qproperty_p.h

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// Copyright (C) 2022 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default
 
#ifndef QPROPERTY_P_H
#define QPROPERTY_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists for the convenience
// of a number of Qt sources files.  This header file may change from
// version to version without notice, or even be removed.
//
// We mean it.
//
 
#include <private/qglobal_p.h>
#include <qproperty.h>
 
#include <qmetaobject.h>
#include <qscopedvaluerollback.h>
#include <qvariant.h>
#include <vector>
#include <QtCore/QVarLengthArray>
 
#include <memory>
 
QT_BEGIN_NAMESPACE
 
namespace QtPrivate {
    Q_CORE_EXPORT bool isAnyBindingEvaluating();
    struct QBindingStatusAccessToken {};
 
    namespace BindableWarnings {
    Q_CORE_EXPORT void printSignalArgumentsWithCustomGetter();
    }
}
 
 
/*!
    \internal
    Similar to \c QPropertyBindingPrivatePtr, but stores a
    \c QPropertyObserver * linking to the QPropertyBindingPrivate*
    instead of the QPropertyBindingPrivate* itself
 */
struct QBindingObserverPtr
{
private:
    QPropertyObserver *d = nullptr;
public:
    QBindingObserverPtr() = default;
    Q_DISABLE_COPY(QBindingObserverPtr)
    void swap(QBindingObserverPtr &other) noexcept
    { qt_ptr_swap(d, other.d); }
    QBindingObserverPtr(QBindingObserverPtr &&other) noexcept : d(std::exchange(other.d, nullptr)) {}
    QT_MOVE_ASSIGNMENT_OPERATOR_IMPL_VIA_MOVE_AND_SWAP(QBindingObserverPtr)
 
 
    inline QBindingObserverPtr(QPropertyObserver *observer) noexcept;
    inline ~QBindingObserverPtr();
    inline QPropertyBindingPrivate *binding() const noexcept;
    inline QPropertyObserver *operator ->();
};
 
using PendingBindingObserverList = QVarLengthArray<QPropertyBindingPrivatePtr>;
 
// Keep all classes related to QProperty in one compilation unit. Performance of this code is crucial and
// we need to allow the compiler to inline where it makes sense.
 
// This is a helper "namespace"
struct QPropertyBindingDataPointer
{
    const QtPrivate::QPropertyBindingData *ptr = nullptr;
 
    QPropertyBindingPrivate *binding() const
    {
        return ptr->binding();
    }
 
    void setObservers(QPropertyObserver *observer)
    {
        auto &d = ptr->d_ref();
        observer->prev = reinterpret_cast<QPropertyObserver**>(&d);
        d = reinterpret_cast<quintptr>(observer);
    }
    static void fixupAfterMove(QtPrivate::QPropertyBindingData *ptr);
    Q_ALWAYS_INLINE void addObserver(QPropertyObserver *observer);
    inline void setFirstObserver(QPropertyObserver *observer);
    inline QPropertyObserverPointer firstObserver() const;
    static QPropertyProxyBindingData *proxyData(QtPrivate::QPropertyBindingData *ptr);
 
    inline int observerCount() const;
 
    template <typename T>
    static QPropertyBindingDataPointer get(QProperty<T> &property)
    {
        return QPropertyBindingDataPointer{&property.bindingData()};
    }
};
 
struct QPropertyObserverNodeProtector
{
    Q_DISABLE_COPY_MOVE(QPropertyObserverNodeProtector)
 
    QPropertyObserverBase m_placeHolder;
    Q_NODISCARD_CTOR
    QPropertyObserverNodeProtector(QPropertyObserver *observer)
    {
        // insert m_placeholder after observer into the linked list
        QPropertyObserver *next = observer->next.data();
        m_placeHolder.next = next;
        observer->next = static_cast<QPropertyObserver *>(&m_placeHolder);
        if (next)
            next->prev = &m_placeHolder.next;
        m_placeHolder.prev = &observer->next;
        m_placeHolder.next.setTag(QPropertyObserver::ObserverIsPlaceholder);
    }
 
    QPropertyObserver *next() const { return m_placeHolder.next.data(); }
 
    ~QPropertyObserverNodeProtector();
};
 
// This is a helper "namespace"
struct QPropertyObserverPointer
{
    QPropertyObserver *ptr = nullptr;
 
    void unlink()
    {
        unlink_common();
#if QT_DEPRECATED_SINCE(6, 6)
        QT_WARNING_PUSH QT_WARNING_DISABLE_DEPRECATED
        if (ptr->next.tag() == QPropertyObserver::ObserverIsAlias)
            ptr->aliasData = nullptr;
        QT_WARNING_POP
#endif
    }
 
    void unlink_fast()
    {
#if QT_DEPRECATED_SINCE(6, 6)
        QT_WARNING_PUSH QT_WARNING_DISABLE_DEPRECATED
        Q_ASSERT(ptr->next.tag() != QPropertyObserver::ObserverIsAlias);
        QT_WARNING_POP
#endif
        unlink_common();
    }
 
