4 files changed, 21 insertions, 3 deletions
diff --git a/src/gui/kernel/qeventdispatcher_glib_lite.cpp b/src/gui/kernel/qeventdispatcher_glib_lite.cpp
index 0cfea8a..744925c 100644
--- a/src/gui/kernel/qeventdispatcher_glib_lite.cpp
+++ b/src/gui/kernel/qeventdispatcher_glib_lite.cpp
@@ -79,6 +79,8 @@ static gboolean userEventSourceDispatch(GSource *s, GSourceFunc, gpointer)
     QWindowSystemInterface::UserEvent * event;
     while (QWindowSystemInterfacePrivate::userEventsQueued()) {
         event = QWindowSystemInterfacePrivate::getUserEvent();
+        if (!event)
+            break;
 
         // send through event filter
         if (source->q->filterEvent(event)) {
diff --git a/src/gui/kernel/qeventdispatcher_lite.cpp b/src/gui/kernel/qeventdispatcher_lite.cpp
index d500ad6..5b99a2f 100644
--- a/src/gui/kernel/qeventdispatcher_lite.cpp
+++ b/src/gui/kernel/qeventdispatcher_lite.cpp
@@ -89,6 +89,8 @@ bool QEventDispatcherLite::processEvents(QEventLoop::ProcessEventsFlags flags)
             && QWindowSystemInterfacePrivate::userEventsQueued() > 0) {
             // process a pending user input event
             event = QWindowSystemInterfacePrivate::getUserEvent();
+            if (!event)
+                break;
         } else {
             break;
         }
diff --git a/src/gui/kernel/qwindowsysteminterface.cpp b/src/gui/kernel/qwindowsysteminterface.cpp
index d7b5eef..05ca3d3 100644
--- a/src/gui/kernel/qwindowsysteminterface.cpp
+++ b/src/gui/kernel/qwindowsysteminterface.cpp
@@ -52,6 +52,7 @@ QTime QWindowSystemInterface::eventTime;
 //
 
 QList<QWindowSystemInterface::UserEvent *> QWindowSystemInterfacePrivate::userEventQueue;
+QMutex QWindowSystemInterfacePrivate::queueMutex;
 
 extern QPointer<QWidget> qt_last_mouse_receiver;
 /*!
@@ -109,4 +110,15 @@ void QWindowSystemInterface::handleWheelEvent(QWidget *tlw, ulong timestamp, con
     QWindowSystemInterfacePrivate::queueUserEvent(e);
 }
 
+QWindowSystemInterface::UserEvent * QWindowSystemInterfacePrivate::getUserEvent()
+{
+    queueMutex.lock();
+    QWindowSystemInterface::UserEvent *ret;
+    if (userEventQueue.isEmpty())
+        ret = 0;
+    else
+        ret = userEventQueue.takeFirst();
+    queueMutex.unlock();
+    return ret;
+}
 QT_END_NAMESPACE
diff --git a/src/gui/kernel/qwindowsysteminterface.h b/src/gui/kernel/qwindowsysteminterface.h
index 70b2830..d9bfc70 100644
--- a/src/gui/kernel/qwindowsysteminterface.h
+++ b/src/gui/kernel/qwindowsysteminterface.h
@@ -46,6 +46,7 @@
 #include <QtCore/QEvent>
 #include <QtGui/QWidget>
 #include <QtCore/QWeakPointer>
+#include <QtCore/QMutex>
 
 QT_BEGIN_HEADER
 
@@ -128,10 +129,11 @@ private:
 class QWindowSystemInterfacePrivate {
 public:
     static QList<QWindowSystemInterface::UserEvent *> userEventQueue;
+    static QMutex queueMutex;
 
-    static int userEventsQueued() { return userEventQueue.count(); }
-    static QWindowSystemInterface::UserEvent * getUserEvent() { return userEventQueue.takeFirst(); }
-    static void queueUserEvent(QWindowSystemInterface::UserEvent *ev) { userEventQueue.append(ev); }
+    static int userEventsQueued() { queueMutex.lock(); int ret = userEventQueue.count(); queueMutex.unlock(); return ret; }
+    static QWindowSystemInterface::UserEvent * getUserEvent();
+    static void queueUserEvent(QWindowSystemInterface::UserEvent *ev) { queueMutex.lock(); userEventQueue.append(ev); queueMutex.unlock(); }
 };
 
 QT_END_NAMESPACE