Codechange: Where the ship comes from is already known

This simplifies the handling of variables.

`ChooseShipTrack` is called upon entering `tile`, and looking further back to the caller, it can be deduced that `v->tile` matches `src_tile`. With that said, `enterdir` can also be removed, as it's not used anywhere else.

`CreateRandomPath` and `GetRandomFollowUpTrackdir` is being fed `src_tile` as it's 2nd parameter. This could be eliminated, as `v` is also being passed to it. Just use `v->tile` in those functions.

src/pathfinder/yapf/yapf.h

@@ -21,11 +21,10 @@
  * Finds the best path for given ship using YAPF.
  * @param v        the ship that needs to find a path
  * @param tile     the tile to find the path from (should be next tile the ship is about to enter)
- * @param enterdir diagonal direction which the ship will enter this new tile from
  * @param path_found [out] Whether a path has been found (true) or has been guessed (false)
  * @return         the best trackdir for next turn or INVALID_TRACK if the path could not be found
  */
-Track YapfShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, bool &path_found, ShipPathCache &path_cache);
+Track YapfShipChooseTrack(const Ship *v, TileIndex tile, bool &path_found, ShipPathCache &path_cache);
 
 /**
  * Returns true if it is better to reverse the ship before leaving depot using YAPF.

src/pathfinder/yapf/yapf_ship.cpp

@@ -188,9 +188,9 @@ public:
 	}
 
 	/** Creates a random path, avoids 90 degree turns. */
-	static Trackdir CreateRandomPath(const Ship *v, TileIndex tile, Trackdir dir, ShipPathCache &path_cache, int path_length)
+	static Trackdir CreateRandomPath(const Ship *v, Trackdir dir, ShipPathCache &path_cache, int path_length)
 	{
-		std::pair<TileIndex, Trackdir> tile_dir = { tile, dir };
+		std::pair<TileIndex, Trackdir> tile_dir = { v->tile, dir };
 		for (int i = 0; i < path_length; ++i) {
 			tile_dir = GetRandomFollowUpTileTrackdir(v, tile_dir.first, tile_dir.second);
 			if (tile_dir.second == INVALID_TRACKDIR) break;
@@ -204,10 +204,8 @@ public:
 		return result;
 	}
 
-	static Trackdir ChooseShipTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, bool &path_found, ShipPathCache &path_cache)
+	static Trackdir ChooseShipTrack(const Ship *v, TileIndex tile, bool &path_found, ShipPathCache &path_cache)
 	{
-		/* Move back to the old tile/trackdir (where ship is coming from). */
-		const TileIndex src_tile = TileAddByDiagDir(tile, ReverseDiagDir(enterdir));
 		const Trackdir trackdir = v->GetVehicleTrackdir();
 		assert(IsValidTrackdir(trackdir));
 
@@ -218,7 +216,7 @@ public:
 		if (high_level_path.empty()) {
 			path_found = false;
 			/* Make the ship move around aimlessly. This prevents repeated pathfinder calls and clearly indicates that the ship is lost. */
-			return CreateRandomPath(v, src_tile, trackdir, path_cache, SHIP_LOST_PATH_LENGTH);
+			return CreateRandomPath(v, trackdir, path_cache, SHIP_LOST_PATH_LENGTH);
 		}
 
 		/* Try one time without restricting the search area, which generally results in better and more natural looking paths.
@@ -228,7 +226,7 @@ public:
 			Tpf pf(MAX_SHIP_PF_NODES);
 
