method add_file_box f_opt =
let title =
match f_opt with
None -> "<no name>"
| Some s -> Filename.basename s
in
let label = GMisc.label ~text: title () in
let fb = new file label f_opt in
let eb = GBin.event_box () in
fb#reparent eb#coerce;
ignore(notebook#append_page ~tab_label: label#coerce eb#coerce);
file_boxes <- file_boxes @ [fb];
notebook#goto_page ((List.length file_boxes) - 1)