(svn r9371) -Feature: Add support for variable snow lines in the arctic climate, supplied

by newgrf files. When this is enabled forests cannot be built below the highest
snow line, and farms can't be built above it. Houses still use the
_opt.snow_line so they are all consistent, so to make them respect the snowline
you may want to use some newhouses features as well.

src/clear_cmd.cpp

@@ -16,6 +16,7 @@
 #include "tunnel_map.h"
 #include "bridge_map.h"
 #include "bridge.h"
+#include "landscape.h"
 #include "variables.h"
 #include "table/sprites.h"
 #include "unmovable_map.h"
@@ -620,7 +621,7 @@ void TileLoopClearHelper(TileIndex tile)
 /* convert into snowy tiles */
 static void TileLoopClearAlps(TileIndex tile)
 {
-	int k = GetTileZ(tile) - _opt.snow_line + TILE_HEIGHT;
+	int k = GetTileZ(tile) - GetSnowLine() + TILE_HEIGHT;
 
 	if (k < 0) { // well below the snow line
 		if (!IsClearGround(tile, CLEAR_SNOW)) return;

src/industry_cmd.cpp

@@ -12,6 +12,7 @@
 #include "table/sprites.h"
 #include "map.h"
 #include "tile.h"
+#include "landscape.h"
 #include "viewport.h"
 #include "command.h"
 #include "industry.h"
@@ -814,7 +815,7 @@ static void PlantFarmField(TileIndex tile, IndustryID industry)
 	int type;
 
 	if (_opt.landscape == LT_HILLY) {
-		if (GetTileZ(tile) + TILE_HEIGHT * 2 >= _opt.snow_line)
+		if (GetTileZ(tile) + TILE_HEIGHT * 2 >= GetSnowLine())
 			return;
 	}
 
@@ -1016,7 +1017,7 @@ static bool CheckNewIndustry_NULL(TileIndex tile)
 static bool CheckNewIndustry_Forest(TileIndex tile)
 {
 	if (_opt.landscape == LT_HILLY) {
-		if (GetTileZ(tile) < _opt.snow_line + TILE_HEIGHT * 2U) {
+		if (GetTileZ(tile) < HighestSnowLine() + TILE_HEIGHT * 2U) {
 			_error_message = STR_4831_FOREST_CAN_ONLY_BE_PLANTED;
 			return false;
 		}
@@ -1048,7 +1049,7 @@ static bool CheckNewIndustry_OilRig(TileIndex tile)
 static bool CheckNewIndustry_Farm(TileIndex tile)
 {
 	if (_opt.landscape == LT_HILLY) {
-		if (GetTileZ(tile) + TILE_HEIGHT * 2 >= _opt.snow_line) {
+		if (GetTileZ(tile) + TILE_HEIGHT * 2 >= HighestSnowLine()) {
 			_error_message = STR_0239_SITE_UNSUITABLE;
 			return false;
 		}

src/landscape.cpp

@@ -5,6 +5,7 @@
 #include "bridge_map.h"
 #include "heightmap.h"
 #include "clear_map.h"
+#include "date.h"
 #include "functions.h"
 #include "map.h"
 #include "player.h"
@@ -14,6 +15,7 @@
 #include <stdarg.h>
 #include "viewport.h"
 #include "command.h"
+#include "landscape.h"
 #include "vehicle.h"
 #include "variables.h"
 #include "void_map.h"
@@ -61,6 +63,7 @@ const Slope _inclined_tileh[] = {
 	SLOPE_NWS, SLOPE_WSE, SLOPE_SEN, SLOPE_ENW
 };
 
+SnowLine *_snow_line = NULL;
 
 uint GetPartialZ(int x, int y, Slope corners)
 {
@@ -302,6 +305,62 @@ void GetTileDesc(TileIndex tile, TileDesc *td)
 	_tile_type_procs[GetTileType(tile)]->get_tile_desc_proc(tile, td);
 }
 
