the data to insert
the GCompareDataFunc used to compare items in the sequence. It is called with two items of the seq and user_data. It should return 0 if the items are equal, a negative value if the first item comes before the second, and a positive value if the second item comes before the first.
user data passed to cmp_func.
a GSequenceIter pointing to the new item.
Inserts data into sequence using func to determine the new position. The sequence must already be sorted according to cmp_func; otherwise the new position of data is undefined. Since 2.14