I had misconfigured ensureVisible's margins , and the view's size and the scene's rect .
Now it works fine :)

For item to be editable you would implement flags() in your model and make sure the returned flag set contains Qt::ItemIsEditable. You'd also need to implement the setData() method and handle Qt::EditRole in the data() method.

For the columns from the database just return the base implementation of these methods and provide override only for your extra column.