path: root/engine.c

/* $Id$ */

#include "stdafx.h"
#include "openttd.h"
#include "debug.h"
#include "functions.h"
#include "string.h"
#include "strings.h"
#include "table/strings.h"
#include "engine.h"
#include "table/engines.h"
#include "gfx.h"
#include "player.h"
#include "command.h"
#include "vehicle.h"
#include "news.h"
#include "saveload.h"
#include "sprite.h"
#include "variables.h"

enum {
	ENGINE_AVAILABLE = 1,
	ENGINE_INTRODUCING = 2,
	ENGINE_PREVIEWING = 4,
};

/** TRANSLATE FROM LOCAL CARGO TO GLOBAL CARGO ID'S.
 * This maps the per-landscape cargo ID's to globally unique cargo ID's usable ie. in
 * the custom GRF  files. It is basically just a transcribed table from TTDPatch's newgrf.txt.
 */
const CargoID _global_cargo_id[NUM_LANDSCAPE][NUM_CARGO] = {
	/* LT_NORMAL */ {GC_PASSENGERS, GC_COAL,  GC_MAIL, GC_OIL, GC_LIVESTOCK, GC_GOODS, GC_GRAIN, GC_WOOD, GC_IRON_ORE,    GC_STEEL,  GC_VALUABLES, GC_PAPER_TEMP},
	/* LT_HILLY */  {GC_PASSENGERS, GC_COAL,  GC_MAIL, GC_OIL, GC_LIVESTOCK, GC_GOODS, GC_GRAIN, GC_WOOD, GC_INVALID,     GC_PAPER,  GC_VALUABLES, GC_FOOD },
	/* LT_DESERT */ {GC_PASSENGERS, GC_RUBBER,GC_MAIL, GC_OIL, GC_FRUIT,     GC_GOODS, GC_GRAIN, GC_WOOD, GC_COPPER_ORE,  GC_WATER,  GC_VALUABLES, GC_FOOD },
	/* LT_CANDY */  {GC_PASSENGERS, GC_SUGAR, GC_MAIL, GC_TOYS,GC_BATTERIES, GC_CANDY, GC_TOFFEE,GC_COLA, GC_COTTON_CANDY,GC_BUBBLES,GC_PLASTIC,   GC_FIZZY_DRINKS },
	/**
	 * - GC_INVALID (255) means that  cargo is not available for that climate
	 * - GC_PAPER_TEMP (27) is paper in  temperate climate in TTDPatch
	 * Following can  be renumbered:
	 * - GC_DEFAULT (29) is the defa ult cargo for the purpose of spritesets
	 * - GC_PURCHASE (30) is the purchase list image (the equivalent of 0xff) for the purpose of spritesets
	 */
};

/** BEGIN --- TRANSLATE FROM GLOBAL CARGO TO LOCAL CARGO ID'S **/
/** Map global cargo ID's to local-cargo ID's */
const CargoID _local_cargo_id_ctype[NUM_GLOBAL_CID] = {
	CT_PASSENGERS,CT_COAL,   CT_MAIL,        CT_OIL,      CT_LIVESTOCK,CT_GOODS,  CT_GRAIN,      CT_WOOD,         /*  0- 7 */
	CT_IRON_ORE,  CT_STEEL,  CT_VALUABLES,   CT_PAPER,    CT_FOOD,     CT_FRUIT,  CT_COPPER_ORE, CT_WATER,        /*  8-15 */
	CT_RUBBER,    CT_SUGAR,  CT_TOYS,        CT_BATTERIES,CT_CANDY,    CT_TOFFEE, CT_COLA,       CT_COTTON_CANDY, /* 16-23 */
	CT_BUBBLES,   CT_PLASTIC,CT_FIZZY_DRINKS,CT_PAPER     /* unsup. */,CT_HILLY_UNUSED,                           /* 24-28 */
	CT_INVALID,   CT_INVALID                                                                                      /* 29-30 */
};

#define MC(cargo) (1 << cargo)
/** Bitmasked value where the global cargo ID is available in landscape
 * 0: LT_NORMAL, 1: LT_HILLY, 2: LT_DESERT, 3: LT_CANDY */
const uint32 _landscape_global_cargo_mask[NUM_LANDSCAPE] =
{ /* LT_NORMAL: temperate */
	MC(GC_PASSENGERS)|MC(GC_COAL)|MC(GC_MAIL)|MC(GC_OIL)|MC(GC_LIVESTOCK)|MC(GC_GOODS)|MC(GC_GRAIN)|MC(GC_WOOD)|
	MC(GC_IRON_ORE)|MC(GC_STEEL)|MC(GC_VALUABLES)|MC(GC_FOOD)|MC(GC_UNDEFINED),
	/* LT_HILLY: arctic */
	MC(GC_PASSENGERS)|MC(GC_COAL)|MC(GC_MAIL)|MC(GC_OIL)|MC(GC_LIVESTOCK)|MC(GC_GOODS)|
	MC(GC_GRAIN)|MC(GC_WOOD)|MC(GC_VALUABLES)|MC(GC_PAPER)|MC(GC_FOOD)|MC(GC_UNDEFINED),
	/* LT_DESERT: rainforest/desert */
	MC(GC_PASSENGERS)|MC(GC_MAIL)|MC(GC_OIL)|MC(GC_GOODS)|MC(GC_GRAIN)|MC(GC_WOOD)|
	MC(GC_VALUABLES)|MC(GC_FOOD)|MC(GC_FRUIT)|MC(GC_COPPER_ORE)|MC(GC_WATER)|MC(GC_RUBBER),
	/* LT_CANDY: toyland */
	MC(GC_PASSENGERS)|MC(GC_MAIL)|MC(GC_SUGAR)|MC(GC_TOYS)|MC(GC_BATTERIES)|MC(GC_CANDY)|
	MC(GC_TOFFEE)|MC(GC_COLA)|MC(GC_COTTON_CANDY)|MC(GC_BUBBLES)|MC(GC_PLASTIC)|MC(GC_FIZZY_DRINKS)
};
/** END   --- TRANSLATE FROM GLOBAL CARGO TO LOCAL CARGO ID'S **/

