{

    if (event->type() == QEvent::MouseButtonPress ||

        event->type() == QEvent::MouseButtonRelease ||

        event->type() == QEvent::MouseMove)

    {

        QMouseEvent* mouseEvent = (QMouseEvent*) event;

        double pos = this->position(mouseEvent);

        double posPx = this->positionPx(mouseEvent);

        currentPosPx = posPx;

        if (event->type() == QEvent::MouseButtonPress &&

            mouseEvent->button() == Qt::LeftButton)

        {

            pressed = true; // not yet started

            firstPos = pos;

            firstPosPx = posPx;

        }

        else if (event->type() == QEvent::MouseMove)

        {

            // make sure pick size is big enough, so that just

            // clicking won't trigger pick

            if (!started && pressed && (fabs(posPx-firstPosPx) > MIN_PICK_SIZE))

            {

                started = true;

                emit pickStarted(pos);

            }

            else if (started)

            {

                pickerOverlay->updateOverlay();

                emit picking(firstPos, pos);

            }

            scaleOverlay->updateOverlay();

        }

        else // event->type() == QEvent::MouseButtonRelease

        {

            if (started)

            {

                // finalize

                started = false;

                pressed = false;

                emit picked(firstPos, pos);

            }

        }

        return true;

    }

    else

    {

        return QObject::eventFilter(object, event);