let button_handlers_in_pos (wr: win_ref) (pos: int) (b: b)
: (node_ref * rslt list) option =
assert (win_valid wr b);
begin match
(page_assoc_valid (win_assoc_valid wr b).win_page b).page_document
with
| None -> None
| Some(root) ->
begin try
Some(List.nth (button_handlers_in_tree root b) pos)
with
| Failure("nth") -> None
end
end