1) Make the delegate work always on the model's index, do not go back to the...

1) Make the delegate work always on the model's index, do not go back to the source index, if the model is a proxy (that idea fails anyway with a proxy chain)
2) If the option.rect is empty, don't create or update widgets
3) If the option.rect is not in the view's rectangle, do not create the widgets. This makes sure that only visible widgets are created.