4 files changed, 36 insertions, 2 deletions
diff --git a/src/gui/kernel/qguiapplication.cpp b/src/gui/kernel/qguiapplication.cpp
index b8c6e4db20..1763624b83 100644
--- a/src/gui/kernel/qguiapplication.cpp
+++ b/src/gui/kernel/qguiapplication.cpp
@@ -1279,6 +1279,9 @@ void QGuiApplicationPrivate::processWindowSystemEvent(QWindowSystemInterfacePriv
     case QWindowSystemInterfacePrivate::ApplicationStateChanged:
             QGuiApplicationPrivate::processApplicationStateChangedEvent(static_cast<QWindowSystemInterfacePrivate::ApplicationStateChangedEvent *>(e));
         break;
+    case QWindowSystemInterfacePrivate::FlushEvents:
+        QWindowSystemInterface::deferredFlushWindowSystemEvents();
+        break;
     case QWindowSystemInterfacePrivate::Close:
         QGuiApplicationPrivate::processCloseEvent(
                 static_cast<QWindowSystemInterfacePrivate::CloseEvent *>(e));
diff --git a/src/gui/kernel/qwindowsysteminterface.cpp b/src/gui/kernel/qwindowsysteminterface.cpp
index 01100d8555..8c5a3bc215 100644
--- a/src/gui/kernel/qwindowsysteminterface.cpp
+++ b/src/gui/kernel/qwindowsysteminterface.cpp
@@ -54,6 +54,8 @@ QT_BEGIN_NAMESPACE
 
 QElapsedTimer QWindowSystemInterfacePrivate::eventTime;
 bool QWindowSystemInterfacePrivate::synchronousWindowsSystemEvents = false;
+QWaitCondition QWindowSystemInterfacePrivate::eventsFlushed;
+QMutex QWindowSystemInterfacePrivate::flushEventMutex;
 
 //------------------------------------------------------------
 //
@@ -514,9 +516,25 @@ void QWindowSystemInterface::handleExposeEvent(QWindow *tlw, const QRegion &regi
     QWindowSystemInterfacePrivate::handleWindowSystemEvent(e);
 }
 
+void QWindowSystemInterface::deferredFlushWindowSystemEvents()
+{
+    Q_ASSERT(QThread::currentThread() == QGuiApplication::instance()->thread());
+
+    QMutexLocker locker(&QWindowSystemInterfacePrivate::flushEventMutex);
+    flushWindowSystemEvents();
+    QWindowSystemInterfacePrivate::eventsFlushed.wakeOne();
+}
+
 void QWindowSystemInterface::flushWindowSystemEvents()
 {
-    sendWindowSystemEventsImplementation(QEventLoop::AllEvents);
+    if (QThread::currentThread() != QGuiApplication::instance()->thread()) {
+        QMutexLocker locker(&QWindowSystemInterfacePrivate::flushEventMutex);
+        QWindowSystemInterfacePrivate::FlushEventsEvent *e = new QWindowSystemInterfacePrivate::FlushEventsEvent();
+        QWindowSystemInterfacePrivate::handleWindowSystemEvent(e);
+        QWindowSystemInterfacePrivate::eventsFlushed.wait(&QWindowSystemInterfacePrivate::flushEventMutex);
+    } else {
+        sendWindowSystemEventsImplementation(QEventLoop::AllEvents);
+    }
 }
 
 bool QWindowSystemInterface::sendWindowSystemEvents(QEventLoop::ProcessEventsFlags flags)
diff --git a/src/gui/kernel/qwindowsysteminterface.h b/src/gui/kernel/qwindowsysteminterface.h
index 5668f3c0cf..22e5983a07 100644
--- a/src/gui/kernel/qwindowsysteminterface.h
+++ b/src/gui/kernel/qwindowsysteminterface.h
@@ -186,6 +186,7 @@ public:
     static bool sendWindowSystemEvents(QEventLoop::ProcessEventsFlags flags);
     static void setSynchronousWindowsSystemEvents(bool enable);
     static void flushWindowSystemEvents();
+    static void deferredFlushWindowSystemEvents();
     static int windowSystemEventsQueued();
 
 private:
diff --git a/src/gui/kernel/qwindowsysteminterface_p.h b/src/gui/kernel/qwindowsysteminterface_p.h
index 8336c3d63c..431b2cbe1e 100644
--- a/src/gui/kernel/qwindowsysteminterface_p.h
+++ b/src/gui/kernel/qwindowsysteminterface_p.h
@@ -58,6 +58,7 @@
 #include <QPointer>
 #include <QMutex>
 #include <QList>
+#include <QWaitCondition>
 
 QT_BEGIN_NAMESPACE
 
@@ -89,7 +90,8 @@ public:
         TabletLeaveProximity = UserInputEvent | 0x16,
         PlatformPanel = UserInputEvent | 0x17,
         ContextMenu = UserInputEvent | 0x18,
-        ApplicationStateChanged = 0x19
+        ApplicationStateChanged = 0x19,
+        FlushEvents = 0x20
     };
 
     class WindowSystemEvent {
@@ -162,6 +164,13 @@ public:
         Qt::ApplicationState newState;
     };
 
+    class FlushEventsEvent : public WindowSystemEvent {
+    public:
+        FlushEventsEvent()
+            : WindowSystemEvent(FlushEvents)
+        { }
+    };
+
     class UserEvent : public WindowSystemEvent {
     public:
         UserEvent(QWindow * w, ulong time, EventType t)
@@ -432,6 +441,9 @@ public:
     static QElapsedTimer eventTime;
     static bool synchronousWindowsSystemEvents;
 
+    static QWaitCondition eventsFlushed;
+    static QMutex flushEventMutex;
+
     static QList<QTouchEvent::TouchPoint> convertTouchPoints(const QList<QWindowSystemInterface::TouchPoint> &points, QEvent::Type *type);
 };