bool Gui::GUIApplicationNativeEventAware::x11EventFilter(XEvent *event)
{
#ifdef SPNAV_FOUND
    spnav_event navEvent;
    if (!spnav_x11_event(event, &navEvent))
        return false;

    QWidget *currentWidget = this->focusWidget();
    if (!currentWidget)
        currentWidget = mainWindow;

    if (navEvent.type == SPNAV_EVENT_MOTION)
    {
        motionDataArray[0] = navEvent.motion.x;
        motionDataArray[1] = navEvent.motion.y;
        motionDataArray[2] = navEvent.motion.z;
        motionDataArray[3] = navEvent.motion.rx;
        motionDataArray[4] = navEvent.motion.ry;
        motionDataArray[5] = navEvent.motion.rz;

        if (!setOSIndependentMotionData()) return false;
        importSettings();

        Spaceball::MotionEvent *motionEvent = new Spaceball::MotionEvent();

        motionEvent->setTranslations(motionDataArray[0], motionDataArray[1], motionDataArray[2]);
        motionEvent->setRotations(motionDataArray[3], motionDataArray[4], motionDataArray[5]);

        this->postEvent(currentWidget, motionEvent);
        return true;
    }

    if (navEvent.type == SPNAV_EVENT_BUTTON)
    {
        Spaceball::ButtonEvent *buttonEvent = new Spaceball::ButtonEvent();
        buttonEvent->setButtonNumber(navEvent.button.bnum);
        if (navEvent.button.press)
            buttonEvent->setButtonStatus(Spaceball::BUTTON_PRESSED);
        else
            buttonEvent->setButtonStatus(Spaceball::BUTTON_RELEASED);
        this->postEvent(currentWidget, buttonEvent);
        return true;
    }

    Base::Console().Log("Unknown spaceball event\n");
    return true;
#else
    return false;
#endif // SPNAV_FOUND
}
bool Gui::GUIApplicationNativeEventAware::x11EventFilter(XEvent *event)
{
#ifdef SPNAV_FOUND
    /*
    First we check if we have a motion flush event:
    - If there are unprocessed motion events we are in a flooding situation.
      In that case we wait with generating a Spaceball event.
    - A motion event counter of 0 indicates that FreeCAD is ready to process
      the event. A Spaceball event, using the saved motion data, is posted.
    */
    static Display* display = QX11Info::display();
    static Atom motion_flush_event = XInternAtom(display, "FCMotionFlushEvent", false);
    static int nMotionEvents = 0;

    QWidget *currentWidget = this->focusWidget();
    if (!currentWidget)
        currentWidget = mainWindow;

    if (event->type == ClientMessage)
    {
        Atom message_type = event->xclient.message_type;
        
        if (message_type == motion_flush_event)
        {
            nMotionEvents--;
            if (nMotionEvents == 0)
            {
                importSettings();
                
                Spaceball::MotionEvent *motionEvent = new Spaceball::MotionEvent();
                
                motionEvent->setTranslations(motionDataArray[0], motionDataArray[1], motionDataArray[2]);
                motionEvent->setRotations(motionDataArray[3], motionDataArray[4], motionDataArray[5]);

                this->postEvent(currentWidget, motionEvent);
            }
            
            return true;
        } // XEvent: motion_flush_event
    } // XEvent: ClientMessage

    /*
    From here on we deal with spacenav events only:
    - motion: The event data is saved and a self addressed flush event
              is sent through the window system (XEvent). 
              In the case of an event flooding, the motion data is added up.
    - button: A Spaceball event is posted (QInputEvent).
    */
    spnav_event navEvent;
    if (!spnav_x11_event(event, &navEvent))
        return false;

    if (navEvent.type == SPNAV_EVENT_MOTION)
    {
        /*
        If the motion data of the preceding event has not been processed
        through posting an Spaceball event (flooding situation), 
        the motion data provided by the incoming event is added to the saved data. 
        */
    	int dx, dy, dz, drx, dry, drz;

        if (nMotionEvents == 0)
        {
            dx = 0;
            dy = 0;
            dz = 0;
            drx = 0;
            dry = 0;
            drz = 0;
        }
        else
        {
            dx = motionDataArray[0];
            dy = motionDataArray[1];
            dz = motionDataArray[2];
            drx = motionDataArray[3];
            dry = motionDataArray[4];
            drz = motionDataArray[5];
        }
        
        motionDataArray[0] = navEvent.motion.x;
        motionDataArray[1] = navEvent.motion.y;
        motionDataArray[2] = navEvent.motion.z;
        motionDataArray[3] = navEvent.motion.rx;
        motionDataArray[4] = navEvent.motion.ry;
        motionDataArray[5] = navEvent.motion.rz;

        if (!setOSIndependentMotionData()) return false;
        
        motionDataArray[0] += dx;
        motionDataArray[1] += dy;
        motionDataArray[2] += dz;
        motionDataArray[3] += drx;
        motionDataArray[4] += dry;
        motionDataArray[5] += drz;
        
        /*
        Send a self addressed flush event through the window system. This will
        trigger a Spaceball event if FreeCAD is ready to do so.
        */
        nMotionEvents++;
        XClientMessageEvent flushEvent;
        
        flushEvent.display = display;
        flushEvent.window = event->xclient.window;
        flushEvent.type = ClientMessage;
        flushEvent.format = 8;    
        flushEvent.message_type = motion_flush_event;
        
        XSendEvent (display, flushEvent.window, False, 0, (XEvent*)&flushEvent); // siehe spnavd, False, 0
        
        return true;
    }

    if (navEvent.type == SPNAV_EVENT_BUTTON)
    {
        Spaceball::ButtonEvent *buttonEvent = new Spaceball::ButtonEvent();
        buttonEvent->setButtonNumber(navEvent.button.bnum);
        if (navEvent.button.press)
            buttonEvent->setButtonStatus(Spaceball::BUTTON_PRESSED);
        else
            buttonEvent->setButtonStatus(Spaceball::BUTTON_RELEASED);
        this->postEvent(currentWidget, buttonEvent);
        return true;
    }

    Base::Console().Log("Unknown spaceball event\n");
    return true;
#else
    return false;
#endif // SPNAV_FOUND
}