+/**
+ * Has a snow line table already been loaded.
+ * @return true if the table has been loaded already.
+ */
+bool IsSnowLineSet(void)
+{
+	return _snow_line != NULL;
+}
+
+/**
+ * Set a variable snow line, as loaded from a newgrf file.
+ * @param table the 12 * 32 byte table containing the snowline for each day
+ */
+void SetSnowLine(byte table[SNOW_LINE_MONTHS][SNOW_LINE_DAYS])
+{
+	_snow_line = CallocT<SnowLine>(1);
+	memcpy(_snow_line->table, table, sizeof(_snow_line->table));
+
+	for (uint i = 0; i < SNOW_LINE_MONTHS; i++) {
+		for (uint j = 0; j < SNOW_LINE_DAYS; j++) {
+			_snow_line->highest_value = max(_snow_line->highest_value, table[i][j]);
+		}
+	}
+}
+
+/**
+ * Get the current snow line, either variable or static.
+ * @return the snow line height.
+ */
+byte GetSnowLine(void)
+{
+	if (_snow_line == NULL) return _opt.snow_line;
+
+	YearMonthDay ymd;
+	ConvertDateToYMD(_date, &ymd);
+	return _snow_line->table[ymd.month][ymd.day];
+}
+
+/**
+ * Get the highest possible snow line height, either variable or static.
+ * @return the highest snow line height.
+ */
+byte HighestSnowLine(void)
+{
+	return _snow_line == NULL ? _opt.snow_line : _snow_line->highest_value;
+}
+
+/**
+ * Clear the variable snow line table and free the memory.
+ */
+void ClearSnowLine(void)
+{
+	free(_snow_line);
+	_snow_line = NULL;
+}
+
 /** Clear a piece of landscape
  * @param tile tile to clear
  * @param flags of operation to conduct

src/landscape.h

@@ -0,0 +1,19 @@
+/* $Id$ */
+
+/** @file landscape.h */
+
+enum {
+	SNOW_LINE_MONTHS = 12,
+	SNOW_LINE_DAYS   = 32,
+};
+
+struct SnowLine {
+	byte table[SNOW_LINE_MONTHS][SNOW_LINE_DAYS];
+	byte highest_value;
+};
+
+bool IsSnowLineSet(void);
+void SetSnowLine(byte table[SNOW_LINE_MONTHS][SNOW_LINE_DAYS]);
+byte GetSnowLine(void);
+byte HighestSnowLine(void);
+void ClearSnowLine(void);

src/newgrf.cpp

@@ -27,6 +27,7 @@
 #include "fontcache.h"
 #include "date.h"
 #include "currency.h"
+#include "landscape.h"
 #include "sound.h"
 #include "newgrf_config.h"
 #include "newgrf_house.h"
@@ -1510,6 +1511,22 @@ static bool GlobalVarChangeInfo(uint gvid, int numinfo, int prop, byte **bufp, i
 			break;
 
 		case 0x10: // 12 * 32 * B Snow line height table
+			if (numinfo > 1 || IsSnowLineSet()) {
+				grfmsg(1, "GlobalVarChangeInfo: The snowline can only be set once (%d)", numinfo);
+			} else if (len < SNOW_LINE_MONTHS * SNOW_LINE_DAYS) {
+				grfmsg(1, "GlobalVarChangeInfo: Not enough entries set in the snowline table (%d)", len);
+			} else {
+				byte table[SNOW_LINE_MONTHS][SNOW_LINE_DAYS];
+
+				for (uint i = 0; i < SNOW_LINE_MONTHS; i++) {
+					for (uint j = 0; j < SNOW_LINE_DAYS; j++) {
+						table[i][j] = grf_load_byte(&buf);
+					}
+				}
+				SetSnowLine(table);
+			}
+			break;
+
 		default:
 			ret = true;
 	}
@@ -3973,6 +3990,9 @@ static void ResetNewGRFData()
 	ResetStationClasses();
 	ResetCustomStations();
 
