(svn r15190) -Feature: Allow terraforming of the tiles at the edges of the map.

31 files changed, 417 insertions, 171 deletions

diff --git a/src/ai/api/ai_tile.cpp b/src/ai/api/ai_tile.cpp
index a1f16b9bd..6426c9374 100644
--- a/src/ai/api/ai_tile.cpp
+++ b/src/ai/api/ai_tile.cpp
@@ -190,22 +190,22 @@
 
 /* static */ bool AITile::RaiseTile(TileIndex tile, int32 slope)
 {
-	EnforcePrecondition(false, ::IsValidTile(tile));
+	EnforcePrecondition(false, tile < ::MapSize());
 
 	return AIObject::DoCommand(tile, slope, 1, CMD_TERRAFORM_LAND);
 }
 
 /* static */ bool AITile::LowerTile(TileIndex tile, int32 slope)
 {
-	EnforcePrecondition(false, ::IsValidTile(tile));
+	EnforcePrecondition(false, tile < ::MapSize());
 
 	return AIObject::DoCommand(tile, slope, 0, CMD_TERRAFORM_LAND);
 }
 
 /* static */ bool AITile::LevelTiles(TileIndex start_tile, TileIndex end_tile)
 {
-	EnforcePrecondition(false, ::IsValidTile(start_tile));
-	EnforcePrecondition(false, ::IsValidTile(end_tile));
+	EnforcePrecondition(false, start_tile < ::MapSize());
+	EnforcePrecondition(false, end_tile < ::MapSize());
 
 	return AIObject::DoCommand(end_tile, start_tile, 0, CMD_LEVEL_LAND);
 }
diff --git a/src/ai/api/ai_tile.hpp b/src/ai/api/ai_tile.hpp
index 9a4df1677..576bacf07 100644
--- a/src/ai/api/ai_tile.hpp
+++ b/src/ai/api/ai_tile.hpp
@@ -291,7 +291,7 @@ public:
 	 *  for example: SLOPE_N | SLOPE_W (= SLOPE_NW)
 	 * @param tile The tile to raise.
 	 * @param slope Corners to raise (SLOPE_xxx).
-	 * @pre AIMap::IsValidTile(tile).
+	 * @pre tile < AIMap::GetMapSize().
 	 * @exception AIError::ERR_AREA_NOT_CLEAR
 	 * @exception AIError::ERR_TOO_CLOSE_TO_EDGE
 	 * @exception AITile::ERR_TILE_TOO_HIGH
@@ -304,7 +304,7 @@ public:
 	 *  for example: SLOPE_N | SLOPE_W (= SLOPE_NW)
 	 * @param tile The tile to lower.
 	 * @param slope Corners to lower (SLOPE_xxx).
-	 * @pre AIMap::IsValidTile(tile).
+	 * @pre tile < AIMap::GetMapSize().
 	 * @exception AIError::ERR_AREA_NOT_CLEAR
 	 * @exception AIError::ERR_TOO_CLOSE_TO_EDGE
 	 * @exception AITile::ERR_TILE_TOO_LOW
diff --git a/src/clear_cmd.cpp b/src/clear_cmd.cpp
index 8e55ce4c0..81d45bbaa 100644
--- a/src/clear_cmd.cpp
+++ b/src/clear_cmd.cpp
@@ -18,6 +18,7 @@
 #include "economy_func.h"
 #include "viewport_func.h"
 #include "settings_type.h"
+#include "water.h"
 
 #include "table/strings.h"
 #include "table/sprites.h"
@@ -216,6 +217,16 @@ static void TileLoopClearDesert(TileIndex tile)
 
 static void TileLoop_Clear(TileIndex tile)
 {
+	/* If the tile is at any edge flood it to prevent maps without water. */
+	if (_settings_game.construction.freeform_edges && DistanceFromEdge(tile) == 1) {
+		uint z;
+		Slope slope = GetTileSlope(tile, &z);
+		if (z == 0 && slope == SLOPE_FLAT) {
+			DoFloodTile(tile);
+			MarkTileDirtyByTile(tile);
+			return;
+		}
+	}
 	TileLoopClearHelper(tile);
 
 	switch (_settings_game.game_creation.landscape) {
diff --git a/src/command.cpp b/src/command.cpp
index 0cb9e7640..aa0d48e42 100644
--- a/src/command.cpp
+++ b/src/command.cpp
@@ -214,7 +214,7 @@ static const Command _command_proc_table[] = {
 	{CmdBuildTrainDepot,      CMD_NO_WATER | CMD_AUTO}, /* CMD_BUILD_TRAIN_DEPOT */
 	{CmdBuildSingleSignal,                   CMD_AUTO}, /* CMD_BUILD_SIGNALS */
 	{CmdRemoveSingleSignal,                  CMD_AUTO}, /* CMD_REMOVE_SIGNALS */
-	{CmdTerraformLand,                       CMD_AUTO}, /* CMD_TERRAFORM_LAND */
+	{CmdTerraformLand,       CMD_ALL_TILES | CMD_AUTO}, /* CMD_TERRAFORM_LAND */
 	{CmdPurchaseLandArea,     CMD_NO_WATER | CMD_AUTO}, /* CMD_PURCHASE_LAND_AREA */
 	{CmdSellLandArea,                               0}, /* CMD_SELL_LAND_AREA */
 	{CmdBuildTunnel,                         CMD_AUTO}, /* CMD_BUILD_TUNNEL */
@@ -311,7 +311,7 @@ static const Command _command_proc_table[] = {
 	{CmdBuildCanal,                          CMD_AUTO}, /* CMD_BUILD_CANAL */
 	{CmdCompanyCtrl,                                0}, /* CMD_COMPANY_CTRL */
 
-	{CmdLevelLand,             CMD_NO_TEST | CMD_AUTO}, /* CMD_LEVEL_LAND; test run might clear tiles multiple times, in execution that only happens once */
+	{CmdLevelLand, CMD_ALL_TILES | CMD_NO_TEST | CMD_AUTO}, /* CMD_LEVEL_LAND; test run might clear tiles multiple times, in execution that only happens once */
 
 	{CmdRefitRailVehicle,                           0}, /* CMD_REFIT_RAIL_VEHICLE */
 	{CmdRestoreOrderIndex,                          0}, /* CMD_RESTORE_ORDER_INDEX */
@@ -403,7 +403,7 @@ CommandCost DoCommand(TileIndex tile, uint32 p1, uint32 p2, uint32 flags, uint32
 	CommandCost res;
 
 	/* Do not even think about executing out-of-bounds tile-commands */
-	if (!IsValidTile(tile)) return CMD_ERROR;
+	if (tile != 0 && (tile >= MapSize() || (!IsValidTile(tile) && (flags & DC_ALL_TILES) == 0))) return CMD_ERROR;
 
 	CommandProc *proc = _command_proc_table[cmd].proc;
 
@@ -497,9 +497,6 @@ bool DoCommandP(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallbac
 {
 	assert(_docommand_recursive == 0);
 
-	/* Do not even think about executing out-of-bounds tile-commands */
-	if (!IsValidTile(tile)) return false;
-
 	CommandCost res, res2;
 
 	int x = TileX(tile) * TILE_SIZE;
@@ -528,6 +525,9 @@ bool DoCommandP(TileIndex tile, uint32 p1, uint32 p2, uint32 cmd, CommandCallbac
 	/* Flags get send to the DoCommand */
 	uint32 flags = CommandFlagsToDCFlags(cmd_flags);
 
+	/* Do not even think about executing out-of-bounds tile-commands */
+	if (tile != 0 && (tile >= MapSize() || (!IsValidTile(tile) && (cmd_flags & CMD_ALL_TILES) == 0))) return false;
+
 	bool notest = (cmd_flags & CMD_NO_TEST) != 0;
 
 	_docommand_recursive = 1;
diff --git a/src/command_func.h b/src/command_func.h
index a6b77c6a0..d588ef807 100644
--- a/src/command_func.h
+++ b/src/command_func.h
@@ -96,6 +96,7 @@ static inline uint32 CommandFlagsToDCFlags(uint cmd_flags)
 	uint32 flags = 0;
 	if (cmd_flags & CMD_NO_WATER) flags |= DC_NO_WATER;
 	if (cmd_flags & CMD_AUTO) flags |= DC_AUTO;
+	if (cmd_flags & CMD_ALL_TILES) flags |= DC_ALL_TILES;
 	return flags;
 }
 
diff --git a/src/command_type.h b/src/command_type.h
index a4d3b295f..f64780ed7 100644
--- a/src/command_type.h
+++ b/src/command_type.h
@@ -304,6 +304,7 @@ enum {
 	DC_NO_TOWN_RATING  = 0x020, ///< town rating does not disallow you from building
 	DC_BANKRUPT        = 0x040, ///< company bankrupts, skip money check, skip vehicle on tile check in some cases
 	DC_AUTOREPLACE     = 0x080, ///< autoreplace/autorenew is in progress, this shall disable vehicle limits when building, and ignore certain restrictions when undoing things (like vehicle attach callback)
+	DC_ALL_TILES       = 0x100, ///< allow this command also on MP_VOID tiles
 };
 
 /**
@@ -340,6 +341,7 @@ enum {
 	CMD_AUTO     = 0x04, ///< set the DC_AUTO flag on this command
 	CMD_NO_TEST  = 0x08, ///< the command's output may differ between test and execute due to town rating changes etc.
 	CMD_NO_WATER = 0x10, ///< set the DC_NO_WATER flag on this command
+	CMD_ALL_TILES= 0x20, ///< allow this command also on MP_VOID tiles
 };
 
 /**
diff --git a/src/genworld.cpp b/src/genworld.cpp
index 1580dc410..a238853a1 100644
--- a/src/genworld.cpp
+++ b/src/genworld.cpp
@@ -28,6 +28,7 @@
 #include "blitter/factory.hpp"
 #include "tilehighlight_func.h"
 #include "saveload/saveload.h"
+#include "void_map.h"
 