 			/* Set origin and destination nodes */
-			pf.SetOrigin(src_tile, trackdirs);
+			pf.SetOrigin(v->tile, trackdirs);
 			pf.SetDestination(v);
 			const bool is_intermediate_destination = static_cast<int>(high_level_path.size()) >= NUMBER_OR_WATER_REGIONS_LOOKAHEAD + 1;
 			if (is_intermediate_destination) pf.SetIntermediateDestination(high_level_path.back());
@@ -241,7 +239,7 @@ public:
 			path_found = pf.FindPath(v);
 			Node *node = pf.GetBestNode();
 			if (attempt == 0 && !path_found) continue; // Try again with restricted search area.
-			if (!path_found || node == nullptr) return GetRandomFollowUpTileTrackdir(v, src_tile, trackdir).second;
+			if (!path_found || node == nullptr) return GetRandomFollowUpTileTrackdir(v, v->tile, trackdir).second;
 
 			/* Return only the path within the current water region if an intermediate destination was returned. If not, cache the entire path
 			 * to the final destination tile. The low-level pathfinder might actually prefer a different docking tile in a nearby region. Without
@@ -267,7 +265,7 @@ public:
 
 			/* A empty path means we are already at the destination. The pathfinder shouldn't have been called at all.
 			 * Return a random reachable trackdir to hopefully nudge the ship out of this strange situation. */
-			if (path_cache.empty()) return GetRandomFollowUpTileTrackdir(v, src_tile, trackdir).second;
+			if (path_cache.empty()) return GetRandomFollowUpTileTrackdir(v, v->tile, trackdir).second;
 
 			/* Take out the last trackdir as the result. */
 			const Trackdir result = path_cache.front();
@@ -437,9 +435,9 @@ struct CYapfShip : CYapfT<CYapfShip_TypesT<CYapfShip, CFollowTrackWater, CShipNo
 };
 
 /** Ship controller helper - path finder invoker. */
-Track YapfShipChooseTrack(const Ship *v, TileIndex tile, DiagDirection enterdir, bool &path_found, ShipPathCache &path_cache)
+Track YapfShipChooseTrack(const Ship *v, TileIndex tile, bool &path_found, ShipPathCache &path_cache)
 {
-	Trackdir td_ret = CYapfShip::ChooseShipTrack(v, tile, enterdir, path_found, path_cache);
+	Trackdir td_ret = CYapfShip::ChooseShipTrack(v, tile, path_found, path_cache);
 	return (td_ret != INVALID_TRACKDIR) ? TrackdirToTrack(td_ret) : INVALID_TRACK;
 }
 

src/ship_cmd.cpp

@@ -501,14 +501,11 @@ static void ShipArrivesAt(const Vehicle *v, Station *st)
  *
  * @param v Ship to navigate
  * @param tile Tile, the ship is about to enter
- * @param enterdir Direction of entering
  * @param tracks Available track choices on \a tile
  * @return Track to choose, or INVALID_TRACK when to reverse.
  */
-static Track ChooseShipTrack(Ship *v, TileIndex tile, DiagDirection enterdir, TrackBits tracks)
+static Track ChooseShipTrack(Ship *v, TileIndex tile, TrackBits tracks)
 {
-	assert(IsValidDiagDirection(enterdir));
-
 	bool path_found = true;
 	Track track;
 
@@ -535,7 +532,7 @@ static Track ChooseShipTrack(Ship *v, TileIndex tile, DiagDirection enterdir, Tr
 
 		switch (_settings_game.pf.pathfinder_for_ships) {
 			case VPF_NPF: track = NPFShipChooseTrack(v, path_found); break;
-			case VPF_YAPF: track = YapfShipChooseTrack(v, tile, enterdir, path_found, v->path); break;
+			case VPF_YAPF: track = YapfShipChooseTrack(v, tile, path_found, v->path); break;
 			default: NOT_REACHED();
 		}
 	}
@@ -821,7 +818,7 @@ static void ShipController(Ship *v)
 				}
 
 				/* Choose a direction, and continue if we find one */
-				const Track track = ChooseShipTrack(v, gp.new_tile, diagdir, tracks);
+				const Track track = ChooseShipTrack(v, gp.new_tile, tracks);
 				if (track == INVALID_TRACK) return ReverseShip(v);
 
 				const ShipSubcoordData &b = _ship_subcoord[diagdir][track];