/** Bitmasked values of what type of cargo is refittable for the given vehicle-type.
 * This coupled with the landscape information (_landscape_global_cargo_mask) gives
 * us exactly what is refittable and what is not */
const uint32 _default_refitmasks[NUM_VEHICLE_TYPES] = {
	/* Trains */
	MC(GC_PASSENGERS)|MC(GC_COAL)|MC(GC_MAIL)|MC(GC_LIVESTOCK)|MC(GC_GOODS)|MC(GC_GRAIN)|MC(GC_WOOD)|MC(GC_IRON_ORE)|
	MC(GC_STEEL)|MC(GC_VALUABLES)|MC(GC_PAPER)|MC(GC_FOOD)|MC(GC_FRUIT)|MC(GC_COPPER_ORE)|MC(GC_WATER)|MC(GC_SUGAR)|
	MC(GC_TOYS)|MC(GC_CANDY)|MC(GC_TOFFEE)|MC(GC_COLA)|MC(GC_COTTON_CANDY)|MC(GC_BUBBLES)|MC(GC_PLASTIC)|MC(GC_FIZZY_DRINKS),
	/* Road vehicles (not refittable by default) */
	0,
	/* Ships */
	MC(GC_COAL)|MC(GC_MAIL)|MC(GC_LIVESTOCK)|MC(GC_GOODS)|MC(GC_GRAIN)|MC(GC_WOOD)|MC(GC_IRON_ORE)|MC(GC_STEEL)|MC(GC_VALUABLES)|
	MC(GC_PAPER)|MC(GC_FOOD)|MC(GC_FRUIT)|MC(GC_COPPER_ORE)|MC(GC_WATER)|MC(GC_RUBBER)|MC(GC_SUGAR)|MC(GC_TOYS)|MC(GC_BATTERIES)|
	MC(GC_CANDY)|MC(GC_TOFFEE)|MC(GC_COLA)|MC(GC_COTTON_CANDY)|MC(GC_BUBBLES)|MC(GC_PLASTIC)|MC(GC_FIZZY_DRINKS),
	/* Aircraft */
	MC(GC_PASSENGERS)|MC(GC_MAIL)|MC(GC_GOODS)|MC(GC_VALUABLES)|MC(GC_FOOD)|MC(GC_FRUIT)|MC(GC_SUGAR)|MC(GC_TOYS)|
	MC(GC_BATTERIES)|MC(GC_CANDY)|MC(GC_TOFFEE)|MC(GC_COLA)|MC(GC_COTTON_CANDY)|MC(GC_BUBBLES)|MC(GC_PLASTIC)|MC(GC_FIZZY_DRINKS),
	/* Special/Disaster */
	0,0
};
#undef MC

void ShowEnginePreviewWindow(EngineID engine);

void DeleteCustomEngineNames(void)
{
	uint i;
	StringID old;

	for (i = 0; i != TOTAL_NUM_ENGINES; i++) {
		old = _engine_name_strings[i];
		_engine_name_strings[i] = i + STR_8000_KIRBY_PAUL_TANK_STEAM;
		DeleteName(old);
	}

	_vehicle_design_names &= ~1;
}

void LoadCustomEngineNames(void)
{
	// XXX: not done */
	DEBUG(misc, 1) ("LoadCustomEngineNames: not done");
}

static void SetupEngineNames(void)
{
	StringID *name;

	for (name = _engine_name_strings; name != endof(_engine_name_strings); name++)
		*name = STR_SV_EMPTY;

	DeleteCustomEngineNames();
	LoadCustomEngineNames();
}

static void AdjustAvailAircraft(void)
{
	uint16 date = _date;
	byte avail = 0;
	if (date >= 12784) avail |= 2; // big airport
	if (date < 14610 || _patches.always_small_airport) avail |= 1;  // small airport
	if (date >= 15706) avail |= 4; // enable heliport

	if (avail != _avail_aircraft) {
		_avail_aircraft = avail;
		InvalidateWindow(WC_BUILD_STATION, 0);
	}
}

static void CalcEngineReliability(Engine *e)
{
	uint age = e->age;

	if (age < e->duration_phase_1) {
		uint start = e->reliability_start;
		e->reliability = age * (e->reliability_max - start) / e->duration_phase_1 + start;
	} else if ((age -= e->duration_phase_1) < e->duration_phase_2) {
		e->reliability = e->reliability_max;
	} else if ((age -= e->duration_phase_2) < e->duration_phase_3) {
		uint max = e->reliability_max;
		e->reliability = (int)age * (int)(e->reliability_final - max) / e->duration_phase_3 + max;
	} else {
		// time's up for this engine
		// make it either available to all players (if never_expire_vehicles is enabled and if it was available earlier)
		// or disable this engine completely
		e->player_avail = (_patches.never_expire_vehicles && e->player_avail)? -1 : 0;
		e->reliability = e->reliability_final;
	}
}

void AddTypeToEngines(void)
{
	Engine* e = _engines;

	do e->type = VEH_Train;    while (++e < &_engines[ROAD_ENGINES_INDEX]);
	do e->type = VEH_Road;     while (++e < &_engines[SHIP_ENGINES_INDEX]);
	do e->type = VEH_Ship;     while (++e < &_engines[AIRCRAFT_ENGINES_INDEX]);
	do e->type = VEH_Aircraft; while (++e < &_engines[TOTAL_NUM_ENGINES]);
	do e->type = VEH_Special;  while (++e < endof(_engines));
}

void StartupEngines(void)
{
	Engine *e;
	const EngineInfo *ei;

