Support more than 62 instances of QWinEventNotifier

QWinEventNotifiers were limited to 62 instances, because of
WaitForMultipleObject's limitation to MAXIMUM_WAIT_OBJECTS - 1 handles.

Use the RegisterWaitForSingleObject API which does not have this
restriction and executes waits in threads managed by the system. A
central manual reset event per event dispatcher is signaled in the
RegisterWaitForSingleObject callback and waited for in the event loop.

[ChangeLog][QtCore][QWinEventNotifier] QWinEventNotifier is not
restricted to 62 instances anymore.

Task-number: QTBUG-8819
Change-Id: I2c749951453a4b699cc50dada0d6017440b67a4a
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

1 files changed, 88 insertions, 0 deletions

diff --git a/tests/auto/corelib/kernel/qwineventnotifier/tst_qwineventnotifier.cpp b/tests/auto/corelib/kernel/qwineventnotifier/tst_qwineventnotifier.cpp
index 3221587300..304f6121a5 100644
--- a/tests/auto/corelib/kernel/qwineventnotifier/tst_qwineventnotifier.cpp
+++ b/tests/auto/corelib/kernel/qwineventnotifier/tst_qwineventnotifier.cpp
@@ -31,6 +31,8 @@
 #include <qtimer.h>
 #include <qt_windows.h>
 
+#include <memory>
+
 class tst_QWinEventNotifier : public QObject
 {
     Q_OBJECT
@@ -40,6 +42,7 @@ protected slots:
     void simple_timerSet();
 private slots:
     void simple();
+    void manyNotifiers();
 
 private:
     HANDLE simpleHEvent;
@@ -87,6 +90,91 @@ void tst_QWinEventNotifier::simple()
     QVERIFY(simpleActivated);
 }
 
+class EventWithNotifier : public QObject
+{
+    Q_OBJECT
+public:
+    EventWithNotifier()
+    {
+        connect(&notifier, &QWinEventNotifier::activated,
+                this, &EventWithNotifier::onNotifierActivated);
+        notifier.setHandle(CreateEvent(0, TRUE, FALSE, 0));
+        notifier.setEnabled(true);
+
+        static int nextIndex = 0;
+        idx = nextIndex++;
+    }
+
+    ~EventWithNotifier()
+    {
+        notifier.setEnabled(false);
+        CloseHandle(notifier.handle());
+    }
+
+    HANDLE eventHandle() const { return notifier.handle(); }
+    int numberOfTimesActivated() const { return activatedCount; }
+
+signals:
+    void activated();
+
+public slots:
+    void onNotifierActivated()
+    {
+        ResetEvent(notifier.handle());
+        activatedCount++;
+        emit activated();
+    }
+
+private:
+    QWinEventNotifier notifier;
+    int activatedCount = 0;
+    int idx = 0;
+};
+
+void tst_QWinEventNotifier::manyNotifiers()
+{
+    const size_t maxEvents = 100;
+    const size_t middleEvenEvent = maxEvents / 2;
+    Q_ASSERT(middleEvenEvent % 2 == 0);
+    using EventWithNotifierPtr = std::unique_ptr<EventWithNotifier>;
+    std::vector<EventWithNotifierPtr> events(maxEvents);
+    std::generate(events.begin(), events.end(), [] () {
+        return EventWithNotifierPtr(new EventWithNotifier);
+    });
+
+    QTestEventLoop loop;
+    auto connection = connect(events.at(8).get(), &EventWithNotifier::activated, &loop, &QTestEventLoop::exitLoop);
+    for (const auto &ewn : events) {
+        connect(ewn.get(), &EventWithNotifier::activated, [&events, &loop] () {
+            if (std::all_of(events.cbegin(), events.cend(),
+                    [] (const EventWithNotifierPtr &ewn) {
+                            return ewn->numberOfTimesActivated() > 0; })) {
+                loop.exitLoop();
+            }
+        });
+    }
+
+    // Activate all even events before running the event loop.
+    for (size_t i = 0; i < events.size(); i += 2)
+        SetEvent(events.at(i)->eventHandle());
+
+    // Wait until event notifier with index 8 has been activated.
+    loop.enterLoop(30);
+    QObject::disconnect(connection);
+
+    // Activate all odd events after the event loop has run for a bit.
+    for (size_t i = 1; i < events.size(); i += 2)
+        SetEvent(events.at(i)->eventHandle());
+
+    // Wait until all event notifiers have fired.
+    loop.enterLoop(30);
+
+    // All notifiers must have been activated exactly once.
+    QVERIFY(std::all_of(events.cbegin(), events.cend(), [] (const EventWithNotifierPtr &ewn) {
+        return ewn->numberOfTimesActivated() == 1;
+    }));
+}
+
 QTEST_MAIN(tst_QWinEventNotifier)
 
 #include "tst_qwineventnotifier.moc"