Added javaHack

Fixes Java applications that don't work well with xmonad, by setting @_JAVA_AWT_WM_NONREPARENTING=1@

CHANGES.md

@@ -52,6 +52,8 @@
     Serves as a collection of hacks and fixes that should be easily acessible to users.
     The first element of this module is windowedFullscreenFix, which fixes fullscreen behaviour
     of chromium based applications when using windowed fullscreen.
+    A second entry is `javaHack`, which helps when dealing with Java applications that might
+    not work well with xmonad.
 
   * `XMonad.Util.ActionCycle`
 

XMonad/Util/Hacks.hs

@@ -23,12 +23,16 @@ module XMonad.Util.Hacks
   ( -- * Windowed fullscreen
     -- $windowedFullscreenFix
     windowedFullscreenFixEventHook
+    -- * Java Hack
+    -- $java
+  , javaHack
   ) where
 
 
 import XMonad
 import Data.Monoid (All(All))
 import Control.Monad (when)
+import System.Posix.Env (putEnv)
 
 
 -- $windowedFullscreenFix
@@ -65,10 +69,26 @@ windowedFullscreenFixEventHook :: Event -> X All
 windowedFullscreenFixEventHook (ClientMessageEvent _ _ _ dpy win typ (_:dats)) = do
   wmstate <- getAtom "_NET_WM_STATE"
   fullscreen <- getAtom "_NET_WM_STATE_FULLSCREEN"
-  when (typ == wmstate && fromIntegral fullscreen `elem` dats) $ do
+  when (typ == wmstate && fromIntegral fullscreen `elem` dats) $
     withWindowAttributes dpy win $ \attrs ->
       liftIO $ do
         resizeWindow dpy win (fromIntegral $ wa_width attrs - 1) (fromIntegral $ wa_height attrs)
         resizeWindow dpy win (fromIntegral $ wa_width attrs) (fromIntegral $ wa_height attrs)
   return $ All True
 windowedFullscreenFixEventHook _ = return $ All True
+
+
+-- $java
+-- | Some java Applications might not work with xmonad. A common workaround would be to set the environment
+-- variable @_JAVA_AWT_WM_NONREPARENTING@ to 1. The function 'javaHack' does exactly that.
+-- Example usage:
+--
+-- > main = xmonad $ Hacks.javaHack (def {...})
+--
+
+-- | Fixes Java applications that don't work well with xmonad, by setting @_JAVA_AWT_WM_NONREPARENTING=1@
+javaHack :: XConfig l -> XConfig l
+javaHack conf = conf
+  { startupHook = startupHook conf
+                    *> io (putEnv "_JAVA_AWT_WM_NONREPARENTING=1")
+  }