dbus/properties: allow removing to/from wire transforms

Useful when properties are only read/written in one direction.

Author: outfoxxed

src/dbus/properties.hpp

@@ -143,9 +143,6 @@ template <typename T>
 struct DBusDataTransform {
 	using Wire = T;
 	using Data = T;
-
-	static DBusResult<Data> fromWire(Wire&& wire) { return DBusResult<T>(std::move(wire)); }
-	static Wire toWire(const Data& value) { return value; }
 };
 
 namespace bindable_p {
@@ -166,6 +163,20 @@ struct BindableType {
 	using Type = Meta::Type;
 };
 
+template <typename T, typename = void>
+struct HasFromWire: std::false_type {};
+
+template <typename T>
+struct HasFromWire<T, std::void_t<decltype(T::fromWire(std::declval<typename T::Wire>()))>>
+    : std::true_type {};
+
+template <typename T, typename = void>
+struct HasToWire: std::false_type {};
+
+template <typename T>
+struct HasToWire<T, std::void_t<decltype(T::toWire(std::declval<typename T::Data>()))>>
+    : std::true_type {};
+
 } // namespace bindable_p
 
 template <
@@ -206,12 +217,14 @@ class DBusBindableProperty: public DBusPropertyCore {
 	QDBusError store(const QVariant& variant) override {
 		DBusResult<DataType> result;
 
-		if constexpr (std::is_same_v<WireType, BaseType>) {
-			result = demarshallVariant<DataType>(variant);
-		} else {
+		if constexpr (bindable_p::HasFromWire<Transform>::value) {
 			auto wireResult = demarshallVariant<WireType>(variant);
 			if (!wireResult.isValid()) return wireResult.error;
 			result = Transform::fromWire(std::move(wireResult.value));
+		} else if constexpr (std::is_same_v<WireType, BaseType>) {
+			result = demarshallVariant<DataType>(variant);
+		} else {
+			return QDBusError(QDBusError::NotSupported, "This property cannot be deserialized");
 		}
 
 		if (!result.isValid()) return result.error;
@@ -225,10 +238,12 @@ class DBusBindableProperty: public DBusPropertyCore {
 	}
 
 	QVariant serialize() override {
-		if constexpr (std::is_same_v<WireType, BaseType>) {
+		if constexpr (bindable_p::HasToWire<Transform>::value) {
+			return QVariant::fromValue(Transform::toWire(this->bindable()->value()));
+		} else if constexpr (std::is_same_v<WireType, BaseType>) {
 			return QVariant::fromValue(this->bindable()->value());
 		} else {
-			return QVariant::fromValue(Transform::toWire(this->bindable()->value()));
+			return QVariant();
 		}
 	}
 

src/services/upower/device.cpp

@@ -105,8 +105,6 @@ DBusResult<qreal> DBusDataTransform<PowerPercentage>::fromWire(qreal wire) {
 	return DBusResult(wire * 0.01);
 }
 
-qreal DBusDataTransform<PowerPercentage>::toWire(const qreal& value) { return value * 100; }
-
 DBusResult<UPowerDeviceState::Enum>
 DBusDataTransform<UPowerDeviceState::Enum>::fromWire(quint32 wire) {
 	if (wire != UPowerDeviceType::Battery && wire >= UPowerDeviceState::Unknown
@@ -120,10 +118,6 @@ DBusDataTransform<UPowerDeviceState::Enum>::fromWire(quint32 wire) {
 	);
 }
 
-quint32 DBusDataTransform<UPowerDeviceState::Enum>::toWire(const UPowerDeviceState::Enum& value) {
-	return static_cast<quint32>(value);
-}
-
 DBusResult<UPowerDeviceType::Enum> DBusDataTransform<UPowerDeviceType::Enum>::fromWire(quint32 wire
 ) {
 	if (wire >= UPowerDeviceType::Unknown && wire <= UPowerDeviceType::BluetoothGeneric) {
@@ -135,8 +129,4 @@ DBusResult<UPowerDeviceType::Enum> DBusDataTransform<UPowerDeviceType::Enum>::fr
 	);
 }
 
-quint32 DBusDataTransform<UPowerDeviceType::Enum>::toWire(const UPowerDeviceType::Enum& value) {
-	return static_cast<quint32>(value);
-}
-
 } // namespace qs::dbus

src/services/upower/device.hpp

@@ -91,23 +91,20 @@ struct DBusDataTransform<qs::service::upower::UPowerDeviceState::Enum> {
 	using Wire = quint32;
 	using Data = qs::service::upower::UPowerDeviceState::Enum;
 	static DBusResult<Data> fromWire(Wire wire);
-	static Wire toWire(const Data& value);
 };
 
 template <>
 struct DBusDataTransform<qs::service::upower::UPowerDeviceType::Enum> {
 	using Wire = quint32;
 	using Data = qs::service::upower::UPowerDeviceType::Enum;
 	static DBusResult<Data> fromWire(Wire wire);
-	static Wire toWire(const Data& value);
 };
 
 template <>
 struct DBusDataTransform<qs::service::upower::PowerPercentage> {
 	using Wire = qreal;
 	using Data = qreal;
 	static DBusResult<Data> fromWire(Wire wire);
-	static Wire toWire(const Data& value);
 };
 
 } // namespace qs::dbus