Multi-part ships: Require feature test to enable callback 16

docs/newgrf-additions.html

@@ -895,7 +895,8 @@
 	<h3 id="callbacks_ships"><a href="https://newgrf-specs.tt-wiki.net/wiki/Callbacks">Callbacks - Ships</a></h3>
 	<h4 id="callbacks_ships_articulated">Multi-part ships</h4>
 	<p><b><a href="https://newgrf-specs.tt-wiki.net/wiki/Callbacks#Articulated_engine_.2816.29">Callback 16 - Articulated engine</a> may also be used for ships.</b><br />
-	This functions the same as for trains and road vehicles, and is enabled in the same way (bit 4 of ship property 12).<br />
+	The feature name: <font face="monospace">multi_part_ships</font> must be tested for to enable this callback for ships.<br />
+	This functions the same as for trains and road vehicles, and is enabled for individual engines in the same way (bit 4 of ship property 12).<br />
 	Additional ship parts are not used for graphics, they are only used for additional cargo capacity.<br />
 	The graphics chain for the primary vehicle may check the cargo states of the other ship parts if required.<br />
 	Additional ship parts may be refitted individually.

src/articulated_vehicles.cpp

@@ -15,6 +15,7 @@
 #include "engine_func.h"
 #include "company_func.h"
 #include "newgrf.h"
+#include "newgrf_extension.h"
 #include <vector>
 
 #include "table/strings.h"
@@ -37,6 +38,10 @@ static EngineID GetNextArticulatedPart(uint index, EngineID front_type, Vehicle
 
 	const Engine *front_engine = Engine::Get(front_type);
 
+	if (front_engine->type == VEH_SHIP && !(front_engine->GetGRF() != nullptr && HasBit(front_engine->GetGRF()->observed_feature_tests, GFTOF_MULTI_PART_SHIPS))) {
+		return INVALID_ENGINE;
+	}
+
 	uint16 callback = GetVehicleCallback(CBID_VEHICLE_ARTIC_ENGINE, index, 0, front_type, front);
 	if (callback == CALLBACK_FAILED) return INVALID_ENGINE;
 

src/newgrf_extension.cpp

@@ -66,7 +66,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("town_uncapped_variables", 1),
 	GRFFeatureInfo("town_zone_callback", 1, GFTOF_TOWN_ZONE_CALLBACK),
 	GRFFeatureInfo("more_varaction2_types", 1, GFTOF_MORE_VARACTION2_TYPES),
-	GRFFeatureInfo("multi_part_ships", 1),
+	GRFFeatureInfo("multi_part_ships", 1, GFTOF_MULTI_PART_SHIPS),
 	GRFFeatureInfo(),
 };
 

src/newgrf_extension.h

@@ -101,6 +101,7 @@ enum GRFFeatureTestObservationFlag : uint8 {
 	GFTOF_MORE_ACTION2_IDS,
 	GFTOF_TOWN_ZONE_CALLBACK,
 	GFTOF_MORE_VARACTION2_TYPES,
+	GFTOF_MULTI_PART_SHIPS,
 
 	GFTOF_INVALID = 0xFF,
 };