Changes to ship collision avoidance algorithm

[openttd-joker.git] / src / ship_cmd.cpp

/* $Id$ */

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file ship_cmd.cpp Handling of ships. */

#include "stdafx.h"
#include "ship.h"
#include "dock_base.h"
#include "landscape.h"
#include "timetable.h"
#include "news_func.h"
#include "company_func.h"
#include "pathfinder/npf/npf_func.h"
#include "depot_base.h"
#include "station_base.h"
#include "newgrf_engine.h"
#include "pathfinder/yapf/yapf.h"
#include "newgrf_sound.h"
#include "spritecache.h"
#include "strings_func.h"
#include "window_func.h"
#include "date_func.h"
#include "vehicle_func.h"
#include "sound_func.h"
#include "ai/ai.hpp"
#include "game/game.hpp"
#include "pathfinder/opf/opf_ship.h"
#include "engine_base.h"
#include "company_base.h"
#include "tunnelbridge_map.h"
#include "zoom_func.h"

#include "table/strings.h"

#include "safeguards.h"

/**
 * Determine the effective #WaterClass for a ship travelling on a tile.
 * @param tile Tile of interest
 * @return the waterclass to be used by the ship.
 */
WaterClass GetEffectiveWaterClass(TileIndex tile)
{
        if (HasTileWaterClass(tile)) return GetWaterClass(tile);
        if (IsTileType(tile, MP_TUNNELBRIDGE)) {
                assert(GetTunnelBridgeTransportType(tile) == TRANSPORT_WATER);
                return WATER_CLASS_CANAL;
        }
        if (IsTileType(tile, MP_RAILWAY)) {
                assert(GetRailGroundType(tile) == RAIL_GROUND_WATER);
                return WATER_CLASS_SEA;
        }
        NOT_REACHED();
}

static const uint16 _ship_sprites[] = {0x0E5D, 0x0E55, 0x0E65, 0x0E6D};

template <>
bool IsValidImageIndex<VEH_SHIP>(uint8 image_index)
{
        return image_index < lengthof(_ship_sprites);
}

static inline TrackBits GetTileShipTrackStatus(TileIndex tile)
{
        return TrackStatusToTrackBits(GetTileTrackStatus(tile, TRANSPORT_WATER, 0));
}

static void GetShipIcon(EngineID engine, EngineImageType image_type, VehicleSpriteSeq *result)
{
        const Engine *e = Engine::Get(engine);
        uint8 spritenum = e->u.ship.image_index;

        if (is_custom_sprite(spritenum)) {
                GetCustomVehicleIcon(engine, DIR_W, image_type, result);
                if (result->IsValid()) return;

                spritenum = e->original_image_index;
        }

        assert(IsValidImageIndex<VEH_SHIP>(spritenum));
        result->Set(DIR_W + _ship_sprites[spritenum]);
}

void DrawShipEngine(int left, int right, int preferred_x, int y, EngineID engine, PaletteID pal, EngineImageType image_type)
{
        VehicleSpriteSeq seq;
        GetShipIcon(engine, image_type, &seq);

        Rect16 rect = seq.GetBounds();
        preferred_x = Clamp(preferred_x,
                        left - UnScaleGUI(rect.left),
                        right - UnScaleGUI(rect.right));

        seq.Draw(preferred_x, y, pal, pal == PALETTE_CRASH);
}

/**
 * Get the size of the sprite of a ship sprite heading west (used for lists).
 * @param engine The engine to get the sprite from.
 * @param[out] width The width of the sprite.
 * @param[out] height The height of the sprite.
 * @param[out] xoffs Number of pixels to shift the sprite to the right.
 * @param[out] yoffs Number of pixels to shift the sprite downwards.
 * @param image_type Context the sprite is used in.
 */
void GetShipSpriteSize(EngineID engine, uint &width, uint &height, int &xoffs, int &yoffs, EngineImageType image_type)
{
        VehicleSpriteSeq seq;
        GetShipIcon(engine, image_type, &seq);

