summaryrefslogtreecommitdiff
path: root/src/newgrf_house.cpp
blob: 5f318cf96b67b9db0af865f2974af77bfadfa335 (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
/* $Id$ */

/** @file newgrf_house.cpp Implementation of NewGRF houses. */

#include "stdafx.h"
#include "openttd.h"
#include "variables.h"
#include "debug.h"
#include "viewport_func.h"
#include "landscape.h"
#include "town_map.h"
#include "sprite.h"
#include "newgrf.h"
#include "newgrf_house.h"
#include "newgrf_spritegroup.h"
#include "newgrf_town.h"
#include "newgrf_sound.h"
#include "newgrf_commons.h"
#include "transparency.h"
#include "functions.h"
#include "company_func.h"
#include "animated_tile_func.h"
#include "company_base.h"

static BuildingCounts    _building_counts;
static HouseClassMapping _class_mapping[HOUSE_CLASS_MAX];

HouseOverrideManager _house_mngr(NEW_HOUSE_OFFSET, HOUSE_MAX, INVALID_HOUSE_ID);

HouseClassID AllocateHouseClassID(byte grf_class_id, uint32 grfid)
{
	/* Start from 1 because 0 means that no class has been assigned. */
	for (int i = 1; i != lengthof(_class_mapping); i++) {
		HouseClassMapping *map = &_class_mapping[i];

		if (map->class_id == grf_class_id && map->grfid == grfid) return (HouseClassID)i;

		if (map->class_id == 0 && map->grfid == 0) {
			map->class_id = grf_class_id;
			map->grfid    = grfid;
			return (HouseClassID)i;
		}
	}
	return HOUSE_NO_CLASS;
}

void InitializeBuildingCounts()
{
	memset(&_building_counts, 0, sizeof(_building_counts));
}

/**
 * IncreaseBuildingCount()
 * Increase the count of a building when it has been added by a town.
 * @param t The town that the building is being built in
 * @param house_id The id of the house being added
 */
void IncreaseBuildingCount(Town *t, HouseID house_id)
{
	HouseClassID class_id = GetHouseSpecs(house_id)->class_id;

	if (!_loaded_newgrf_features.has_newhouses) return;

	/* If there are 255 buildings of this type in this town, there are also
	 * at least that many houses of the same class in the town, and
	 * therefore on the map as well. */
	if (t->building_counts.id_count[house_id] == 255) return;

	t->building_counts.id_count[house_id]++;
	if (_building_counts.id_count[house_id] < 255) _building_counts.id_count[house_id]++;

	/* Similarly, if there are 255 houses of this class in this town, there
	 * must be at least that number on the map too. */
	if (class_id == HOUSE_NO_CLASS || t->building_counts.class_count[class_id] == 255) return;

	t->building_counts.class_count[class_id]++;
	if (_building_counts.class_count[class_id] < 255) _building_counts.class_count[class_id]++;
}

/**
 * DecreaseBuildingCount()
 * Decrease the number of a building when it is deleted.
 * @param t The town that the building was built in
 * @param house_id The id of the house being removed
 */
void DecreaseBuildingCount(Town *t, HouseID house_id)
{
	HouseClassID class_id = GetHouseSpecs(house_id)->class_id;

	if (!_loaded_newgrf_features.has_newhouses) return;

	if (t->building_counts.id_count[house_id] > 0) t->building_counts.id_count[house_id]--;
	if (_building_counts.id_count[house_id] > 0)   _building_counts.id_count[house_id]--;

	if (class_id == HOUSE_NO_CLASS) return;

	if (t->building_counts.class_count[class_id] > 0) t->building_counts.class_count[class_id]--;
	if (_building_counts.class_count[class_id] > 0)   _building_counts.class_count[class_id]--;
}

static uint32 HouseGetRandomBits(const ResolverObject *object)
{
	const TileIndex tile = object->u.house.tile;
	return (tile == INVALID_TILE || !IsTileType(tile, MP_HOUSE)) ? 0 : GetHouseRandomBits(tile);
}

static uint32 HouseGetTriggers(const ResolverObject *object)
{
	const TileIndex tile = object->u.house.tile;
	return (tile == INVALID_TILE || !IsTileType(tile, MP_HOUSE)) ? 0 : GetHouseTriggers(tile);
}