    void setBindingToNotify(QPropertyBindingPrivate *binding)
    {
        Q_ASSERT(ptr->next.tag() != QPropertyObserver::ObserverIsPlaceholder);
        ptr->binding = binding;
        ptr->next.setTag(QPropertyObserver::ObserverNotifiesBinding);
    }
 
    void setBindingToNotify_unsafe(QPropertyBindingPrivate *binding);
    void setChangeHandler(QPropertyObserver::ChangeHandler changeHandler);
 
    enum class Notify {Everything, OnlyChangeHandlers};
 
    void notify(QUntypedPropertyData *propertyDataPtr);
#ifndef QT_NO_DEBUG
    void noSelfDependencies(QPropertyBindingPrivate *binding);
#else
    void noSelfDependencies(QPropertyBindingPrivate *) {}
#endif
    void evaluateBindings(PendingBindingObserverList &bindingObservers, QBindingStatus *status);
    void observeProperty(QPropertyBindingDataPointer property);
 
    explicit operator bool() const { return ptr != nullptr; }
 
    QPropertyObserverPointer nextObserver() const { return {ptr->next.data()}; }
 
    QPropertyBindingPrivate *binding() const
    {
        Q_ASSERT(ptr->next.tag() == QPropertyObserver::ObserverNotifiesBinding);
        return ptr->binding;
    }
 
private:
    void unlink_common()
    {
        if (ptr->next)
            ptr->next->prev = ptr->prev;
        if (ptr->prev)
            ptr->prev.setPointer(ptr->next.data());
        ptr->next = nullptr;
        ptr->prev.clear();
    }
};
 
class QPropertyBindingErrorPrivate : public QSharedData
{
public:
    QPropertyBindingError::Type type = QPropertyBindingError::NoError;
    QString description;
};
 
namespace QtPrivate {
 
struct BindingEvaluationState
{
    BindingEvaluationState(QPropertyBindingPrivate *binding, QBindingStatus *status);
    ~BindingEvaluationState()
    {
        *currentState = previousState;
    }
 
    QPropertyBindingPrivate *binding;
    BindingEvaluationState *previousState = nullptr;
    BindingEvaluationState **currentState = nullptr;
    QVarLengthArray<const QPropertyBindingData *, 8> alreadyCaptureProperties;
};
 
/*!
 * \internal
 * CompatPropertySafePoint needs to be constructed before the setter of
 * a QObjectCompatProperty runs. It prevents spurious binding dependencies
 * caused by reads of properties inside the compat property setter.
 * Moreover, it ensures that we don't destroy bindings when using operator=
 */
struct CompatPropertySafePoint
{
    Q_CORE_EXPORT CompatPropertySafePoint(QBindingStatus *status, QUntypedPropertyData *property);
    ~CompatPropertySafePoint()
    {
        *currentState = previousState;
        *currentlyEvaluatingBindingList = bindingState;
    }
    QUntypedPropertyData *property;
    CompatPropertySafePoint *previousState = nullptr;
    CompatPropertySafePoint **currentState = nullptr;
    QtPrivate::BindingEvaluationState **currentlyEvaluatingBindingList = nullptr;
    QtPrivate::BindingEvaluationState *bindingState = nullptr;
};
 
/*!
 * \internal
 * While the regular QProperty notification for a compat property runs we
 * don't want to have any currentCompatProperty set. This would be a _different_
 * one than the one we are current evaluating. Therefore it's misleading and
 * prevents the registering of actual dependencies.
 */
struct CurrentCompatPropertyThief
{
    Q_DISABLE_COPY_MOVE(CurrentCompatPropertyThief)
    QScopedValueRollback<CompatPropertySafePoint *> m_guard;
public:
    Q_NODISCARD_CTOR
    CurrentCompatPropertyThief(QBindingStatus *status)
        : m_guard(status->currentCompatProperty, nullptr)
    {
    }
};
 
}
 
class Q_CORE_EXPORT QPropertyBindingPrivate : public QtPrivate::RefCounted
{
private:
    friend struct QPropertyBindingDataPointer;
    friend class QPropertyBindingPrivatePtr;
 
    using ObserverArray = std::array<QPropertyObserver, 4>;
 
private:
 
    // used to detect binding loops for lazy evaluated properties
    bool updating = false;
    bool hasStaticObserver = false;
    bool pendingNotify = false;
    bool hasBindingWrapper:1;
    // used to detect binding loops for eagerly evaluated properties
    bool isQQmlPropertyBinding:1;
    /* a sticky binding does not get removed in removeBinding
       this is used to support QQmlPropertyData::DontRemoveBinding
       in qtdeclarative
    */
    bool m_sticky:1;
 
    const QtPrivate::BindingFunctionVTable *vtable;
 
    union {
        QtPrivate::QPropertyObserverCallback staticObserverCallback = nullptr;
        QtPrivate::QPropertyBindingWrapper staticBindingWrapper;
    };
    ObserverArray inlineDependencyObservers; // for things we are observing
 
