fromWindowOp Window ManageHook fromWindowOp fn ask liftX fn doF id fro

fromWindowOp :: (Window -> X()) -> ManageHook
fromWindowOp fn = ask >>= \w -> liftX (fn w) >> doF id

fromX :: X () -> ManageHook
fromX op = fromWindowOp $ const op

...
[ className =? "Gimp" --> fromX (sendMessage ...) ]