clean up Layout.hs, not entirely happy about the impure layouts.

XMonad/Layout.hs

@@ -32,9 +32,110 @@ import Control.Arrow ((***), second)
 import Control.Monad
 import Data.Maybe (fromMaybe)
 
+------------------------------------------------------------------------
+-- | Builtin basic layout algorithms:
+--
+-- > fullscreen mode
+-- > tall mode
+--
+-- The latter algorithms support the following operations:
+--
+-- >    Shrink
+-- >    Expand
+--
+data Resize     = Shrink | Expand   deriving Typeable
+
+-- | You can also increase the number of clients in the master pane
+data IncMasterN = IncMasterN Int    deriving Typeable
+
+instance Message Resize
+instance Message IncMasterN
+
+-- | Simple fullscreen mode, just render all windows fullscreen.
+data Full a = Full deriving (Show, Read)
+
+instance LayoutClass Full a
+
+-- | The builtin tiling mode of xmonad, and its operations.
+data Tall a = Tall Int Rational Rational deriving (Show, Read)
+                        -- TODO should be capped [0..1] ..
+
+-- a nice pure layout, lots of properties for the layout, and its messages, in Properties.hs
+instance LayoutClass Tall a where
+    pureLayout (Tall nmaster _ frac) r s = zip ws rs
+      where ws = W.integrate s
+            rs = tile frac r nmaster (length ws)
+
+    pureMessage (Tall nmaster delta frac) m =
+            msum [fmap resize     (fromMessage m)
+                 ,fmap incmastern (fromMessage m)]
+
+      where resize Shrink             = Tall nmaster delta (max 0 $ frac-delta)
+            resize Expand             = Tall nmaster delta (min 1 $ frac+delta)
+            incmastern (IncMasterN d) = Tall (max 0 (nmaster+d)) delta frac
+
+    description _ = "Tall"
+
+-- | tile.  Compute the positions for windows using the default 2 pane tiling algorithm.
+--
+-- The screen is divided (currently) into two panes. all clients are
+-- then partioned between these two panes. one pane, the `master', by
+-- convention has the least number of windows in it (by default, 1).
+-- the variable `nmaster' controls how many windows are rendered in the
+-- master pane.
+--
+-- `delta' specifies the ratio of the screen to resize by.
+--
+-- 'frac' specifies what proportion of the screen to devote to the
+-- master area.
+--
+tile :: Rational -> Rectangle -> Int -> Int -> [Rectangle]
+tile f r nmaster n = if n <= nmaster || nmaster == 0
+    then splitVertically n r
+    else splitVertically nmaster r1 ++ splitVertically (n-nmaster) r2 -- two columns
+  where (r1,r2) = splitHorizontallyBy f r
+
+--
+-- Divide the screen vertically into n subrectangles
+--
+splitVertically, splitHorizontally :: Int -> Rectangle -> [Rectangle]
+splitVertically n r | n < 2 = [r]
+splitVertically n (Rectangle sx sy sw sh) = Rectangle sx sy sw smallh :
+    splitVertically (n-1) (Rectangle sx (sy+fromIntegral smallh) sw (sh-smallh))
+  where smallh = sh `div` fromIntegral n --hmm, this is a fold or map.
+
+-- Not used in the core, but exported
+splitHorizontally n = map mirrorRect . splitVertically n . mirrorRect
+
+-- Divide the screen into two rectangles, using a rational to specify the ratio
+splitHorizontallyBy, splitVerticallyBy :: RealFrac r => r -> Rectangle -> (Rectangle, Rectangle)
+splitHorizontallyBy f (Rectangle sx sy sw sh) =
+    ( Rectangle sx sy leftw sh
+    , Rectangle (sx + fromIntegral leftw) sy (sw-fromIntegral leftw) sh)
+  where leftw = floor $ fromIntegral sw * f
+
+-- Not used in the core, but exported
+splitVerticallyBy f = (mirrorRect *** mirrorRect) . splitHorizontallyBy f . mirrorRect
+
+------------------------------------------------------------------------
+-- | Mirror a layout, compute its 90 degree rotated form.
+
+-- | Mirror a layout, compute its 90 degree rotated form.
+data Mirror l a = Mirror (l a) deriving (Show, Read)
+
+instance LayoutClass l a => LayoutClass (Mirror l) a where
+    runLayout (W.Workspace i (Mirror l) ms) r = (map (second mirrorRect) *** fmap Mirror)
+                                                `fmap` runLayout (W.Workspace i l ms) (mirrorRect r)
+    handleMessage (Mirror l) = fmap (fmap Mirror) . handleMessage l
+    description (Mirror l) = "Mirror "++ description l
+
+-- | Mirror a rectangle
+mirrorRect :: Rectangle -> Rectangle
+mirrorRect (Rectangle rx ry rw rh) = (Rectangle ry rx rh rw)
 
 ------------------------------------------------------------------------
 -- LayoutClass selection manager
+-- Layouts that transition between other layouts
 
 -- | A layout that allows users to switch between various layout options.
 
