void ShapedClock::mousePressEvent(QMouseEvent *event) {

    if (event->button() == Qt::LeftButton) {

        dragPosition = event->globalPos() - frameGeometry().topLeft();

        event->accept();

    }

}

void ShapedClock::mouseMoveEvent(QMouseEvent *event) {

    if (event->buttons() & Qt::LeftButton) {

        move(event->globalPos() - dragPosition);

        event->accept();

    }

}

const QPoint & QMouseEvent::globalPos () const

Returns the global position of the mouse cursor at the time of the event. This is important on asynchronous window systems like X11. Whenever you move your widgets around in response to mouse events, globalPos() may differ a lot from the current pointer position QCursor::pos(), and from QWidget::mapToGlobal(pos()).

QPoint QWidget::mapToGlobal ( const QPoint & pos ) const

Translates the widget coordinate pos to global screen coordinates. For example, mapToGlobal(QPoint(0,0)) would give the global coordinates of the top-left pixel of the widget.

QPoint QWidget::mapFromGlobal ( const QPoint & pos ) const

Translates the global screen coordinate pos to widget coordinates.