Preserve custom bridge head road data when upgrading bridges.

Based on commit 301925f948c9b36966c9c668e1476c2485425338

src/bridge_map.h

@@ -147,13 +147,20 @@ static inline void MakeBridgeRamp(TileIndex t, Owner o, BridgeType bridgetype, D
  * @param bridgetype the type of bridge this bridge ramp belongs to
  * @param d          the direction this ramp must be facing
  * @param r          the road type of the bridge
+ * @param upgrade    whether the bridge is an upgrade instead of a totally new bridge
  */
-static inline void MakeRoadBridgeRamp(TileIndex t, Owner o, Owner owner_road, Owner owner_tram, BridgeType bridgetype, DiagDirection d, RoadTypes r)
+static inline void MakeRoadBridgeRamp(TileIndex t, Owner o, Owner owner_road, Owner owner_tram, BridgeType bridgetype, DiagDirection d, RoadTypes r, bool upgrade)
 {
+	// Backup custom bridgehead data.
+	uint custom_bridge_head_backup = GB(_m[t].m2, 0, 8);
+
 	MakeBridgeRamp(t, o, bridgetype, d, TRANSPORT_ROAD, 0);
 	SetRoadOwner(t, ROADTYPE_ROAD, owner_road);
 	if (owner_tram != OWNER_TOWN) SetRoadOwner(t, ROADTYPE_TRAM, owner_tram);
 	SetRoadTypes(t, r);
+
+	// Restore custom bridgehead data if we're upgrading an existing bridge.
+	if (upgrade) SB(_m[t].m2, 0, 8, custom_bridge_head_backup);
 }
 
 /**

src/tunnelbridge_cmd.cpp

@@ -327,6 +327,7 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 	CommandCost cost(EXPENSES_CONSTRUCTION);
 	Owner owner;
 	bool is_new_owner;
+	bool is_upgrade = false;
 	if (IsBridgeTile(tile_start) && IsBridgeTile(tile_end) &&
 			GetOtherBridgeEnd(tile_start) == tile_end &&
 			GetTunnelBridgeTransportType(tile_start) == transport_type) {
@@ -381,6 +382,8 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 
 			default: break;
 		}
+
+		is_upgrade = true;
 	} else {
 		/* Build a new bridge. */
 
@@ -507,18 +510,12 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 					if (HasBit(prev_roadtypes, ROADTYPE_ROAD) && GetRoadOwner(tile_start, ROADTYPE_ROAD) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_ROAD);
 					if (HasBit(prev_roadtypes, ROADTYPE_TRAM) && GetRoadOwner(tile_start, ROADTYPE_TRAM) == OWNER_NONE) ClrBit(prev_roadtypes, ROADTYPE_TRAM);
 				}
-				if (c != NULL) {
-					/* Add all new road types to the company infrastructure counter. */
-					RoadType new_rt;
-					FOR_EACH_SET_ROADTYPE(new_rt, roadtypes ^ prev_roadtypes) {
-						/* A full diagonal road tile has two road bits. */
-						c->infrastructure.road[new_rt] += (bridge_len + 2) * 2 * TUNNELBRIDGE_TRACKBIT_FACTOR;
-					}
-				}
+				if (is_upgrade) SubtractRoadTunnelBridgeInfrastructure(tile_start, tile_end);
 				Owner owner_road = HasBit(prev_roadtypes, ROADTYPE_ROAD) ? GetRoadOwner(tile_start, ROADTYPE_ROAD) : company;
 				Owner owner_tram = HasBit(prev_roadtypes, ROADTYPE_TRAM) ? GetRoadOwner(tile_start, ROADTYPE_TRAM) : company;
-				MakeRoadBridgeRamp(tile_start, owner, owner_road, owner_tram, bridge_type, dir,                 roadtypes);
-				MakeRoadBridgeRamp(tile_end,   owner, owner_road, owner_tram, bridge_type, ReverseDiagDir(dir), roadtypes);
+				MakeRoadBridgeRamp(tile_start, owner, owner_road, owner_tram, bridge_type, dir,                 roadtypes, is_upgrade);
+				MakeRoadBridgeRamp(tile_end,   owner, owner_road, owner_tram, bridge_type, ReverseDiagDir(dir), roadtypes, is_upgrade);
+				AddRoadTunnelBridgeInfrastructure(tile_start, tile_end);
 				break;
 			}