@@ -87,96 +188,3 @@ instance (LayoutClass l a, LayoutClass r a) => LayoutClass (Choose l r) a where
     -- The default cases for left and right:
     handleMessage (SLeft  r l) m = fmap (fmap $ SLeft  r) $ handleMessage l m
     handleMessage (SRight l r) m = fmap (fmap $ SRight l) $ handleMessage r m
-
---
--- | Builtin layout algorithms:
---
--- > fullscreen mode
--- > tall mode
---
--- The latter algorithms support the following operations:
---
--- >    Shrink
--- >    Expand
---
-data Resize     = Shrink | Expand   deriving Typeable
-
--- | You can also increase the number of clients in the master pane
-data IncMasterN = IncMasterN Int    deriving Typeable
-
-instance Message Resize
-instance Message IncMasterN
-
--- | Simple fullscreen mode, just render all windows fullscreen.
-data Full a = Full deriving (Show, Read)
-
-instance LayoutClass Full a
-
--- | The inbuilt tiling mode of xmonad, and its operations.
-data Tall a = Tall Int Rational Rational deriving (Show, Read)
-
-instance LayoutClass Tall a where
-    pureLayout (Tall nmaster _ frac) r s = zip ws rs
-      where ws = W.integrate s
-            rs = tile frac r nmaster (length ws)
-
-    pureMessage (Tall nmaster delta frac) m = msum [fmap resize (fromMessage m)
-                                                   ,fmap incmastern (fromMessage m)]
-        where resize Shrink = Tall nmaster delta (max 0 $ frac-delta)
-              resize Expand = Tall nmaster delta (min 1 $ frac+delta)
-              incmastern (IncMasterN d) = Tall (max 0 (nmaster+d)) delta frac
-    description _ = "Tall"
-
--- | Mirror a rectangle
-mirrorRect :: Rectangle -> Rectangle
-mirrorRect (Rectangle rx ry rw rh) = (Rectangle ry rx rh rw)
-
--- | Mirror a layout, compute its 90 degree rotated form.
-data Mirror l a = Mirror (l a) deriving (Show, Read)
-
-instance LayoutClass l a => LayoutClass (Mirror l) a where
-    runLayout (W.Workspace i (Mirror l) ms) r = (map (second mirrorRect) *** fmap Mirror)
-                                                `fmap` runLayout (W.Workspace i l ms) (mirrorRect r)
-    handleMessage (Mirror l) = fmap (fmap Mirror) . handleMessage l
-    description (Mirror l) = "Mirror "++ description l
-
-------------------------------------------------------------------------
-
--- | tile.  Compute the positions for windows using the default 2 pane tiling algorithm.
---
--- The screen is divided (currently) into two panes. all clients are
--- then partioned between these two panes. one pane, the `master', by
--- convention has the least number of windows in it (by default, 1).
--- the variable `nmaster' controls how many windows are rendered in the
--- master pane.
---
--- `delta' specifies the ratio of the screen to resize by.
---
--- 'frac' specifies what proportion of the screen to devote to the
--- master area.
---
-tile :: Rational -> Rectangle -> Int -> Int -> [Rectangle]
-tile f r nmaster n = if n <= nmaster || nmaster == 0
-    then splitVertically n r
-    else splitVertically nmaster r1 ++ splitVertically (n-nmaster) r2 -- two columns
-  where (r1,r2) = splitHorizontallyBy f r
-
---
--- Divide the screen vertically into n subrectangles
---
-splitVertically, splitHorizontally :: Int -> Rectangle -> [Rectangle]
-splitVertically n r | n < 2 = [r]
-splitVertically n (Rectangle sx sy sw sh) = Rectangle sx sy sw smallh :
-    splitVertically (n-1) (Rectangle sx (sy+fromIntegral smallh) sw (sh-smallh))
-  where smallh = sh `div` fromIntegral n --hmm, this is a fold or map.
-
-splitHorizontally n = map mirrorRect . splitVertically n . mirrorRect
-
--- Divide the screen into two rectangles, using a rational to specify the ratio
-splitHorizontallyBy, splitVerticallyBy :: RealFrac r => r -> Rectangle -> (Rectangle, Rectangle)
-splitHorizontallyBy f (Rectangle sx sy sw sh) =
-    ( Rectangle sx sy leftw sh
-    , Rectangle (sx + fromIntegral leftw) sy (sw-fromIntegral leftw) sh)
-  where leftw = floor $ fromIntegral sw * f
-
-splitVerticallyBy f = (mirrorRect *** mirrorRect) . splitHorizontallyBy f . mirrorRect