Avoid activate & focus when clicking on window

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    QWidget *qw = new QWidget();

    qw->setFocusPolicy(Qt::NoFocus);
    qw->setAttribute(Qt::WA_ShowWithoutActivating);

    QPushButton *but = new QPushButton("hello",qw);

    qw->show();
    but->show();

    connect(but,SIGNAL(clicked()),this,SLOT(ev()));
}