        Rect16 rect = seq.GetBounds();

        width  = UnScaleGUI(rect.right - rect.left + 1);
        height = UnScaleGUI(rect.bottom - rect.top + 1);
        xoffs  = UnScaleGUI(rect.left);
        yoffs  = UnScaleGUI(rect.top);
}

void Ship::GetImage(Direction direction, EngineImageType image_type, VehicleSpriteSeq *result) const
{
        uint8 spritenum = this->spritenum;

        if (is_custom_sprite(spritenum)) {
                GetCustomVehicleSprite(this, direction, image_type, result);
                if (result->IsValid()) return;

                spritenum = this->GetEngine()->original_image_index;
        }

        assert(IsValidImageIndex<VEH_SHIP>(spritenum));
        result->Set(_ship_sprites[spritenum] + direction);
}

static const Depot *FindClosestShipDepot(const Vehicle *v, uint max_distance)
{
        /* Find the closest depot */
        const Depot *depot;
        const Depot *best_depot = NULL;
        /* If we don't have a maximum distance, i.e. distance = 0,
         * we want to find any depot so the best distance of no
         * depot must be more than any correct distance. On the
         * other hand if we have set a maximum distance, any depot
         * further away than max_distance can safely be ignored. */
        uint best_dist = max_distance == 0 ? UINT_MAX : max_distance + 1;

        FOR_ALL_DEPOTS(depot) {
                TileIndex tile = depot->xy;
                if (IsShipDepotTile(tile) && IsTileOwner(tile, v->owner)) {
                        uint dist = DistanceManhattan(tile, v->tile);
                        if (dist < best_dist) {
                                best_dist = dist;
                                best_depot = depot;
                        }
                }
        }

        return best_depot;
}

static void CheckIfShipNeedsService(Vehicle *v)
{
        if (Company::Get(v->owner)->settings.vehicle.servint_ships == 0 || !v->NeedsAutomaticServicing()) return;
        if (v->IsChainInDepot()) {
                VehicleServiceInDepot(v);
                return;
        }

        uint max_distance;
        switch (_settings_game.pf.pathfinder_for_ships) {
                case VPF_OPF:  max_distance = 12; break;
                case VPF_NPF:  max_distance = _settings_game.pf.npf.maximum_go_to_depot_penalty  / NPF_TILE_LENGTH;  break;
                case VPF_YAPF: max_distance = _settings_game.pf.yapf.maximum_go_to_depot_penalty / YAPF_TILE_LENGTH; break;
                default: NOT_REACHED();
        }

        const Depot *depot = FindClosestShipDepot(v, max_distance);

        if (depot == NULL) {
                if (v->current_order.IsType(OT_GOTO_DEPOT)) {
                        v->current_order.MakeDummy();
                        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                }
                return;
        }

        v->current_order.MakeGoToDepot(depot->index, ODTFB_SERVICE);
        v->dest_tile = depot->xy;
        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
}

/**
 * Update the caches of this ship.
 */
void Ship::UpdateCache()
{
        const ShipVehicleInfo *svi = ShipVehInfo(this->engine_type);

        /* Get speed fraction for the current water type. Aqueducts are always canals. */
        bool is_ocean = GetEffectiveWaterClass(this->tile) == WATER_CLASS_SEA;
        uint raw_speed = GetVehicleProperty(this, PROP_SHIP_SPEED, svi->max_speed);
        this->vcache.cached_max_speed = svi->ApplyWaterClassSpeedFrac(raw_speed, is_ocean);

        /* Update cargo aging period. */
        this->vcache.cached_cargo_age_period = GetVehicleProperty(this, PROP_SHIP_CARGO_AGE_PERIOD, EngInfo(this->engine_type)->cargo_age_period);

        this->UpdateVisualEffect();
}

Money Ship::GetRunningCost() const
{
        const Engine *e = this->GetEngine();
        uint cost_factor = GetVehicleProperty(this, PROP_SHIP_RUNNING_COST_FACTOR, e->u.ship.running_cost);
        return GetPrice(PR_RUNNING_SHIP, cost_factor, e->GetGRF());
}

void Ship::OnNewDay()
{
        if ((++this->day_counter & 7) == 0) {
                DecreaseVehicleValue(this);
        }

