QEventDispatcherWin32: create internal window on construction

When QCoreApplication object is instantiated, creation of the internal
message window is delayed until QEventDispatcherWin32::processEvents()
is called or socket/event notifier is registered. But, if the user uses
a native event loop, posted events are not delivered and timers do not
work.

This problem was fixed in a4ac4b326318ed9034466305222280ed8d1651b5 for
QWindowsGuiEventDispatcher in the same way. So, the risk of regression
is minimal.

Change-Id: I7bbb721d96046f64d21a7b0e553e46798b37189c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/corelib/kernel/qeventdispatcher_win.cpp

@@ -411,7 +411,7 @@ void QEventDispatcherWin32Private::unregisterTimer(WinTimerInfo *t)
     } else if (t->fastTimerId != 0) {
         timeKillEvent(t->fastTimerId);
         QCoreApplicationPrivate::removePostedTimerEvent(t->dispatcher, t->timerId);
-    } else if (internalHwnd) {
+    } else {
         KillTimer(internalHwnd, t->timerId);
     }
     t->timerId = -1;
@@ -463,12 +463,16 @@ void QEventDispatcherWin32Private::postActivateEventNotifiers()
         QCoreApplication::postEvent(q, new QEvent(QEvent::WinEventAct));
 }
 
-void QEventDispatcherWin32::createInternalHwnd()
+QEventDispatcherWin32::QEventDispatcherWin32(QObject *parent)
+    : QEventDispatcherWin32(*new QEventDispatcherWin32Private, parent)
+{
+}
+
+QEventDispatcherWin32::QEventDispatcherWin32(QEventDispatcherWin32Private &dd, QObject *parent)
+    : QAbstractEventDispatcher(dd, parent)
 {
     Q_D(QEventDispatcherWin32);
 
-    if (d->internalHwnd)
-        return;
     d->internalHwnd = qt_create_internal_window(this);
 
     // setup GetMessage hook needed to drive our posted events
@@ -478,21 +482,8 @@ void QEventDispatcherWin32::createInternalHwnd()
         qFatal("Qt: INTERNAL ERROR: failed to install GetMessage hook: %d, %ls",
                errorCode, qUtf16Printable(qt_error_string(errorCode)));
     }
-
-    // start all normal timers
-    for (int i = 0; i < d->timerVec.count(); ++i)
-        d->registerTimer(d->timerVec.at(i));
 }
 
-QEventDispatcherWin32::QEventDispatcherWin32(QObject *parent)
-    : QAbstractEventDispatcher(*new QEventDispatcherWin32Private, parent)
-{
-}
-
-QEventDispatcherWin32::QEventDispatcherWin32(QEventDispatcherWin32Private &dd, QObject *parent)
-    : QAbstractEventDispatcher(dd, parent)
-{ }
-
 QEventDispatcherWin32::~QEventDispatcherWin32()
 {
 }
@@ -517,11 +508,6 @@ bool QEventDispatcherWin32::processEvents(QEventLoop::ProcessEventsFlags flags)
 {
     Q_D(QEventDispatcherWin32);
 
-    if (!d->internalHwnd) {
-        createInternalHwnd();
-        wakeUp(); // trigger a call to sendPostedEvents()
-    }
-
     d->interrupt.storeRelaxed(false);
     emit awake();
 
@@ -642,8 +628,6 @@ void QEventDispatcherWin32::registerSocketNotifier(QSocketNotifier *notifier)
                  "same socket %d and type %s", sockfd, t[type]);
     }
 
-    createInternalHwnd();
-
     QSockNot *sn = new QSockNot;
     sn->obj = notifier;
     sn->fd  = sockfd;
@@ -752,8 +736,7 @@ void QEventDispatcherWin32::registerTimer(int timerId, int interval, Qt::TimerTy
     t->inTimerEvent = false;
     t->fastTimerId = 0;
 
-    if (d->internalHwnd)
-        d->registerTimer(t);
+    d->registerTimer(t);
 
     d->timerVec.append(t);                      // store in timer vector
     d->timerDict.insert(t->timerId, t);          // store timers in dict
@@ -849,8 +832,6 @@ bool QEventDispatcherWin32::registerEventNotifier(QWinEventNotifier *notifier)
     if (d->winEventNotifierList.contains(notifier))
         return true;
 
-    createInternalHwnd();
-
     d->winEventNotifierList.append(notifier);
     d->winEventNotifierListModified = true;
 
@@ -933,10 +914,7 @@ int QEventDispatcherWin32::remainingTime(int timerId)
         if (t && t->timerId == timerId) {
             // timer found, return time to wait
 
