def input_string prompt="Insert: ", maxlen=80
      #ret, str = rb_getstr(@form.window, $error_message_row, $error_message_col,  prompt, maxlen, config)
      ret, str = rb_getstr(@form.window, $error_message_row, $error_message_col,  prompt, maxlen, config)
      #return str if ret == 0
      #return ""
    end
def input_string prompt="Insert: ", maxlen=80
      #ret, str = rb_getstr(@form.window, $error_message_row, $error_message_col,  prompt, maxlen, config)
      ret, str = rb_getstr(@form.window, $error_message_row, $error_message_col,  prompt, maxlen, config)
      #return str if ret == 0
      #return ""
    end
common method to input a blank string
 @param [String] prompt to display before string
 @param [int] max length of input
 @return [0, -1] return value 0 if okay, -1 if error