to_remove), DC_EXEC, CMD_REMOVE_SINGLE_RAIL))) return flooded; // not yet floodable
			flooded = true;
			rail_bits = rail_bits & ~to_remove;
			if (rail_bits == 0) {
				MakeShore(t);
				MarkTileDirtyByTile(t);
				return flooded;
			}
		}

		if (IsNonContinuousFoundation(GetRailFoundation(tileh, rail_bits))) {
			flooded = true;
			SetRailGroundType(t, RAIL_GROUND_WATER);
			MarkTileDirtyByTile(t);
		}
	} else {
		/* Make shore on steep slopes and 'three-corners-raised'-slopes. */
		if (ApplyFoundationToSlope(GetRailFoundation(tileh, rail_bits), &tileh) == 0) {
			if (IsSteepSlope(tileh) || IsSlopeWithThreeCornersRaised(tileh)) {
				flooded = true;
				SetRailGroundType(t, RAIL_GROUND_WATER);
				MarkTileDirtyByTile(t);
			}
		}
	}
	return flooded;
}

static const TileIndexDiffC _trackdelta[] = {
	{ -1,  0 }, {  0,  1 }, { -1,  0 }, {  0,  1 }, {  1,  0 }, {  0,  1 },
	{  0,  0 },
	{  0,  0 },
	{  1,  0 }, {  0, -1 }, {  0, -1 }, {  1,  0 }, {  0, -1 }, { -1,  0 },
	{  0,  0 },
	{  0,  0 }
};


static CommandCost ValidateAutoDrag(Trackdir *trackdir, TileIndex start, TileIndex end)
{
	int x = TileX(start);
	int y = TileY(start);
	int ex = TileX(end);
	int ey = TileY(end);
	int dx, dy, trdx, trdy;

	if (!ValParamTrackOrientation(TrackdirToTrack(*trackdir))) return CMD_ERROR;

	/* calculate delta x,y from start to end tile */
	dx = ex - x;
	dy = ey - y;

	/* calculate delta x,y for the first direction */
	trdx = _trackdelta[*trackdir].x;
	trdy = _trackdelta[*trackdir].y;

	if (!IsDiagonalTrackdir(*trackdir)) {
		trdx += _trackdelta[*trackdir ^ 1].x;
		trdy += _trackdelta[*trackdir ^ 1].y;
	}

	/* validate the direction */
	while (
		(trdx <= 0 && dx > 0) ||
		(trdx >= 0 && dx < 0) ||
		(trdy <= 0 && dy > 0) ||
		(trdy >= 0 && dy < 0)
	) {
		if (!HasBit(*trackdir, 3)) { // first direction is invalid, try the other
			SetBit(*trackdir, 3); // reverse the direction
			trdx = -trdx;
			trdy = -trdy;
		} else { // other direction is invalid too, invalid drag
			return CMD_ERROR;
		}
	}

	/* (for diagonal tracks, this is already made sure of by above test), but:
	 * for non-diagonal tracks, check if the start and end tile are on 1 line */
	if (!IsDiagonalTrackdir(*trackdir)) {
		trdx = _trackdelta[*trackdir].x;
		trdy = _trackdelta[*trackdir].y;
		if (abs(dx) != abs(dy) && abs(dx) + abs(trdy) != abs(dy) + abs(trdx))
			return CMD_ERROR;
	}

	return CommandCost();
}

/** Build a stretch of railroad tracks.
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1 end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0-3) - railroad type normal/maglev (0 = normal, 1 = mono, 2 = maglev)
 * - p2 = (bit 4-6) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit 7)   - 0 = build, 1 = remove tracks
 */
static CommandCost CmdRailTrackHelper(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	CommandCost ret, total_cost(EXPENSES_CONSTRUCTION);
	Track track = (Track)GB(p2, 4, 3);
	Trackdir trackdir;
	byte mode = HasBit(p2, 7);
	RailType railtype = (RailType)GB(p2, 0, 4);
	TileIndex end_tile;

	if (!ValParamRailtype(railtype) || !ValParamTrackOrientation(track)) return CMD_ERROR;
	if (p1 >= MapSize()) return CMD_ERROR;
	end_tile = p1;
	trackdir = TrackToTrackdir(track);

	if (CmdFailed(ValidateAutoDrag(&trackdir, tile, end_tile))) return CMD_ERROR;

	if (flags & DC_EXEC) SndPlayTileFx(SND_20_SPLAT_2, tile);

	for (;;) {
		ret = DoCommand(tile, railtype, TrackdirToTrack(trackdir), flags, (mode == 0) ? CMD_BUILD_SINGLE_RAIL : CMD_REMOVE_SINGLE_RAIL);

		if (CmdFailed(ret)) {
			if ((_error_message != STR_1007_ALREADY_BUILT) && (mode == 0)) break;
			_error_message = INVALID_STRING_ID;
		} else {
			total_cost.AddCost(ret);
		}

		if (tile == end_tile) break;

		tile += ToTileIndexDiff(_trackdelta[trackdir]);

		/* toggle railbit for the non-diagonal tracks */
		if (!IsDiagonalTrackdir(trackdir)) ToggleBit(trackdir, 0);
	}

	return (total_cost.GetCost() == 0) ? CMD_ERROR : total_cost;
}

/** Build rail on a stretch of track.
 * Stub for the unified rail builder/remover
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1 end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0-3) - railroad type normal/maglev (0 = normal, 1 = mono, 2 = maglev)
 * - p2 = (bit 4-6) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit 7)   - 0 = build, 1 = remove tracks
 * @see CmdRailTrackHelper
 */
CommandCost CmdBuildRailroadTrack(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	return CmdRailTrackHelper(tile, flags, p1, ClrBit(p2, 7));
}

/** Build rail on a stretch of track.
 * Stub for the unified rail builder/remover
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1 end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit 0-3) - railroad type normal/maglev (0 = normal, 1 = mono, 2 = maglev)
 * - p2 = (bit 4-6) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit 7)   - 0 = build, 1 = remove tracks
 * @see CmdRailTrackHelper
 */
CommandCost CmdRemoveRailroadTrack(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	return CmdRailTrackHelper(tile, flags, p1, SetBit(p2, 7));
}

/** Build a train depot
 * @param tile position of the train depot
 * @param flags operation to perform
 * @param p1 rail type
 * @param p2 bit 0..1 entrance direction (DiagDirection)
 *
 * @todo When checking for the tile slope,
 * distingush between "Flat land required" and "land sloped in wrong direction"
 */
CommandCost CmdBuildTrainDepot(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	Slope tileh;

	/* check railtype and valid direction for depot (0 through 3), 4 in total */
	if (!ValParamRailtype((RailType)p1)) return CMD_ERROR;

	tileh = GetTileSlope(tile, NULL);

	DiagDirection dir = Extract<DiagDirection, 0>(p2);

	/* Prohibit construction if
	 * The tile is non-flat AND
	 * 1) The AI is "old-school"
	 * 2) build-on-slopes is disabled
	 * 3) the tile is steep i.e. spans two height levels
	 * 4) the exit points in the wrong direction
	 */

	if (tileh != SLOPE_FLAT && (
				_is_old_ai_player ||
				!_patches.build_on_slopes ||
				IsSteepSlope(tileh) ||
				!CanBuildDepotByTileh(dir, tileh)
			)) {
		return_cmd_error(STR_0007_FLAT_LAND_REQUIRED);
	}

	CommandCost cost = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
	if (CmdFailed(cost)) return CMD_ERROR;

	if (MayHaveBridgeAbove(tile) && IsBridgeAbove(tile)) return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);

	Depot *d = new Depot(tile);

	if (d == NULL) return CMD_ERROR;
	AutoPtrT<Depot> d_auto_delete = d;

	if (flags & DC_EXEC) {
		MakeRailDepot(tile, _current_player, dir, (RailType)p1);
		MarkTileDirtyByTile(tile);

		d->town_index = ClosestTownFromTile(tile, (uint)-1)->index;

		AddSideToSignalBuffer(tile, INVALID_DIAGDIR, _current_player);
		YapfNotifyTrackLayoutChange(tile, TrackdirToTrack(DiagdirToDiagTrackdir(dir)));
		d_auto_delete.Detach();
	}

	return cost.AddCost(_price.build_train_depot);
}

/** Build signals, alternate between double/single, signal/semaphore,
 * pre/exit/combo-signals, and what-else not. If the rail piece does not
 * have any signals, bit 4 (cycle signal-type) is ignored
 * @param tile tile where to build the signals
 * @param flags operation to perform
 * @param p1 various bitstuffed elements
 * - p1 = (bit 0-2) - track-orientation, valid values: 0-5 (Track enum)
 * - p1 = (bit 3)   - 1 = override signal/semaphore, or pre/exit/combo signal or (for bit 7) toggle variant (CTRL-toggle)
 * - p1 = (bit 4)   - 0 = signals, 1 = semaphores
 * - p1 = (bit 5-6) - type of the signal, for valid values see enum SignalType in rail_map.h
 * - p1 = (bit 7)   - convert the present signal type and variant
 * @param p2 used for CmdBuildManySignals() to copy direction of first signal
 * TODO: p2 should be replaced by two bits for "along" and "against" the track.
 */
CommandCost CmdBuildSingleSignal(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	Track track = (Track)GB(p1, 0, 3);
	bool ctrl_pressed = HasBit(p1, 3); // was the CTRL button pressed
	SignalVariant sigvar = (ctrl_pressed ^ HasBit(p1, 4)) ? SIG_SEMAPHORE : SIG_ELECTRIC; // the signal variant of the new signal
	SignalType sigtype = (SignalType)GB(p1, 5, 2); // the signal type of the new signal
	bool convert_signal = HasBit(p1, 7); // convert button pressed
	CommandCost cost;

	if (!ValParamTrackOrientation(track) || !IsTileType(tile, MP_RAILWAY) || !EnsureNoTrainOnTrack(tile, track))
		return CMD_ERROR;

	/* Protect against invalid signal copying */
	if (p2 != 0 && (p2 & SignalOnTrack(track)) == 0) return CMD_ERROR;

