anchor.diff:          tree.Selection.UnselectAll()
           tree.Selection.SelectIter iter.Value
   
  -    let getSelectedNodes (pad:TreeViewPad) =
  -        let (nodes:ITreeNavigator[]) = pad.TreeView?GetSelectedNodes()
  -        nodes
  +    let getSelectedNode (pad:TreeViewPad) =
  +        let (node:ITreeNavigator) = pad.TreeView?GetSelectedNode()
  +        node
   
       let getPath (tree:TreeView) =
           tree.Selection.GetSelectedRows().[0]
  
positive.code:             let res, iter = getIter path
              if prev && res then
                  select tree iter
                  let nodes = getSelectedNodes pad
                  if nodes.[0].Expanded then
                      // move to last child
                      let path = getPath tree
                      path.Down()
  
negative.code:             let path = selected.[0]
              let _res, iterOriginal = getIter path
              path.Down()
              let node = getSelectedNode pad
              let res, iter = getIter path
              if res && node.Expanded then
                  select tree iter
              else
                  let path = getPath tree
  