let fetch_url (u: url) (wr: win_ref) (b: b)
: b * output_event list =
assert (win_valid wr b);
begin match u with
| Blank_url ->
(b, [])
| Http_url(d, uri) ->
let dst = Doc_dst(wr) in
let (b', oe) = http_send d uri "" dst b in
(b', [ oe ])
end