diff options
Diffstat (limited to 'lib/events')
| -rw-r--r-- | lib/events/event.h | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/lib/events/event.h b/lib/events/event.h index da6cf3c7..043d4f54 100644 --- a/lib/events/event.h +++ b/lib/events/event.h @@ -332,6 +332,13 @@ inline bool isUnknown(const Event& e) return e.type() == UnknownEventTypeId; } +//! \brief Cast the event pointer down in a type-safe way +//! +//! Checks that the event \p eptr points to actually is of the requested type +//! and returns a (plain) pointer to the event downcast to that type. \p eptr +//! can be either "dumb" (BaseEventT*) or "smart" (`event_ptr_tt<>`). This +//! overload doesn't affect the event ownership - if the original pointer owns +//! the event it must outlive the downcast pointer to keep it from dangling. template <class EventT, typename BasePtrT> inline auto eventCast(const BasePtrT& eptr) -> decltype(static_cast<EventT*>(&*eptr)) @@ -341,6 +348,28 @@ inline auto eventCast(const BasePtrT& eptr) : nullptr; } +//! \brief Cast the event pointer down in a type-safe way, with moving +//! +//! Checks that the event \p eptr points to actually is of the requested type; +//! if (and only if) it is, releases the pointer, downcasts it to the requested +//! event type and returns a new smart pointer wrapping the downcast one. +//! Unlike the non-moving eventCast() overload, this one only accepts a smart +//! pointer, and that smart pointer should be an rvalue (either a temporary, +//! or as a result of std::move()). The ownership, respectively, is transferred +//! to the new pointer; the original smart pointer is reset to nullptr, as is +//! normal for `unique_ptr<>::release()`. +//! \note If \p eptr's event type does not match \p EventT it retains ownership +//! after calling this overload; if it is a temporary, this normally +//! leads to the event getting deleted along with the end of +//! the temporary's lifetime. +template <class EventT, typename BaseEventT> +inline auto eventCast(event_ptr_tt<BaseEventT>&& eptr) +{ + return eptr && is<std::decay_t<EventT>>(*eptr) + ? event_ptr_tt<EventT>(static_cast<EventT*>(eptr.release())) + : nullptr; +} + namespace _impl { template <typename FnT, class BaseT> concept Invocable_With_Downcast = |