# File lib/sup/buffer.rb, line 435
  def kill_buffer buf
    raise ArgumentError, "buffer not on stack: #{buf}: #{buf.title.inspect}" unless @buffers.member? buf

    buf.mode.cleanup
    @buffers.delete buf
    @name_map.delete buf.title
    @focus_buf = nil if @focus_buf == buf
    if @buffers.empty?
      ## TODO: something intelligent here
      ## for now I will simply prohibit killing the inbox buffer.
    else
      raise_to_front @buffers.last
    end
  end