1 files changed, 95 insertions, 0 deletions
diff --git a/src/qml/qml/qqmlguardedcontextdata_p.h b/src/qml/qml/qqmlguardedcontextdata_p.h
new file mode 100644
index 0000000000..048f809f48
--- /dev/null
+++ b/src/qml/qml/qqmlguardedcontextdata_p.h
@@ -0,0 +1,95 @@
+// 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