Comment by [email protected]: @guillembarba
The first use case that triggered this blueprint is the management of products and product categories. The idea is to show side by side the list of categories and the list of product and let the user drop products on categories. UI-wise it means dropping one line on another (which currently is used to create child records).
But you are right that we will open more features if we allow to dnd the record under a list (but not on a line). This means that the client must also send some extra information. But this also means that the on_drop signature is not correct (because in this case there is no record to instantiate and so on_drop must be a classmethod).
For more information: https://code.google.com/p/tryton/wiki/Drag_and_drop_between_two_lists
