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+-----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.hs
+-- Copyright   :  (c) Spencer Janssen 2007
+-- License     :  BSD3-style (see LICENSE)
+-- 
+-- Maintainer  :  sjanssen@cse.unl.edu
+-- Stability   :  unstable
+-- Portability :  not portable, uses cunning newtype deriving
+--
+-----------------------------------------------------------------------------
+--
+-- The X monad, a state monad transformer over IO, for the window
+-- manager state, and support routines.
+--
+
+module XMonad (
+    X, WorkSpace, XState(..),runX, withDisplay, io, spawn, trace, whenJust
+  ) where
+
+import StackSet (StackSet)
+
+import Control.Monad.State
+import System.IO
+import System.Process (runCommand)
+import Graphics.X11.Xlib (Display,Window)
+
+-- | XState, the window manager state.
+-- Just the display, width, height and a window list
+data XState = XState
+    { display       :: Display
+    , screenWidth   :: {-# UNPACK #-} !Int
+    , screenHeight  :: {-# UNPACK #-} !Int
+    , workspace     :: {-# UNPACK #-} !WorkSpace      -- ^ workspace list
+    }
+
+type WorkSpace = StackSet Window
+
+-- | The X monad, a StateT transformer over IO encapuslating the window
+-- manager state
+newtype X a = X (StateT XState IO a)
+    deriving (Functor, Monad, MonadIO, MonadState XState)
+
+-- | Run the X monad, given a chunk of X monad code, and an initial state
+-- Return the result, and final state
+runX :: XState -> X a -> IO ()
+runX st (X a) = runStateT a st >> return ()
+
+-- | Run a monad action with the current display settings
+withDisplay :: (Display -> X ()) -> X ()
+withDisplay f = gets display >>= f
+
+------------------------------------------------------------------------
+
+-- | Lift an IO action into the X monad
+io :: IO a -> X a
+io = liftIO
+{-# INLINE io #-}
+
+-- | spawn. Launch an external application
+spawn :: String -> X ()
+spawn x = io (runCommand x) >> return ()
+
+-- | Run a side effecting action with the current workspace. Like 'when' but
+whenJust :: Maybe a -> (a -> X ()) -> X ()
+whenJust mg f = maybe (return ()) f mg
+
+-- | A 'trace' for the X monad. Logs a string to stderr. The result may
+-- be found in your .xsession-errors file
+trace :: String -> X ()
+trace msg = io $! do hPutStrLn stderr msg; hFlush stderr