diff options
Diffstat (limited to 'src/corelib/global')
| -rw-r--r-- | src/corelib/global/qnativeinterface.h | 108 |
1 files changed, 91 insertions, 17 deletions
diff --git a/src/corelib/global/qnativeinterface.h b/src/corelib/global/qnativeinterface.h index d32e2cd982..395a4ba1da 100644 --- a/src/corelib/global/qnativeinterface.h +++ b/src/corelib/global/qnativeinterface.h @@ -61,11 +61,21 @@ QT_BEGIN_NAMESPACE #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: \ // Revisioned interfaces only make sense when exposed through a base @@ -81,35 +91,97 @@ QT_BEGIN_NAMESPACE 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> - struct TypeInfo : private NativeInterface + bool constexpr hasTypeInfo() { - static constexpr char const *name() { return NativeInterface::TypeInfo::name; } - static constexpr int revision() { return NativeInterface::TypeInfo::revision; } + return has_type_info<NativeInterface>::value; + } - template<typename BaseType> - static constexpr bool isCompatibleWith = - std::is_base_of<typename NativeInterface::TypeInfo::baseType, BaseType>::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> {}; + template <typename T> Q_NATIVE_INTERFACE_IMPORT void *resolveInterface(const T *that, const char *name, int revision); Q_CORE_EXPORT Q_DECLARE_LOGGING_CATEGORY(lcNativeInterface) -} + +} // QNativeInterface::Private // Declares an accessor for the native interface -#define QT_DECLARE_NATIVE_INTERFACE_ACCESSOR \ - template <typename I> \ - I *nativeInterface() const \ +#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 \ { \ - using T = std::decay_t<decltype(*this)>; \ - using NativeInterface = QNativeInterface::Private::TypeInfo<I>; \ - static_assert(NativeInterface::template isCompatibleWith<T>, \ - "T::nativeInterface<I>() requires that native interface I is compatible with T"); \ - \ - return static_cast<I*>(QNativeInterface::Private::resolveInterface(this, \ - NativeInterface::name(), NativeInterface::revision())); \ + return static_cast<NativeInterface*>( \ + QNativeInterface::Private::resolveInterface(this, \ + TypeInfo::name(), TypeInfo::revision())); \ } // Provides a definition for the interface destructor @@ -134,6 +206,8 @@ namespace QNativeInterface::Private { revision, TypeInfo<NativeInterface>::revision(), name); \ return nullptr; \ } \ + } else { \ + qCDebug(lcNativeInterface, "No match for requested interface name %s", name); \ } QT_END_NAMESPACE |