        CheckVehicleBreakdown(this);
        AgeVehicle(this);
        CheckIfShipNeedsService(this);

        CheckOrders(this);

        if (this->running_ticks == 0) return;

        CommandCost cost(EXPENSES_SHIP_RUN, this->GetRunningCost() * this->running_ticks / (DAYS_IN_YEAR * DAY_TICKS));

        this->profit_this_year -= cost.GetCost();
        this->running_ticks = 0;

        SubtractMoneyFromCompanyFract(this->owner, cost);

        SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
        /* we need this for the profit */
        SetWindowClassesDirty(WC_SHIPS_LIST);
}

Trackdir Ship::GetVehicleTrackdir() const
{
        if (this->vehstatus & VS_CRASHED) return INVALID_TRACKDIR;

        if (this->IsInDepot()) {
                /* We'll assume the ship is facing outwards */
                return DiagDirToDiagTrackdir(GetShipDepotDirection(this->tile));
        }

        if (this->state == TRACK_BIT_WORMHOLE) {
                /* ship on aqueduct, so just use his direction and assume a diagonal track */
                return DiagDirToDiagTrackdir(DirToDiagDir(this->direction));
        }

        return TrackDirectionToTrackdir(FindFirstTrack(this->state), this->direction);
}

void Ship::MarkDirty()
{
        this->colourmap = PAL_NONE;
        this->UpdateViewport(true, false);
        this->UpdateCache();
}

static void PlayShipSound(const Vehicle *v)
{
        if (!PlayVehicleSound(v, VSE_START)) {
                SndPlayVehicleFx(ShipVehInfo(v->engine_type)->sfx, v);
        }
}

void Ship::PlayLeaveStationSound() const
{
        PlayShipSound(this);
}
  
/**
 * Of all the docks a station has, return the best destination for a ship.
 * @param v The ship.
 * @param st Station the ship \a v is heading for.
 * @return The free and closest (if none is free, just closest) dock of station \a st to ship \a v.
 */
const Dock* GetBestDock(const Ship *v, const Station *st)
{
        assert(st != NULL && st->HasFacilities(FACIL_DOCK) && st->docks != NULL);
        if (st->docks->next == NULL) return st->docks;

        Dock *best_dock = NULL;
        uint best_distance = UINT_MAX;

        for (Dock *dock = st->docks; dock != NULL; dock = dock->next) {
                uint new_distance = DistanceManhattan(v->tile, dock->flat);

                if (new_distance < best_distance) {
                        best_dock = dock;
                        best_distance = new_distance;
                }
        }

        assert(best_dock != NULL);

        return best_dock;
}

TileIndex Ship::GetOrderStationLocation(StationID station)
{
        if (station == this->last_station_visited) this->last_station_visited = INVALID_STATION;

        const Station *st = Station::Get(station);
        if (st->HasFacilities(FACIL_DOCK)) {
                if (st->docks == NULL) {
                        return st->xy; // A buoy
                } else {
                        const Dock* dock = GetBestDock(this, st);

                        DiagDirection direction = DiagdirBetweenTiles(dock->sloped, dock->flat);
                        return dock->flat + TileOffsByDiagDir(direction);
                }
        } else {
                this->IncrementRealOrderIndex();
                return 0;
        }
}

void Ship::UpdateDeltaXY(Direction direction)
{
        static const int8 _delta_xy_table[8][4] = {
                /* y_extent, x_extent, y_offs, x_offs */
                { 6,  6,  -3,  -3}, // N
                { 6, 32,  -3, -16}, // NE
                { 6,  6,  -3,  -3}, // E
                {32,  6, -16,  -3}, // SE
                { 6,  6,  -3,  -3}, // S
                { 6, 32,  -3, -16}, // SW
                { 6,  6,  -3,  -3}, // W
                {32,  6, -16,  -3}, // NW
        };

