TreeView : parent of parent of parent of ... of item

[Yves]

Dear All,
with

      'bn'⎕WC'form'('coord' 'pixel')
      'bn.tv'⎕WC'treeview'
      depth←0 1 2 3 3 2 2 3 3 1 2 3 3 2 3 3
      itm←1⊂[1]'abcdefghijklmnopqrstuvwxyz'[?((⍴depth),3)⍴26]
      bn.tv.(Items Depth)←itm depth

by mouse, i select an item.

      ⍸ bn.tv.SelItems
      12

i search vector of all parents from root to selected item.
by hands, i do

      bn.tv.GetParentItem 12
11
      bn.tv.GetParentItem 11
10
      bn.tv.GetParentItem 10
1

but, in case of all unselect

      bn.tv.SelItems
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
      bn.tv.GetParentItem 0
¯1

i feel a dfns is a better solution, but i don't see how to write in dfns.
can you explain to me how to write it ?

Best Regards,
Yves

[Yves]

with

      ]box on
      ]row on

my actual function is

      result←parentOfItem no

      result←no

      :Repeat
         no←bn.tv.GetParentItem no
         result←no,result
      :Until 0=no

      result←sort{(0≠⍵)/⍵}result

and result are

      parentOfItem ¨ ⍳ (⍴ bn.tv.Items)
┌─┬───┬─────┬───────┬───────┬─────┬─────┬───────┬───────┬────┬───────┬──────────┬──────────┬───────┬──────────┬──────────┐
│1│1 2│1 2 3│1 2 3 4│1 2 3 5│1 2 6│1 2 7│1 2 7 8│1 2 7 9│1 10│1 10 11│1 10 11 12│1 10 11 13│1 10 14│1 10 14 15│1 10 14 16│
└─┴───┴─────┴───────┴───────┴─────┴─────┴───────┴───────┴────┴───────┴──────────┴──────────┴───────┴──────────┴──────────┘

weakness, not very elegant...