Add NewGRF bridge property to prevent town or AI/GS building bridge type

docs/newgrf-additions.html

@@ -203,6 +203,16 @@
 	</table>
 	</p>
 	<p>This is indicated by the feature name: <font face="monospace">action0_bridge_pillar_flags</font>, version 1</p>
+	<h4>Bridge availability flags (mappable property: bridge_availability_flags)</h4>
+	<p>This property sets the availability flags for this bridge type.<br />
+	The property length is 1 byte. The format is:
+	<table>
+	<tr><th>Bit</th><th>Value</th><th>Meaning</th></tr>
+	<tr><td>0</td><td>1</td><td>Towns may not build this bridge type</td></tr>
+	<tr><td>1</td><td>2</td><td>Scripts (AI/GS) may not build this bridge type</td></tr>
+	</table>
+	</p>
+	<p>This is indicated by the feature name: <font face="monospace">action0_bridge_availability_flags</font>, version 1</p>
 	<h4>More bridges (16 instead of 13)</h4>
 	<p>This is indicated by the feature name: <font face="monospace">more_bridge_types</font>, version 1</p>
 	<h3><a href="https://newgrf-specs.tt-wiki.net/wiki/Action0/Railtypes">Action 0 - Railtypes</a></h3>

src/bridge.h

@@ -54,6 +54,8 @@ DECLARE_ENUM_AS_BIT_SET(BridgePiecePillarFlags)
 enum BridgeSpecCtrlFlags {
 	BSCF_CUSTOM_PILLAR_FLAGS,
 	BSCF_INVALID_PILLAR_FLAGS,
+	BSCF_NOT_AVAILABLE_TOWN,
+	BSCF_NOT_AVAILABLE_AI_GS,
 };
 
 /**
@@ -94,6 +96,7 @@ static inline const BridgeSpec *GetBridgeSpec(BridgeType i)
 void DrawBridgeMiddle(const TileInfo *ti);
 
 CommandCost CheckBridgeAvailability(BridgeType bridge_type, uint bridge_len, DoCommandFlag flags = DC_NONE);
+bool MayTownBuildBridgeType(BridgeType bridge_type);
 int CalcBridgeLenCostFactor(int x);
 BridgePiecePillarFlags GetBridgeTilePillarFlags(TileIndex tile, TileIndex northern_bridge_end, TileIndex southern_bridge_end, BridgeType bridge_type, TransportType bridge_transport_type);
 

src/newgrf.cpp

@@ -2310,6 +2310,14 @@ static ChangeInfoResult BridgeChangeInfo(uint brid, int numinfo, int prop, const
 				SetBit(bridge->ctrl_flags, BSCF_CUSTOM_PILLAR_FLAGS);
 				break;
 
+			case A0RPI_BRIDGE_AVAILABILITY_FLAGS: {
+				if (MappedPropertyLengthMismatch(buf, 1, mapping_entry)) break;
+				byte flags = buf->ReadByte();
+				SB(bridge->ctrl_flags, BSCF_NOT_AVAILABLE_TOWN, 1, HasBit(flags, 0) ? 1 : 0);
+				SB(bridge->ctrl_flags, BSCF_NOT_AVAILABLE_AI_GS, 1, HasBit(flags, 1) ? 1 : 0);
+				break;
+			}
+
 			default:
 				ret = HandleAction0PropertyDefault(buf, prop);
 				break;
@@ -8369,6 +8377,7 @@ static const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("more_bridge_types", 1),
 	GRFFeatureInfo("action0_bridge_prop14", 1),
 	GRFFeatureInfo("action0_bridge_pillar_flags", 1),
+	GRFFeatureInfo("action0_bridge_availability_flags", 1),
 	GRFFeatureInfo("action5_programmable_signals", 1),
 	GRFFeatureInfo("action0_railtype_programmable_signals", 1),
 	GRFFeatureInfo("action0_railtype_restricted_signals", 1),
@@ -8487,6 +8496,7 @@ static const GRFPropertyMapDefinition _grf_action0_remappable_properties[] = {
 	GRFPropertyMapDefinition(GSF_STATIONS, A0RPI_STATION_DISALLOWED_BRIDGE_PILLARS, "station_disallowed_bridge_pillars"),
 	GRFPropertyMapDefinition(GSF_BRIDGES, A0RPI_BRIDGE_MENU_ICON, "bridge_menu_icon"),
 	GRFPropertyMapDefinition(GSF_BRIDGES, A0RPI_BRIDGE_PILLAR_FLAGS, "bridge_pillar_flags"),
+	GRFPropertyMapDefinition(GSF_BRIDGES, A0RPI_BRIDGE_AVAILABILITY_FLAGS, "bridge_availability_flags"),
 	GRFPropertyMapDefinition(GSF_RAILTYPES, A0RPI_RAILTYPE_ENABLE_PROGRAMMABLE_SIGNALS, "railtype_enable_programmable_signals"),
 	GRFPropertyMapDefinition(GSF_RAILTYPES, A0RPI_RAILTYPE_ENABLE_RESTRICTED_SIGNALS, "railtype_enable_restricted_signals"),
 	GRFPropertyMapDefinition(),