 #include "table/sprites.h"
 
@@ -106,6 +107,12 @@ static void _GenerateWorld(void *arg)
 		if (_gw.mode == GW_EMPTY) {
 			SetGeneratingWorldProgress(GWP_UNMOVABLE, 1);
 
+			/* Make sure the tiles at the north border are void tiles if needed. */
+			if (_settings_game.construction.freeform_edges) {
+				for (uint row = 0; row < MapSizeY(); row++) MakeVoid(TileXY(0, row));
+				for (uint col = 0; col < MapSizeX(); col++) MakeVoid(TileXY(col, 0));
+			}
+
 			/* Make the map the height of the patch setting */
 			if (_game_mode != GM_MENU) FlatEmptyWorld(_settings_game.game_creation.se_flat_world_height);
 
diff --git a/src/genworld_gui.cpp b/src/genworld_gui.cpp
index 883db3239..366f58f26 100644
--- a/src/genworld_gui.cpp
+++ b/src/genworld_gui.cpp
@@ -98,13 +98,14 @@ enum GenerateLandscapeWindowWidgets {
 	GLAND_WATER_TEXT,
 	GLAND_WATER_PULLDOWN,
 	GLAND_SMOOTHNESS_TEXT,
-	GLAND_SMOOTHNESS_PULLDOWN
+	GLAND_SMOOTHNESS_PULLDOWN,
+	GLAND_WATER_BORDERS_PULLDOWN,
 };
 
 static const Widget _generate_landscape_widgets[] = {
 {  WWT_CLOSEBOX,  RESIZE_NONE, COLOUR_BROWN,    0,  10,   0,  13, STR_00C5,                     STR_018B_CLOSE_WINDOW},
 {    WWT_CAPTION, RESIZE_NONE, COLOUR_BROWN,   11, 337,   0,  13, STR_WORLD_GENERATION_CAPTION, STR_NULL},
-{      WWT_PANEL, RESIZE_NONE, COLOUR_BROWN,    0, 337,  14, 267, 0x0,                          STR_NULL},
+{      WWT_PANEL, RESIZE_NONE, COLOUR_BROWN,    0, 337,  14, 285, 0x0,                          STR_NULL},
 
 /* Landscape selection */
 {   WWT_IMGBTN_2, RESIZE_NONE, COLOUR_ORANGE,  10,  86,  24,  78, SPR_SELECT_TEMPERATE,         STR_030E_SELECT_TEMPERATE_LANDSCAPE},    // GLAND_TEMPERATE
@@ -166,6 +167,9 @@ static const Widget _generate_landscape_widgets[] = {
 /* Map smoothness */
 {       WWT_TEXT, RESIZE_NONE, COLOUR_ORANGE,  12, 110, 245, 257, STR_SMOOTHNESS,               STR_NULL},                               // GLAND_SMOOTHNESS_TEXT
 {   WWT_DROPDOWN, RESIZE_NONE, COLOUR_ORANGE, 114, 231, 246, 257, 0x0,                          STR_NULL},                               // GLAND_SMOOTHNESS_PULLDOWN
+
+/* Water borders */
+{   WWT_DROPDOWN, RESIZE_NONE, COLOUR_ORANGE,  12, 326, 264, 275, 0x0,                          STR_NULL},                               // GLAND_WATER_BORDERS_PULLDOWN
 {   WIDGETS_END},
 };
 
@@ -269,6 +273,25 @@ static const StringID _rotation[]    = {STR_CONFIG_PATCHES_HEIGHTMAP_ROTATION_CO
 static const StringID _landscape[]   = {STR_CONFIG_PATCHES_LAND_GENERATOR_ORIGINAL, STR_CONFIG_PATCHES_LAND_GENERATOR_TERRA_GENESIS, INVALID_STRING_ID};
 static const StringID _num_towns[]   = {STR_NUM_VERY_LOW, STR_6816_LOW, STR_6817_NORMAL, STR_6818_HIGH, INVALID_STRING_ID};
 static const StringID _num_inds[]    = {STR_NONE, STR_NUM_VERY_LOW, STR_6816_LOW, STR_6817_NORMAL, STR_6818_HIGH, INVALID_STRING_ID};
+static const StringID _water_borders[] = {
+	STR_CONFIG_PATCHES_WATER_BORDER_NONE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_SE,
+	STR_CONFIG_PATCHES_WATER_BORDER_SE_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_SW,
+	STR_CONFIG_PATCHES_WATER_BORDER_SW_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_SW_SE,
+	STR_CONFIG_PATCHES_WATER_BORDER_SW_SE_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SE_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SW,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_NE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_SE,
+	STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_SE_NE,
+	INVALID_STRING_ID
+};
 
 struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 	uint widget_id;
@@ -294,9 +317,10 @@ struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 
 	virtual void OnPaint()
 	{
-		/* You can't select smoothness if not terragenesis */
+		/* You can't select smoothness / non-water borders if not terragenesis */
 		if (mode == GLWP_GENERATE) {
 			this->SetWidgetDisabledState(GLAND_SMOOTHNESS_PULLDOWN, _settings_newgame.game_creation.land_generator == 0);
+			this->SetWidgetDisabledState(GLAND_WATER_BORDERS_PULLDOWN, _settings_newgame.game_creation.land_generator == 0 || !_settings_newgame.construction.freeform_edges);
 		}
 		/* Disable snowline if not hilly */
 		this->SetWidgetDisabledState(GLAND_SNOW_LEVEL_TEXT, _settings_newgame.game_creation.landscape != LT_ARCTIC);
@@ -324,11 +348,12 @@ struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 		}
 
 		if (mode == GLWP_GENERATE) {
-			this->widget[GLAND_LANDSCAPE_PULLDOWN].data  = _landscape[_settings_newgame.game_creation.land_generator];
-			this->widget[GLAND_TREE_PULLDOWN].data       = _tree_placer[_settings_newgame.game_creation.tree_placer];
-			this->widget[GLAND_TERRAIN_PULLDOWN].data    = _elevations[_settings_newgame.difficulty.terrain_type];
-			this->widget[GLAND_WATER_PULLDOWN].data      = _sea_lakes[_settings_newgame.difficulty.quantity_sea_lakes];
-			this->widget[GLAND_SMOOTHNESS_PULLDOWN].data = _smoothness[_settings_newgame.game_creation.tgen_smoothness];
+			this->widget[GLAND_LANDSCAPE_PULLDOWN].data     = _landscape[_settings_newgame.game_creation.land_generator];
+			this->widget[GLAND_TREE_PULLDOWN].data          = _tree_placer[_settings_newgame.game_creation.tree_placer];
+			this->widget[GLAND_TERRAIN_PULLDOWN].data       = _elevations[_settings_newgame.difficulty.terrain_type];
+			this->widget[GLAND_WATER_PULLDOWN].data         = _sea_lakes[_settings_newgame.difficulty.quantity_sea_lakes];
+			this->widget[GLAND_SMOOTHNESS_PULLDOWN].data    = _smoothness[_settings_newgame.game_creation.tgen_smoothness];
+			this->widget[GLAND_WATER_BORDERS_PULLDOWN].data = _settings_newgame.construction.freeform_edges ? _water_borders[_settings_newgame.game_creation.water_borders] : STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_SE_NE;
 		} else {
 			this->widget[GLAND_TREE_PULLDOWN].data               = _tree_placer[_settings_newgame.game_creation.tree_placer];
 			this->widget[GLAND_HEIGHTMAP_ROTATION_PULLDOWN].data = _rotation[_settings_newgame.game_creation.heightmap_rotation];
@@ -483,6 +508,10 @@ struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 			case GLAND_SMOOTHNESS_PULLDOWN: // Map smoothness
 				ShowDropDownMenu(this, _smoothness, _settings_newgame.game_creation.tgen_smoothness, GLAND_SMOOTHNESS_PULLDOWN, 0, 0);
 				break;
+
+			case GLAND_WATER_BORDERS_PULLDOWN: // Water borders
+				ShowDropDownMenu(this, _water_borders, _settings_newgame.game_creation.water_borders, GLAND_WATER_BORDERS_PULLDOWN, 0, 0);
+				break;
 		}
 	}
 
@@ -507,10 +536,11 @@ struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 	virtual void OnDropdownSelect(int widget, int index)
 	{
 		switch (widget) {
-			case GLAND_MAPSIZE_X_PULLDOWN:  _settings_newgame.game_creation.map_x = index; break;
-			case GLAND_MAPSIZE_Y_PULLDOWN:  _settings_newgame.game_creation.map_y = index; break;
-			case GLAND_TREE_PULLDOWN:       _settings_newgame.game_creation.tree_placer = index; break;
-			case GLAND_SMOOTHNESS_PULLDOWN: _settings_newgame.game_creation.tgen_smoothness = index;  break;
+			case GLAND_MAPSIZE_X_PULLDOWN:     _settings_newgame.game_creation.map_x = index; break;
+			case GLAND_MAPSIZE_Y_PULLDOWN:     _settings_newgame.game_creation.map_y = index; break;
+			case GLAND_TREE_PULLDOWN:          _settings_newgame.game_creation.tree_placer = index; break;
+			case GLAND_SMOOTHNESS_PULLDOWN:    _settings_newgame.game_creation.tgen_smoothness = index;  break;
+			case GLAND_WATER_BORDERS_PULLDOWN: _settings_newgame.game_creation.water_borders = index;  break;
 
 			case GLAND_TOWN_PULLDOWN:
 				_settings_newgame.difficulty.number_towns = index;
@@ -571,7 +601,7 @@ struct GenerateLandscapeWindow : public QueryStringBaseWindow {
 };
 
 static const WindowDesc _generate_landscape_desc = {
-	WDP_CENTER, WDP_CENTER, 338, 268, 338, 268,
+	WDP_CENTER, WDP_CENTER, 338, 286, 338, 286,
 	WC_GENERATE_LANDSCAPE, WC_NONE,
 	WDF_STD_TOOLTIPS | WDF_DEF_WIDGET | WDF_UNCLICK_BUTTONS,
 	_generate_landscape_widgets,
diff --git a/src/heightmap.cpp b/src/heightmap.cpp
index 2ca58b14c..2a4186aa6 100644
--- a/src/heightmap.cpp
+++ b/src/heightmap.cpp
@@ -319,9 +319,14 @@ static void GrayscaleToMapHeights(uint img_width, uint img_height, byte *map)
 		col_pad = (1 + width - ((img_width * img_scale) / num_div)) / 2;
 	}
 
