prop_findIndex (x :: T) =
    and [ tag w == fromJust (findTag i x)
        | w <- workspace (current x) : map workspace (visible x)  ++ hidden x
        , t <- maybeToList (stack w)
        , i <- focus t : up t ++ down t
        ]
prop_findIndex (x :: T) =
    and [ tag w == fromJust (findTag i x)
        | w <- workspace (current x) : map workspace (visible x)  ++ hidden x
        , t <- maybeToList (stack w)
        , i <- focus t : up t ++ down t
        ]
prop_findIndex (x :: T) =
    and [ tag w == fromJust (findTag i x)
        | w <- workspace (current x) : map workspace (visible x)  ++ hidden x
        , t <- maybeToList (stack w)
        , i <- focus t : up t ++ down t
        ]