-            if (d->internalHwnd)
-                return t->timeout > currentTime ? t->timeout - currentTime : 0;
-            else
-                return t->interval;
+            return t->timeout > currentTime ? t->timeout - currentTime : 0;
         }
     }
 
@@ -950,7 +928,7 @@ int QEventDispatcherWin32::remainingTime(int timerId)
 void QEventDispatcherWin32::wakeUp()
 {
     Q_D(QEventDispatcherWin32);
-    if (d->internalHwnd && d->wakeUps.testAndSetRelaxed(0, 1)) {
+    if (d->wakeUps.testAndSetRelaxed(0, 1)) {
         // post a WM_QT_SENDPOSTEDEVENTS to this thread if there isn't one already pending
         if (!PostMessage(d->internalHwnd, WM_QT_SENDPOSTEDEVENTS, 0, 0))
             qErrnoWarning("QEventDispatcherWin32::wakeUp: Failed to post a message");
@@ -1056,9 +1034,7 @@ void QEventDispatcherWin32::sendPostedEvents()
 
 HWND QEventDispatcherWin32::internalHwnd()
 {
-    Q_D(QEventDispatcherWin32);
-    createInternalHwnd();
-    return d->internalHwnd;
+    return d_func()->internalHwnd;
 }
 
 QT_END_NAMESPACE

src/corelib/kernel/qeventdispatcher_win_p.h

@@ -72,9 +72,6 @@ class Q_CORE_EXPORT QEventDispatcherWin32 : public QAbstractEventDispatcher
     Q_OBJECT
     Q_DECLARE_PRIVATE(QEventDispatcherWin32)
 
-protected:
-    void createInternalHwnd();
-
 public:
     explicit QEventDispatcherWin32(QObject *parent = 0);
     ~QEventDispatcherWin32();

src/gui/platform/windows/qwindowsguieventdispatcher.cpp

@@ -63,7 +63,6 @@ QWindowsGuiEventDispatcher::QWindowsGuiEventDispatcher(QObject *parent) :
     QEventDispatcherWin32(parent)
 {
     setObjectName(QStringLiteral("QWindowsGuiEventDispatcher"));
-    createInternalHwnd(); // QTBUG-40881: Do not delay registering timers, etc. for QtMfc.
 }
 
 bool QWindowsGuiEventDispatcher::processEvents(QEventLoop::ProcessEventsFlags flags)

tests/auto/corelib/kernel/qcoreapplication/tst_qcoreapplication.cpp

@@ -36,6 +36,10 @@
 #include <private/qeventloop_p.h>
 #include <private/qthread_p.h>
 
+#ifdef Q_OS_WIN
+#include <QtCore/qt_windows.h>
+#endif
+
 typedef QCoreApplication TestApplication;
 
 class EventSpy : public QObject
@@ -617,6 +621,42 @@ void tst_QCoreApplication::processEventsAlwaysSendsPostedEvents()
     } while (t.elapsed() < 1000);
 }
 
+#ifdef Q_OS_WIN
+void tst_QCoreApplication::sendPostedEventsInNativeLoop()
+{
+    int argc = 1;
+    char *argv[] = { const_cast<char*>(QTest::currentAppName()) };
+    TestApplication app(argc, argv);
+
+    bool signalReceived = false;
+
+    // Post a message to the queue
+    QMetaObject::invokeMethod(this, [&signalReceived]() {
+        signalReceived = true;
+    }, Qt::QueuedConnection);
+
+    QElapsedTimer elapsedTimer;
+    elapsedTimer.start();
+
+    // Exec own message loop
+    MSG msg;
+    forever {
+        if (elapsedTimer.hasExpired(3000) || signalReceived)
+            break;
+
+        if (!::PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
+            QThread::msleep(100);
+            continue;
+        }
+
+        ::TranslateMessage(&msg);
+        ::DispatchMessage(&msg);
+    }
+
+    QVERIFY(signalReceived);
+}
+#endif // Q_OS_WIN
+
 class QuitBlocker : public QObject
 {
    Q_OBJECT

tests/auto/corelib/kernel/qcoreapplication/tst_qcoreapplication.h

@@ -49,6 +49,9 @@ private slots:
     void applicationPid();
     void globalPostedEventsCount();
     void processEventsAlwaysSendsPostedEvents();
+#ifdef Q_OS_WIN
+    void sendPostedEventsInNativeLoop();
+#endif
     void quit();
     void reexec();
     void execAfterExit();