+	if (_settings_game.construction.freeform_edges) {
+		for (uint x = 0; x < MapSizeX(); x++) MakeVoid(TileXY(x, 0));
+		for (uint y = 0; y < MapSizeY(); y++) MakeVoid(TileXY(0, y));
+	}
+
 	/* Form the landscape */
-	for (row = 0; row < height - 1; row++) {
-		for (col = 0; col < width - 1; col++) {
+	for (row = 0; row < height; row++) {
+		for (col = 0; col < width; col++) {
 			switch (_settings_game.game_creation.heightmap_rotation) {
 				default: NOT_REACHED();
 				case HM_COUNTER_CLOCKWISE: tile = TileXY(col, row); break;
@@ -329,7 +334,7 @@ static void GrayscaleToMapHeights(uint img_width, uint img_height, byte *map)
 			}
 
 			/* Check if current tile is within the 1-pixel map edge or padding regions */
-			if ((DistanceFromEdge(tile) <= 1) ||
+			if ((!_settings_game.construction.freeform_edges && DistanceFromEdge(tile) <= 1) ||
 					(row < row_pad) || (row >= (height - row_pad - 1)) ||
 					(col < col_pad) || (col >= (width  - col_pad - 1))) {
 				SetTileHeight(tile, 0);
@@ -353,7 +358,11 @@ static void GrayscaleToMapHeights(uint img_width, uint img_height, byte *map)
 				/* Color scales from 0 to 255, OpenTTD height scales from 0 to 15 */
 				SetTileHeight(tile, map[img_row * img_width + img_col] / 16);
 			}
-			MakeClear(tile, CLEAR_GRASS, 3);
+			/* Only clear the tiles within the map area. */
+			if (TileX(tile) != MapMaxX() && TileY(tile) != MapMaxY() &&
+					(!_settings_game.construction.freeform_edges || (TileX(tile) != 0 && TileY(tile) != 0))) {
+				MakeClear(tile, CLEAR_GRASS, 3);
+			}
 		}
 	}
 }
@@ -365,7 +374,7 @@ static void GrayscaleToMapHeights(uint img_width, uint img_height, byte *map)
 static void FixSlopes()
 {
 	uint width, height;
-	uint row, col;
+	int row, col;
 	byte current_tile;
 
 	/* Adjust height difference to maximum one horizontal/vertical change. */
@@ -373,12 +382,17 @@ static void FixSlopes()
 	height  = MapSizeY();
 
 	/* Top and left edge */
-	for (row = 1; row < height - 2; row++) {
-		for (col = 1; col < width - 2; col++) {
-			/* Find lowest tile; either the top or left one */
-			current_tile = TileHeight(TileXY(col - 1, row)); // top edge
-			if (TileHeight(TileXY(col, row - 1)) < current_tile) {
-				current_tile = TileHeight(TileXY(col, row - 1)); // left edge
+	for (row = 0; (uint)row < height; row++) {
+		for (col = 0; (uint)col < width; col++) {
+			current_tile = MAX_TILE_HEIGHT;
+			if (col != 0) {
+				/* Find lowest tile; either the top or left one */
+				current_tile = TileHeight(TileXY(col - 1, row)); // top edge
+			}
+			if (row != 0) {
+				if (TileHeight(TileXY(col, row - 1)) < current_tile) {
+					current_tile = TileHeight(TileXY(col, row - 1)); // left edge
+				}
 			}
 
 			/* Does the height differ more than one? */
@@ -390,12 +404,18 @@ static void FixSlopes()
 	}
 
 	/* Bottom and right edge */
-	for (row = height - 2; row > 0; row--) {
-		for (col = width - 2; col > 0; col--) {
-			/* Find lowest tile; either the bottom and right one */
-			current_tile = TileHeight(TileXY(col + 1, row)); // bottom edge
-			if (TileHeight(TileXY(col, row + 1)) < current_tile) {
-				current_tile = TileHeight(TileXY(col, row + 1)); // right edge
+	for (row = height - 1; row >= 0; row--) {
+		for (col = width - 1; col >= 0; col--) {
+			current_tile = MAX_TILE_HEIGHT;
+			if ((uint)col != width - 1) {
+				/* Find lowest tile; either the bottom and right one */
+				current_tile = TileHeight(TileXY(col + 1, row)); // bottom edge
+			}
+
+			if ((uint)row != height - 1) {
+				if (TileHeight(TileXY(col, row + 1)) < current_tile) {
+					current_tile = TileHeight(TileXY(col, row + 1)); // right edge
+				}
 			}
 
 			/* Does the height differ more than one? */
@@ -447,14 +467,9 @@ void LoadHeightmap(char *filename)
 
 void FlatEmptyWorld(byte tile_height)
 {
-	uint width, height;
-	uint row, col;
-
-	width  = MapSizeX();
-	height = MapSizeY();
-
-	for (row = 2; row < height - 2; row++) {
-		for (col = 2; col < width - 2; col++) {
+	int edge_distance = _settings_game.construction.freeform_edges ? 0 : 2;
+	for (uint row = edge_distance; row < MapSizeY() - edge_distance; row++) {
+		for (uint col = edge_distance; col < MapSizeX() - edge_distance; col++) {
 			SetTileHeight(TileXY(col, row), tile_height);
 		}
 	}
diff --git a/src/industry_cmd.cpp b/src/industry_cmd.cpp
index 67afd3f3f..45def31e5 100644
--- a/src/industry_cmd.cpp
+++ b/src/industry_cmd.cpp
@@ -930,6 +930,8 @@ static void PlantFarmField(TileIndex tile, IndustryID industry)
 	/* offset tile to match size */
 	tile -= TileDiffXY(size_x / 2, size_y / 2);
 
+	if (TileX(tile) + size_x >= MapSizeX() || TileY(tile) + size_y >= MapSizeY()) return;
+
 	/* check the amount of bad tiles */
 	count = 0;
 	BEGIN_TILE_LOOP(cur_tile, size_x, size_y, tile)
@@ -1179,19 +1181,6 @@ static CheckNewIndustryProc * const _check_new_industry_procs[CHECK_END] = {
 	CheckNewIndustry_OilRig
 };
 
-static bool CheckSuitableIndustryPos(TileIndex tile)
-{
-	uint x = TileX(tile);
-	uint y = TileY(tile);
-
-	if (x < 2 || y < 2 || x > MapMaxX() - 3 || y > MapMaxY() - 3) {
-		_error_message = STR_0239_SITE_UNSUITABLE;
-		return false;
-	}
-
-	return true;
-}
-
 static const Town *CheckMultipleIndustryInTown(TileIndex tile, int type)
 {
 	const Town *t;
@@ -1237,6 +1226,8 @@ static bool CheckIfIndustryTilesAreFree(TileIndex tile, const IndustryTileTable
 
 	do {
 		IndustryGfx gfx = GetTranslatedIndustryTileID(it->gfx);
+		if (TileX(tile) + it->ti.x >= MapSizeX()) return false;
+		if (TileY(tile) + it->ti.y >= MapSizeY()) return false;
 		TileIndex cur_tile = tile + ToTileIndexDiff(it->ti);
 
 		if (!IsValidTile(cur_tile)) {
@@ -1342,7 +1333,7 @@ static bool CheckCanTerraformSurroundingTiles(TileIndex tile, uint height, int i
 		 *  has to be correct too (in level, or almost in level)
 		 *  else you get a chain-reaction of terraforming. */
 		if (internal == 0 && curh != height) {
-			if (!CheckCanTerraformSurroundingTiles(tile_walk + TileDiffXY(-1, -1), height, internal + 1))
+			if (TileX(tile_walk) == 0 || TileY(tile_walk) == 0 || !CheckCanTerraformSurroundingTiles(tile_walk + TileDiffXY(-1, -1), height, internal + 1))
 				return false;
 		}
 	} END_TILE_LOOP(tile_walk, size_x, size_y, tile);
@@ -1373,6 +1364,7 @@ static bool CheckIfCanLevelIndustryPlatform(TileIndex tile, uint32 flags, const
 	/* Remember level height */
 	h = TileHeight(tile);
 
+	if (TileX(tile) <= 1 || TileY(tile) <= 1) return false;
 	/* Check that all tiles in area and surrounding are clear
 	 * this determines that there are no obstructing items */
 	cur_tile = tile + TileDiffXY(-1, -1);
@@ -1380,7 +1372,7 @@ static bool CheckIfCanLevelIndustryPlatform(TileIndex tile, uint32 flags, const
 	size_y = max_y + 4;
 
 	/* Check if we don't leave the map */
-	if (TileX(cur_tile) == 0 || TileY(cur_tile) == 0 || TileX(cur_tile) + size_x >= MapMaxX() || TileY(cur_tile) + size_y >= MapMaxY()) return false;
+	if (TileX(cur_tile) + size_x >= MapMaxX() || TileY(cur_tile) + size_y >= MapMaxY()) return false;
 