    QPropertyObserverPointer firstObserver; // list of observers observing us
    std::unique_ptr<std::vector<QPropertyObserver>> heapObservers; // for things we are observing
 
protected:
    QUntypedPropertyData *propertyDataPtr = nullptr;
 
    /* For bindings set up from C++, location stores where the binding was created in the C++ source
       For QQmlPropertyBinding that information does not make sense, and the location in the QML  file
       is stored somewhere else. To make efficient use of the space, we instead provide a scratch space
       for QQmlPropertyBinding (which stores further binding information there).
       Anything stored in the union must be trivially destructible.
       (checked in qproperty.cpp)
 
       The discriminator for this union is the isQQmlPropertyBinding flag above. It has nothing to
       do with custom vtables per se. Depending on what is stored in declarativeExtraData, you may
       want vtable support for it, but since declarativeExtraData is well inside
       QPropertyBindingPrivate it can be a regular vtable. In practice, QML bindings have custom
       vtables because they store additional data _outside_ QPropertyBindingPrivate.
    */
    using DeclarativeErrorCallback = void(*)(QPropertyBindingPrivate *);
    union {
        QPropertyBindingSourceLocation location;
        struct {
            std::byte declarativeExtraData[sizeof(QPropertyBindingSourceLocation) - sizeof(DeclarativeErrorCallback)];
            DeclarativeErrorCallback errorCallBack;
        };
    };
private:
    QPropertyBindingError m_error;
 
    QMetaType metaType;
 
public:
    static constexpr size_t getSizeEnsuringAlignment() {
        constexpr auto align = alignof (std::max_align_t) - 1;
        constexpr size_t sizeEnsuringAlignment = (sizeof(QPropertyBindingPrivate) + align) & ~align;
        static_assert (sizeEnsuringAlignment % alignof (std::max_align_t) == 0,
                   "Required for placement new'ing the function behind it.");
        return sizeEnsuringAlignment;
    }
 
    const QtPrivate::BindingFunctionVTable *bindingFunctionVTable() const { return vtable; }
 
    // public because the auto-tests access it, too.
    size_t dependencyObserverCount = 0;
 
    bool isUpdating() {return updating;}
    void setSticky(bool keep = true) {m_sticky = keep;}
    bool isSticky() {return m_sticky;}
    void scheduleNotify() {pendingNotify = true;}
 
    QPropertyBindingPrivate(QMetaType metaType, const QtPrivate::BindingFunctionVTable *vtable,
                            const QPropertyBindingSourceLocation &location, bool isQQmlPropertyBinding=false)
        : hasBindingWrapper(false)
        , isQQmlPropertyBinding(isQQmlPropertyBinding)
        , m_sticky(false)
        , vtable(vtable)
        , location(location)
        , metaType(metaType)
    {}
    ~QPropertyBindingPrivate();
 
 
    void setProperty(QUntypedPropertyData *propertyPtr) { propertyDataPtr = propertyPtr; }
    void setStaticObserver(QtPrivate::QPropertyObserverCallback callback, QtPrivate::QPropertyBindingWrapper bindingWrapper)
    {
        Q_ASSERT(!(callback && bindingWrapper));
        if (callback) {
            hasStaticObserver = true;
            hasBindingWrapper = false;
            staticObserverCallback = callback;
        } else if (bindingWrapper) {
            hasStaticObserver = false;
            hasBindingWrapper = true;
            staticBindingWrapper = bindingWrapper;
        } else {
            hasStaticObserver = false;
            hasBindingWrapper = false;
            staticObserverCallback = nullptr;
        }
    }
    void prependObserver(QPropertyObserverPointer observer)
    {
        observer.ptr->prev = const_cast<QPropertyObserver **>(&firstObserver.ptr);
        firstObserver = observer;
    }
 
    QPropertyObserverPointer takeObservers()
    {
        auto observers = firstObserver;
        firstObserver.ptr = nullptr;
        return observers;
    }
 
    void clearDependencyObservers();
 
    Q_ALWAYS_INLINE QPropertyObserverPointer allocateDependencyObserver() {
        if (dependencyObserverCount < inlineDependencyObservers.size()) {
            ++dependencyObserverCount;
            return {&inlineDependencyObservers[dependencyObserverCount - 1]};
        }
        return allocateDependencyObserver_slow();
    }
 
    QPropertyObserverPointer allocateDependencyObserver_slow();
 
    QPropertyBindingSourceLocation sourceLocation() const
    {
        if (!isQQmlPropertyBinding)
            return location;
        return []() {
            constexpr auto msg = "Custom location";
            QPropertyBindingSourceLocation result;
            result.fileName = msg;
            return result;
        }();
    }
    QPropertyBindingError bindingError() const { return m_error; }
    QMetaType valueMetaType() const { return metaType; }
 
    void unlinkAndDeref();
 
    bool evaluateRecursive(PendingBindingObserverList &bindingObservers, QBindingStatus *status = nullptr);
 
