Add X.L.TrackFloating for tiled-floating focus issues (#4)

XMonad/Layout/TrackFloating.hs

@@ -0,0 +1,83 @@
+{-# LANGUAGE MultiParamTypeClasses, PatternGuards, TypeSynonymInstances #-}
+{- |
+
+Module      :  XMonad.Layout.TrackFloating
+Copyright   :  (c) 2010 Adam Vogt
+License     :  BSD-style (see xmonad/LICENSE)
+
+Maintainer  :  vogt.adam@gmail.com
+Stability   :  unstable
+Portability :  unportable
+
+Layout modifier that tracks focus in the tiled layer while the floating layer
+is in use. This is particularly helpful for tiled layouts where the focus
+determines what is visible.
+
+The relevant bug is Issue 4
+<http://code.google.com/p/xmonad/issues/detail?id=4>. Explanation:
+
+Focus in the tiled layer goes to the first window in the stack (so-called
+master window) when you focus the tiled layer.
+
+See 'trackFloating' for usage.
+
+-}
+module XMonad.Layout.TrackFloating
+    (trackFloating,
+     TrackFloating,
+    ) where
+
+import Control.Monad
+import Data.List
+import qualified Data.Map as M
+
+import XMonad
+import XMonad.Layout.LayoutModifier
+import qualified XMonad.StackSet as W
+
+
+data TrackFloating a = TrackFloating (Maybe Window)
+    deriving (Read,Show)
+
+
+instance LayoutModifier TrackFloating Window where
+    modifyLayoutWithUpdate (TrackFloating mw) ws@(W.Workspace{ W.stack = ms }) r
+      = do
+        winset <- gets windowset
+        let sTotal = W.stack $ W.workspace $ W.current winset
+            newStack
+              -- focus is floating, so use the remembered focus point
+              | Just sTotal' <- sTotal,
+                W.focus sTotal' `M.member` W.floating winset,
+                Just w <- mw,
+                Just s <- ms,
+                Just ns <- find ((==) w . W.focus)
+                    $ zipWith const (iterate W.focusDown' s) (W.integrate s)
+                = Just ns
+              | otherwise
+                = ms
+            newState
+              | Just sTotal' <- sTotal
+                = if W.focus sTotal' `M.member` W.floating winset
+                    then mw
+                    else Just (W.focus sTotal')
+              | otherwise
+                = Nothing
+        ran <- runLayout ws{ W.stack = newStack } r
+        return (ran, guard (newState /= mw) >> Just (TrackFloating newState))
+
+
+{- | Apply to your layout in a config like:
+
+> main = xmonad (defaultConfig{
+>                   layoutHook = trackFloating
+>                       (noBorders Full ||| Tall 1 0.3 0.5),
+>                   ...
+>               })
+
+Interactions with some layout modifiers (ex. decorations, minimizing) are
+unknown but likely unpleasant.
+-}
+trackFloating ::  l a -> ModifiedLayout TrackFloating l a
+trackFloating layout = ModifiedLayout (TrackFloating Nothing) layout
+