 	/* _current_company is OWNER_NONE for randomly generated industries and in editor, or the company who funded or prospected the industry.
 	 * Perform terraforming as OWNER_TOWN to disable autoslope. */
@@ -1632,7 +1624,6 @@ static Industry *CreateNewIndustryHelper(TileIndex tile, IndustryType type, uint
 	if (t == NULL) return NULL;
 
 	if (!CheckIfIndustryIsAllowed(tile, type, t)) return NULL;
-	if (!CheckSuitableIndustryPos(tile)) return NULL;
 
 	if (!Industry::CanAllocateItem()) return NULL;
 
diff --git a/src/landscape.cpp b/src/landscape.cpp
index e2e7d2504..900ec71fd 100644
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -690,9 +690,9 @@ void InitializeLandscape()
 	uint sizex = MapSizeX();
 
 	uint y;
-	for (y = 0; y < maxy; y++) {
+	for (y = _settings_game.construction.freeform_edges ? 1 : 0; y < maxy; y++) {
 		uint x;
-		for (x = 0; x < maxx; x++) {
+		for (x = _settings_game.construction.freeform_edges ? 1 : 0; x < maxx; x++) {
 			MakeClear(sizex * y + x, CLEAR_GRASS, 3);
 			SetTileHeight(sizex * y + x, 0);
 			SetTropicZone(sizex * y + x, TROPICZONE_NORMAL);
diff --git a/src/lang/english.txt b/src/lang/english.txt
index 6b89e7609..b10a226d2 100644
--- a/src/lang/english.txt
+++ b/src/lang/english.txt
@@ -1090,6 +1090,29 @@ STR_CONFIG_PATCHES_HEIGHTMAP_ROTATION                           :{LTBLUE}Heightm
 STR_CONFIG_PATCHES_HEIGHTMAP_ROTATION_COUNTER_CLOCKWISE         :Counter clockwise
 STR_CONFIG_PATCHES_HEIGHTMAP_ROTATION_CLOCKWISE                 :Clockwise
 STR_CONFIG_PATCHES_SE_FLAT_WORLD_HEIGHT                         :{LTBLUE}The height level a flat scenario map gets: {ORANGE}{STRING1}
+STR_CONFIG_PATCHES_ENABLE_FREEFORM_EDGES                        :{LTBLUE}Enable terraforming the tiles at the map borders
+STR_CONFIG_PATCHES_EDGES_NOT_EMPTY                              :{WHITE}One or more tiles at the northern edge are not empty
+STR_CONFIG_PATCHES_EDGES_NOT_WATER                              :{WHITE}One or more tiles at one of the edges is not water
+
+# Start of map water border strings.
+# DON'T ADD OR REMOVE LINES HERE
+STR_CONFIG_PATCHES_WATER_BORDER_NONE                            :Land at all borders
+STR_CONFIG_PATCHES_WATER_BORDER_NE                              :Water at north-east border only
+STR_CONFIG_PATCHES_WATER_BORDER_SE                              :Water at south-east border only
+STR_CONFIG_PATCHES_WATER_BORDER_SE_NE                           :Water at north-east and south-east borders
+STR_CONFIG_PATCHES_WATER_BORDER_SW                              :Water at south-west border only
+STR_CONFIG_PATCHES_WATER_BORDER_SW_NE                           :Water at north-east and south-west borders
+STR_CONFIG_PATCHES_WATER_BORDER_SW_SE                           :Water at south-east and south-west borders
+STR_CONFIG_PATCHES_WATER_BORDER_SW_SE_NE                        :Land only at north-west border
+STR_CONFIG_PATCHES_WATER_BORDER_NW                              :Water at north-west border only
+STR_CONFIG_PATCHES_WATER_BORDER_NW_NE                           :Water at north-west and north-east borders
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SE                           :Water at north-west and south-east borders
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SE_NE                        :Land only at south-west border
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SW                           :Water at north-west and south-west borders
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_NE                        :Land only at south-east border
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_SE                        :Land only at north-east border
+STR_CONFIG_PATCHES_WATER_BORDER_NW_SW_SE_NE                     :Water at all borders
+# End of map water border strings.
 
 STR_CONFIG_PATCHES_STATION_SPREAD                               :{LTBLUE}Max station spread: {ORANGE}{STRING1} {RED}Warning: High setting slows game
 STR_CONFIG_PATCHES_SERVICEATHELIPAD                             :{LTBLUE}Service helicopters at helipads automatically: {ORANGE}{STRING1}
@@ -2118,6 +2141,7 @@ STR_INDUSTRY_PROD_GODOWN                                        :{BLACK}{BIGFONT
 STR_5000_TRAIN_IN_TUNNEL                                        :{WHITE}Train in tunnel
 STR_5001_ROAD_VEHICLE_IN_TUNNEL                                 :{WHITE}Road vehicle in tunnel
 STR_5003_ANOTHER_TUNNEL_IN_THE_WAY                              :{WHITE}Another tunnel in the way
+STR_TUNNEL_THROUGH_MAP_BORDER                                   :{WHITE}Tunnel would end out of the map
 STR_5005_UNABLE_TO_EXCAVATE_LAND                                :{WHITE}Unable to excavate land for other end of tunnel
 STR_5006_MUST_DEMOLISH_TUNNEL_FIRST                             :{WHITE}Must demolish tunnel first
 STR_5007_MUST_DEMOLISH_BRIDGE_FIRST                             :{WHITE}Must demolish bridge first
diff --git a/src/newgrf_industries.cpp b/src/newgrf_industries.cpp
index da74f58d3..d65570c93 100644
--- a/src/newgrf_industries.cpp
+++ b/src/newgrf_industries.cpp
@@ -59,6 +59,7 @@ static uint GetClosestWaterDistance(TileIndex tile, bool water)
 
 	uint max_x = MapMaxX();
 	uint max_y = MapMaxY();
+	uint min_xy = _settings_game.construction.freeform_edges ? 1 : 0;
 
 	/* go in a 'spiral' with increasing manhattan distance in each iteration */
 	for (uint dist = 1; dist < max_dist; dist++) {
@@ -75,8 +76,8 @@ static uint GetClosestWaterDistance(TileIndex tile, bool water)
 
 			/* each side of this square has length 'dist' */
 			for (uint a = 0; a < dist; a++) {
-				/* MP_VOID tiles are not checked (interval is [0; max) for IsInsideMM())*/
-				if (IsInsideMM(x, 0, max_x) && IsInsideMM(y, 0, max_y)) {
+				/* MP_VOID tiles are not checked (interval is [min; max) for IsInsideMM())*/
+				if (IsInsideMM(x, min_xy, max_x) && IsInsideMM(y, min_xy, max_y)) {
 					TileIndex t = TileXY(x, y);
 					if (IsTileType(t, MP_WATER) == water) return dist;
 				}
diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index d19adc190..bbff67644 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -659,6 +659,11 @@ bool AfterLoadGame()
 		}
 	}
 
+	/* Force the freeform edges to false for old savegames. */
+	if (CheckSavegameVersion(111)) {
+		_settings_game.construction.freeform_edges = false;
+	}
+
 	/* From version 9.0, we update the max passengers of a town (was sometimes negative
 	 *  before that. */
 	if (CheckSavegameVersion(9)) {
diff --git a/src/saveload/saveload.cpp b/src/saveload/saveload.cpp
index b7dc4e9a9..58cc791c5 100644
--- a/src/saveload/saveload.cpp
+++ b/src/saveload/saveload.cpp
@@ -42,7 +42,7 @@
 
 #include <list>
 
-extern const uint16 SAVEGAME_VERSION = 110;
+extern const uint16 SAVEGAME_VERSION = 111;
 
 SavegameType _savegame_type; ///< type of savegame we are loading
 
diff --git a/src/settings.cpp b/src/settings.cpp
index 6440a7687..3a90f9651 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -68,6 +68,10 @@
 #include "ai/ai_config.hpp"
 #include "ai/ai_info.hpp"
 
+#include "tile_map.h"
+#include "void_map.h"
+#include "station_base.h"
+
 #include "table/strings.h"
 
 ClientSettings _settings_client;
@@ -1079,6 +1083,71 @@ static int32 CheckNoiseToleranceLevel(const char *value)
 	return 0;
 }
 
+static int32 CheckFreeformEdges(int32 p1)
+{
+	if (_game_mode == GM_MENU) return 0;
+	if (p1 != 0) {
+		Vehicle *v;
+		FOR_ALL_VEHICLES(v) {
+			if (v->type == VEH_SHIP && (TileX(v->tile) == 0 || TileY(v->tile) == 0)) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_EMPTY, 0, 0);
+				_settings_game.construction.freeform_edges = false;
+				return 0;
+			}
+		}
+		Station *st;
+		FOR_ALL_STATIONS(st) {
+			if (TileX(st->xy) == 0 || TileY(st->xy) == 0) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_EMPTY, 0, 0);
+				_settings_game.construction.freeform_edges = false;
+				return 0;
+			}
+		}
+		for (uint i = 0; i < MapSizeX(); i++) MakeVoid(TileXY(i, 0));
+		for (uint i = 0; i < MapSizeY(); i++) MakeVoid(TileXY(0, i));
+	} else {
+		for (uint i = 0; i < MapMaxX(); i++) {
+			if (TileHeight(TileXY(i, 1)) != 0) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_WATER, 0, 0);
+				_settings_game.construction.freeform_edges = true;
+				return 0;
+			}
+		}
+		for (uint i = 1; i < MapMaxX(); i++) {
+			if (!IsTileType(TileXY(i, MapMaxY() - 1), MP_WATER) || TileHeight(TileXY(1, MapMaxY())) != 0) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_WATER, 0, 0);
+				_settings_game.construction.freeform_edges = true;
+				return 0;
+			}
+		}
+		for (uint i = 0; i < MapMaxY(); i++) {
+			if (TileHeight(TileXY(1, i)) != 0) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_WATER, 0, 0);
+				_settings_game.construction.freeform_edges = true;
+				return 0;
+			}
+		}
+		for (uint i = 1; i < MapMaxY(); i++) {
+			if (!IsTileType(TileXY(MapMaxX() - 1, i), MP_WATER) || TileHeight(TileXY(MapMaxX(), i)) != 0) {
+				ShowErrorMessage(INVALID_STRING_ID, STR_CONFIG_PATCHES_EDGES_NOT_WATER, 0, 0);
+				_settings_game.construction.freeform_edges = true;
+				return 0;
+			}
+		}
+		/* Make tiles at the border water again. */
+		for (uint i = 0; i < MapMaxX(); i++) {
+			SetTileHeight(TileXY(i, 0), 0);
+			SetTileType(TileXY(i, 0), MP_WATER);
+		}
+		for (uint i = 0; i < MapMaxY(); i++) {
+			SetTileHeight(TileXY(0, i), 0);
+			SetTileType(TileXY(0, i), MP_WATER);
+		}
+	}
+	MarkWholeScreenDirty();
+	return 0;
+}
+
 #ifdef ENABLE_NETWORK
 
 static int32 UpdateMinActiveClients(int32 p1)
@@ -1396,6 +1465,8 @@ const SettingDesc _patch_settings[] = {
 
