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|
-----------------------------------------------------------------------------
-- |
-- Module : WMonad.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 W monad, a state monad transformer over IO, for the window
-- manager state, and support routines.
--
module WMonad (
W, WorkSpace, WState(..),
runW, 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)
-- | WState, the window manager state.
-- Just the display, width, height and a window list
data WState = WState
{ display :: Display
, screenWidth :: {-# UNPACK #-} !Int
, screenHeight :: {-# UNPACK #-} !Int
, workspace :: {-# UNPACK #-} !WorkSpace -- ^ workspace list
}
type WorkSpace = StackSet Window
-- | The W monad, a StateT transformer over IO encapuslating the window
-- manager state
newtype W a = W (StateT WState IO a)
deriving (Functor, Monad, MonadIO, MonadState WState)
-- | Run the W monad, given a chunk of W monad code, and an initial state
-- Return the result, and final state
runW :: WState -> W a -> IO (a, WState)
runW st (W a) = runStateT a st
-- | Run a monad action with the current display settings
withDisplay :: (Display -> W ()) -> W ()
withDisplay f = gets display >>= f
------------------------------------------------------------------------
-- | Lift an IO action into the W monad
io :: IO a -> W a
io = liftIO
-- | spawn. Launch an external application
spawn :: String -> W ()
spawn x = io (runCommand x) >> return ()
-- | Run a side effecting action with the current workspace. Like 'when' but
whenJust :: Maybe a -> (a -> W ()) -> W ()
whenJust mg f = maybe (return ()) f mg
-- | A 'trace' for the W monad. Logs a string to stderr. The result may
-- be found in your .xsession-errors file
trace :: String -> W ()
trace msg = io $ do hPutStrLn stderr msg; hFlush stderr
|