	SetupEngineNames();

	for (e = _engines, ei = _engine_info; e != endof(_engines); e++, ei++) {
		uint32 r;

		e->age = 0;
		e->railtype = ei->railtype;
		e->flags = 0;
		e->player_avail = 0;

		r = Random();
		e->intro_date = GB(r, 0, 9) + ei->base_intro;
		if (e->intro_date <= _date) {
			e->age = (_date - e->intro_date) >> 5;
			e->player_avail = (byte)-1;
			e->flags |= ENGINE_AVAILABLE;
		}

		e->reliability_start = GB(r, 16, 14) + 0x7AE0;
		r = Random();
		e->reliability_max   = GB(r,  0, 14) + 0xBFFF;
		e->reliability_final = GB(r, 16, 14) + 0x3FFF;

		r = Random();
		e->duration_phase_1 = GB(r, 0, 5) + 7;
		e->duration_phase_2 = GB(r, 5, 4) + ei->base_life * 12 - 96;
		e->duration_phase_3 = GB(r, 9, 7) + 120;

		e->reliability_spd_dec = (ei->unk2&0x7F) << 2;

		/* my invented flag for something that is a wagon */
		if (ei->unk2 & 0x80) {
			e->age = 0xFFFF;
		} else {
			CalcEngineReliability(e);
		}

		e->lifelength = ei->lifelength + _patches.extend_vehicle_life;

		// prevent certain engines from ever appearing.
		if (!HASBIT(ei->climates, _opt.landscape)) {
			e->flags |= ENGINE_AVAILABLE;
			e->player_avail = 0;
		}

		/* This sets up type for the engine
		   It is needed if you want to ask the engine what type it is
		   It should hopefully be the same as when you ask a vehicle what it is
		   but using this, you can ask what type an engine number is
		   even if it is not a vehicle (yet)*/
	}

	AdjustAvailAircraft();
}

uint32 _engine_refit_masks[TOTAL_NUM_ENGINES];


// TODO: We don't support cargo-specific wagon overrides. Pretty exotic... ;-) --pasky

typedef struct WagonOverride {
	byte *train_id;
	int trains;
	SpriteGroup *group;
} WagonOverride;

typedef struct WagonOverrides {
	int overrides_count;
	WagonOverride *overrides;
} WagonOverrides;

static WagonOverrides _engine_wagon_overrides[TOTAL_NUM_ENGINES];

void SetWagonOverrideSprites(EngineID engine, SpriteGroup *group, byte *train_id,
	int trains)
{
	WagonOverrides *wos;
	WagonOverride *wo;

	wos = &_engine_wagon_overrides[engine];
	wos->overrides_count++;
	wos->overrides = realloc(wos->overrides,
		wos->overrides_count * sizeof(*wos->overrides));

	wo = &wos->overrides[wos->overrides_count - 1];
	/* FIXME: If we are replacing an override, release original SpriteGroup
	 * to prevent leaks. But first we need to refcount the SpriteGroup.
	 * --pasky */
	wo->group = group;
	group->ref_count++;
	wo->trains = trains;
	wo->train_id = malloc(trains);
	memcpy(wo->train_id, train_id, trains);
}

static const SpriteGroup *GetWagonOverrideSpriteSet(EngineID engine, byte overriding_engine)
{
	const WagonOverrides *wos = &_engine_wagon_overrides[engine];
	int i;

	// XXX: This could turn out to be a timesink on profiles. We could
	// always just dedicate 65535 bytes for an [engine][train] trampoline
	// for O(1). Or O(logMlogN) and searching binary tree or smt. like
	// that. --pasky

	for (i = 0; i < wos->overrides_count; i++) {
		const WagonOverride *wo = &wos->overrides[i];
		int j;

		for (j = 0; j < wo->trains; j++) {
			if (wo->train_id[j] == overriding_engine)
				return wo->group;
		}
	}
	return NULL;
}

/**
 * Unload all wagon override sprite groups.
 */
void UnloadWagonOverrides(void)
{
	WagonOverrides *wos;
	WagonOverride *wo;
	EngineID engine;
	int i;

	for (engine = 0; engine < TOTAL_NUM_ENGINES; engine++) {
		wos = &_engine_wagon_overrides[engine];
		for (i = 0; i < wos->overrides_count; i++) {
			wo = &wos->overrides[i];
			UnloadSpriteGroup(&wo->group);
			free(wo->train_id);
		}
		free(wos->overrides);
		wos->overrides_count = 0;
		wos->overrides = NULL;
	}
}

// 0 - 28 are cargos, 29 is default, 30 is the advert (purchase list)
// (It isn't and shouldn't be like this in the GRF files since new cargo types
// may appear in future - however it's more convenient to store it like this in
// memory. --pasky)
static SpriteGroup *engine_custom_sprites[TOTAL_NUM_ENGINES][NUM_GLOBAL_CID];

void SetCustomEngineSprites(EngineID engine, byte cargo, SpriteGroup *group)
{
	if (engine_custom_sprites[engine][cargo] != NULL) {
		DEBUG(grf, 6)("SetCustomEngineSprites: engine `%d' cargo `%d' already has group -- removing.", engine, cargo);
		UnloadSpriteGroup(&engine_custom_sprites[engine][cargo]);
	}
	engine_custom_sprites[engine][cargo] = group;
	group->ref_count++;
}

