Fix QWinEventNotifier for auto-reset events

Auto-reset events are automatically reset to non-signaled when we get
notified about the signaled state. This implies that we cannot check the
event state again in activateEventNotifiers. Instead, store the signaled
state in a QAtomicInt and test and decrement that.

This amends commit 85403d0a.

Task-number: QTBUG-63555
Change-Id: I0adee3d2929783f98d91060f9106c8b5266d72fa
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/corelib/kernel/qeventdispatcher_win.cpp

@@ -942,7 +942,8 @@ void QEventDispatcherWin32::activateEventNotifiers()
     for (int i = d->winEventNotifierList.count(); --i >= 0;) {
         QWinEventNotifier *notifier = d->winEventNotifierList.at(i);
         QWinEventNotifierPrivate *nd = QWinEventNotifierPrivate::get(notifier);
-        if (WaitForSingleObject(nd->handleToEvent, 0) == WAIT_OBJECT_0) {
+        if (nd->signaledCount.load() != 0) {
+            --nd->signaledCount;
             nd->unregisterWaitObject();
             d->activateEventNotifier(notifier);
         }

src/corelib/kernel/qwineventnotifier.cpp

@@ -157,6 +157,7 @@ void QWinEventNotifier::setHandle(HANDLE hEvent)
     Q_D(QWinEventNotifier);
     setEnabled(false);
     d->handleToEvent = hEvent;
+    d->signaledCount = 0;
 }
 
 /*!
@@ -254,6 +255,7 @@ static void CALLBACK wfsoCallback(void *context, BOOLEAN /*ignore*/)
     QAbstractEventDispatcher *eventDispatcher = nd->threadData->eventDispatcher.load();
     QEventDispatcherWin32Private *edp = QEventDispatcherWin32Private::get(
                 static_cast<QEventDispatcherWin32 *>(eventDispatcher));
+    ++nd->signaledCount;
     SetEvent(edp->winEventNotifierActivatedEvent);
 }
 

src/corelib/kernel/qwineventnotifier_p.h

@@ -54,6 +54,7 @@
 #include "qwineventnotifier.h"
 
 #include <private/qobject_p.h>
+#include <QtCore/qatomic.h>
 #include <QtCore/qt_windows.h>
 
 QT_BEGIN_NAMESPACE
@@ -73,6 +74,7 @@ public:
 
     HANDLE handleToEvent;
     HANDLE waitHandle = NULL;
+    QAtomicInt signaledCount;
     bool enabled;
 };
 

tests/auto/corelib/kernel/qwineventnotifier/tst_qwineventnotifier.cpp

@@ -41,6 +41,7 @@ protected slots:
     void simple_activated();
     void simple_timerSet();
 private slots:
+    void simple_data();
     void simple();
     void manyNotifiers();
 
@@ -61,9 +62,17 @@ void tst_QWinEventNotifier::simple_timerSet()
     SetEvent((HANDLE)simpleHEvent);
 }
 
+void tst_QWinEventNotifier::simple_data()
+{
+    QTest::addColumn<bool>("resetManually");
+    QTest::newRow("manual_reset") << true;
+    QTest::newRow("auto_reset") << false;
+}
+
 void tst_QWinEventNotifier::simple()
 {
-    simpleHEvent = CreateEvent(0, true, false, 0);
+    QFETCH(bool, resetManually);
+    simpleHEvent = CreateEvent(0, resetManually, false, 0);
     QVERIFY(simpleHEvent);
 
     QWinEventNotifier n(simpleHEvent);