Merge PR #272 (public roads) into jgrpp

src/genworld.cpp

@@ -42,6 +42,7 @@ void GenerateClearTile();
 void GenerateIndustries();
 void GenerateObjects();
 void GenerateTrees();
+void GeneratePublicRoads();
 
 void StartupEconomy();
 void StartupCompanies();
@@ -140,6 +141,7 @@ static void _GenerateWorld()
 				GenerateIndustries();
 				GenerateObjects();
 				GenerateTrees();
+				GeneratePublicRoads();
 			}
 		}
 

src/genworld.h

@@ -78,6 +78,7 @@ enum GenWorldProgress {
 	GWP_INDUSTRY,    ///< Generate industries
 	GWP_OBJECT,      ///< Generate objects (radio tower, light houses)
 	GWP_TREE,        ///< Generate trees
+	GWP_PUBLIC_ROADS,///< Generate public roads
 	GWP_GAME_INIT,   ///< Initialize the game
 	GWP_RUNTILELOOP, ///< Runs the tile loop 1280 times to make snow etc
 	GWP_RUNSCRIPT,   ///< Runs the game script at most 2500 times, or when ever the script sleeps

src/genworld_gui.cpp

@@ -1462,6 +1462,7 @@ static const StringID _generation_class_table[]  = {
 	STR_SCENEDIT_TOOLBAR_INDUSTRY_GENERATION,
 	STR_GENERATION_OBJECT_GENERATION,
 	STR_GENERATION_TREE_GENERATION,
+	STR_GENERATION_PUBLIC_ROADS_GENERATION,
 	STR_GENERATION_SETTINGUP_GAME,
 	STR_GENERATION_PREPARING_TILELOOP,
 	STR_GENERATION_PREPARING_SCRIPT,
@@ -1568,7 +1569,7 @@ void ShowGenerateWorldProgress()
 
 static void _SetGeneratingWorldProgress(GenWorldProgress cls, uint progress, uint total)
 {
-	static const int percent_table[] = {0, 5, 14, 17, 20, 40, 60, 65, 80, 85, 95, 99, 100 };
+	static const int percent_table[] = {0, 7, 14, 22, 29, 36, 44, 51, 58, 65, 73, 80, 90, 100 };
 	static_assert(lengthof(percent_table) == GWP_CLASS_COUNT + 1);
 	assert(cls < GWP_CLASS_COUNT);
 

src/landscape.cpp

@@ -1209,15 +1209,7 @@ static bool RiverMakeWider(TileIndex tile, void *data)
 /* AyStar callback when an route has been found. */
 static void River_FoundEndNode(AyStar *aystar, OpenListNode *current)
 {
-	/* Count river length. */
-	uint length = 0;
-
 	for (PathNode *path = &current->path; path != nullptr; path = path->parent) {
-		length++;
-	}
-
-	uint cur_pos = 0;
-	for (PathNode *path = &current->path; path != nullptr; path = path->parent, cur_pos++) {
 		TileIndex tile = path->node.tile;
 		if (!IsWaterTile(tile)) {
 			MakeRiver(tile, Random());
@@ -1241,17 +1233,6 @@ static void River_FoundEndNode(AyStar *aystar, OpenListNode *current)
 
 static const uint RIVER_HASH_SIZE = 8; ///< The number of bits the hash for river finding should have.
 
-/**
- * Simple hash function for river tiles to be used by AyStar.
- * @param tile The tile to hash.
- * @param dir The unused direction.
- * @return The hash for the tile.
- */
-static uint River_Hash(uint tile, uint dir)
-{
-	return GB(TileHash(TileX(tile), TileY(tile)), 0, RIVER_HASH_SIZE);
-}
-
 /**
  * Actually build the river between the begin and end tiles using AyStar.
  * @param begin The begin of the river.
@@ -1267,7 +1248,7 @@ static void BuildRiver(TileIndex begin, TileIndex end)
 	finder.FoundEndNode = River_FoundEndNode;
 	finder.user_target = &end;
 
-	finder.Init(River_Hash, 1 << RIVER_HASH_SIZE);
+	finder.Init(1 << RIVER_HASH_SIZE);
 
 	AyStarNode start;
 	start.tile = begin;

src/lang/english.txt

@@ -1931,6 +1931,12 @@ STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_HELPTEXT               :Adjust placemen
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE                  :Arctic tree range: {STRING2}
 STR_CONFIG_SETTING_TREES_AROUND_SNOWLINE_RANGE_HELPTEXT         :Approximate range of arctic trees around snow line
 
+STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS                           :Build public roads connecting towns: {STRING2}
+STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_HELPTEXT                  :Generates public roads which connect the towns. Takes a bit of time on bigger maps. 'Build and avoid' generates roads which avoid curves and result in very grid-like connections.
+STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_NONE                      :None (Default)
+STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_WITH_CURVES               :Build with curves
+STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_AVOID_CURVES              :Build and avoid curves
+
 STR_CONFIG_SETTING_TREE_GROWTH                                  :Tree growth speed: {STRING2}
 STR_CONFIG_SETTING_TREE_GROWTH_HELPTEXT                         :Control rate at which trees grow during the game. This might affect industries which rely on tree growth, for example lumber mills
 STR_CONFIG_SETTING_TREE_GROWTH_NORMAL                           :Normal
@@ -3390,6 +3396,8 @@ STR_TERRAFORM_TOOLTIP_GENERATE_RANDOM_LAND                      :{BLACK}Generate
 STR_TERRAFORM_SE_NEW_WORLD                                      :{BLACK}Create new scenario
 STR_TERRAFORM_RESET_LANDSCAPE                                   :{BLACK}Reset landscape
 STR_TERRAFORM_RESET_LANDSCAPE_TOOLTIP                           :{BLACK}Remove all company-owned property from the map
+STR_TERRAFORM_PUBLIC_ROADS                                      :{BLACK}Build public roads
+STR_TERRAFORM_PUBLIC_ROADS_TOOLTIP                              :{BLACK}Build public roads between the towns on the map
 
 STR_QUERY_RESET_LANDSCAPE_CAPTION                               :{WHITE}Reset Landscape
 STR_RESET_LANDSCAPE_CONFIRMATION_TEXT                           :{WHITE}Are you sure you want to remove all company-owned property?
@@ -3774,6 +3782,7 @@ STR_GENERATION_PROGRESS_NUM                                     :{BLACK}{NUM} /
 STR_GENERATION_WORLD_GENERATION                                 :{BLACK}World generation
 STR_GENERATION_RIVER_GENERATION                                 :{BLACK}River generation
 STR_GENERATION_TREE_GENERATION                                  :{BLACK}Tree generation
+STR_GENERATION_PUBLIC_ROADS_GENERATION                          :{BLACK}Public roads generation
 STR_GENERATION_OBJECT_GENERATION                                :{BLACK}Object generation
 STR_GENERATION_CLEARING_TILES                                   :{BLACK}Rough and rocky area generation
 STR_GENERATION_SETTINGUP_GAME                                   :{BLACK}Setting up game

src/map_func.h

@@ -399,6 +399,13 @@ static inline TileIndex TileAddByDiagDir(TileIndex tile, DiagDirection dir)
 	return TILE_ADD(tile, TileOffsByDiagDir(dir));
 }
 
+/** Checks if two tiles are adjacent */
+static inline bool AreTilesAdjacent(TileIndex a, TileIndex b)
+{
+	return (std::abs((int)TileX(a) - (int)TileX(b)) <= 1) &&
+		   (std::abs((int)TileY(a) - (int)TileY(b)) <= 1);
+}
+
 /**
  * Determines the DiagDirection to get from one tile to another.
  * The tiles do not necessarily have to be adjacent.

src/pathfinder/npf/aystar.cpp

@@ -26,6 +26,7 @@
 #include "aystar.h"
 
 #include "../../safeguards.h"
+#include "core/mem_func.hpp"
 