+	/* Reset the snowline table. */
+	ClearSnowLine();
+
 	/* Reset NewGRF files */
 	ResetNewGRF();
 

src/newgrf_house.cpp

@@ -8,6 +8,7 @@
 #include "variables.h"
 #include "debug.h"
 #include "viewport.h"
+#include "landscape.h"
 #include "date.h"
 #include "town.h"
 #include "town_map.h"
@@ -252,7 +253,7 @@ static uint32 GetTerrainType(TileIndex tile)
 {
 	switch (_opt.landscape) {
 		case LT_DESERT: return GetTropicZone(tile) == TROPICZONE_DESERT ? 1 : 2;
-		case LT_HILLY:  return GetTileZ(tile) >= _opt.snow_line ? 4 : 0;
+		case LT_HILLY:  return GetTileZ(tile) >= GetSnowLine() ? 4 : 0;
 		default:        return 0;
 	}
 }

src/newgrf_spritegroup.cpp

@@ -4,6 +4,7 @@
 #include "openttd.h"
 #include "variables.h"
 #include "macros.h"
+#include "landscape.h"
 #include "oldpool.h"
 #include "newgrf_callbacks.h"
 #include "newgrf_spritegroup.h"
@@ -91,7 +92,7 @@ static inline uint32 GetVariable(const ResolverObject *object, byte variable, by
 		case 0x1A: return UINT_MAX;
 		case 0x1B: return GB(_display_opt, 0, 6);
 		case 0x1C: return object->last_value;
-		case 0x20: return _opt.landscape == LT_HILLY ? _opt.snow_line : 0xFF;
+		case 0x20: return _opt.landscape == LT_HILLY ? GetSnowLine() : 0xFF;
 
 		/* Not a common variable, so evalute the feature specific variables */
 		default: return object->GetVariable(object, variable, parameter, available);

src/newgrf_station.cpp

@@ -6,6 +6,7 @@
 #include "openttd.h"
 #include "variables.h"
 #include "functions.h"
+#include "landscape.h"
 #include "debug.h"
 #include "sprite.h"
 #include "table/sprites.h"
@@ -370,7 +371,7 @@ static uint32 StationGetVariable(const ResolverObject *object, byte variable, by
 		case 0x40: return GetPlatformInfoHelper(tile, false, false, false);
 		case 0x41: return GetPlatformInfoHelper(tile, true,  false, false);
 		case 0x42: /* Terrain and rail type */
-			return ((_opt.landscape == LT_HILLY && GetTileZ(tile) > _opt.snow_line) ? 4 : 0) |
+			return ((_opt.landscape == LT_HILLY && GetTileZ(tile) > GetSnowLine()) ? 4 : 0) |
 			       (_opt.landscape == LT_DESERT ? GetTropicZone(tile) : 0) |
 			       (GetRailType(tile) << 8);
 		case 0x43: return st->owner; /* Station owner */

src/rail_cmd.cpp

@@ -12,6 +12,7 @@
 #include "table/sprites.h"
 #include "table/strings.h"
 #include "map.h"
+#include "landscape.h"
 #include "tile.h"
 #include "town_map.h"
 #include "tunnel_map.h"
@@ -1738,7 +1739,7 @@ static void TileLoop_Track(TileIndex tile)
 
 	switch (_opt.landscape) {
 		case LT_HILLY:
-			if (GetTileZ(tile) > _opt.snow_line) {
+			if (GetTileZ(tile) > GetSnowLine()) {
 				new_ground = RAIL_GROUND_ICE_DESERT;
 				goto set_ground;
 			}

src/road_cmd.cpp

@@ -12,6 +12,7 @@
 #include "table/strings.h"
 #include "functions.h"
 #include "map.h"
+#include "landscape.h"
 #include "tile.h"
 #include "town_map.h"
 #include "vehicle.h"
@@ -864,7 +865,7 @@ static void TileLoop_Road(TileIndex tile)
 {
 	switch (_opt.landscape) {
 		case LT_HILLY:
-			if (IsOnSnow(tile) != (GetTileZ(tile) > _opt.snow_line)) {
+			if (IsOnSnow(tile) != (GetTileZ(tile) > GetSnowLine())) {
 				ToggleSnow(tile);
 				MarkTileDirtyByTile(tile);
 			}

