diff options
Diffstat (limited to 'lib/qt_connection_util.h')
| -rw-r--r-- | lib/qt_connection_util.h | 169 |
1 files changed, 68 insertions, 101 deletions
diff --git a/lib/qt_connection_util.h b/lib/qt_connection_util.h index 86593cc8..ef7f6f80 100644 --- a/lib/qt_connection_util.h +++ b/lib/qt_connection_util.h @@ -9,101 +9,67 @@ namespace Quotient { namespace _impl { - template <typename... ArgTs> - using decorated_slot_tt = - std::function<void(QMetaObject::Connection&, const ArgTs&...)>; + enum ConnectionType { SingleShot, Until }; - template <typename SenderT, typename SignalT, typename ContextT, typename... ArgTs> - inline QMetaObject::Connection - connectDecorated(SenderT* sender, SignalT signal, ContextT* context, - decorated_slot_tt<ArgTs...> decoratedSlot, - Qt::ConnectionType connType) + template <ConnectionType CType> + inline auto connect(auto* sender, auto signal, auto* context, auto slotLike, + Qt::ConnectionType connType) { - auto pc = std::make_unique<QMetaObject::Connection>(); - auto& c = *pc; // Resolve a reference before pc is moved to lambda - - // Perfect forwarding doesn't work through signal-slot connections - - // arguments are always copied (at best - COWed) to the context of - // the slot. Therefore the slot decorator receives const ArgTs&... - // rather than ArgTs&&... - // TODO (C++20): std::bind_front() instead of lambda. - c = QObject::connect(sender, signal, context, - [pc = std::move(pc), - decoratedSlot = std::move(decoratedSlot)](const ArgTs&... args) { - Q_ASSERT(*pc); // If it's been triggered, it should exist - decoratedSlot(*pc, args...); + auto pConn = std::make_unique<QMetaObject::Connection>(); + auto& c = *pConn; // Save the reference before pConn is moved from + c = QObject::connect( + sender, signal, context, + [slotLike, pConn = std::move(pConn)](const auto&... args) + // The requires-expression below is necessary to prevent Qt + // from eagerly trying to fill the lambda with more arguments + // than slotLike() (i.e., the original slot) can handle + requires requires { slotLike(args...); } { + static_assert(CType == Until || CType == SingleShot, + "Unsupported disconnection type"); + if constexpr (CType == SingleShot) { + // Disconnect early to avoid re-triggers during slotLike() + QObject::disconnect(*pConn); + // Qt kindly keeps slot objects until they do their job, + // even if they disconnect themselves in the process (see + // how doActivate() in qobject.cpp handles c->slotObj). + slotLike(args...); + } else if constexpr (CType == Until) { + if (slotLike(args...)) + QObject::disconnect(*pConn); + } }, connType); return c; } - template <typename SenderT, typename SignalT, typename ContextT, - typename... ArgTs> - inline QMetaObject::Connection - connectUntil(SenderT* sender, SignalT signal, ContextT* context, - std::function<bool(ArgTs...)> functor, - Qt::ConnectionType connType) - { - return connectDecorated(sender, signal, context, - decorated_slot_tt<ArgTs...>( - [functor = std::move(functor)](QMetaObject::Connection& c, - const ArgTs&... args) { - if (functor(args...)) - QObject::disconnect(c); - }), - connType); - } - template <typename SenderT, typename SignalT, typename ContextT, - typename... ArgTs> - inline QMetaObject::Connection - connectSingleShot(SenderT* sender, SignalT signal, ContextT* context, - std::function<void(ArgTs...)> slot, - Qt::ConnectionType connType) - { - return connectDecorated(sender, signal, context, - decorated_slot_tt<ArgTs...