    # File lib/rubygame/events/joystick_events.rb, line 105
          def initialize( joystick_id, button )

            unless joystick_id.kind_of?(Fixnum) and joystick_id >= 0
              raise ArgumentError, "joystick_id must be an integer >= 0"
            end

            @joystick_id = joystick_id

            unless button.kind_of?(Fixnum) and button >= 0
              raise ArgumentError, "button must be an integer >= 0"
            end

            @button = button

          end