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// Copyright (C) 2016 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
#ifndef QQMLGUARD_P_H
#define QQMLGUARD_P_H
//
// W A R N I N G
// -------------
//
// This file is not part of the Qt API. It exists for the convenience
// of qapplication_*.cpp, qwidget*.cpp and qfiledialog.cpp. This header
// file may change from version to version without notice, or even be removed.
//
// We mean it.
//
#include <private/qqmldata_p.h>
#include <private/qqmlglobal_p.h>
QT_BEGIN_NAMESPACE
class QQmlGuardImpl
{
public:
using ObjectDestroyedFn = void(*)(QQmlGuardImpl *);
inline QQmlGuardImpl();
inline QQmlGuardImpl(QObject *);
inline QQmlGuardImpl(const QQmlGuardImpl &);
protected:
inline ~QQmlGuardImpl();
public: // ### make so it can be private
QObject *o = nullptr;
QQmlGuardImpl *next = nullptr;
QQmlGuardImpl **prev = nullptr;
ObjectDestroyedFn objectDestroyed = nullptr;
inline void addGuard();
inline void remGuard();
inline void setObject(QObject *g);
bool isNull() const noexcept { return !o; }
};
class QObject;
template<class T>
class QQmlGuard : protected QQmlGuardImpl
{
friend class QQmlData;
public:
Q_NODISCARD_CTOR inline QQmlGuard();
Q_NODISCARD_CTOR inline QQmlGuard(ObjectDestroyedFn objectDestroyed, T *);
Q_NODISCARD_CTOR inline QQmlGuard(T *);
Q_NODISCARD_CTOR inline QQmlGuard(const QQmlGuard<T> &);
inline QQmlGuard<T> &operator=(const QQmlGuard<T> &o);
inline QQmlGuard<T> &operator=(T *);
T *object() const noexcept { return static_cast<T *>(o); }
void setObject(T *g) { QQmlGuardImpl::setObject(g); }
using QQmlGuardImpl::isNull;
T *operator->() const noexcept { return object(); }
T &operator*() const { return *object(); }
operator T *() const noexcept { return object(); }
T *data() const noexcept { return object(); }
};
/* used in QQmlStrongJSQObjectReference to indicate that the
* object has JS ownership
* We save it in objectDestroyFn to save space
* (implemented in qqmlengine.cpp)
*/
void Q_QML_EXPORT hasJsOwnershipIndicator(QQmlGuardImpl *);
template <typename T>
class QQmlStrongJSQObjectReference final : protected QQmlGuardImpl
{
public:
T *object() const noexcept { return static_cast<T *>(o); }
using QQmlGuardImpl::isNull;
T *operator->() const noexcept { return object(); }
T &operator*() const { return *object(); }
operator T *() const noexcept { return object(); }
T *data() const noexcept { return object(); }
void setObject(T *obj, QObject *parent) {
T *old = object();
if (obj == old)
return;
if (hasJsOwnership() && old && old->parent() == parent)
QQml_setParent_noEvent(old, nullptr);
QQmlGuardImpl::setObject(obj);
if (obj && !obj->parent() && !QQmlData::keepAliveDuringGarbageCollection(obj)) {
setJsOwnership(true);
QQml_setParent_noEvent(obj, parent);
} else {
setJsOwnership(false);
}
}
private:
bool hasJsOwnership() {
return objectDestroyed == hasJsOwnershipIndicator;
}
void setJsOwnership(bool itHasOwnership) {
objectDestroyed = itHasOwnership ? hasJsOwnershipIndicator : nullptr;
}
};
QT_END_NAMESPACE
Q_DECLARE_METATYPE(QQmlGuard<QObject>)
QT_BEGIN_NAMESPACE
QQmlGuardImpl::QQmlGuardImpl()
{
}
QQmlGuardImpl::QQmlGuardImpl(QObject *g)
: o(g)
{
if (o) addGuard();
}
/*
\internal
Copying a QQmlGuardImpl leaves the old one in the intrinsic linked list of guards.
The fresh copy does not contain the list pointer of the existing guard; instead
only the object and objectDestroyed pointers are copied, and if there is an object
we add the new guard to the object's list of guards.
*/
QQmlGuardImpl::QQmlGuardImpl(const QQmlGuardImpl &g)
: o(g.o), objectDestroyed(g.objectDestroyed)
{
if (o) addGuard();
}
QQmlGuardImpl::~QQmlGuardImpl()
{
if (prev) remGuard();
o = nullptr;
}
void QQmlGuardImpl::addGuard()
{
Q_ASSERT(!prev);
if (QObjectPrivate::get(o)->wasDeleted)
return;
QQmlData *data = QQmlData::get(o, true);
next = data->guards;
if (next) next->prev = &next;
data->guards = this;
prev = &data->guards;
}
void QQmlGuardImpl::remGuard()
{
Q_ASSERT(prev);
if (next) next->prev = prev;
*prev = next;
next = nullptr;
prev = nullptr;
}
template<class T>
QQmlGuard<T>::QQmlGuard()
{
}
template<class T>
QQmlGuard<T>::QQmlGuard(ObjectDestroyedFn objDestroyed, T *obj)
: QQmlGuardImpl(obj)
{
objectDestroyed = objDestroyed;
}
template<class T>
QQmlGuard<T>::QQmlGuard(T *g)
: QQmlGuardImpl(g)
{
}
template<class T>
QQmlGuard<T>::QQmlGuard(const QQmlGuard<T> &g)
: QQmlGuardImpl(g)
{
}
template<class T>
QQmlGuard<T> &QQmlGuard<T>::operator=(const QQmlGuard<T> &g)
{
objectDestroyed = g.objectDestroyed;
setObject(g.object());
return *this;
}
template<class T>
QQmlGuard<T> &QQmlGuard<T>::operator=(T *g)
{
/* this does not touch objectDestroyed, as operator= is only a convenience
* for setObject. All logic involving objectDestroyed is (sub-)class specific
* and remains unaffected.
*/
setObject(g);
return *this;
}
void QQmlGuardImpl::setObject(QObject *g)
{
if (g != o) {
if (prev) remGuard();
o = g;
if (o) addGuard();
}
}
QT_END_NAMESPACE
#endif // QQMLGUARD_P_H
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