Extract NamedWindow support from Mosaic into its own module

NamedWindows.hs

@@ -0,0 +1,31 @@
+module XMonadContrib.NamedWindows ( NamedWindow, getName, withNamedWindow, unName ) where
+
+-- This module allows you to associate the X titles of windows with
+-- them.  See XMonadContrib.Mosaic for an example of its use.
+
+import Control.Monad.Reader ( asks )
+import Control.Monad.State ( gets )
+
+import qualified StackSet as W ( peek )
+
+import Graphics.X11.Xlib
+import Graphics.X11.Xlib.Extras ( fetchName )
+
+import XMonad
+
+data NamedWindow = NW !String !Window
+instance Eq NamedWindow where
+    (NW s _) == (NW s' _) = s == s'
+instance Ord NamedWindow where
+    compare (NW s _) (NW s' _) = compare s s'
+
+getName :: Window -> X NamedWindow
+getName w = asks display >>= \d -> do n <- maybe "" id `fmap` io (fetchName d w)
+                                      return $ NW n w
+
+unName :: NamedWindow -> Window
+unName (NW _ w) = w
+
+withNamedWindow :: (NamedWindow -> X ()) -> X ()
+withNamedWindow f = do ws <- gets windowset
+                       whenJust (W.peek ws) $ \w -> getName w >>= f