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// Copyright (C) 2021 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 QNATIVEINTERFACE_H
#define QNATIVEINTERFACE_H
#include <QtCore/qglobal.h>
QT_BEGIN_NAMESPACE
// We declare a virtual non-inline function in the form
// of the destructor, making it the key function. This
// ensures that the typeinfo of the class is exported.
// By being protected, we also ensure that pointers to
// the interface can't be deleted.
#define QT_DECLARE_NATIVE_INTERFACE_3(NativeInterface, Revision, BaseType) \
protected: \
virtual ~NativeInterface(); \
\
struct TypeInfo { \
using baseType = BaseType; \
static constexpr char const *name = QT_STRINGIFY(NativeInterface); \
static constexpr int revision = Revision; \
}; \
\
template <typename, typename> \
friend struct QNativeInterface::Private::has_type_info; \
\
template <typename> \
friend bool constexpr QNativeInterface::Private::hasTypeInfo(); \
\
template <typename> \
friend struct QNativeInterface::Private::TypeInfo; \
public: \
NativeInterface() = default; \
Q_DISABLE_COPY_MOVE(NativeInterface)
// Revisioned interfaces only make sense when exposed through a base
// type via QT_DECLARE_NATIVE_INTERFACE_ACCESSOR, as the revision
// checks happen at that level (and not for normal dynamic_casts).
#define QT_DECLARE_NATIVE_INTERFACE_2(NativeInterface, Revision) \
static_assert(false, "Must provide a base type when specifying revision");
#define QT_DECLARE_NATIVE_INTERFACE_1(NativeInterface) \
QT_DECLARE_NATIVE_INTERFACE_3(NativeInterface, 0, void)
#define QT_DECLARE_NATIVE_INTERFACE(...) \
QT_OVERLOADED_MACRO(QT_DECLARE_NATIVE_INTERFACE, __VA_ARGS__)
namespace QNativeInterface::Private {
// Basic type-trait to verify that a given native interface has
// all the required type information for us to evaluate it.
template <typename NativeInterface, typename = void>
struct has_type_info : std::false_type {};
// The type-trait is friended by TypeInfo, so that we can
// evaluate TypeInfo in the template arguments.
template <typename NativeInterface>
struct has_type_info<NativeInterface, std::void_t<
typename NativeInterface::TypeInfo,
typename NativeInterface::TypeInfo::baseType,
decltype(&NativeInterface::TypeInfo::name),
decltype(&NativeInterface::TypeInfo::revision)
>> : std::true_type {};
// We need to wrap the instantiation of has_type_info in a
// function friended by TypeInfo, otherwise MSVC will not
// let us evaluate TypeInfo in the template arguments.
template <typename NativeInterface>
bool constexpr hasTypeInfo()
{
return has_type_info<NativeInterface>::value;
}
template <typename NativeInterface>
struct TypeInfo
{
// To ensure SFINAE works for hasTypeInfo we can't use it in a constexpr
// variable that also includes an expression that relies on the type
// info. This helper variable is okey, as it it self contained.
static constexpr bool haveTypeInfo = hasTypeInfo<NativeInterface>();
// We can then use the helper variable in a constexpr condition in a
// function, which does not break SFINAE if haveTypeInfo is false.
template <typename BaseType>
static constexpr bool isCompatibleHelper()
{
if constexpr (haveTypeInfo)
return std::is_base_of<typename NativeInterface::TypeInfo::baseType, BaseType>::value;
else
return false;
}
// MSVC however doesn't like constexpr functions in enable_if_t conditions,
// so we need to wrap it yet again in a constexpr variable. This is fine,
// as all the SFINAE magic has been resolved at this point.
template <typename BaseType>
static constexpr bool isCompatibleWith = isCompatibleHelper<BaseType>();
// The revision and name accessors are not used in enable_if_t conditions,
// so we can leave them as constexpr functions. As this class template is
// friended by TypeInfo we can access the protected members of TypeInfo.
static constexpr int revision()
{
if constexpr (haveTypeInfo)
return NativeInterface::TypeInfo::revision;
else
return 0;
}
static constexpr char const *name()
{
if constexpr (haveTypeInfo)
return NativeInterface::TypeInfo::name;
else
return nullptr;
}
};
// Wrapper type to make the error message in case
// of incompatible interface types read better.
template <typename I>
struct NativeInterface : TypeInfo<I> {};
} // QNativeInterface::Private
// Declares an accessor for the native interface
#ifdef Q_QDOC
#define QT_DECLARE_NATIVE_INTERFACE_ACCESSOR(T) \
template <typename QNativeInterface> \
QNativeInterface *nativeInterface() const;
#else
#define QT_DECLARE_NATIVE_INTERFACE_ACCESSOR(T) \
template <typename NativeInterface, typename TypeInfo = QNativeInterface::Private::NativeInterface<NativeInterface>, \
typename BaseType = T, std::enable_if_t<TypeInfo::template isCompatibleWith<T>, bool> = true> \
NativeInterface *nativeInterface() const \
{ \
return static_cast<NativeInterface*>(resolveInterface( \
TypeInfo::name(), TypeInfo::revision())); \
} \
protected: \
void *resolveInterface(const char *name, int revision) const; \
public:
#endif
QT_END_NAMESPACE
#endif // QNATIVEINTERFACE_H
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