Add "Selective" layout modifier

XMonad/Layout/Selective.hs

@@ -0,0 +1,98 @@
+-----------------------------------------------------------------------------
+-- |
+-- Module      :  XMonad.Layout.Selective
+-- Copyright   :  (c) 2009 Max Rabkin
+-- License     :  BSD3-style (see LICENSE)
+--
+-- Maintainer  :  Max Rabkin <max.rabkin@gmail.com>
+-- Stability   :  unstable
+-- Portability :  unportable
+--
+-- Provides a layout modifier that only shows the master pane and windows
+-- around the focussed window.
+--
+-----------------------------------------------------------------------------
+
+{-# LANGUAGE MultiParamTypeClasses,
+             FlexibleInstances,
+             NoMonomorphismRestriction,
+             NamedFieldPuns #-}
+
+module XMonad.Layout.Selective where
+
+import XMonad.Core
+import XMonad.StackSet
+import XMonad.Layout.LayoutModifier
+import Control.Applicative ((<$>))
+
+-- invariant: 0 <= nMaster <= start; 0 <= nRest
+data Selection = Sel { nMaster :: Int, start :: Int, nRest :: Int }
+    deriving (Read, Show, Eq)
+
+select :: Selection -> Stack a -> Stack a
+select (Sel { nMaster, start, nRest }) stk
+    | lups < nMaster
+        = stk { down=take (nMaster - lups - 1) downs ++
+                    (take nRest . drop (start - lups - 1) $ downs) }
+    | otherwise
+        = stk { up=reverse (take nMaster ups ++ drop start ups),
+                down=take (nRest - (lups - start) - 1) downs }
+    where
+        downs = down stk
+        ups = reverse $ up stk
+        lups = length ups
+    
+{-
+select :: Selection -> Stack a -> (Selection, Stack a)
+select sel@(Sel { nMaster, start, nRest }) stk
+    | lups < nMaster   -- the focussed window is in the master pane
+        = let start' = start `min` (lups + ldown - nRest + 1)
+                             `max` nMaster
+            in (sel { start=start' }, 
+                stk { down=take (nMaster - lups - 1) downs ++
+                            (take nRest . drop (start' - lups - 1) $ downs) })
+    | otherwise
+        = let start' = start `min` lups
+                             `max` (lups - nRest + 1) 
+                             `min` (lups + ldown - nRest + 1)
+                             `max` nMaster
+            in (sel { start=start' },
+                stk { up=reverse (take nMaster ups ++ drop start' ups),
+                      down=take (nRest - (lups - start') - 1) downs })
+    where
+        downs = down stk
+        ups = reverse $ up stk
+        lups = length ups
+        ldown = length downs
+-}
+
+updateStart :: Selection -> Stack a -> Int
+updateStart (Sel { nMaster, start, nRest }) stk
+    | lups < nMaster   -- the focussed window is in the master pane
+        = start `min` (lups + ldown - nRest + 1) `max` nMaster
+    | otherwise
+        = start `min` lups 
+                `max` (lups - nRest + 1) 
+                `min` (lups + ldown - nRest + 1) 
+                `max` nMaster
+    where
+        lups = length $ up stk
+        ldown = length $ down stk
+
+update :: Selection -> Stack a -> Selection
+update sel stk = sel { start=updateStart sel stk }
+
+updateAndSelect :: Selection -> Stack a -> Stack a
+updateAndSelect sel stk = select (update sel stk) stk
+
+data Selective a = Selective Selection
+    deriving (Read, Show)
+
+instance LayoutModifier Selective a where
+    modifyLayout (Selective s) w r =
+        runLayout (w { stack = updateAndSelect s <$> stack w }) r
+
+    pureModifier (Selective sel) _ stk wins = (wins, Selective . update sel <$> stk)
+
+selective :: Int -> Int -> l a -> ModifiedLayout Selective l a
+selective m r = ModifiedLayout . Selective $ Sel { nMaster=m, start=m, nRest=r }