Gtk.TreeIterCompareFunc

A GtkTreeIterCompareFunc should return a negative integer, zero, or a positive integer if a sorts before b, a sorts with b, or a sorts after b respectively. If two iters compare as equal, their order in the sorted model is undefined. In order to ensure that the Gtk.TreeSortable behaves as expected, the GtkTreeIterCompareFunc must define a partial order on the model, i.e. it must be reflexive, antisymmetric and transitive.

For example, if model is a product catalogue, then a compare function for the "price" column could be one which returns <literal>price_of(a) - price_of(b)</literal>.