Import Everest treeline patch

src/settings_type.h

@@ -310,6 +310,8 @@ struct ConstructionSettings {
 	uint8  industry_platform;                ///< the amount of flat land around an industry
 	bool   freeform_edges;                   ///< allow terraforming the tiles at the map edges
 	uint8  extra_tree_placement;             ///< (dis)allow building extra trees in-game
+	uint8  trees_around_snow_line_range;     ///< range around snowline for mixed and arctic forest.
+	uint32 no_trees_on_this_level;           ///< option to avoid growth of trees on certain tile level.
 	uint8  command_pause_level;              ///< level/amount of commands that can't be executed while paused
 
 	uint32 terraform_per_64k_frames;         ///< how many tile heights may, over a long period, be terraformed per 65536 frames?

src/table/settings.ini

@@ -2308,6 +2308,24 @@ strhelp  = STR_CONFIG_SETTING_EXTRA_TREE_PLACEMENT_HELPTEXT
 strval   = STR_CONFIG_SETTING_EXTRA_TREE_PLACEMENT_NONE
 cat      = SC_BASIC
 
+[SDT_VAR]
+base     = GameSettings
+var      = construction.trees_around_snow_line_range
+type     = SLE_UINT8
+def      = 0
+min      = 0
+max      = 15
+cat      = SC_BASIC
+
+[SDT_VAR]
+base     = GameSettings
+var      = construction.no_trees_on_this_level
+type     = SLE_UINT32
+def      = 0
+min      = 0
+max      = UINT32_MAX
+cat      = SC_BASIC
+
 [SDT_VAR]
 base     = GameSettings
 var      = game_creation.custom_sea_level

src/tree_cmd.cpp

@@ -131,13 +131,34 @@ static void PlantTreesOnTile(TileIndex tile, TreeType treetype, uint count, uint
  */
 static TreeType GetRandomTreeType(TileIndex tile, uint seed)
 {
+	/* no_trees_on_this_level example: 0xDC96521 is no trees on z levels 13,12,9,6,5,2,1. Set to 0 gives you original gameplay. (See openttd.cfg) */
+	uint32 no_tree = _settings_game.construction.no_trees_on_this_level;
+	byte   range   = _settings_game.construction.trees_around_snow_line_range;
+
 	switch (_settings_game.game_creation.landscape) {
 		case LT_TEMPERATE:
-			return (TreeType)(seed * TREE_COUNT_TEMPERATE / 256 + TREE_TEMPERATE);
+			if (no_tree == 0) return (TreeType)(seed * TREE_COUNT_TEMPERATE / 256 + TREE_TEMPERATE);
+		case LT_ARCTIC: {
+			if (no_tree == 0) return (TreeType)(seed * TREE_COUNT_SUB_ARCTIC / 256 + TREE_SUB_ARCTIC);
 
-		case LT_ARCTIC:
-			return (TreeType)(seed * TREE_COUNT_SUB_ARCTIC / 256 + TREE_SUB_ARCTIC);
+			int z = GetTileZ(tile);
+			if (z > _settings_game.game_creation.snow_line_height + (2 * range)) return TREE_INVALID; // Above tree line.
 
+			/* no_trees_on_this_level */
+			for (; no_tree != 0;) {
+				if ((int)(no_tree & 0xF) == z) return TREE_INVALID;
+				no_tree = no_tree >> 4;
+			}
+			if (z > (int)_settings_game.game_creation.snow_line_height - range) {
+				/* Below snow level mixed forest. Above is Arctic trees and thinning out. */
+				if (z < _settings_game.game_creation.snow_line_height) {
+					return (seed & 1) ? (TreeType)(seed * TREE_COUNT_SUB_ARCTIC / 256 + TREE_SUB_ARCTIC) : (TreeType)(seed * TREE_COUNT_TEMPERATE / 256 + TREE_TEMPERATE);
+				} else {
+					return (seed & 1) ? TREE_INVALID : (TreeType)(seed * TREE_COUNT_SUB_ARCTIC / 256 + TREE_SUB_ARCTIC);
+				}
+			}
+			return (TreeType)(seed * TREE_COUNT_TEMPERATE / 256 + TREE_TEMPERATE);
+		}
 		case LT_TROPIC:
 			switch (GetTropicZone(tile)) {
 				case TROPICZONE_NORMAL:  return (TreeType)(seed * TREE_COUNT_SUB_TROPICAL / 256 + TREE_SUB_TROPICAL);