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diff --git a/src/lib/Xmobar/Plugins/Locks.hs b/src/lib/Xmobar/Plugins/Locks.hs
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+++ b/src/lib/Xmobar/Plugins/Locks.hs
@@ -0,0 +1,64 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  Plugins.Locks
+-- Copyright   :  (c) Patrick Chilton
+-- License     :  BSD-style (see LICENSE)
+--
+-- Maintainer  :  Patrick Chilton <chpatrick@gmail.com>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- A plugin that displays the status of the lock keys.
+--
+-----------------------------------------------------------------------------
+
+module Xmobar.Plugins.Locks where
+
+import Graphics.X11
+import Data.List
+import Data.Bits
+import Control.Monad
+import Graphics.X11.Xlib.Extras
+import Xmobar.Plugins
+import Xmobar.Plugins.Kbd
+import Xmobar.XUtil (nextEvent')
+
+data Locks = Locks
+    deriving (Read, Show)
+
+locks :: [ ( KeySym, String )]
+locks = [ ( xK_Caps_Lock,   "CAPS"   )
+        , ( xK_Num_Lock,    "NUM"    )
+        , ( xK_Scroll_Lock, "SCROLL" )
+        ]
+
+run' :: Display -> Window -> IO String
+run' d root = do
+    modMap <- getModifierMapping d
+    ( _, _, _, _, _, _, _, m ) <- queryPointer d root
+
+    ls <- filterM ( \( ks, _ ) -> do
+        kc <- keysymToKeycode d ks
+        return $ case find (elem kc . snd) modMap of
+            Nothing       -> False
+            Just ( i, _ ) -> testBit m (fromIntegral i)
+        ) locks
+
+    return $ unwords $ map snd ls
+
+instance Exec Locks where
+    alias Locks = "locks"
+    start Locks cb = do
+        d <- openDisplay ""
+        root <- rootWindow d (defaultScreen d)
+        _ <- xkbSelectEventDetails d xkbUseCoreKbd xkbIndicatorStateNotify m m
+
+        allocaXEvent $ \ep -> forever $ do
+            cb =<< run' d root
+            nextEvent' d ep
+            getEvent ep
+
+        closeDisplay d
+        return ()
+      where
+        m = xkbAllStateComponentsMask