L.LimitWindows add usage information, functions to modify the limit

XMonad/Layout/LimitWindows.hs

@@ -1,4 +1,4 @@
-{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses #-}
+{-# LANGUAGE FlexibleInstances, MultiParamTypeClasses, DeriveDataTypeable #-}
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  XMonad.Layout.LimitWindows
@@ -13,11 +13,45 @@
 --
 -----------------------------------------------------------------------------
 
-module XMonad.Layout.LimitWindows (limitWindows,limitSlice) where
+module XMonad.Layout.LimitWindows (
+    -- * Usage
+    -- $usage
+
+    -- Layout Modifiers
+    limitWindows,limitSlice,
+
+    -- Change the number of windows
+    increaseLimit,decreaseLimit,setLimit
+    ) where
 
 import XMonad.Layout.LayoutModifier
 import XMonad
 import qualified XMonad.StackSet as W
+import Control.Monad((<=<),guard)
+
+-- $usage
+-- To use this module, add the following import to @~\/.xmonad\/xmonad.hs@:
+--
+-- > import XMonad.Layout.LimitWindows
+--
+-- > myLayout = limitWindows 6 $ Tall 1 0.03 0.5 ||| Full ||| RandomOtherLayout...
+-- > main = xmonad defaultConfig { layoutHook = myLayout }
+--
+-- You may also be interested in dynamically changing the number dynamically,
+-- by binding keys to the 'increaseLimit', 'decreaseLimit', or 'setLimit'
+-- actions.
+--
+-- For detailed instructions on editing your key bindings, see
+-- "XMonad.Doc.Extending#Editing_key_bindings".
+
+increaseLimit :: X ()
+increaseLimit = sendMessage $ LimitChange succ
+
+decreaseLimit :: X ()
+decreaseLimit = sendMessage . LimitChange $ max 1 . pred
+
+setLimit :: Int -> X ()
+setLimit tgt = sendMessage . LimitChange $ const tgt
 
 -- | Only display the first @n@ windows.
 limitWindows :: Int -> l a -> ModifiedLayout LimitWindows l a
@@ -32,8 +66,16 @@ data LimitWindows a = LimitWindows SliceStyle Int deriving (Read,Show)
 
 data SliceStyle = FirstN | Slice deriving (Read,Show)
 
--- do the runLayout call in an environment with only the windows chosen by f ... ?
+data LimitChange = LimitChange { unLC :: (Int -> Int) } deriving (Typeable)
+
+instance Message LimitChange
+
 instance LayoutModifier LimitWindows a where
+     pureMess (LimitWindows s n) =
+        fmap (LimitWindows s) . pos <=< (`app` n) . unLC <=< fromMessage
+      where pos x   = guard (x>=0)     >> return x
+            app f x = guard (f x /= x) >>  return (f x)
+
      modifyLayout (LimitWindows style n) ws r =
         runLayout ws { W.stack = f n `fmap` W.stack ws } r
       where f = case style of
@@ -45,6 +87,7 @@ firstN n st = W.Stack f (reverse u) d
     where (u,f:d) = splitAt (min (n-1) $ length $ W.up st)
                     $ take n $ W.integrate st
 
+-- | A non-wrapping, fixed-size slice of a stack around the focused element
 slice ::  Int -> W.Stack t -> W.Stack t
 slice n (W.Stack f u d) =
         W.Stack f (take (nu + unusedD) u)