Change: Scale towns/industries by amount of land tiles.

This stops a large map with lots of water being crammed with towns and
industries even when set to Very Low.

src/genworld.cpp

@@ -134,11 +134,13 @@ static void _GenerateWorld()
 			if (_game_mode != GM_MENU) FlatEmptyWorld(_settings_game.game_creation.se_flat_world_height);
 
 			ConvertGroundTilesIntoWaterTiles();
+			Map::CountLandTiles();
 			IncreaseGeneratingWorldProgress(GWP_OBJECT);
 
 			_settings_game.game_creation.snow_line_height = DEF_SNOWLINE_HEIGHT;
 		} else {
 			GenerateClearTile();
+			Map::CountLandTiles();
 
 			/* Only generate towns, tree and industries in newgame mode. */
 			if (_game_mode != GM_EDITOR) {

src/industry_cmd.cpp

@@ -43,6 +43,7 @@
 #include "industry_cmd.h"
 #include "landscape_cmd.h"
 #include "terraform_cmd.h"
+#include "map_func.h"
 #include "timer/timer.h"
 #include "timer/timer_game_calendar.h"
 #include "timer/timer_game_economy.h"
@@ -2356,7 +2357,7 @@ static uint GetNumberOfIndustries()
 
 	if (difficulty == ID_CUSTOM) return std::min<uint>(IndustryPool::MAX_SIZE, _settings_game.game_creation.custom_industry_number);
 
-	return std::min<uint>(IndustryPool::MAX_SIZE, Map::ScaleBySize(numof_industry_table[difficulty]));
+	return std::min<uint>(IndustryPool::MAX_SIZE, Map::ScaleByLandProportion(Map::ScaleBySize(numof_industry_table[difficulty])));
 }
 
 /**

src/map.cpp

@@ -24,6 +24,8 @@
 /* static */ uint Map::size;      ///< The number of tiles on the map
 /* static */ uint Map::tile_mask; ///< _map_size - 1 (to mask the mapsize)
 
+/* static */ uint Map::initial_land_count; ///< Initial number of land tiles on the map.
+
 /* static */ std::unique_ptr<Tile::TileBase[]> Tile::base_tiles; ///< Base tiles of the map
 /* static */ std::unique_ptr<Tile::TileExtended[]> Tile::extended_tiles; ///< Extended tiles of the map
 
@@ -59,6 +61,15 @@
 	AllocateWaterRegions();
 }
 
+/* static */ void Map::CountLandTiles()
+{
+	/* Count number of tiles that are land. */
+	Map::initial_land_count = 0;
+	for (const auto tile : Map::Iterate()) {
+		Map::initial_land_count += IsWaterTile(tile) ? 0 : 1;
+	}
+}
+
 
 #ifdef _DEBUG
 TileIndex TileAdd(TileIndex tile, TileIndexDiff offset)

src/map_func.h

@@ -239,8 +239,11 @@ private:
 	static uint size;      ///< The number of tiles on the map
 	static uint tile_mask; ///< _map_size - 1 (to mask the mapsize)
 
+	static uint initial_land_count; ///< Initial number of land tiles on the map.
+
 public:
 	static void Allocate(uint size_x, uint size_y);
+	static void CountLandTiles();
 
 	/**
 	 * Logarithm of the map size along the X side.
@@ -307,6 +310,16 @@ public:
 		return Map::SizeY() - 1;
 	}
 
+	/**
+	 * Scales the given value by the number of water tiles.
+	 * @param n the value to scale
+	 * @return the scaled size
+	 */
+	static inline uint ScaleByLandProportion(uint n)
+	{
+		/* Use 64-bit arithmetic to avoid overflow. */
+		return static_cast<uint>(static_cast<uint64_t>(n) * Map::initial_land_count / Map::size);
+	}
 
 	/**
 	 * 'Wraps' the given "tile" so it is within the map.

src/town_cmd.cpp

@@ -53,6 +53,7 @@
 #include "road_cmd.h"
 #include "terraform_cmd.h"
 #include "tunnelbridge_cmd.h"
+#include "map_func.h"
 #include "timer/timer.h"
 #include "timer/timer_game_calendar.h"
 #include "timer/timer_game_economy.h"
@@ -2424,7 +2425,7 @@ bool GenerateTowns(TownLayout layout)
 {
 	uint current_number = 0;
 	uint difficulty = (_game_mode != GM_EDITOR) ? _settings_game.difficulty.number_towns : 0;
-	uint total = (difficulty == (uint)CUSTOM_TOWN_NUMBER_DIFFICULTY) ? _settings_game.game_creation.custom_town_number : Map::ScaleBySize(_num_initial_towns[difficulty] + (Random() & 7));
+	uint total = (difficulty == (uint)CUSTOM_TOWN_NUMBER_DIFFICULTY) ? _settings_game.game_creation.custom_town_number : Map::ScaleByLandProportion(Map::ScaleBySize(_num_initial_towns[difficulty] + (Random() & 7)));
 	total = std::min<uint>(TownPool::MAX_SIZE, total);
 	uint32_t townnameparts;
 	TownNames town_names;