static void HouseSetTriggers(const ResolverObject *object, int triggers)
{
	const TileIndex tile = object->u.house.tile;
	if (IsTileType(tile, MP_HOUSE)) SetHouseTriggers(tile, triggers);
}

static uint32 GetNumHouses(HouseID house_id, const Town *town)
{
	uint8 map_id_count, town_id_count, map_class_count, town_class_count;
	HouseClassID class_id = GetHouseSpecs(house_id)->class_id;

	map_id_count     = _building_counts.id_count[house_id];
	map_class_count  = _building_counts.class_count[class_id];
	town_id_count    = town->building_counts.id_count[house_id];
	town_class_count = town->building_counts.class_count[class_id];

	return map_class_count << 24 | town_class_count << 16 | map_id_count << 8 | town_id_count;
}

uint32 GetNearbyTileInformation(byte parameter, TileIndex tile)
{
	tile = GetNearbyTile(parameter, tile);
	return GetNearbyTileInformation(tile);
}

/** Structure with user-data for SearchNearbyHouseXXX - functions */
typedef struct {
	const HouseSpec *hs;  ///< Specs of the house, that startet the search
	TileIndex north_tile; ///< Northern tile of the house.
} SearchNearbyHouseData;

/** Callback function to search a house by its HouseID
 * @param tile TileIndex to be examined
 * @param user_data SearchNearbyHouseData
 * @return true or false, if found or not
 */
static bool SearchNearbyHouseID(TileIndex tile, void *user_data)
{
	if (IsTileType(tile, MP_HOUSE)) {
		HouseID house = GetHouseType(tile); // tile been examined
		const HouseSpec *hs = GetHouseSpecs(house);
		if (hs->grffile != NULL) { // must be one from a grf file
			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;

			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
			if (north_tile == nbhd->north_tile) return false; // Always ignore origin house

			return hs->local_id == nbhd->hs->local_id &&  // same local id as the one requested
				hs->grffile->grfid == nbhd->hs->grffile->grfid;  // from the same grf
		}
	}
	return false;
}

/** Callback function to search a house by its classID
 * @param tile TileIndex to be examined
 * @param user_data SearchNearbyHouseData
 * @return true or false, if found or not
 */
static bool SearchNearbyHouseClass(TileIndex tile, void *user_data)
{
	if (IsTileType(tile, MP_HOUSE)) {
		HouseID house = GetHouseType(tile); // tile been examined
		const HouseSpec *hs = GetHouseSpecs(house);
		if (hs->grffile != NULL) { // must be one from a grf file
			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;

			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
			if (north_tile == nbhd->north_tile) return false; // Always ignore origin house

			return hs->class_id == nbhd->hs->class_id &&  // same classid as the one requested
				hs->grffile->grfid == nbhd->hs->grffile->grfid;  // from the same grf
		}
	}
	return false;
}

/** Callback function to search a house by its grfID
 * @param tile TileIndex to be examined
 * @param user_data SearchNearbyHouseData
 * @return true or false, if found or not
 */
static bool SearchNearbyHouseGRFID(TileIndex tile, void *user_data)
{
	if (IsTileType(tile, MP_HOUSE)) {
		HouseID house = GetHouseType(tile); // tile been examined
		const HouseSpec *hs = GetHouseSpecs(house);
		if (hs->grffile != NULL) { // must be one from a grf file
			SearchNearbyHouseData *nbhd = (SearchNearbyHouseData *)user_data;

			TileIndex north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!
			if (north_tile == nbhd->north_tile) return false; // Always ignore origin house

			return hs->grffile->grfid == nbhd->hs->grffile->grfid;  // from the same grf
		}
	}
	return false;
}

/** This function will activate a search around a central tile, looking for some houses
 * that fit the requested characteristics
 * @param parameter that is given by the callback.
 *                  bits 0..6 radius of the search
 *                  bits 7..8 search type i.e.: 0 = houseID/ 1 = classID/ 2 = grfID
 * @param tile TileIndex from which to start the search
 * @param house the HouseID that is associated to the house, the callback is called for
 * @return the Manhattan distance from the center tile, if any, and 0 if failure
 */
static uint32 GetDistanceFromNearbyHouse(uint8 parameter, TileIndex tile, HouseID house)
{
	static TestTileOnSearchProc * const search_procs[3] = {
		SearchNearbyHouseID,
		SearchNearbyHouseClass,
		SearchNearbyHouseGRFID,
	};
	TileIndex found_tile = tile;
	uint8 searchtype = GB(parameter, 6, 2);
	uint8 searchradius = GB(parameter, 0, 6);
	if (searchtype >= lengthof(search_procs)) return 0;  // do not run on ill-defined code
	if (searchradius < 1) return 0; // do not use a too low radius

	SearchNearbyHouseData nbhd;
	nbhd.hs = GetHouseSpecs(house);
	nbhd.north_tile = tile + GetHouseNorthPart(house); // modifies 'house'!

