Improve scroll selection

src/Dodge/Inventory.hs

@@ -152,7 +152,10 @@ changeSwapSelSet yi w
 
 swapSelSet :: (Int -> IS.IntSet -> World -> World) -> World -> World
 swapSelSet f w = fromMaybe w $ do
-    Sel j _ is <- w ^. hud . diSelection
+    Sel j i is' <- w ^. hud . diSelection
+    let is = if IS.null is' 
+        then IS.singleton i
+        else is'
     return $
         if concurrentIS is
             then f j is w
@@ -224,7 +227,10 @@ multiSelScroll' f w = fromMaybe w $ do
     Sel j i is <- w ^. hud . diSelection
     ss <- w ^? hud . diSections . ix j . ssItems
     k <- f i ss
-    let insertordelete = if k `IS.member` is then IS.delete i else IS.insert i . IS.insert k
+    let insertordelete 
+            | not (i `IS.member` is) && k `IS.member` is = IS.delete k
+            | k `IS.member` is = IS.delete i 
+            | otherwise = IS.insert i . IS.insert k
     return $
         w
             & hud . diSelection . _Just . slSet %~ insertordelete