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diff --git a/XMonad/Layout/DraggingVisualizer.hs b/XMonad/Layout/DraggingVisualizer.hs
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+{-# LANGUAGE DeriveDataTypeable, TypeSynonymInstances, MultiParamTypeClasses, FlexibleContexts #-}
+----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.Layout.DraggingVisualizer
+-- Copyright   :  (c) Jan Vornberger 2009
+-- License     :  BSD3-style (see LICENSE)
+--
+-- Maintainer  :  jan.vornberger@informatik.uni-oldenburg.de
+-- Stability   :  unstable
+-- Portability :  not portable
+--
+-- A helper module to visualize the process of dragging a window by
+-- making it follow the mouse cursor. See "XMonad.Layout.WindowSwitcherDecoration"
+-- for a module that makes use of this.
+--
+-----------------------------------------------------------------------------
+
+module XMonad.Layout.DraggingVisualizer
+    ( draggingVisualizer,
+      DraggingVisualizerMsg (..)
+    ) where
+
+import XMonad
+import XMonad.Layout.LayoutModifier
+
+data DraggingVisualizer a = DraggingVisualizer (Maybe (Window, Rectangle)) deriving ( Read, Show )
+draggingVisualizer :: LayoutClass l Window => l Window -> ModifiedLayout DraggingVisualizer l Window
+draggingVisualizer = ModifiedLayout $ DraggingVisualizer Nothing
+
+data DraggingVisualizerMsg = DraggingWindow Window Rectangle
+                                | DraggingStopped
+                                deriving ( Typeable, Eq )
+instance Message DraggingVisualizerMsg
+
+instance LayoutModifier DraggingVisualizer Window where
+    modifierDescription (DraggingVisualizer _) = "DraggingVisualizer"
+    pureModifier (DraggingVisualizer (Just dragged@(draggedWin, _))) _ _ wrs =
+            if draggedWin `elem` (map fst wrs)
+                then (dragged : rest, Nothing)
+                else (wrs, Just $ DraggingVisualizer Nothing)
+        where
+            rest = filter (\(w, _) -> w /= draggedWin) wrs
+    pureModifier _ _ _ wrs = (wrs, Nothing)
+
+    pureMess (DraggingVisualizer _) m = case fromMessage m of
+        Just (DraggingWindow w rect) -> Just $ DraggingVisualizer $ Just (w, rect)
+        Just (DraggingStopped) -> Just $ DraggingVisualizer Nothing
+        _ -> Nothing