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+{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
+
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.Layout.ThreeColumns
+-- Copyright   :  (c) Kai Grossjohann <kai@emptydomain.de>
+-- License     :  BSD3-style (see LICENSE)
+-- 
+-- Maintainer  :  ?
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- A layout similar to tall but with three columns.
+--
+-----------------------------------------------------------------------------
+
+module XMonad.Layout.ThreeColumns (
+                              -- * Usage
+                              -- $usage
+                              ThreeCol(..)
+                             ) where
+
+import XMonad
+import qualified XMonad.StackSet as W
+import XMonad.Layouts ( Resize(..), IncMasterN(..), splitVertically, splitHorizontallyBy )
+
+import Data.Ratio
+
+--import Control.Monad.State
+import Control.Monad.Reader
+
+import Graphics.X11.Xlib
+
+-- $usage
+--
+-- You can use this module with the following in your Config.hs file:
+--
+-- > import XMonad.Layout.ThreeColumns
+--
+--  and add, to the list of layouts:
+--
+-- > ThreeCol nmaster delta ratio
+
+-- %import XMonad.Layout.ThreeColumns
+-- %layout , ThreeCol nmaster delta ratio
+
+data ThreeCol a = ThreeCol Int Rational Rational deriving (Show,Read)
+
+instance LayoutClass ThreeCol a where
+    doLayout (ThreeCol nmaster _ frac) r =
+        return . (\x->(x,Nothing)) .
+        ap zip (tile3 frac r nmaster . length) . W.integrate
+    handleMessage (ThreeCol nmaster delta frac) m =
+        return $ msum [fmap resize     (fromMessage m)
+                      ,fmap incmastern (fromMessage m)]
+            where resize Shrink = ThreeCol nmaster delta (max 0 $ frac-delta)
+                  resize Expand = ThreeCol nmaster delta (min 1 $ frac+delta)
+                  incmastern (IncMasterN d) = ThreeCol (max 0 (nmaster+d)) delta frac
+    description _ = "ThreeCol"
+
+-- | tile3.  Compute window positions using 3 panes
+tile3 :: Rational -> Rectangle -> Int -> Int -> [Rectangle]
+tile3 f r nmaster n 
+    | n <= nmaster || nmaster == 0 = splitVertically n r
+    | n <= nmaster+1 = splitVertically nmaster s1 ++ splitVertically (n-nmaster) s2
+    | otherwise = splitVertically nmaster r1 ++ splitVertically nmid r2 ++ splitVertically nright r3
+  where (r1, r2, r3) = split3HorizontallyBy f r
+        (s1, s2) = splitHorizontallyBy f r
+        nslave = (n - nmaster)
+        nmid = ceiling (nslave % 2)
+        nright = (n - nmaster - nmid)
+
+split3HorizontallyBy :: Rational -> Rectangle -> (Rectangle, Rectangle, Rectangle)
+split3HorizontallyBy f (Rectangle sx sy sw sh) =
+    ( Rectangle sx sy leftw sh
+    , Rectangle (sx + fromIntegral leftw) sy midw sh
+    , Rectangle (sx + fromIntegral leftw + fromIntegral midw) sy rightw sh )
+  where leftw = ceiling $ fromIntegral sw * (2/3) * f
+        midw = ceiling ( (sw - leftw) % 2 )
+        rightw = sw - leftw - midw