1 files changed, 127 insertions, 0 deletions
diff --git a/src/corelib/platform/windows/qcomobject_p.h b/src/corelib/platform/windows/qcomobject_p.h
new file mode 100644
index 0000000000..8f27a18ff6
--- /dev/null
+++ b/src/corelib/platform/windows/qcomobject_p.h
@@ -0,0 +1,127 @@
+// Copyright (C) 2023 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 QCOMOBJECT_P_H
+#define QCOMOBJECT_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 <QtCore/private/qglobal_p.h>
+
+#if defined(Q_OS_WIN) || defined(Q_QDOC)
+
+#  include <QtCore/qt_windows.h>
+
+QT_BEGIN_NAMESPACE
+
+namespace QtPrivate {
+
+template <typename... TInterfaces>
+struct QComObjectTraits
+{
+    static constexpr bool isGuidOf(REFIID riid) noexcept
+    {
+        return ((riid == __uuidof(TInterfaces)) || ...);
+    }
+};
+
+} // namespace QtPrivate
+
+// NOTE: In order to be able to query the intermediate interface, i.e. the one you do not specify in
+// QComObject interface list (TFirstInterface, TInterfaces) but that is a base for any of them
+// (except IUnknown) you need to provide an explicit specialization of function
+// QComObjectTraits<...>::isGuidOf for that type. For example, if you want to inherit interface
+// IMFSampleGrabberSinkCallback which inherits IMFClockStateSink and you want to be able to query
+// the latter one you need to provide this explicit specialization:
+//
+// class SinkCallback : public QComObject<IMFSampleGrabberSinkCallback>
+// {
+// ...
+// };
+//
+// namespace QtPrivate {
+//
+// template <>
+// struct QComObjectTraits<IMFSampleGrabberSinkCallback>
+// {
+//     static constexpr bool isGuidOf(REFIID riid) noexcept
+//     {
+//         return QComObjectTraits<IMFSampleGrabberSinkCallback, IMFClockStateSink>::isGuidOf(riid);
+//     }
+// };
+//
+// }
+
+template <typename TFirstInterface, typename... TAdditionalInterfaces>
+class QComObject : public TFirstInterface, public TAdditionalInterfaces...
+{
+public:
+    STDMETHODIMP QueryInterface(REFIID riid, void **ppvObject) override
+    {
+        if (!ppvObject)
+            return E_POINTER;
+
+        if (riid == __uuidof(IUnknown)) {
+            *ppvObject = static_cast<IUnknown *>(static_cast<TFirstInterface *>(this));
+            AddRef();
+
+            return S_OK;
+        }
+
+        return tryQueryInterface<TFirstInterface, TAdditionalInterfaces...>(riid, ppvObject);
+    }
+
+    STDMETHODIMP_(ULONG) AddRef() override { return ++m_referenceCount; }
+
+    STDMETHODIMP_(ULONG) Release() override
+    {
+        const LONG referenceCount = --m_referenceCount;
+        if (referenceCount == 0)
+            delete this;
+
+        return referenceCount;
+    }
+
+protected:
+    QComObject() = default;
+
+    // Destructor is not public. Caller should call Release.
+    // Derived class should make its destructor private to force this behavior.
+    virtual ~QComObject() = default;
+
+private:
+    template <typename TInterface, typename... TRest>
+    HRESULT tryQueryInterface(REFIID riid, void **ppvObject)
+    {
+        if (QtPrivate::QComObjectTraits<TInterface>::isGuidOf(riid)) {
+            *ppvObject = static_cast<TInterface *>(this);
+            AddRef();
+
+            return S_OK;
+        }
+
+        if constexpr (sizeof...(TRest) > 0)
+            return tryQueryInterface<TRest...>(riid, ppvObject);
+
+        *ppvObject = nullptr;
+
+        return E_NOINTERFACE;
+    }
+
+    std::atomic<LONG> m_referenceCount = 1;
+};
+
+QT_END_NAMESPACE
+
+#endif // Q_OS_WIN
+
+#endif // QCOMOBJECT_P_H