From 93d1d8773fab6eda973b19631a0473b11bba35e3 Mon Sep 17 00:00:00 2001
From: dP <dp@dpointer.org>
Date: Fri, 15 May 2020 23:18:03 +0300
Subject: Fix: Desync after house replacement

---
 src/town_cmd.cpp | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

(limited to 'src')

diff --git a/src/town_cmd.cpp b/src/town_cmd.cpp
index 507cccd56..1d550fb02 100644
--- a/src/town_cmd.cpp
+++ b/src/town_cmd.cpp
@@ -454,13 +454,22 @@ uint32 GetWorldPopulation()
 
 /**
  * Remove stations from nearby station list if a town is no longer in the catchment area of each.
+ * To improve performance only checks stations that cover the provided house area (doesn't need to contain an actual house).
  * @param t Town to work on
+ * @param tile Location of house area (north part)
+ * @param flags BuildingFlags containing the size of house area
  */
-static void RemoveNearbyStations(Town *t)
+static void RemoveNearbyStations(Town *t, TileIndex tile, BuildingFlags flags)
 {
 	for (StationList::iterator it = t->stations_near.begin(); it != t->stations_near.end(); /* incremented inside loop */) {
 		const Station *st = *it;
-		if (!st->CatchmentCoversTown(t->index)) {
+
+		bool covers_area = st->TileIsInCatchment(tile);
+		if (flags & BUILDING_2_TILES_Y)   covers_area |= st->TileIsInCatchment(tile + TileDiffXY(0, 1));
+		if (flags & BUILDING_2_TILES_X)   covers_area |= st->TileIsInCatchment(tile + TileDiffXY(1, 0));
+		if (flags & BUILDING_HAS_4_TILES) covers_area |= st->TileIsInCatchment(tile + TileDiffXY(1, 1));
+
+		if (covers_area && !st->CatchmentCoversTown(t->index)) {
 			it = t->stations_near.erase(it);
 		} else {
 			++it;
@@ -621,11 +630,7 @@ static void TileLoop_Town(TileIndex tile)
 		ClearTownHouse(t, tile);
 
 		/* Rebuild with another house? */
-		if (GB(r, 24, 8) < 12 || !BuildTownHouse(t, tile))
-		{
-			/* House wasn't replaced, so remove it */
-			if (!_generating_world) RemoveNearbyStations(t);
-		}
+		if (GB(r, 24, 8) >= 12) BuildTownHouse(t, tile);
 	}
 
 	cur_company.Restore();
@@ -654,7 +659,6 @@ static CommandCost ClearTile_Town(TileIndex tile, DoCommandFlag flags)
 	ChangeTownRating(t, -rating, RATING_HOUSE_MINIMUM, flags);
 	if (flags & DC_EXEC) {
 		ClearTownHouse(t, tile);
-		RemoveNearbyStations(t);
 	}
 
 	return cost;
@@ -2666,11 +2670,12 @@ void ClearTownHouse(Town *t, TileIndex tile)
 	}
 
 	/* Do the actual clearing of tiles */
-	uint eflags = hs->building_flags;
 	DoClearTownHouseHelper(tile, t, house);
-	if (eflags & BUILDING_2_TILES_Y)   DoClearTownHouseHelper(tile + TileDiffXY(0, 1), t, ++house);
-	if (eflags & BUILDING_2_TILES_X)   DoClearTownHouseHelper(tile + TileDiffXY(1, 0), t, ++house);
-	if (eflags & BUILDING_HAS_4_TILES) DoClearTownHouseHelper(tile + TileDiffXY(1, 1), t, ++house);
+	if (hs->building_flags & BUILDING_2_TILES_Y)   DoClearTownHouseHelper(tile + TileDiffXY(0, 1), t, ++house);
+	if (hs->building_flags & BUILDING_2_TILES_X)   DoClearTownHouseHelper(tile + TileDiffXY(1, 0), t, ++house);
+	if (hs->building_flags & BUILDING_HAS_4_TILES) DoClearTownHouseHelper(tile + TileDiffXY(1, 1), t, ++house);
+
+	RemoveNearbyStations(t, tile, hs->building_flags);
 
 	UpdateTownRadius(t);
 
-- 
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