See http://www.qtcentre.org/archive/index.php/t-19600.html

Looking at the documentation http://doc.qt.nokia.com/4.7/qitemeditorfactory.html, calling QItemEditorFactory::setDefaultFactory will set a new factory that will be applied to all delegates in all views. The only way to set a new default factory is to start with a new one by calling the default constructor:

QItemEditorFactory newFactory = new QItemEditorFactory().

If you then set

QItemEditorFactory::setDefaultFactory(newFactory);

I would expect the default behaviour of delegates to still be present (being able to edit numbers and QStrings etc. in views the usual way), but it actually disables all of that functionality everywhere.

Creating a new QItemEditorFactory() should initialize that default functionality from the get-go.