no_global.diff

diff --git a/src/landscape.cpp b/src/landscape.cpp
index 442bb61cda..c10c2191a6 100644
--- a/src/landscape.cpp
+++ b/src/landscape.cpp
@@ -89,11 +89,6 @@ extern const byte _slope_to_sprite_offset[32] = {
  */
 static SnowLine *_snow_line = nullptr;
 
-/** The current spring during river generation */
-static TileIndex _current_spring = INVALID_TILE;
-
-/** Whether the current river is a big river that others flow into */
-static bool _is_main_river = false;
 
 /**
  * Map 2D viewport or smallmap coordinate to 3D world or tile coordinate.
@@ -1115,6 +1110,12 @@ static bool FlowsDown(TileIndex begin, TileIndex end)
 			((slopeEnd == slopeBegin && heightEnd < heightBegin) || slopeEnd == SLOPE_FLAT || slopeBegin == SLOPE_FLAT);
 }
 
+/** Parameters for river generation to pass as AyStar user data. */
+struct River_UserData {
+	TileIndex spring; ///< The current spring during river generation.
+	bool main_river;  ///< Whether the current river is a big river that others flow into.
+};
+
 /* AyStar callback for checking whether we reached our destination. */
 static int32 River_EndNodeCheck(const AyStar *aystar, const OpenListNode *current)
 {
@@ -1152,6 +1153,8 @@ static void River_GetNeighbours(AyStar *aystar, OpenListNode *current)
 /* AyStar callback when an route has been found. */
 static void River_FoundEndNode(AyStar *aystar, OpenListNode *current)
 {
+	River_UserData *data = (River_UserData *)aystar->user_data;
+
 	/* Count river length. */
 	uint length = 0;
 	for (PathNode *path = &current->path; path != nullptr; path = path->parent) {
@@ -1165,14 +1168,14 @@ static void River_FoundEndNode(AyStar *aystar, OpenListNode *current)
 			MakeRiver(tile, Random());
 
 			/* Check if we should widen river depending on how far we are away from the source. */
-			const uint current_river_length = DistanceManhattan(_current_spring, path->node.tile);
+			const uint current_river_length = DistanceManhattan(data->spring, path->node.tile);
 			const uint long_river_length = _settings_game.game_creation.min_river_length * 4;
 			const uint radius = std::min(3u, (current_river_length / (long_river_length / 3u)) + 1u);
 
 			MarkTileDirtyByTile(tile);
 
 			/* If building a main river, try to widen it. */
-			if (_is_main_river && (radius > 1)) {
+			if (data->main_river && (radius > 1)) {
 				CircularTileSearch(&tile, radius + RandomRange(1), RiverMakeWider, (void*)&path->node.tile);
 			}
 			else {
@@ -1200,9 +1203,13 @@ static uint River_Hash(uint tile, uint dir)
  * Actually build the river between the begin and end tiles using AyStar.
  * @param begin The begin of the river.
  * @param end The end of the river.
+ * @param spring The springing point of the river.
+ * @param main_river Whether the current river is a big river that others flow into.
  */
-static void BuildRiver(TileIndex begin, TileIndex end)
+static void BuildRiver(TileIndex begin, TileIndex end, TileIndex spring, bool main_river)
 {
+	River_UserData user_data = { spring, main_river };
+
 	AyStar finder = {};
 	finder.CalculateG = River_CalculateG;
 	finder.CalculateH = River_CalculateH;
@@ -1210,6 +1217,7 @@ static void BuildRiver(TileIndex begin, TileIndex end)
 	finder.EndNodeCheck = River_EndNodeCheck;
 	finder.FoundEndNode = River_FoundEndNode;
 	finder.user_target = &end;
+	finder.user_data = &user_data;
 
 	finder.Init(River_Hash, 1 << RIVER_HASH_SIZE);
 
@@ -1226,20 +1234,16 @@ static void BuildRiver(TileIndex begin, TileIndex end)
  * @param spring The springing point of the river.
  * @param begin  The begin point we are looking from; somewhere down hill from the spring.
  * @param min_river_length The minimum length for the river.
- * @return True iff a river could/has been built, otherwise false.
+ * @return First element: True iff a river could/has been built, otherwise false; second element: River ends at sea.
  */
-static bool FlowRiver(TileIndex spring, TileIndex begin, uint min_river_length)
+static std::tuple<bool, bool> FlowRiver(TileIndex spring, TileIndex begin, uint min_river_length)
 {
 #	define SET_MARK(x) marks.insert(x)
 #	define IS_MARKED(x) (marks.find(x) != marks.end())
 
 	uint height = TileHeight(begin);
-	if (IsWaterTile(begin))
-	{
-		if (GetTileZ(begin) == 0) {
-			_is_main_river = true;
-		}
-		return DistanceManhattan(spring, begin) > min_river_length;
+	if (IsWaterTile(begin))	{
+		return { DistanceManhattan(spring, begin) > min_river_length, GetTileZ(begin) == 0 };
 	}
 
 	std::set<TileIndex> marks;
@@ -1272,9 +1276,10 @@ static bool FlowRiver(TileIndex spring, TileIndex begin, uint min_river_length)
 		}
 	} while (!queue.empty());
 
+	bool main_river = false;
 	if (found) {
 		/* Flow further down hill. */
-		found = FlowRiver(spring, end, min_river_length);
+		std::tie(found, main_river) = FlowRiver(spring, end, min_river_length);
 	} else if (count > 32) {
 		/* Maybe we can make a lake. Find the Nth of the considered tiles. */
 		TileIndex lakeCenter = 0;
@@ -1310,8 +1315,8 @@ static bool FlowRiver(TileIndex spring, TileIndex begin, uint min_river_length)
 	}
 
 	marks.clear();
-	if (found) BuildRiver(begin, end);
-	return found;
+	if (found) BuildRiver(begin, end, spring, main_river);
+	return { found, main_river };
 }
 
 /**
@@ -1332,9 +1337,7 @@ static void CreateRivers()
 		for (int tries = 0; tries < 512; tries++) {
 			TileIndex t = RandomTile();
 			if (!CircularTileSearch(&t, 8, FindSpring, nullptr)) continue;
-			_current_spring = t;
-			_is_main_river = false;
-			if (FlowRiver(t, t, _settings_game.game_creation.min_river_length * 4)) break;
+			if (std::get<0>(FlowRiver(t, t, _settings_game.game_creation.min_river_length * 4))) break;
 		}
 	}
 
@@ -1344,9 +1347,7 @@ static void CreateRivers()
 		for (int tries = 0; tries < 128; tries++) {
 			TileIndex t = RandomTile();
 			if (!CircularTileSearch(&t, 8, FindSpring, nullptr)) continue;
-			_current_spring = t;
-			_is_main_river = false;
-			if (FlowRiver(t, t, _settings_game.game_creation.min_river_length)) break;
+			if (std::get<0>(FlowRiver(t, t, _settings_game.game_creation.min_river_length))) break;
 		}
 	}