Vkm::Engine::EventBus Class Reference

Typed pub/sub event dispatcher. More...

#include <event_bus.h>

Public Member Functions
template<typename EventT>
ListenerId	subscribe (std::function< void(const EventT &)> callback)
	Register a callback for events of type EventT.
template<typename EventT>
bool	unsubscribe (ListenerId id)
	Remove a registered listener.
template<typename EventT>
void	emit (const EventT &event)
	Fire event synchronously to every listener now.
template<typename EventT>
void	enqueue (EventT event)
	Queue event for delivery on the next flush().
void	flush ()
	Drain every per-type queue to its listeners.
void	dropIdleBuses ()
	Drop every bus nothing listens to any more.
std::size_t	busCount () const
	How many event types have a bus right now.

Detailed Description

Typed pub/sub event dispatcher.

Owned by the Engine and carried on FrameContext. Main-thread only. Subscribing and unsubscribing inside a callback are allowed; docs/reference/events.md has the delivery rules.

Member Function Documentation

subscribe()

template<typename EventT>

ListenerId Vkm::Engine::EventBus::subscribe ( std::function< void(const EventT &)> callback )

inline

Register a callback for events of type EventT.

Template Parameters

EventT

Event type listened for.

Parameters

callback

Called with each EventT emitted or flushed from now on.

Returns

ListenerId for a later unsubscribe().

unsubscribe()

template<typename EventT>

bool Vkm::Engine::EventBus::unsubscribe ( ListenerId id )

inline

Remove a registered listener.

Template Parameters

EventT

Event type it was subscribed to.

Parameters

id	What subscribe() returned.

Returns

true if it was found and removed.

emit()

template<typename EventT>

void Vkm::Engine::EventBus::emit ( const EventT & event )

inline

Fire event synchronously to every listener now.

Template Parameters

EventT

Event type; no bus is created when nothing listens.

Parameters

event

Passed to each listener.

enqueue()

template<typename EventT>

void Vkm::Engine::EventBus::enqueue ( EventT event )

inline

Queue event for delivery on the next flush().

Template Parameters

EventT

Event type.

Parameters

event

Event to queue; moved in.

flush()

void Vkm::Engine::EventBus::flush

(

)

Drain every per-type queue to its listeners.

Engine::run calls it at the top of Simulation, once per tick and once per frame. A nested call from a listener is ignored.

dropIdleBuses()

void Vkm::Engine::EventBus::dropIdleBuses

(

)

Drop every bus nothing listens to any more.

For just before a gameplay module is unmapped (see ScriptModule::releaseRegistrations): a Bus<EventT> for a module's event holds the module's vtable, so a flush() after reload would call into unmapped memory. A bus with a listener stays, so drop those first; an idle bus has nowhere to deliver, so nothing is lost.

busCount()

std::size_t Vkm::Engine::EventBus::busCount ( ) const

inline

How many event types have a bus right now.

Returns

The number of live buses.

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The documentation for this class was generated from the following file:

• core/event/event_bus.h