	/* Use a pointer for the tile to start the search. Will be required for calculating the distance*/
	if (CircularTileSearch(&found_tile, 2 * searchradius + 1, search_procs[searchtype], &nbhd)) {
		return DistanceManhattan(found_tile, tile);
	}
	return 0;
}

/**
 * HouseGetVariable():
 *
 * Used by the resolver to get values for feature 07 deterministic spritegroups.
 */
static uint32 HouseGetVariable(const ResolverObject *object, byte variable, byte parameter, bool *available)
{
	const Town *town = object->u.house.town;
	TileIndex tile   = object->u.house.tile;
	HouseID house_id = object->u.house.house_id;

	if (object->scope == VSG_SCOPE_PARENT) {
		return TownGetVariable(variable, parameter, available, town);
	}

	switch (variable) {
		/* Construction stage. */
		case 0x40: return (IsTileType(tile, MP_HOUSE) ? GetHouseBuildingStage(tile) : 0) | TileHash2Bit(TileX(tile), TileY(tile)) << 2;

		/* Building age. */
		case 0x41: return GetHouseAge(tile);

		/* Town zone */
		case 0x42: return GetTownRadiusGroup(town, tile);

		/* Terrain type */
		case 0x43: return GetTerrainType(tile);

		/* Number of this type of building on the map. */
		case 0x44: return GetNumHouses(house_id, town);

		/* Whether the town is being created or just expanded. */
		case 0x45: return _generating_world ? 1 : 0;

		/* Current animation frame. */
		case 0x46: return IsTileType(tile, MP_HOUSE) ? GetHouseAnimationFrame(tile) : 0;

		/* Position of the house */
		case 0x47: return TileY(tile) << 16 | TileX(tile);

		/* Building counts for old houses with id = parameter. */
		case 0x60: return GetNumHouses(parameter, town);

		/* Building counts for new houses with id = parameter. */
		case 0x61: {
			const HouseSpec *hs = GetHouseSpecs(house_id);
			if (hs->grffile == NULL) return 0;

			HouseID new_house = _house_mngr.GetID(parameter, hs->grffile->grfid);
			return new_house == INVALID_HOUSE_ID ? 0 : GetNumHouses(new_house, town);
		}

		/* Land info for nearby tiles. */
		case 0x62: return GetNearbyTileInformation(parameter, tile);

		/* Current animation frame of nearby house tiles */
		case 0x63: {
			TileIndex testtile = GetNearbyTile(parameter, tile);
			return IsTileType(testtile, MP_HOUSE) ? GetHouseAnimationFrame(testtile) : 0;
		}

		/* Cargo acceptance history of nearby stations */
		/*case 0x64: not implemented yet */

		/* Distance test for some house types */
		case 0x65: return GetDistanceFromNearbyHouse(parameter, tile, object->u.house.house_id);
	}

	DEBUG(grf, 1, "Unhandled house property 0x%X", variable);

	*available = false;
	return UINT_MAX;
}

static const SpriteGroup *HouseResolveReal(const ResolverObject *object, const SpriteGroup *group)
{
	/* Houses do not have 'real' groups */
	return NULL;
}

/**
 * NewHouseResolver():
 *
 * Returns a resolver object to be used with feature 07 spritegroups.
 */
static void NewHouseResolver(ResolverObject *res, HouseID house_id, TileIndex tile, Town *town)
{
	res->GetRandomBits = HouseGetRandomBits;
	res->GetTriggers   = HouseGetTriggers;
	res->SetTriggers   = HouseSetTriggers;
	res->GetVariable   = HouseGetVariable;
	res->ResolveReal   = HouseResolveReal;

	res->u.house.tile     = tile;
	res->u.house.town     = town;
	res->u.house.house_id = house_id;

	res->callback        = CBID_NO_CALLBACK;
	res->callback_param1 = 0;
	res->callback_param2 = 0;
	res->last_value      = 0;
	res->trigger         = 0;
	res->reseed          = 0;
	res->count           = 0;

	const HouseSpec *hs = GetHouseSpecs(house_id);
	res->grffile         = (hs != NULL ? hs->grffile : NULL);
}

uint16 GetHouseCallback(CallbackID callback, uint32 param1, uint32 param2, HouseID house_id, Town *town, TileIndex tile)
{
	ResolverObject object;
	const SpriteGroup *group;

