notes.txt

Tree model architecture:


`ObsList` = "pure" list list_model
  Python list,
  plus: Children source / retrieval,
  plus: events:
      on_insert,
      on_replace,
      on_remove,
      on_load_children,
      on_sort,
      on_get_selection,
  plus: notion of associated "toolkit id"
      
`ListBinding` = databinding (non-toolkit specific):
    mapping list columns to object propertes/functions and vice-versa
    sort-key / sort-ascending
    bind events to hook methods (to be subclassed)

`ListBindingQt`, `ListBindingTk`: actual implementation of event reactions; also
doubles as QAbstractitemModel / kind-of Tkinter traceable variable. ie.
adapter-like classes


Open problems / issues:

 - Assigning ObsList from Listview A to Listview B binds both listviews to the list.
    Test that this works (views synchronized; last assignment controls get_selection)

 - ObsList.children_source: This is now a property of the ObsList (ie. model.)
   When assigning a non-obslist to a view, children_source is taken over from
   previous val --> impure!
   when assigning an ObsList, its children_source is used --> hint in manual