    Q_ALWAYS_INLINE bool evaluateRecursive_inline(PendingBindingObserverList &bindingObservers, QBindingStatus *status);
 
    void notifyNonRecursive(const PendingBindingObserverList &bindingObservers);
    enum NotificationState : bool { Delayed, Sent };
    NotificationState notifyNonRecursive();
 
    static QPropertyBindingPrivate *get(const QUntypedPropertyBinding &binding)
    { return static_cast<QPropertyBindingPrivate *>(binding.d.data()); }
    static QUntypedPropertyBinding makeUntyped(QPropertyBindingPrivate *d)
    { return QUntypedPropertyBinding(static_cast<void *>(d)); }
 
    void setError(QPropertyBindingError &&e)
    { m_error = std::move(e); }
 
    void detachFromProperty()
    {
        hasStaticObserver = false;
        hasBindingWrapper = false;
        propertyDataPtr = nullptr;
        clearDependencyObservers();
    }
 
    static QPropertyBindingPrivate *currentlyEvaluatingBinding();
 
    /* In some cases we want to run the vtable's dtor _in place_ of ~QPropertBindingPrivate() rather
       than in addition, in order to cater to special memory layouts with extra trailing fields. The
       vtable's size member acts as flag for this. We call this a "custom" vtable. Note that you
       could have a QML binding with a regular vtable, as well as a non-QML binding with custom
       vtable. In practice, QML bindings have custom vtables because they store additional data
       after QPropertyBindingPrivate.
     */
    bool hasCustomVTable() const
    {
        return vtable->size == 0;
    }
 
    /* Determines whether we have a regular source location or declarativeExtraData + errorCallback.
     * This has nothing to do with custom vtables per se.
     */
    bool isQmlBinding() const
    {
        return isQQmlPropertyBinding;
    }
 
    static void destroyAndFreeMemory(QPropertyBindingPrivate *priv) {
        if (priv->hasCustomVTable()) {
            // special hack for QQmlPropertyBinding which has a
            // different memory layout than normal QPropertyBindings
            priv->vtable->destroy(priv);
        } else{
            priv->~QPropertyBindingPrivate();
            delete[] reinterpret_cast<std::byte *>(priv);
        }
    }
};
 
inline void QPropertyBindingDataPointer::setFirstObserver(QPropertyObserver *observer)
{
    if (auto *b = binding()) {
        b->firstObserver.ptr = observer;
        return;
    }
    auto &d = ptr->d_ref();
    d = reinterpret_cast<quintptr>(observer);
}
 
inline void QPropertyBindingDataPointer::fixupAfterMove(QtPrivate::QPropertyBindingData *ptr)
{
    auto &d = ptr->d_ref();
    if (ptr->isNotificationDelayed()) {
        QPropertyProxyBindingData *proxy = ptr->proxyData();
        Q_ASSERT(proxy);
        proxy->originalBindingData = ptr;
    }
    // If QPropertyBindingData has been moved, and it has an observer
    // we have to adjust the firstObserver's prev pointer to point to
    // the moved to QPropertyBindingData's d_ptr
    if (d & QtPrivate::QPropertyBindingData::BindingBit)
        return; // nothing to do if the observer is stored in the binding
    if (auto observer = reinterpret_cast<QPropertyObserver *>(d))
        observer->prev = reinterpret_cast<QPropertyObserver **>(&d);
}
 
inline QPropertyObserverPointer QPropertyBindingDataPointer::firstObserver() const
{
    if (auto *b = binding())
        return b->firstObserver;
    return { reinterpret_cast<QPropertyObserver *>(ptr->d()) };
}
 
/*!
    \internal
    Returns the proxy data of \a ptr, or \c nullptr if \a ptr has no delayed notification
 */
inline QPropertyProxyBindingData *QPropertyBindingDataPointer::proxyData(QtPrivate::QPropertyBindingData *ptr)
{
    if (!ptr->isNotificationDelayed())
        return nullptr;
    return ptr->proxyData();
}
 
inline int QPropertyBindingDataPointer::observerCount() const
{
    int count = 0;
    for (auto observer = firstObserver(); observer; observer = observer.nextObserver())
        ++count;
    return count;
}
 
namespace QtPrivate {
    Q_CORE_EXPORT bool isPropertyInBindingWrapper(const QUntypedPropertyData *property);
    void Q_CORE_EXPORT initBindingStatusThreadId();
}
 
template<typename Class, typename T, auto Offset, auto Setter, auto Signal = nullptr,
         auto Getter = nullptr>
class QObjectCompatProperty : public QPropertyData<T>
{
    template<typename Property, typename>
    friend class QtPrivate::QBindableInterfaceForProperty;
 
    using ThisType = QObjectCompatProperty<Class, T, Offset, Setter, Signal, Getter>;
    using SignalTakesValue = std::is_invocable<decltype(Signal), Class, T>;
    Class *owner()
    {
        char *that = reinterpret_cast<char *>(this);
        return reinterpret_cast<Class *>(that - QtPrivate::detail::getOffset(Offset));
    }
    const Class *owner() const
    {
        char *that = const_cast<char *>(reinterpret_cast<const char *>(this));
        return reinterpret_cast<Class *>(that - QtPrivate::detail::getOffset(Offset));
    }
 
