How to update eventFilter function?

I use update( ) function but it`s not worked .

bool CLASS_NAME::eventFilter(QObject *o, QEvent *e)
{
for ( int i = 0; i < 42; i++ ) {

if (o == tree_widget[i]->viewport() && e->type() == QEvent::Paint) {

QPainter p;

p.begin(tree_widget[i]->viewport() );

p.drawText( 35, 70, "something");

p.end();
}
}

return QWidget::eventFilter(o, e);
}