diff options
| -rw-r--r-- | indra/llcommon/llevents.cpp | 23 | ||||
| -rw-r--r-- | indra/llcommon/llevents.h | 20 |
2 files changed, 28 insertions, 15 deletions
diff --git a/indra/llcommon/llevents.cpp b/indra/llcommon/llevents.cpp index dce97b5411..eedd8c92b5 100644 --- a/indra/llcommon/llevents.cpp +++ b/indra/llcommon/llevents.cpp @@ -545,10 +545,8 @@ bool LLEventStream::post(const LLSD& event) *****************************************************************************/ bool LLEventMailDrop::post(const LLSD& event) { - bool posted = false; - - if (!mSignal->empty()) - posted = LLEventStream::post(event); + // forward the call to our base class + bool posted = LLEventStream::post(event); if (!posted) { // if the event was not handled we will save it for later so that it can @@ -564,16 +562,25 @@ LLBoundListener LLEventMailDrop::listen_impl(const std::string& name, const NameList& after, const NameList& before) { - if (!mEventHistory.empty()) + // Before actually connecting this listener for subsequent post() calls, + // first feed each of the saved events, in order, to the new listener. + // Remove any that this listener consumes -- Effective STL, Item 9. + for (auto hi(mEventHistory.begin()), hend(mEventHistory.end()); hi != hend; ) { - if (listener(mEventHistory.front())) + if (listener(*hi)) { - mEventHistory.pop_front(); + // new listener consumed this event, erase it + hi = mEventHistory.erase(hi); + } + else + { + // listener did not consume this event, just move along + ++hi; } } + // let base class perform the actual connection return LLEventStream::listen_impl(name, listener, after, before); - } diff --git a/indra/llcommon/llevents.h b/indra/llcommon/llevents.h index 1d51c660ed..5d60c63810 100644 --- a/indra/llcommon/llevents.h +++ b/indra/llcommon/llevents.h @@ -650,15 +650,21 @@ public: * LLEventMailDrop *****************************************************************************/ /** - * LLEventMailDrop is a specialization of LLEventStream. Events are posted normally, - * however if no listeners return that they have handled the event it is placed in - * a queue. Subsequent attaching listeners will receive stored events from the queue - * until a listener indicates that the event has been handled. In order to receive - * multiple events from a mail drop the listener must disconnect and reconnect. + * LLEventMailDrop is a specialization of LLEventStream. Events are posted + * normally, however if no listener returns that it has handled the event + * (returns true), it is placed in a queue. Subsequent attaching listeners + * will receive stored events from the queue until some listener indicates + * that the event has been handled. + * + * LLEventMailDrop completely decouples the timing of post() calls from + * listen() calls: every event posted to an LLEventMailDrop is eventually seen + * by all listeners, until some listener consumes it. The caveat is that each + * event *must* eventually reach a listener that will consume it, else the + * queue will grow to arbitrary length. * * @NOTE: When using an LLEventMailDrop (or LLEventQueue) with a LLEventTimeout or - * LLEventFilter attaching the filter downstream using Timeout's constructor will - * cause the MailDrop to discharge any of it's stored events. The timeout should + * LLEventFilter attaching the filter downstream, using Timeout's constructor will + * cause the MailDrop to discharge any of its stored events. The timeout should * instead be connected upstream using its listen() method. * See llcoro::suspendUntilEventOnWithTimeout() for an example. */ |