    static bool bindingWrapper(QMetaType type, QUntypedPropertyData *dataPtr, QtPrivate::QPropertyBindingFunction binding)
    {
        auto *thisData = static_cast<ThisType *>(dataPtr);
        QBindingStorage *storage = qGetBindingStorage(thisData->owner());
        QPropertyData<T> copy(thisData->valueBypassingBindings());
        {
            QtPrivate::CurrentCompatPropertyThief thief(storage->bindingStatus);
            if (!binding.vtable->call(type, &copy, binding.functor))
                return false;
        }
        // ensure value and setValue know we're currently evaluating our binding
        QtPrivate::CompatPropertySafePoint guardThis(storage->bindingStatus, thisData);
        (thisData->owner()->*Setter)(copy.valueBypassingBindings());
        return true;
    }
    bool inBindingWrapper(const QBindingStorage *storage) const
    {
        return storage->bindingStatus && storage->bindingStatus->currentCompatProperty
            && QtPrivate::isPropertyInBindingWrapper(this);
    }
 
    inline static T getPropertyValue(const QUntypedPropertyData *d) {
        auto prop = static_cast<const ThisType *>(d);
        if constexpr (std::is_null_pointer_v<decltype(Getter)>)
            return prop->value();
        else
            return (prop->owner()->*Getter)();
    }
 
    inline static T getPropertyValueBypassingBindings(const QUntypedPropertyData *d) {
        auto prop = static_cast<const ThisType *>(d);
        if constexpr (std::is_null_pointer_v<decltype(Getter)>)
            return prop->valueBypassingBindings();
        else
            return (prop->owner()->*Getter)();
    }
 
    inline static void warnIfSignalWithArgumentAndCustomGetter()
    {
        if constexpr (!std::is_null_pointer_v<decltype(Signal)>
                      && SignalTakesValue::value
                      && !std::is_null_pointer_v<decltype(Getter)>) {
            QtPrivate::BindableWarnings::printSignalArgumentsWithCustomGetter();
        }
    }
 
public:
    using value_type = typename QPropertyData<T>::value_type;
    using parameter_type = typename QPropertyData<T>::parameter_type;
    using arrow_operator_result = typename QPropertyData<T>::arrow_operator_result;
 
    QObjectCompatProperty() { warnIfSignalWithArgumentAndCustomGetter(); }
    explicit QObjectCompatProperty(const T &initialValue) : QPropertyData<T>(initialValue)
    {
        warnIfSignalWithArgumentAndCustomGetter();
    }
    explicit QObjectCompatProperty(T &&initialValue) : QPropertyData<T>(std::move(initialValue))
    {
        warnIfSignalWithArgumentAndCustomGetter();
    }
 
    parameter_type value() const
    {
        const QBindingStorage *storage = qGetBindingStorage(owner());
        // make sure we don't register this binding as a dependency to itself
        if (storage->bindingStatus && storage->bindingStatus->currentlyEvaluatingBinding && !inBindingWrapper(storage))
            storage->registerDependency_helper(this);
        return this->val;
    }
 
    arrow_operator_result operator->() const
    {
        if constexpr (QTypeTraits::is_dereferenceable_v<T>) {
            return value();
        } else if constexpr (std::is_pointer_v<T>) {
            value();
            return this->val;
        } else {
            return;
        }
    }
 
    parameter_type operator*() const
    {
        return value();
    }
 
    operator parameter_type() const
    {
        return value();
    }
 
    void setValue(parameter_type t)
    {
        QBindingStorage *storage = qGetBindingStorage(owner());
        if (auto *bd = storage->bindingData(this)) {
            // make sure we don't remove the binding if called from the bindingWrapper
            if (bd->hasBinding() && !inBindingWrapper(storage))
                bd->removeBinding_helper();
        }
        this->val = t;
    }
 
    QObjectCompatProperty &operator=(parameter_type newValue)
    {
        setValue(newValue);
        return *this;
    }
 
    QPropertyBinding<T> setBinding(const QPropertyBinding<T> &newBinding)
    {
        QtPrivate::QPropertyBindingData *bd = qGetBindingStorage(owner())->bindingData(this, true);
        QUntypedPropertyBinding oldBinding(bd->setBinding(newBinding, this, nullptr, bindingWrapper));
        // notification is already handled in QPropertyBindingData::setBinding
        return static_cast<QPropertyBinding<T> &>(oldBinding);
    }
 
    bool setBinding(const QUntypedPropertyBinding &newBinding)
    {
        if (!newBinding.isNull() && newBinding.valueMetaType() != QMetaType::fromType<T>())
            return false;
        setBinding(static_cast<const QPropertyBinding<T> &>(newBinding));
        return true;
    }
 