        const int8 *bb = _delta_xy_table[direction];
        this->x_offs        = bb[3];
        this->y_offs        = bb[2];
        this->x_extent      = bb[1];
        this->y_extent      = bb[0];
        this->z_extent      = 6;
}

static bool CheckShipLeaveDepot(Ship *v)
{
        if (!v->IsChainInDepot()) return false;

        if (v->current_order.IsWaitTimetabled())
                v->HandleWaiting(false);
        if (v->current_order.IsType(OT_WAITING))
                return true;

        /* We are leaving a depot, but have to go to the exact same one; re-enter */
        if (v->current_order.IsType(OT_GOTO_DEPOT) &&
                        IsShipDepotTile(v->tile) && GetDepotIndex(v->tile) == v->current_order.GetDestination()) {
                VehicleEnterDepot(v);
                return true;
        }

        TileIndex tile = v->tile;
        Axis axis = GetShipDepotAxis(tile);

        DiagDirection north_dir = ReverseDiagDir(AxisToDiagDir(axis));
        TileIndex north_neighbour = TILE_ADD(tile, TileOffsByDiagDir(north_dir));
        DiagDirection south_dir = AxisToDiagDir(axis);
        TileIndex south_neighbour = TILE_ADD(tile, 2 * TileOffsByDiagDir(south_dir));

        TrackBits north_tracks = DiagdirReachesTracks(north_dir) & GetTileShipTrackStatus(north_neighbour);
        TrackBits south_tracks = DiagdirReachesTracks(south_dir) & GetTileShipTrackStatus(south_neighbour);
        if (north_tracks && south_tracks) {
                /* Ask pathfinder for best direction */
                bool reverse = false;
                bool path_found;
                switch (_settings_game.pf.pathfinder_for_ships) {
                        case VPF_OPF: reverse = OPFShipChooseTrack(v, north_neighbour, north_dir, north_tracks, path_found) == INVALID_TRACK; break; // OPF always allows reversing
                        case VPF_NPF: reverse = NPFShipCheckReverse(v); break;
                        case VPF_YAPF: reverse = YapfShipCheckReverse(v); break;
                        default: NOT_REACHED();
                }
                if (reverse) north_tracks = TRACK_BIT_NONE;
        }

        if (north_tracks) {
                /* Leave towards north */
                v->direction = DiagDirToDir(north_dir);
        } else if (south_tracks) {
                /* Leave towards south */
                v->direction = DiagDirToDir(south_dir);
        } else {
                /* Both ways blocked */
                return false;
        }

        v->state = AxisToTrackBits(axis);
        v->vehstatus &= ~VS_HIDDEN;

        v->cur_speed = 0;
        v->UpdateViewport(true, true);
        SetWindowDirty(WC_VEHICLE_DEPOT, v->tile);

        PlayShipSound(v);
        VehicleServiceInDepot(v);
        InvalidateWindowData(WC_VEHICLE_DEPOT, v->tile);
        SetWindowClassesDirty(WC_SHIPS_LIST);

        return false;
}

static bool ShipAccelerate(Vehicle *v)
{
        uint spd;
        byte t;

        spd = min(v->cur_speed + 1, v->vcache.cached_max_speed);
        spd = min(spd, v->current_order.GetMaxSpeed() * 2);

        /* updates statusbar only if speed have changed to save CPU time */
        if (spd != v->cur_speed) {
                v->cur_speed = spd;
                SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
        }

        /* Convert direction-independent speed into direction-dependent speed. (old movement method) */
        spd = v->GetOldAdvanceSpeed(spd);

        if (spd == 0) return false;
        if ((byte)++spd == 0) return true;

        v->progress = (t = v->progress) - (byte)spd;

        return (t < v->progress);
}

/**
 * Ship arrives at a dock. If it is the first time, send out a news item.
 * @param v  Ship that arrived.
 * @param st Station being visited.
 */
static void ShipArrivesAt(const Vehicle *v, Station *st)
{
        /* Check if station was ever visited before */
        if (!(st->had_vehicle_of_type & HVOT_SHIP)) {
                st->had_vehicle_of_type |= HVOT_SHIP;