 	     SDT_VAR(GameSettings, game_creation.map_x,                           SLE_UINT8,                     S, 0,     8,                     6,      11, 0, STR_CONFIG_PATCHES_MAP_X,                 NULL),
 	     SDT_VAR(GameSettings, game_creation.map_y,                           SLE_UINT8,                     S, 0,     8,                     6,      11, 0, STR_CONFIG_PATCHES_MAP_Y,                 NULL),
+	SDT_CONDBOOL(GameSettings, construction.freeform_edges,                             111, SL_MAX_VERSION, 0, 0, false,                                    STR_CONFIG_PATCHES_ENABLE_FREEFORM_EDGES, CheckFreeformEdges),
+	 SDT_CONDVAR(GameSettings, game_creation.water_borders,                   SLE_UINT8,111, SL_MAX_VERSION, 0, 0,    15,                     0,      15, 0, STR_NULL,                                 NULL),
 
  SDT_CONDOMANY(GameSettings, locale.currency,                               SLE_UINT8, 97, SL_MAX_VERSION, N, 0, 0, CUSTOM_CURRENCY_ID, "GBP|USD|EUR|YEN|ATS|BEF|CHF|CZK|DEM|DKK|ESP|FIM|FRF|GRD|HUF|ISK|ITL|NLG|NOK|PLN|ROL|RUR|SIT|SEK|YTL|SKK|BRR|custom", STR_NULL, NULL, NULL),
  SDT_CONDOMANY(GameSettings, locale.units,                                  SLE_UINT8, 97, SL_MAX_VERSION, N, 0, 1, 2, "imperial|metric|si", STR_NULL, NULL, NULL),
diff --git a/src/settings_gui.cpp b/src/settings_gui.cpp
index fc455ceb3..22891b0e3 100644
--- a/src/settings_gui.cpp
+++ b/src/settings_gui.cpp
@@ -1066,6 +1066,7 @@ static PatchEntry _patches_construction[] = {
 	PatchEntry("construction.extra_dynamite"),
 	PatchEntry("construction.longbridges"),
 	PatchEntry("station.always_small_airport"),
+	PatchEntry("construction.freeform_edges"),
 };
 /** Construction sub-page */
 static PatchPage _patches_construction_page = {_patches_construction, lengthof(_patches_construction)};
diff --git a/src/settings_type.h b/src/settings_type.h
index ab5a87d4c..a67128787 100644
--- a/src/settings_type.h
+++ b/src/settings_type.h
@@ -154,6 +154,7 @@ struct GameCreationSettings {
 	byte   town_name;                        ///< the town name generator used for town names
 	byte   landscape;                        ///< the landscape we're currently in
 	byte   snow_line;                        ///< the snowline level in this game
+	byte   water_borders;                    ///< bitset of the borders that are water
 };
 
 /** Settings related to construction in-game */
@@ -165,6 +166,7 @@ struct ConstructionSettings {
 	bool   extra_dynamite;                   ///< extra dynamite
 	bool   road_stop_on_town_road;           ///< allow building of drive-through road stops on town owned roads
 	uint8  raw_industry_construction;        ///< type of (raw) industry construction (none, "normal", prospecting)
+	bool   freeform_edges;                   ///< allow terraforming the tiles at the map edges
 };
 
 /** Settings related to the AI. */
diff --git a/src/sound.cpp b/src/sound.cpp
index cd795560d..429710f66 100644
--- a/src/sound.cpp
+++ b/src/sound.cpp
@@ -237,8 +237,8 @@ static void SndPlayScreenCoordFx(SoundFx sound, int left, int right, int top, in
 void SndPlayTileFx(SoundFx sound, TileIndex tile)
 {
 	/* emits sound from center of the tile */
-	int x = TileX(tile) * TILE_SIZE + TILE_SIZE / 2;
-	int y = TileY(tile) * TILE_SIZE - TILE_SIZE / 2;
+	int x = min(MapMaxX() - 1, TileX(tile)) * TILE_SIZE + TILE_SIZE / 2;
+	int y = min(MapMaxY() - 1, TileY(tile)) * TILE_SIZE - TILE_SIZE / 2;
 	uint z = (y < 0 ? 0 : GetSlopeZ(x, y));
 	Point pt = RemapCoords(x, y, z);
 	y += 2 * TILE_SIZE;
diff --git a/src/terraform_cmd.cpp b/src/terraform_cmd.cpp
index 25c193299..337eca2fd 100644
--- a/src/terraform_cmd.cpp
+++ b/src/terraform_cmd.cpp
@@ -130,9 +130,10 @@ static void TerraformAddDirtyTile(TerraformerState *ts, TileIndex tile)
  */
 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));
+	/* Make sure all tiles passed to TerraformAddDirtyTile are within [0, MapSize()] */
+	if (TileY(tile) >= 1) TerraformAddDirtyTile(ts, tile + TileDiffXY( 0, -1));
+	if (TileY(tile) >= 1 && TileX(tile) >= 1) TerraformAddDirtyTile(ts, tile + TileDiffXY(-1, -1));
+	if (TileX(tile) >= 1) TerraformAddDirtyTile(ts, tile + TileDiffXY(-1,  0));
 	TerraformAddDirtyTile(ts, tile);
 }
 
@@ -159,10 +160,10 @@ static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int
 	 */
 	if (height == TerraformGetHeightOfTile(ts, tile)) return CMD_ERROR;
 
-	/* Check "too close to edge of map" */
+	/* Check "too close to edge of map". Only possible when freeform-edges is off. */
 	uint x = TileX(tile);
 	uint y = TileY(tile);
-	if ((x <= 1) || (y <= 1) || (x >= MapMaxX() - 1) || (y >= MapMaxY() - 1)) {
+	if (!_settings_game.construction.freeform_edges && ((x <= 1) || (y <= 1) || (x >= MapMaxX() - 1) || (y >= MapMaxY() - 1))) {
 		/*
 		 * Determine a sensible error tile
 		 */
@@ -187,6 +188,7 @@ static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int
 	{
 		const TileIndexDiffC *ttm;
 
+		TileIndex orig_tile = tile;
 		static const TileIndexDiffC _terraform_tilepos[] = {
 			{ 1,  0}, // move to tile in SE
 			{-2,  0}, // undo last move, and move to tile in NW
@@ -197,6 +199,11 @@ static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int
 		for (ttm = _terraform_tilepos; ttm != endof(_terraform_tilepos); ttm++) {
 			tile += ToTileIndexDiff(*ttm);
 
+			if (tile >= MapSize()) continue;
+			/* Make sure we don't wrap around the map */
+			if (Delta(TileX(orig_tile), TileX(tile)) == MapSizeX() - 1) continue;
+			if (Delta(TileY(orig_tile), TileY(tile)) == MapSizeY() - 1) continue;
+
 			/* Get TileHeight of neighboured tile as of current terraform progress */
 			int r = TerraformGetHeightOfTile(ts, tile);
 			int height_diff = height - r;
@@ -224,9 +231,6 @@ static CommandCost TerraformTileHeight(TerraformerState *ts, TileIndex tile, int
  */
 CommandCost CmdTerraformLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2, const char *text)
 {
-	/* Make an extra check for map-bounds cause we add tiles to the originating tile */
-	if (tile + TileDiffXY(1, 1) >= MapSize()) return CMD_ERROR;
-
 	_terraform_err_tile = INVALID_TILE;
 
 	CommandCost total_cost(EXPENSES_CONSTRUCTION);
@@ -271,6 +275,11 @@ CommandCost CmdTerraformLand(TileIndex tile, uint32 flags, uint32 p1, uint32 p2,
 		for (int count = ts.tile_table_count; count != 0; count--, ti++) {
 			TileIndex tile = *ti;
 
