Method GetScope

src/newgrf_engine.cpp:318–362

virtual */

/* virtual */ ScopeResolver *VehicleResolverObject::GetScope(VarSpriteGroupScope scope, uint8_t relative)
{
	switch (scope) {
		case VSG_SCOPE_SELF:   return &this->self_scope;
		case VSG_SCOPE_PARENT: return &this->parent_scope;
		case VSG_SCOPE_RELATIVE: {
			int32_t count = GB(relative, 0, 4);
			if (this->self_scope.v != nullptr && (relative != this->cached_relative_count || count == 0)) {
				/* Note: This caching only works as long as the VSG_SCOPE_RELATIVE cannot be used in
				 *       VarAct2 with procedure calls. */
				if (count == 0) count = this->GetRegister(0x100);

				const Vehicle *v = nullptr;
				switch (GB(relative, 6, 2)) {
					default: NOT_REACHED();
					case 0x00: // count back (away from the engine), starting at this vehicle
						v = this->self_scope.v;
						break;
					case 0x01: // count forward (toward the engine), starting at this vehicle
						v = this->self_scope.v;
						count = -count;
						break;
					case 0x02: // count back, starting at the engine
						v = this->parent_scope.v;
						break;
					case 0x03: { // count back, starting at the first vehicle in this chain of vehicles with the same ID, as for vehicle variable 41
						const Vehicle *self = this->self_scope.v;
						for (const Vehicle *u = self->First(); u != self; u = u->Next()) {
							if (u->engine_type != self->engine_type) {
								v = nullptr;
							} else {
								if (v == nullptr) v = u;
							}
						}
						if (v == nullptr) v = self;
						break;
					}
				}
				this->relative_scope.SetVehicle(v->Move(count));
			}
			return &this->relative_scope;
		}
		default: return ResolverObject::GetScope(scope, relative);
	}
}

/**
 * Determines the livery of an engine.