Modified TwoPane layout. Not changing second window on mouse focus change.

gistfile1.hs

-- Derived from xmonad-contrib/XMonad/Layout/TwoPane.hs
data TwoPaneMod a = TwoPaneMod Rational Rational deriving (Show, Read)

instance LayoutClass TwoPaneMod Window where
    doLayout (TwoPaneMod _ split) r s = (,Nothing) <$> arrange r s
      where
        arrange rect st = do
            ws <- mapped <$> get
            let x = case reverse (W.up st) of
                    (master:_) -> [(master, left), (W.focus st, right)]
                    []         -> case win2nd ws (W.down st) of
                        (next:_) -> [(W.focus st, left), (next, right)]
                        []       -> [(W.focus st, rect)]
            return x
          where
            (left, right) = splitHorizontallyBy split rect
            win2nd ws ds  = filter (`S.member` ws) ds ++ ds

    handleMessage (TwoPaneMod delta split) x =
        return $ case fromMessage x of
            Just Shrink -> Just (TwoPaneMod delta (split - delta))
            Just Expand -> Just (TwoPaneMod delta (split + delta))
            _           -> Nothing

    description _ = "TwoPaneMod"