(svn r11773) -Codechange: move some non-clear-land functions from clear_cmd.cpp to a more correct location.

6 files changed, 469 insertions, 456 deletions

diff --git a/src/clear_cmd.cpp b/src/clear_cmd.cpp
index 73183c504..d7c7e7e49 100644
--- a/src/clear_cmd.cpp
+++ b/src/clear_cmd.cpp
@@ -5,13 +5,10 @@
 #include "stdafx.h"
 #include "openttd.h"
 #include "clear_map.h"
-#include "rail_map.h"
 #include "table/strings.h"
 #include "player.h"
 #include "viewport.h"
 #include "command_func.h"
-#include "tunnel_map.h"
-#include "bridge_map.h"
 #include "bridge.h"
 #include "landscape.h"
 #include "variables.h"
@@ -23,431 +20,7 @@
 #include "tile_cmd.h"
 #include "functions.h"
 #include "economy_func.h"
-#include "vehicle_func.h"
-
-/*
- * In one terraforming command all four corners of a initial tile can be raised/lowered (though this is not available to the player).
- * The maximal amount of height modifications is archieved when raising a complete flat land from sea level to MAX_TILE_HEIGHT or vice versa.
- * This affects all corners with a manhatten distance smaller than MAX_TILE_HEIGHT to one of the initial 4 corners.
- * Their maximal amount is computed to 4 * \sum_{i=1}^{h_max} i  =  2 * h_max * (h_max + 1).
- */
-static const int TERRAFORMER_MODHEIGHT_SIZE = 2 * MAX_TILE_HEIGHT * (MAX_TILE_HEIGHT + 1);
-
-/*
- * The maximal amount of affected tiles (i.e. the tiles that incident with one of the corners above, is computed similiar to
- * 1 + 4 * \sum_{i=1}^{h_max} (i+1)  =  1 + 2 * h_max + (h_max + 3).
- */
-static const int TERRAFORMER_TILE_TABLE_SIZE = 1 + 2 * MAX_TILE_HEIGHT * (MAX_TILE_HEIGHT + 3);
-
-struct TerraformerHeightMod {
-	TileIndex tile;   ///< Referenced tile.
-	byte height;      ///< New TileHeight (height of north corner) of the tile.
-};
-
-struct TerraformerState {
-	int modheight_count;                                         ///< amount of entries in "modheight".
-	int tile_table_count;                                        ///< amount of entries in "tile_table".
-
-	/**
-	 * Dirty tiles, i.e.\ at least one corner changed.
-	 *
-	 * This array contains the tiles which are or will be marked as dirty.
-	 *
-	 * @ingroup dirty
-	 */
-	TileIndex tile_table[TERRAFORMER_TILE_TABLE_SIZE];
-	TerraformerHeightMod modheight[TERRAFORMER_MODHEIGHT_SIZE];  ///< Height modifications.
-};
-
-/**
- * Gets the TileHeight (height of north corner) of a tile as of current terraforming progress.
- *
- * @param ts TerraformerState.
- * @param tile Tile.
- * @return TileHeight.
- */
-static int TerraformGetHeightOfTile(TerraformerState *ts, TileIndex tile)
-{
-	TerraformerHeightMod *mod = ts->modheight;
-	int count;
-
-	for (count = ts->modheight_count; count != 0; count--, mod++) {
-		if (mod->tile == tile) return mod->height;
-	}
-
-	/* TileHeight unchanged so far, read value from map. */
-	return TileHeight(tile);
-}
-
-/**
- * Stores the TileHeight (height of north corner) of a tile in a TerraformerState.
- *
- * @param ts TerraformerState.
- * @param tile Tile.
- * @param height New TileHeight.
- */
-static void TerraformSetHeightOfTile(TerraformerState *ts, TileIndex tile, int height)
-{
-	/* Find tile in the "modheight" table.
-	 * Note: In a normal user-terraform command the tile will not be found in the "modheight" table.
-	 *       But during house- or industry-construction multiple corners can be terraformed at once. */
-	TerraformerHeightMod *mod = ts->modheight;
-	int count = ts->modheight_count;
-	while ((count > 0) && (mod->tile != tile)) {
-		mod++;
-		count--;
-	}
-
-	/* New entry? */
-	if (count == 0) {
-		assert(ts->modheight_count < TERRAFORMER_MODHEIGHT_SIZE);
-		ts->modheight_count++;
-	}
-
-	/* Finally store the new value */
-	mod->tile = tile;
-	mod->height = (byte)height;
-}
-
-/**
- * Adds a tile to the "tile_table" in a TerraformerState.
- *
- * @param ts TerraformerState.
- * @param tile Tile.
