Hi Steffen, I think it is simpler to check if the screen has height > width, and then do what Mirror does if that happens to be the case. The following code is a slight modification of the code for Mirror probably does that (it compiles but I have not tested it): {-# LANGUAGE MultiParamTypeClasses #-} -- at the top of the file {-# LANGUAGE FlexibleInstances #-} import XMonad import Control.Arrow import qualified XMonad.StackSet as W -- | Mirror a layout, compute its 90 degree rotated form. newtype MirrorAspect l a = MirrorAspect (l a) deriving (Show, Read) instance LayoutClass l a => LayoutClass (MirrorAspect l) a where runLayout (W.Workspace i (MirrorAspect l) ms) r@(Rectangle _ _ w h) = (map (second mirrorRect) *** fmap MirrorAspect) `fmap` runLayout (W.Workspace i l ms) (mirrorRect r) where -- | possibly Mirror a rectangle mirrorRect :: Rectangle -> Rectangle mirrorRect r0@(Rectangle rx ry rw rh) | h > w = Rectangle ry rx rh rw | otherwise = r0 handleMessage (MirrorAspect l) = fmap (fmap MirrorAspect) . handleMessage l description (MirrorAspect l) = "MirrorAspect "++ description l Regards, Adam