Factor out pprWindowSet (and Xinerama version) from dynamicLog.

This patch lets you pretty-print a WindowSet to a string, rather than always
printing it out to stdout directly.

DynamicLog.hs

@@ -21,7 +21,7 @@
 module XMonadContrib.DynamicLog (
                                  -- * Usage
                                  -- $usage 
-                                 dynamicLog, dynamicLogXinerama
+                                 dynamicLog, dynamicLogXinerama, pprWindowSet, pprWindowSetXinerama
                                 ) where
 
 -- 
@@ -52,9 +52,10 @@ import qualified StackSet as S
 --  
 
 dynamicLog :: X ()
-dynamicLog = withWindowSet $ io . putStrLn . ppr
-  where
-    ppr s =  concatMap fmt $ sortBy (compare `on` S.tag)
+dynamicLog = withWindowSet $ io . putStrLn . pprWindowSet
+
+pprWindowSet :: WindowSet -> String
+pprWindowSet s =  concatMap fmt $ sortBy (compare `on` S.tag)
             (map S.workspace (S.current s : S.visible s) ++ S.hidden s)
    where this     = S.tag (S.workspace (S.current s))
          visibles = map (S.tag . S.workspace) (S.visible s)
@@ -73,9 +74,10 @@ dynamicLog = withWindowSet $ io . putStrLn . ppr
 -- and 2 and 7 are non-visible, non-empty workspaces
 --
 dynamicLogXinerama :: X ()
-dynamicLogXinerama = withWindowSet $ io . putStrLn . ppr
-  where
-    ppr ws = "[" ++ unwords onscreen ++ "] " ++ unwords offscreen
+dynamicLogXinerama = withWindowSet $ io . putStrLn . pprWindowSetXinerama
+
+pprWindowSetXinerama :: WindowSet -> String
+pprWindowSetXinerama ws = "[" ++ unwords onscreen ++ "] " ++ unwords offscreen
   where onscreen  = map (pprTag . S.workspace)
                         . sortBy (compare `on` S.screen) $ S.current ws : S.visible ws
         offscreen = map pprTag . filter (isJust . S.stack)