- * @ingroup dirty
- */
-static void TerraformAddDirtyTile(TerraformerState *ts, TileIndex tile)
-{
-	int count;
-	TileIndex *t;
-
-	count = ts->tile_table_count;
-
-	for (t = ts->tile_table; count != 0; count--, t++) {
-		if (*t == tile) return;
-	}
-
-	assert(ts->tile_table_count < TERRAFORMER_TILE_TABLE_SIZE);
-
-	ts->tile_table[ts->tile_table_count++] = tile;
-}
-
-/**
- * Adds all tiles that incident with the north corner of a specific tile to the "tile_table" in a TerraformerState.
- *
- * @param ts TerraformerState.
- * @param tile Tile.
- * @ingroup dirty
- */
-static void TerraformAddDirtyTileAround(TerraformerState *ts, TileIndex tile)
-{
-	TerraformAddDirtyTile(ts, tile + TileDiffXY( 0, -1));
-	TerraformAddDirtyTile(ts, tile + TileDiffXY(-1, -1));
-	TerraformAddDirtyTile(ts, tile + TileDiffXY(-1,  0));
-	TerraformAddDirtyTile(ts, tile);
-}
-
-/**
- * Terraform the north corner of a tile to a specific height.
- *
- * @param ts TerraformerState.
- * @param tile Tile.
- * @param height Aimed height.
- * @param return Error code or cost.
- */
-static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int height)
-{
-	CommandCost total_cost = CommandCost();
-
-	assert(tile < MapSize());
-
-	/* Check range of destination height */
-	if (height < 0) return_cmd_error(STR_1003_ALREADY_AT_SEA_LEVEL);
-	if (height > MAX_TILE_HEIGHT) return_cmd_error(STR_1004_TOO_HIGH);
-
-	/*
-	 * Check if the terraforming has any effect.
-	 * This can only be true, if multiple corners of the start-tile are terraformed (i.e. the terraforming is done by towns/industries etc.).
-	 * In this case the terraforming should fail. (Don't know why.)
-	 */
-	if (height == TerraformGetHeightOfTile(ts, tile)) return CMD_ERROR;
-
-	/* Check "too close to edge of map" */
-	uint x = TileX(tile);
-	uint y = TileY(tile);
-	if ((x <= 1) || (y <= 1) || (x >= MapMaxX() - 1) || (y >= MapMaxY() - 1)) {
-		/*
-		 * Determine a sensible error tile
-		 * Note: If x and y are both zero this will disable the error tile. (Tile 0 cannot be highlighted :( )
-		 */
-		if ((x == 1) && (y != 0)) x = 0;
-		if ((y == 1) && (x != 0)) y = 0;
-		_terraform_err_tile = TileXY(x, y);
-		return_cmd_error(STR_0002_TOO_CLOSE_TO_EDGE_OF_MAP);
-	}
-
-	/* Mark incident tiles, that are involved in the terraforming */
-	TerraformAddDirtyTileAround(ts, tile);
-
-	/* Store the height modification */
-	TerraformSetHeightOfTile(ts, tile, height);
-
-	/* Increment cost */
-	total_cost.AddCost(_price.terraform);
-
-	/* Recurse to neighboured corners if height difference is larger than 1 */
-	{
-		const TileIndexDiffC *ttm;
-
-		static const TileIndexDiffC _terraform_tilepos[] = {
-			{ 1,  0}, // move to tile in SE
-			{-2,  0}, // undo last move, and move to tile in NW
-			{ 1,  1}, // undo last move, and move to tile in SW
-			{ 0, -2}  // undo last move, and move to tile in NE
-		};
-
-		for (ttm = _terraform_tilepos; ttm != endof(_terraform_tilepos); ttm++) {
-			tile += ToTileIndexDiff(*ttm);
-
-			/* Get TileHeight of neighboured tile as of current terraform progress */
-			int r = TerraformGetHeightOfTile(ts, tile);
-			int height_diff = height - r;
-
-			/* Is the height difference to the neighboured corner greater than 1? */
-			if (abs(height_diff) > 1) {
-				/* Terraform the neighboured corner. The resulting height difference should be 1. */
-				height_diff += (height_diff < 0 ? 1 : -1);
-				CommandCost cost = TerraformTileHeight(ts, tile, r + height_diff);
-				if (CmdFailed(cost)) return cost;
-				total_cost.AddCost(cost);
-			}
-		}
-	}
-
-	return total_cost;
-}
-
-/** Terraform land
- * @param tile tile to terraform
- * @param flags for this command type
- * @param p1 corners to terraform (SLOPE_xxx)
- * @param p2 direction; eg up (non-zero) or down (zero)
- * @return error or cost of terraforming
- */
-CommandCost CmdTerraformLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
-{
-	TerraformerState ts;
-	CommandCost total_cost = CommandCost();
-	int direction = (p2 != 0 ? 1 : -1);
-
-	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
-
-	_terraform_err_tile = 0;
-
-	ts.modheight_count = ts.tile_table_count = 0;
