Elide vehicle random trigger callbacks

src/newgrf_commons.h

@@ -338,6 +338,7 @@ enum SpriteGroupCallbacksUsed : uint8 {
 	SGCU_ALL                            = 0xFF,
 	SGCU_VEHICLE_32DAY_CALLBACK         = 1 << 0,
 	SGCU_VEHICLE_REFIT_COST             = 1 << 1,
+	SGCU_RANDOM_TRIGGER                 = 1 << 2,
 };
 DECLARE_ENUM_AS_BIT_SET(SpriteGroupCallbacksUsed)
 

src/newgrf_engine.cpp

@@ -1378,19 +1378,28 @@ static void DoTriggerVehicle(Vehicle *v, VehicleTrigger trigger, byte base_rando
 	/* We can't trigger a non-existent vehicle... */
 	assert(v != nullptr);
 
-	VehicleResolverObject object(v->engine_type, v, VehicleResolverObject::WO_CACHED, false, CBID_RANDOM_TRIGGER);
-	object.waiting_triggers = v->waiting_triggers | trigger;
-	v->waiting_triggers = object.waiting_triggers; // store now for var 5F
+	uint32 reseed = 0;
+	if (Engine::Get(v->engine_type)->callbacks_used & SGCU_RANDOM_TRIGGER) {
+		VehicleResolverObject object(v->engine_type, v, VehicleResolverObject::WO_CACHED, false, CBID_RANDOM_TRIGGER);
+		object.waiting_triggers = v->waiting_triggers | trigger;
+		v->waiting_triggers = object.waiting_triggers; // store now for var 5F
 
-	const SpriteGroup *group = object.Resolve();
-	if (group == nullptr) return;
+		const SpriteGroup *group = object.Resolve();
+		if (group == nullptr) return;
+
+		/* Store remaining triggers. */
+		v->waiting_triggers = object.GetRemainingTriggers();
 
-	/* Store remaining triggers. */
-	v->waiting_triggers = object.GetRemainingTriggers();
+		reseed = object.GetReseedSum();
+	} else {
+		v->waiting_triggers |= trigger;
+
+		const Engine *e = Engine::Get(v->engine_type);
+		if (!(e->grf_prop.spritegroup[v->cargo_type] || e->grf_prop.spritegroup[CT_DEFAULT])) return;
+	}
 
 	/* Rerandomise bits. Scopes other than SELF are invalid for rerandomisation. For bug-to-bug-compatibility with TTDP we ignore the scope. */
 	byte new_random_bits = Random();
-	uint32 reseed = object.GetReseedSum();
 	v->random_bits &= ~reseed;
 	v->random_bits |= (first ? new_random_bits : base_random_bits) & reseed;
 

src/newgrf_spritegroup.cpp

@@ -341,6 +341,10 @@ void DeterministicSpriteGroup::AnalyseCallbacks(AnalyseCallbackOperation &op) co
 								op.callbacks_used |= SGCU_VEHICLE_REFIT_COST;
 								break;
 
+							case CBID_RANDOM_TRIGGER:
+								op.callbacks_used |= SGCU_RANDOM_TRIGGER;
+								break;
+
 							case CBID_VEHICLE_MODIFY_PROPERTY:
 								if (range.group != nullptr) {
 									AnalyseCallbackOperation cb36_op;
@@ -433,6 +437,10 @@ const SpriteGroup *RandomizedSpriteGroup::Resolve(ResolverObject &object) const
 	return SpriteGroup::Resolve(this->groups[index], object, false);
 }
 
+void RandomizedSpriteGroup::AnalyseCallbacks(AnalyseCallbackOperation &op) const
+{
+	if (op.mode == ACOM_CB_VAR) op.callbacks_used |= SGCU_RANDOM_TRIGGER;
+}
 
 const SpriteGroup *RealSpriteGroup::Resolve(ResolverObject &object) const
 {

src/newgrf_spritegroup.h

@@ -219,6 +219,8 @@ struct RandomizedSpriteGroup : SpriteGroup {
 
 	std::vector<const SpriteGroup *> groups; ///< Take the group with appropriate index:
 
+	void AnalyseCallbacks(AnalyseCallbackOperation &op) const override;
+
 protected:
 	const SpriteGroup *Resolve(ResolverObject &object) const;
 };