QNotifiedProperty: Add guard callback
A guard callback is a predicate which takes the new value set by setValue or computed as the result of a binding expression. If it returns false, the value is discarded and the old value is kept. Note that due to lazyness, when setting a binding, we still notify everyone as the binding is only evaluated on demand, and the guard can thus only run when someone actually queries the value. Note further that a guard is allowed to modify the value that is passed to it (e.g. to clamp it to a certain range). Task-number: QTBUG-85032 Change-Id: I3551e4357fe5780fb75da80bf8be208ec152dc2a Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>
This commit is contained in:
Fabian Kosmale
parent
6a24ac7c4e
commit
e18a060c03
@ -95,7 +95,8 @@ QPropertyBase::~QPropertyBase()
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QUntypedPropertyBinding QPropertyBase::setBinding(const QUntypedPropertyBinding &binding,
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void *propertyDataPtr,
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void *staticObserver,
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void (*staticObserverCallback)(void*, void*))
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void (*staticObserverCallback)(void*, void*),
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bool (*guardCallback)(void *, void*))
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{
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QPropertyBindingPrivatePtr oldBinding;
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QPropertyBindingPrivatePtr newBinding = binding.d;
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@ -122,7 +123,7 @@ QUntypedPropertyBinding QPropertyBase::setBinding(const QUntypedPropertyBinding
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newBinding->setProperty(propertyDataPtr);
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if (observer)
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newBinding->prependObserver(observer);
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newBinding->setStaticObserver(staticObserver, staticObserverCallback);
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newBinding->setStaticObserver(staticObserver, staticObserverCallback, guardCallback);
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} else if (observer) {
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d.setObservers(observer.ptr);
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} else {
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@ -85,7 +85,7 @@ struct Q_CORE_EXPORT QPropertyBindingSourceLocation
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template <typename Functor> class QPropertyChangeHandler;
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template <typename T> class QProperty;
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template <typename T, auto callbackMember> class QNotifiedProperty;
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template <typename T, auto callbackMember, auto guardCallback> class QNotifiedProperty;
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class QPropertyBindingErrorPrivate;
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@ -179,8 +179,8 @@ public:
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: QUntypedPropertyBinding(property.d.priv.binding())
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{}
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template<auto notifier>
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QPropertyBinding(const QNotifiedProperty<PropertyType, notifier> &property)
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template<auto notifier, auto guard>
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QPropertyBinding(const QNotifiedProperty<PropertyType, notifier, guard> &property)
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: QUntypedPropertyBinding(property.d.priv.binding())
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{}
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@ -382,13 +382,36 @@ namespace detail {
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struct ExtractClassFromFunctionPointer<T C::*> { using Class = C; };
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}
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template <typename T, auto Callback>
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template <typename T, auto Callback, auto ValueGuard=nullptr>
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class QNotifiedProperty
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{
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public:
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using value_type = T;
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using Class = typename detail::ExtractClassFromFunctionPointer<decltype(Callback)>::Class;
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static_assert(std::is_invocable_v<decltype(Callback), Class, T> || std::is_invocable_v<decltype(Callback), Class>);
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private:
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static bool constexpr ValueGuardModifiesArgument = std::is_invocable_r_v<bool, decltype(ValueGuard), Class, T&>;
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static bool constexpr CallbackAcceptsOldValue = std::is_invocable_v<decltype(Callback), Class, T>;
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static bool constexpr HasValueGuard = !std::is_same_v<decltype(ValueGuard), std::nullptr_t>;
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public:
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static_assert(CallbackAcceptsOldValue || std::is_invocable_v<decltype(Callback), Class>);
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static_assert(
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std::is_invocable_r_v<bool, decltype(ValueGuard), Class, T> ||
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ValueGuardModifiesArgument ||
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!HasValueGuard,
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"Guard has wrong signature");
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private:
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// type erased guard functions, casts its arguments to the correct types
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static constexpr bool (*GuardTEHelper)(void *, void*) = [](void *o, void *newValue){
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if constexpr (HasValueGuard) { // Guard->* is invalid if Guard == nullptr
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return (reinterpret_cast<Class *>(o)->*(ValueGuard))(*static_cast<T *>(newValue));
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} else {
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Q_UNUSED(o); // some compilers complain about unused variables
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Q_UNUSED(newValue);
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return true;
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}
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};
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static constexpr bool(*GuardTE)(void *, void*) = HasValueGuard ? GuardTEHelper : nullptr;
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public:
