From c37beb78eeae598db0ae8a2883ac0e3ee3dc0ef5 Mon Sep 17 00:00:00 2001
From: Jonathan G Rennison <j.g.rennison@gmail.com>
Date: Sat, 27 Feb 2021 21:31:23 +0000
Subject: [PATCH] Check for broken custom bridge head states, and bump save
 version

---
 src/saveload/afterload.cpp       | 42 ++++++++++++++++++++++++++++++++
 src/saveload/extended_ver_sl.cpp |  2 +-
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/src/saveload/afterload.cpp b/src/saveload/afterload.cpp
index 6fe47f8826..660ad144e4 100644
--- a/src/saveload/afterload.cpp
+++ b/src/saveload/afterload.cpp
@@ -1542,6 +1542,48 @@ bool AfterLoadGame()
 		}
 	}
 
+	if (SlXvIsFeaturePresent(XSLFI_CUSTOM_BRIDGE_HEADS, 1, 3)) {
+		/* fix any mismatched road/tram bits */
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (IsBridgeTile(t) && GetTunnelBridgeTransportType(t) == TRANSPORT_ROAD) {
+				for (RoadTramType rtt : { RTT_TRAM, RTT_ROAD }) {
+					RoadType rt = GetRoadType(t, rtt);
+					if (rt == INVALID_ROADTYPE) continue;
+					RoadBits rb = GetCustomBridgeHeadRoadBits(t, rtt);
+					DiagDirection dir = GetTunnelBridgeDirection(t);
+					if (!(rb & DiagDirToRoadBits(dir))) continue;
+
+					if (HasAtMostOneBit(rb)) {
+						DEBUG(misc, 0, "Fixing road bridge head state (case A) at tile 0x%X", t);
+						rb |= DiagDirToRoadBits(ReverseDiagDir(dir));
+						SetCustomBridgeHeadRoadBits(t, rtt, rb);
+					}
+
+					TileIndex end = GetOtherBridgeEnd(t);
+					if (GetRoadType(end, rtt) == INVALID_ROADTYPE) {
+						DEBUG(misc, 0, "Fixing road bridge head state (case B) at tile 0x%X -> 0x%X", t, end);
+						SetRoadType(end, rtt, rt);
+						SetCustomBridgeHeadRoadBits(end, rtt, AxisToRoadBits(DiagDirToAxis(dir)));
+						continue;
+					}
+
+					if (GetRoadType(end, rtt) != rt) {
+						DEBUG(misc, 0, "Fixing road bridge head state (case C) at tile 0x%X -> 0x%X", t, end);
+						SetRoadType(end, rtt, rt);
+					}
+
+					RoadBits end_rb = GetCustomBridgeHeadRoadBits(end, rtt);
+					if (!(end_rb & DiagDirToRoadBits(ReverseDiagDir(dir)))) {
+						DEBUG(misc, 0, "Fixing road bridge head state (case D) at tile 0x%X -> 0x%X", t, end);
+						end_rb |= DiagDirToRoadBits(ReverseDiagDir(dir));
+						if (HasAtMostOneBit(end_rb)) end_rb |= DiagDirToRoadBits(dir);
+						SetCustomBridgeHeadRoadBits(end, rtt, end_rb);
+					}
+				}
+			}
+		}
+	}
+
 	/* Elrails got added in rev 24 */
 	if (IsSavegameVersionBefore(SLV_24)) {
 		RailType min_rail = RAILTYPE_ELECTRIC;
diff --git a/src/saveload/extended_ver_sl.cpp b/src/saveload/extended_ver_sl.cpp
index 9ad1fce10b..177d35b489 100644
--- a/src/saveload/extended_ver_sl.cpp
+++ b/src/saveload/extended_ver_sl.cpp
@@ -103,7 +103,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_CARGO_TYPE_ORDERS,      XSCF_NULL,                3,   3, "cargo_type_orders",         nullptr, nullptr, "ORDX,VEOX" },
 	{ XSLFI_EXTENDED_GAMELOG,       XSCF_NULL,                1,   1, "extended_gamelog",          nullptr, nullptr, nullptr        },
 	{ XSLFI_STATION_CATCHMENT_INC,  XSCF_NULL,                1,   1, "station_catchment_inc",     nullptr, nullptr, nullptr        },
-	{ XSLFI_CUSTOM_BRIDGE_HEADS,    XSCF_NULL,                3,   3, "custom_bridge_heads",       nullptr, nullptr, nullptr        },
+	{ XSLFI_CUSTOM_BRIDGE_HEADS,    XSCF_NULL,                4,   4, "custom_bridge_heads",       nullptr, nullptr, nullptr        },
 	{ XSLFI_CHUNNEL,                XSCF_NULL,                2,   2, "chunnel",                   nullptr, nullptr, "TUNN"      },
 	{ XSLFI_SCHEDULED_DISPATCH,     XSCF_NULL,                2,   2, "scheduled_dispatch",        nullptr, nullptr, nullptr        },
 	{ XSLFI_MORE_TOWN_GROWTH_RATES, XSCF_NULL,                1,   1, "more_town_growth_rates",    nullptr, nullptr, nullptr        },