[Qt-interest] Screen coordinates in QGraphicsItem::hoverEnterEvent() ?

[bd.anon at free.fr]

In QGraphicsItem::hoverEnterEvent(), I would like to make use of
QToolTip::showText(const QPoint & pos, const QString & text, QWidget *
w, const QRect & rect).

My application may use several main windows, which as a consequence
could potentially have different views on the same Scene.

How from QGraphicsItem::hoverEnterEvent() do I determine the screen
coordinates required by rect in QToolTip::showText, given that I do
not know which screen / viewport generated the QGraphicsItem
hoverEnter Event ?

Am I missing something ?

Thanks for any pointer or code snippet.