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Merge branch 'connect-overloaded-c++17'

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Make Connect() work with overloaded event handlers in C++17.

See https://github.com/wxWidgets/wxWidgets/pull/2126
This commit is contained in:
Vadim Zeitlin
2020-12-04 20:02:46 +01:00
parent dc33f27e10 f48099e00a
commit 859193fb65
2 changed files with 110 additions and 109 deletions
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57
include/wx/event.h
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@@ -144,43 +144,58 @@ inline wxEventFunction wxEventFunctionCast(void (wxEvtHandler::*func)(T&))
wxGCC_WARNING_RESTORE_CAST_FUNCTION_TYPE()
}
// Special hack to remove "noexcept" from the function type when using C++17 or
// later: static_cast<> below would fail to cast a member function pointer to a
// member of a derived class to the base class if noexcept is specified for the
// former, so remove it first if necessary.
// In good old pre-C++17 times we could just static_cast the event handler,
// defined in some class deriving from wxEvtHandler, to the "functype" which is
// a type of wxEvtHandler method. But with C++17 this doesn't work when the
// handler is a noexcept function, so we need to cast it to a noexcept function
// pointer first.
#if __cplusplus >= 201703L
namespace wxPrivate
{
// Generic template version, doing nothing.
template <typename T>
struct RemoveNoexceptEventHandler
// Cast to noexcept function type first if necessary.
template <typename E, typename C>
constexpr auto DoCast(void (C::*pmf)(E&))
{
using type = T;
return static_cast<void (wxEvtHandler::*)(E&)>(pmf);
}
template <typename E, typename C>
constexpr auto DoCast(void (C::*pmf)(E&) noexcept)
{
return static_cast<void (wxEvtHandler::*)(E&)>(
static_cast<void (wxEvtHandler::*)(E&) noexcept>(pmf)
);
}
// Helper used to recover the type of the handler argument from the function
// type. This is required in order to explicitly pass this type to DoCast<> as
// the compiler would be unable to deduce it for overloaded functions.
// Generic template version, doing nothing.
template <typename F>
struct EventArgOf;
// Specialization sufficient to cover all event handler function types.
template <typename C, typename E>
struct EventArgOf<void (C::*)(E&)>
{
using type = E;
};
// Specialization removing noexcept when it's specified.
//
// Note that this doesn't pretend to be generally suitable, this is just enough
// to work in our particular case.
template <typename R, typename C, typename E>
struct RemoveNoexceptEventHandler<R (C::*)(E&) noexcept>
{
using type = R (C::*)(E&);
};
} // namespace wxPrivate
#define wxREMOVE_NOEXCEPT_EVENT_HANDLER(pmf) \
static_cast<wxPrivate::RemoveNoexceptEventHandler<decltype(pmf)>::type>(pmf)
#define wxEventHandlerNoexceptCast(functype, pmf) \
wxPrivate::DoCast<wxPrivate::EventArgOf<functype>::type>(pmf)
#else
#define wxREMOVE_NOEXCEPT_EVENT_HANDLER(pmf) pmf
#define wxEventHandlerNoexceptCast(functype, pmf) static_cast<functype>(pmf)
#endif
// Try to cast the given event handler to the correct handler type:
#define wxEVENT_HANDLER_CAST( functype, func ) \
wxEventFunctionCast(static_cast<functype>(wxREMOVE_NOEXCEPT_EVENT_HANDLER(&func)))
wxEventFunctionCast(wxEventHandlerNoexceptCast(functype, &func))
// The tag is a type associated to the event type (which is an integer itself,