C++ (Qt)
DockWidgets::DockWidgets(QWidget *parent)
    : QMainWindow(parent)
{
	ui.setupUi(this);
	QList <QDockWidget *> lst = findChildren<QDockWidget *>();
	foreach(QDockWidget *widget, lst)
	{
	    connect(widget, SIGNAL(visibilityChanged(bool)), SLOT(slotVisibilityChanged(bool)));
	}
}
void DockWidgets::slotVisibilityChanged(bool visible)
{
    QObject *sndr = sender();
    if (sndr)
    {
        sndr->setProperty("dockIsVisible", visible);
    }
}