class Infobar

def busy(frames: :circle1, **opts, &block)
  block_given? or raise ArgumentError, 'block is required as an argument'
  duration = opts.delete(:sleep) || 0.1
  reset
  call(**opts | {
    total: Float::INFINITY,
    message: { format: ' %l %te %s ', '%s' => { frames: frames } },
  })
  ib = Thread.new {
    loop do
      +infobar
      sleep duration
    end
  }
  r = nil
  t = Thread.new { r = yield }
  t.join
  ib.kill
  r
end