scaling all contents of a QTableView

Hello... does anybody have a hint about how to scale all the contents of a QTableView? (Cells and headers)...

In I tried the following, but this works only on the cells... headers are not scaled and also, viewport is not working properly...

Code:

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void MyDelegate::paint (QPainter * painter, const QStyleOptionViewItem & option, const QModelIndex & index ) const
{
   QTransform trans;
   trans.scale(1.25, 1.25);
   painter->setTransform(trans);
 
   QStyledItemDelegate::paint(painter, option, index);
}

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Any example or hint would be really appreciated.