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, 46 insertions, 14 deletions

diff --git a/src/corelib/kernel/qwineventnotifier.cpp b/src/corelib/kernel/qwineventnotifier.cpp
index 0808374a6a..6bfa6ca729 100644
--- a/src/corelib/kernel/qwineventnotifier.cpp
+++ b/src/corelib/kernel/qwineventnotifier.cpp
@@ -37,7 +37,7 @@
 **
 ****************************************************************************/
 
-#include "qwineventnotifier.h"
+#include "qwineventnotifier_p.h"
 
 #ifdef Q_OS_WINRT
 #include "qeventdispatcher_winrt_p.h"
@@ -50,19 +50,6 @@
 
 QT_BEGIN_NAMESPACE
 
-class QWinEventNotifierPrivate : public QObjectPrivate
-{
-    Q_DECLARE_PUBLIC(QWinEventNotifier)
-public:
-    QWinEventNotifierPrivate()
-    : handleToEvent(0), enabled(false) {}
-    QWinEventNotifierPrivate(HANDLE h, bool e)
-    : handleToEvent(h), enabled(e) {}
-
-    HANDLE handleToEvent;
-    bool enabled;
-};
-
 /*!
     \class QWinEventNotifier
     \inmodule QtCore
@@ -246,4 +233,49 @@ bool QWinEventNotifier::event(QEvent * e)
     return false;
 }
 
+#if defined(Q_OS_WINRT)
+
+bool QWinEventNotifierPrivate::registerWaitObject()
+{
+    Q_UNIMPLEMENTED();
+    return false;
+}
+
+void QWinEventNotifierPrivate::unregisterWaitObject()
+{
+    Q_UNIMPLEMENTED();
+}
+
+#else // defined(Q_OS_WINRT)
+
+static void CALLBACK wfsoCallback(void *context, BOOLEAN /*ignore*/)
+{
+    QWinEventNotifierPrivate *nd = reinterpret_cast<QWinEventNotifierPrivate *>(context);
+    QAbstractEventDispatcher *eventDispatcher = nd->threadData->eventDispatcher.load();
+    QEventDispatcherWin32Private *edp = QEventDispatcherWin32Private::get(
+                static_cast<QEventDispatcherWin32 *>(eventDispatcher));
+    SetEvent(edp->winEventNotifierActivatedEvent);
+}
+
+bool QWinEventNotifierPrivate::registerWaitObject()
+{
+    if (RegisterWaitForSingleObject(&waitHandle, handleToEvent, wfsoCallback, this,
+                                    INFINITE, WT_EXECUTEONLYONCE) == 0) {
+        qErrnoWarning("QWinEventNotifier: RegisterWaitForSingleObject failed.");
+        return false;
+    }
+    return true;
+}
+
+void QWinEventNotifierPrivate::unregisterWaitObject()
+{
+    // Unregister the wait handle and wait for pending callbacks to finish.
+    if (UnregisterWaitEx(waitHandle, INVALID_HANDLE_VALUE))
+        waitHandle = NULL;
+    else
+        qErrnoWarning("QWinEventNotifier: UnregisterWaitEx failed.");
+}
+
+#endif // !defined(Q_OS_WINRT)
+
 QT_END_NAMESPACE