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QNotifiedProperty() = default;
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@ -428,46 +451,56 @@ public:
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return value();
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}
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void setValue(Class *owner, T &&newValue)
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template<typename S>
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auto setValue(Class *owner, S &&newValue) -> std::enable_if_t<!ValueGuardModifiesArgument && std::is_same_v<S, T>, void>
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{
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if constexpr(std::is_invocable_v<decltype(Callback), Class>) {
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if (d.setValueAndReturnTrueIfChanged(std::move(newValue)))
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notify(owner);
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} else {
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if constexpr (HasValueGuard) {
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if (!(owner->*ValueGuard)(newValue))
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return;
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}
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if constexpr (CallbackAcceptsOldValue) {
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T oldValue = value(); // TODO: kind of pointless if there was no change
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if (d.setValueAndReturnTrueIfChanged(std::move(newValue)))
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notify(owner, &oldValue);
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} else {
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if (d.setValueAndReturnTrueIfChanged(std::move(newValue)))
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notify(owner);
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}
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d.priv.removeBinding();
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}
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void setValue(Class *owner, const T &newValue)
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void setValue(Class *owner, std::conditional_t<ValueGuardModifiesArgument, T, const T &> newValue)
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{
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if constexpr(std::is_invocable_v<decltype(Callback), Class>) {
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if (d.setValueAndReturnTrueIfChanged(newValue))
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notify(owner);
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} else {
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if constexpr (HasValueGuard) {
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if (!(owner->*ValueGuard)(newValue))
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return;
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}
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if constexpr (CallbackAcceptsOldValue) {
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// When newValue is T, we move it, if it's const T& it stays const T& and won't get moved
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T oldValue = value();
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if (d.setValueAndReturnTrueIfChanged(newValue))
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if (d.setValueAndReturnTrueIfChanged(std::move(newValue)))
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notify(owner, &oldValue);
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} else {
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if (d.setValueAndReturnTrueIfChanged(std::move(newValue)))
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notify(owner);
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}
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d.priv.removeBinding();
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}
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QPropertyBinding<T> setBinding(Class *owner, const QPropertyBinding<T> &newBinding)
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{
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if constexpr(std::is_invocable_v<decltype(Callback), Class>) {
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QPropertyBinding<T> oldBinding(d.priv.setBinding(newBinding, &d, owner, [](void *o) {
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(reinterpret_cast<Class *>(o)->*Callback)();
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}));
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notify(owner);
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if constexpr (CallbackAcceptsOldValue) {
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T oldValue = value();
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QPropertyBinding<T> oldBinding(d.priv.setBinding(newBinding, &d, owner, [](void *o, void *oldVal) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldVal));
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}, GuardTE));
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notify(owner, &oldValue);
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return oldBinding;
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} else {
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T oldValue = value();
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QPropertyBinding<T> oldBinding(d.priv.setBinding(newBinding, &d, owner, [](void *o, void *oldValue) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldValue));
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}));
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notify(owner, &oldValue);
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QPropertyBinding<T> oldBinding(d.priv.setBinding(newBinding, &d, owner, [](void *o, void *) {
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(reinterpret_cast<Class *>(o)->*Callback)();
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}, GuardTE));
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notify(owner);
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return oldBinding;
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}
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}
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@ -475,18 +508,18 @@ public:
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QPropertyBinding<T> setBinding(Class *owner, QPropertyBinding<T> &&newBinding)
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{
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QPropertyBinding<T> b(std::move(newBinding));
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if constexpr(std::is_invocable_v<decltype(Callback), Class>) {
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QPropertyBinding<T> oldBinding(d.priv.setBinding(b, &d, owner, [](void *o, void *) {
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(reinterpret_cast<Class *>(o)->*Callback)();
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}));
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notify(owner);
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if constexpr (CallbackAcceptsOldValue) {
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T oldValue = value();