src/newgrf.h

@@ -114,6 +114,7 @@ enum Action0RemapPropertyIds {
 	A0RPI_STATION_DISALLOWED_BRIDGE_PILLARS,
 	A0RPI_BRIDGE_MENU_ICON,
 	A0RPI_BRIDGE_PILLAR_FLAGS,
+	A0RPI_BRIDGE_AVAILABILITY_FLAGS,
 	A0RPI_RAILTYPE_ENABLE_PROGRAMMABLE_SIGNALS,
 	A0RPI_RAILTYPE_ENABLE_RESTRICTED_SIGNALS,
 };

src/script/api/script_bridge.cpp

@@ -20,7 +20,9 @@
 
 /* static */ bool ScriptBridge::IsValidBridge(BridgeID bridge_id)
 {
-	return bridge_id < MAX_BRIDGES && ::GetBridgeSpec(bridge_id)->avail_year <= _cur_year;
+	if (bridge_id >= MAX_BRIDGES) return false;
+	const BridgeSpec *b = ::GetBridgeSpec(bridge_id);
+	return b->avail_year <= _cur_year && !HasBit(b->ctrl_flags, BSCF_NOT_AVAILABLE_AI_GS);
 }
 
 /* static */ bool ScriptBridge::IsBridgeTile(TileIndex tile)
@@ -77,7 +79,7 @@ static void _DoCommandReturnBuildBridge1(class ScriptInstance *instance)
 	EnforcePrecondition(false, vehicle_type != ScriptVehicle::VT_ROAD || ScriptRoad::IsRoadTypeAvailable(ScriptRoad::GetCurrentRoadType()));
 	EnforcePrecondition(false, ScriptObject::GetCompany() != OWNER_DEITY || vehicle_type == ScriptVehicle::VT_ROAD);
 
-	uint type = 0;
+	uint type = (1 << 17);
 	switch (vehicle_type) {
 		case ScriptVehicle::VT_ROAD:
 			type |= (TRANSPORT_ROAD << 15);

src/town_cmd.cpp

@@ -1303,7 +1303,7 @@ static bool GrowTownWithBridge(const Town *t, const TileIndex tile, const DiagDi
 	for (;;) {
 		/* Can we actually build the bridge? */
 		RoadType rt = GetTownRoadType(t);
-		if (DoCommand(tile, bridge_tile, bridge_type | rt << 8 | TRANSPORT_ROAD << 15, CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)), CMD_BUILD_BRIDGE).Succeeded()) {
+		if (MayTownBuildBridgeType(bridge_type) && DoCommand(tile, bridge_tile, bridge_type | rt << 8 | TRANSPORT_ROAD << 15, CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)), CMD_BUILD_BRIDGE).Succeeded()) {
 			DoCommand(tile, bridge_tile, bridge_type | rt << 8 | TRANSPORT_ROAD << 15, DC_EXEC | CommandFlagsToDCFlags(GetCommandFlags(CMD_BUILD_BRIDGE)), CMD_BUILD_BRIDGE);
 			_grow_town_result = GROWTH_SUCCEED;
 			return true;

src/tunnelbridge_cmd.cpp

@@ -274,6 +274,14 @@ CommandCost CheckBridgeAvailability(BridgeType bridge_type, uint bridge_len, DoC
 	return_cmd_error(STR_ERROR_BRIDGE_TOO_LONG);
 }
 
+bool MayTownBuildBridgeType(BridgeType bridge_type)
+{
+	if (bridge_type >= MAX_BRIDGES) return false;
+
+	const BridgeSpec *b = GetBridgeSpec(bridge_type);
+	return !HasBit(b->ctrl_flags, BSCF_NOT_AVAILABLE_TOWN);
+}
+
 /**
  * Build a Bridge
  * @param end_tile end tile
@@ -283,6 +291,7 @@ CommandCost CheckBridgeAvailability(BridgeType bridge_type, uint bridge_len, DoC
  * - p2 = (bit  0- 7) - bridge type (hi bh)
  * - p2 = (bit  8-13) - rail type or road types.
  * - p2 = (bit 15-16) - transport type.
+ * - p2 = (bit 17)    - script command
  * @param text unused
  * @return the cost of this operation or an error
  */
@@ -300,6 +309,8 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 
 	TransportType transport_type = Extract<TransportType, 15, 2>(p2);
 
+	bool script_cmd = HasBit(p2, 17);
+
 	/* type of bridge */
 	switch (transport_type) {
 		case TRANSPORT_ROAD:
@@ -354,6 +365,7 @@ CommandCost CmdBuildBridge(TileIndex end_tile, DoCommandFlag flags, uint32 p1, u
 		/* set and test bridge length, availability */
 		CommandCost ret = CheckBridgeAvailability(bridge_type, bridge_len, flags);
 		if (ret.Failed()) return ret;
+		if (script_cmd && HasBit(GetBridgeSpec(bridge_type)->ctrl_flags, BSCF_NOT_AVAILABLE_AI_GS)) return CMD_ERROR;
 	} else {
 		if (bridge_len > _settings_game.construction.max_bridge_length) return_cmd_error(STR_ERROR_BRIDGE_TOO_LONG);
 	}