#ifndef Q_QDOC
    template <typename Functor>
    QPropertyBinding<T> setBinding(Functor &&f,
                                   const QPropertyBindingSourceLocation &location = QT_PROPERTY_DEFAULT_BINDING_LOCATION,
                                   std::enable_if_t<std::is_invocable_v<Functor>> * = nullptr)
    {
        return setBinding(Qt::makePropertyBinding(std::forward<Functor>(f), location));
    }
#else
    template <typename Functor>
    QPropertyBinding<T> setBinding(Functor f);
#endif
 
    bool hasBinding() const {
        auto *bd = qGetBindingStorage(owner())->bindingData(this);
        return bd && bd->binding() != nullptr;
    }
 
    void removeBindingUnlessInWrapper()
    {
        QBindingStorage *storage = qGetBindingStorage(owner());
        if (auto *bd = storage->bindingData(this)) {
            // make sure we don't remove the binding if called from the bindingWrapper
            if (bd->hasBinding() && !inBindingWrapper(storage))
                bd->removeBinding_helper();
        }
    }
 
    void notify()
    {
        QBindingStorage *storage = qGetBindingStorage(owner());
        if (auto bd = storage->bindingData(this, false)) {
            // This partly duplicates QPropertyBindingData::notifyObservers because we want to
            // check for inBindingWrapper() after checking for isNotificationDelayed() and
            // firstObserver. This is because inBindingWrapper() is the most expensive check.
            if (!bd->isNotificationDelayed()) {
                QPropertyBindingDataPointer d{bd};
                if (QPropertyObserverPointer observer = d.firstObserver()) {
                    if (!inBindingWrapper(storage)) {
                        PendingBindingObserverList bindingObservers;
                        if (bd->notifyObserver_helper(this, storage, observer, bindingObservers)
                                == QtPrivate::QPropertyBindingData::Evaluated) {
                            // evaluateBindings() can trash the observers.
                            // It can also reallocate binding data pointer.
                            // So, we need to re-fetch here.
                            bd = storage->bindingData(this, false);
                            QPropertyBindingDataPointer dd{bd};
                            if (QPropertyObserverPointer obs = dd.firstObserver())
                                obs.notify(this);
                            for (auto&& bindingPtr: bindingObservers) {
                                auto *binding = static_cast<QPropertyBindingPrivate *>(bindingPtr.get());
                                binding->notifyNonRecursive();
                            }
                        }
                    }
                }
            }
        }
        if constexpr (!std::is_null_pointer_v<decltype(Signal)>) {
            if constexpr (SignalTakesValue::value)
                (owner()->*Signal)(getPropertyValueBypassingBindings(this));
            else
                (owner()->*Signal)();
        }
    }
 
    QPropertyBinding<T> binding() const
    {
        auto *bd = qGetBindingStorage(owner())->bindingData(this);
        QUntypedPropertyBinding binding = QPropertyBindingPrivate::makeUntyped(bd ? bd->binding() : nullptr);
        return static_cast<QPropertyBinding<T> &&>(binding);
    }
 
    QPropertyBinding<T> takeBinding()
    {
        return setBinding(QPropertyBinding<T>());
    }
 
    template<typename Functor>
    QPropertyChangeHandler<Functor> onValueChanged(Functor f)
    {
        static_assert(std::is_invocable_v<Functor>, "Functor callback must be callable without any parameters");
        return QPropertyChangeHandler<Functor>(*this, f);
    }
 
    template<typename Functor>
    QPropertyChangeHandler<Functor> subscribe(Functor f)
    {
        static_assert(std::is_invocable_v<Functor>, "Functor callback must be callable without any parameters");
        f();
        return onValueChanged(f);
    }
 
    template<typename Functor>
    QPropertyNotifier addNotifier(Functor f)
    {
        static_assert(std::is_invocable_v<Functor>, "Functor callback must be callable without any parameters");
        return QPropertyNotifier(*this, f);
    }
 
    QtPrivate::QPropertyBindingData &bindingData() const
    {
        auto *storage = const_cast<QBindingStorage *>(qGetBindingStorage(owner()));
        return *storage->bindingData(const_cast<QObjectCompatProperty *>(this), true);
    }
};
 
namespace QtPrivate {
template<typename Class, typename Ty, auto Offset, auto Setter, auto Signal, auto Getter>
class QBindableInterfaceForProperty<
        QObjectCompatProperty<Class, Ty, Offset, Setter, Signal, Getter>, std::void_t<Class>>
{
    using Property = QObjectCompatProperty<Class, Ty, Offset, Setter, Signal, Getter>;
    using T = typename Property::value_type;
public:
    static constexpr QBindableInterface iface = {
        [](const QUntypedPropertyData *d, void *value) -> void
        { *static_cast<T*>(value) = Property::getPropertyValue(d); },
        [](QUntypedPropertyData *d, const void *value) -> void
        {
            (static_cast<Property *>(d)->owner()->*Setter)(*static_cast<const T*>(value));
        },
        [](const QUntypedPropertyData *d) -> QUntypedPropertyBinding
        { return static_cast<const Property *>(d)->binding(); },
        [](QUntypedPropertyData *d, const QUntypedPropertyBinding &binding) -> QUntypedPropertyBinding
        { return static_cast<Property *>(d)->setBinding(static_cast<const QPropertyBinding<T> &>(binding)); },
        [](const QUntypedPropertyData *d, const QPropertyBindingSourceLocation &location) -> QUntypedPropertyBinding
        { return Qt::makePropertyBinding([d]() -> T { return Property::getPropertyValue(d); }, location); },
        [](const QUntypedPropertyData *d, QPropertyObserver *observer) -> void
        { observer->setSource(static_cast<const Property *>(d)->bindingData()); },
        []() { return QMetaType::fromType<T>(); }
    };
};
}
 
