How to sort glazed TreeList?

I have a pretty weird question - how to sort glazed TreeList? I am using it in SWT NatTable, and when my data provider is set to GlazedListsDataProvider with TreeList inside it, sorting works in a very strange way. It works fine, if I am using GlazedListsDataProvider with SortedList.

For instance, my tree looks like that:

Root
  Node1
   Child1
   Child2
  Node2
   Child3

I need to sort only children INSIDE Node1 and Node2, separately one of another (so that only child1 and child2 will change their place). However, After sorting it looks like following:

Root
  Node1
  Node2
   Child1
   Child2
   Child3

Reversed sorting:

Root
  Node1
  Node2
   Child2
   Child1
   Child3

So basically, it kind of working (it does sort children in a correct way), but moreover it sorts elements, which it should not sort. What could be a reason of such behavior? My sorting algorithm is simple:

compare (element1, element2) {
   if (both elements are under same parent and have same type)
     compare
   otherwise
     return 0
   }

I am doing sorting as proposed in following example http://kari.dy.fi/src/sample/foldertree.zip - meaning, that after comparator is build in SortState I am setting it into the TreeFormat, used by TreeList.

I assume, that returning 0 does not work in a correct way, however, I can not see other solution. Or may be it is a problem somewhere else, not in my comparator.

Thank you for your patience, I will be glad to get any hints. Best regards, Alex G.

Solution

So, here is my solution for this problem: DZone Article. Once again, it is only one of the possible solutions, and it is not perfect, but it is working:)