-
-	/* Make an extra check for map-bounds cause we add tiles to the originating tile */
-	if (tile + TileDiffXY(1, 1) >= MapSize()) return CMD_ERROR;
-
-	/* Compute the costs and the terraforming result in a model of the landscape */
-	if ((p1 & SLOPE_W) != 0) {
-		TileIndex t = tile + TileDiffXY(1, 0);
-		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
-		if (CmdFailed(cost)) return cost;
-		total_cost.AddCost(cost);
-	}
-
-	if ((p1 & SLOPE_S) != 0) {
-		TileIndex t = tile + TileDiffXY(1, 1);
-		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
-		if (CmdFailed(cost)) return cost;
-		total_cost.AddCost(cost);
-	}
-
-	if ((p1 & SLOPE_E) != 0) {
-		TileIndex t = tile + TileDiffXY(0, 1);
-		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
-		if (CmdFailed(cost)) return cost;
-		total_cost.AddCost(cost);
-	}
-
-	if ((p1 & SLOPE_N) != 0) {
-		TileIndex t = tile + TileDiffXY(0, 0);
-		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
-		if (CmdFailed(cost)) return cost;
-		total_cost.AddCost(cost);
-	}
-
-	/* Check if the terraforming is valid wrt. tunnels, bridges and objects on the surface */
-	{
-		int count;
-		TileIndex *ti = ts.tile_table;
-
-		for (count = ts.tile_table_count; count != 0; count--, ti++) {
-			TileIndex tile = *ti;
-
-			/* Find new heights of tile corners */
-			uint z_N = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(0, 0));
-			uint z_W = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(1, 0));
-			uint z_S = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(1, 1));
-			uint z_E = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(0, 1));
-
-			/* Find min and max height of tile */
-			uint z_min = min(min(z_N, z_W), min(z_S, z_E));
-			uint z_max = max(max(z_N, z_W), max(z_S, z_E));
-
-			/* Compute tile slope */
-			uint tileh = (z_max > z_min + 1 ? SLOPE_STEEP : SLOPE_FLAT);
-			if (z_W > z_min) tileh += SLOPE_W;
-			if (z_S > z_min) tileh += SLOPE_S;
-			if (z_E > z_min) tileh += SLOPE_E;
-			if (z_N > z_min) tileh += SLOPE_N;
-
-			/* Check if bridge would take damage */
-			if (direction == 1 && MayHaveBridgeAbove(tile) && IsBridgeAbove(tile) &&
-					GetBridgeHeight(GetSouthernBridgeEnd(tile)) <= z_max * TILE_HEIGHT) {
-				_terraform_err_tile = tile; // highlight the tile under the bridge
-				return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
-			}
-			/* Check if tunnel would take damage */
-			if (direction == -1 && IsTunnelInWay(tile, z_min * TILE_HEIGHT)) {
-				_terraform_err_tile = tile; // highlight the tile above the tunnel
-				return_cmd_error(STR_1002_EXCAVATION_WOULD_DAMAGE);
-			}
-			/* Check tiletype-specific things, and add extra-cost */
-			CommandCost cost = _tile_type_procs[GetTileType(tile)]->terraform_tile_proc(tile, flags | DC_AUTO, z_min * TILE_HEIGHT, (Slope) tileh);
-			if (CmdFailed(cost)) {
-				_terraform_err_tile = tile;
-				return cost;
-			}
-			total_cost.AddCost(cost);
-		}
-	}
-
-	if (flags & DC_EXEC) {
-		/* change the height */
-		{
-			int count;
-			TerraformerHeightMod *mod;
-
-			mod = ts.modheight;
-			for (count = ts.modheight_count; count != 0; count--, mod++) {
-				TileIndex til = mod->tile;
-
-				SetTileHeight(til, mod->height);
-			}
-		}
-
-		/* finally mark the dirty tiles dirty */
-		{
-			int count;
-			TileIndex *ti = ts.tile_table;
-			for (count = ts.tile_table_count; count != 0; count--, ti++) {
-				MarkTileDirtyByTile(*ti);
-			}
-		}
-	}
-	return total_cost;
-}
-
-
-/** Levels a selected (rectangle) area of land
- * @param tile end tile of area-drag
- * @param flags for this command type
- * @param p1 start tile of area drag
- * @param p2 height difference; eg raise (+1), lower (-1) or level (0)
- * @return  error or cost of terraforming
- */
-CommandCost CmdLevelLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
-{
-	int size_x, size_y;
-	int ex;
-	int ey;
-	int sx, sy;
-	uint h, oldh, curh;
-	CommandCost money;
-	CommandCost ret;
-	CommandCost cost;
-
-	if (p1 >= MapSize()) return CMD_ERROR;
-
-	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
-
-	/* remember level height */