	NewHouseResolver(&object, house_id, tile, town);
	object.callback = callback;
	object.callback_param1 = param1;
	object.callback_param2 = param2;

	group = Resolve(GetHouseSpecs(house_id)->spritegroup, &object);
	if (group == NULL || group->type != SGT_CALLBACK) return CALLBACK_FAILED;

	return group->g.callback.result;
}

static void DrawTileLayout(const TileInfo *ti, const SpriteGroup *group, byte stage, HouseID house_id)
{
	const DrawTileSprites *dts = group->g.layout.dts;
	const DrawTileSeqStruct *dtss;

	const HouseSpec *hs = GetHouseSpecs(house_id);
	SpriteID palette = hs->random_colour[TileHash2Bit(ti->x, ti->y)] + PALETTE_RECOLOR_START;
	if (HasBit(hs->callback_mask, CBM_HOUSE_COLOUR)) {
		uint16 callback = GetHouseCallback(CBID_HOUSE_COLOUR, 0, 0, house_id, GetTownByTile(ti->tile), ti->tile);
		if (callback != CALLBACK_FAILED) {
			/* If bit 14 is set, we should use a 2cc colour map, else use the callback value. */
			palette = HasBit(callback, 14) ? GB(callback, 0, 8) + SPR_2CCMAP_BASE : callback;
		}
	}

	SpriteID image = dts->ground.sprite;
	SpriteID pal   = dts->ground.pal;

	if (IS_CUSTOM_SPRITE(image)) image += stage;

	if (GB(image, 0, SPRITE_WIDTH) != 0) {
		DrawGroundSprite(image, GroundSpritePaletteTransform(image, pal, palette));
	}

	foreach_draw_tile_seq(dtss, dts->seq) {
		if (GB(dtss->image.sprite, 0, SPRITE_WIDTH) == 0) continue;

		image = dtss->image.sprite;
		pal   = dtss->image.pal;

		/* Stop drawing sprite sequence once we meet a sprite that doesn't have to be opaque */
		if (IsInvisibilitySet(TO_HOUSES) && !HasBit(image, SPRITE_MODIFIER_OPAQUE)) return;

		if (IS_CUSTOM_SPRITE(image)) image += stage;

		pal = SpriteLayoutPaletteTransform(image, pal, palette);

		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_HOUSES)
			);
		} else {
			/* For industries and houses delta_x and delta_y are unsigned */
			AddChildSpriteScreen(image, pal, (byte)dtss->delta_x, (byte)dtss->delta_y, !HasBit(image, SPRITE_MODIFIER_OPAQUE) && IsTransparencySet(TO_HOUSES));
		}
	}
}

void DrawNewHouseTile(TileInfo *ti, HouseID house_id)
{
	const HouseSpec *hs = GetHouseSpecs(house_id);
	const SpriteGroup *group;
	ResolverObject object;

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

	NewHouseResolver(&object, house_id, ti->tile, GetTownByTile(ti->tile));

	group = Resolve(hs->spritegroup, &object);
	if (group == NULL || group->type != SGT_TILELAYOUT) {
		/* XXX: This is for debugging purposes really, and shouldn't stay. */
		DrawGroundSprite(SPR_SHADOW_CELL, PAL_NONE);
	} else {
		/* Limit the building stage to the number of stages supplied. */
		byte stage = GetHouseBuildingStage(ti->tile);
		stage = Clamp(stage - 4 + group->g.layout.num_sprites, 0, group->g.layout.num_sprites - 1);
		DrawTileLayout(ti, group, stage, house_id);
	}
}

void AnimateNewHouseTile(TileIndex tile)
{
	const HouseSpec *hs = GetHouseSpecs(GetHouseType(tile));
	byte animation_speed = hs->animation_speed;
	bool frame_set_by_callback = false;

	if (HasBit(hs->callback_mask, CBM_HOUSE_ANIMATION_SPEED)) {
		uint16 callback_res = GetHouseCallback(CBID_HOUSE_ANIMATION_SPEED, 0, 0, GetHouseType(tile), GetTownByTile(tile), tile);
		if (callback_res != CALLBACK_FAILED) animation_speed = Clamp(callback_res & 0xFF, 2, 16);
	}

