public delegate bool TreeSelectionFunc (TreeSelection selection, TreeModel model, TreePath path, bool path_currently_selected)
A function used by set_select_function to filter whether or not a row may be selected.
It is called whenever a row's state might change. A return value of true indicates to
that it is okay to change the selection.
A TreeModel being viewed
The TreePath of the row in question
true, if the path is currently selected
true, if the selection state of the row can be toggled