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QPropertyBinding<T> oldBinding(d.priv.setBinding(b, &d, owner, [](void *o, void *oldVal) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldVal));
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}, GuardTE));
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notify(owner, &oldValue);
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return oldBinding;
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} else {
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T oldValue = value();
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QPropertyBinding<T> oldBinding(d.priv.setBinding(b, &d, owner, [](void *o, void *oldValue) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldValue));
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}));
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notify(owner, &oldValue);
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QPropertyBinding<T> oldBinding(d.priv.setBinding(b, &d, owner, [](void *o, void *) {
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(reinterpret_cast<Class *>(o)->*Callback)();
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}, GuardTE));
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notify(owner);
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return oldBinding;
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}
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}
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@ -495,17 +528,17 @@ public:
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{
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if (newBinding.valueMetaType().id() != qMetaTypeId<T>())
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return false;
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if constexpr(std::is_invocable_v<decltype(Callback), Class>) {
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if constexpr (CallbackAcceptsOldValue) {
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T oldValue = value();
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d.priv.setBinding(newBinding, &d, owner, [](void *o, void *oldVal) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldVal));
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}, GuardTE);
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notify(owner, &oldValue);
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} else {
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d.priv.setBinding(newBinding, &d, owner, [](void *o, void *) {
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(reinterpret_cast<Class *>(o)->*Callback)();
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});
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}, GuardTE);
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notify(owner);
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} else {
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T oldValue = value();
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d.priv.setBinding(newBinding, &d, owner, [](void *o, void *oldValue) {
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(reinterpret_cast<Class *>(o)->*Callback)(*reinterpret_cast<T *>(oldValue));
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});
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notify(owner, &oldValue);
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}
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return true;
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}
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@ -544,10 +577,12 @@ private:
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void notify(Class *owner, T *oldValue=nullptr)
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{
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d.priv.notifyObservers(&d);
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if constexpr(std::is_invocable_v<decltype(Callback), Class>)
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if constexpr (std::is_invocable_v<decltype(Callback), Class>) {
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Q_UNUSED(oldValue);
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(owner->*Callback)();
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else
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} else {
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(owner->*Callback)(*oldValue);
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}
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}
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Q_DISABLE_COPY_MOVE(QNotifiedProperty)
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@ -581,8 +616,8 @@ public:
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void setSource(const QProperty<PropertyType> &property)
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{ setSource(property.d.priv); }
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template <typename PropertyType, auto notifier>
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void setSource(const QNotifiedProperty<PropertyType, notifier> &property)
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template <typename PropertyType, auto notifier, auto guard>
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void setSource(const QNotifiedProperty<PropertyType, notifier, guard> &property)
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{ setSource(property.d.priv); }
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protected:
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@ -642,8 +677,8 @@ public:
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setSource(property);
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}
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template <typename PropertyType, typename Class, void(Class::*Callback)()>
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QPropertyChangeHandler(const QNotifiedProperty<PropertyType, Callback> &property, Functor handler)
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template <typename PropertyType, auto Callback, auto Guard>
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QPropertyChangeHandler(const QNotifiedProperty<PropertyType, Callback, Guard> &property, Functor handler)
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: QPropertyObserver([](QPropertyObserver *self, void *) {
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auto This = static_cast<QPropertyChangeHandler<Functor>*>(self);
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This->m_handler();
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@ -675,9 +710,9 @@ QPropertyChangeHandler<Functor> QProperty<T>::subscribe(Functor f)
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return onValueChanged(f);
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}
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template <typename T, auto Callback>
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template <typename T, auto Callback, auto ValueGuard>
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template<typename Functor>
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QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback>::onValueChanged(Functor f)
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QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback, ValueGuard>::onValueChanged(Functor f)
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{
