Handle empty layout lists

Main.hs

@@ -45,7 +45,8 @@ main = do
     nbc    <- initcolor normalBorderColor
     fbc    <- initcolor focusedBorderColor
 
-    let cf = XConf
+    let safeLayouts = case defaultLayouts of [] -> (full, []); (x:xs) -> (x, xs)
+        cf = XConf
             { display       = dpy
             , xineScreens   = xinesc
             , theRoot       = rootw
@@ -59,7 +60,7 @@ main = do
             }
         st = XState
             { workspace     = W.empty workspaces (length xinesc)
-            , layouts       = M.empty
+            , layouts       = M.fromList [(w, safeLayouts) | w <- [0 .. W workspaces - 1]]
             }
 
     xSetErrorHandler -- in C, I'm too lazy to write the binding

Operations.hs

@@ -48,7 +48,7 @@ refresh = do
 
     flip mapM_ (M.assocs (W.screen2ws ws)) $ \(scn, n) -> do
         let sc        = genericIndex xinesc scn -- temporary coercion!
-            l  = fromMaybe full (do (x:_) <- M.lookup n fls; return x)
+            (Just l)  = fmap fst $ M.lookup n fls
         mapM_ (\(w, rect) -> io $ moveWindowInside d w rect) $ (doLayout l) sc $ W.index n ws
         whenJust (W.peekStack n ws) (io . raiseWindow d)
     whenJust (W.peek ws) setFocus
@@ -73,7 +73,8 @@ clearEnterEvents = do
 -- uppermost.
 --
 switchLayout :: X ()
-switchLayout = layout (\(x:xs) -> xs ++ [x]) -- TODO pattern match here might fail!
+switchLayout = layout (\(x, xs) -> let xs' = xs ++ [x]
+                                   in (head xs', tail xs'))
 
 --
 -- TODO, using Typeable for extensible stuff is a bit gunky. Check --
@@ -85,7 +86,7 @@ switchLayout = layout (\(x:xs) -> xs ++ [x]) -- TODO pattern match here might fa
 data ShrinkOrExpand = Shrink | Expand deriving (Typeable, Eq)
 
 layoutMsg :: Typeable a => a -> X () -- FIXME: The below shouldn't refresh on Nothing
-layoutMsg a = layout $ \x@(l:ls) -> maybe x (:ls) (modifyLayout l (toDyn a))
+layoutMsg a = layout $ \x@(l, ls) -> maybe x (flip (,) ls) (modifyLayout l (toDyn a))
 
 --
 -- Standard layout algorithms:
@@ -139,11 +140,11 @@ tile r (Rectangle sx sy sw sh) (w:s) =
 
 -- | layout. Modify the current workspace's layout with a pure
 -- function and refresh.
-layout :: ([Layout] -> [Layout]) -> X ()
+layout :: ((Layout, [Layout]) -> (Layout, [Layout])) -> X ()
 layout f = do
     modify $ \s ->
         let n          = W.current . workspace $ s
-            fl  = M.findWithDefault defaultLayouts n $ layouts s
+            (Just fl)  = M.lookup n $ layouts s
         in s { layouts = M.insert n (f fl) (layouts s) }
     refresh
 

XMonad.hs

@@ -36,7 +36,8 @@ import qualified Data.Map as M
 -- Just the display, width, height and a window list
 data XState = XState
     { workspace         :: !WindowSet                      -- ^ workspace list
-    , layouts           :: !(M.Map WorkspaceId [Layout])   -- ^ mapping of workspaces 
+    , layouts           :: !(M.Map WorkspaceId (Layout, [Layout]))
+                                                           -- ^ mapping of workspaces 
                                                            -- to descriptions of their layouts
     }