	/* You can only build signals on plain rail tiles, and the selected track must exist */
	if (!IsPlainRailTile(tile) || !HasTrack(tile, track)) return CMD_ERROR;

	if (!CheckTileOwnership(tile)) return CMD_ERROR;

	{
		/* See if this is a valid track combination for signals, (ie, no overlap) */
		TrackBits trackbits = GetTrackBits(tile);
		if (KillFirstBit(trackbits) != TRACK_BIT_NONE && /* More than one track present */
				trackbits != TRACK_BIT_HORZ &&
				trackbits != TRACK_BIT_VERT) {
			return_cmd_error(STR_1005_NO_SUITABLE_RAILROAD_TRACK);
		}
	}

	/* you can not convert a signal if no signal is on track */
	if (convert_signal && !HasSignalOnTrack(tile, track)) return CMD_ERROR;

	if (!HasSignalOnTrack(tile, track)) {
		/* build new signals */
		cost = CommandCost(EXPENSES_CONSTRUCTION, _price.build_signals);
	} else {
		if (p2 != 0 && sigvar != GetSignalVariant(tile, track)) {
			/* convert signals <-> semaphores */
			cost = CommandCost(EXPENSES_CONSTRUCTION, _price.build_signals + _price.remove_signals);

		} else if (convert_signal) {
			/* convert button pressed */
			if (ctrl_pressed || GetSignalVariant(tile, track) != sigvar) {
				/* convert electric <-> semaphore */
				cost = CommandCost(EXPENSES_CONSTRUCTION, _price.build_signals + _price.remove_signals);
			} else {
				/* it is free to change signal type: normal-pre-exit-combo */
				cost = CommandCost();
			}

		} else {
			/* it is free to change orientation/pre-exit-combo signals */
			cost = CommandCost();
		}
	}

	if (flags & DC_EXEC) {
		if (!HasSignals(tile)) {
			/* there are no signals at all on this tile yet */
			SetHasSignals(tile, true);
			SetSignalStates(tile, 0xF); // all signals are on
			SetPresentSignals(tile, 0); // no signals built by default
			SetSignalType(tile, track, sigtype);
			SetSignalVariant(tile, track, sigvar);
		}

		if (p2 == 0) {
			if (!HasSignalOnTrack(tile, track)) {
				/* build new signals */
				SetPresentSignals(tile, GetPresentSignals(tile) | SignalOnTrack(track));
				SetSignalType(tile, track, sigtype);
				SetSignalVariant(tile, track, sigvar);
			} else {
				if (convert_signal) {
					/* convert signal button pressed */
					if (ctrl_pressed) {
						/* toggle the pressent signal variant: SIG_ELECTRIC <-> SIG_SEMAPHORE */
						SetSignalVariant(tile, track, (GetSignalVariant(tile, track) == SIG_ELECTRIC) ? SIG_SEMAPHORE : SIG_ELECTRIC);

					} else {
						/* convert the present signal to the chosen type and variant */
						SetSignalType(tile, track, sigtype);
						SetSignalVariant(tile, track, sigvar);
					}

				} else if (ctrl_pressed) {
					/* cycle between normal -> pre -> exit -> combo -> ... */
					sigtype = GetSignalType(tile, track);

					SetSignalType(tile, track, sigtype == SIGTYPE_COMBO ? SIGTYPE_NORMAL : (SignalType)(sigtype + 1));
				} else {
					/* cycle the signal side: both -> left -> right -> both -> ... */
					CycleSignalSide(tile, track);
				}
			}
		} else {
			/* If CmdBuildManySignals is called with copying signals, just copy the
			 * direction of the first signal given as parameter by CmdBuildManySignals */
			SetPresentSignals(tile, (GetPresentSignals(tile) & ~SignalOnTrack(track)) | (p2 & SignalOnTrack(track)));
			SetSignalVariant(tile, track, sigvar);
		}

		MarkTileDirtyByTile(tile);
		AddTrackToSignalBuffer(tile, track, _current_player);
		YapfNotifyTrackLayoutChange(tile, track);
	}

	return cost;
}

static bool CheckSignalAutoFill(TileIndex &tile, Trackdir &trackdir, int &signal_ctr, bool remove)
{
	tile = AddTileIndexDiffCWrap(tile, _trackdelta[trackdir]);
	if (tile == INVALID_TILE) return false;

	/* Check for track bits on the new tile */
	TrackdirBits trackdirbits = TrackStatusToTrackdirBits(GetTileTrackStatus(tile, TRANSPORT_RAIL, 0));

	if (TracksOverlap(TrackdirBitsToTrackBits(trackdirbits))) return false;
	trackdirbits &= TrackdirReachesTrackdirs(trackdir);

	/* No track bits, must stop */
	if (trackdirbits == TRACKDIR_BIT_NONE) return false;

	/* Get the first track dir */
	trackdir = RemoveFirstTrackdir(&trackdirbits);

	/* Any left? It's a junction so we stop */
	if (trackdirbits != TRACKDIR_BIT_NONE) return false;

	switch (GetTileType(tile)) {
		case MP_RAILWAY:
			if (IsRailDepot(tile)) return false;
			if (!remove && HasSignalOnTrack(tile, TrackdirToTrack(trackdir))) return false;
			signal_ctr++;
			if (IsDiagonalTrackdir(trackdir)) {
				signal_ctr++;
				/* Ensure signal_ctr even so X and Y pieces get signals */
				ClrBit(signal_ctr, 0);
			}
			return true;

		case MP_ROAD:
			if (!IsLevelCrossing(tile)) return false;
			signal_ctr += 2;
			return true;

		case MP_TUNNELBRIDGE: {
			TileIndex orig_tile = tile; // backup old value

			if (GetTunnelBridgeTransportType(tile) != TRANSPORT_RAIL) return false;
			if (GetTunnelBridgeDirection(tile) != TrackdirToExitdir(trackdir)) return false;

			/* Skip to end of tunnel or bridge
			 * note that tile is a parameter by reference, so it must be updated */
			tile = GetOtherTunnelBridgeEnd(tile);

			signal_ctr += (GetTunnelBridgeLength(orig_tile, tile) + 2) * 2;
			return true;
		}

		default: return false;
	}
}

/** Build many signals by dragging; AutoSignals
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1  end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit  0- 2) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit  3)    - 1 = override signal/semaphore, or pre/exit/combo signal (CTRL-toggle)
 * - p2 = (bit  4)    - 0 = signals, 1 = semaphores
 * - p2 = (bit  5)    - 0 = build, 1 = remove signals
 * - p2 = (bit  6)    - 0 = selected stretch, 1 = auto fill
 * - p2 = (bit 24-31) - user defined signals_density
 */
static CommandCost CmdSignalTrackHelper(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	CommandCost ret, total_cost(EXPENSES_CONSTRUCTION);
	int signal_ctr;
	byte signals;
	bool error = true;
	TileIndex end_tile;
	TileIndex start_tile = tile;

	Track track = (Track)GB(p2, 0, 3);
	bool mode = HasBit(p2, 3);
	bool semaphores = HasBit(p2, 4);
	bool remove = HasBit(p2, 5);
	bool autofill = HasBit(p2, 6);
	Trackdir trackdir = TrackToTrackdir(track);
	byte signal_density = GB(p2, 24, 8);

	if (p1 >= MapSize()) return CMD_ERROR;
	end_tile = p1;
	if (signal_density == 0 || signal_density > 20) return CMD_ERROR;

	if (!IsTileType(tile, MP_RAILWAY)) return CMD_ERROR;

	/* for vertical/horizontal tracks, double the given signals density
	 * since the original amount will be too dense (shorter tracks) */
	signal_density *= 2;

	if (CmdFailed(ValidateAutoDrag(&trackdir, tile, end_tile))) return CMD_ERROR;

	track = TrackdirToTrack(trackdir); /* trackdir might have changed, keep track in sync */
	Trackdir start_trackdir = trackdir;

	/* Autofill must start on a valid track to be able to avoid loops */
	if (autofill && !HasTrack(tile, track)) return CMD_ERROR;

	/* copy the signal-style of the first rail-piece if existing */
	if (HasSignals(tile)) {
		signals = GetPresentSignals(tile) & SignalOnTrack(track);
		if (signals == 0) signals = SignalOnTrack(track); /* Can this actually occur? */

		/* copy signal/semaphores style (independent of CTRL) */
		semaphores = GetSignalVariant(tile, track) != SIG_ELECTRIC;
	} else { // no signals exist, drag a two-way signal stretch
		signals = SignalOnTrack(track);
	}

	byte signal_dir = 0;
	if (signals & SignalAlongTrackdir(trackdir))   SetBit(signal_dir, 0);
	if (signals & SignalAgainstTrackdir(trackdir)) SetBit(signal_dir, 1);

	/* signal_ctr         - amount of tiles already processed
	 * signals_density    - patch setting to put signal on every Nth tile (double space on |, -- tracks)
	 **********
	 * trackdir   - trackdir to build with autorail
	 * semaphores - semaphores or signals
	 * signals    - is there a signal/semaphore on the first tile, copy its style (two-way/single-way)
	 *              and convert all others to semaphore/signal
	 * remove     - 1 remove signals, 0 build signals */
	signal_ctr = 0;
	for (;;) {
		/* only build/remove signals with the specified density */
		if ((remove && autofill) || signal_ctr % signal_density == 0) {
			uint32 p1 = GB(TrackdirToTrack(trackdir), 0, 3);
			SB(p1, 3, 1, mode);
			SB(p1, 4, 1, semaphores);

			/* Pick the correct orientation for the track direction */
			signals = 0;
			if (HasBit(signal_dir, 0)) signals |= SignalAlongTrackdir(trackdir);
			if (HasBit(signal_dir, 1)) signals |= SignalAgainstTrackdir(trackdir);

			ret = DoCommand(tile, p1, signals, flags, remove ? CMD_REMOVE_SIGNALS : CMD_BUILD_SIGNALS);