                SetDParam(0, st->index);
                AddVehicleNewsItem(
                        STR_NEWS_FIRST_SHIP_ARRIVAL,
                        (v->owner == _local_company) ? NT_ARRIVAL_COMPANY : NT_ARRIVAL_OTHER,
                        v->index,
                        st->index
                );
                AI::NewEvent(v->owner, new ScriptEventStationFirstVehicle(st->index, v->index));
                Game::NewEvent(new ScriptEventStationFirstVehicle(st->index, v->index));
        }
}


/**
 * Runs the pathfinder to choose a track to continue along.
 *
 * @param v Ship to navigate
 * @param tile Tile, the ship is about to enter
 * @param enterdir Direction of entering
 * @param tracks Available track choices on \a tile
 * @return Track to choose, or INVALID_TRACK when to reverse.
 */
static Track ChooseShipTrack(Ship *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks)
{
        assert(IsValidDiagDirection(enterdir));

        bool path_found = true;
        Track track;
        switch (_settings_game.pf.pathfinder_for_ships) {
                case VPF_OPF: track = OPFShipChooseTrack(v, tile, enterdir, tracks, path_found); break;
                case VPF_NPF: track = NPFShipChooseTrack(v, tile, enterdir, tracks, path_found); break;
                case VPF_YAPF: track = YapfShipChooseTrack(v, tile, enterdir, tracks, path_found); break;
                default: NOT_REACHED();
        }

        v->HandlePathfindingResult(path_found);
        return track;
}

static inline TrackBits GetAvailShipTracks(TileIndex tile, DiagDirection dir)
{
        return GetTileShipTrackStatus(tile) & DiagdirReachesTracks(dir);
}

static const byte _ship_subcoord[4][6][3] = {
        {
                {15, 8, 1},
                { 0, 0, 0},
                { 0, 0, 0},
                {15, 8, 2},
                {15, 7, 0},
                { 0, 0, 0},
        },
        {
                { 0, 0, 0},
                { 8, 0, 3},
                { 7, 0, 2},
                { 0, 0, 0},
                { 8, 0, 4},
                { 0, 0, 0},
        },
        {
                { 0, 8, 5},
                { 0, 0, 0},
                { 0, 7, 6},
                { 0, 0, 0},
                { 0, 0, 0},
                { 0, 8, 4},
        },
        {
                { 0, 0, 0},
                { 8, 15, 7},
                { 0, 0, 0},
                { 8, 15, 6},
                { 0, 0, 0},
                { 7, 15, 0},
        }
};

/* Used for finding tile exit direction using the enter direction and following track */
static const DiagDirection _diagdir_tile_exit[TRACK_END][DIAGDIR_END] = {
        { DIAGDIR_NE     , INVALID_DIAGDIR, DIAGDIR_SW     , INVALID_DIAGDIR}, //       TRACK_X     = 0
        { INVALID_DIAGDIR, DIAGDIR_SE     , INVALID_DIAGDIR, DIAGDIR_NW     }, //       TRACK_Y     = 1
        { INVALID_DIAGDIR, DIAGDIR_NE     , DIAGDIR_NW     , INVALID_DIAGDIR}, //       TRACK_UPPER = 2
        { DIAGDIR_SE     , INVALID_DIAGDIR, INVALID_DIAGDIR, DIAGDIR_SW     }, //       TRACK_LOWER = 3
        { DIAGDIR_NW     , DIAGDIR_SW     , INVALID_DIAGDIR, INVALID_DIAGDIR}, //       TRACK_LEFT  = 4
        { INVALID_DIAGDIR, INVALID_DIAGDIR, DIAGDIR_SE     , DIAGDIR_NE     }  //       TRACK_RIGHT = 5
};

struct ShipCollideChecker {

        TrackBits track_bits; ///< Trackbits (track that was chosen by the pathfinder converted in trackbits.) .
        TileIndex tile;       ///< Tile of where ship was found, used to determine distance between ships.
};