-	oldh = TileHeight(p1);
-
-	/* compute new height */
-	h = oldh + p2;
-
-	/* Check range of destination height */
-	if (h > MAX_TILE_HEIGHT) return_cmd_error((oldh == 0) ? STR_1003_ALREADY_AT_SEA_LEVEL : STR_1004_TOO_HIGH);
-
-	/* make sure sx,sy are smaller than ex,ey */
-	ex = TileX(tile);
-	ey = TileY(tile);
-	sx = TileX(p1);
-	sy = TileY(p1);
-	if (ex < sx) Swap(ex, sx);
-	if (ey < sy) Swap(ey, sy);
-	tile = TileXY(sx, sy);
-
-	size_x = ex - sx + 1;
-	size_y = ey - sy + 1;
-
-	money.AddCost(GetAvailableMoneyForCommand());
-
-	BEGIN_TILE_LOOP(tile2, size_x, size_y, tile) {
-		curh = TileHeight(tile2);
-		while (curh != h) {
-			ret = DoCommand(tile2, SLOPE_N, (curh > h) ? 0 : 1, flags & ~DC_EXEC, CMD_TERRAFORM_LAND);
-			if (CmdFailed(ret)) break;
-
-			if (flags & DC_EXEC) {
-				money.AddCost(-ret.GetCost());
-				if (money.GetCost() < 0) {
-					_additional_cash_required = ret.GetCost();
-					return cost;
-				}
-				DoCommand(tile2, SLOPE_N, (curh > h) ? 0 : 1, flags, CMD_TERRAFORM_LAND);
-			}
-
-			cost.AddCost(ret);
-			curh += (curh > h) ? -1 : 1;
-		}
-	} END_TILE_LOOP(tile2, size_x, size_y, tile)
-
-	return (cost.GetCost() == 0) ? CMD_ERROR : cost;
-}
-
-/** Purchase a land area. Actually you only purchase one tile, so
- * the name is a bit confusing ;p
- * @param tile the tile the player is purchasing
- * @param flags for this command type
- * @param p1 unused
- * @param p2 unused
- * @return error of cost of operation
- */
-CommandCost CmdPurchaseLandArea(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
-{
-	CommandCost cost;
-
-	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
-
-	if (IsOwnedLandTile(tile) && IsTileOwner(tile, _current_player)) {
-		return_cmd_error(STR_5807_YOU_ALREADY_OWN_IT);
-	}
-
-	cost = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
-	if (CmdFailed(cost)) return CMD_ERROR;
-
-	if (flags & DC_EXEC) {
-		MakeOwnedLand(tile, _current_player);
-		MarkTileDirtyByTile(tile);
-	}
-
-	return cost.AddCost(_price.clear_roughland * 10);
-}
-
+#include "table/clear_land.h"
 
 static CommandCost ClearTile_Clear(TileIndex tile, byte flags)
 {
@@ -470,33 +43,6 @@ static CommandCost ClearTile_Clear(TileIndex tile, byte flags)
 	return price;
 }
 
-/** Sell a land area. Actually you only sell one tile, so
- * the name is a bit confusing ;p
- * @param tile the tile the player is selling
- * @param flags for this command type
- * @param p1 unused
- * @param p2 unused
- * @return error or cost of operation
- */
-CommandCost CmdSellLandArea(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
-{
-	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
-
-	if (!IsOwnedLandTile(tile)) return CMD_ERROR;
-	if (!CheckTileOwnership(tile) && _current_player != OWNER_WATER) return CMD_ERROR;
-
-
-	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
-
-	if (flags & DC_EXEC) DoClearSquare(tile);
-
-	return CommandCost(- _price.clear_roughland * 2);
-}
-
-
-#include "table/clear_land.h"
-
-
 void DrawClearLandTile(const TileInfo *ti, byte set)
 {
 	DrawGroundSprite(SPR_FLAT_BARE_LAND + _tileh_to_sprite[ti->tileh] + set * 19, PAL_NONE);
diff --git a/src/terraform_cmd.cpp b/src/terraform_cmd.cpp
new file mode 100644
index 000000000..138506231
--- /dev/null
+++ b/src/terraform_cmd.cpp
@@ -0,0 +1,411 @@
+/* $Id$ */
+
+/** @file terraform_cmd.cpp Commands related to terraforming. */
+
+#include "stdafx.h"
+#include "openttd.h"
+#include "strings_type.h"
+#include "table/strings.h"
+#include "command_func.h"
+#include "tile_map.h"
+#include "tunnel_map.h"
+#include "bridge_map.h"
+#include "variables.h"
+#include "functions.h"
+#include "economy_func.h"
+
+/*
+ * In one terraforming command all four corners of a initial tile can be raised/lowered (though this is not available to the player).
+ * The maximal amount of height modifications is archieved when raising a complete flat land from sea level to MAX_TILE_HEIGHT or vice versa.
+ * This affects all corners with a manhatten distance smaller than MAX_TILE_HEIGHT to one of the initial 4 corners.
+ * Their maximal amount is computed to 4 * \sum_{i=1}^{h_max} i  =  2 * h_max * (h_max + 1).