			/* Be user-friendly and try placing signals as much as possible */
			if (CmdSucceeded(ret)) {
				error = false;
				total_cost.AddCost(ret);
			}
		}

		if (autofill) {
			if (!CheckSignalAutoFill(tile, trackdir, signal_ctr, remove)) break;

			/* Prevent possible loops */
			if (tile == start_tile && trackdir == start_trackdir) break;
		} else {
			if (tile == end_tile) break;

			tile += ToTileIndexDiff(_trackdelta[trackdir]);
			signal_ctr++;

			/* toggle railbit for the non-diagonal tracks (|, -- tracks) */
			if (IsDiagonalTrackdir(trackdir)) {
				signal_ctr++;
			} else {
				ToggleBit(trackdir, 0);
			}
		}
	}

	return error ? CMD_ERROR : total_cost;
}

/** Build signals on a stretch of track.
 * Stub for the unified signal builder/remover
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1  end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit  0- 2) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit  3)    - 1 = override signal/semaphore, or pre/exit/combo signal (CTRL-toggle)
 * - p2 = (bit  4)    - 0 = signals, 1 = semaphores
 * - p2 = (bit  5)    - 0 = build, 1 = remove signals
 * - p2 = (bit  6)    - 0 = selected stretch, 1 = auto fill
 * - p2 = (bit 24-31) - user defined signals_density
 * @see CmdSignalTrackHelper
 */
CommandCost CmdBuildSignalTrack(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	return CmdSignalTrackHelper(tile, flags, p1, p2);
}

/** Remove signals
 * @param tile coordinates where signal is being deleted from
 * @param flags operation to perform
 * @param p1 various bitstuffed elements, only track information is used
 *           - (bit  0- 2) - track-orientation, valid values: 0-5 (Track enum)
 *           - (bit  3)    - override signal/semaphore, or pre/exit/combo signal (CTRL-toggle)
 *           - (bit  4)    - 0 = signals, 1 = semaphores
 * @param p2 unused
 */
CommandCost CmdRemoveSingleSignal(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	Track track = (Track)GB(p1, 0, 3);

	if (!ValParamTrackOrientation(track) ||
			!IsTileType(tile, MP_RAILWAY) ||
			!EnsureNoTrainOnTrack(tile, track) ||
			!HasSignalOnTrack(tile, track)) {
		return CMD_ERROR;
	}

	/* Only water can remove signals from anyone */
	if (_current_player != OWNER_WATER && !CheckTileOwnership(tile)) return CMD_ERROR;

	/* Do it? */
	if (flags & DC_EXEC) {
		SetPresentSignals(tile, GetPresentSignals(tile) & ~SignalOnTrack(track));

		/* removed last signal from tile? */
		if (GetPresentSignals(tile) == 0) {
			SetSignalStates(tile, 0);
			SetHasSignals(tile, false);
			SetSignalVariant(tile, INVALID_TRACK, SIG_ELECTRIC); // remove any possible semaphores
		}

		AddTrackToSignalBuffer(tile, track, GetTileOwner(tile));
		YapfNotifyTrackLayoutChange(tile, track);

		MarkTileDirtyByTile(tile);
	}

	return CommandCost(EXPENSES_CONSTRUCTION, _price.remove_signals);
}

/** Remove signals on a stretch of track.
 * Stub for the unified signal builder/remover
 * @param tile start tile of drag
 * @param flags operation to perform
 * @param p1  end tile of drag
 * @param p2 various bitstuffed elements
 * - p2 = (bit  0- 2) - track-orientation, valid values: 0-5 (Track enum)
 * - p2 = (bit  3)    - 1 = override signal/semaphore, or pre/exit/combo signal (CTRL-toggle)
 * - p2 = (bit  4)    - 0 = signals, 1 = semaphores
 * - p2 = (bit  5)    - 0 = build, 1 = remove signals
 * - p2 = (bit  6)    - 0 = selected stretch, 1 = auto fill
 * - p2 = (bit 24-31) - user defined signals_density
 * @see CmdSignalTrackHelper
 */
CommandCost CmdRemoveSignalTrack(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	return CmdSignalTrackHelper(tile, flags, p1, SetBit(p2, 5)); // bit 5 is remove bit
}

/** Update power of train under which is the railtype being converted */
void *UpdateTrainPowerProc(Vehicle *v, void *data)
{
	/* Similiar checks as in TrainPowerChanged() */

	if (v->type == VEH_TRAIN && !IsArticulatedPart(v)) {
		const RailVehicleInfo *rvi = RailVehInfo(v->engine_type);
		if (GetVehicleProperty(v, 0x0B, rvi->power) != 0) TrainPowerChanged(v->First());
	}

	return NULL;
}

/** Convert one rail type to the other. You can convert normal rail to
 * monorail/maglev easily or vice-versa.
 * @param tile end tile of rail conversion drag
 * @param flags operation to perform
 * @param p1 start tile of drag
 * @param p2 new railtype to convert to
 */
CommandCost CmdConvertRail(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
{
	CommandCost cost(EXPENSES_CONSTRUCTION);
	RailType totype = (RailType)p2;

	if (!ValParamRailtype(totype)) return CMD_ERROR;
	if (p1 >= MapSize()) return CMD_ERROR;

	uint ex = TileX(tile);
	uint ey = TileY(tile);
	uint sx = TileX(p1);
	uint sy = TileY(p1);

	/* make sure sx,sy are smaller than ex,ey */
	if (ex < sx) Swap(ex, sx);
	if (ey < sy) Swap(ey, sy);

	_error_message = STR_1005_NO_SUITABLE_RAILROAD_TRACK; // by default, there is no track to convert

	for (uint x = sx; x <= ex; ++x) {
		for (uint y = sy; y <= ey; ++y) {
			TileIndex tile = TileXY(x, y);
			TileType tt = GetTileType(tile);

			/* Check if there is any track on tile */
			switch (tt) {
				case MP_RAILWAY:
					break;
				case MP_STATION:
					if (!IsRailwayStation(tile)) continue;
					break;
				case MP_ROAD:
					if (!IsLevelCrossing(tile)) continue;
					break;
				case MP_TUNNELBRIDGE:
					if (GetTunnelBridgeTransportType(tile) != TRANSPORT_RAIL) continue;
					break;
				default: continue;
			}

			/* Original railtype we are converting from */
			RailType type = GetRailType(tile);

			/* Converting to the same type or converting 'hidden' elrail -> rail */
			if (type == totype || (_patches.disable_elrails && totype == RAILTYPE_RAIL && type == RAILTYPE_ELECTRIC)) continue;

			/* Trying to convert other's rail */
			if (!CheckTileOwnership(tile)) continue;

			/* Vehicle on the tile when not converting Rail <-> ElRail
			 * Tunnels and bridges have special check later */
			if (tt != MP_TUNNELBRIDGE) {
				if (!IsCompatibleRail(type, totype) && !EnsureNoVehicleOnGround(tile)) continue;
				if (flags & DC_EXEC) { // we can safely convert, too
					SetRailType(tile, totype);
					MarkTileDirtyByTile(tile);
					/* update power of train engines on this tile */
					VehicleFromPos(tile, NULL, &UpdateTrainPowerProc);
				}
			}

			switch (tt) {
				case MP_RAILWAY:
					switch (GetRailTileType(tile)) {
						case RAIL_TILE_WAYPOINT:
							if (flags & DC_EXEC) {
								/* notify YAPF about the track layout change */
								YapfNotifyTrackLayoutChange(tile, AxisToTrack(GetWaypointAxis(tile)));
							}
							cost.AddCost(RailConvertCost(type, totype));
							break;

						case RAIL_TILE_DEPOT:
							if (flags & DC_EXEC) {
								/* notify YAPF about the track layout change */
								YapfNotifyTrackLayoutChange(tile, AxisToTrack(DiagDirToAxis(GetRailDepotDirection(tile))));

								/* Update build vehicle window related to this depot */
								InvalidateWindowData(WC_VEHICLE_DEPOT, tile);
								InvalidateWindowData(WC_BUILD_VEHICLE, tile);
							}
							cost.AddCost(RailConvertCost(type, totype));
							break;

						default: // RAIL_TILE_NORMAL, RAIL_TILE_SIGNALS
							if (flags & DC_EXEC) {
								/* notify YAPF about the track layout change */
								TrackBits tracks = GetTrackBits(tile);
								while (tracks != TRACK_BIT_NONE) {
									YapfNotifyTrackLayoutChange(tile, RemoveFirstTrack(&tracks));
								}
							}
							cost.AddCost(RailConvertCost(type, totype) * CountBits(GetTrackBits(tile)));
							break;
					}
					break;

				case MP_TUNNELBRIDGE: {
					TileIndex endtile = GetOtherTunnelBridgeEnd(tile);

					/* If both ends of tunnel/bridge are in the range, do not try to convert twice -
					 * it would cause assert because of different test and exec runs */
					if (endtile < tile && TileX(endtile) >= sx && TileX(endtile) <= ex &&
							TileY(endtile) >= sy && TileY(endtile) <= ey) continue;

					/* When not coverting rail <-> el. rail, any vehicle cannot be in tunnel/bridge */
					if (!IsCompatibleRail(GetRailType(tile), totype) &&
							GetVehicleTunnelBridge(tile, endtile) != NULL) continue;

					if (flags & DC_EXEC) {
						SetRailType(tile, totype);
						SetRailType(endtile, totype);

						VehicleFromPos(tile, NULL, &UpdateTrainPowerProc);
						VehicleFromPos(endtile, NULL, &UpdateTrainPowerProc);

						Track track = AxisToTrack(DiagDirToAxis(GetTunnelBridgeDirection(tile)));

						YapfNotifyTrackLayoutChange(tile, track);
						YapfNotifyTrackLayoutChange(endtile, track);

