
    header bar = style
      [ ("position", "absolute")
      , ("left", px 0)
      , ("top", px 0)
      , ("width", "100%")
      , ("height", px (if bar then 24 else 0))
      , ("background-color", "#333")
      , ("border-radius", "2px 2px 0px 0px")
      , ("user-select", "none")
      ]
    content bar = style
      [ ("position", "absolute")