Qt源码之事件处理

 某对象在发送一个事件的时候，使用sendEvent()或者postEvent()函数进行事件的发送操作。查看发送事件的两个函数源代码：

//sendEvent()

inline bool QCoreApplication::sendEvent(QObject *receiver, QEvent *event){  

    if (event) event->spont = false; return self ? self->notifyInternal(receiver, event) : false; 

}//事件要在栈上分配，不走事件队列，只支持同步操作

其中notifyInternal(receiver, event)调用notify(receiver, event)调用notify_helper(receiver, event){

    if (sendThroughApplicationEventFilters(receiver, event))  return true;
    if (sendThroughObjectEventFilters(receiver, event))  return true;
    return receiver->event(event);//这就是我们需要处理的事件
}

//postEvent()

void QCoreApplication::postEvent(QObject *receiver, QEvent *event, int priority)
{
    if (receiver == 0) {
        qWarning("QCoreApplication::postEvent: Unexpected null receiver");
        delete event;
        return;
    }
    QThreadData * volatile * pdata = &receiver->d_func()->threadData;
    QThreadData *data = *pdata;
    if (!data) {
        delete event;
        return;
    }
    data->postEventList.mutex.lock();
    QMutexUnlocker locker(&data->postEventList.mutex);
    if (receiver->d_func()->postedEvents
        && self && self->compressEvent(event, receiver, &data->postEventList)) {
        return;
    }
    if (event->type() == QEvent::DeferredDelete && data == QThreadData::current()) {
        static_cast<QDeferredDeleteEvent *>(event)->level = data->loopLevel;
    }
    QScopedPointer<QEvent> eventDeleter(event);
    data->postEventList.addEvent(QPostEvent(receiver, event, priority));
    eventDeleter.take();
    event->posted = true;
    ++receiver->d_func()->postedEvents;
    data->canWait = false;
    locker.unlock();
    QAbstractEventDispatcher* dispatcher = data->eventDispatcher.loadAcquire();
    if (dispatcher)
        dispatcher->wakeUp();
}//由此可以看出，事件要在堆上分配，用接收端线程事件队列postEventList进行维护，立即返回，支持异步操作；引用原文：When control returns to main
 event loop , all events that are storeed in the queue will be sent using the notify(receive, event) funcation