	/* An animation speed of 2 means the animation frame changes 4 ticks, and
	 * increasing this value by one doubles the wait. 2 is the minimum value
	 * allowed for animation_speed, which corresponds to 120ms, and 16 is the
	 * maximum, corresponding to around 33 minutes. */
	if (_tick_counter % (1 << animation_speed) != 0) return;

	byte frame      = GetHouseAnimationFrame(tile);
	byte num_frames = GB(hs->animation_frames, 0, 7);

	if (HasBit(hs->callback_mask, CBM_HOUSE_ANIMATION_NEXT_FRAME)) {
		uint32 param = (hs->extra_flags & CALLBACK_1A_RANDOM_BITS) ? Random() : 0;
		uint16 callback_res = GetHouseCallback(CBID_HOUSE_ANIMATION_NEXT_FRAME, param, 0, GetHouseType(tile), GetTownByTile(tile), tile);

		if (callback_res != CALLBACK_FAILED) {
			frame_set_by_callback = true;

			switch (callback_res & 0xFF) {
				case 0xFF:
					DeleteAnimatedTile(tile);
					break;
				case 0xFE:
					/* Carry on as normal. */
					frame_set_by_callback = false;
					break;
				default:
					frame = callback_res & 0xFF;
					break;
			}

			/* If the lower 7 bits of the upper byte of the callback
			 * result are not empty, it is a sound effect. */
			if (GB(callback_res, 8, 7) != 0) PlayTileSound(hs->grffile, GB(callback_res, 8, 7), tile);
		}
	}

	if (!frame_set_by_callback) {
		if (frame < num_frames) {
			frame++;
		} else if (frame == num_frames && HasBit(hs->animation_frames, 7)) {
			/* This animation loops, so start again from the beginning */
			frame = 0;
		} else {
			/* This animation doesn't loop, so stay here */
			DeleteAnimatedTile(tile);
		}
	}

	SetHouseAnimationFrame(tile, frame);
	MarkTileDirtyByTile(tile);
}

void ChangeHouseAnimationFrame(const GRFFile *file, TileIndex tile, uint16 callback_result)
{
	switch (callback_result & 0xFF) {
		case 0xFD: /* Do nothing. */         break;
		case 0xFE: AddAnimatedTile(tile);    break;
		case 0xFF: DeleteAnimatedTile(tile); break;
		default:
			SetHouseAnimationFrame(tile, callback_result & 0xFF);
			AddAnimatedTile(tile);
			break;
	}
	/* If the lower 7 bits of the upper byte of the callback
	 * result are not empty, it is a sound effect. */
	if (GB(callback_result, 8, 7) != 0) PlayTileSound(file, GB(callback_result, 8, 7), tile);
}

bool CanDeleteHouse(TileIndex tile)
{
	const HouseSpec *hs = GetHouseSpecs(GetHouseType(tile));

	/* Humans are always allowed to remove buildings, as is water and
	 * anyone using the scenario editor. */
	if ((IsValidCompanyID(_current_company) && IsHumanCompany(_current_company))
			|| _current_company == OWNER_WATER || _current_company == OWNER_NONE) return true;

	if (HasBit(hs->callback_mask, CBM_HOUSE_DENY_DESTRUCTION)) {
		uint16 callback_res = GetHouseCallback(CBID_HOUSE_DENY_DESTRUCTION, 0, 0, GetHouseType(tile), GetTownByTile(tile), tile);
		return (callback_res == CALLBACK_FAILED || callback_res == 0);
	} else {
		return !(hs->extra_flags & BUILDING_IS_PROTECTED);
	}
}

static void AnimationControl(TileIndex tile, uint16 random_bits)
{
	const HouseSpec *hs = GetHouseSpecs(GetHouseType(tile));

	if (HasBit(hs->callback_mask, CBM_HOUSE_ANIMATION_START_STOP)) {
		uint32 param = (hs->extra_flags & SYNCHRONISED_CALLBACK_1B) ? (GB(Random(), 0, 16) | random_bits << 16) : Random();
		uint16 callback_res = GetHouseCallback(CBID_HOUSE_ANIMATION_START_STOP, param, 0, GetHouseType(tile), GetTownByTile(tile), tile);

		if (callback_res != CALLBACK_FAILED) ChangeHouseAnimationFrame(hs->grffile, tile, callback_res);
	}
}

bool NewHouseTileLoop(TileIndex tile)
{
	const HouseSpec *hs = GetHouseSpecs(GetHouseType(tile));

	if (GetHouseProcessingTime(tile) > 0) {
		DecHouseProcessingTime(tile);
		return true;
	}

