X.L.Magnifier: Add magnify

This more general function subsumes (almost) all previously known
combinators in this library (it is still symmetric with regards to
magnification, as this is what most users want).  Also export some
previously internal (but not crucial to the implementation) types to
make this possible.

XMonad/Layout/Magnifier.hs

@@ -24,6 +24,9 @@ module XMonad.Layout.Magnifier
     ( -- * Usage
       -- $usage
 
+      -- * General combinators
+      magnify,
+
       -- * Magnify Everything
       magnifier,
       magnifierOff,
@@ -39,9 +42,11 @@ module XMonad.Layout.Magnifier
 
       -- * Messages and Types
       MagnifyMsg (..),
+      MagnifyThis(..),
       Magnifier,
     ) where
 
+import Data.Bool (bool)
 import Numeric.Natural (Natural)
 
 import XMonad
@@ -95,13 +100,29 @@ import XMonad.Util.XUtils
 -- For detailed instruction on editing the key binding see
 -- "XMonad.Doc.Extending#Editing_key_bindings".
 
+-- | Add magnification capabilities to a certain layout.
+--
+-- For example, to re-create @'magnifiercz'' 1.3@, you would do
+--
+-- >>> magnify 1.3 (NoMaster 1) On
+--
+magnify
+    :: Rational     -- ^ Amount to magnify both directions
+    -> MagnifyThis  -- ^ What to magnify
+    -> Bool         -- ^ Whether magnification should start out on
+                    --   (@True@) or off (@False@)
+    -> l a          -- ^ Input layout
+    -> ModifiedLayout Magnifier l a
+magnify cz mt start = ModifiedLayout $
+    Mag 1 (fromRational cz, fromRational cz) (bool Off On start) mt
+
 -- | Increase the size of the window that has focus
 magnifier :: l a -> ModifiedLayout Magnifier l a
 magnifier = magnifiercz 1.5
 
 -- | Change the size of the window that has focus by a custom zoom
 magnifiercz :: Rational -> l a -> ModifiedLayout Magnifier l a
-magnifiercz cz = ModifiedLayout (Mag 1 (fromRational cz, fromRational cz) On (All 1))
+magnifiercz cz = magnify cz (All 1) True
 
 -- | Increase the size of the window that has focus, unless if it is one of the
 -- master windows.
@@ -111,7 +132,7 @@ magnifier' = magnifiercz' 1.5
 -- | Increase the size of the window that has focus by a custom zoom,
 -- unless if it is one of the the master windows.
 magnifiercz' :: Rational -> l a -> ModifiedLayout Magnifier l a
-magnifiercz' cz = ModifiedLayout (Mag 1 (fromRational cz, fromRational cz) On (NoMaster 1))
+magnifiercz' cz = magnify cz (NoMaster 1) True
 
 -- | Magnifier that defaults to Off
 magnifierOff :: l a -> ModifiedLayout Magnifier l a
@@ -124,15 +145,15 @@ maxMagnifierOff = magnifierczOff 1000
 
 -- | Like 'magnifiercz', but default to @Off@.
 magnifierczOff :: Rational -> l a -> ModifiedLayout Magnifier l a
-magnifierczOff cz = ModifiedLayout (Mag 1 (fromRational cz, fromRational cz) Off (All 1))
+magnifierczOff cz = magnify cz (All 1) False
 
 -- | Like 'magnifiercz'', but default to @Off@.
 magnifierczOff' :: Rational -> l a -> ModifiedLayout Magnifier l a
-magnifierczOff' cz = ModifiedLayout (Mag 1 (fromRational cz, fromRational cz) Off (NoMaster 1))
+magnifierczOff' cz = magnify cz (NoMaster 1) False
 
 -- | A magnifier that greatly magnifies just the vertical direction
 maximizeVertical :: l a -> ModifiedLayout Magnifier l a
-maximizeVertical = ModifiedLayout (Mag 1 (1,1000) Off (All 1))
+maximizeVertical = ModifiedLayout (Mag 1 (1, 1000) Off (All 1))
 
 data MagnifyMsg = MagnifyMore | MagnifyLess | ToggleOn | ToggleOff | Toggle deriving ( Typeable )
 instance Message MagnifyMsg
@@ -145,14 +166,15 @@ data Magnifier a = Mag
     , zoomFactor :: !(Double, Double)
       -- ^ Zoom-factor in the @x@ and @y@ direction; the window's width and
       --   height will be multiplied by these amounts when magnifying.
-    , toggle     :: !Toggle
+    , toggle :: !Toggle
       -- ^ Whether to magnify windows at all.
     , magWhen :: !MagnifyThis
       -- ^ Conditions when to magnify a given window
     }
     deriving (Read, Show)
 
-data Toggle        = On  | Off      deriving  (Read, Show)
+-- | Whether magnification is currently enabled.
+data Toggle = On | Off deriving (Read, Show)
 
 -- | Which windows to magnify and when to start doing so.  Note that
 -- magnifying will start /at/ the cut-off, so @All 3@ will start
@@ -201,12 +223,12 @@ unlessMaster n mainmod r s wrs = if null (drop (n-1) (up s)) then return (wrs, N
 applyMagnifier :: (Double,Double) -> Rectangle -> t -> [(Window, Rectangle)]
                -> X ([(Window, Rectangle)], Maybe a)
 applyMagnifier z r _ wrs = do focused <- withWindowSet (return . peek)
-                              let mag (w,wr) ws | focused == Just w = ws ++ [(w, fit r $ magnify z wr)]
+                              let mag (w,wr) ws | focused == Just w = ws ++ [(w, fit r $ magnify' z wr)]
                                                 | otherwise         = (w,wr) : ws
                               return (reverse $ foldr mag [] wrs, Nothing)
 
-magnify :: (Double, Double) -> Rectangle -> Rectangle
-magnify (zoomx,zoomy) (Rectangle x y w h) = Rectangle x' y' w' h'
+magnify' :: (Double, Double) -> Rectangle -> Rectangle
+magnify' (zoomx,zoomy) (Rectangle x y w h) = Rectangle x' y' w' h'
     where x' = x - fromIntegral (w' - w) `div` 2
           y' = y - fromIntegral (h' - h) `div` 2
           w' = round $ fromIntegral w * zoomx