						MarkTileDirtyByTile(tile);
						MarkTileDirtyByTile(endtile);

						if (IsBridge(tile)) {
							TileIndexDiff delta = TileOffsByDiagDir(GetTunnelBridgeDirection(tile));
							TileIndex t = tile + delta;
							for (; t != endtile; t += delta) MarkTileDirtyByTile(t); // TODO encapsulate this into a function
						}
					}

					cost.AddCost((GetTunnelBridgeLength(tile, endtile) + 2) * RailConvertCost(type, totype));
				} break;

				default: // MP_STATION, MP_ROAD
					if (flags & DC_EXEC) {
						Track track = ((tt == MP_STATION) ? GetRailStationTrack(tile) : GetCrossingRailTrack(tile));
						YapfNotifyTrackLayoutChange(tile, track);
					}

					cost.AddCost(RailConvertCost(type, totype));
					break;
			}
		}
	}

	return (cost.GetCost() == 0) ? CMD_ERROR : cost;
}

static CommandCost RemoveTrainDepot(TileIndex tile, uint32 flags)
{
	if (!CheckTileOwnership(tile) && _current_player != OWNER_WATER)
		return CMD_ERROR;

	if (!EnsureNoVehicleOnGround(tile))
		return CMD_ERROR;

	if (flags & DC_EXEC) {
		/* read variables before the depot is removed */
		DiagDirection dir = GetRailDepotDirection(tile);
		Owner owner = GetTileOwner(tile);

		DoClearSquare(tile);
		delete GetDepotByTile(tile);
		AddSideToSignalBuffer(tile, dir, owner);
		YapfNotifyTrackLayoutChange(tile, TrackdirToTrack(DiagdirToDiagTrackdir(dir)));
	}

	return CommandCost(EXPENSES_CONSTRUCTION, _price.remove_train_depot);
}

static CommandCost ClearTile_Track(TileIndex tile, byte flags)
{
	CommandCost cost(EXPENSES_CONSTRUCTION);
	CommandCost ret;

	if (flags & DC_AUTO) {
		if (!IsTileOwner(tile, _current_player))
			return_cmd_error(STR_1024_AREA_IS_OWNED_BY_ANOTHER);

		if (IsPlainRailTile(tile)) {
			return_cmd_error(STR_1008_MUST_REMOVE_RAILROAD_TRACK);
		} else {
			return_cmd_error(STR_2004_BUILDING_MUST_BE_DEMOLISHED);
		}
	}

	switch (GetRailTileType(tile)) {
		case RAIL_TILE_SIGNALS:
		case RAIL_TILE_NORMAL: {
			Slope tileh = GetTileSlope(tile, NULL);
			/* Is there flat water on the lower halftile, that gets cleared expensively? */
			bool water_ground = (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh));

			TrackBits tracks = GetTrackBits(tile);
			while (tracks != TRACK_BIT_NONE) {
				Track track = RemoveFirstTrack(&tracks);
				ret = DoCommand(tile, 0, track, flags, CMD_REMOVE_SINGLE_RAIL);
				if (CmdFailed(ret)) return CMD_ERROR;
				cost.AddCost(ret);
			}

			if (water_ground) {
				/* The track was removed, and left a coast tile. Now also clear the water. */
				if (flags & DC_EXEC) DoClearSquare(tile);
				cost.AddCost(_price.clear_water);
			}

			return cost;
		}

		case RAIL_TILE_DEPOT:
			return RemoveTrainDepot(tile, flags);

		case RAIL_TILE_WAYPOINT:
			return RemoveTrainWaypoint(tile, flags, false);

		default:
			return CMD_ERROR;
	}
}

/**
 * Get surface height in point (x,y)
 * On tiles with halftile foundations move (x,y) to a save point wrt. track
 */
static uint GetSaveSlopeZ(uint x, uint y, Track track)
{
	switch (track) {
		case TRACK_UPPER: x &= ~0xF; y &= ~0xF; break;
		case TRACK_LOWER: x |=  0xF; y |=  0xF; break;
		case TRACK_LEFT:  x |=  0xF; y &= ~0xF; break;
		case TRACK_RIGHT: x &= ~0xF; y |=  0xF; break;
		default: break;
	}
	return GetSlopeZ(x, y);
}

static void DrawSingleSignal(TileIndex tile, Track track, byte condition, uint image, uint pos)
{
	bool side = (_opt.road_side != 0) && _patches.signal_side;
	static const Point SignalPositions[2][12] = {
		{      /* Signals on the left side */
		/*  LEFT      LEFT      RIGHT     RIGHT     UPPER     UPPER */
			{ 8,  5}, {14,  1}, { 1, 14}, { 9, 11}, { 1,  0}, { 3, 10},
		/*  LOWER     LOWER     X         X         Y         Y     */
			{11,  4}, {14, 14}, {11,  3}, { 4, 13}, { 3,  4}, {11, 13}
		}, {   /* Signals on the right side */
		/*  LEFT      LEFT      RIGHT     RIGHT     UPPER     UPPER */
			{14,  1}, {12, 10}, { 4,  6}, { 1, 14}, {10,  4}, { 0,  1},
		/*  LOWER     LOWER     X         X         Y         Y     */
			{14, 14}, { 5, 12}, {11, 13}, { 4,  3}, {13,  4}, { 3, 11}
		}
	};

	uint x = TileX(tile) * TILE_SIZE + SignalPositions[side][pos].x;
	uint y = TileY(tile) * TILE_SIZE + SignalPositions[side][pos].y;

	SpriteID sprite;

	SignalType type       = GetSignalType(tile, track);
	SignalVariant variant = GetSignalVariant(tile, track);

	if (type == SIGTYPE_NORMAL && variant == SIG_ELECTRIC) {
		/* Normal electric signals are picked from original sprites. */
		sprite = SPR_ORIGINAL_SIGNALS_BASE + image + condition;
	} else {
		/* All other signals are picked from add on sprites. */
		sprite = SPR_SIGNALS_BASE + (type - 1) * 16 + variant * 64 + image + condition;
	}

	AddSortableSpriteToDraw(sprite, PAL_NONE, x, y, 1, 1, BB_HEIGHT_UNDER_BRIDGE, GetSaveSlopeZ(x, y, track));
}

static uint32 _drawtile_track_palette;


static void DrawTrackFence_NW(const TileInfo *ti)
{
	SpriteID image = SPR_TRACK_FENCE_FLAT_X;
	if (ti->tileh != SLOPE_FLAT) image = (ti->tileh & SLOPE_S) ? SPR_TRACK_FENCE_SLOPE_SW : SPR_TRACK_FENCE_SLOPE_NE;
	AddSortableSpriteToDraw(image, _drawtile_track_palette,
		ti->x, ti->y + 1, 16, 1, 4, ti->z);
}

static void DrawTrackFence_SE(const TileInfo *ti)
{
	SpriteID image = SPR_TRACK_FENCE_FLAT_X;
	if (ti->tileh != SLOPE_FLAT) image = (ti->tileh & SLOPE_S) ? SPR_TRACK_FENCE_SLOPE_SW : SPR_TRACK_FENCE_SLOPE_NE;
	AddSortableSpriteToDraw(image, _drawtile_track_palette,
		ti->x, ti->y + TILE_SIZE - 1, 16, 1, 4, ti->z);
}

static void DrawTrackFence_NW_SE(const TileInfo *ti)
{
	DrawTrackFence_NW(ti);
	DrawTrackFence_SE(ti);
}

static void DrawTrackFence_NE(const TileInfo *ti)
{
	SpriteID image = SPR_TRACK_FENCE_FLAT_Y;
	if (ti->tileh != SLOPE_FLAT) image = (ti->tileh & SLOPE_S) ? SPR_TRACK_FENCE_SLOPE_SE : SPR_TRACK_FENCE_SLOPE_NW;
	AddSortableSpriteToDraw(image, _drawtile_track_palette,
		ti->x + 1, ti->y, 1, 16, 4, ti->z);
}

static void DrawTrackFence_SW(const TileInfo *ti)
{
	SpriteID image = SPR_TRACK_FENCE_FLAT_Y;
	if (ti->tileh != SLOPE_FLAT) image = (ti->tileh & SLOPE_S) ? SPR_TRACK_FENCE_SLOPE_SE : SPR_TRACK_FENCE_SLOPE_NW;
	AddSortableSpriteToDraw(image, _drawtile_track_palette,
		ti->x + TILE_SIZE - 1, ti->y, 1, 16, 4, ti->z);
}

static void DrawTrackFence_NE_SW(const TileInfo *ti)
{
	DrawTrackFence_NE(ti);
	DrawTrackFence_SW(ti);
}

/**
 * Draw fence at eastern side of track.
 */
static void DrawTrackFence_NS_1(const TileInfo *ti)
{
	uint z = ti->z + GetSlopeZInCorner(RemoveHalftileSlope(ti->tileh), CORNER_W);
	AddSortableSpriteToDraw(SPR_TRACK_FENCE_FLAT_VERT, _drawtile_track_palette,
		ti->x + TILE_SIZE / 2, ti->y + TILE_SIZE / 2, 1, 1, 4, z);
}

/**
 * Draw fence at western side of track.
 */
static void DrawTrackFence_NS_2(const TileInfo *ti)
{
	uint z = ti->z + GetSlopeZInCorner(RemoveHalftileSlope(ti->tileh), CORNER_E);
	AddSortableSpriteToDraw(SPR_TRACK_FENCE_FLAT_VERT, _drawtile_track_palette,
		ti->x + TILE_SIZE / 2, ti->y + TILE_SIZE / 2, 1, 1, 4, z);
}

/**
 * Draw fence at southern side of track.
 */
static void DrawTrackFence_WE_1(const TileInfo *ti)
{
	uint z = ti->z + GetSlopeZInCorner(RemoveHalftileSlope(ti->tileh), CORNER_N);
	AddSortableSpriteToDraw(SPR_TRACK_FENCE_FLAT_HORZ, _drawtile_track_palette,
		ti->x + TILE_SIZE / 2, ti->y + TILE_SIZE / 2, 1, 1, 4, z);
}