	TriggerHouse(tile, HOUSE_TRIGGER_TILE_LOOP);
	TriggerHouse(tile, HOUSE_TRIGGER_TILE_LOOP_TOP);

	if (HasBit(hs->callback_mask, CBM_HOUSE_ANIMATION_START_STOP)) {
		/* If this house is marked as having a synchronised callback, all the
		 * tiles will have the callback called at once, rather than when the
		 * tile loop reaches them. This should only be enabled for the northern
		 * tile, or strange things will happen (here, and in TTDPatch). */
		if (hs->extra_flags & SYNCHRONISED_CALLBACK_1B) {
			uint16 random = GB(Random(), 0, 16);

			if (hs->building_flags & BUILDING_HAS_1_TILE)  AnimationControl(tile, random);
			if (hs->building_flags & BUILDING_2_TILES_Y)   AnimationControl(TILE_ADDXY(tile, 0, 1), random);
			if (hs->building_flags & BUILDING_2_TILES_X)   AnimationControl(TILE_ADDXY(tile, 1, 0), random);
			if (hs->building_flags & BUILDING_HAS_4_TILES) AnimationControl(TILE_ADDXY(tile, 1, 1), random);
		} else {
			AnimationControl(tile, 0);
		}
	}

	/* Check callback 21, which determines if a house should be destroyed. */
	if (HasBit(hs->callback_mask, CBM_HOUSE_DESTRUCTION)) {
		uint16 callback_res = GetHouseCallback(CBID_HOUSE_DESTRUCTION, 0, 0, GetHouseType(tile), GetTownByTile(tile), tile);
		if (callback_res != CALLBACK_FAILED && GB(callback_res, 0, 8) > 0) {
			ClearTownHouse(GetTownByTile(tile), tile);
			return false;
		}
	}

	SetHouseProcessingTime(tile, hs->processing_time);
	return true;
}

static void DoTriggerHouse(TileIndex tile, HouseTrigger trigger, byte base_random, bool first)
{
	ResolverObject object;

	/* We can't trigger a non-existent building... */
	assert(IsTileType(tile, MP_HOUSE));

	HouseID hid = GetHouseType(tile);
	HouseSpec *hs = GetHouseSpecs(hid);

	if (hs->spritegroup == NULL) return;

	NewHouseResolver(&object, hid, tile, GetTownByTile(tile));

	object.callback = CBID_RANDOM_TRIGGER;
	object.trigger = trigger;

	const SpriteGroup *group = Resolve(hs->spritegroup, &object);
	if (group == NULL) return;

	byte new_random_bits = Random();
	byte random_bits = GetHouseRandomBits(tile);
	random_bits &= ~object.reseed;
	random_bits |= (first ? new_random_bits : base_random) & object.reseed;
	SetHouseRandomBits(tile, random_bits);

	switch (trigger) {
		case HOUSE_TRIGGER_TILE_LOOP:
			/* Random value already set. */
			break;

		case HOUSE_TRIGGER_TILE_LOOP_TOP:
			if (!first) break;
			/* Random value of first tile already set. */
			if (hs->building_flags & BUILDING_2_TILES_Y)   DoTriggerHouse(TILE_ADDXY(tile, 0, 1), trigger, random_bits, false);
			if (hs->building_flags & BUILDING_2_TILES_X)   DoTriggerHouse(TILE_ADDXY(tile, 1, 0), trigger, random_bits, false);
			if (hs->building_flags & BUILDING_HAS_4_TILES) DoTriggerHouse(TILE_ADDXY(tile, 1, 1), trigger, random_bits, false);
			break;
	}
}

void TriggerHouse(TileIndex t, HouseTrigger trigger)
{
	DoTriggerHouse(t, trigger, 0, true);
}