 /**
  * This looks in the hash whether a node exists in the closed list.
@@ -34,7 +35,9 @@
  */
 PathNode *AyStar::ClosedListIsInList(const AyStarNode *node)
 {
-	return (PathNode*)this->closedlist_hash.Get(node->tile, node->direction);
+	const auto result = this->closedlist_hash.find(std::make_pair(node->tile, node->direction));
+
+	return (result == this->closedlist_hash.end()) ? nullptr : result->second;
 }
 
 /**
@@ -45,9 +48,10 @@ PathNode *AyStar::ClosedListIsInList(const AyStarNode *node)
 void AyStar::ClosedListAdd(const PathNode *node)
 {
 	/* Add a node to the ClosedList */
-	PathNode *new_node = MallocT<PathNode>(1);
+	const auto new_node = MallocT<PathNode>(1);
 	*new_node = *node;
-	this->closedlist_hash.Set(node->node.tile, node->node.direction, new_node);
+
+	this->closedlist_hash[std::make_pair(node->node.tile, node->node.direction)] = new_node;
 }
 
 /**
@@ -57,7 +61,9 @@ void AyStar::ClosedListAdd(const PathNode *node)
  */
 OpenListNode *AyStar::OpenListIsInList(const AyStarNode *node)
 {
-	return (OpenListNode*)this->openlist_hash.Get(node->tile, node->direction);
+	const auto result = this->openlist_hash.find(std::make_pair(node->tile, node->direction));
+
+	return (result == this->openlist_hash.end()) ? nullptr : result->second;
 }
 
 /**
@@ -70,7 +76,7 @@ OpenListNode *AyStar::OpenListPop()
 	/* Return the item the Queue returns.. the best next OpenList item. */
 	OpenListNode *res = (OpenListNode*)this->openlist_queue.Pop();
 	if (res != nullptr) {
-		this->openlist_hash.DeleteValue(res->path.node.tile, res->path.node.direction);
+		this->openlist_hash.erase(std::make_pair(res->path.node.tile, res->path.node.direction));
 	}
 
 	return res;
@@ -87,7 +93,7 @@ void AyStar::OpenListAdd(PathNode *parent, const AyStarNode *node, int f, int g)
 	new_node->g = g;
 	new_node->path.parent = parent;
 	new_node->path.node = *node;
-	this->openlist_hash.Set(node->tile, node->direction, new_node);
+	this->openlist_hash[std::make_pair(node->tile, node->direction)] =  new_node;
 
 	/* Add it to the queue */
 	this->openlist_queue.Push(new_node, f);
@@ -132,8 +138,9 @@ void AyStar::CheckTile(AyStarNode *current, OpenListNode *parent)
 	if (check != nullptr) {
 		uint i;
 		/* Yes, check if this g value is lower.. */
-		if (new_g > check->g) return;
+		if (new_g >= check->g) return;
 		this->openlist_queue.Delete(check, 0);
+
 		/* It is lower, so change it to this item */
 		check->g = new_g;
 		check->path.parent = closedlist_parent;
@@ -191,7 +198,7 @@ int AyStar::Loop()
 	/* Free the node */
 	free(current);
 
-	if (this->max_search_nodes != 0 && this->closedlist_hash.GetSize() >= this->max_search_nodes) {
+	if (this->max_search_nodes != 0 && this->closedlist_hash.size() >= this->max_search_nodes) {
 		/* We've expanded enough nodes */
 		return AYSTAR_LIMIT_REACHED;
 	} else {
@@ -208,8 +215,14 @@ void AyStar::Free()
 	this->openlist_queue.Free(false);
 	/* 2nd argument above is false, below is true, to free the values only
 	 * once */
-	this->openlist_hash.Delete(true);
-	this->closedlist_hash.Delete(true);
+	for (const auto& pair : this->openlist_hash) {
+		free(pair.second);
+	}
+	this->openlist_hash.clear();
+	for (const auto& pair : this->closedlist_hash) {
+		free(pair.second);
+	}
+	this->closedlist_hash.clear();
 #ifdef AYSTAR_DEBUG
 	printf("[AyStar] Memory free'd\n");
 #endif
@@ -225,8 +238,15 @@ void AyStar::Clear()
 	 * the hash. */
 	this->openlist_queue.Clear(false);
 	/* Clean the hashes */
-	this->openlist_hash.Clear(true);
-	this->closedlist_hash.Clear(true);
+	for (const auto& pair : this->openlist_hash) {
+		free(pair.second);
+	}
+	this->openlist_hash.clear();
+
+	for (const auto& pair : this->closedlist_hash) {
+		free(pair.second);
+	}
+	this->closedlist_hash.clear();
 
 #ifdef AYSTAR_DEBUG
 	printf("[AyStar] Cleared AyStar\n");
@@ -290,11 +310,14 @@ void AyStar::AddStartNode(AyStarNode *start_node, uint g)
  * Initialize an #AyStar. You should fill all appropriate fields before
  * calling #Init (see the declaration of #AyStar for which fields are internal).
  */
-void AyStar::Init(Hash_HashProc hash, uint num_buckets)
+void AyStar::Init(uint num_buckets)
 {
+	MemSetT(&neighbours, 0);
+	MemSetT(&openlist_queue, 0);
+
 	/* Allocated the Hash for the OpenList and ClosedList */
-	this->openlist_hash.Init(hash, num_buckets);
-	this->closedlist_hash.Init(hash, num_buckets);
+	this->openlist_hash.reserve(num_buckets);
+	this->closedlist_hash.reserve(num_buckets);
 
 	/* Set up our sorting queue
 	 *  BinaryHeap allocates a block of 1024 nodes

src/pathfinder/npf/aystar.h

@@ -17,6 +17,9 @@
 #define AYSTAR_H
 
 #include "queue.h"
+#include <unordered_map>
+#include <memory>
+
 #include "../../tile_type.h"
 #include "../../track_type.h"
 
@@ -57,6 +60,15 @@ struct OpenListNode {
 	PathNode path;
 };
 
+struct PairHash {
+public:
+	template <typename T, typename U>
+	std::size_t operator()(const std::pair<T, U> &x) const
+	{
+		return std::hash<T>()(x.first) ^ std::hash<U>()(x.second);
+	}
+};
+
 bool CheckIgnoreFirstTile(const PathNode *node);
 
 struct AyStar;
@@ -144,7 +156,7 @@ struct AyStar {
 	AyStarNode neighbours[12];
 	byte num_neighbours;
 
-	void Init(Hash_HashProc hash, uint num_buckets);
+	void Init(uint num_buckets);
 
 	/* These will contain the methods for manipulating the AyStar. Only
 	 * Main() should be called externally */
@@ -156,9 +168,9 @@ struct AyStar {
 	void CheckTile(AyStarNode *current, OpenListNode *parent);
 
 protected:
-	Hash       closedlist_hash; ///< The actual closed list.
+	std::unordered_map<std::pair<TileIndex, Trackdir>, PathNode*, PairHash> closedlist_hash;
 	BinaryHeap openlist_queue;  ///< The open queue.
-	Hash       openlist_hash;   ///< An extra hash to speed up the process of looking up an element in the open list.
+	std::unordered_map<std::pair<TileIndex, Trackdir>, OpenListNode*, PairHash> openlist_hash;
 
 	void OpenListAdd(PathNode *parent, const AyStarNode *node, int f, int g);
 	OpenListNode *OpenListIsInList(const AyStarNode *node);

src/pathfinder/npf/npf.cpp

@@ -131,24 +131,6 @@ static uint NPFDistanceTrack(TileIndex t0, TileIndex t1)
 	return diagTracks * NPF_TILE_LENGTH + straightTracks * NPF_TILE_LENGTH * STRAIGHT_TRACK_LENGTH;
 }
 
