Wysota, Why I need layouts ?
This is the reason because a Widget extending Qtreeview is not viewed using promote ?
And :
1.- I have tested the class in 'old' style (creating the instance, givin size, etc) and It is showed. ( an empty white QTreeView)
2.- If I extend the A_table to Qpushbutton.... promote works fine, I see an empty space at my form, but I see a button when run. (so, it is ok).
So, finally, I cannot extend a basic QTreeView using promote ?