make Layouts able to layout whatever they like.

Config.hs

@@ -84,7 +84,7 @@ borderWidth = 1
 -- |
 -- The default set of tiling algorithms
 --
-defaultLayouts :: [Layout]
+defaultLayouts :: [Layout Window]
 defaultLayouts = [ tiled , mirror tiled , full ]
   where
      -- default tiling algorithm partitions the screen into two panes

Operations.hs

@@ -368,14 +368,14 @@ instance Message IncMasterN
 
 -- simple fullscreen mode, just render all windows fullscreen.
 -- a plea for tuple sections: map . (,sc)
-full :: Layout
+full :: Layout a
 full = Layout { doLayout     = \sc (W.Stack f _ _) -> return [(f, sc)]
               , modifyLayout = const (return Nothing) } -- no changes
 
 --
 -- The tiling mode of xmonad, and its operations.
 --
-tall :: Int -> Rational -> Rational -> Layout
+tall :: Int -> Rational -> Rational -> Layout a
 tall nmaster delta frac =
     Layout { doLayout     = \r -> return . ap zip (tile frac r nmaster . length) . W.integrate
            , modifyLayout = \m -> return $ msum [fmap resize     (fromMessage m)
@@ -390,7 +390,7 @@ mirrorRect :: Rectangle -> Rectangle
 mirrorRect (Rectangle rx ry rw rh) = (Rectangle ry rx rh rw)
 
 -- | Mirror a layout, compute its 90 degree rotated form.
-mirror :: Layout -> Layout
+mirror :: Layout a -> Layout a
 mirror (Layout { doLayout = dl, modifyLayout = ml }) =
     Layout { doLayout     = \sc w -> map (second mirrorRect) `fmap` dl (mirrorRect sc) w
            , modifyLayout = fmap (fmap mirror) . ml }

XMonad.hs

@@ -43,7 +43,7 @@ data XState = XState
     , statusGaps   :: ![(Int,Int,Int,Int)] -- ^ width of status bar on each screen
     , mapped       :: !(S.Set Window)      -- ^ the Set of mapped windows
     , waitingUnmap :: !(M.Map Window Int)  -- ^ the number of expected UnmapEvents
-    , layouts      :: !(M.Map WorkspaceId (Layout, [Layout])) }
+    , layouts      :: !(M.Map WorkspaceId (Layout Window, [Layout Window])) }
                        -- ^ mapping of workspaces to descriptions of their layouts
 data XConf = XConf
     { display       :: Display      -- ^ the X11 display
@@ -119,10 +119,10 @@ atom_WM_STATE           = getAtom "WM_STATE"
 -- 'doLayout', a pure function to layout a Window set 'modifyLayout', 
 -- 'modifyLayout' can be considered a branch of an exception handler.
 --
-data Layout = Layout { doLayout     :: Rectangle -> Stack Window -> X [(Window, Rectangle)]
-                     , modifyLayout :: SomeMessage -> X (Maybe Layout) }
+data Layout a = Layout { doLayout     :: Rectangle -> Stack a -> X [(a, Rectangle)]
+                       , modifyLayout :: SomeMessage -> X (Maybe (Layout a)) }
 
-runLayout :: Layout -> Rectangle -> StackOrNot Window -> X [(Window, Rectangle)]
+runLayout :: Layout a -> Rectangle -> StackOrNot a -> X [(a, Rectangle)]
 runLayout l r = maybe (return []) (doLayout l r)
 
 -- | Based on ideas in /An Extensible Dynamically-Typed Hierarchy of Exceptions/,