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#if defined(__cpp_lib_is_invocable) && (__cpp_lib_is_invocable >= 201703L)
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static_assert(std::is_invocable_v<Functor>, "Functor callback must be callable without any parameters");
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@ -685,9 +720,9 @@ QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback>::onValueChanged(F
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return QPropertyChangeHandler<Functor>(*this, f);
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}
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template <typename T, auto Callback>
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template <typename T, auto Callback, auto ValueGuard>
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template<typename Functor>
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QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback>::subscribe(Functor f)
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QPropertyChangeHandler<Functor> QNotifiedProperty<T, Callback, ValueGuard>::subscribe(Functor f)
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{
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#if defined(__cpp_lib_is_invocable) && (__cpp_lib_is_invocable >= 201703L)
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static_assert(std::is_invocable_v<Functor>, "Functor callback must be callable without any parameters");
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@ -111,7 +111,10 @@ bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged()
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bool newValue = false;
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evalError = evaluationFunction(metaType, &newValue);
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if (evalError.type() == QPropertyBindingError::NoError) {
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if (propertyPtr->extraBit() != newValue) {
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bool updateAllowed = true;
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if (hasStaticObserver && staticGuardCallback)
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updateAllowed = staticGuardCallback(staticObserver, &newValue);
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if (updateAllowed && propertyPtr->extraBit() != newValue) {
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propertyPtr->setExtraBit(newValue);
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changed = true;
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}
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@ -121,7 +124,10 @@ bool QPropertyBindingPrivate::evaluateIfDirtyAndReturnTrueIfValueChanged()
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evalError = evaluationFunction(metaType, resultVariant.data());
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if (evalError.type() == QPropertyBindingError::NoError) {
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int compareResult = 0;
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if (!QMetaType::compare(propertyDataPtr, resultVariant.constData(), metaType.id(), &compareResult) || compareResult != 0) {
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bool updateAllowed = true;
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if (hasStaticObserver && staticGuardCallback)
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updateAllowed = staticGuardCallback(staticObserver, resultVariant.data());
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if (updateAllowed && (!QMetaType::compare(propertyDataPtr, resultVariant.constData(), metaType.id(), &compareResult) || compareResult != 0)) {
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changed = true;
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metaType.destruct(propertyDataPtr);
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metaType.construct(propertyDataPtr, resultVariant.constData());
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@ -81,6 +81,7 @@ private:
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struct {
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void *staticObserver;
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void (*staticObserverCallback)(void*, void*);
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bool (*staticGuardCallback)(void*, void*);
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};
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};
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QScopedPointer<std::vector<QPropertyObserver>> heapObservers;
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@ -107,7 +108,7 @@ public:
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void setDirty(bool d) { dirty = d; }
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void setProperty(void *propertyPtr) { propertyDataPtr = propertyPtr; }
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void setStaticObserver(void *observer, void (*callback)(void*, void*))
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void setStaticObserver(void *observer, void (*callback)(void*, void*), bool (*guardCallback)(void *, void*))
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{
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if (observer) {
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if (!hasStaticObserver) {
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@ -123,6 +124,7 @@ public:
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hasStaticObserver = true;
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staticObserver = observer;
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staticObserverCallback = callback;
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staticGuardCallback = guardCallback;
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} else if (hasStaticObserver) {
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hasStaticObserver = false;
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new (&inlineDependencyObservers) ObserverArray();
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@ -84,7 +84,8 @@ public:
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QUntypedPropertyBinding setBinding(const QUntypedPropertyBinding &newBinding,
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void *propertyDataPtr, void *staticObserver = nullptr,
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void (*staticObserverCallback)(void *, void *) = nullptr);
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void (*staticObserverCallback)(void *, void *) = nullptr,
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bool (*guardCallback)(void *, void *) = nullptr);
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QPropertyBindingPrivate *binding();
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void evaluateIfDirty();
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@ -73,6 +73,7 @@ private slots:
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void propertyAlias();
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void notifiedProperty();
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void notifiedPropertyWithOldValueCallback();
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void notifiedPropertyWithGuard();
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};
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void tst_QProperty::functorBinding()