+			assert(tile < MapSize());
+			/* MP_VOID tiles can be terraformed but as tunnels and bridges
+			 * cannot go under / over these tiles they don't need checking. */
+			if (IsTileType(tile, MP_VOID)) continue;
+
 			/* Find new heights of tile corners */
 			uint z_N = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(0, 0));
 			uint z_W = TerraformGetHeightOfTile(&ts, tile + TileDiffXY(1, 0));
diff --git a/src/terraform_gui.cpp b/src/terraform_gui.cpp
index b0aa2e11a..5a9a1cf40 100644
--- a/src/terraform_gui.cpp
+++ b/src/terraform_gui.cpp
@@ -113,10 +113,12 @@ static void GenerateRockyArea(TileIndex end, TileIndex start)
  **/
 bool GUIPlaceProcDragXY(ViewportDragDropSelectionProcess proc, TileIndex start_tile, TileIndex end_tile)
 {
-	/* When end_tile is MP_VOID, the DoCommandP checks will deny this command without any
-	 * user-visible reason. This happens when terraforming at the southern border. */
-	if (TileX(end_tile) == MapMaxX()) end_tile += TileDiffXY(-1, 0);
-	if (TileY(end_tile) == MapMaxY()) end_tile += TileDiffXY(0, -1);
+	if (!_settings_game.construction.freeform_edges) {
+		/* When end_tile is MP_VOID, the error tile will not be visible to the
+		 * user. This happens when terraforming at the southern border. */
+		if (TileX(end_tile) == MapMaxX()) end_tile += TileDiffXY(-1, 0);
+		if (TileY(end_tile) == MapMaxY()) end_tile += TileDiffXY(0, -1);
+	}
 
 	switch (proc) {
 		case DDSP_DEMOLISH_AREA:
@@ -378,8 +380,8 @@ static void CommonRaiseLowerBigLand(TileIndex tile, int mode)
 	} else {
 		assert(_terraform_size != 0);
 		/* check out for map overflows */
-		sizex = min(MapSizeX() - TileX(tile) - 1, _terraform_size);
-		sizey = min(MapSizeY() - TileY(tile) - 1, _terraform_size);
+		sizex = min(MapSizeX() - TileX(tile), _terraform_size);
+		sizey = min(MapSizeY() - TileY(tile), _terraform_size);
 
 		if (sizex == 0 || sizey == 0) return;
 
diff --git a/src/tgp.cpp b/src/tgp.cpp
index 18e4026d8..e72acf5e0 100644
--- a/src/tgp.cpp
+++ b/src/tgp.cpp
@@ -552,6 +552,13 @@ static void HeightMapAdjustWaterLevel(amplitude_t water_percent, height_t h_max_
 
 static double perlin_coast_noise_2D(const double x, const double y, const double p, const int prime);
 
+enum Borders {
+	BORDER_NE = 0,
+	BORDER_SE = 1,
+	BORDER_SW = 2,
+	BORDER_NW = 3,
+};
+
 /**
  * This routine sculpts in from the edge a random amount, again a Perlin
  * sequence, to avoid the rigid flat-edge slopes that were present before. The
@@ -572,7 +579,7 @@ static double perlin_coast_noise_2D(const double x, const double y, const double
  * Please note that all the small numbers; 53, 101, 167, etc. are small primes
  * to help give the perlin noise a bit more of a random feel.
  */
-static void HeightMapCoastLines()
+static void HeightMapCoastLines(uint8 water_borders)
 {
 	int smallest_size = min(_settings_game.game_creation.map_x, _settings_game.game_creation.map_y);
 	const int margin = 4;
@@ -582,40 +589,47 @@ static void HeightMapCoastLines()
 
 	/* Lower to sea level */
 	for (y = 0; y <= _height_map.size_y; y++) {
-		/* Top right */
-		max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.9, 53) + 0.25) * 5 + (perlin_coast_noise_2D(y, y, 0.35, 179) + 1) * 12);
-		max_x = max((smallest_size * smallest_size / 16) + max_x, (smallest_size * smallest_size / 16) + margin - max_x);
-		if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
-		for (x = 0; x < max_x; x++) {
-			_height_map.height(x, y) = 0;
+		if (HasBit(water_borders, BORDER_NE)) {
+			/* Top right */
+			max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.9, 53) + 0.25) * 5 + (perlin_coast_noise_2D(y, y, 0.35, 179) + 1) * 12);
+			max_x = max((smallest_size * smallest_size / 16) + max_x, (smallest_size * smallest_size / 16) + margin - max_x);
+			if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
+			for (x = 0; x < max_x; x++) {
+				_height_map.height(x, y) = 0;
+			}
 		}
 
-		/* Bottom left */
-		max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.85, 101) + 0.3) * 6 + (perlin_coast_noise_2D(y, y, 0.45,  67) + 0.75) * 8);
-		max_x = max((smallest_size * smallest_size / 16) + max_x, (smallest_size * smallest_size / 16) + margin - max_x);
-		if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
-		for (x = _height_map.size_x; x > (_height_map.size_x - 1 - max_x); x--) {
-			_height_map.height(x, y) = 0;
+		if (HasBit(water_borders, BORDER_SW)) {
+			/* Bottom left */
+			max_x = abs((perlin_coast_noise_2D(_height_map.size_y - y, y, 0.85, 101) + 0.3) * 6 + (perlin_coast_noise_2D(y, y, 0.45,  67) + 0.75) * 8);
+			max_x = max((smallest_size * smallest_size / 16) + max_x, (smallest_size * smallest_size / 16) + margin - max_x);
+			if (smallest_size < 8 && max_x > 5) max_x /= 1.5;
+			for (x = _height_map.size_x; x > (_height_map.size_x - 1 - max_x); x--) {
+				_height_map.height(x, y) = 0;
+			}
 		}
 	}
 
 	/* Lower to sea level */
 	for (x = 0; x <= _height_map.size_x; x++) {
-		/* Top left */
-		max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 2, 0.9, 167) + 0.4) * 5 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.4, 211) + 0.7) * 9);
-		max_y = max((smallest_size * smallest_size / 16) + max_y, (smallest_size * smallest_size / 16) + margin - max_y);
-		if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
-		for (y = 0; y < max_y; y++) {
-			_height_map.height(x, y) = 0;
+		if (HasBit(water_borders, BORDER_NW)) {
+			/* Top left */
+			max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 2, 0.9, 167) + 0.4) * 5 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.4, 211) + 0.7) * 9);
+			max_y = max((smallest_size * smallest_size / 16) + max_y, (smallest_size * smallest_size / 16) + margin - max_y);
+			if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
+			for (y = 0; y < max_y; y++) {
+				_height_map.height(x, y) = 0;
+			}
 		}
 
-
-		/* Bottom right */
-		max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.85, 71) + 0.25) * 6 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.35, 193) + 0.75) * 12);
-		max_y = max((smallest_size * smallest_size / 16) + max_y, (smallest_size * smallest_size / 16) + margin - max_y);
-		if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
-		for (y = _height_map.size_y; y > (_height_map.size_y - 1 - max_y); y--) {
-			_height_map.height(x, y) = 0;
+		if (HasBit(water_borders, BORDER_SE)) {
+			/* Bottom right */
+			max_y = abs((perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.85, 71) + 0.25) * 6 + (perlin_coast_noise_2D(x, _height_map.size_y / 3, 0.35, 193) + 0.75) * 12);
+			max_y = max((smallest_size * smallest_size / 16) + max_y, (smallest_size * smallest_size / 16) + margin - max_y);
+			if (smallest_size < 8 && max_y > 5) max_y /= 1.5;
+			for (y = _height_map.size_y; y > (_height_map.size_y - 1 - max_y); y--) {
+				_height_map.height(x, y) = 0;
+			}
 		}
 	}
 }
@@ -658,18 +672,18 @@ static void HeightMapSmoothCoastInDirection(int org_x, int org_y, int dir_x, int
 }
 
 /** Smooth coasts by modulating height of tiles close to map edges with cosine of distance from edge */
-static void HeightMapSmoothCoasts()
+static void HeightMapSmoothCoasts(uint8 water_borders)
 {
 	uint x, y;
 	/* First Smooth NW and SE coasts (y close to 0 and y close to size_y) */
 	for (x = 0; x < _height_map.size_x; x++) {
-		HeightMapSmoothCoastInDirection(x, 0, 0, 1);
-		HeightMapSmoothCoastInDirection(x, _height_map.size_y - 1, 0, -1);
+		if (HasBit(water_borders, BORDER_NW)) HeightMapSmoothCoastInDirection(x, 0, 0, 1);
+		if (HasBit(water_borders, BORDER_SE)) HeightMapSmoothCoastInDirection(x, _height_map.size_y - 1, 0, -1);
 	}
 	/* First Smooth NE and SW coasts (x close to 0 and x close to size_x) */
 	for (y = 0; y < _height_map.size_y; y++) {
-		HeightMapSmoothCoastInDirection(0, y, 1, 0);
-		HeightMapSmoothCoastInDirection(_height_map.size_x - 1, y, -1, 0);
+		if (HasBit(water_borders, BORDER_NE)) HeightMapSmoothCoastInDirection(0, y, 1, 0);
+		if (HasBit(water_borders, BORDER_SW)) HeightMapSmoothCoastInDirection(_height_map.size_x - 1, y, -1, 0);
 	}
 }
 
@@ -683,15 +697,15 @@ static void HeightMapSmoothCoasts()
 static void HeightMapSmoothSlopes(height_t dh_max)
 {
 	int x, y;
-	for (y = 1; y <= (int)_height_map.size_y; y++) {
-		for (x = 1; x <= (int)_height_map.size_x; x++) {
-			height_t h_max = min(_height_map.height(x - 1, y), _height_map.height(x, y - 1)) + dh_max;
+	for (y = 0; y <= (int)_height_map.size_y; y++) {
+		for (x = 0; x <= (int)_height_map.size_x; x++) {
+			height_t h_max = min(_height_map.height(x > 0 ? x - 1 : x, y), _height_map.height(x, y > 0 ? y - 1 : y)) + dh_max;
 			if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 		}
 	}
-	for (y = _height_map.size_y - 1; y >= 0; y--) {
-		for (x = _height_map.size_x - 1; x >= 0; x--) {
-			height_t h_max = min(_height_map.height(x + 1, y), _height_map.height(x, y + 1)) + dh_max;
+	for (y = _height_map.size_y; y >= 0; y--) {
+		for (x = _height_map.size_x; x >= 0; x--) {
+			height_t h_max = min(_height_map.height((uint)x < _height_map.size_x ? x + 1 : x, y), _height_map.height(x, (uint)y < _height_map.size_y ? y + 1 : y)) + dh_max;
 			if (_height_map.height(x, y) > h_max) _height_map.height(x, y) = h_max;
 		}
 	}
@@ -710,10 +724,12 @@ static void HeightMapNormalize()
 