+ */
+static const int TERRAFORMER_MODHEIGHT_SIZE = 2 * MAX_TILE_HEIGHT * (MAX_TILE_HEIGHT + 1);
+
+/*
+ * The maximal amount of affected tiles (i.e. the tiles that incident with one of the corners above, is computed similiar to
+ * 1 + 4 * \sum_{i=1}^{h_max} (i+1)  =  1 + 2 * h_max + (h_max + 3).
+ */
+static const int TERRAFORMER_TILE_TABLE_SIZE = 1 + 2 * MAX_TILE_HEIGHT * (MAX_TILE_HEIGHT + 3);
+
+struct TerraformerHeightMod {
+	TileIndex tile;   ///< Referenced tile.
+	byte height;      ///< New TileHeight (height of north corner) of the tile.
+};
+
+struct TerraformerState {
+	int modheight_count;                                         ///< amount of entries in "modheight".
+	int tile_table_count;                                        ///< amount of entries in "tile_table".
+
+	/**
+	 * Dirty tiles, i.e.\ at least one corner changed.
+	 *
+	 * This array contains the tiles which are or will be marked as dirty.
+	 *
+	 * @ingroup dirty
+	 */
+	TileIndex tile_table[TERRAFORMER_TILE_TABLE_SIZE];
+	TerraformerHeightMod modheight[TERRAFORMER_MODHEIGHT_SIZE];  ///< Height modifications.
+};
+
+TileIndex _terraform_err_tile;
+
+/**
+ * Gets the TileHeight (height of north corner) of a tile as of current terraforming progress.
+ *
+ * @param ts TerraformerState.
+ * @param tile Tile.
+ * @return TileHeight.
+ */
+static int TerraformGetHeightOfTile(TerraformerState *ts, TileIndex tile)
+{
+	TerraformerHeightMod *mod = ts->modheight;
+	int count;
+
+	for (count = ts->modheight_count; count != 0; count--, mod++) {
+		if (mod->tile == tile) return mod->height;
+	}
+
+	/* TileHeight unchanged so far, read value from map. */
+	return TileHeight(tile);
+}
+
+/**
+ * Stores the TileHeight (height of north corner) of a tile in a TerraformerState.
+ *
+ * @param ts TerraformerState.
+ * @param tile Tile.
+ * @param height New TileHeight.
+ */
+static void TerraformSetHeightOfTile(TerraformerState *ts, TileIndex tile, int height)
+{
+	/* Find tile in the "modheight" table.
+	 * Note: In a normal user-terraform command the tile will not be found in the "modheight" table.
+	 *       But during house- or industry-construction multiple corners can be terraformed at once. */
+	TerraformerHeightMod *mod = ts->modheight;
+	int count = ts->modheight_count;
+	while ((count > 0) && (mod->tile != tile)) {
+		mod++;
+		count--;
+	}
+
+	/* New entry? */
+	if (count == 0) {
+		assert(ts->modheight_count < TERRAFORMER_MODHEIGHT_SIZE);
+		ts->modheight_count++;
+	}
+
+	/* Finally store the new value */
+	mod->tile = tile;
+	mod->height = (byte)height;
+}
+
+/**
+ * Adds a tile to the "tile_table" in a TerraformerState.
+ *
+ * @param ts TerraformerState.
+ * @param tile Tile.
+ * @ingroup dirty
+ */
+static void TerraformAddDirtyTile(TerraformerState *ts, TileIndex tile)
+{
+	int count;
+	TileIndex *t;
+
+	count = ts->tile_table_count;
+
+	for (t = ts->tile_table; count != 0; count--, t++) {
+		if (*t == tile) return;
+	}
+
+	assert(ts->tile_table_count < TERRAFORMER_TILE_TABLE_SIZE);
+
+	ts->tile_table[ts->tile_table_count++] = tile;
+}
+
+/**
+ * Adds all tiles that incident with the north corner of a specific tile to the "tile_table" in a TerraformerState.
+ *
+ * @param ts TerraformerState.
+ * @param tile Tile.
+ * @ingroup dirty
+ */
+static void TerraformAddDirtyTileAround(TerraformerState *ts, TileIndex tile)
+{
+	TerraformAddDirtyTile(ts, tile + TileDiffXY( 0, -1));
+	TerraformAddDirtyTile(ts, tile + TileDiffXY(-1, -1));
+	TerraformAddDirtyTile(ts, tile + TileDiffXY(-1,  0));
+	TerraformAddDirtyTile(ts, tile);
+}
+
+/**
+ * Terraform the north corner of a tile to a specific height.
+ *
+ * @param ts TerraformerState.
+ * @param tile Tile.
+ * @param height Aimed height.
+ * @param return Error code or cost.