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@ -876,6 +877,136 @@ void tst_QProperty::notifiedPropertyWithOldValueCallback()
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QCOMPARE(instance.property.value(), 4);
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}
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struct ClassWithNotifiedPropertyWithGuard
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{
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using This = ClassWithNotifiedPropertyWithGuard;
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QVector<int> recordedValues;
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void callback() { recordedValues << property.value(); }
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void callback2() { recordedValues << property2.value(); }
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void callback3() {}
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bool trivialGuard(int ) {return true;}
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bool reject42(int newValue) {return newValue != 42;}
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bool bound(int &newValue) { newValue = qBound<int>(0, newValue, 100); return true; }
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QNotifiedProperty<int, &This::callback, &This::trivialGuard> property;
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QNotifiedProperty<int, &This::callback2, &This::reject42> property2;
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QNotifiedProperty<int, &This::callback3, &This::bound> property3;
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};
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void tst_QProperty::notifiedPropertyWithGuard()
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{
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{
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// property with guard that returns always true is the same as using no guard
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ClassWithNotifiedPropertyWithGuard instance;
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std::array<QProperty<int>, 5> otherProperties = {
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QProperty<int>([&]() { return instance.property + 1; }),
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QProperty<int>([&]() { return instance.property + 2; }),
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QProperty<int>([&]() { return instance.property + 3; }),
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QProperty<int>([&]() { return instance.property + 4; }),
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QProperty<int>([&]() { return instance.property + 5; }),
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};
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auto check = [&] {
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const int val = instance.property.value();
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for (int i = 0; i < int(otherProperties.size()); ++i)
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QCOMPARE(otherProperties[i].value(), val + i + 1);
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};
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QVERIFY(instance.recordedValues.isEmpty());
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check();
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instance.property.setValue(&instance, 42);
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QCOMPARE(instance.recordedValues.count(), 1);
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QCOMPARE(instance.recordedValues.at(0), 42);
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instance.recordedValues.clear();
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check();
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instance.property.setValue(&instance, 42);
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QVERIFY(instance.recordedValues.isEmpty());
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check();
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int subscribedCount = 0;
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QProperty<int> injectedValue(100);
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instance.property.setBinding(&instance, [&injectedValue]() { return injectedValue.value(); });
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auto subscriber = [&] { ++subscribedCount; };
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std::array<QPropertyChangeHandler<decltype (subscriber)>, 10> subscribers = {
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
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instance.property.subscribe(subscriber),
|
||||
instance.property.subscribe(subscriber),
|
||||
instance.property.subscribe(subscriber),
|
||||
instance.property.subscribe(subscriber)
|
||||
};
|
||||
|
||||
QCOMPARE(subscribedCount, 10);
|
||||
subscribedCount = 0;
|
||||
|
||||
QCOMPARE(instance.property.value(), 100);
|
||||
QCOMPARE(instance.recordedValues.count(), 1);
|
||||
QCOMPARE(instance.recordedValues.at(0), 100);
|
||||
instance.recordedValues.clear();
|
||||
check();
|
||||
QCOMPARE(subscribedCount, 0);
|
||||
|
||||
injectedValue = 200;
|
||||
QCOMPARE(instance.property.value(), 200);
|
||||
QCOMPARE(instance.recordedValues.count(), 1);
|
||||
QCOMPARE(instance.recordedValues.at(0), 200);
|
||||
instance.recordedValues.clear();
|
||||
check();
|
||||
QCOMPARE(subscribedCount, 10);
|
||||
subscribedCount = 0;
|
||||
|
||||
injectedValue = 400;
|
||||
QCOMPARE(instance.property.value(), 400);
|
||||
QCOMPARE(instance.recordedValues.count(), 1);
|
||||
QCOMPARE(instance.recordedValues.at(0), 400);
|
||||
instance.recordedValues.clear();
|
||||
check();
|
||||
QCOMPARE(subscribedCount, 10);
|
||||
}
|
||||
|
||||
{
|
||||
// Values can be rejected
|
||||
ClassWithNotifiedPropertyWithGuard instance2;
|
||||
|
||||
instance2.property2.setValue(&instance2, 1);
|
||||
instance2.property2.setBinding(&instance2, [](){return 42;});
|
||||
instance2.property2.setValue(&instance2, 2);
|
||||
instance2.property2.setBinding(&instance2, [](){return 3;});
|
||||
instance2.property2.setValue(&instance2, 42);
|
||||
// Note that we get 1 twice
|
||||
// This is an unfortunate result of the lazyness used for bindings
|
||||
// When we call setBinding, the binding does not get evaluated, but we
|
||||
// call the callback in notify; the callback will in our case query the
|
||||
// properties' value. At that point we then evaluate the binding, and
|
||||
// notice that the value is in fact disallowed. Thus we return the old
|
||||
// value.
|
||||
QVector<int> expected {1, 1, 2, 3};
|
||||
QCOMPARE(instance2.recordedValues, expected);
|
||||
}
|
||||
|
||||
{
|
||||
// guard can modify incoming values
|
||||
ClassWithNotifiedPropertyWithGuard instance3;
|
||||
instance3.property3.setValue(&instance3, 5);
|
||||
int i1 = 5;
|
||||
QCOMPARE(instance3.property3.value(), i1);
|
||||
instance3.property3.setBinding(&instance3, [](){return 255;});
|
||||
QCOMPARE(instance3.property3.value(), 100);
|
||||
const int i2 = -1;
|
||||
instance3.property3.setValue(&instance3, i2);
|
||||
QCOMPARE(instance3.property3.value(), 0);
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
QTEST_MAIN(tst_QProperty);
|
||||
|
||||
#include "tst_qproperty.moc"
|
||||
|
||||
Loading…
Reference in New Issue
Block a user