def validate_field f=@widgets[@active_index]
      begin
        on_leave f
      rescue => err
        $log.error "form: validate_field caught EXCEPTION #{err}"
        $log.error(err.backtrace.join("\n")) 
#        $error_message = "#{err}" # changed 2010  
        $error_message.value = "#{err}"
        Ncurses.beep
        return -1
      end
      return 0
    end
def validate_field f=@widgets[@active_index]
      begin
        on_leave f
      rescue => err
        $log.error "form: validate_field caught EXCEPTION #{err}"
        $log.error(err.backtrace.join("\n")) 
#        $error_message = "#{err}" # changed 2010  
        $error_message.value = "#{err}"
        Ncurses.beep
        return -1
      end
      return 0
    end
run validate_field on a field, usually whatevers current
 before transferring control
 We should try to automate this so developer does not have to remember to call it.
 # @param field object
 @return [0, -1] for success or failure
 NOTE : catches exception and sets $error_message, check if -1