-/**
- * Calculates a hash value for use in the NPF.
- * @param key1 The TileIndex of the tile to hash
- * @param key2 The Trackdir of the track on the tile.
- *
- * @todo Think of a better hash.
- */
-static uint NPFHash(uint key1, uint key2)
-{
-	/* TODO: think of a better hash? */
-	uint part1 = TileX(key1) & NPF_HASH_HALFMASK;
-	uint part2 = TileY(key1) & NPF_HASH_HALFMASK;
-
-	assert(IsValidTrackdir((Trackdir)key2));
-	assert(IsValidTile(key1));
-	return ((part1 << NPF_HASH_HALFBITS | part2) + (NPF_HASH_SIZE * key2 / TRACKDIR_END)) % NPF_HASH_SIZE;
-}
-
 static int32 NPFCalcZero(AyStar *as, AyStarNode *current, OpenListNode *parent)
 {
 	return 0;
@@ -1127,7 +1109,7 @@ void InitializeNPF()
 	static bool first_init = true;
 	if (first_init) {
 		first_init = false;
-		_npf_aystar.Init(NPFHash, NPF_HASH_SIZE);
+		_npf_aystar.Init(NPF_HASH_SIZE);
 	} else {
 		_npf_aystar.Clear();
 	}

src/road.cpp

@@ -8,6 +8,12 @@
 /** @file road.cpp Generic road related functions. */
 
 #include "stdafx.h"
+#include <algorithm>
+#include <memory>
+#include <numeric>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
 #include "rail_map.h"
 #include "road_map.h"
 #include "water_map.h"
@@ -18,13 +24,30 @@
 #include "date_func.h"
 #include "landscape.h"
 #include "road.h"
+#include "town.h"
+#include "pathfinder/npf/aystar.h"
+#include "tunnelbridge.h"
 #include "road_func.h"
 #include "roadveh.h"
+#include "map_func.h"
+#include "core/backup_type.hpp"
+#include "core/random_func.hpp"
 
+#include <numeric>
+
+#include "cheat_func.h"
+#include "command_func.h"
 #include "safeguards.h"
 
 uint32 _road_layout_change_counter = 0;
 
+/** Whether to build public roads */
+enum PublicRoadsConstruction {
+	PRC_NONE,         ///< Generate no public roads
+	PRC_WITH_CURVES,  ///< Generate roads with lots of curves
+	PRC_AVOID_CURVES, ///< Generate roads avoiding curves if possible
+};
+
 /**
  * Return if the tile is a valid tile for a crossing.
  *
@@ -303,3 +326,818 @@ RoadTypes ExistingRoadTypes(CompanyID c)
 