/**
 * Draw fence at northern side of track.
 */
static void DrawTrackFence_WE_2(const TileInfo *ti)
{
	uint z = ti->z + GetSlopeZInCorner(RemoveHalftileSlope(ti->tileh), CORNER_S);
	AddSortableSpriteToDraw(SPR_TRACK_FENCE_FLAT_HORZ, _drawtile_track_palette,
		ti->x + TILE_SIZE / 2, ti->y + TILE_SIZE / 2, 1, 1, 4, z);
}


static void DrawTrackDetails(const TileInfo* ti)
{
	switch (GetRailGroundType(ti->tile)) {
		case RAIL_GROUND_FENCE_NW:     DrawTrackFence_NW(ti);    break;
		case RAIL_GROUND_FENCE_SE:     DrawTrackFence_SE(ti);    break;
		case RAIL_GROUND_FENCE_SENW:   DrawTrackFence_NW_SE(ti); break;
		case RAIL_GROUND_FENCE_NE:     DrawTrackFence_NE(ti);    break;
		case RAIL_GROUND_FENCE_SW:     DrawTrackFence_SW(ti);    break;
		case RAIL_GROUND_FENCE_NESW:   DrawTrackFence_NE_SW(ti); break;
		case RAIL_GROUND_FENCE_VERT1:  DrawTrackFence_NS_1(ti);  break;
		case RAIL_GROUND_FENCE_VERT2:  DrawTrackFence_NS_2(ti);  break;
		case RAIL_GROUND_FENCE_HORIZ1: DrawTrackFence_WE_1(ti);  break;
		case RAIL_GROUND_FENCE_HORIZ2: DrawTrackFence_WE_2(ti);  break;
		case RAIL_GROUND_WATER: {
			Corner track_corner;
			if (IsHalftileSlope(ti->tileh)) {
				/* Steep slope or one-corner-raised slope with halftile foundation */
				track_corner = GetHalftileSlopeCorner(ti->tileh);
			} else {
				/* Three-corner-raised slope */
				track_corner = OppositeCorner(GetHighestSlopeCorner(ComplementSlope(ti->tileh)));
			}
			switch (track_corner) {
				case CORNER_W: DrawTrackFence_NS_1(ti); break;
				case CORNER_S: DrawTrackFence_WE_2(ti); break;
				case CORNER_E: DrawTrackFence_NS_2(ti); break;
				case CORNER_N: DrawTrackFence_WE_1(ti); break;
				default: NOT_REACHED();
			}
			break;
		}
		default: break;
	}
}


/**
 * Draw ground sprite and track bits
 * @param ti TileInfo
 * @param track TrackBits to draw
 */
static void DrawTrackBits(TileInfo* ti, TrackBits track)
{
	/* SubSprite for drawing the track halftile of 'three-corners-raised'-sloped rail sprites. */
	static const int INF = 1000; // big number compared to tilesprite size
	static const SubSprite _halftile_sub_sprite[4] = {
		{ -INF    , -INF  , 32 - 33, INF     }, // CORNER_W, clip 33 pixels from right
		{ -INF    ,  0 + 7, INF    , INF     }, // CORNER_S, clip 7 pixels from top
		{ -31 + 33, -INF  , INF    , INF     }, // CORNER_E, clip 33 pixels from left
		{ -INF    , -INF  , INF    , 30 - 23 }  // CORNER_N, clip 23 pixels from bottom
	};

	const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
	RailGroundType rgt = GetRailGroundType(ti->tile);
	Foundation f = GetRailFoundation(ti->tileh, track);
	Corner halftile_corner = CORNER_INVALID;

	if (IsNonContinuousFoundation(f)) {
		/* Save halftile corner */
		halftile_corner = (f == FOUNDATION_STEEP_BOTH ? GetHighestSlopeCorner(ti->tileh) : GetHalftileFoundationCorner(f));
		/* Draw lower part first */
		track &= ~CornerToTrackBits(halftile_corner);
		f = (f == FOUNDATION_STEEP_BOTH ? FOUNDATION_STEEP_LOWER : FOUNDATION_NONE);
	}

	DrawFoundation(ti, f);
	/* DrawFoundation modifies ti */

	SpriteID image;
	SpriteID pal = PAL_NONE;
	const SubSprite *sub = NULL;
	bool junction = false;

	/* Select the sprite to use. */
	if (track == 0) {
		/* Clear ground (only track on halftile foundation) */
		if (rgt == RAIL_GROUND_WATER) {
			if (IsSteepSlope(ti->tileh)) {
				DrawShoreTile(ti->tileh);
				image = 0;
			} else {
				image = SPR_FLAT_WATER_TILE;
			}
		} else {
			switch (rgt) {
				case RAIL_GROUND_BARREN:     image = SPR_FLAT_BARE_LAND;  break;
				case RAIL_GROUND_ICE_DESERT: image = SPR_FLAT_SNOWY_TILE; break;
				default:                     image = SPR_FLAT_GRASS_TILE; break;
			}
			image += _tileh_to_sprite[ti->tileh];
		}
	} else {
		if (ti->tileh != SLOPE_FLAT) {
			/* track on non-flat ground */
			image = _track_sloped_sprites[ti->tileh - 1] + rti->base_sprites.track_y;
		} else {
			/* track on flat ground */
			(image = rti->base_sprites.track_y, track == TRACK_BIT_Y) ||
			(image++,                           track == TRACK_BIT_X) ||
			(image++,                           track == TRACK_BIT_UPPER) ||
			(image++,                           track == TRACK_BIT_LOWER) ||
			(image++,                           track == TRACK_BIT_RIGHT) ||
			(image++,                           track == TRACK_BIT_LEFT) ||
			(image++,                           track == TRACK_BIT_CROSS) ||

			(image = rti->base_sprites.track_ns, track == TRACK_BIT_HORZ) ||
			(image++,                            track == TRACK_BIT_VERT) ||

			(junction = true, false) ||
			(image = rti->base_sprites.ground, (track & TRACK_BIT_3WAY_NE) == 0) ||
			(image++,                          (track & TRACK_BIT_3WAY_SW) == 0) ||
			(image++,                          (track & TRACK_BIT_3WAY_NW) == 0) ||
			(image++,                          (track & TRACK_BIT_3WAY_SE) == 0) ||
			(image++, true);
		}

		switch (rgt) {
			case RAIL_GROUND_BARREN:     pal = PALETTE_TO_BARE_LAND; break;
			case RAIL_GROUND_ICE_DESERT: image += rti->snow_offset;  break;
			case RAIL_GROUND_WATER: {
				/* three-corner-raised slope */
				DrawShoreTile(ti->tileh);
				Corner track_corner = OppositeCorner(GetHighestSlopeCorner(ComplementSlope(ti->tileh)));
				sub = &(_halftile_sub_sprite[track_corner]);
				break;
			}
			default: break;
		}
	}

	if (image != 0) DrawGroundSprite(image, pal, sub);

	/* Draw track pieces individually for junction tiles */
	if (junction) {
		if (track & TRACK_BIT_X)     DrawGroundSprite(rti->base_sprites.single_y, PAL_NONE);
		if (track & TRACK_BIT_Y)     DrawGroundSprite(rti->base_sprites.single_x, PAL_NONE);
		if (track & TRACK_BIT_UPPER) DrawGroundSprite(rti->base_sprites.single_n, PAL_NONE);
		if (track & TRACK_BIT_LOWER) DrawGroundSprite(rti->base_sprites.single_s, PAL_NONE);
		if (track & TRACK_BIT_LEFT)  DrawGroundSprite(rti->base_sprites.single_w, PAL_NONE);
		if (track & TRACK_BIT_RIGHT) DrawGroundSprite(rti->base_sprites.single_e, PAL_NONE);
	}

	if (IsValidCorner(halftile_corner)) {
		DrawFoundation(ti, HalftileFoundation(halftile_corner));

		/* Draw higher halftile-overlay: Use the sloped sprites with three corners raised. They probably best fit the lightning. */
		Slope fake_slope = SlopeWithThreeCornersRaised(OppositeCorner(halftile_corner));
		image = _track_sloped_sprites[fake_slope - 1] + rti->base_sprites.track_y;
		pal = PAL_NONE;
		switch (rgt) {
			case RAIL_GROUND_BARREN:     pal = PALETTE_TO_BARE_LAND; break;
			case RAIL_GROUND_ICE_DESERT:
			case RAIL_GROUND_HALF_SNOW:  image += rti->snow_offset;  break; // higher part has snow in this case too
			default: break;
		}
		DrawGroundSprite(image, pal, &(_halftile_sub_sprite[halftile_corner]));
	}
}

/** Enums holding the offsets from base signal sprite,
 * according to the side it is representing.
 * The addtion of 2 per enum is necessary in order to "jump" over the
 * green state sprite, all signal sprites being in pair,
 * starting with the off-red state */
enum {
	SIGNAL_TO_SOUTHWEST =  0,
	SIGNAL_TO_NORTHEAST =  2,
	SIGNAL_TO_SOUTHEAST =  4,
	SIGNAL_TO_NORTHWEST =  6,
	SIGNAL_TO_EAST      =  8,
	SIGNAL_TO_WEST      = 10,
	SIGNAL_TO_SOUTH     = 12,
	SIGNAL_TO_NORTH     = 14,
};

static void DrawSignals(TileIndex tile, TrackBits rails)
{
#define MAYBE_DRAW_SIGNAL(x,y,z,t) if (IsSignalPresent(tile, x)) DrawSingleSignal(tile, t, GetSingleSignalState(tile, x), y, z)

	if (!(rails & TRACK_BIT_Y)) {
		if (!(rails & TRACK_BIT_X)) {
			if (rails & TRACK_BIT_LEFT) {
				MAYBE_DRAW_SIGNAL(2, SIGNAL_TO_NORTH, 0, TRACK_LEFT);
				MAYBE_DRAW_SIGNAL(3, SIGNAL_TO_SOUTH, 1, TRACK_LEFT);
			}
			if (rails & TRACK_BIT_RIGHT) {
				MAYBE_DRAW_SIGNAL(0, SIGNAL_TO_NORTH, 2, TRACK_RIGHT);
				MAYBE_DRAW_SIGNAL(1, SIGNAL_TO_SOUTH, 3, TRACK_RIGHT);
			}
			if (rails & TRACK_BIT_UPPER) {
				MAYBE_DRAW_SIGNAL(3, SIGNAL_TO_WEST, 4, TRACK_UPPER);
				MAYBE_DRAW_SIGNAL(2, SIGNAL_TO_EAST, 5, TRACK_UPPER);
			}
			if (rails & TRACK_BIT_LOWER) {
				MAYBE_DRAW_SIGNAL(1, SIGNAL_TO_WEST, 6, TRACK_LOWER);
				MAYBE_DRAW_SIGNAL(0, SIGNAL_TO_EAST, 7, TRACK_LOWER);
			}
		} else {
			MAYBE_DRAW_SIGNAL(3, SIGNAL_TO_SOUTHWEST, 8, TRACK_X);
			MAYBE_DRAW_SIGNAL(2, SIGNAL_TO_NORTHEAST, 9, TRACK_X);
		}
	} else {
		MAYBE_DRAW_SIGNAL(3, SIGNAL_TO_SOUTHEAST, 10, TRACK_Y);
		MAYBE_DRAW_SIGNAL(2, SIGNAL_TO_NORTHWEST, 11, TRACK_Y);
	}
}

static void DrawTile_Track(TileInfo *ti)
{
	const RailtypeInfo *rti = GetRailTypeInfo(GetRailType(ti->tile));
	SpriteID image;