/**
 * Unload all engine sprite groups.
 */
void UnloadCustomEngineSprites(void)
{
	EngineID engine;
	CargoID cargo;

	for (engine = 0; engine < TOTAL_NUM_ENGINES; engine++) {
		for (cargo = 0; cargo < NUM_GLOBAL_CID; cargo++) {
			if (engine_custom_sprites[engine][cargo] != NULL) {
				DEBUG(grf, 6)("UnloadCustomEngineSprites: Unloading group for engine `%d' cargo `%d'.", engine, cargo);
				UnloadSpriteGroup(&engine_custom_sprites[engine][cargo]);
			}
		}
	}
}

typedef SpriteGroup *(*resolve_callback)(const SpriteGroup *spritegroup,
	const Vehicle *veh, uint16 callback_info, void *resolve_func); /* XXX data pointer used as function pointer */

static const SpriteGroup* ResolveVehicleSpriteGroup(const SpriteGroup *spritegroup,
	const Vehicle *veh, uint16 callback_info, resolve_callback resolve_func)
{
	if (spritegroup == NULL)
		return NULL;

	//debug("spgt %d", spritegroup->type);
	switch (spritegroup->type) {
		case SGT_REAL:
		case SGT_CALLBACK:
			return spritegroup;

		case SGT_DETERMINISTIC: {
			const DeterministicSpriteGroup *dsg = &spritegroup->g.determ;
			const SpriteGroup *target;
			int value = -1;

			//debug("[%p] Having fun resolving variable %x", veh, dsg->variable);
			if (dsg->variable == 0x0C) {
				/* Callback ID */
				value = callback_info & 0xFF;
			} else if ((dsg->variable >> 6) == 0) {
				/* General property */
				value = GetDeterministicSpriteValue(dsg->variable);
			} else {
				/* Vehicle-specific property. */

				if (veh == NULL) {
					/* We are in a purchase list of something,
					 * and we are checking for something undefined.
					 * That means we should get the first target
					 * (NOT the default one). */
					if (dsg->num_ranges > 0) {
						target = dsg->ranges[0].group;
					} else {
						target = dsg->default_group;
					}
					return resolve_func(target, NULL, callback_info, resolve_func);
				}

				if (dsg->var_scope == VSG_SCOPE_PARENT) {
					/* First engine in the vehicle chain */
					if (veh->type == VEH_Train)
						veh = GetFirstVehicleInChain(veh);
				}

				if (dsg->variable == 0x40 || dsg->variable == 0x41) {
					if (veh->type == VEH_Train) {
						const Vehicle *u = GetFirstVehicleInChain(veh);
						byte chain_before = 0, chain_after = 0;

						while (u != veh) {
							chain_before++;
							if (dsg->variable == 0x41 && u->engine_type != veh->engine_type)
								chain_before = 0;
							u = u->next;
						}
						while (u->next != NULL && (dsg->variable == 0x40 || u->next->engine_type == veh->engine_type)) {
							chain_after++;
							u = u->next;
						};

						value = chain_before | chain_after << 8
						        | (chain_before + chain_after) << 16;
					} else {
						value = 1; /* 1 vehicle in the chain */
					}

				} else {
					// TTDPatch runs on little-endian arch;
					// Variable is 0x80 + offset in TTD's vehicle structure
					switch (dsg->variable - 0x80) {
#define veh_prop(id_, value_) case (id_): value = (value_); break
						veh_prop(0x00, veh->type);
						veh_prop(0x01, veh->subtype);
						veh_prop(0x04, veh->index);
						veh_prop(0x05, veh->index & 0xFF);
						/* XXX? Is THIS right? */
						veh_prop(0x0A, PackOrder(&veh->current_order));
						veh_prop(0x0B, PackOrder(&veh->current_order) & 0xff);
						veh_prop(0x0C, veh->num_orders);
						veh_prop(0x0D, veh->cur_order_index);
						veh_prop(0x10, veh->load_unload_time_rem);
						veh_prop(0x11, veh->load_unload_time_rem & 0xFF);
						veh_prop(0x12, veh->date_of_last_service);
						veh_prop(0x13, veh->date_of_last_service & 0xFF);
						veh_prop(0x14, veh->service_interval);
						veh_prop(0x15, veh->service_interval & 0xFF);
						veh_prop(0x16, veh->last_station_visited);
						veh_prop(0x17, veh->tick_counter);
						veh_prop(0x18, veh->max_speed);
						veh_prop(0x19, veh->max_speed & 0xFF);
						veh_prop(0x1F, veh->direction);
						veh_prop(0x28, veh->cur_image);
						veh_prop(0x29, veh->cur_image & 0xFF);
						veh_prop(0x32, veh->vehstatus);
						veh_prop(0x33, veh->vehstatus);
						veh_prop(0x34, veh->cur_speed);
						veh_prop(0x35, veh->cur_speed & 0xFF);
						veh_prop(0x36, veh->subspeed);
						veh_prop(0x37, veh->acceleration);
						veh_prop(0x39, veh->cargo_type);
						veh_prop(0x3A, veh->cargo_cap);
						veh_prop(0x3B, veh->cargo_cap & 0xFF);
						veh_prop(0x3C, veh->cargo_count);
						veh_prop(0x3D, veh->cargo_count & 0xFF);
						veh_prop(0x3E, veh->cargo_source); // Probably useless; so what
						veh_prop(0x3F, veh->cargo_days);
						veh_prop(0x40, veh->age);
						veh_prop(0x41, veh->age & 0xFF);
						veh_prop(0x42, veh->max_age);
						veh_prop(0x43, veh->max_age & 0xFF);
						veh_prop(0x44, veh->build_year);
						veh_prop(0x45, veh->unitnumber);
						veh_prop(0x46, veh->engine_type);
						veh_prop(0x47, veh->engine_type & 0xFF);
						veh_prop(0x48, veh->spritenum);
						veh_prop(0x49, veh->day_counter);
						veh_prop(0x4A, veh->breakdowns_since_last_service);
						veh_prop(0x4B, veh->breakdown_ctr);
						veh_prop(0x4C, veh->breakdown_delay);
						veh_prop(0x4D, veh->breakdown_chance);
						veh_prop(0x4E, veh->reliability);
						veh_prop(0x4F, veh->reliability & 0xFF);
						veh_prop(0x50, veh->reliability_spd_dec);
						veh_prop(0x51, veh->reliability_spd_dec & 0xFF);
						veh_prop(0x52, veh->profit_this_year);
						veh_prop(0x53, veh->profit_this_year & 0xFFFFFF);
						veh_prop(0x54, veh->profit_this_year & 0xFFFF);
						veh_prop(0x55, veh->profit_this_year & 0xFF);
						veh_prop(0x56, veh->profit_last_year);
						veh_prop(0x57, veh->profit_last_year & 0xFF);
						veh_prop(0x58, veh->profit_last_year);
						veh_prop(0x59, veh->profit_last_year & 0xFF);
						veh_prop(0x5A, veh->next == NULL ? INVALID_VEHICLE : veh->next->index);
						veh_prop(0x5C, veh->value);
						veh_prop(0x5D, veh->value & 0xFFFFFF);
						veh_prop(0x5E, veh->value & 0xFFFF);
						veh_prop(0x5F, veh->value & 0xFF);
						veh_prop(0x60, veh->string_id);
						veh_prop(0x61, veh->string_id & 0xFF);
						/* 00h..07h=sub image? 40h=in tunnel; actually some kind of status
						 * aircraft: >=13h when in flight
						 * train, ship: 80h=in depot
						 * rv: 0feh=in depot */
						/* TODO veh_prop(0x62, veh->???); */

