Function GetRotorOverrideSprite

src/newgrf_engine.cpp:1135–1165

}

static void GetRotorOverrideSprite(EngineID engine, const struct Aircraft *v, EngineImageType image_type, VehicleSpriteSeq *result)
{
	const Engine *e = Engine::Get(engine);

	/* Only valid for helicopters */
	assert(e->type == VEH_AIRCRAFT);
	assert(!(e->VehInfo<AircraftVehicleInfo>().subtype & AIR_CTOL));

	/* We differ from TTDPatch by resolving the sprite using the primary vehicle 'v', and not using the rotor vehicle 'v->Next()->Next()'.
	 * TTDPatch copies some variables between the vehicles each time, to somehow synchronize the rotor vehicle with the primary vehicle.
	 * We use 'rotor_in_gui' to replicate when the variables differ.
	 * But some other variables like 'rotor state' and 'rotor speed' are not available in OpenTTD, while they are in TTDPatch. */
	bool rotor_in_gui = image_type != EIT_ON_MAP;
	VehicleResolverObject object(engine, v, VehicleResolverObject::WO_SELF, rotor_in_gui, CBID_NO_CALLBACK);
	result->Clear();
	uint rotor_pos = v == nullptr || rotor_in_gui ? 0 : v->Next()->Next()->state;

	bool sprite_stack = e->info.misc_flags.Test(EngineMiscFlag::SpriteStack);
	uint max_stack = sprite_stack ? static_cast<uint>(std::size(result->seq)) : 1;
	for (uint stack = 0; stack < max_stack; ++stack) {
		object.callback_param1 = image_type | (stack << 8);
		const auto *group = object.Resolve<ResultSpriteGroup>();
		int32_t reg100 = sprite_stack ? object.GetRegister(0x100) : 0;
		if (group != nullptr && group->num_sprites != 0) {
			result->seq[result->count].sprite = group->sprite + (rotor_pos % group->num_sprites);
			result->seq[result->count].pal    = GB(reg100, 0, 16); // zero means default recolouring
			result->count++;
		}
		if (!HasBit(reg100, 31)) break;
	}
}

void GetCustomRotorSprite(const struct Aircraft *v, EngineImageType image_type, VehicleSpriteSeq *result)
{