[Qt-interest] how to hide the +/- completely in a expanded QTreeView

[TP]

Hi everybody,

With "setItemsExpandable( False )", I have made the items of my QTreeView
not expandable by the user, so the user cannot expand and collapse items
interactively. It means that I propose all the items of the tree by default
with "expandAll()"
But I would like to remove all minus signs "-" in the small box at the left
of the tree, not only at the root level (which can be done
with "setRootIsDecorated( False )"), but at all levels of the tree. It seems 
logical because the items are not expandable.

How to do this?

Thanks

Julien