						/* TODO: The rest is per-vehicle, I hope no GRF file looks so far.
						 * But they won't let us have an easy ride so surely *some* GRF
						 * file does. So someone needs to do this too. --pasky */

#undef veh_prop
					}
				}
			}

			target = value != -1 ? EvalDeterministicSpriteGroup(dsg, value) : dsg->default_group;
			//debug("Resolved variable %x: %d, %p", dsg->variable, value, callback);
			return resolve_func(target, veh, callback_info, resolve_func);
		}

		case SGT_RANDOMIZED: {
			const RandomizedSpriteGroup *rsg = &spritegroup->g.random;

			if (veh == NULL) {
				/* Purchase list of something. Show the first one. */
				assert(rsg->num_groups > 0);
				//debug("going for %p: %d", rsg->groups[0], rsg->groups[0].type);
				return resolve_func(rsg->groups[0], NULL, callback_info, resolve_func);
			}

			if (rsg->var_scope == VSG_SCOPE_PARENT) {
				/* First engine in the vehicle chain */
				if (veh->type == VEH_Train)
					veh = GetFirstVehicleInChain(veh);
			}

			return resolve_func(EvalRandomizedSpriteGroup(rsg, veh->random_bits), veh, callback_info, resolve_func);
		}

		default:
			error("I don't know how to handle such a spritegroup %d!", spritegroup->type);
			return NULL;
	}
}

static const SpriteGroup *GetVehicleSpriteGroup(EngineID engine, const Vehicle *v)
{
	const SpriteGroup *group;
	byte cargo = GC_PURCHASE;

	if (v != NULL) {
		cargo = _global_cargo_id[_opt.landscape][v->cargo_type];
		assert(cargo != GC_INVALID);
	}

	group = engine_custom_sprites[engine][cargo];

	if (v != NULL && v->type == VEH_Train) {
		const SpriteGroup *overset = GetWagonOverrideSpriteSet(engine, v->u.rail.first_engine);

		if (overset != NULL) group = overset;
	}

	return group;
}

int GetCustomEngineSprite(EngineID engine, const Vehicle *v, byte direction)
{
	const SpriteGroup *group;
	const RealSpriteGroup *rsg;
	byte cargo = GC_PURCHASE;
	byte loaded = 0;
	bool in_motion = 0;
	int totalsets, spriteset;
	int r;

	if (v != NULL) {
		int capacity = v->cargo_cap;

		cargo = _global_cargo_id[_opt.landscape][v->cargo_type];
		assert(cargo != GC_INVALID);

		if (capacity == 0) capacity = 1;
		loaded = (v->cargo_count * 100) / capacity;
		in_motion = (v->cur_speed != 0);
	}

	group = GetVehicleSpriteGroup(engine, v);
	group = ResolveVehicleSpriteGroup(group, v, 0, (resolve_callback) ResolveVehicleSpriteGroup);

	if (group == NULL && cargo != GC_DEFAULT) {
		// This group is empty but perhaps there'll be a default one.
		group = ResolveVehicleSpriteGroup(engine_custom_sprites[engine][GC_DEFAULT], v, 0,
		                                (resolve_callback) ResolveVehicleSpriteGroup);
	}

	if (group == NULL)
		return 0;

	assert(group->type == SGT_REAL);
	rsg = &group->g.real;

	if (!rsg->sprites_per_set) {
		// This group is empty. This function users should therefore
		// look up the sprite number in _engine_original_sprites.
		return 0;
	}

	assert(rsg->sprites_per_set <= 8);
	direction %= rsg->sprites_per_set;

	totalsets = in_motion ? rsg->loaded_count : rsg->loading_count;

	// My aim here is to make it possible to visually determine absolutely
	// empty and totally full vehicles. --pasky
	if (loaded == 100 || totalsets == 1) { // full
		spriteset = totalsets - 1;
	} else if (loaded == 0 || totalsets == 2) { // empty
		spriteset = 0;
	} else { // something inbetween
		spriteset = loaded * (totalsets - 2) / 100 + 1;
		// correct possible rounding errors
		if (!spriteset)
			spriteset = 1;
		else if (spriteset == totalsets - 1)
			spriteset--;
	}

	r = (in_motion ? rsg->loaded[spriteset]->g.result.result : rsg->loading[spriteset]->g.result.result) + direction;
	return r;
}

