qqmlguardedcontextdata_p.h

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// Copyright (C) 2020 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 QQMLGUARDEDCONTEXTDATA_P_H
#define QQMLGUARDEDCONTEXTDATA_P_H
 
//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  This header file may change from version to
// version without notice, or even be removed.
//
// We mean it.
//
 
#include <QtQml/private/qtqmlglobal_p.h>
#include <QtQml/private/qqmlcontextdata_p.h>
 
QT_BEGIN_NAMESPACE
 
class QQmlGuardedContextData
{
    Q_DISABLE_COPY(QQmlGuardedContextData);
public:
    QQmlGuardedContextData() = default;
    ~QQmlGuardedContextData() { unlink(); }
 
    QQmlGuardedContextData(QQmlGuardedContextData &&) = default;
    QQmlGuardedContextData &operator=(QQmlGuardedContextData &&) = default;
 
    QQmlGuardedContextData(QQmlRefPointer<QQmlContextData> data)
    {
        setContextData(std::move(data));
    }
 
    QQmlGuardedContextData &operator=(QQmlRefPointer<QQmlContextData> d)
    {
        setContextData(std::move(d));
        return *this;
    }
 
    QQmlRefPointer<QQmlContextData> contextData() const { return m_contextData; }
    void setContextData(QQmlRefPointer<QQmlContextData> contextData)
    {
        if (m_contextData.data() == contextData.data())
            return;
        unlink();
 
        if (contextData) {
            m_contextData = std::move(contextData);
            m_next = m_contextData->m_contextGuards;
            if (m_next)
                m_next->m_prev = &m_next;
 
            m_contextData->m_contextGuards = this;
            m_prev = &m_contextData->m_contextGuards;
        }
    }
 
    bool isNull() const { return !m_contextData; }
 
    operator const QQmlRefPointer<QQmlContextData> &() const { return m_contextData; }
    QQmlContextData &operator*() const { return m_contextData.operator*(); }
    QQmlContextData *operator->() const { return m_contextData.operator->(); }
 
    QQmlGuardedContextData *next() const { return m_next; }
 
private:
    void reset()
    {
        m_contextData.reset();
        m_next = nullptr;
        m_prev = nullptr;
    }
 
    void unlink()
    {
        if (m_prev) {
            *m_prev = m_next;
            if (m_next)
                m_next->m_prev = m_prev;
            reset();
        }
    }
 
    QQmlRefPointer<QQmlContextData> m_contextData;
    QQmlGuardedContextData  *m_next = nullptr;
    QQmlGuardedContextData **m_prev = nullptr;
};
 
QT_END_NAMESPACE
 
#endif // QQMLGUARDEDCONTEXTDATA_P_H