parent() heirarchy misunderstanding?

[marcel]

The parent of all subwindows in a mdi area is QMdiArea::viewport(). This is inherited from abstract scroll area.
The viewport is a QWidget so you should write the cast accordingly.

[KShots]

Thanks, I was able to replace that with a simple

static_cast<formMainWindow *>(parent()->parent()->parent()->parent())->subWindowDestroyed(this);

static_cast<formMainWindow *>(parent()->parent()->parent()->parent())->subWindowDestroyed(this);

To copy to clipboard, switch view to plain text mode 

within the closeEvent(QCloseEvent *) of the subwindow (to clean up before the thing is actually destroyed).