+ */
+static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int height)
+{
+	CommandCost total_cost = CommandCost();
+
+	assert(tile < MapSize());
+
+	/* Check range of destination height */
+	if (height < 0) return_cmd_error(STR_1003_ALREADY_AT_SEA_LEVEL);
+	if (height > MAX_TILE_HEIGHT) return_cmd_error(STR_1004_TOO_HIGH);
+
+	/*
+	 * Check if the terraforming has any effect.
+	 * This can only be true, if multiple corners of the start-tile are terraformed (i.e. the terraforming is done by towns/industries etc.).
+	 * In this case the terraforming should fail. (Don't know why.)
+	 */
+	if (height == TerraformGetHeightOfTile(ts, tile)) return CMD_ERROR;
+
+	/* Check "too close to edge of map" */
+	uint x = TileX(tile);
+	uint y = TileY(tile);
+	if ((x <= 1) || (y <= 1) || (x >= MapMaxX() - 1) || (y >= MapMaxY() - 1)) {
+		/*
+		 * Determine a sensible error tile
+		 * Note: If x and y are both zero this will disable the error tile. (Tile 0 cannot be highlighted :( )
+		 */
+		if ((x == 1) && (y != 0)) x = 0;
+		if ((y == 1) && (x != 0)) y = 0;
+		_terraform_err_tile = TileXY(x, y);
+		return_cmd_error(STR_0002_TOO_CLOSE_TO_EDGE_OF_MAP);
+	}
+
+	/* Mark incident tiles, that are involved in the terraforming */
+	TerraformAddDirtyTileAround(ts, tile);
+
+	/* Store the height modification */
+	TerraformSetHeightOfTile(ts, tile, height);
+
+	/* Increment cost */
+	total_cost.AddCost(_price.terraform);
+
+	/* Recurse to neighboured corners if height difference is larger than 1 */
+	{
+		const TileIndexDiffC *ttm;
+
+		static const TileIndexDiffC _terraform_tilepos[] = {
+			{ 1,  0}, // move to tile in SE
+			{-2,  0}, // undo last move, and move to tile in NW
+			{ 1,  1}, // undo last move, and move to tile in SW
+			{ 0, -2}  // undo last move, and move to tile in NE
+		};
+
+		for (ttm = _terraform_tilepos; ttm != endof(_terraform_tilepos); ttm++) {
+			tile += ToTileIndexDiff(*ttm);
+
+			/* Get TileHeight of neighboured tile as of current terraform progress */
+			int r = TerraformGetHeightOfTile(ts, tile);
+			int height_diff = height - r;
+
+			/* Is the height difference to the neighboured corner greater than 1? */
+			if (abs(height_diff) > 1) {
+				/* Terraform the neighboured corner. The resulting height difference should be 1. */
+				height_diff += (height_diff < 0 ? 1 : -1);
+				CommandCost cost = TerraformTileHeight(ts, tile, r + height_diff);
+				if (CmdFailed(cost)) return cost;
+				total_cost.AddCost(cost);
+			}
+		}
+	}
+
+	return total_cost;
+}
+
+/** Terraform land
+ * @param tile tile to terraform
+ * @param flags for this command type
+ * @param p1 corners to terraform (SLOPE_xxx)
+ * @param p2 direction; eg up (non-zero) or down (zero)
+ * @return error or cost of terraforming
+ */
+CommandCost CmdTerraformLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
+{
+	TerraformerState ts;
+	CommandCost total_cost = CommandCost();
+	int direction = (p2 != 0 ? 1 : -1);
+
+	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
+
+	_terraform_err_tile = 0;
+
+	ts.modheight_count = ts.tile_table_count = 0;
+
+	/* Make an extra check for map-bounds cause we add tiles to the originating tile */
+	if (tile + TileDiffXY(1, 1) >= MapSize()) return CMD_ERROR;
+
+	/* Compute the costs and the terraforming result in a model of the landscape */
+	if ((p1 & SLOPE_W) != 0) {
+		TileIndex t = tile + TileDiffXY(1, 0);
+		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
+		if (CmdFailed(cost)) return cost;
+		total_cost.AddCost(cost);
+	}
+
+	if ((p1 & SLOPE_S) != 0) {
+		TileIndex t = tile + TileDiffXY(1, 1);
+		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
+		if (CmdFailed(cost)) return cost;
+		total_cost.AddCost(cost);
+	}
+
+	if ((p1 & SLOPE_E) != 0) {
+		TileIndex t = tile + TileDiffXY(0, 1);
+		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
+		if (CmdFailed(cost)) return cost;
+		total_cost.AddCost(cost);
+	}
+
+	if ((p1 & SLOPE_N) != 0) {
+		TileIndex t = tile + TileDiffXY(0, 0);
+		CommandCost cost = TerraformTileHeight(&ts, t, TileHeight(t) + direction);
+		if (CmdFailed(cost)) return cost;
+		total_cost.AddCost(cost);
+	}
+
+	/* Check if the terraforming is valid wrt. tunnels, bridges and objects on the surface */
+	{
+		int count;
+		TileIndex *ti = ts.tile_table;
+
+		for (count = ts.tile_table_count; count != 0; count--, ti++) {
+			TileIndex tile = *ti;
+
+			/* Find new heights of tile corners */
+			uint z_N = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(0, 0));
