Anyway, I had no answer to this post, so I chose an implementation myshelf.

I used paintEvent of my QGraphicsView to paint over the QGV and it works great.

I have to think now a way to use lineinput inside this QWidget overlay to key input one value.
Maybe QLineInput over the widget or full new implementation of an input in the overlaying widget If I not make it.

Here is the screenshot of what I made:

http://imagebin.org/69110