QWT oscilloscope example help

[Tamis2018]

QWT oscilloscope example - wheelbox.cpp. Please see code bellow. I could not understand that. That means that whenever I scroll the
mouse it will, generate QEvent::Wheel, then event will be modified only with QPoint( 5, 5 )
(possibly to put mouse on 5,5 coordinate? After the event will be sent to this object which is Wheel class instance? Why?

virtual bool eventFilter( QObject *object, QEvent *event )

{

    if ( event->type() == QEvent::Wheel )

    {

        QWheelEvent *we = ( QWheelEvent * )event

        QWheelEvent wheelEvent( QPoint( 5, 5 ), we->delta(),

            we->buttons(), we->modifiers(),

            we->orientation() );

        QApplication::sendEvent( this, &wheelEvent );

        return true;

    }

    return QwtWheel::eventFilter( object, event );
}

};

[Tamis2018]

Exactly, why we have to include this:

QWheelEvent wheelEvent( QPoint( 5, 5 ), we->delta(),

            we->buttons(), we->modifiers(),

            we->orientation() );

QPoint( 5, 5 ) is pos or global pos?

What is pixelDelta? What does mean that it contains the scrolling distance in pixels
on screen?