 	return known_roadtypes;
 }
+
+
+/* ========================================================================= */
+/*                                PUBLIC ROADS                               */
+/* ========================================================================= */
+
+CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text = nullptr);
+CommandCost CmdBuildTunnel(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text = nullptr);
+CommandCost CmdBuildRoad(TileIndex tile, DoCommandFlag flags, uint32 p1, uint32 p2, const char *text = nullptr);
+
+static std::vector<TileIndex> _town_centers;
+static std::vector<TileIndex> _towns_visited_along_the_way;
+static RoadType _public_road_type;
+static const uint _public_road_hash_size = 8U; ///< The number of bits the hash for river finding should have.
+
+/** Helper function to check if a slope along a certain direction is going up an inclined slope. */
+static bool IsUpwardsSlope(const Slope slope, DiagDirection road_direction)
+{
+	if (!IsInclinedSlope(slope)) return false;
+
+	const auto slope_direction = GetInclinedSlopeDirection(slope);
+
+	return road_direction == slope_direction;
+}
+
+/** Helper function to check if a slope along a certain direction is going down an inclined slope. */
+static bool IsDownwardsSlope(const Slope slope, const DiagDirection road_direction)
+{
+	if (!IsInclinedSlope(slope)) return false;
+
+	const auto slope_direction = GetInclinedSlopeDirection(slope);
+
+	return road_direction == ReverseDiagDir(slope_direction);
+}
+
+/** Helper function to check if a slope is effectively flat. */
+static bool IsSufficientlyFlatSlope(const Slope slope)
+{
+	return !IsSteepSlope(slope) && HasBit(VALID_LEVEL_CROSSING_SLOPES, slope);
+}
+
+static TileIndex BuildTunnel(PathNode *current, TileIndex end_tile = INVALID_TILE, const bool build_tunnel = false)
+{
+	const TileIndex start_tile = current->node.tile;
+	int start_z;
+	GetTileSlope(start_tile, &start_z);
+
+	if (start_z == 0) return INVALID_TILE;
+
+	const DiagDirection direction = GetInclinedSlopeDirection(GetTileSlope(start_tile));
+
+	if (!build_tunnel) {
+		// We are not building yet, so we still need to find the end_tile.
+		const TileIndexDiff delta = TileOffsByDiagDir(direction);
+		end_tile = start_tile;
+		int end_z;
+		const uint tunnel_length_limit = std::min<uint>(_settings_game.construction.max_tunnel_length, 30);
+
+		for (uint tunnel_length = 1;; tunnel_length++) {
+			end_tile += delta;
+
+			if (!IsValidTile(end_tile)) return INVALID_TILE;
+			if (tunnel_length > tunnel_length_limit) return INVALID_TILE;
+
+			GetTileSlope(end_tile, &end_z);
+
+			if (start_z == end_z) break;
+
+			if (!_cheats.crossing_tunnels.value && IsTunnelInWay(end_tile, start_z)) return INVALID_TILE;
+		}
+
+		// No too long or super-short tunnels and always ending up on a matching upwards slope.
+		if (IsSteepSlope(GetTileSlope(end_tile)) || IsHalftileSlope(GetTileSlope(end_tile))) return INVALID_TILE;
+		if (GetTileSlope(start_tile) != ComplementSlope(GetTileSlope(end_tile))) return INVALID_TILE;
+		if (AreTilesAdjacent(start_tile, end_tile)) return INVALID_TILE;
+		if (!IsValidTile(end_tile)) return INVALID_TILE;
+		if (!IsTileType(end_tile, MP_CLEAR) && !IsTileType(end_tile, MP_TREES)) return INVALID_TILE;
+	}
+
+	assert(!build_tunnel || (IsValidTile(end_tile) && GetTileSlope(start_tile) == ComplementSlope(GetTileSlope(end_tile))));
+
+	Backup cur_company(_current_company, OWNER_DEITY, FILE_LINE);
+	const auto build_tunnel_cmd = CmdBuildTunnel(start_tile, DC_AUTO | (build_tunnel ? DC_EXEC : DC_NONE), _public_road_type | (TRANSPORT_ROAD << 8), 0);
+	cur_company.Restore();
+
+	assert(!build_tunnel || build_tunnel_cmd.Succeeded());
+	assert(!build_tunnel || (IsTileType(start_tile, MP_TUNNELBRIDGE) && IsTileType(end_tile, MP_TUNNELBRIDGE)));
+
+	if (!build_tunnel_cmd.Succeeded()) return INVALID_TILE;
+
+	return end_tile;
+}
+
+static TileIndex BuildBridge(PathNode *current, TileIndex end_tile = INVALID_TILE, const bool build_bridge = false)
+{
+	const TileIndex start_tile = current->node.tile;
+
+	// We are not building yet, so we still need to find the end_tile.
+	// We will only build a bridge if we need to cross a river, so first check for that.
+	if (!build_bridge) {
+		const DiagDirection direction = ReverseDiagDir(GetInclinedSlopeDirection(GetTileSlope(start_tile)));
+
+		TileIndex tile = start_tile + TileOffsByDiagDir(direction);
+		const bool is_over_water = IsValidTile(tile) && IsTileType(tile, MP_WATER) && IsSea(tile);
+		uint bridge_length = 0;
+		const uint bridge_length_limit = std::min<uint>(_settings_game.construction.max_bridge_length, is_over_water ? 20 : 10);
+
+		// We are not building yet, so we still need to find the end_tile.
+		for (;
+			IsValidTile(tile) &&
+			(bridge_length <= bridge_length_limit) &&
+			(GetTileZ(start_tile) < (GetTileZ(tile) + _settings_game.construction.max_bridge_height)) &&
+			(GetTileZ(tile) <= GetTileZ(start_tile));
+			tile += TileOffsByDiagDir(direction), bridge_length++) {
+
+			auto is_complementary_slope =
+				!IsSteepSlope(GetTileSlope(tile)) &&
+				!IsHalftileSlope(GetTileSlope(tile)) &&
+				GetTileSlope(start_tile) == ComplementSlope(GetTileSlope(tile));
+
+			// No super-short bridges and always ending up on a matching upwards slope.
+			if (!AreTilesAdjacent(start_tile, tile) && is_complementary_slope) {
+				end_tile = tile;
+				break;
+			}
+		}
+
+		if (!IsValidTile(end_tile)) return INVALID_TILE;
+		if (GetTileSlope(start_tile) != ComplementSlope(GetTileSlope(end_tile))) return INVALID_TILE;
+		if (!IsTileType(end_tile, MP_CLEAR) && !IsTileType(end_tile, MP_TREES) && !IsCoastTile(end_tile)) return INVALID_TILE;
+	}
+
+	assert(!build_bridge || (IsValidTile(end_tile) && GetTileSlope(start_tile) == ComplementSlope(GetTileSlope(end_tile))));
+
+	const uint length = GetTunnelBridgeLength(start_tile, end_tile);
+
+	std::vector<BridgeType> available_bridge_types;
+	for (BridgeType i = 0; i < MAX_BRIDGES; ++i) {
+		if (MayTownBuildBridgeType(i) && CheckBridgeAvailability(i, length).Succeeded()) {
+			available_bridge_types.push_back(i);
+		}
+	}
+
+	assert(!build_bridge || !available_bridge_types.empty());
+	if (available_bridge_types.empty()) return INVALID_TILE;
+
+	const auto bridge_type = available_bridge_types[build_bridge ? RandomRange(uint32(available_bridge_types.size())) : 0];
+
+	Backup cur_company(_current_company, OWNER_DEITY, FILE_LINE);
+	const auto build_bridge_cmd = CmdBuildBridge(end_tile, DC_AUTO | (build_bridge ? DC_EXEC : DC_NONE), start_tile, bridge_type | (_public_road_type << 8) | (TRANSPORT_ROAD << 15));
+	cur_company.Restore();
+
+	assert(!build_bridge || build_bridge_cmd.Succeeded());
+	assert(!build_bridge || (IsTileType(start_tile, MP_TUNNELBRIDGE) && IsTileType(end_tile, MP_TUNNELBRIDGE)));
+
+	if (!build_bridge_cmd.Succeeded()) return INVALID_TILE;
+
+	return end_tile;
+}
+
+static TileIndex BuildRiverBridge(PathNode *current, const DiagDirection road_direction, TileIndex end_tile = INVALID_TILE, const bool build_bridge = false)
+{
+	const TileIndex start_tile = current->node.tile;
+	const int start_tile_z = GetTileMaxZ(start_tile);
+
+	if (!build_bridge) {
+		// We are not building yet, so we still need to find the end_tile.
+		// We will only build a bridge if we need to cross a river, so first check for that.
+		TileIndex tile = start_tile + TileOffsByDiagDir(road_direction);
+
+		if (!IsWaterTile(tile) || !IsRiver(tile)) return INVALID_TILE;
+
+		// Now let's see if we can bridge it. But don't bridge anything more than 4 river tiles. Cities aren't allowed to, so public roads we are not either.
+		// Only bridges starting at slopes should be longer ones. The others look like crap when built this way. Players can build them but the map generator
+		// should not force that on them. This is just to bridge rivers, not to make long bridges.