#define QT_OBJECT_COMPAT_PROPERTY_4(Class, Type, name,  setter)
    static constexpr size_t _qt_property_##name##_offset() {
        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
        return offsetof(Class, name);
        QT_WARNING_POP
    }
    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter> name;
 
#define QT_OBJECT_COMPAT_PROPERTY_5(Class, Type, name,  setter, signal)
    static constexpr size_t _qt_property_##name##_offset() {
        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
        return offsetof(Class, name);
        QT_WARNING_POP
    }
    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter, signal> name;
 
#define Q_OBJECT_COMPAT_PROPERTY(...)
    QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
    QT_OVERLOADED_MACRO(QT_OBJECT_COMPAT_PROPERTY, __VA_ARGS__)
    QT_WARNING_POP
 
#define QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS_5(Class, Type, name,  setter, value)
    static constexpr size_t _qt_property_##name##_offset() {
        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
        return offsetof(Class, name);
        QT_WARNING_POP
    }
    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter> name =
            QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter>(
                    value);
 
#define QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS_6(Class, Type, name, setter, signal, value)
    static constexpr size_t _qt_property_##name##_offset() {
        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
        return offsetof(Class, name);
        QT_WARNING_POP
    }
    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter, signal> name =
            QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter,
                                  signal>(value);
 
#define QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS_7(Class, Type, name, setter, signal, getter, value)
    static constexpr size_t _qt_property_##name##_offset() {
        QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
        return offsetof(Class, name);
        QT_WARNING_POP
    }
    QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter, signal, getter>
        name = QObjectCompatProperty<Class, Type, Class::_qt_property_##name##_offset, setter,
                                     signal, getter>(value);
 
#define Q_OBJECT_COMPAT_PROPERTY_WITH_ARGS(...)
    QT_WARNING_PUSH QT_WARNING_DISABLE_INVALID_OFFSETOF
    QT_OVERLOADED_MACRO(QT_OBJECT_COMPAT_PROPERTY_WITH_ARGS, __VA_ARGS__)
    QT_WARNING_POP
 
 
namespace QtPrivate {
Q_CORE_EXPORT BindingEvaluationState *suspendCurrentBindingStatus();
Q_CORE_EXPORT void restoreBindingStatus(BindingEvaluationState *status);
}
 
struct QUntypedBindablePrivate
{
    static QtPrivate::QBindableInterface const *getInterface(const QUntypedBindable &bindable)
    {
        return bindable.iface;
    }
 
    static QUntypedPropertyData *getPropertyData(const QUntypedBindable &bindable)
    {
        return bindable.data;
    }
};
 
inline bool QPropertyBindingPrivate::evaluateRecursive_inline(PendingBindingObserverList &bindingObservers, QBindingStatus *status)
{
    if (updating) {
        m_error = QPropertyBindingError(QPropertyBindingError::BindingLoop);
        if (isQQmlPropertyBinding)
            errorCallBack(this);
        return false;
    }
 
    /*
     * Evaluating the binding might lead to the binding being broken. This can
     * cause ref to reach zero at the end of the function.  However, the
     * updateGuard's destructor will then still trigger, trying to set the
     * updating bool to its old value
     * To prevent this, we create a QPropertyBindingPrivatePtr which ensures
     * that the object is still alive when updateGuard's dtor runs.
     */
    QPropertyBindingPrivatePtr keepAlive {this};
 
    QScopedValueRollback<bool> updateGuard(updating, true);
 
    QtPrivate::BindingEvaluationState evaluationFrame(this, status);
 
    auto bindingFunctor =  reinterpret_cast<std::byte *>(this) +
            QPropertyBindingPrivate::getSizeEnsuringAlignment();
    bool changed = false;
    if (hasBindingWrapper) {
        changed = staticBindingWrapper(metaType, propertyDataPtr,
                                       {vtable, bindingFunctor});
    } else {
        changed = vtable->call(metaType, propertyDataPtr, bindingFunctor);
    }
    // If there was a change, we must set pendingNotify.
    // If there was not, we must not clear it, as that only should happen in notifyRecursive
    pendingNotify = pendingNotify || changed;
    if (!changed || !firstObserver)
        return changed;
 
    firstObserver.noSelfDependencies(this);
    firstObserver.evaluateBindings(bindingObservers, status);
    return true;
}
 