+			uint z_W = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(1, 0));
+			uint z_S = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(1, 1));
+			uint z_E = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(0, 1));
+
+			/* Find min and max height of tile */
+			uint z_min = min(min(z_N, z_W), min(z_S, z_E));
+			uint z_max = max(max(z_N, z_W), max(z_S, z_E));
+
+			/* Compute tile slope */
+			uint tileh = (z_max > z_min + 1 ? SLOPE_STEEP : SLOPE_FLAT);
+			if (z_W > z_min) tileh += SLOPE_W;
+			if (z_S > z_min) tileh += SLOPE_S;
+			if (z_E > z_min) tileh += SLOPE_E;
+			if (z_N > z_min) tileh += SLOPE_N;
+
+			/* Check if bridge would take damage */
+			if (direction == 1 && MayHaveBridgeAbove(tile) && IsBridgeAbove(tile) &&
+					GetBridgeHeight(GetSouthernBridgeEnd(tile)) <= z_max * TILE_HEIGHT) {
+				_terraform_err_tile = tile; // highlight the tile under the bridge
+				return_cmd_error(STR_5007_MUST_DEMOLISH_BRIDGE_FIRST);
+			}
+			/* Check if tunnel would take damage */
+			if (direction == -1 && IsTunnelInWay(tile, z_min * TILE_HEIGHT)) {
+				_terraform_err_tile = tile; // highlight the tile above the tunnel
+				return_cmd_error(STR_1002_EXCAVATION_WOULD_DAMAGE);
+			}
+			/* Check tiletype-specific things, and add extra-cost */
+			CommandCost cost = _tile_type_procs[GetTileType(tile)]->terraform_tile_proc(tile, flags | DC_AUTO, z_min * TILE_HEIGHT, (Slope) tileh);
+			if (CmdFailed(cost)) {
+				_terraform_err_tile = tile;
+				return cost;
+			}
+			total_cost.AddCost(cost);
+		}
+	}
+
+	if (flags & DC_EXEC) {
+		/* change the height */
+		{
+			int count;
+			TerraformerHeightMod *mod;
+
+			mod = ts.modheight;
+			for (count = ts.modheight_count; count != 0; count--, mod++) {
+				TileIndex til = mod->tile;
+
+				SetTileHeight(til, mod->height);
+			}
+		}
+
+		/* finally mark the dirty tiles dirty */
+		{
+			int count;
+			TileIndex *ti = ts.tile_table;
+			for (count = ts.tile_table_count; count != 0; count--, ti++) {
+				MarkTileDirtyByTile(*ti);
+			}
+		}
+	}
+	return total_cost;
+}
+
+
+/** Levels a selected (rectangle) area of land
+ * @param tile end tile of area-drag
+ * @param flags for this command type
+ * @param p1 start tile of area drag
+ * @param p2 height difference; eg raise (+1), lower (-1) or level (0)
+ * @return  error or cost of terraforming
+ */
+CommandCost CmdLevelLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
+{
+	int size_x, size_y;
+	int ex;
+	int ey;
+	int sx, sy;
+	uint h, oldh, curh;
+	CommandCost money;
+	CommandCost ret;
+	CommandCost cost;
+
+	if (p1 >= MapSize()) return CMD_ERROR;
+
+	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
+
+	/* remember level height */
+	oldh = TileHeight(p1);
+
+	/* compute new height */
+	h = oldh + p2;
+
+	/* Check range of destination height */
+	if (h > MAX_TILE_HEIGHT) return_cmd_error((oldh == 0) ? STR_1003_ALREADY_AT_SEA_LEVEL : STR_1004_TOO_HIGH);
+
+	/* make sure sx,sy are smaller than ex,ey */
+	ex = TileX(tile);
+	ey = TileY(tile);
+	sx = TileX(p1);
+	sy = TileY(p1);
+	if (ex < sx) Swap(ex, sx);
+	if (ey < sy) Swap(ey, sy);
+	tile = TileXY(sx, sy);
+
+	size_x = ex - sx + 1;
+	size_y = ey - sy + 1;
+
+	money.AddCost(GetAvailableMoneyForCommand());
+
+	BEGIN_TILE_LOOP(tile2, size_x, size_y, tile) {
+		curh = TileHeight(tile2);
+		while (curh != h) {
+			ret = DoCommand(tile2, SLOPE_N, (curh > h) ? 0 : 1, flags & ~DC_EXEC, CMD_TERRAFORM_LAND);
+			if (CmdFailed(ret)) break;
+
+			if (flags & DC_EXEC) {
+				money.AddCost(-ret.GetCost());
+				if (money.GetCost() < 0) {
+					_additional_cash_required = ret.GetCost();
+					return cost;
+				}
+				DoCommand(tile2, SLOPE_N, (curh > h) ? 0 : 1, flags, CMD_TERRAFORM_LAND);
+			}
+
+			cost.AddCost(ret);
+			curh += (curh > h) ? -1 : 1;
+		}
+	} END_TILE_LOOP(tile2, size_x, size_y, tile)
+
+	return (cost.GetCost() == 0) ? CMD_ERROR : cost;
+}
diff --git a/src/terraform_gui.cpp b/src/terraform_gui.cpp
index f33db131a..f074d64eb 100644
--- a/src/terraform_gui.cpp
+++ b/src/terraform_gui.cpp
@@ -26,6 +26,7 @@ void CcTerraform(bool success, TileIndex tile, uint32 p1, uint32 p2)
 	if (success) {
 		SndPlayTileFx(SND_1F_SPLAT, tile);
 	} else {
+		extern TileIndex _terraform_err_tile;
 		SetRedErrorSquare(_terraform_err_tile);
 	}
 }
diff --git a/src/unmovable_cmd.cpp b/src/unmovable_cmd.cpp
index ef4638d23..d11020421 100644
--- a/src/unmovable_cmd.cpp
+++ b/src/unmovable_cmd.cpp
@@ -25,6 +25,7 @@
 #include "transparency.h"
 #include "functions.h"
 #include "window_func.h"
+#include "vehicle_func.h"
 
 /** Destroy a HQ.