/**
 * Check if a wagon is currently using a wagon override
 * @param v The wagon to check
 * @return true if it is using an override, false otherwise
 */
bool UsesWagonOverride(const Vehicle *v) {
	assert(v->type == VEH_Train);
	return GetWagonOverrideSpriteSet(v->engine_type, v->u.rail.first_engine) != NULL;
}

/**
 * Evaluates a newgrf callback
 * @param callback_info info about which callback to evaluate
 *  (bit 0-7)  = CallBack id of the callback to use, see CallBackId enum
 *  (bit 8-15) = Other info some callbacks need to have, callback specific, see CallBackId enum, not used yet
 * @param engine Engine type of the vehicle to evaluate the callback for
 * @param vehicle The vehicle to evaluate the callback for, NULL if it doesnt exist (yet)
 * @return The value the callback returned, or CALLBACK_FAILED if it failed
 */
uint16 GetCallBackResult(uint16 callback_info, EngineID engine, const Vehicle *v)
{
	const SpriteGroup *group;
	byte cargo = GC_DEFAULT;

	if (v != NULL)
		cargo = _global_cargo_id[_opt.landscape][v->cargo_type];

	group = engine_custom_sprites[engine][cargo];

	if (v != NULL && v->type == VEH_Train) {
		const SpriteGroup *overset = GetWagonOverrideSpriteSet(engine, v->u.rail.first_engine);

		if (overset != NULL) group = overset;
	}

	group = ResolveVehicleSpriteGroup(group, v, callback_info, (resolve_callback) ResolveVehicleSpriteGroup);

	if (group == NULL && cargo != GC_DEFAULT) {
		// This group is empty but perhaps there'll be a default one.
		group = ResolveVehicleSpriteGroup(engine_custom_sprites[engine][GC_DEFAULT], v, callback_info,
		                                (resolve_callback) ResolveVehicleSpriteGroup);
	}

	if (group == NULL || group->type != SGT_CALLBACK)
		return CALLBACK_FAILED;

	return group->g.callback.result;
}



// Global variables are evil, yes, but we would end up with horribly overblown
// calling convention otherwise and this should be 100% reentrant.
static byte _vsg_random_triggers;
static byte _vsg_bits_to_reseed;

static const SpriteGroup *TriggerVehicleSpriteGroup(const SpriteGroup *spritegroup,
	Vehicle *veh, uint16 callback_info, resolve_callback resolve_func)
{
	if (spritegroup == NULL)
		return NULL;

	if (spritegroup->type == SGT_RANDOMIZED) {
		_vsg_bits_to_reseed |= RandomizedSpriteGroupTriggeredBits(
			&spritegroup->g.random,
			_vsg_random_triggers,
			&veh->waiting_triggers
		);
	}

	return ResolveVehicleSpriteGroup(spritegroup, veh, callback_info, resolve_func);
}

static void DoTriggerVehicle(Vehicle *veh, VehicleTrigger trigger, byte base_random_bits, bool first)
{
	const SpriteGroup *group;
	const RealSpriteGroup *rsg;
	byte new_random_bits;

	_vsg_random_triggers = trigger;
	_vsg_bits_to_reseed = 0;
	group = TriggerVehicleSpriteGroup(GetVehicleSpriteGroup(veh->engine_type, veh), veh, 0,
	                                  (resolve_callback) TriggerVehicleSpriteGroup);

	if (group == NULL && veh->cargo_type != GC_DEFAULT) {
		// This group turned out to be empty but perhaps there'll be a default one.
		group = TriggerVehicleSpriteGroup(engine_custom_sprites[veh->engine_type][GC_DEFAULT], veh, 0,
		                                  (resolve_callback) TriggerVehicleSpriteGroup);
	}

	if (group == NULL)
		return;

	assert(group->type == SGT_REAL);
	rsg = &group->g.real;

	new_random_bits = Random();
	veh->random_bits &= ~_vsg_bits_to_reseed;
	veh->random_bits |= (first ? new_random_bits : base_random_bits) & _vsg_bits_to_reseed;

	switch (trigger) {
		case VEHICLE_TRIGGER_NEW_CARGO:
			/* All vehicles in chain get ANY_NEW_CARGO trigger now.
			 * So we call it for the first one and they will recurse. */
			/* Indexing part of vehicle random bits needs to be
			 * same for all triggered vehicles in the chain (to get
			 * all the random-cargo wagons carry the same cargo,
			 * i.e.), so we give them all the NEW_CARGO triggered
			 * vehicle's portion of random bits. */
			assert(first);
			DoTriggerVehicle(GetFirstVehicleInChain(veh), VEHICLE_TRIGGER_ANY_NEW_CARGO, new_random_bits, false);
			break;
		case VEHICLE_TRIGGER_DEPOT:
			/* We now trigger the next vehicle in chain recursively.
			 * The random bits portions may be different for each
			 * vehicle in chain. */
			if (veh->next != NULL)
				DoTriggerVehicle(veh->next, trigger, 0, true);
			break;
		case VEHICLE_TRIGGER_EMPTY:
			/* We now trigger the next vehicle in chain
			 * recursively.  The random bits portions must be same
			 * for each vehicle in chain, so we give them all
			 * first chained vehicle's portion of random bits. */
			if (veh->next != NULL)
				DoTriggerVehicle(veh->next, trigger, first ? new_random_bits : base_random_bits, false);
			break;
		case VEHICLE_TRIGGER_ANY_NEW_CARGO:
			/* Now pass the trigger recursively to the next vehicle
			 * in chain. */
			assert(!first);
			if (veh->next != NULL)
				DoTriggerVehicle(veh->next, VEHICLE_TRIGGER_ANY_NEW_CARGO, base_random_bits, false);
			break;
	}
}

void TriggerVehicle(Vehicle *veh, VehicleTrigger trigger)
{
	DoTriggerVehicle(veh, trigger, 0, true);
}

static char *_engine_custom_names[TOTAL_NUM_ENGINES];

void SetCustomEngineName(EngineID engine, const char *name)
{
	_engine_custom_names[engine] = strdup(name);
}

void UnInitNewgrEngines(void)
{
	char **i;
	for (i = _engine_custom_names; i != endof(_engine_custom_names); i++) {
		free(*i);
		*i = NULL;
	}
}