src/town_cmd.cpp

@@ -11,6 +11,7 @@
 #include "table/strings.h"
 #include "table/sprites.h"
 #include "map.h"
+#include "landscape.h"
 #include "tile.h"
 #include "town_map.h"
 #include "tunnel_map.h"
@@ -1700,7 +1701,7 @@ static void UpdateTownGrowRate(Town *t)
 	}
 
 	if (_opt.landscape == LT_HILLY) {
-		if (TilePixelHeight(t->xy) >= _opt.snow_line && t->act_food == 0 && t->population > 90)
+		if (TilePixelHeight(t->xy) >= GetSnowLine() && t->act_food == 0 && t->population > 90)
 			return;
 	} else if (_opt.landscape == LT_DESERT) {
 		if (GetTropicZone(t->xy) == TROPICZONE_DESERT && (t->act_food==0 || t->act_water==0) && t->population > 60)

src/tree_cmd.cpp

@@ -9,6 +9,7 @@
 #include "table/tree_land.h"
 #include "functions.h"
 #include "map.h"
+#include "landscape.h"
 #include "tile.h"
 #include "tree_map.h"
 #include "viewport.h"
@@ -53,7 +54,7 @@ static void PlaceTree(TileIndex tile, uint32 r)
 		MakeTree(tile, tree, GB(r, 22, 2), min(GB(r, 16, 3), 6), TREE_GROUND_GRASS, 0);
 
 		// above snowline?
-		if (_opt.landscape == LT_HILLY && GetTileZ(tile) > _opt.snow_line) {
+		if (_opt.landscape == LT_HILLY && GetTileZ(tile) > GetSnowLine()) {
 			SetTreeGroundDensity(tile, TREE_GROUND_SNOW_DESERT, 3);
 			SetTreeCounter(tile, (TreeGround)GB(r, 24, 3));
 		} else {
@@ -150,7 +151,7 @@ void PlaceTreesRandomly()
 			j = GetTileZ(tile) / TILE_HEIGHT * 2;
 			while (j--) {
 				/* Above snowline more trees! */
-				if (_opt.landscape == LT_HILLY && ht > _opt.snow_line) {
+				if (_opt.landscape == LT_HILLY && ht > GetSnowLine()) {
 					PlaceTreeAtSameHeight(tile, ht);
 					PlaceTreeAtSameHeight(tile, ht);
 				};
@@ -496,7 +497,7 @@ static void TileLoopTreesDesert(TileIndex tile)
 
 static void TileLoopTreesAlps(TileIndex tile)
 {
-	int k = GetTileZ(tile) - _opt.snow_line + TILE_HEIGHT;
+	int k = GetTileZ(tile) - GetSnowLine() + TILE_HEIGHT;
 
 	if (k < 0) {
 		if (GetTreeGround(tile) != TREE_GROUND_SNOW_DESERT) return;

src/tunnelbridge_cmd.cpp

@@ -14,6 +14,7 @@
 #include "table/strings.h"
 #include "functions.h"
 #include "map.h"
+#include "landscape.h"
 #include "tile.h"
 #include "tunnel_map.h"
 #include "unmovable_map.h"
@@ -1178,7 +1179,7 @@ static void TileLoop_TunnelBridge(TileIndex tile)
 	bool snow_or_desert = IsTunnelTile(tile) ? HasTunnelSnowOrDesert(tile) : HasBridgeSnowOrDesert(tile);
 	switch (_opt.landscape) {
 		case LT_HILLY:
-			if (snow_or_desert != (GetTileZ(tile) > _opt.snow_line)) {
+			if (snow_or_desert != (GetTileZ(tile) > GetSnowLine())) {
 				if (IsTunnelTile(tile)) {
 					SetTunnelSnowOrDesert(tile, !snow_or_desert);
 				} else {