gtk-tree-sortable-set-default-sort-func (sortable func)

sortable -- a gtk-tree-sortable object
func -- a gtk-tree-iter-compare-func callback function

Sets the default comparison callback function used when sorting to be func. If the current sort column ID of sortable is +gtk-tree-sortable-default-sort-column-id+, then the model will sort using this function.

If func is nil, then there will be no default comparison function. This means that once the model has been sorted, it cannot go back to the default state. In this case, when the current sort column ID of sortable is +gtk-tree-sortable-default-sort-column-id, the model will be unsorted.