StringID GetCustomEngineName(EngineID engine)
{
	if (!_engine_custom_names[engine])
		return _engine_name_strings[engine];
	ttd_strlcpy(_userstring, _engine_custom_names[engine], lengthof(_userstring));
	return STR_SPEC_USERSTRING;
}


void AcceptEnginePreview(Engine *e, PlayerID player)
{
	Player *p = GetPlayer(player);

	assert(e->railtype < RAILTYPE_END);
	SETBIT(e->player_avail, player);
	SETBIT(p->avail_railtypes, e->railtype);

	e->preview_player = 0xFF;
	InvalidateWindowClasses(WC_BUILD_VEHICLE);
	InvalidateWindowClasses(WC_REPLACE_VEHICLE);
}

static PlayerID GetBestPlayer(PlayerID pp)
{
	const Player *p;
	int32 best_hist;
	PlayerID best_player;
	uint mask = 0;

	do {
		best_hist = -1;
		best_player = OWNER_SPECTATOR;
		FOR_ALL_PLAYERS(p) {
			if (p->is_active && p->block_preview == 0 && !HASBIT(mask, p->index) &&
					p->old_economy[0].performance_history > best_hist) {
				best_hist = p->old_economy[0].performance_history;
				best_player = p->index;
			}
		}

		if (best_player == OWNER_SPECTATOR) return OWNER_SPECTATOR;

		SETBIT(mask, best_player);
	} while (--pp != 0);

	return best_player;
}

void EnginesDailyLoop(void)
{
	EngineID i;

	if (_cur_year >= 130) return;

	for (i = 0; i != lengthof(_engines); i++) {
		Engine* e = &_engines[i];

		if (e->flags & ENGINE_INTRODUCING) {
			if (e->flags & ENGINE_PREVIEWING) {
				if (e->preview_player != 0xFF && !--e->preview_wait) {
					e->flags &= ~ENGINE_PREVIEWING;
					DeleteWindowById(WC_ENGINE_PREVIEW, i);
					e->preview_player++;
				}
 			} else if (e->preview_player != 0xFF) {
				PlayerID best_player = GetBestPlayer(e->preview_player);

				if (best_player == OWNER_SPECTATOR) {
					e->preview_player = 0xFF;
					continue;
				}

				if (!IS_HUMAN_PLAYER(best_player)) {
					/* XXX - TTDBUG: TTD has a bug here ???? */
					AcceptEnginePreview(e, best_player);
				} else {
					e->flags |= ENGINE_PREVIEWING;
					e->preview_wait = 20;
					if (IS_INTERACTIVE_PLAYER(best_player))
						ShowEnginePreviewWindow(i);
				}
			}
		}
	}
}

/** Accept an engine prototype. XXX - it is possible that the top-player
 * changes while you are waiting to accept the offer? Then it becomes invalid
 * @param x,y unused
 * @param p1 engine-prototype offered
 * @param p2 unused
 */
int32 CmdWantEnginePreview(int x, int y, uint32 flags, uint32 p1, uint32 p2)
{
	Engine *e;
	if (!IsEngineIndex(p1)) return CMD_ERROR;

	e = GetEngine(p1);
	if (GetBestPlayer(e->preview_player) != _current_player) return CMD_ERROR;

	if (flags & DC_EXEC)
		AcceptEnginePreview(e, _current_player);

	return 0;
}

// Determine if an engine type is a wagon (and not a loco)
static bool IsWagon(EngineID index)
{
	return index < NUM_TRAIN_ENGINES && RailVehInfo(index)->flags & RVI_WAGON;
}

static void NewVehicleAvailable(Engine *e)
{
	Vehicle *v;
	Player *p;
	EngineID index = e - _engines;

	// In case the player didn't build the vehicle during the intro period,
	// prevent that player from getting future intro periods for a while.
	if (e->flags&ENGINE_INTRODUCING) {
		FOR_ALL_PLAYERS(p) {
			uint block_preview = p->block_preview;

			if (!HASBIT(e->player_avail,p->index))
				continue;

			/* We assume the user did NOT build it.. prove me wrong ;) */
			p->block_preview = 20;

			FOR_ALL_VEHICLES(v) {
				if (v->type == VEH_Train || v->type == VEH_Road || v->type == VEH_Ship ||
						(v->type == VEH_Aircraft && v->subtype <= 2)) {
					if (v->owner == p->index && v->engine_type == index) {
						/* The user did prove me wrong, so restore old value */
						p->block_preview = block_preview;
						break;
					}
				}
			}
		}
	}

	e->flags = (e->flags & ~ENGINE_INTRODUCING) | ENGINE_AVAILABLE;
	InvalidateWindowClasses(WC_BUILD_VEHICLE);
	InvalidateWindowClasses(WC_REPLACE_VEHICLE);

	// Now available for all players
	e->player_avail = (byte)-1;

	// Do not introduce new rail wagons
	if (IsWagon(index))
		return;

