Arbitrary instance for StackSet must set random focus on each workspace

When focus was separated from the stack order on each workspace, we
forgot to update the Arbitrary instance to set random focus. As spotted
by David R, this then invalidates 4 of our QC properties. In particular,
the property involving where focus goes after a random transient
(annoying behaviour) appeared to be correct, but wasn't, due to
inadequate coverage.

This patch sets focus to a random window on each workspace. As a result,
we now catch the focus/raise/delete issue people have been complaining
about.

Lesson: make sure your QuickCheck generators are doing what you think
they are.

darcs-hash:20070508051126-9c5c1-55a0597e6838b35f12b3d348e85360cda6c237ca

1 files changed, 33 insertions, 7 deletions

diff --git a/tests/Properties.hs b/tests/Properties.hs
index 4707305..e7a9854 100644
--- a/tests/Properties.hs
+++ b/tests/Properties.hs
@@ -28,17 +28,26 @@ import qualified Data.Map as M
 -- keeping track of the currently focused workspace, and the total
 -- number of workspaces. If there are duplicates in the list, the last
 -- occurence wins.
-fromList :: (Integral i, Integral j, Ord a) => (i, Int,[[a]]) -> StackSet i j a
-fromList (_,_,[]) = error "Cannot build a StackSet from an empty list"
+fromList :: (Integral i, Integral j, Ord a) => (i, Int, [Maybe a], [[a]]) -> StackSet i j a
+fromList (_,_,_,[]) = error "Cannot build a StackSet from an empty list"
 
-fromList (n,m,xs) | n < 0 || n >= genericLength xs
+fromList (n,m,fs,xs) | n < 0 || n >= genericLength xs
                 = error $ "Cursor index is out of range: " ++ show (n, length xs)
                   | m < 1 || m >  genericLength xs
                 = error $ "Can't have more screens than workspaces: " ++ show (m, length xs)
 
-fromList (o,m,xs) = view o $ foldr (\(i,ys) s ->
-                                  foldr (\a t -> insert a i t) s ys)
-                                      (empty (length xs) m) (zip [0..] xs)
+-- 'o' random workspace
+-- 'fs' random focused window on each workspace
+--
+fromList (o,m,fs,xs) =
+    let s = view o $
+                foldr (\(i,ys) s ->
+                    foldr (\a t -> insert a i t) s ys)
+                        (empty (length xs) m) (zip [0..] xs)
+
+    in foldr (\f s -> case f of
+                            Nothing -> s
+                            Just w  -> raiseFocus w s) s fs
 
 -- ---------------------------------------------------------------------
 
@@ -51,13 +60,30 @@ height :: Int -> T -> Int
 height i w = length (index i w)
 
 -- build (non-empty) StackSets with between 1 and 100 stacks
+--
+-- StackSet
+--  { current :: i
+--  , screen2ws:: !(M.Map j i)          -- ^ screen -> workspace
+--  , ws2screen:: !(M.Map i j)          -- ^ workspace -> screen map
+--  , stacks   :: !(M.Map i ([a], [a])) -- ^ screen -> (floating, normal)
+--  , cache    :: !(M.Map a i)          -- ^ a cache of windows back to their stacks
+--  }
+--
+-- Use 'raiseFocus' to bring focus to the front'
+--
 instance (Integral i, Integral j, Ord a, Arbitrary a) => Arbitrary (StackSet i j a) where
     arbitrary = do
         sz <- choose (1,20)
         n  <- choose (0,sz-1)
         sc <- choose (1,sz)
         ls <- vector sz
-        return $ fromList (fromIntegral n,sc,ls)
+
+        -- pick a random element of each stack to focus.
+        fs <- sequence [ if null s then return Nothing
+                            else liftM Just (elements s)
+                       | s <- ls ]
+
+        return $ fromList (fromIntegral n,sc,fs,ls)
     coarbitrary = error "no coarbitrary for StackSet"
 
 -- Invariants: