;+
;
; @file_comments
; Find, from an Id of widget, the Id of the widget which is
; "the top-level base" (i.e., it has no parent)
;
; categories
; widget
;
; @param WIDGET_ID
; This argument should be the widget ID of the
; widget for which information is desired.
;
; @returns
; The Id of the widget which is "the top-level base"
;
; @history
; Sebastien Masson (smasson\@lodyc.jussieu.fr)
;                      22/9/1999
;
; @version
; $Id$
;
;-
FUNCTION findtopid, widget_id
;
  compile_opt idl2, strictarrsubs
;
   id = long(WIDGET_ID)
;    exist = widget_info(id, /managed)
;    if exist EQ 0 then return,  -1
   topid = id
   topid2 = id
   while topid2 NE 0 do begin
      topid = topid2
      topid2 = widget_info(topid2, /parent)
   endwhile
   return,  long(topid)
end