qt-everywhere-src-5.15.1/qt3d/src/render/frontend/qabstractfunctor.h

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#ifndef QT3DRENDER_QABSTRACTFUNCTOR_H
#define QT3DRENDER_QABSTRACTFUNCTOR_H

#include <Qt3DRender/qt3drender_global.h>

QT_BEGIN_NAMESPACE

namespace Qt3DRender {

// This will generate a unique id() function per type
// <=> 1 unique function address per type
template<class T>
struct FunctorType
{
    static qintptr id()
    {
        // The MSVC linker can under some cases optimize all the template
        // functions into a single function. The code below is there to ensure
        // that the linker won't collapse all these distincts functions into one
        static T *t = nullptr;
        return reinterpret_cast<qintptr>(t);
    }
};

template<class T>
Q3D_DECL_DEPRECATED qintptr functorTypeId()
{
    return reinterpret_cast<qintptr>(&FunctorType<T>::id);
}

#define QT3D_FUNCTOR(Class)                     \
   qintptr id() const override {         \
        return Qt3DRender::functorTypeId<Class>();    \
   }


class Q_3DRENDERSHARED_EXPORT QAbstractFunctor
{
public:
    Q3D_DECL_DEPRECATED QAbstractFunctor() = default;
    virtual ~QAbstractFunctor();
    virtual qintptr id() const = 0;

    // TODO: Remove when moving a copy of this to Qt3DCore
    template<class T>
    const T *functor_cast(const QAbstractFunctor *other) const
    {
        if (other->id() == functorTypeId<T>())
            return static_cast<const T *>(other);
        return nullptr;
    }
private:
    Q_DISABLE_COPY(QAbstractFunctor)
};

template<class T>
const T *functor_cast(const QAbstractFunctor *other)
{
    if (other->id() == functorTypeId<T>())
        return static_cast<const T *>(other);
    return nullptr;
}

} // Qt3D

QT_END_NAMESPACE

#endif // QT3DRENDER_QABSTRACTFUNCTOR_H