 	HeightMapAdjustWaterLevel(water_percent, h_max_new);
 
-	HeightMapCoastLines();
+	byte water_borders = _settings_game.construction.freeform_edges ? _settings_game.game_creation.water_borders : 0xF;
+
+	HeightMapCoastLines(water_borders);
 	HeightMapSmoothSlopes(roughness);
 
-	HeightMapSmoothCoasts();
+	HeightMapSmoothCoasts(water_borders);
 	HeightMapSmoothSlopes(roughness);
 
 	HeightMapSineTransform(12, h_max_new);
@@ -817,7 +833,12 @@ static double perlin_coast_noise_2D(const double x, const double y, const double
 static void TgenSetTileHeight(TileIndex tile, int height)
 {
 	SetTileHeight(tile, height);
-	MakeClear(tile, CLEAR_GRASS, 3);
+
+	/* Only clear the tiles within the map area. */
+	if (TileX(tile) != MapMaxX() && TileY(tile) != MapMaxY() &&
+			(!_settings_game.construction.freeform_edges || (TileX(tile) != 0 && TileY(tile) != 0))) {
+		MakeClear(tile, CLEAR_GRASS, 3);
+	}
 }
 
 /**
@@ -842,9 +863,15 @@ void GenerateTerrainPerlin()
 
 	IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 
+	/* First make sure the tiles at the north border are void tiles if needed. */
+	if (_settings_game.construction.freeform_edges) {
+		for (y = 0; y < _height_map.size_y - 1; y++) MakeVoid(_height_map.size_x * y);
+		for (x = 0; x < _height_map.size_x;     x++) MakeVoid(x);
+	}
+
 	/* Transfer height map into OTTD map */
-	for (y = 2; y < _height_map.size_y - 2; y++) {
-		for (x = 2; x < _height_map.size_x - 2; x++) {
+	for (y = 0; y < _height_map.size_y; y++) {
+		for (x = 0; x < _height_map.size_x; x++) {
 			int height = H2I(_height_map.height(x, y));
 			if (height < 0) height = 0;
 			if (height > 15) height = 15;
@@ -854,10 +881,6 @@ void GenerateTerrainPerlin()
 
 	IncreaseGeneratingWorldProgress(GWP_LANDSCAPE);
 
-	/* Recreate void tiles at the border in case they have been affected by generation */
-	for (y = 0; y < _height_map.size_y - 1; y++) MakeVoid(_height_map.size_x * y + _height_map.size_x - 1);
-	for (x = 0; x < _height_map.size_x;     x++) MakeVoid(_height_map.size_x * y + x);
-
 	FreeHeightMap();
 	GenerateWorldSetAbortCallback(NULL);
 }
diff --git a/src/tile_map.cpp b/src/tile_map.cpp
index 4f6ea17d6..c8977d6d1 100644
--- a/src/tile_map.cpp
+++ b/src/tile_map.cpp
@@ -16,8 +16,9 @@ Slope GetTileSlope(TileIndex tile, uint *h)
 {
 	assert(tile < MapSize());
 
-	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) {
-		if (h != NULL) *h = 0;
+	if (TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY() ||
+			(_settings_game.construction.freeform_edges && (TileX(tile) == 0 || TileY(tile) == 0))) {
+		if (h != NULL) *h = TileHeight(tile) * TILE_HEIGHT;
 		return SLOPE_FLAT;
 	}
 
diff --git a/src/tile_map.h b/src/tile_map.h
index f9ce5ddc9..bd67279a6 100644
--- a/src/tile_map.h
+++ b/src/tile_map.h
@@ -10,6 +10,7 @@
 #include "company_type.h"
 #include "map_func.h"
 #include "core/bitmath_func.hpp"
+#include "settings_type.h"
 
 /**
  * Returns the height of a tile
@@ -87,8 +88,9 @@ static inline void SetTileType(TileIndex tile, TileType type)
 {
 	assert(tile < MapSize());
 	/* VOID tiles (and no others) are exactly allowed at the lower left and right
-	 * edges of the map */
-	assert((TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY()) == (type == MP_VOID));
+	 * edges of the map. If _settings_game.construction.freeform_edges is true,
+	 * the upper edges of the map are also VOID tiles. */
+	assert((TileX(tile) == MapMaxX() || TileY(tile) == MapMaxY() || (_settings_game.construction.freeform_edges && (TileX(tile) == 0 || TileY(tile) == 0))) == (type == MP_VOID));
 	SB(_m[tile].type_height, 4, 4, type);
 }
 
diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 9ef890a91..7be47fa6a 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -759,7 +759,7 @@ static bool IsNeighborRoadTile(TileIndex tile, const DiagDirection dir, uint dis
 		if (pos & 2) cur += tid_lt[2];
 
 		cur = (uint)(pos / 4) * cur; // Multiply for the fitting distance
-		if (GetTownRoadBits(TILE_ADD(tile, cur)) & DiagDirToRoadBits((pos & 2) ? dir : ReverseDiagDir(dir))) return true;
+		if (IsValidTile(tile + TileXY(TileX(cur) / 2, TileY(cur) / 2)) && IsValidTile(tile + cur) && GetTownRoadBits(TILE_ADD(tile, cur)) & DiagDirToRoadBits((pos & 2) ? dir : ReverseDiagDir(dir))) return true;
 	}
 	return false;
 }
@@ -1135,6 +1135,8 @@ static void GrowTownInTile(TileIndex *tile_ptr, RoadBits cur_rb, DiagDirection t
 		/* Don't walk into water. */
 		if (IsWaterTile(house_tile)) return;
 
+		if (!IsValidTile(house_tile) || !IsValidTile(house_tile + TileOffsByDiagDir(target_dir))) return;
+
 		switch (t1->GetActiveLayout()) {
 			default: NOT_REACHED();
 
diff --git a/src/tunnel_map.cpp b/src/tunnel_map.cpp
index 648f233a8..8400c9483 100644
--- a/src/tunnel_map.cpp
+++ b/src/tunnel_map.cpp
@@ -47,6 +47,7 @@ bool IsTunnelInWayDir(TileIndex tile, uint z, DiagDirection dir)
 
 	do {
 		tile -= delta;
+		if (!IsValidTile(tile)) return false;
 		height = GetTileZ(tile);
 	} while (z < height);
 
diff --git a/src/tunnelbridge_cmd.cpp b/src/tunnelbridge_cmd.cpp
index 7d33f62f7..27667219f 100644
--- a/src/tunnelbridge_cmd.cpp
+++ b/src/tunnelbridge_cmd.cpp
@@ -527,6 +527,7 @@ CommandCost CmdBuildTunnel(TileIndex start_tile, uint32 flags, uint32 p1, uint32
 
 	for (;;) {
 		end_tile += delta;
+		if (!IsValidTile(end_tile)) return_cmd_error(STR_TUNNEL_THROUGH_MAP_BORDER);
 		end_tileh = GetTileSlope(end_tile, &end_z);
 
 		if (start_z == end_z) break;
diff --git a/src/unmovable_cmd.cpp b/src/unmovable_cmd.cpp
index 71e514c2f..f6eb3ea70 100644
--- a/src/unmovable_cmd.cpp
+++ b/src/unmovable_cmd.cpp
@@ -367,11 +367,13 @@ static bool ClickTile_Unmovable(TileIndex tile)
 /* checks, if a radio tower is within a 9x9 tile square around tile */
 static bool IsRadioTowerNearby(TileIndex tile)
 {
-	TileIndex tile_s = tile - TileDiffXY(4, 4);
+	TileIndex tile_s = tile - TileDiffXY(min(TileX(tile), 4U), min(TileY(tile), 4U));
+	uint w = min(TileX(tile), 4U) + 1 + min(MapMaxX() - TileX(tile), 4U);
+	uint h = min(TileY(tile), 4U) + 1 + min(MapMaxY() - TileY(tile), 4U);
 
-	BEGIN_TILE_LOOP(tile, 9, 9, tile_s)
+	BEGIN_TILE_LOOP(tile, w, h, tile_s)
 		if (IsTransmitterTile(tile)) return true;
-	END_TILE_LOOP(tile, 9, 9, tile_s)
+	END_TILE_LOOP(tile, w, h, tile_s)
 
 	return false;
 }
@@ -383,6 +385,23 @@ void GenerateUnmovables()
 	/* add radio tower */
 	int radiotowser_to_build = ScaleByMapSize(15); // maximum number of radio towers on the map
 	int lighthouses_to_build = _settings_game.game_creation.landscape == LT_TROPIC ? 0 : ScaleByMapSize1D((Random() & 3) + 7);
+
+	/* Scale the amount of lighthouses with the amount of land at the borders. */
+	if (_settings_game.construction.freeform_edges) {
+		uint num_water_tiles = 0;
+		for (uint x = 0; x < MapMaxX(); x++) {
+			if (IsTileType(TileXY(x, 1), MP_WATER)) num_water_tiles++;
+			if (IsTileType(TileXY(x, MapMaxY() - 1), MP_WATER)) num_water_tiles++;
+		}
+		for (uint y = 1; y < MapMaxY() - 1; y++) {
+			if (IsTileType(TileXY(1, y), MP_WATER)) num_water_tiles++;
+			if (IsTileType(TileXY(MapMaxX() - 1, y), MP_WATER)) num_water_tiles++;
+		}
+		/* The -6 is because the top borders are MP_VOID (-2) and all corners
+		 * are counted twice (-4). */
+		lighthouses_to_build = lighthouses_to_build * num_water_tiles / (2 * MapMaxY() + 2 * MapMaxX() - 6);
+	}
+
 	SetGeneratingWorldProgress(GWP_UNMOVABLE, radiotowser_to_build + lighthouses_to_build);
 
 	for (uint i = ScaleByMapSize(1000); i != 0; i--) {
@@ -416,13 +435,16 @@ void GenerateUnmovables()
 		TileIndex tile;
 		switch (dir) {
 			default:
-			case DIAGDIR_NE: tile = TileXY(maxx,     r % maxy); break;
-			case DIAGDIR_SE: tile = TileXY(r % maxx, 0);        break;
-			case DIAGDIR_SW: tile = TileXY(0,        r % maxy); break;
-			case DIAGDIR_NW: tile = TileXY(r % maxx, maxy);     break;
+			case DIAGDIR_NE: tile = TileXY(maxx - 1, r % maxy); break;
+			case DIAGDIR_SE: tile = TileXY(r % maxx, 1); break;
+			case DIAGDIR_SW: tile = TileXY(1,        r % maxy); break;
+			case DIAGDIR_NW: tile = TileXY(r % maxx, maxy - 1); break;
 		}
 