>( - [slot = std::move(slot)](QMetaObject::Connection& c, - const ArgTs&... args) { - QObject::disconnect(c); - slot(args...); - }), - connType); - } - // TODO: get rid of it as soon as Apple Clang gets proper deduction guides - // for std::function<> - // ...or consider using QtPrivate magic used by QObject::connect() - // ...for inspiration, also check a possible std::not_fn implementation - // at https://en.cppreference.com/w/cpp/utility/functional/not_fn - template <typename FnT> - inline auto wrap_in_function(FnT&& f) - { - return typename function_traits<FnT>::function_type(std::forward<FnT>(f)); - } + template <typename SlotT, typename ReceiverT> + concept PmfSlot = + (fn_arg_count_v<SlotT> > 0 + && std::is_base_of_v<std::decay_t<fn_arg_t<SlotT, 0>>, ReceiverT>); } // namespace _impl -/*! \brief Create a connection that self-disconnects when its "slot" returns true - * - * A slot accepted by connectUntil() is different from classic Qt slots - * in that its return value must be bool, not void. The slot's return value - * controls whether the connection should be kept; if the slot returns false, - * the connection remains; upon returning true, the slot is disconnected from - * the signal. Because of a different slot signature connectUntil() doesn't - * accept member functions as QObject::connect or Quotient::connectSingleShot - * do; you should pass a lambda or a pre-bound member function to it. - */ -template <typename SenderT, typename SignalT, typename ContextT, typename FunctorT> -inline auto connectUntil(SenderT* sender, SignalT signal, ContextT* context, - const FunctorT& slot, +//! \brief Create a connection that self-disconnects when its slot returns true +//! +//! A slot accepted by connectUntil() is different from classic Qt slots +//! in that its return value must be bool, not void. Because of that different +//! signature connectUntil() doesn't accept member functions in the way +//! QObject::connect or Quotient::connectSingleShot do; you should pass a lambda +//! or a pre-bound member function to it. +//! \return whether the connection should be dropped; false means that the +//! connection remains; upon returning true, the slot is disconnected +//! from the signal. +inline auto connectUntil(auto* sender, auto signal, auto* context, + auto smartSlot, Qt::ConnectionType connType = Qt::AutoConnection) { - return _impl::connectUntil(sender, signal, context, _impl::wrap_in_function(slot), - connType); + return _impl::connect<_impl::Until>(sender, signal, context, smartSlot, + connType); } -/// Create a connection that self-disconnects after triggering on the signal -template <typename SenderT, typename SignalT, typename ContextT, typename FunctorT> -inline auto connectSingleShot(SenderT* sender, SignalT signal, - ContextT* context, const FunctorT& slot, +//! Create a connection that self-disconnects after triggering on the signal +template <typename ContextT, typename SlotT> +inline auto connectSingleShot(auto* sender, auto signal, ContextT* context, + SlotT slot, Qt::ConnectionType connType = Qt::AutoConnection) { #if QT_VERSION_MAJOR >= 6 @@ -111,25 +77,26 @@ inline auto connectSingleShot(SenderT* sender, SignalT signal, Qt::ConnectionType(connType | Qt::SingleShotConnection)); #else - return _impl::connectSingleShot( - sender, signal, context, _impl::wrap_in_function(slot), connType); -} - -// Specialisation for usual Qt slots passed as pointers-to-members. -template <typename SenderT, typename SignalT, typename ReceiverT, - typename SlotObjectT, typename... ArgTs> -inline auto connectSingleShot(SenderT* sender, SignalT signal, - ReceiverT* receiver, - void (SlotObjectT::*slot)(ArgTs...), - Qt::ConnectionType connType = Qt::AutoConnection) -{ - // TODO: when switching to C++20, use std::bind_front() instead - return _impl::connectSingleShot(sender, signal, receiver, - _impl::wrap_in_function( - [receiver, slot](const ArgTs&... args) { - (receiver->*slot)(args...); - }), - connType); + // In case of classic Qt pointer-to-member-function slots the receiver + // object has to be pre-bound to the slot to make it self-contained + if constexpr (_impl::PmfSlot<SlotT, ContextT>) { + auto&& boundSlot = +# if __cpp_lib_bind_front // Needs Apple Clang 13 (other platforms are fine) + std::bind_front(slot, context); +# else + [context, slot](const auto&... args) + requires requires { (context->*slot)(args...); } + { + (context->*slot)(args...); + }; +# endif + return _impl::connect<_impl::SingleShot>( + sender, signal, context, + std::forward<decltype(boundSlot)>(boundSlot), connType); + } else { + return _impl::connect<_impl::SingleShot>(sender, signal, context, slot, + connType); + } #endif } |