Add --restart, a command line flag to cause a running xmonad process to restart

Main.hs

@@ -40,6 +40,7 @@ main = do
         ["--resume", _]       -> launch
         ["--help"]            -> usage
         ["--recompile"]       -> recompile True >> return ()
+        ["--restart"]         -> sendRestart >> return ()
         ["--version"]         -> putStrLn ("xmonad " ++ showVersion version)
 #ifdef TESTING
         ("--run-tests":_)     -> Properties.main
@@ -55,6 +56,7 @@ usage = do
         "  --help                       Print this message" :
         "  --version                    Print the version number" :
         "  --recompile                  Recompile your ~/.xmonad/xmonad.hs" :
+        "  --restart                    Request a running xmonad process to restart" :
 #ifdef TESTING
         "  --run-tests                  Run the test suite" :
 #endif
@@ -83,3 +85,14 @@ buildLaunch = do
     args <- getArgs
     executeFile (dir ++ "/xmonad-"++arch++"-"++os) False args Nothing
     return ()
+
+sendRestart :: IO ()
+sendRestart = do
+    dpy <- openDisplay ""
+    rw <- rootWindow dpy $ defaultScreen dpy
+    xmonad_restart <- internAtom dpy "XMONAD_RESTART" False
+    allocaXEvent $ \e -> do
+        setEventType e clientMessage
+        setClientMessageEvent e rw xmonad_restart 32 0 currentTime
+        sendEvent dpy rw False structureNotifyMask e
+    sync dpy False

XMonad/Main.hsc

@@ -280,6 +280,12 @@ handle (ConfigureEvent {ev_window = w}) = whenX (isRoot w) rescreen
 handle PropertyEvent { ev_event_type = t, ev_atom = a }
     | t == propertyNotify && a == wM_NAME = userCodeDef () =<< asks (logHook . config)
 
+handle e@ClientMessageEvent { ev_message_type = mt } = do
+    a <- getAtom "XMONAD_RESTART"
+    if (mt == a)
+        then restart "xmonad" True
+        else broadcastMessage e
+
 handle e = broadcastMessage e -- trace (eventName e) -- ignoring
 
 

man/xmonad.1.in

@@ -23,6 +23,8 @@ When running with multiple monitors (Xinerama), each screen has exactly 1 worksp
 .TP
 \fB--recompile
 Recompiles your configuration in ~/.xmonad/xmonad.hs
+\fB--restart
+Causes the currently running xmonad process to restart
 .TP
 \fB--version
 Display version of \fBxmonad\fR.