  * During normal gameplay you can only implicitely destroy a HQ when you are
@@ -111,6 +112,58 @@ CommandCost CmdBuildCompanyHQ(TileIndex tile, uint32 flags, uint32 p1, uint32 p2
 	return cost;
 }
 
+/** Purchase a land area. Actually you only purchase one tile, so
+ * the name is a bit confusing ;p
+ * @param tile the tile the player is purchasing
+ * @param flags for this command type
+ * @param p1 unused
+ * @param p2 unused
+ * @return error of cost of operation
+ */
+CommandCost CmdPurchaseLandArea(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
+{
+	CommandCost cost;
+
+	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
+
+	if (IsOwnedLandTile(tile) && IsTileOwner(tile, _current_player)) {
+		return_cmd_error(STR_5807_YOU_ALREADY_OWN_IT);
+	}
+
+	cost = DoCommand(tile, 0, 0, flags, CMD_LANDSCAPE_CLEAR);
+	if (CmdFailed(cost)) return CMD_ERROR;
+
+	if (flags & DC_EXEC) {
+		MakeOwnedLand(tile, _current_player);
+		MarkTileDirtyByTile(tile);
+	}
+
+	return cost.AddCost(_price.clear_roughland * 10);
+}
+
+/** Sell a land area. Actually you only sell one tile, so
+ * the name is a bit confusing ;p
+ * @param tile the tile the player is selling
+ * @param flags for this command type
+ * @param p1 unused
+ * @param p2 unused
+ * @return error or cost of operation
+ */
+CommandCost CmdSellLandArea(TileIndex tile, uint32 flags, uint32 p1, uint32 p2)
+{
+	SET_EXPENSES_TYPE(EXPENSES_CONSTRUCTION);
+
+	if (!IsOwnedLandTile(tile)) return CMD_ERROR;
+	if (!CheckTileOwnership(tile) && _current_player != OWNER_WATER) return CMD_ERROR;
+
+
+	if (!EnsureNoVehicleOnGround(tile)) return CMD_ERROR;
+
+	if (flags & DC_EXEC) DoClearSquare(tile);
+
+	return CommandCost(- _price.clear_roughland * 2);
+}
+
 static Foundation GetFoundation_Unmovable(TileIndex tile, Slope tileh);
 
 static void DrawTile_Unmovable(TileInfo *ti)
diff --git a/src/unmovable_map.h b/src/unmovable_map.h
index 0b3132ce0..0f6283cb7 100644
--- a/src/unmovable_map.h
+++ b/src/unmovable_map.h
@@ -5,6 +5,9 @@
 #ifndef UNMOVABLE_MAP_H
 #define UNMOVABLE_MAP_H
 
+#include "core/bitmath_func.hpp"
+#include "tile_map.h"
+
 enum {
 	HQ_NUM_TILE = 4, ///< Number of HQ tiles
 	HQ_NUM_SIZE = 5  ///< Number of stages of an HQ
diff --git a/src/variables.h b/src/variables.h
index 6532ad453..aaf62c9a8 100644
--- a/src/variables.h
+++ b/src/variables.h
@@ -90,7 +90,6 @@ VARDEF PlayerFace _player_face; ///< for player face storage in openttd.cfg
 
 /* IN/OUT parameters to commands */
 VARDEF byte _yearly_expenses_type;
-VARDEF TileIndex _terraform_err_tile;
 VARDEF TileIndex _build_tunnel_endtile;
 VARDEF bool _generating_world;