QT5的post Event解析

标签：通过   cal   查看   oid   except   机制   when   异步   async   

大家都知道，QT的事件机制，查了好多网上的帖子，分析的不够到位，今天给大家分享下，我的分析，请高手指正：
都知道post Event通过
    QScopedPointer<QEvent> eventDeleter(event);
//增加到事件队列
    data->postEventList.addEvent(QPostEvent(receiver, event, priority));
    eventDeleter.take();
    event->posted = true;
    ++receiver->d_func()->postedEvents;
    data->canWait = false;
    locker.unlock();

//事件分发
    QAbstractEventDispatcher* dispatcher = data->eventDispatcher.loadAcquire();
    if (dispatcher)
        dispatcher->wakeUp();
网上基本上讲到这里，也就结束了，post Event由于是异步事件，很多都说和操作系统有关，这是对的，但是，还没有往下深纠，
下面我往下进行深入的考察：
QAbstractEventDispatcher，大家注意到这个类，这个类是一个抽象类，他是一个指针，指向的肯定是派生类。
他的派生类是什么呢？，他的派生类和平台相关，对于win下，他的派生类是QEventDispatcherWin32
这在QCore Application，就会创建，createEventDispatcher（），可以查看下这个里面的代码，

void QEventDispatcherWin32::wakeUp()
{
    Q_D(QEventDispatcherWin32);
    d->serialNumber.ref();
    if (d->internalHwnd && d->wakeUps.testAndSetAcquire(0, 1)) {
        // post a WM_QT_SENDPOSTEDEVENTS to this thread if there isn‘t one already pending
        PostMessage(d->internalHwnd, WM_QT_SENDPOSTEDEVENTS, 0, 0);
    }
}
这里里面调用的是PostMessage，这个是win32的标准函数，这个就把消息添加到，win32的消息列队里面去了。
到这里大家也许就不知道怎么办了，下面是什么呢？
别忘了，回掉函数，最终要通过回掉函数，来处理消息的。
LRESULT QT_WIN_CALLBACK qt_internal_proc(HWND hwnd, UINT message, WPARAM wp, LPARAM lp)
{
    if (message == WM_NCCREATE)
        return true;

    MSG msg;
    msg.hwnd = hwnd;
    msg.message = message;
    msg.wParam = wp;
    msg.lParam = lp;
    QAbstractEventDispatcher* dispatcher = QAbstractEventDispatcher::instance();
    long result;
    if (!dispatcher) {
        if (message == WM_TIMER)
            KillTimer(hwnd, wp);
        return 0;
    } else if (dispatcher->filterNativeEvent(QByteArrayLiteral("windows_dispatcher_MSG"), &msg, &result)) {
        return result;
    }

#ifdef GWLP_USERDATA
    QEventDispatcherWin32 *q = (QEventDispatcherWin32 *) GetWindowLongPtr(hwnd, GWLP_USERDATA);
#else
    QEventDispatcherWin32 *q = (QEventDispatcherWin32 *) GetWindowLong(hwnd, GWL_USERDATA);
#endif
    QEventDispatcherWin32Private *d = 0;
    if (q != 0)
        d = q->d_func();

    if (message == WM_QT_SOCKETNOTIFIER) {
        // socket notifier message
        int type = -1;
        switch (WSAGETSELECTEVENT(lp)) {
        case FD_READ:
        case FD_ACCEPT:
            type = 0;
            break;
        case FD_WRITE:
        case FD_CONNECT:
            type = 1;
            break;
        case FD_OOB:
            type = 2;
            break;
        case FD_CLOSE:
            type = 3;
            break;
        }
        if (type >= 0) {
            Q_ASSERT(d != 0);
            QSNDict *sn_vec[4] = { &d->sn_read, &d->sn_write, &d->sn_except, &d->sn_read };
            QSNDict *dict = sn_vec[type];

            QSockNot *sn = dict ? dict->value(wp) : 0;
            if (sn) {
#ifndef Q_OS_WINCE
                d->doWsaAsyncSelect(sn->fd, 0);
                d->active_fd[sn->fd].selected = false;
                d->postActivateSocketNotifiers();
#endif
                if (type < 3) {
                    QEvent event(QEvent::SockAct);
                    QCoreApplication::sendEvent(sn->obj, &event);
                } else {
                    QEvent event(QEvent::SockClose);
                    QCoreApplication::sendEvent(sn->obj, &event);
                }
            }
        }
        return 0;
#ifndef Q_OS_WINCE
    } else if (message == WM_QT_ACTIVATENOTIFIERS) {
        Q_ASSERT(d != 0);

        // register all socket notifiers
        for (QSFDict::iterator it = d->active_fd.begin(), end = d->active_fd.end();
             it != end; ++it) {
            QSockFd &sd = it.value();
            if (!sd.selected) {
                d->doWsaAsyncSelect(it.key(), sd.event);
                sd.selected = true;
            }
        }
        d->activateNotifiersPosted = false;
        return 0;
#endif // !Q_OS_WINCE
    } else if (message == WM_QT_SENDPOSTEDEVENTS
               // we also use a Windows timer to send posted events when the message queue is full
               || (message == WM_TIMER
                   && d->sendPostedEventsWindowsTimerId != 0
                   && wp == (uint)d->sendPostedEventsWindowsTimerId)) {
        const int localSerialNumber = d->serialNumber.load();
        if (localSerialNumber != d->lastSerialNumber) {
            d->lastSerialNumber = localSerialNumber;
            q->sendPostedEvents();
        }
        return 0;
    } else if (message == WM_TIMER) {
        Q_ASSERT(d != 0);
        d->sendTimerEvent(wp);
        return 0;
    }

    return DefWindowProc(hwnd, message, wp, lp);
}

最终通过回掉函数处理消息，回掉函数中调用sendPostedEvents，或者是sendEvent，而sendPostedEvents，最终调用会通过
QCore Application：：sendPostedEvents（）；调用而这个有用到了sendEvent。
而大家都知道sendEvent是同步的。
这就是postEvent的整个过程

http://www.qtcn.org/bbs/apps.php?q=diary&uid=177993&a=detail&did=2356

QT5的post Event解析

标签：通过   cal   查看   oid   except   机制   when   异步   async   

原文地址：http://www.cnblogs.com/findumars/p/6413821.html