/*!
    \internal
 
    Walks through the list of property observers, and calls any ChangeHandler
    found there.
    It doesn't do anything with bindings, which are only handled in
    QPropertyBindingPrivate::evaluateRecursive.
 */
inline void QPropertyObserverPointer::notify(QUntypedPropertyData *propertyDataPtr)
{
    auto observer = const_cast<QPropertyObserver*>(ptr);
    /*
     * The basic idea of the loop is as follows: We iterate over all observers in the linked list,
     * and execute the functionality corresponding to their tag.
     * However, complication arise due to the fact that the triggered operations might modify the list,
     * which includes deletion and move of the current and next nodes.
     * Therefore, we take a few safety precautions:
     * 1. Before executing any action which might modify the list, we insert a placeholder node after the current node.
     *    As that one is stack allocated and owned by us, we can rest assured that it is
     *    still there after the action has executed, and placeHolder->next points to the actual next node in the list.
     *    Note that taking next at the beginning of the loop does not work, as the executed action might either move
     *    or delete that node.
     * 2. After the triggered action has finished, we can use the next pointer in the placeholder node as a safe way to
     *    retrieve the next node.
     * 3. Some care needs to be taken to avoid infinite recursion with change handlers, so we add an extra test there, that
     *    checks whether we're already have the same change handler in our call stack. This can be done by checking whether
     *    the node after the current one is a placeholder node.
     */
    while (observer) {
        QPropertyObserver *next = observer->next.data();
        switch (QPropertyObserver::ObserverTag(observer->next.tag())) {
        case QPropertyObserver::ObserverNotifiesChangeHandler:
        {
            auto handlerToCall = observer->changeHandler;
            // prevent recursion
            if (next && next->next.tag() == QPropertyObserver::ObserverIsPlaceholder) {
                observer = next->next.data();
                continue;
            }
            // handlerToCall might modify the list
            QPropertyObserverNodeProtector protector(observer);
            handlerToCall(observer, propertyDataPtr);
            next = protector.next();
            break;
        }
        case QPropertyObserver::ObserverNotifiesBinding:
            break;
        case QPropertyObserver::ObserverIsPlaceholder:
            // recursion is already properly handled somewhere else
            break;
#if QT_DEPRECATED_SINCE(6, 6)
        QT_WARNING_PUSH QT_WARNING_DISABLE_DEPRECATED
        case QPropertyObserver::ObserverIsAlias:
            break;
        QT_WARNING_POP
#endif
        default: Q_UNREACHABLE();
        }
        observer = next;
    }
}
 
inline QPropertyObserverNodeProtector::~QPropertyObserverNodeProtector()
{
    QPropertyObserverPointer d{static_cast<QPropertyObserver *>(&m_placeHolder)};
    d.unlink_fast();
}
 
QBindingObserverPtr::QBindingObserverPtr(QPropertyObserver *observer) noexcept : d(observer)
{
    Q_ASSERT(d);
    QPropertyObserverPointer{d}.binding()->addRef();
}
 
QBindingObserverPtr::~QBindingObserverPtr()
{
    if (!d)
        return;
 
    QPropertyBindingPrivate *bindingPrivate = binding();
    if (!bindingPrivate->deref())
        QPropertyBindingPrivate::destroyAndFreeMemory(bindingPrivate);
}
 
QPropertyBindingPrivate *QBindingObserverPtr::binding() const noexcept { return QPropertyObserverPointer{d}.binding(); }
 
QPropertyObserver *QBindingObserverPtr::operator->() { return d; }
 
namespace QtPrivate {
class QPropertyAdaptorSlotObject : public QUntypedPropertyData, public QSlotObjectBase
{
    QPropertyBindingData bindingData_;
    QObject *obj;
    QMetaProperty metaProperty_;
 
#if QT_VERSION < QT_VERSION_CHECK(7, 0, 0)
    static void impl(int which, QSlotObjectBase *this_, QObject *r, void **a, bool *ret);
#else
    static void impl(QSlotObjectBase *this_, QObject *r, void **a, int which, bool *ret);
#endif
 
    QPropertyAdaptorSlotObject(QObject *o, const QMetaProperty& p);
 
public:
    static QPropertyAdaptorSlotObject *cast(QSlotObjectBase *ptr, int propertyIndex)
    {
        if (ptr->isImpl(&QPropertyAdaptorSlotObject::impl)) {
            auto p = static_cast<QPropertyAdaptorSlotObject *>(ptr);
            if (p->metaProperty_.propertyIndex() == propertyIndex)
                return p;
        }
        return nullptr;
    }
 
    inline const QPropertyBindingData &bindingData() const { return bindingData_; }
    inline QPropertyBindingData &bindingData() { return bindingData_; }
    inline QObject *object() const { return obj; }
    inline const QMetaProperty &metaProperty() const { return metaProperty_; }
 
    friend class QT_PREPEND_NAMESPACE(QUntypedBindable);
};
}
 
QT_END_NAMESPACE
 
#endif // QPROPERTY_P_H