variable number of windows in master area

Config.hs

@@ -111,6 +111,10 @@ modMask = mod1Mask
 defaultDelta :: Rational
 defaultDelta = 3%100
 
+-- The default number of windows in the master area
+defaultWindowsInMaster :: Int
+defaultWindowsInMaster = 1
+
 -- numlock handling:
 --
 -- The mask for the numlock key. You may need to change this on some systems.
@@ -135,7 +139,9 @@ borderWidth = 1
 
 -- The default set of Layouts:
 defaultLayouts :: [Layout]
-defaultLayouts = [ full, tall defaultDelta (1%2), wide defaultDelta (1%2) ]
+defaultLayouts = [ full,
+                   tall defaultWindowsInMaster defaultDelta (1%2),
+                   wide defaultWindowsInMaster defaultDelta (1%2) ]
 
 --
 -- The key bindings list.
@@ -157,6 +163,9 @@ keys = M.fromList $
     , ((modMask,               xK_h     ), sendMessage Shrink)
     , ((modMask,               xK_l     ), sendMessage Expand)
 
+    , ((modMask .|. shiftMask, xK_j     ), sendMessage (IncMasterN 1))
+    , ((modMask .|. shiftMask, xK_k     ), sendMessage (IncMasterN (-1)))
+
     , ((modMask .|. shiftMask, xK_c     ), kill)
 
     , ((modMask .|. shiftMask, xK_q                     ), io $ exitWith ExitSuccess)

Operations.hs

@@ -101,19 +101,22 @@ sendMessage a = layout $ \x@(l, ls) -> maybe x (flip (,) ls) (modifyLayout l (So
 data Resize = Shrink | Expand deriving Typeable
 instance Message Resize
 
+data IncMasterN = IncMasterN Int deriving Typeable
+instance Message IncMasterN
+
 full :: Layout
 full = Layout { doLayout     = \sc ws -> return [ (w,sc) | w <- ws ]
               , modifyLayout = const Nothing } -- no changes
 
-tall, wide :: Rational -> Rational -> Layout
-wide delta frac = mirrorLayout (tall delta frac)
+tall, wide :: Int -> Rational -> Rational -> Layout
+wide nmaster delta frac = mirrorLayout (tall nmaster delta frac)
 
-tall delta frac = Layout { doLayout = \r w -> return $ zip w $ tile frac r (length w)
-                         , modifyLayout = fmap handler . fromMessage }
+tall nmaster delta frac = Layout { doLayout = \r w -> return $ zip w $ tile frac r nmaster (length w)
+                                 , modifyLayout = \m -> fmap resize (fromMessage m) `mplus` fmap incmastern (fromMessage m) }
 
-    where handler s = tall delta $ (case s of
-                                    Shrink -> (-)
-                                    Expand -> (+)) frac delta
+    where resize Shrink = tall nmaster delta (frac-delta)
+          resize Expand = tall nmaster delta (frac+delta)
+          incmastern (IncMasterN d) = tall (max 1 (nmaster+d)) delta frac
 
 -- | Mirror a rectangle
 mirrorRect :: Rectangle -> Rectangle
@@ -131,9 +134,9 @@ mirrorLayout (Layout { doLayout = dl, modifyLayout = ml }) =
 --  * no windows overlap
 --  * no gaps exist between windows.
 --
-tile :: Rational -> Rectangle -> Int -> [Rectangle]
-tile _ d n | n < 2 = [d]
-tile f r n = r1 : splitVertically (n-1) r2
+tile :: Rational -> Rectangle -> Int -> Int -> [Rectangle]
+tile _ r nmaster n | n <= nmaster = splitVertically n r
+tile f r nmaster n = splitVertically nmaster r1 ++ splitVertically (n-nmaster) r2
     where (r1,r2) = splitHorizontallyBy f r
 
 splitVertically, splitHorizontally :: Int -> Rectangle -> [Rectangle]

tests/Properties.hs

@@ -265,10 +265,10 @@ prop_push_local (x :: T) i = not (member i x) ==> hidden x == hidden (push i x)
 -- some properties for layouts:
 
 -- 1 window should always be tiled fullscreen
-prop_tile_fullscreen rect = tile pct rect 1 == [rect]
+prop_tile_fullscreen rect = tile pct rect 1 1 == [rect]
 
 -- multiple windows 
-prop_tile_non_overlap rect windows = noOverlaps (tile pct rect windows)
+prop_tile_non_overlap rect windows nmaster = noOverlaps (tile pct rect nmaster windows)
   where _ = rect :: Rectangle
 
 pct = 3 % 100