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-rw-r--r--StackSet.hs31
1 files changed, 27 insertions, 4 deletions
diff --git a/StackSet.hs b/StackSet.hs
index 89a8484..a7bc376 100644
--- a/StackSet.hs
+++ b/StackSet.hs
@@ -24,7 +24,7 @@
module StackSet where
import Data.Maybe
-import qualified Data.List as L (delete,genericLength)
+import qualified Data.List as L (delete,genericLength,elemIndex)
import qualified Data.Map as M
------------------------------------------------------------------------
@@ -216,12 +216,35 @@ raiseFocus k w = case M.lookup k (cache w) of
Nothing -> w
Just i -> (view i w) { focus = M.insert i k (focus w) }
--- | Cycle the current stack ordering. In tiled mode has the effect of
--- moving a new window into the master position, without changing focus.
-promote :: StackSet a -> StackSet a
+-- | Swap the currently focused window with the master window (the
+-- window on top of the stack). Focus moves to the master.
+promote :: Ord a => StackSet a -> StackSet a
+promote w = maybe w id $ do
+ a <- peek w -- fail if null
+ let w' = w { stacks = M.adjust (\s -> swap a (head s) s) (current w) (stacks w) }
+ return $ insert a (current w) w' -- and maintain focus
+
+--
+-- | Swap first occurences of 'a' and 'b' in list.
+-- If both elements are not in the list, the list is unchanged.
+--
+swap :: Eq a => a -> a -> [a] -> [a]
+swap a b xs
+ | a == b = xs -- do nothing
+ | Just ai <- L.elemIndex a xs
+ , Just bi <- L.elemIndex b xs = insertAt bi a (insertAt ai b xs)
+ where
+ insertAt n x ys = as ++ x : tail bs
+ where (as,bs) = splitAt n ys
+
+swap _ _ xs = xs -- do nothing
+
+{-
+-- cycling:
promote w = w { stacks = M.adjust next (current w) (stacks w) }
where next [] = []
next xs = last xs : init xs
+-}
-- |
elemAfter :: Eq a => a -> [a] -> Maybe a