-		for (int j = 0; j < 20; j++) {
+		/* Only build lighthouses at tiles where the border is sea. */
+		if (!IsTileType(tile, MP_WATER)) continue;
+
+		for (int j = 0; j < 19; j++) {
 			uint h;
 			if (IsTileType(tile, MP_CLEAR) && GetTileSlope(tile, &h) == SLOPE_FLAT && h <= TILE_HEIGHT * 2 && !IsBridgeAbove(tile)) {
 				MakeLighthouse(tile);
diff --git a/src/viewport.cpp b/src/viewport.cpp
index d507772b4..2227c8ca1 100644
--- a/src/viewport.cpp
+++ b/src/viewport.cpp
@@ -382,8 +382,8 @@ static Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y)
 	/* we need to move variables in to the valid range, as the
 	 * GetTileZoomCenterWindow() function can call here with invalid x and/or y,
 	 * when the user tries to zoom out along the sides of the map */
-	a = Clamp(a, 0, (int)(MapMaxX() * TILE_SIZE) - 1);
-	b = Clamp(b, 0, (int)(MapMaxY() * TILE_SIZE) - 1);
+	a = Clamp(a, -4 * TILE_SIZE, (int)(MapMaxX() * TILE_SIZE) - 1);
+	b = Clamp(b, -4 * TILE_SIZE, (int)(MapMaxY() * TILE_SIZE) - 1);
 
 	/* (a, b) is the X/Y-world coordinate that belongs to (x,y) if the landscape would be completely flat on height 0.
 	 * Now find the Z-world coordinate by fix point iteration.
@@ -393,12 +393,15 @@ static Point TranslateXYToTileCoord(const ViewPort *vp, int x, int y)
 	 * So give it a z-malus of 4 in the first iterations.
 	 */
 	z = 0;
-	for (int i = 0; i < 5; i++) z = GetSlopeZ(a + max(z, 4u) - 4, b + max(z, 4u) - 4) / 2;
-	for (uint malus = 3; malus > 0; malus--) z = GetSlopeZ(a + max(z, malus) - malus, b + max(z, malus) - malus) / 2;
-	for (int i = 0; i < 5; i++) z = GetSlopeZ(a + z, b + z) / 2;
 
-	pt.x = a + z;
-	pt.y = b + z;
+	int min_coord = _settings_game.construction.freeform_edges ? TILE_SIZE : 0;
+
+	for (int i = 0; i < 5; i++) z = GetSlopeZ(Clamp(a + (int)max(z, 4u) - 4, min_coord, MapMaxX() * TILE_SIZE - 1), Clamp(b + (int)max(z, 4u) - 4, min_coord, MapMaxY() * TILE_SIZE - 1)) / 2;
+	for (uint malus = 3; malus > 0; malus--) z = GetSlopeZ(Clamp(a + (int)max(z, malus) - (int)malus, min_coord, MapMaxX() * TILE_SIZE - 1), Clamp(b + (int)max(z, malus) - (int)malus, min_coord, MapMaxY() * TILE_SIZE - 1)) / 2;
+	for (int i = 0; i < 5; i++) z = GetSlopeZ(Clamp(a + (int)z, min_coord, MapMaxX() * TILE_SIZE - 1), Clamp(b + (int)z, min_coord, MapMaxY() * TILE_SIZE - 1)) / 2;
+
+	pt.x = Clamp(a + (int)z, min_coord, MapMaxX() * TILE_SIZE - 1);
+	pt.y = Clamp(b + (int)z, min_coord, MapMaxY() * TILE_SIZE - 1);
 
 	return pt;
 }
@@ -969,26 +972,33 @@ static void ViewportAddLandscape()
 		int y_cur = y;
 
 		do {
-			TileType tt;
+			TileType tt = MP_VOID;
 
 			ti.x = x_cur;
 			ti.y = y_cur;
-			if (0 <= x_cur && x_cur < (int)MapSizeX() * TILE_SIZE &&
-					0 <= y_cur && y_cur < (int)MapSizeY() * TILE_SIZE) {
+
+			ti.z = 0;
+
+			ti.tileh = SLOPE_FLAT;
+			ti.tile = INVALID_TILE;
+
+			if (0 <= x_cur && x_cur < (int)MapMaxX() * TILE_SIZE &&
+					0 <= y_cur && y_cur < (int)MapMaxY() * TILE_SIZE) {
 				TileIndex tile = TileVirtXY(x_cur, y_cur);
 
-				ti.tile = tile;
-				ti.tileh = GetTileSlope(tile, &ti.z);
-				tt = GetTileType(tile);
-			} else {
-				ti.tileh = SLOPE_FLAT;
-				ti.tile = INVALID_TILE;
-				ti.z = 0;
-				tt = MP_VOID;
-			}
+				if (!_settings_game.construction.freeform_edges || (TileX(tile) != 0 && TileY(tile) != 0)) {
+					if (x_cur == ((int)MapMaxX() - 1) * TILE_SIZE || y_cur == ((int)MapMaxY() - 1) * TILE_SIZE) {
+						uint maxh = max<uint>(TileHeight(tile), 1);
+						for (uint h = 0; h < maxh; h++) {
+							DrawGroundSpriteAt(SPR_SHADOW_CELL, PAL_NONE, ti.x, ti.y, h * TILE_HEIGHT);
+						}
+					}
 
-			y_cur += 0x10;
-			x_cur -= 0x10;
+					ti.tile = tile;
+					ti.tileh = GetTileSlope(tile, &ti.z);
+					tt = GetTileType(tile);
+				}
+			}
 
 			_vd.foundation_part = FOUNDATION_PART_NONE;
 			_vd.foundation[0] = -1;
@@ -997,7 +1007,18 @@ static void ViewportAddLandscape()
 			_vd.last_foundation_child[1] = NULL;
 
 			_tile_type_procs[tt]->draw_tile_proc(&ti);
+
+			if ((x_cur == (int)MapMaxX() * TILE_SIZE && IsInsideMM(y_cur, 0, MapMaxY() * TILE_SIZE)) ||
+				(y_cur == (int)MapMaxY() * TILE_SIZE && IsInsideMM(x_cur, 0, MapMaxX() * TILE_SIZE))) {
+				TileIndex tile = TileVirtXY(x_cur, y_cur);
+				ti.tile = tile;
+				ti.tileh = GetTileSlope(tile, &ti.z);
+				tt = GetTileType(tile);
+			}
 			if (ti.tile != INVALID_TILE) DrawTileSelection(&ti);
+
+			y_cur += 0x10;
+			x_cur -= 0x10;
 		} while (--width_cur);
 
 		if ((direction ^= 1) != 0) {
diff --git a/src/water.h b/src/water.h
index 2fa063b3c..5c562e6fa 100644
--- a/src/water.h
+++ b/src/water.h
@@ -7,6 +7,7 @@
 
 void TileLoop_Water(TileIndex tile);
 bool FloodHalftile(TileIndex t);
+void DoFloodTile(TileIndex target);
 
 void ConvertGroundTilesIntoWaterTiles();
 
diff --git a/src/water_cmd.cpp b/src/water_cmd.cpp
index 6735d2231..c24e8d500 100644
--- a/src/water_cmd.cpp
+++ b/src/water_cmd.cpp
@@ -358,9 +358,9 @@ static CommandCost ClearTile_Water(TileIndex tile, byte flags)
 		case WATER_TILE_CLEAR:
 			if (flags & DC_NO_WATER) return_cmd_error(STR_3807_CAN_T_BUILD_ON_WATER);
 
-			/* Make sure it's not an edge tile. */
-			if (!IsInsideMM(TileX(tile), 1, MapMaxX() - 1) ||
-					!IsInsideMM(TileY(tile), 1, MapMaxY() - 1)) {
+			/* Make sure freeform edges are allowed or it's not an edge tile. */
+			if (!_settings_game.construction.freeform_edges && (!IsInsideMM(TileX(tile), 1, MapMaxX() - 1) ||
+					!IsInsideMM(TileY(tile), 1, MapMaxY() - 1))) {
 				return_cmd_error(STR_0002_TOO_CLOSE_TO_EDGE_OF_MAP);
 			}
 
@@ -905,7 +905,7 @@ static FloodingBehaviour GetFloodingBehaviour(TileIndex tile)
 /**
  * Floods a tile.
  */
-static void DoFloodTile(TileIndex target)
+void DoFloodTile(TileIndex target)
 {
 	assert(!IsTileType(target, MP_WATER));