+		for (;
+			IsValidTile(tile) &&
+			(GetTunnelBridgeLength(start_tile, tile) <= std::min(_settings_game.construction.max_bridge_length, (uint16)3)) &&
+			(start_tile_z < (GetTileZ(tile) + _settings_game.construction.max_bridge_height)) &&
+			(GetTileZ(tile) <= start_tile_z);
+			tile += TileOffsByDiagDir(road_direction)) {
+
+			if ((IsTileType(tile, MP_CLEAR) || IsTileType(tile, MP_TREES) || IsCoastTile(tile)) &&
+					GetTileZ(tile) <= start_tile_z &&
+					IsSufficientlyFlatSlope(GetTileSlope(tile))) {
+				end_tile = tile;
+				break;
+			}
+		}
+
+		if (!IsValidTile(end_tile)) return INVALID_TILE;
+		if (!IsTileType(end_tile, MP_CLEAR) && !IsTileType(end_tile, MP_TREES) && !IsCoastTile(end_tile)) return INVALID_TILE;
+	}
+
+	assert(!build_bridge || IsValidTile(end_tile));
+
+	const uint length = GetTunnelBridgeLength(start_tile, end_tile);
+
+	std::vector<BridgeType> available_bridge_types;
+	for (BridgeType i = 0; i < MAX_BRIDGES; ++i) {
+		if (MayTownBuildBridgeType(i) && CheckBridgeAvailability(i, length).Succeeded()) {
+			available_bridge_types.push_back(i);
+		}
+	}
+
+	const auto bridge_type = available_bridge_types[build_bridge ? RandomRange(uint32(available_bridge_types.size())) : 0];
+
+	Backup cur_company(_current_company, OWNER_DEITY, FILE_LINE);
+	const auto build_bridge_cmd = CmdBuildBridge(end_tile, DC_AUTO | (build_bridge ? DC_EXEC : DC_NONE), start_tile, bridge_type | (_public_road_type << 8) | (TRANSPORT_ROAD << 15));
+	cur_company.Restore();
+
+	assert(!build_bridge || build_bridge_cmd.Succeeded());
+	assert(!build_bridge || (IsTileType(start_tile, MP_TUNNELBRIDGE) && IsTileType(end_tile, MP_TUNNELBRIDGE)));
+
+	if (!build_bridge_cmd.Succeeded()) return INVALID_TILE;
+
+	return end_tile;
+}
+
+static bool IsValidNeighbourOfPreviousTile(const TileIndex tile, const TileIndex previous_tile)
+{
+	if (!IsValidTile(tile) || (tile == previous_tile)) return false;
+
+	const auto forward_direction = DiagdirBetweenTiles(previous_tile, tile);
+
+	if (IsTileType(tile, MP_TUNNELBRIDGE))
+	{
+		if (GetOtherTunnelBridgeEnd(tile) == previous_tile) return true;
+
+		const auto tunnel_direction = GetTunnelBridgeDirection(tile);
+
+		return (tunnel_direction == forward_direction);
+	}
+
+	if (!IsTileType(tile, MP_CLEAR) && !IsTileType(tile, MP_TREES) && !IsTileType(tile, MP_ROAD) && !IsCoastTile(tile)) return false;
+
+	const Slope slope = GetTileSlope(tile);
+	if (IsSteepSlope(slope)) return false;
+
+	const Slope foundationSlope = GetFoundationSlope(tile);
+
+	/* Allow only trivial foundations (3 corners raised or 2 opposite corners raised -> flat) */
+	if (slope != foundationSlope && !HasBit(VALID_LEVEL_CROSSING_SLOPES, slope)) return false;
+
+	if (IsInclinedSlope(slope)) {
+		const auto slope_direction = GetInclinedSlopeDirection(slope);
+
+		if (slope_direction != forward_direction && ReverseDiagDir(slope_direction) != forward_direction) {
+			return false;
+		}
+	} else if (!HasBit(VALID_LEVEL_CROSSING_SLOPES, slope)) {
+		return false;
+	} else {
+		/* Check whether the previous tile was an inclined slope, and whether we are leaving the previous tile from a valid direction */
+		if (slope != SLOPE_FLAT) {
+			const Slope previous_slope = GetTileSlope(previous_tile);
+			if (IsInclinedSlope(previous_slope)) {
+				const DiagDirection slope_direction = GetInclinedSlopeDirection(previous_slope);
+				if (slope_direction != forward_direction && ReverseDiagDir(slope_direction) != forward_direction) return false;
+			}
+		}
+	}
+
+	return true;
+}
+
+static bool AreParallelOverlapping(const Point &start_a, const Point &end_a, const Point &start_b, const Point &end_b)
+{
+	// Check parallel overlaps.
+	if (start_a.x == end_a.x && start_b.x == end_b.x && start_a.x == start_b.x) {
+		if ((start_a.y <= start_b.y && end_a.y >= start_b.y) || (start_a.y >= start_b.y && end_a.y <= start_b.y) ||
+			(start_a.y <= end_b.y && end_a.y >= end_b.y) || (start_a.y >= end_b.y && end_a.y <= end_b.y)) {
+			return true;
+		}
+	}
+
+	if (start_a.y == end_a.y && start_b.y == end_b.y && start_a.y == start_b.y) {
+		if ((start_a.x <= start_b.x && end_a.x >= start_b.x) || (start_a.x >= start_b.x && end_a.x <= start_b.x) ||
+			(start_a.x <= end_b.x && end_a.x >= end_b.x) || (start_a.x >= end_b.x && end_a.x <= end_b.x)) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+static bool AreIntersecting(const Point &start_a, const Point &end_a, const Point &start_b, const Point &end_b)
+{
+	if (start_a.x == end_a.x && start_b.y == end_b.y) {
+		if ((start_b.x <= start_a.x && end_b.x >= start_a.x) || (start_b.x >= start_a.x && end_b.x <= start_a.x)) {
+			if ((start_a.y <= start_b.y && end_a.y >= start_b.y) || (start_a.y >= start_b.y && end_a.y <= start_b.y)) {
+				return true;
+			}
+		}
+	}
+
+	if (start_a.y == end_a.y && start_b.x == end_b.x) {
+		if ((start_b.y <= start_a.y && end_b.y >= start_a.y) || (start_b.y >= start_a.y && end_b.y <= start_a.y)) {
+			if ((start_a.x <= start_b.x && end_a.x >= start_b.x) || (start_a.x >= start_b.x && end_a.x <= start_b.x)) {
+				return true;
+			}
+		}
+	}
+
+	return false;
+}
+
+static bool IsBlockedByPreviousBridgeOrTunnel(OpenListNode *current, TileIndex start_tile, TileIndex end_tile)
+{
+	PathNode* start = &current->path;
+	PathNode* end = current->path.parent;
+
+	Point start_b {};
+	start_b.x = TileX(start_tile);
+	start_b.y = TileY(start_tile);
+	Point end_b {};
+	end_b.x = TileX(end_tile);
+	end_b.y = TileY(end_tile);
+
+	while (end != nullptr) {
+		Point start_a {};
+		start_a.x = TileX(start->node.tile);
+		start_a.y = TileY(start->node.tile);
+		Point end_a {};
+		end_a.x = TileX(end->node.tile);
+		end_a.y = TileY(end->node.tile);
+
+		if (!AreTilesAdjacent(start->node.tile, end->node.tile) &&
+			(AreIntersecting(start_a, end_a, start_b, end_b) || AreParallelOverlapping(start_a, end_a, start_b, end_b))) {
+			return true;
+		}
+
+		start = end;
+		end = start->parent;
+	}
+
+	return false;
+}
+
+/** AyStar callback for getting the neighbouring nodes of the given node. */
+static void PublicRoad_GetNeighbours(AyStar *aystar, OpenListNode *current)
+{
+	const auto current_tile = current->path.node.tile;
+	const auto previous_tile = current->path.parent != nullptr ? current->path.parent->node.tile : INVALID_TILE;
+	const auto forward_direction = DiagdirBetweenTiles(previous_tile, current_tile);
+
+	aystar->num_neighbours = 0;
+
+	// Check if we just went through a tunnel or a bridge.
+	if (IsValidTile(previous_tile) && !AreTilesAdjacent(current_tile, previous_tile)) {
+
+		// We went through a tunnel or bridge, this limits our options to proceed to only forward.
+		const TileIndex next_tile = current_tile + TileOffsByDiagDir(forward_direction);
+
+		if (IsValidNeighbourOfPreviousTile(next_tile, current_tile)) {
+			aystar->neighbours[aystar->num_neighbours].tile = next_tile;
+			aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+			aystar->num_neighbours++;
+		}
+	} else if (IsTileType(current_tile, MP_TUNNELBRIDGE)) {
+		// Handle existing tunnels and bridges
+		const auto tunnel_bridge_end = GetOtherTunnelBridgeEnd(current_tile);
+		aystar->neighbours[aystar->num_neighbours].tile = tunnel_bridge_end;
+		aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+		aystar->num_neighbours++;
+	} else {
+		// Handle regular neighbors.
+		for (DiagDirection d = DIAGDIR_BEGIN; d < DIAGDIR_END; d++) {
+			const auto neighbour = current_tile + TileOffsByDiagDir(d);
+
+			if (neighbour == previous_tile) {
+				continue;
+			}
+
+			if (IsValidNeighbourOfPreviousTile(neighbour, current_tile)) {
+				aystar->neighbours[aystar->num_neighbours].tile = neighbour;
+				aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+				aystar->num_neighbours++;
+			}
+		}
+
+		// Check if we can turn this into a tunnel or a bridge.
+		if (IsValidTile(previous_tile)) {
