thing.ml

let read_dsr_nonblock n =
  let bytes = Bytes.create n in
  let stdin_fd = Unix.descr_of_in_channel stdin in
  let ready, _, _ = Unix.select [ stdin_fd ] [] [] 0.0001 in
  if Stdlib.(ready = []) then None
  else
    match Unix.read stdin_fd bytes 0 n with
    | exception _ -> None
    | _ ->
        Some
          (Bytes.to_string
          @@ Bytes.sub bytes ~pos:2 ~len:(Bytes.length bytes - 2))

let get_max_yx () : (int * int) option =
  let parse_yx (s : string) =
    String.rsplit2_exn ~on:';' s |> fun (y, x) ->
    ( Int.of_string y,
      Int.of_string
        (String.to_list x |> List.take_while ~f:Char.is_digit |> String.of_list)
    )
  in
  Terminal.move_cursor 0 0;
  Terminal.move_cursor 999 999;
  printf "%s%s%!" Escape_seq.csi "6n";
  Out_channel.flush stdout;
  match read_dsr_nonblock 10 with None -> None | Some s -> Some (parse_yx s)
  
  (* In raw mode and only on certain terminals: get_max_yx () => Some (24, 80) *)