/** Helper function for collision avoidance. */
static Vehicle *FindShipOnTile(Vehicle *v, void *data)
{
        if (v->type != VEH_SHIP || v->vehstatus & VS_STOPPED) return NULL;
 
        ShipCollideChecker *scc = (ShipCollideChecker*)data;
        scc->tile = v->tile;

        /* Don't detect vehicles on different parallel tracks. */
        TrackBits bits = scc->track_bits | Ship::From(v)->state;
        if (bits == TRACK_BIT_HORZ || bits == TRACK_BIT_VERT) return NULL;

        return v;
}
 
/**
 * If there is imminent collision or worse, direction and speed will be adjusted.
 * @param tile    Tile that the ship is about to enter.
 * @param v       Ship that does the request.
 * @param tracks  The available tracks that could be followed.
 * @param track   The track that the pathfinder assigned.
 * @param diagdir The DiagDirection that tile will be entered.
 * @return The new track if found.
 */
static void CheckDistanceBetweenShips(TileIndex tile, Ship *v, TrackBits tracks, Track *track_old, DiagDirection diagdir)
{
        if (!_settings_game.pf.forbid_90_deg) return;
        if (DistanceManhattan(v->dest_tile, tile) <= 3 && !v->current_order.IsType(OT_GOTO_WAYPOINT)) return; // No checking close to docks and depots.

        Track track = *track_old;

        TileIndex tile_plus_one = TileAddByDiagDir(tile, _diagdir_tile_exit[track][diagdir]);
        if (!IsValidTile(tile_plus_one)) tile_plus_one = tile;

        ShipCollideChecker scc;

        scc.track_bits = v->state;
        bool found = HasVehicleOnPos(tile_plus_one, &scc, &FindShipOnTile);
        scc.track_bits = TrackToTrackBits(track);
        if (!found) found = HasVehicleOnPos(tile, &scc, &FindShipOnTile);

        if (found) {

                /* Speed adjustment related to distance. */
                v->cur_speed /= scc.tile == tile_plus_one ? 2 : 4;

                switch (tracks) {
                        default: break;
                        case TRACK_BIT_3WAY_NE: track == TRACK_RIGHT ? track = TRACK_X : track = TRACK_UPPER; break;
                        case TRACK_BIT_3WAY_SE: track == TRACK_LOWER ? track = TRACK_Y : track = TRACK_RIGHT; break;
                        case TRACK_BIT_3WAY_SW: track == TRACK_LEFT  ? track = TRACK_X : track = TRACK_LOWER; break;
                        case TRACK_BIT_3WAY_NW: track == TRACK_UPPER ? track = TRACK_Y : track = TRACK_LEFT;  break;
                }
                /* Don't bump in coast, don't get stuck. */
                if (track != *track_old && !IsWaterTile(TileAddByDiagDir(tile, _diagdir_tile_exit[track][diagdir]))) return;
                *track_old = track;
        }
}

static void ShipController(Ship *v)
{
        uint32 r;
        const byte *b;
        Direction dir;
        Track track;
        TrackBits tracks;

        v->tick_counter++;
        v->current_order_time++;

        if (v->HandleBreakdown()) return;

        if (v->vehstatus & VS_STOPPED) return;

        ProcessOrders(v);
        v->HandleLoading();

        if (v->current_order.IsType(OT_LOADING)) return;

        if (CheckShipLeaveDepot(v)) return;

        v->ShowVisualEffect();

        if (!ShipAccelerate(v)) return;

        GetNewVehiclePosResult gp = GetNewVehiclePos(v);
        if (v->state != TRACK_BIT_WORMHOLE) {
                /* Not on a bridge */
                if (gp.old_tile == gp.new_tile) {
                        /* Staying in tile */
                        if (v->IsInDepot()) {
                                gp.x = v->x_pos;
                                gp.y = v->y_pos;
                        } else {
                                /* Not inside depot */
                                r = VehicleEnterTile(v, gp.new_tile, gp.x, gp.y);
                                if (HasBit(r, VETS_CANNOT_ENTER)) goto reverse_direction;