	_drawtile_track_palette = PLAYER_SPRITE_COLOR(GetTileOwner(ti->tile));

	if (IsPlainRailTile(ti->tile)) {
		TrackBits rails = GetTrackBits(ti->tile);

		DrawTrackBits(ti, rails);

		if (HasBit(_display_opt, DO_FULL_DETAIL)) DrawTrackDetails(ti);

		if (HasCatenary(GetRailType(ti->tile))) DrawCatenary(ti);

		if (HasSignals(ti->tile)) DrawSignals(ti->tile, rails);
	} else {
		/* draw depot/waypoint */
		const DrawTileSprites* dts;
		const DrawTileSeqStruct* dtss;
		uint32 relocation;

		if (ti->tileh != SLOPE_FLAT) DrawFoundation(ti, FOUNDATION_LEVELED);

		if (IsRailDepot(ti->tile)) {
			dts = &_depot_gfx_table[GetRailDepotDirection(ti->tile)];

			relocation = rti->total_offset;

			image = dts->ground.sprite;
			if (image != SPR_FLAT_GRASS_TILE) image += rti->total_offset;

			/* adjust ground tile for desert
			 * don't adjust for snow, because snow in depots looks weird */
			if (IsSnowRailGround(ti->tile) && _opt.landscape == LT_TROPIC) {
				if (image != SPR_FLAT_GRASS_TILE) {
					image += rti->snow_offset; // tile with tracks
				} else {
					image = SPR_FLAT_SNOWY_TILE; // flat ground
				}
			}
		} else {
			/* look for customization */
			byte stat_id = GetWaypointByTile(ti->tile)->stat_id;
			const StationSpec *statspec = GetCustomStationSpec(STAT_CLASS_WAYP, stat_id);

			if (statspec != NULL) {
				/* emulate station tile - open with building */
				const Station* st = ComposeWaypointStation(ti->tile);
				uint gfx = 2;

				if (HasBit(statspec->callbackmask, CBM_STATION_SPRITE_LAYOUT)) {
					uint16 callback = GetStationCallback(CBID_STATION_SPRITE_LAYOUT, 0, 0, statspec, st, ti->tile);
					if (callback != CALLBACK_FAILED) gfx = callback;
				}

				if (statspec->renderdata == NULL) {
					dts = GetStationTileLayout(STATION_RAIL, gfx);
				} else {
					dts = &statspec->renderdata[(gfx < statspec->tiles ? gfx : 0) + GetWaypointAxis(ti->tile)];
				}

				if (dts != NULL && dts->seq != NULL) {
					relocation = GetCustomStationRelocation(statspec, st, ti->tile);

					image = dts->ground.sprite;
					if (HasBit(image, SPRITE_MODIFIER_USE_OFFSET)) {
						image += GetCustomStationGroundRelocation(statspec, st, ti->tile);
						image += rti->custom_ground_offset;
					} else {
						image += rti->total_offset;
					}
				} else {
					goto default_waypoint;
				}
			} else {
default_waypoint:
				/* There is no custom layout, fall back to the default graphics */
				dts = &_waypoint_gfx_table[GetWaypointAxis(ti->tile)];
				relocation = 0;
				image = dts->ground.sprite + rti->total_offset;
				if (IsSnowRailGround(ti->tile)) image += rti->snow_offset;
			}
		}

		DrawGroundSprite(image, PAL_NONE);

		if (HasCatenary(GetRailType(ti->tile))) DrawCatenary(ti);

		foreach_draw_tile_seq(dtss, dts->seq) {
			SpriteID image = dtss->image.sprite;
			SpriteID pal;

			/* Unlike stations, our default waypoint has no variation for
			 * different railtype, so don't use the railtype offset if
			 * no relocation is set */
			if (HasBit(image, SPRITE_MODIFIER_USE_OFFSET)) {
				image += rti->total_offset;
			} else {
				image += relocation;
			}

			if (!(!HasBit(image, SPRITE_MODIFIER_OPAQUE) && IsTransparencySet(TO_BUILDINGS)) && HasBit(image, PALETTE_MODIFIER_COLOR)) {
				pal = _drawtile_track_palette;
			} else {
				pal = dtss->image.pal;
			}

			if ((byte)dtss->delta_z != 0x80) {
				AddSortableSpriteToDraw(
					image, pal,
					ti->x + dtss->delta_x, ti->y + dtss->delta_y,
					dtss->size_x, dtss->size_y,
					dtss->size_z, ti->z + dtss->delta_z,
					!HasBit(image, SPRITE_MODIFIER_OPAQUE) && IsTransparencySet(TO_BUILDINGS)
				);
			} else {
				AddChildSpriteScreen(image, pal, dtss->delta_x, dtss->delta_y);
			}
		}
	}
	DrawBridgeMiddle(ti);
}


static void DrawTileSequence(int x, int y, SpriteID ground, const DrawTileSeqStruct* dtss, uint32 offset)
{
	SpriteID palette = PLAYER_SPRITE_COLOR(_local_player);

	DrawSprite(ground, PAL_NONE, x, y);
	for (; dtss->image.sprite != 0; dtss++) {
		Point pt = RemapCoords(dtss->delta_x, dtss->delta_y, dtss->delta_z);
		SpriteID image = dtss->image.sprite + offset;

		DrawSprite(image, HasBit(image, PALETTE_MODIFIER_COLOR) ? palette : PAL_NONE, x + pt.x, y + pt.y);
	}
}

void DrawTrainDepotSprite(int x, int y, int dir, RailType railtype)
{
	const DrawTileSprites* dts = &_depot_gfx_table[dir];
	SpriteID image = dts->ground.sprite;
	uint32 offset = GetRailTypeInfo(railtype)->total_offset;

	if (image != SPR_FLAT_GRASS_TILE) image += offset;
	DrawTileSequence(x + 33, y + 17, image, dts->seq, offset);
}

void DrawDefaultWaypointSprite(int x, int y, RailType railtype)
{
	uint32 offset = GetRailTypeInfo(railtype)->total_offset;
	const DrawTileSprites* dts = &_waypoint_gfx_table[AXIS_X];

	DrawTileSequence(x, y, dts->ground.sprite + offset, dts->seq, 0);
}

static uint GetSlopeZ_Track(TileIndex tile, uint x, uint y)
{
	uint z;
	Slope tileh = GetTileSlope(tile, &z);

	if (tileh == SLOPE_FLAT) return z;
	if (IsPlainRailTile(tile)) {
		z += ApplyFoundationToSlope(GetRailFoundation(tileh, GetTrackBits(tile)), &tileh);
		return z + GetPartialZ(x & 0xF, y & 0xF, tileh);
	} else {
		return z + TILE_HEIGHT;
	}
}

static Foundation GetFoundation_Track(TileIndex tile, Slope tileh)
{
	return IsPlainRailTile(tile) ? GetRailFoundation(tileh, GetTrackBits(tile)) : FlatteningFoundation(tileh);
}

static void GetAcceptedCargo_Track(TileIndex tile, AcceptedCargo ac)
{
	/* not used */
}

static void AnimateTile_Track(TileIndex tile)
{
	/* not used */
}

static void TileLoop_Track(TileIndex tile)
{
	RailGroundType old_ground = GetRailGroundType(tile);
	RailGroundType new_ground;

	if (old_ground == RAIL_GROUND_WATER) {
		TileLoop_Water(tile);
		return;
	}

	switch (_opt.landscape) {
		case LT_ARCTIC: {
			uint z;
			Slope slope = GetTileSlope(tile, &z);
			bool half = false;

			/* for non-flat track, use lower part of track
			 * in other cases, use the highest part with track */
			if (IsPlainRailTile(tile)) {
				TrackBits track = GetTrackBits(tile);
				Foundation f = GetRailFoundation(slope, track);

				switch (f) {
					case FOUNDATION_NONE:
						/* no foundation - is the track on the upper side of three corners raised tile? */
						if (IsSlopeWithThreeCornersRaised(slope)) z += TILE_HEIGHT;
						break;

					case FOUNDATION_INCLINED_X:
					case FOUNDATION_INCLINED_Y:
						/* sloped track - is it on a steep slope? */
						if (IsSteepSlope(slope)) z += TILE_HEIGHT;
						break;

					case FOUNDATION_STEEP_LOWER:
						/* only lower part of steep slope */
						z += TILE_HEIGHT;
						break;

					default:
						/* if it is a steep slope, then there is a track on higher part */
						if (IsSteepSlope(slope)) z += TILE_HEIGHT;
						z += TILE_HEIGHT;
						break;
				}

				half = IsInsideMM(f, FOUNDATION_STEEP_BOTH, FOUNDATION_HALFTILE_N + 1);
			} else {
				/* is the depot on a non-flat tile? */
				if (slope != SLOPE_FLAT) z += TILE_HEIGHT;
			}

