Assume locale is utf8 for spawn.

This adds the utf8-string dependency so that users no longer need to encode
strings they (possibly indirectly) pass to spawn. This is the expected
behavior, since each Char in String should be an actual character.

For systems that do not use utf8 this does not help. Fixing this by using iconv
or similar libraries may be done later.

XMonad/Core.hs

@@ -32,6 +32,7 @@ module XMonad.Core (
 import XMonad.StackSet hiding (modify)
 
 import Prelude hiding ( catch )
+import Codec.Binary.UTF8.String (encodeString)
 import Control.Exception.Extensible (catch, fromException, try, bracket, throw, finally, SomeException(..))
 import Control.Applicative
 import Control.Monad.State
@@ -384,12 +385,14 @@ catchIO f = io (f `catch` \(SomeException e) -> hPrint stderr e >> hFlush stderr
 
 -- | spawn. Launch an external application. Specifically, it double-forks and
 -- runs the 'String' you pass as a command to \/bin\/sh.
+--
+-- Note this function assumes your locale uses utf8.
 spawn :: MonadIO m => String -> m ()
 spawn x = spawnPID x >> return ()
 
 -- | Like 'spawn', but returns the 'ProcessID' of the launched application
 spawnPID :: MonadIO m => String -> m ProcessID
-spawnPID x = xfork $ executeFile "/bin/sh" False ["-c", x] Nothing
+spawnPID x = xfork $ executeFile "/bin/sh" False ["-c", encodeString x] Nothing
 
 -- | A replacement for 'forkProcess' which resets default signal handlers.
 xfork :: MonadIO m => IO () -> m ProcessID

xmonad.cabal

@@ -46,7 +46,8 @@ library
         build-depends: base < 5 && >=3, containers, directory, process, filepath, extensible-exceptions
     else
         build-depends: base < 3
-    build-depends: X11>=1.5.0.0 && < 1.6, mtl, unix
+    build-depends: X11>=1.5.0.0 && < 1.6, mtl, unix,
+                   utf8-string >= 0.3 && < 0.4
 
     if true
         ghc-options:        -funbox-strict-fields -Wall