compare

Compares two given items according to the sort order implemented by the sorter.

Sorters implement a partial order:

* It is reflexive, ie a = a * It is antisymmetric, ie if a < b and b < a, then a = b * It is transitive, ie given any 3 items with a ≤ b and b ≤ c, then a ≤ c

The sorter may signal it conforms to additional constraints via the return value of [[email protected]_order].

Parameters:

this	a `GtkSorter`
item1	first item to compare
item2	second item to compare

Returns:

gtk_ordering_equal if item1 == item2, gtk_ordering_smaller if item1 < item2, gtk_ordering_larger if item1 > item2