	// make maglev / monorail available
	FOR_ALL_PLAYERS(p) {
		if (p->is_active) {
			assert(e->railtype < RAILTYPE_END);
			SETBIT(p->avail_railtypes, e->railtype);
		}
	}

	if (index < NUM_TRAIN_ENGINES) {
		AddNewsItem(index, NEWS_FLAGS(NM_CALLBACK, 0, NT_NEW_VEHICLES, DNC_TRAINAVAIL), 0, 0);
	} else if (index < NUM_TRAIN_ENGINES + NUM_ROAD_ENGINES) {
		AddNewsItem(index, NEWS_FLAGS(NM_CALLBACK, 0, NT_NEW_VEHICLES, DNC_ROADAVAIL), 0, 0);
	} else if (index < NUM_TRAIN_ENGINES + NUM_ROAD_ENGINES + NUM_SHIP_ENGINES) {
		AddNewsItem(index, NEWS_FLAGS(NM_CALLBACK, 0, NT_NEW_VEHICLES, DNC_SHIPAVAIL), 0, 0);
	} else {
		AddNewsItem(index, NEWS_FLAGS(NM_CALLBACK, 0, NT_NEW_VEHICLES, DNC_AIRCRAFTAVAIL), 0, 0);
	}
}

void EnginesMonthlyLoop(void)
{
	Engine *e;

	if (_cur_year < 130) {
		for (e = _engines; e != endof(_engines); e++) {
			// Age the vehicle
			if (e->flags & ENGINE_AVAILABLE && e->age != 0xFFFF) {
				e->age++;
				CalcEngineReliability(e);
			}

			if (!(e->flags & ENGINE_AVAILABLE) && (uint16)(_date - min(_date, 365)) >= e->intro_date) {
				// Introduce it to all players
				NewVehicleAvailable(e);
			} else if (!(e->flags & (ENGINE_AVAILABLE|ENGINE_INTRODUCING)) && _date >= e->intro_date) {
				// Introduction date has passed.. show introducing dialog to one player.
				e->flags |= ENGINE_INTRODUCING;

				// Do not introduce new rail wagons
				if (!IsWagon(e - _engines))
					e->preview_player = 1; // Give to the player with the highest rating.
			}
		}
	}
	AdjustAvailAircraft();
}

/** Rename an engine.
 * @param x,y unused
 * @param p1 engine ID to rename
 * @param p2 unused
 */
int32 CmdRenameEngine(int x, int y, uint32 flags, uint32 p1, uint32 p2)
{
	StringID str;

	if (!IsEngineIndex(p1) || _cmd_text[0] == '\0') return CMD_ERROR;

	str = AllocateNameUnique(_cmd_text, 0);
	if (str == 0) return CMD_ERROR;

	if (flags & DC_EXEC) {
		StringID old_str = _engine_name_strings[p1];
		_engine_name_strings[p1] = str;
		DeleteName(old_str);
		_vehicle_design_names |= 3;
		MarkWholeScreenDirty();
	} else {
		DeleteName(str);
	}

	return 0;
}


static const SaveLoad _engine_desc[] = {
	SLE_VAR(Engine,intro_date,						SLE_UINT16),
	SLE_VAR(Engine,age,										SLE_UINT16),
	SLE_VAR(Engine,reliability,						SLE_UINT16),
	SLE_VAR(Engine,reliability_spd_dec,		SLE_UINT16),
	SLE_VAR(Engine,reliability_start,			SLE_UINT16),
	SLE_VAR(Engine,reliability_max,				SLE_UINT16),
	SLE_VAR(Engine,reliability_final,			SLE_UINT16),
	SLE_VAR(Engine,duration_phase_1,			SLE_UINT16),
	SLE_VAR(Engine,duration_phase_2,			SLE_UINT16),
	SLE_VAR(Engine,duration_phase_3,			SLE_UINT16),

	SLE_VAR(Engine,lifelength,						SLE_UINT8),
	SLE_VAR(Engine,flags,									SLE_UINT8),
	SLE_VAR(Engine,preview_player,				SLE_UINT8),
	SLE_VAR(Engine,preview_wait,					SLE_UINT8),
	SLE_VAR(Engine,railtype,							SLE_UINT8),
	SLE_VAR(Engine,player_avail,					SLE_UINT8),

	// reserve extra space in savegame here. (currently 16 bytes)
	SLE_CONDARR(NullStruct,null,SLE_FILE_U64 | SLE_VAR_NULL, 2, 2, 255),

	SLE_END()
};

static void Save_ENGN(void)
{
	uint i;

	for (i = 0; i != lengthof(_engines); i++) {
		SlSetArrayIndex(i);
		SlObject(&_engines[i], _engine_desc);
	}
}

static void Load_ENGN(void)
{
	int index;
	while ((index = SlIterateArray()) != -1) {
		SlObject(GetEngine(index), _engine_desc);
	}
}

static void LoadSave_ENGS(void)
{
	SlArray(_engine_name_strings, lengthof(_engine_name_strings), SLE_STRINGID);
}

const ChunkHandler _engine_chunk_handlers[] = {
	{ 'ENGN', Save_ENGN, Load_ENGN, CH_ARRAY},
	{ 'ENGS', LoadSave_ENGS, LoadSave_ENGS, CH_RIFF | CH_LAST},
};


/*
 * returns true if an engine is valid, of the specified type, and buildable by
 * the current player, false otherwise
 *
 * engine = index of the engine to check
 * type   = the type the engine should be of (VEH_xxx)
 */
bool IsEngineBuildable(uint engine, byte type)
{
	const Engine *e;

	// check if it's an engine that is in the engine array
	if (!IsEngineIndex(engine)) return false;

	e = GetEngine(engine);

	// check if it's an engine of specified type
	if (e->type != type) return false;

	// check if it's available
	if (!HASBIT(e->player_avail, _current_player)) return false;

	return true;
}