大家都知道，QT的事件機制，查了好多網上的帖子，分析的不夠到位，今天給大家分享下，我的分析，請高手指正：
都知道post Event通過
QScopedPointer<QEvent> eventDeleter(event);
//增加到事件隊列
data->postEventList.addEvent(QPostEvent(receiver, event, priority));
eventDeleter.take();
event->posted = true;
++receiver->d_func()->postedEvents;
data->canWait = false;
locker.unlock();
//事件分發
QAbstractEventDispatcher* dispatcher = data->eventDispatcher.loadAcquire();
if (dispatcher)
dispatcher->wakeUp();
網上基本上講到這里，也就結束了，post Event由於是異步事件，很多都說和操作系統有關，這是對的，但是，還沒有往下深糾，
下面我往下進行深入的考察：
QAbstractEventDispatcher，大家注意到這個類，這個類是一個抽象類，他是一個指針，指向的肯定是派生類。
他的派生類是什么呢？，他的派生類和平台相關，對於win下，他的派生類是QEventDispatcherWin32
這在QCore Application，就會創建，createEventDispatcher（），可以查看下這個里面的代碼，
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);
}
}
這里里面調用的是PostMessage，這個是win32的標准函數，這個就把消息添加到，win32的消息列隊里面去了。
到這里大家也許就不知道怎么辦了，下面是什么呢？
別忘了，回掉函數，最終要通過回掉函數，來處理消息的。
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);
}
最終通過回掉函數處理消息，回掉函數中調用sendPostedEvents，或者是sendEvent，而sendPostedEvents，最終調用會通過
QCore Application：：sendPostedEvents（）；調用而這個有用到了sendEvent。
而大家都知道sendEvent是同步的。
這就是postEvent的整個過程
http://www.qtcn.org/bbs/apps.php?q=diary&uid=177993&a=detail&did=2356