depend on data-default, and deprecate the monomorphic name defaultConfig

Main.hs

@@ -37,7 +37,7 @@ main :: IO ()
 main = do
     installSignalHandlers -- important to ignore SIGCHLD to avoid zombies
     args <- getArgs
-    let launch = catchIO buildLaunch >> xmonad defaultConfig
+    let launch = catchIO buildLaunch >> xmonad def
     case args of
         []                    -> launch
         ("--resume":_)        -> launch

XMonad/Config.hs

@@ -1,4 +1,5 @@
-{-# OPTIONS -fno-warn-missing-signatures #-}
+{-# OPTIONS -fno-warn-missing-signatures -fno-warn-orphans #-}
+{-# LANGUAGE TypeFamilies #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Config
@@ -13,13 +14,13 @@
 --
 -- DO NOT MODIFY THIS FILE!  It won't work.  You may configure xmonad
 -- by providing your own @~\/.xmonad\/xmonad.hs@ that overrides
--- specific fields in 'defaultConfig'.  For a starting point, you can
+-- specific fields in the default config, 'def'.  For a starting point, you can
 -- copy the @xmonad.hs@ found in the @man@ directory, or look at
 -- examples on the xmonad wiki.
 --
 ------------------------------------------------------------------------
 
-module XMonad.Config (defaultConfig) where
+module XMonad.Config (defaultConfig, Default(..)) where
 
 --
 -- Useful imports
@@ -38,6 +39,7 @@ import XMonad.Operations
 import XMonad.ManageHook
 import qualified XMonad.StackSet as W
 import Data.Bits ((.|.))
+import Data.Default
 import Data.Monoid
 import qualified Data.Map as M
 import System.Exit
@@ -250,8 +252,8 @@ mouseBindings (XConfig {XMonad.modMask = modMask}) = M.fromList
     -- you may also bind events to the mouse scroll wheel (button4 and button5)
     ]
 
--- | The default set of configuration values itself
-defaultConfig = XConfig
+instance (a ~ Choose Tall (Choose (Mirror Tall) Full)) => Default (XConfig a) where
+  def = XConfig
     { XMonad.borderWidth        = borderWidth
     , XMonad.workspaces         = workspaces
     , XMonad.layoutHook         = layout
@@ -271,6 +273,11 @@ defaultConfig = XConfig
     , XMonad.rootMask           = rootMask
     }
 
+-- | The default set of configuration values itself
+{-# DEPRECATED defaultConfig "Use def (from Data.Default, and re-exported by XMonad and XMonad.Config) instead." #-}
+defaultConfig :: XConfig (Choose Tall (Choose (Mirror Tall) Full))
+defaultConfig = def
+
 -- | Finally, a copy of the default bindings in simple textual tabular format.
 help :: String
 help = unlines ["The default modifier key is 'alt'. Default keybindings:",

XMonad/Core.hs

@@ -37,6 +37,7 @@ import Control.Exception.Extensible (catch, fromException, try, bracket, throw,
 import Control.Applicative
 import Control.Monad.State
 import Control.Monad.Reader
+import Data.Default
 import System.FilePath
 import System.IO
 import System.Info
@@ -149,6 +150,9 @@ instance (Monoid a) => Monoid (X a) where
     mempty  = return mempty
     mappend = liftM2 mappend
 
+instance Default a => Default (X a) where
+    def = return def
+
 type ManageHook = Query (Endo WindowSet)
 newtype Query a = Query (ReaderT Window X a)
     deriving (Functor, Monad, MonadReader Window, MonadIO)
@@ -160,6 +164,9 @@ instance Monoid a => Monoid (Query a) where
     mempty  = return mempty
     mappend = liftM2 mappend
 
+instance Default a => Default (Query a) where
+    def = return def
+
 -- | Run the 'X' monad, given a chunk of 'X' monad code, and an initial state
 -- Return the result, and final state
 runX :: XConf -> XState -> X a -> IO (a, XState)

XMonad/Main.hsc

@@ -85,11 +85,11 @@ xmonad initxmc = do
 
     xinesc <- getCleanedScreenInfo dpy
     nbc    <- do v            <- initColor dpy $ normalBorderColor  xmc
-                 ~(Just nbc_) <- initColor dpy $ normalBorderColor Default.defaultConfig
+                 ~(Just nbc_) <- initColor dpy $ normalBorderColor Default.def
                  return (fromMaybe nbc_ v)
 
     fbc    <- do v <- initColor dpy $ focusedBorderColor xmc
-                 ~(Just fbc_)  <- initColor dpy $ focusedBorderColor Default.defaultConfig
+                 ~(Just fbc_)  <- initColor dpy $ focusedBorderColor Default.def
                  return (fromMaybe fbc_ v)
 
     hSetBuffering stdout NoBuffering

man/xmonad.hs

@@ -258,7 +258,7 @@ main = xmonad defaults
 --
 -- No need to modify this.
 --
-defaults = defaultConfig {
+defaults = def {
       -- simple stuff
         terminal           = myTerminal,
         focusFollowsMouse  = myFocusFollowsMouse,

xmonad.cabal

@@ -58,7 +58,8 @@ library
     else
         build-depends: base < 3
     build-depends: X11>=1.5 && < 1.7, mtl, unix,
-                   utf8-string >= 0.3 && < 0.4
+                   utf8-string >= 0.3 && < 0.4,
+                   data-default
 
     if true
         ghc-options:        -funbox-strict-fields -Wall