			/* 'z' is now the lowest part of the highest track bit -
			 * for sloped track, it is 'z' of lower part
			 * for two track bits, it is 'z' of higher track bit
			 * For non-continuous foundations (and STEEP_BOTH), 'half' is set */
			if (z > GetSnowLine()) {
				if (half && z - GetSnowLine() == TILE_HEIGHT) {
					/* track on non-continuous foundation, lower part is not under snow */
					new_ground = RAIL_GROUND_HALF_SNOW;
				} else {
					new_ground = RAIL_GROUND_ICE_DESERT;
				}
				goto set_ground;
			}
			break;
			}

		case LT_TROPIC:
			if (GetTropicZone(tile) == TROPICZONE_DESERT) {
				new_ground = RAIL_GROUND_ICE_DESERT;
				goto set_ground;
			}
			break;
	}

	if (!IsPlainRailTile(tile)) return;

	new_ground = RAIL_GROUND_GRASS;

	if (old_ground != RAIL_GROUND_BARREN) { // wait until bottom is green
		/* determine direction of fence */
		TrackBits rail = GetTrackBits(tile);

		switch (rail) {
			case TRACK_BIT_UPPER: new_ground = RAIL_GROUND_FENCE_HORIZ1; break;
			case TRACK_BIT_LOWER: new_ground = RAIL_GROUND_FENCE_HORIZ2; break;
			case TRACK_BIT_LEFT:  new_ground = RAIL_GROUND_FENCE_VERT1;  break;
			case TRACK_BIT_RIGHT: new_ground = RAIL_GROUND_FENCE_VERT2;  break;

			default: {
				PlayerID owner = GetTileOwner(tile);

				if (rail == (TRACK_BIT_LOWER | TRACK_BIT_RIGHT) || (
							(rail & TRACK_BIT_3WAY_NW) == 0 &&
							(rail & TRACK_BIT_X)
						)) {
					TileIndex n = tile + TileDiffXY(0, -1);
					TrackBits nrail = GetTrackBits(n);

					if (!IsTileType(n, MP_RAILWAY) ||
							!IsTileOwner(n, owner) ||
							nrail == TRACK_BIT_UPPER ||
							nrail == TRACK_BIT_LEFT) {
						new_ground = RAIL_GROUND_FENCE_NW;
					}
				}

				if (rail == (TRACK_BIT_UPPER | TRACK_BIT_LEFT) || (
							(rail & TRACK_BIT_3WAY_SE) == 0 &&
							(rail & TRACK_BIT_X)
						)) {
					TileIndex n = tile + TileDiffXY(0, 1);
					TrackBits nrail = GetTrackBits(n);

					if (!IsTileType(n, MP_RAILWAY) ||
							!IsTileOwner(n, owner) ||
							nrail == TRACK_BIT_LOWER ||
							nrail == TRACK_BIT_RIGHT) {
						new_ground = (new_ground == RAIL_GROUND_FENCE_NW) ?
							RAIL_GROUND_FENCE_SENW : RAIL_GROUND_FENCE_SE;
					}
				}

				if (rail == (TRACK_BIT_LOWER | TRACK_BIT_LEFT) || (
							(rail & TRACK_BIT_3WAY_NE) == 0 &&
							(rail & TRACK_BIT_Y)
						)) {
					TileIndex n = tile + TileDiffXY(-1, 0);
					TrackBits nrail = GetTrackBits(n);

					if (!IsTileType(n, MP_RAILWAY) ||
							!IsTileOwner(n, owner) ||
							nrail == TRACK_BIT_UPPER ||
							nrail == TRACK_BIT_RIGHT) {
						new_ground = RAIL_GROUND_FENCE_NE;
					}
				}

				if (rail == (TRACK_BIT_UPPER | TRACK_BIT_RIGHT) || (
							(rail & TRACK_BIT_3WAY_SW) == 0 &&
							(rail & TRACK_BIT_Y)
						)) {
					TileIndex n = tile + TileDiffXY(1, 0);
					TrackBits nrail = GetTrackBits(n);

					if (!IsTileType(n, MP_RAILWAY) ||
							!IsTileOwner(n, owner) ||
							nrail == TRACK_BIT_LOWER ||
							nrail == TRACK_BIT_LEFT) {
						new_ground = (new_ground == RAIL_GROUND_FENCE_NE) ?
							RAIL_GROUND_FENCE_NESW : RAIL_GROUND_FENCE_SW;
					}
				}
				break;
			}
		}
	}

set_ground:
	if (old_ground != new_ground) {
		SetRailGroundType(tile, new_ground);
		MarkTileDirtyByTile(tile);
	}
}


static TrackStatus GetTileTrackStatus_Track(TileIndex tile, TransportType mode, uint sub_mode, DiagDirection side)
{
	if (mode != TRANSPORT_RAIL) return 0;

	TrackBits trackbits = TRACK_BIT_NONE;
	TrackdirBits red_signals = TRACKDIR_BIT_NONE;

	switch (GetRailTileType(tile)) {
		default: NOT_REACHED();
		case RAIL_TILE_NORMAL:
			trackbits = GetTrackBits(tile);
			break;

		case RAIL_TILE_SIGNALS: {
			trackbits = GetTrackBits(tile);
			byte a = GetPresentSignals(tile);
			uint b = GetSignalStates(tile);

			b &= a;

			/* When signals are not present (in neither
			 * direction), we pretend them to be green. (So if
			 * signals are only one way, the other way will
			 * implicitely become `red' */
			if ((a & 0xC) == 0) b |= 0xC;
			if ((a & 0x3) == 0) b |= 0x3;

			if ((b & 0x8) == 0) red_signals |= (TRACKDIR_BIT_LEFT_N | TRACKDIR_BIT_X_NE | TRACKDIR_BIT_Y_SE | TRACKDIR_BIT_UPPER_E);
			if ((b & 0x4) == 0) red_signals |= (TRACKDIR_BIT_LEFT_S | TRACKDIR_BIT_X_SW | TRACKDIR_BIT_Y_NW | TRACKDIR_BIT_UPPER_W);
			if ((b & 0x2) == 0) red_signals |= (TRACKDIR_BIT_RIGHT_N | TRACKDIR_BIT_LOWER_E);
			if ((b & 0x1) == 0) red_signals |= (TRACKDIR_BIT_RIGHT_S | TRACKDIR_BIT_LOWER_W);

			break;
		}

		case RAIL_TILE_DEPOT: {
			DiagDirection dir = GetRailDepotDirection(tile);

			if (side != INVALID_DIAGDIR && side != dir) break;

			trackbits = AxisToTrackBits(DiagDirToAxis(dir));
			break;
		}

		case RAIL_TILE_WAYPOINT:
			trackbits = GetRailWaypointBits(tile);
			break;
	}

	return CombineTrackStatus(TrackBitsToTrackdirBits(trackbits), red_signals);
}

static void ClickTile_Track(TileIndex tile)
{
	switch (GetRailTileType(tile)) {
		case RAIL_TILE_DEPOT:    ShowDepotWindow(tile, VEH_TRAIN);                  break;
		case RAIL_TILE_WAYPOINT: ShowRenameWaypointWindow(GetWaypointByTile(tile)); break;
		default: break;
	}
}

static void GetTileDesc_Track(TileIndex tile, TileDesc *td)
{
	td->owner = GetTileOwner(tile);
	switch (GetRailTileType(tile)) {
		case RAIL_TILE_NORMAL:
			td->str = STR_1021_RAILROAD_TRACK;
			break;

		case RAIL_TILE_SIGNALS: {
			const StringID signal_type[4][4] = {
				{
					STR_RAILROAD_TRACK_WITH_NORMAL_SIGNALS,
					STR_RAILROAD_TRACK_WITH_NORMAL_PRESIGNALS,
					STR_RAILROAD_TRACK_WITH_NORMAL_EXITSIGNALS,
					STR_RAILROAD_TRACK_WITH_NORMAL_COMBOSIGNALS
				},
				{
					STR_RAILROAD_TRACK_WITH_NORMAL_PRESIGNALS,
					STR_RAILROAD_TRACK_WITH_PRESIGNALS,
					STR_RAILROAD_TRACK_WITH_PRE_EXITSIGNALS,
					STR_RAILROAD_TRACK_WITH_PRE_COMBOSIGNALS
				},
				{
					STR_RAILROAD_TRACK_WITH_NORMAL_EXITSIGNALS,
					STR_RAILROAD_TRACK_WITH_PRE_EXITSIGNALS,
					STR_RAILROAD_TRACK_WITH_EXITSIGNALS,
					STR_RAILROAD_TRACK_WITH_EXIT_COMBOSIGNALS
				},
				{
					STR_RAILROAD_TRACK_WITH_NORMAL_COMBOSIGNALS,
					STR_RAILROAD_TRACK_WITH_PRE_COMBOSIGNALS,
					STR_RAILROAD_TRACK_WITH_EXIT_COMBOSIGNALS,
					STR_RAILROAD_TRACK_WITH_COMBOSIGNALS
				}
			};

			td->str = signal_type[GetSignalType(tile, TRACK_UPPER)][GetSignalType(tile, TRACK_LOWER)];
			break;
		}

		case RAIL_TILE_DEPOT:
			td->str = STR_1023_RAILROAD_TRAIN_DEPOT;
			break;

		case RAIL_TILE_WAYPOINT:
		default:
			td->str = STR_LANDINFO_WAYPOINT;
			break;
	}
}

static void ChangeTileOwner_Track(TileIndex tile, PlayerID old_player, PlayerID new_player)
{
	if (!IsTileOwner(tile, old_player)) return;

	if (new_player != PLAYER_SPECTATOR) {
		SetTileOwner(tile, new_player);
	} else {
		DoCommand(tile, 0, 0, DC_EXEC | DC_BANKRUPT, CMD_LANDSCAPE_CLEAR);
	}
}

static const byte _fractcoords_behind[4] = { 0x8F, 0x8, 0x80, 0xF8 };
static const byte _fractcoords_enter[4] = { 0x8A, 0x48, 0x84, 0xA8 };
static const signed char _deltacoord_leaveoffset[8] = {
	-1,  0,  1,  0, /* x */
	 0,  1,  0, -1  /* y */
};