                                /* A leave station order only needs one tick to get processed, so we can
                                 * always skip ahead. */
                                if (v->current_order.IsType(OT_LEAVESTATION)) {
                                        v->current_order.Free();
                                        SetWindowWidgetDirty(WC_VEHICLE_VIEW, v->index, WID_VV_START_STOP);
                                } else if (v->dest_tile != 0) {
                                        /* We have a target, let's see if we reached it... */
                                        if (v->current_order.IsType(OT_GOTO_WAYPOINT) &&
                                                        DistanceManhattan(v->dest_tile, gp.new_tile) <= 3) {
                                                /* We got within 3 tiles of our target buoy, so let's skip to our
                                                 * next order */
                                                UpdateVehicleTimetable(v, true);
                                                v->IncrementRealOrderIndex();
                                                v->current_order.MakeDummy();
                                        } else {
                                                /* Non-buoy orders really need to reach the tile */
                                                if (v->dest_tile == gp.new_tile) {
                                                        if (v->current_order.IsType(OT_GOTO_DEPOT)) {
                                                                if ((gp.x & 0xF) == 8 && (gp.y & 0xF) == 8) {
                                                                        VehicleEnterDepot(v);
                                                                        return;
                                                                }
                                                        } else if (v->current_order.IsType(OT_GOTO_STATION)) {
                                                                v->last_station_visited = v->current_order.GetDestination();

                                                                /* Process station in the orderlist. */
                                                                Station *st = Station::Get(v->current_order.GetDestination());
                                                                if (st->facilities & FACIL_DOCK) { // ugly, ugly workaround for problem with ships able to drop off cargo at wrong stations
                                                                        ShipArrivesAt(v, st);
                                                                        v->BeginLoading();
                                                                } else { // leave stations without docks right aways
                                                                        v->current_order.MakeLeaveStation();
                                                                        v->IncrementRealOrderIndex();
                                                                }
                                                        }
                                                }
                                        }
                                }
                        }
                } else {
                        /* New tile */
                        if (!IsValidTile(gp.new_tile)) goto reverse_direction;

                        DiagDirection diagdir = DiagdirBetweenTiles(gp.old_tile, gp.new_tile);
                        assert(diagdir != INVALID_DIAGDIR);
                        tracks = GetAvailShipTracks(gp.new_tile, diagdir);
                        if (tracks == TRACK_BIT_NONE) goto reverse_direction;

                        /* Choose a direction, and continue if we find one */
                        track = ChooseShipTrack(v, gp.new_tile, diagdir, tracks);
                        if (track == INVALID_TRACK) goto reverse_direction;

                        /* Try to avoid collision and keep distance between ships. */
                        CheckDistanceBetweenShips(gp.new_tile, v, tracks, &track, diagdir);

                        b = _ship_subcoord[diagdir][track];

                        gp.x = (gp.x & ~0xF) | b[0];
                        gp.y = (gp.y & ~0xF) | b[1];

                        /* Call the landscape function and tell it that the vehicle entered the tile */
                        r = VehicleEnterTile(v, gp.new_tile, gp.x, gp.y);
                        if (HasBit(r, VETS_CANNOT_ENTER)) goto reverse_direction;

                        if (!HasBit(r, VETS_ENTERED_WORMHOLE)) {
                                v->tile = gp.new_tile;
                                v->state = TrackToTrackBits(track);

                                /* Update ship cache when the water class changes. Aqueducts are always canals. */
                                WaterClass old_wc = GetEffectiveWaterClass(gp.old_tile);
                                WaterClass new_wc = GetEffectiveWaterClass(gp.new_tile);
                                if (old_wc != new_wc) v->UpdateCache();
                        }