+			const Slope current_tile_slope = GetTileSlope(current_tile);
+			if (IsUpwardsSlope(current_tile_slope, forward_direction)) {
+				const TileIndex tunnel_end = BuildTunnel(&current->path);
+
+				if (IsValidTile(tunnel_end)) {
+					const Slope tunnel_end_slope = GetTileSlope(tunnel_end);
+					if (!IsBlockedByPreviousBridgeOrTunnel(current, current_tile, tunnel_end) &&
+							!IsSteepSlope(tunnel_end_slope) &&
+							!IsHalftileSlope(tunnel_end_slope) &&
+							(tunnel_end_slope == ComplementSlope(current_tile_slope))) {
+						assert(IsValidDiagDirection(DiagdirBetweenTiles(current_tile, tunnel_end)));
+						aystar->neighbours[aystar->num_neighbours].tile = tunnel_end;
+						aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+						aystar->num_neighbours++;
+					}
+				}
+			} else if (IsDownwardsSlope(current_tile_slope, forward_direction)) {
+				const TileIndex bridge_end = BuildBridge(&current->path, forward_direction);
+
+				if (IsValidTile(bridge_end)) {
+					const Slope bridge_end_slope = GetTileSlope(bridge_end);
+					if (!IsBlockedByPreviousBridgeOrTunnel(current, current_tile, bridge_end) &&
+							!IsSteepSlope(bridge_end_slope) &&
+							!IsHalftileSlope(bridge_end_slope) &&
+							(bridge_end_slope == ComplementSlope(current_tile_slope))) {
+						assert(IsValidDiagDirection(DiagdirBetweenTiles(current_tile, bridge_end)));
+						aystar->neighbours[aystar->num_neighbours].tile = bridge_end;
+						aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+						aystar->num_neighbours++;
+					}
+				}
+			} else if (IsSufficientlyFlatSlope(current_tile_slope)) {
+				// Check if we could bridge a river from a flat tile. Not looking pretty on the map but you gotta do what you gotta do.
+				const auto bridge_end = BuildRiverBridge(&current->path, forward_direction);
+				assert(!IsValidTile(bridge_end) || IsSufficientlyFlatSlope(GetTileSlope(bridge_end)));
+
+				if (IsValidTile(bridge_end) &&
+						!IsBlockedByPreviousBridgeOrTunnel(current, current_tile, bridge_end)) {
+					assert(IsValidDiagDirection(DiagdirBetweenTiles(current_tile, bridge_end)));
+					aystar->neighbours[aystar->num_neighbours].tile = bridge_end;
+					aystar->neighbours[aystar->num_neighbours].direction = INVALID_TRACKDIR;
+					aystar->num_neighbours++;
+				}
+			}
+		}
+	}
+}
+
+/** AyStar callback for checking whether we reached our destination. */
+static int32 PublicRoad_EndNodeCheck(const AyStar *aystar, const OpenListNode *current)
+{
+	// Mark towns visited along the way.
+	const auto search_result =
+		std::find(_town_centers.begin(), _town_centers.end(), current->path.node.tile);
+
+	if (search_result != _town_centers.end()) {
+		_towns_visited_along_the_way.push_back(current->path.node.tile);
+	}
+
+	return current->path.node.tile == *static_cast<TileIndex*>(aystar->user_target) ? AYSTAR_FOUND_END_NODE : AYSTAR_DONE;
+}
+
+/** AyStar callback when an route has been found. */
+static void PublicRoad_FoundEndNode(AyStar *aystar, OpenListNode *current)
+{
+	PathNode* child = nullptr;
+
+	for (PathNode *path = &current->path; path != nullptr; path = path->parent) {
+		const TileIndex tile = path->node.tile;
+
+		if (IsTileType(tile, MP_TUNNELBRIDGE)) {
+			// Just follow the path; infrastructure is already in place.
+			continue;
+		}
+
+		if (path->parent == nullptr || AreTilesAdjacent(tile, path->parent->node.tile)) {
+			RoadBits road_bits = ROAD_NONE;
+
+			if (child != nullptr) {
+				const TileIndex tile2 = child->node.tile;
+				road_bits |= DiagDirToRoadBits(DiagdirBetweenTiles(tile, tile2));
+			}
+			if (path->parent != nullptr) {
+				const TileIndex tile2 = path->parent->node.tile;
+				road_bits |= DiagDirToRoadBits(DiagdirBetweenTiles(tile, tile2));
+			}
+
+			if (child != nullptr || path->parent != nullptr) {
+				// Check if we need to build anything.
+				bool need_to_build_road = true;
+
+				if (IsTileType(tile, MP_ROAD)) {
+					const RoadBits existing_bits = GetRoadBits(tile, RTT_ROAD);
+					CLRBITS(road_bits, existing_bits);
+					if (road_bits == ROAD_NONE) need_to_build_road = false;
+				}
+
+				// If it is already a road and has the right bits, we are good. Otherwise build the needed ones.
+				if (need_to_build_road)
+				{
+					Backup cur_company(_current_company, OWNER_DEITY, FILE_LINE);
+					CmdBuildRoad(tile, DC_EXEC, _public_road_type << 4 | road_bits, 0);
+					cur_company.Restore();
+				}
+			}
+		} else {
+			// We only get here if we have a parent and we're not adjacent to it. River/Tunnel time!
+			const DiagDirection road_direction = DiagdirBetweenTiles(tile, path->parent->node.tile);
+
+			auto end_tile = INVALID_TILE;
+
+			const Slope tile_slope = GetTileSlope(tile);
+			if (IsUpwardsSlope(tile_slope, road_direction)) {
+				end_tile = BuildTunnel(path, path->parent->node.tile, true);
+				assert(IsValidTile(end_tile) && IsDownwardsSlope(GetTileSlope(end_tile), road_direction));
+			} else if (IsDownwardsSlope(tile_slope, road_direction)) {
+				// Provide the function with the end tile, since we already know it, but still check the result.
+				end_tile = BuildBridge(path, path->parent->node.tile, true);
+				assert(IsValidTile(end_tile) && IsUpwardsSlope(GetTileSlope(end_tile), road_direction));
+			} else {
+				// River bridge is the last possibility.
+				assert(IsSufficientlyFlatSlope(tile_slope));
+				end_tile = BuildRiverBridge(path, road_direction, path->parent->node.tile, true);
+				assert(IsValidTile(end_tile) && IsSufficientlyFlatSlope(GetTileSlope(end_tile)));
+			}
+		}
+
+		child = path;
+	}
+}
+
+static const int32 BASE_COST_PER_TILE  = 1;      // Cost for existing road or tunnel/bridge.
+static const int32 COST_FOR_NEW_ROAD   = 10;    // Cost for building a new road.
+static const int32 COST_FOR_SLOPE      = 50;     // Additional cost if the road heads up or down a slope.
+
+/** AyStar callback for getting the cost of the current node. */
+static int32 PublicRoad_CalculateG(AyStar *, AyStarNode *current, OpenListNode *parent)
+{
+	int32 cost = 0;
+
+	const int32 distance = DistanceManhattan(parent->path.node.tile, current->tile);
+
+	if (IsTileType(current->tile, MP_ROAD) || IsTileType(current->tile, MP_TUNNELBRIDGE)) {
+		cost += distance * BASE_COST_PER_TILE;
+	} else {
+		cost += distance * COST_FOR_NEW_ROAD;
+
+		if (GetTileMaxZ(parent->path.node.tile) != GetTileMaxZ(current->tile)) {
+			cost += COST_FOR_SLOPE;
+
+			auto current_node = &parent->path;
+			auto parent_node = parent->path.parent;
+
+			// Force the pathfinder to build serpentine roads by punishing every slope in the last couple of tiles.
+			for (int i = 0; i < 3; ++i) {
+				if (current_node == nullptr || parent_node == nullptr) {
+					break;
+				}
+
+				if (GetTileMaxZ(current_node->node.tile) != GetTileMaxZ(parent_node->node.tile)) {
+					cost += COST_FOR_SLOPE;
+				}
+
+				current_node = parent_node;
+				parent_node = current_node->parent;
+			}
+		}
+
+		if (distance > 1) {
+			// We are planning to build a bridge or tunnel. Make that a bit more expensive.
+			cost += 6 * COST_FOR_SLOPE;
+			cost += distance * 2 * COST_FOR_NEW_ROAD;
+		}
+	}
+
+	if (_settings_game.game_creation.build_public_roads == PRC_AVOID_CURVES &&
+		parent->path.parent != nullptr &&
+		DiagdirBetweenTiles(parent->path.parent->node.tile, parent->path.node.tile) != DiagdirBetweenTiles(parent->path.node.tile, current->tile)) {
+		cost += 1;
+	}
+
+	return cost;
+}
+
+/** AyStar callback for getting the estimated cost to the destination. */
+static int32 PublicRoad_CalculateH(AyStar *aystar, AyStarNode *current, OpenListNode *parent)
+{
+	return DistanceManhattan(*static_cast<TileIndex*>(aystar->user_target), current->tile) * BASE_COST_PER_TILE;
+}
+
+bool FindPath(AyStar& finder, const TileIndex from, TileIndex to)
+{
+	finder.CalculateG = PublicRoad_CalculateG;
+	finder.CalculateH = PublicRoad_CalculateH;