/** Compute number of ticks when next wagon will leave a depot.
 * Negative means next wagon should have left depot n ticks before.
 * @param v vehicle outside (leaving) the depot
 * @return number of ticks when the next wagon will leave
 */
int TicksToLeaveDepot(const Vehicle *v)
{
	DiagDirection dir = GetRailDepotDirection(v->tile);
	int length = v->u.rail.cached_veh_length;

	switch (dir) {
		case DIAGDIR_NE: return  ((int)(v->x_pos & 0x0F) - ((_fractcoords_enter[dir] & 0x0F) - (length + 1)));
		case DIAGDIR_SE: return -((int)(v->y_pos & 0x0F) - ((_fractcoords_enter[dir] >> 4)   + (length + 1)));
		case DIAGDIR_SW: return -((int)(v->x_pos & 0x0F) - ((_fractcoords_enter[dir] & 0x0F) + (length + 1)));
		default:
		case DIAGDIR_NW: return  ((int)(v->y_pos & 0x0F) - ((_fractcoords_enter[dir] >> 4)   - (length + 1)));
	}

	return 0; // make compilers happy
}


static VehicleEnterTileStatus VehicleEnter_Track(Vehicle *v, TileIndex tile, int x, int y)
{
	byte fract_coord;
	byte fract_coord_leave;
	DiagDirection dir;
	int length;

	/* this routine applies only to trains in depot tiles */
	if (v->type != VEH_TRAIN || !IsTileDepotType(tile, TRANSPORT_RAIL)) return VETSB_CONTINUE;

	/* depot direction */
	dir = GetRailDepotDirection(tile);

	/* calculate the point where the following wagon should be activated */
	/* this depends on the length of the current vehicle */
	length = v->u.rail.cached_veh_length;

	fract_coord_leave =
		((_fractcoords_enter[dir] & 0x0F) + // x
			(length + 1) * _deltacoord_leaveoffset[dir]) +
		(((_fractcoords_enter[dir] >> 4) +  // y
			((length + 1) * _deltacoord_leaveoffset[dir+4])) << 4);

	fract_coord = (x & 0xF) + ((y & 0xF) << 4);

	if (_fractcoords_behind[dir] == fract_coord) {
		/* make sure a train is not entering the tile from behind */
		return VETSB_CANNOT_ENTER;
	} else if (_fractcoords_enter[dir] == fract_coord) {
		if (DiagDirToDir(ReverseDiagDir(dir)) == v->direction) {
			/* enter the depot */
			v->u.rail.track = TRACK_BIT_DEPOT,
			v->vehstatus |= VS_HIDDEN; /* hide it */
			v->direction = ReverseDir(v->direction);
			if (v->Next() == NULL) VehicleEnterDepot(v);
			v->tile = tile;

			InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
			return VETSB_ENTERED_WORMHOLE;
		}
	} else if (fract_coord_leave == fract_coord) {
		if (DiagDirToDir(dir) == v->direction) {
			/* leave the depot? */
			if ((v = v->Next()) != NULL) {
				v->vehstatus &= ~VS_HIDDEN;
				v->u.rail.track = (DiagDirToAxis(dir) == AXIS_X ? TRACK_BIT_X : TRACK_BIT_Y);
			}
		}
	}

	return VETSB_CONTINUE;
}

/**
 * Tests if autoslope is allowed.
 *
 * @param tile The tile.
 * @param flags Terraform command flags.
 * @param z_old Old TileZ.
 * @param tileh_old Old TileSlope.
 * @param z_new New TileZ.
 * @param tileh_new New TileSlope.
 * @param rail_bits Trackbits.
 */
static CommandCost TestAutoslopeOnRailTile(TileIndex tile, uint flags, uint z_old, Slope tileh_old, uint z_new, Slope tileh_new, TrackBits rail_bits)
{
	if (!_patches.build_on_slopes || !AutoslopeEnabled()) return CMD_ERROR;

	/* Is the slope-rail_bits combination valid in general? I.e. is it save to call GetRailFoundation() ? */
	if (CmdFailed(CheckRailSlope(tileh_new, rail_bits, TRACK_BIT_NONE, tile))) return CMD_ERROR;

	/* Get the slopes on top of the foundations */
	z_old += ApplyFoundationToSlope(GetRailFoundation(tileh_old, rail_bits), &tileh_old);
	z_new += ApplyFoundationToSlope(GetRailFoundation(tileh_new, rail_bits), &tileh_new);

	Corner track_corner;
	switch (rail_bits) {
		case TRACK_BIT_LEFT:  track_corner = CORNER_W; break;
		case TRACK_BIT_LOWER: track_corner = CORNER_S; break;
		case TRACK_BIT_RIGHT: track_corner = CORNER_E; break;
		case TRACK_BIT_UPPER: track_corner = CORNER_N; break;

		/* Surface slope must not be changed */
		default: return (((z_old != z_new) || (tileh_old != tileh_new)) ? CMD_ERROR : CommandCost(EXPENSES_CONSTRUCTION, _price.terraform));
	}

	/* The height of the track_corner must not be changed. The rest ensures GetRailFoundation() already. */
	z_old += GetSlopeZInCorner(RemoveHalftileSlope(tileh_old), track_corner);
	z_new += GetSlopeZInCorner(RemoveHalftileSlope(tileh_new), track_corner);
	if (z_old != z_new) return CMD_ERROR;

	CommandCost cost = CommandCost(EXPENSES_CONSTRUCTION, _price.terraform);
	/* Make the ground dirty, if surface slope has changed */
	if (tileh_old != tileh_new) {
		/* If there is flat water on the lower halftile add the cost for clearing it */
		if (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh_old)) cost.AddCost(_price.clear_water);
		if ((flags & DC_EXEC) != 0) SetRailGroundType(tile, RAIL_GROUND_BARREN);
	}
	return  cost;
}

static CommandCost TerraformTile_Track(TileIndex tile, uint32 flags, uint z_new, Slope tileh_new)
{
	uint z_old;
	Slope tileh_old = GetTileSlope(tile, &z_old);
	if (IsPlainRailTile(tile)) {
		TrackBits rail_bits = GetTrackBits(tile);
		/* Is there flat water on the lower halftile, that must be cleared expensively? */
		bool was_water = (GetRailGroundType(tile) == RAIL_GROUND_WATER && IsSlopeWithOneCornerRaised(tileh_old));

		_error_message = STR_1008_MUST_REMOVE_RAILROAD_TRACK;

		/* First test autoslope. However if it succeeds we still have to test the rest, because non-autoslope terraforming is cheaper. */
		CommandCost autoslope_result = TestAutoslopeOnRailTile(tile, flags, z_old, tileh_old, z_new, tileh_new, rail_bits);

		/* When there is only a single horizontal/vertical track, one corner can be terraformed. */
		Corner allowed_corner;
		switch (rail_bits) {
			case TRACK_BIT_RIGHT: allowed_corner = CORNER_W; break;
			case TRACK_BIT_UPPER: allowed_corner = CORNER_S; break;
			case TRACK_BIT_LEFT:  allowed_corner = CORNER_E; break;
			case TRACK_BIT_LOWER: allowed_corner = CORNER_N; break;
			default: return autoslope_result;
		}

		Foundation f_old = GetRailFoundation(tileh_old, rail_bits);

		/* Do not allow terraforming if allowed_corner is part of anti-zig-zag foundations */
		if (tileh_old != SLOPE_NS && tileh_old != SLOPE_EW && IsSpecialRailFoundation(f_old)) return autoslope_result;

		/* Everything is valid, which only changes allowed_corner */
		for (Corner corner = (Corner)0; corner < CORNER_END; corner = (Corner)(corner + 1)) {
			if (allowed_corner == corner) continue;
			if (z_old + GetSlopeZInCorner(tileh_old, corner) != z_new + GetSlopeZInCorner(tileh_new, corner)) return autoslope_result;
		}

		/* Make the ground dirty */
		if ((flags & DC_EXEC) != 0) SetRailGroundType(tile, RAIL_GROUND_BARREN);

		/* allow terraforming */
		return CommandCost(EXPENSES_CONSTRUCTION, was_water ? _price.clear_water : (Money)0);
	} else {
		if (_patches.build_on_slopes && AutoslopeEnabled()) {
			switch (GetRailTileType(tile)) {
				case RAIL_TILE_WAYPOINT: {
					CommandCost cost = TestAutoslopeOnRailTile(tile, flags, z_old, tileh_old, z_new, tileh_new, GetRailWaypointBits(tile));
					if (!CmdFailed(cost)) return cost; // allow autoslope
					break;
				}

				case RAIL_TILE_DEPOT:
					if (AutoslopeCheckForEntranceEdge(tile, z_new, tileh_new, GetRailDepotDirection(tile))) return CommandCost(EXPENSES_CONSTRUCTION, _price.terraform);
					break;

				default: NOT_REACHED();
			}
		}
	}
	return DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
}


extern const TileTypeProcs _tile_type_rail_procs = {
	DrawTile_Track,           /* draw_tile_proc */
	GetSlopeZ_Track,          /* get_slope_z_proc */
	ClearTile_Track,          /* clear_tile_proc */
	GetAcceptedCargo_Track,   /* get_accepted_cargo_proc */
	GetTileDesc_Track,        /* get_tile_desc_proc */
	GetTileTrackStatus_Track, /* get_tile_track_status_proc */
	ClickTile_Track,          /* click_tile_proc */
	AnimateTile_Track,        /* animate_tile_proc */
	TileLoop_Track,           /* tile_loop_clear */
	ChangeTileOwner_Track,    /* change_tile_owner_clear */
	NULL,                     /* get_produced_cargo_proc */
	VehicleEnter_Track,       /* vehicle_enter_tile_proc */
	GetFoundation_Track,      /* get_foundation_proc */
	TerraformTile_Track,      /* terraform_tile_proc */
};