Qt set a custom widget inside a QTableView cell

I want-to put-a customed-widget into the cell of QTableView. The Widget can-be a QPushButton, a checkBox or something else. I've tried following methods, but no-one satisfies me:

1. Use delegate. This strategy can paint widget, but cant-be a customed widget, and cant interact.
2. Use QTableView::setIndexWidget(). Using this strategy, the customed-widget covers the cell wholly & absolutely, delegate binded to QTableView not working, which means a-double-click() wont make Edit operation on-the cell.

Note that the function is stand-alone, like a plugin. So I cant do following things.

1. Inherit from QTableView. I can only get a-pointer-variable binded with QTableView----only an object of QTableView.
2. Inherit from any-model. The model is control by other user, the programmer writing model shouldn't and can't just use my-customed model.

The problem is really complex and too-many constraints restrict the design.

Thanks for all of you contributing to this question, I've found a way to solve this problem. It is solved as the "original thought", which is just to draw a QToolButton on the tableView, using the QModelIndex. Through QModelIndex, I can get the geomertry location where I can draw any QWidget. However, this method is really complex, for I have to maintain the changes of QModelIndex, like removeColumns and insertColumns.

Another problem is concerned that I have to distinguish between hide & delete columns or rows. And I think I should post an another new question for help. Thanks again.