+	finder.GetNeighbours = PublicRoad_GetNeighbours;
+	finder.EndNodeCheck = PublicRoad_EndNodeCheck;
+	finder.FoundEndNode = PublicRoad_FoundEndNode;
+	finder.user_target = &(to);
+	finder.max_search_nodes = 1 << 20;
+
+	finder.Init(1 << _public_road_hash_size);
+
+	AyStarNode start {};
+	start.tile = from;
+	start.direction = INVALID_TRACKDIR;
+	finder.AddStartNode(&start, 0);
+
+	int result = AYSTAR_STILL_BUSY;
+
+	while (result == AYSTAR_STILL_BUSY) {
+		result = finder.Main();
+	}
+
+	const bool found_path = (result == AYSTAR_FOUND_END_NODE);
+
+	return found_path;
+}
+
+struct TownNetwork
+{
+	uint failures_to_connect {};
+	std::vector<TileIndex> towns;
+};
+
+void PostProcessNetworks(const std::vector<std::shared_ptr<TownNetwork>>& town_networks)
+{
+	for (auto network : town_networks) {
+		if (network->towns.size() <= 3) {
+			continue;
+		}
+
+		std::vector towns(network->towns);
+		
+		for (auto town_a : network->towns) {
+			std::sort(towns.begin(), towns.end(), [&](const TileIndex& a, const TileIndex& b) { return DistanceManhattan(a, town_a) < DistanceManhattan(b, town_a); });
+
+			const auto second_clostest_town = *(towns.begin() + 2);
+			const auto third_clostest_town = *(towns.begin() + 3);
+
+			AyStar finder {};
+			{
+				FindPath(finder, town_a, second_clostest_town);
+				finder.Clear();
+				FindPath(finder, town_a, third_clostest_town);
+			}
+			finder.Free();
+
+			IncreaseGeneratingWorldProgress(GWP_PUBLIC_ROADS);
+		}
+	}
+}
+
+/**
+* Build the public road network connecting towns using AyStar.
+*/
+void GeneratePublicRoads()
+{
+	if (_settings_game.game_creation.build_public_roads == PRC_NONE) return;
+
+	_town_centers.clear();
+	_towns_visited_along_the_way.clear();
+
+	std::vector<TileIndex> towns;
+	towns.clear();
+	{
+		for (const Town *town : Town::Iterate()) {
+			towns.push_back(town->xy);
+			_town_centers.push_back(town->xy);
+		}
+	}
+
+	if (towns.empty()) {
+		return;
+	}
+
+	SetGeneratingWorldProgress(GWP_PUBLIC_ROADS, uint(towns.size() * 2));
+
+	// Create a list of networks which also contain a value indicating how many times we failed to connect to them.
+	std::vector<std::shared_ptr<TownNetwork>> networks;
+	std::unordered_map<TileIndex, std::shared_ptr<TownNetwork>> town_to_network_map;
+
+	std::sort(towns.begin(), towns.end(), [&](auto a, auto b) { return DistanceFromEdge(a) > DistanceFromEdge(b); });
+
+	TileIndex main_town = *towns.begin();
+	towns.erase(towns.begin());
+
+	_public_road_type = GetTownRoadType(Town::GetByTile(main_town));
+	std::unordered_set<TileIndex> checked_towns;
+
+	auto main_network = std::make_shared<TownNetwork>();
+	main_network->towns.push_back(main_town);
+	main_network->failures_to_connect = 0;
+
+	networks.push_back(main_network);
+	town_to_network_map[main_town] = main_network;
+
+	IncreaseGeneratingWorldProgress(GWP_PUBLIC_ROADS);
+
+	auto town_network_distance = [](const TileIndex town, const std::shared_ptr<TownNetwork> &network) {
+		int32 best = INT32_MAX;
+		for (TileIndex t : network->towns) {
+			best = std::min<int32>(best, DistanceManhattan(t, town));
+		}
+		return best;
+	};
+
+	std::sort(towns.begin(), towns.end(), [&](auto a, auto b) { return DistanceManhattan(a, main_town) < DistanceManhattan(b, main_town); });
+
+	for (auto start_town : towns) {
+		// Check if we can connect to any of the networks.
+		_towns_visited_along_the_way.clear();
+
+		checked_towns.clear();
+
+		auto reachable_from_town = town_to_network_map.find(start_town);
+		bool found_path = false;
+
+		if (reachable_from_town != town_to_network_map.end()) {
+			auto reachable_network = reachable_from_town->second;
+
+			std::sort(reachable_network->towns.begin(), reachable_network->towns.end(), [&](auto a, auto b) { return DistanceManhattan(start_town, a) < DistanceManhattan(start_town, b); });
+
+			const TileIndex end_town = *reachable_network->towns.begin();
+			checked_towns.emplace(end_town);
+
+			AyStar finder {};
+			{
+				found_path = FindPath(finder, start_town, end_town);
+			}
+			finder.Free();
+
+			if (found_path) {
+				reachable_network->towns.push_back(start_town);
+				if (reachable_network->failures_to_connect > 0) {
+					reachable_network->failures_to_connect--;
+				}
+
+				for (const TileIndex visited_town : _towns_visited_along_the_way) {
+					town_to_network_map[visited_town] = reachable_network;
+				}
+
+			} else {
+				town_to_network_map.erase(reachable_from_town);
+				reachable_network->failures_to_connect++;
+			}
+		}
+
+		if (!found_path) {
+			// Sort networks by failed connection attempts, so we try the most likely one first.
+			std::sort(networks.begin(), networks.end(), [&](const std::shared_ptr<TownNetwork> &a, const std::shared_ptr<TownNetwork> &b) {
+				return town_network_distance(start_town, a) < town_network_distance(start_town, b);
+			});
+
+			auto can_reach = [&](const std::shared_ptr<TownNetwork> &network) {
+				if (reachable_from_town != town_to_network_map.end() && network.get() == reachable_from_town->second.get()) {
+					return false;
+				}
+
+				// Try to connect to the town in the network that is closest to us.
+				// If we can't connect to that one, we can't connect to any of them since they are all interconnected.
+				sort(network->towns.begin(), network->towns.end(), [&](auto a, auto b) { return DistanceManhattan(start_town, a) < DistanceManhattan(start_town, b); });
+				const TileIndex end_town = *network->towns.begin();
+
+				if (checked_towns.find(end_town) != checked_towns.end()) {
+					return false;
+				}
+
+				checked_towns.emplace(end_town);
+
+				AyStar finder {};
+				{
+					found_path = FindPath(finder, start_town, end_town);
+				}
+				finder.Free();
+
+				if (found_path) {
+					network->towns.push_back(start_town);
+					if (network->failures_to_connect > 0) {
+						network->failures_to_connect--;
+					}
+					town_to_network_map[start_town] = network;
+				} else {
+					network->failures_to_connect++;
+				}
+
+				return found_path;
+			};
+
+			std::vector<std::shared_ptr<TownNetwork>>::iterator networks_end;
+
+			if (networks.size() > 5) {
+				networks_end = networks.begin() + 5;
+			} else {
+				networks_end = networks.end();
+			}
+
+			std::vector<std::shared_ptr<TownNetwork>> sampled_networks;
+			std::copy(networks.begin(), networks_end, std::back_inserter(sampled_networks));
+			std::sort(sampled_networks.begin(), sampled_networks.end(), [&](const std::shared_ptr<TownNetwork> &a, const std::shared_ptr<TownNetwork> &b) {
+				return a->failures_to_connect < b->failures_to_connect;
+			});
+
+			if (!std::any_of(sampled_networks.begin(), sampled_networks.end(), can_reach)) {
+				// We failed so many networks, we are a separate network. Let future towns try to connect to us.
+				auto new_network = std::make_shared<TownNetwork>();
+				new_network->towns.push_back(start_town);
+				new_network->failures_to_connect = 0;
+
+				// We basically failed to connect to this many towns.
+				int towns_already_in_networks = std::accumulate(networks.begin(), networks.end(), 0, [&](int accumulator, const std::shared_ptr<TownNetwork> &network) {
+					return accumulator + static_cast<int>(network->towns.size());
+				});
+
+				new_network->failures_to_connect += towns_already_in_networks;
+				town_to_network_map[start_town] = new_network;
+				networks.push_back(new_network);
+
+				for (const TileIndex visited_town : _towns_visited_along_the_way) {
+					town_to_network_map[visited_town] = new_network;
+				}
+			}
+		}
+
+		IncreaseGeneratingWorldProgress(GWP_PUBLIC_ROADS);
+	}
+
+	PostProcessNetworks(networks);
+}
+
+/* ========================================================================= */
+/*                              END PUBLIC ROADS                             */
+/* ========================================================================= */

