[Qt-interest] Where's QWidget::setBackgroundMode() ?

[Kermit]

Dear all, in Qt 4.7 Assistant, the QStyle's document says:

void QStyle::polish ( QWidget * widget ) [virtual]
Initializes the appearance of the given widget.
This function is called for every widget at some point after it has been
fully created but just before it is shown for the very first time.
Note that the default implementation does nothing. Reasonable actions in
this function might be to call the QWidget::setBackgroundMode() function
for the widget.  [... ...]         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
                                 


But I can't find QWidget::setBackgroundMode() in QWidget or its parents.
Is that a bug for assistant here? Or I haven't found it?

Thanks
B.R
Kermit Mei