added module X.L.TwoPanePersistent

updated CHANGES.md

CHANGES.md

@@ -109,6 +109,14 @@
 
 ### New Modules
 
+  * `XMonad.Layout.TwoPanePersistent`
+
+    A layout that is like TwoPane but keeps track of the slave window that is
+    currently beside the master. In TwoPane, the default behavior when the master
+    is focused is to display the next window in the stack on the slave pane. This
+    is a problem when a different slave window is selected without changing the stack
+    order.
+
   * `XMonad.Hooks.RefocusLast`
 
     Provides log and event hooks that keep track of recently focused windows on

XMonad/Layout/TwoPanePersistent.hs

@@ -0,0 +1,98 @@
+{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.Layout.TwoPanePersistent
+-- Copyright   :  (c) Chayanon Wichitrnithed
+-- License     :  BSD3-style (see LICENSE)
+--
+-- Maintainer  :  Chayanon Wichitrnithed <namowi@gatech.edu>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- This layout is the same as "XMonad.Layout.TwoPane" except that it keeps track of the slave window
+-- that is alongside the master pane. In other words, it prevents the slave pane
+-- from changing after the focus goes back to the master pane.
+
+-----------------------------------------------------------------------------
+
+
+module XMonad.Layout.TwoPanePersistent
+  (
+    -- * Usage
+    -- $usage
+  TwoPanePersistent(..)
+  ) where
+
+import XMonad.StackSet (focus, up, down, Stack, Stack(..))
+import XMonad hiding (focus)
+
+-- $usage
+-- Import the module in @~\/.xmonad\/xmonad.hs@:
+--
+-- > import XMonad.Layout.TwoPanePersistent
+--
+-- Then add the layout to the @layoutHook@:
+--
+-- > myLayout = TwoPanePersistent Nothing (3/100) (1/2) ||| Full ||| etc..
+-- > main = xmonad def { layoutHook = myLayout }
+
+
+data TwoPanePersistent a = TwoPanePersistent
+  { slaveWin :: (Maybe a)  -- ^ slave window; if 'Nothing' or not in the current workspace,
+                           -- the window below the master will go into the slave pane
+  , dFrac :: Rational -- ^ shrink/expand size
+  , mFrac :: Rational -- ^ initial master size
+  } deriving (Show, Read)
+
+
+instance (Show a, Eq a) => LayoutClass TwoPanePersistent a where
+  doLayout l r s =
+    case reverse (up s) of
+      -- master is focused
+      []         -> return $ focusedMaster l s r
+
+      -- slave is focused
+      (master:_) -> return $ focusedSlave l s r master
+
+
+  pureMessage (TwoPanePersistent w delta split) x =
+    case fromMessage x of
+      Just Shrink -> Just (TwoPanePersistent w delta (split - delta))
+      Just Expand -> Just (TwoPanePersistent w delta (split + delta))
+      _ -> Nothing
+
+  description _ = "TwoPanePersistent"
+
+
+----------------------------------------------------------------------------------------
+
+focusedMaster :: (Eq a) => TwoPanePersistent a -> Stack a -> Rectangle
+              -> ( [(a, Rectangle)], Maybe (TwoPanePersistent a) )
+focusedMaster (TwoPanePersistent w delta split) s r =
+  let (left, right) = splitHorizontallyBy split r in
+      case down s of
+        -- there exist windows below the master
+        (next:_) -> let nextSlave = ( [(focus s, left), (next, right)]
+                                    , Just $ TwoPanePersistent (Just next) delta split )
+                    in case w of
+                      -- if retains state, preserve the layout
+                      Just win -> if win `elem` (down s) && (focus s /= win)
+                                  then ( [(focus s, left), (win, right)]
+                                       , Just $ TwoPanePersistent w delta split )
+                                  else nextSlave
+                      -- if no previous state, default to the next slave window
+                      Nothing -> nextSlave
+
+
+        -- the master is the only window
+        []       -> ( [(focus s, r)]
+                    , Just $ TwoPanePersistent Nothing delta split )
+
+
+
+focusedSlave :: TwoPanePersistent a -> Stack a -> Rectangle -> a
+             -> ( [(a, Rectangle)], Maybe (TwoPanePersistent a) )
+focusedSlave (TwoPanePersistent _ delta split) s r m =
+  ( [(m, left), (focus s, right)]
+  , Just $ TwoPanePersistent (Just $ focus s) delta split )
+  where (left, right) = splitHorizontallyBy split r

xmonad-contrib.cabal

@@ -285,6 +285,7 @@ library
                         XMonad.Layout.ToggleLayouts
                         XMonad.Layout.TrackFloating
                         XMonad.Layout.TwoPane
+                        XMonad.Layout.TwoPanePersistent
                         XMonad.Layout.WindowArranger
                         XMonad.Layout.WindowNavigation
                         XMonad.Layout.WindowSwitcherDecoration