src/settings.cpp

@@ -1536,6 +1536,11 @@ static bool ChangeTrackTypeSortMode(int32 p1) {
 	return true;
 }
 
+static bool PublicRoadsSettingChange(int32 p1) {
+	InvalidateWindowClassesData(WC_SCEN_LAND_GEN);
+	return true;
+}
+
 /** Checks if any settings are set to incorrect values, and sets them to correct values in that case. */
 static void ValidateSettings()
 {

src/settings_gui.cpp

@@ -2036,6 +2036,7 @@ static SettingsContainer &GetSettingsTree()
 			genworld->Add(new SettingEntry("economy.initial_city_size"));
 			genworld->Add(new SettingEntry("economy.town_layout"));
 			genworld->Add(new SettingEntry("economy.town_min_distance"));
+			genworld->Add(new SettingEntry("game_creation.build_public_roads"));
 			genworld->Add(new SettingEntry("difficulty.industry_density"));
 			genworld->Add(new SettingEntry("gui.pause_on_newgame"));
 			genworld->Add(new SettingEntry("game_creation.ending_year"));

src/settings_type.h

@@ -388,6 +388,7 @@ struct GameCreationSettings {
 	bool   lakes_allowed_in_deserts;         ///< are lakes allowed in deserts?
 	uint8  amount_of_rocks;                  ///< the amount of rocks
 	uint8  height_affects_rocks;             ///< the affect that map height has on rocks
+	uint8  build_public_roads;               ///< build public roads connecting towns
 };
 
 /** Settings related to construction in-game */

src/table/settings.ini

@@ -63,6 +63,7 @@ static bool UpdateLinkgraphColours(int32 p1);
 static bool ClimateThresholdModeChanged(int32 p1);
 static bool VelocityUnitsChanged(int32 p1);
 static bool ChangeTrackTypeSortMode(int32 p1);
+static bool PublicRoadsSettingChange(int32 p1);
 
 static bool UpdateClientName(int32 p1);
 static bool UpdateServerPassword(int32 p1);
@@ -4072,10 +4073,23 @@ strhelp  = STR_CONFIG_SETTING_HEIGHT_ROCKS_HELPTEXT
 strval   = STR_JUST_COMMA
 patxname = ""rocks.game_creation.height_affects_rocks""
 
-;;game_creation.build_public_roads
-[SDT_NULL]
-length   = 1
+[SDT_XREF]
 extver   = SlXvFeatureTest(XSLFTO_AND, XSLFI_JOKERPP)
+xref     = ""game_creation.build_public_roads""
+
+[SDT_VAR]
+base     = GameSettings
+var      = game_creation.build_public_roads
+type     = SLE_UINT8
+guiflags = SGF_MULTISTRING | SGF_NEWGAME_ONLY | SGF_SCENEDIT_TOO
+def      = 0
+min      = 0
+max      = 2
+str      = STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS
+strhelp  = STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_HELPTEXT
+strval   = STR_CONFIG_SETTING_BUILD_PUBLIC_ROADS_NONE
+proc     = PublicRoadsSettingChange
+patxname = ""public_roads.game_creation.build_public_roads""
 
 ; locale
 

src/terraform_gui.cpp

@@ -572,7 +572,12 @@ static const NWidgetPart _nested_scen_edit_land_gen_widgets[] = {
 		NWidget(WWT_TEXTBTN, COLOUR_GREY, WID_ETT_NEW_SCENARIO), SetMinimalSize(160, 12),
 								SetFill(1, 0), SetDataTip(STR_TERRAFORM_SE_NEW_WORLD, STR_TERRAFORM_TOOLTIP_GENERATE_RANDOM_LAND), SetPadding(0, 2, 0, 2),
 		NWidget(WWT_TEXTBTN, COLOUR_GREY, WID_ETT_RESET_LANDSCAPE), SetMinimalSize(160, 12),
-								SetFill(1, 0), SetDataTip(STR_TERRAFORM_RESET_LANDSCAPE, STR_TERRAFORM_RESET_LANDSCAPE_TOOLTIP), SetPadding(1, 2, 2, 2),
+								SetFill(1, 0), SetDataTip(STR_TERRAFORM_RESET_LANDSCAPE, STR_TERRAFORM_RESET_LANDSCAPE_TOOLTIP), SetPadding(1, 2, 0, 2),
+		NWidget(NWID_SELECTION, INVALID_COLOUR, WID_ETT_SHOW_PUBLIC_ROADS),
+			NWidget(WWT_TEXTBTN, COLOUR_GREY, WID_ETT_PUBLIC_ROADS), SetMinimalSize(160, 12),
+									SetFill(1, 0), SetDataTip(STR_TERRAFORM_PUBLIC_ROADS, STR_TERRAFORM_PUBLIC_ROADS_TOOLTIP), SetPadding(1, 2, 0, 2),
+		EndContainer(),
+		NWidget(NWID_SPACER), SetMinimalSize(0, 2),
 	EndContainer(),
 };
 
@@ -617,8 +622,7 @@ struct ScenarioEditorLandscapeGenerationWindow : Window {
 	ScenarioEditorLandscapeGenerationWindow(WindowDesc *desc, WindowNumber window_number) : Window(desc)
 	{
 		this->CreateNestedTree();
-		NWidgetStacked *show_desert = this->GetWidget<NWidgetStacked>(WID_ETT_SHOW_PLACE_DESERT);
-		show_desert->SetDisplayedPlane(_settings_game.game_creation.landscape == LT_TROPIC ? 0 : SZSP_NONE);
+		this->SetButtonStates();
 		this->FinishInitNested(window_number);
 		this->last_user_action = WIDGET_LIST_END;
 	}
@@ -723,6 +727,12 @@ struct ScenarioEditorLandscapeGenerationWindow : Window {
 				ShowQuery(STR_QUERY_RESET_LANDSCAPE_CAPTION, STR_RESET_LANDSCAPE_CONFIRMATION_TEXT, nullptr, ResetLandscapeConfirmationCallback);
 				break;
 
+			case WID_ETT_PUBLIC_ROADS: { // Build public roads
+				extern void GeneratePublicRoads();
+				GeneratePublicRoads();
+				break;
+			}
+
 			default: NOT_REACHED();
 		}
 	}
@@ -798,6 +808,27 @@ struct ScenarioEditorLandscapeGenerationWindow : Window {
 		this->SetDirty();
 	}
 
+	/**
+	 * Some data on this window has become invalid.
+	 * @param data Information about the changed data.
+	 * @param gui_scope Whether the call is done from GUI scope. You may not do everything when not in GUI scope. See #InvalidateWindowData() for details.
+	 */
+	void OnInvalidateData(int data = 0, bool gui_scope = true) override
+	{
+		if (!gui_scope) return;
+
+		this->SetButtonStates();
+		this->ReInit();
+	}
+
+	void SetButtonStates()
+	{
+		NWidgetStacked *show_desert = this->GetWidget<NWidgetStacked>(WID_ETT_SHOW_PLACE_DESERT);
+		show_desert->SetDisplayedPlane(_settings_game.game_creation.landscape == LT_TROPIC ? 0 : SZSP_NONE);
+		NWidgetStacked *show_public_roads = this->GetWidget<NWidgetStacked>(WID_ETT_SHOW_PUBLIC_ROADS);
+		show_public_roads->SetDisplayedPlane(_settings_game.game_creation.build_public_roads != 0 ? 0 : SZSP_NONE);
+	}
+
 	static HotkeyList hotkeys;
 };
 

src/widgets/terraform_widget.h

@@ -28,6 +28,7 @@ enum TerraformToolbarWidgets {
 /** Widgets of the #ScenarioEditorLandscapeGenerationWindow class. */
 enum EditorTerraformToolbarWidgets {
 	WID_ETT_SHOW_PLACE_DESERT,                   ///< Should the place desert button be shown?
+	WID_ETT_SHOW_PUBLIC_ROADS,                   ///< Should the public roads button be shown?
 	WID_ETT_START,                               ///< Used for iterations.
 	WID_ETT_DOTS = WID_ETT_START,                ///< Invisible widget for rendering the terraform size on.
 	WID_ETT_BUTTONS_START,                       ///< Start of pushable buttons.
@@ -44,6 +45,7 @@ enum EditorTerraformToolbarWidgets {
 	WID_ETT_DECREASE_SIZE,                       ///< Downwards arrow button to decrease terraforming size.
 	WID_ETT_NEW_SCENARIO,                        ///< Button for generating a new scenario.
 	WID_ETT_RESET_LANDSCAPE,                     ///< Button for removing all company-owned property.
+	WID_ETT_PUBLIC_ROADS,                        ///< Button for creating public roads.
 };
 
 #endif /* WIDGETS_TERRAFORM_WIDGET_H */