                        v->direction = (Direction)b[2];
                }
        } else {
                /* On a bridge */
                if (!IsTileType(gp.new_tile, MP_TUNNELBRIDGE) || !HasBit(VehicleEnterTile(v, gp.new_tile, gp.x, gp.y), VETS_ENTERED_WORMHOLE)) {
                        v->x_pos = gp.x;
                        v->y_pos = gp.y;
                        v->UpdatePosition();
                        if ((v->vehstatus & VS_HIDDEN) == 0) v->Vehicle::UpdateViewport(true);
                        return;
                }
        }

        /* update image of ship, as well as delta XY */
        v->x_pos = gp.x;
        v->y_pos = gp.y;
        v->z_pos = GetSlopePixelZ(gp.x, gp.y);

getout:
        v->UpdatePosition();
        v->UpdateViewport(true, true);
        return;

reverse_direction:
        dir = ReverseDir(v->direction);
        v->direction = dir;
        goto getout;
}

bool Ship::Tick()
{
        if (!((this->vehstatus & VS_STOPPED) || this->IsChainInDepot())) this->running_ticks++;

        ShipController(this);

        return true;
}

/**
 * Build a ship.
 * @param tile     tile of the depot where ship is built.
 * @param flags    type of operation.
 * @param e        the engine to build.
 * @param data     unused.
 * @param ret[out] the vehicle that has been built.
 * @return the cost of this operation or an error.
 */
CommandCost CmdBuildShip(TileIndex tile, DoCommandFlag flags, const Engine *e, uint16 data, Vehicle **ret)
{
        tile = GetShipDepotNorthTile(tile);
        if (flags & DC_EXEC) {
                int x;
                int y;

                const ShipVehicleInfo *svi = &e->u.ship;

                Ship *v = new Ship();
                *ret = v;

                v->owner = _current_company;
                v->tile = tile;
                x = TileX(tile) * TILE_SIZE + TILE_SIZE / 2;
                y = TileY(tile) * TILE_SIZE + TILE_SIZE / 2;
                v->x_pos = x;
                v->y_pos = y;
                v->z_pos = GetSlopePixelZ(x, y);

                v->UpdateDeltaXY(v->direction);
                v->vehstatus = VS_HIDDEN | VS_STOPPED | VS_DEFPAL;

                v->spritenum = svi->image_index;
                v->cargo_type = e->GetDefaultCargoType();
                v->cargo_cap = svi->capacity;
                v->refit_cap = 0;

                v->last_station_visited = INVALID_STATION;
                v->last_loading_station = INVALID_STATION;
                v->engine_type = e->index;

                v->reliability = e->reliability;
                v->reliability_spd_dec = e->reliability_spd_dec;
                v->max_age = e->GetLifeLengthInDays();
                _new_vehicle_id = v->index;

                v->state = TRACK_BIT_DEPOT;

                v->SetServiceInterval(Company::Get(_current_company)->settings.vehicle.servint_ships);
                v->date_of_last_service = _date;
                v->build_year = _cur_year;
                v->sprite_seq.Set(SPR_IMG_QUERY);
                v->random_bits = VehicleRandomBits();

                v->UpdateCache();

                if (e->flags & ENGINE_EXCLUSIVE_PREVIEW) SetBit(v->vehicle_flags, VF_BUILT_AS_PROTOTYPE);
                v->SetServiceIntervalIsPercent(Company::Get(_current_company)->settings.vehicle.servint_ispercent);

                v->InvalidateNewGRFCacheOfChain();

                v->cargo_cap = e->DetermineCapacity(v);

                v->InvalidateNewGRFCacheOfChain();

                v->UpdatePosition();
        }

        return CommandCost();
}

bool Ship::FindClosestDepot(TileIndex *location, DestinationID *destination, bool *reverse)
{
        const Depot *depot = FindClosestShipDepot(this, 0);

        if (depot == NULL) return false;

        if (location    != NULL) *location    = depot->xy;
        if (destination != NULL) *destination = depot->index;

        return true;
}