Updating visibility of dynamically created content - haskell

Question

Duplicating this from github as per #HeinrichApfelmus's suggestion:
This may be just a usage error on my part, but I am noticing a strange phenomenon when trying to set up conditional visibility/layout for dynamically created UI elements (in WX of course). As somewhat of a toy-example, I tried to create a widget that created StaticText elements on the fly and allowed the user to "browse" through these elements through '<' '>' buttons.
The problem I am noting is that all labels are invisible until a new one is created, at which point the current widget in focus becomes visible. Whether this is a bug or just a paradigm I am misusing, or a subtlety with reactive frameworks, I am unsure as to how to resolve this. Here is the code I have at this point, which exhibits the problem:
{-# LANGUAGE RecursiveDo #-}
module Test.Adder where
import Reactive.Banana
import Reactive.Banana.WX
import Graphics.UI.WX.Attributes
import Graphics.UI.WX hiding (Event, newEvent, empty, Identity)
import Graphics.UI.WXCore hiding (Event, Timer, empty, Identity, newEvent)
import Graphics.UI.WXCore.Frame
-- | Combine Unit-Events
anyEvent :: [Event ()] -> Event ()
anyEvent = foldl1 (unionWith (\_ _ -> ()))
-- | Unsugared if-then-else function
if_ :: Bool -> a -> a -> a
if_ True x _ = x
if_ False _ y = y
-- | Apply a function to the value at an index, or return a default value
-- if the index is out of range
(!?) :: (a -> b) -> b -> Int -> ([a] -> b)
(f!? ~y) n xs
| n < 0 = y
| otherwise = case drop n xs of
x:_ -> f x
[] -> y
main :: IO ()
main = start test
create :: Window w -> Int -> Behavior Int -> Event Int -> Event () -> MomentIO (StaticText ())
create t i bi ei eRef = do
let tx = replicate i '\t' ++ show i
x <- liftIO $ staticText t [ text := tx ]
let beq = (==i) <$> bi
let eMe = filterE (==i) ei
sink x [ visible :== beq ]
reactimate (refresh x <$ anyEvent [ eRef, () <$ eMe ])
return x
test :: IO ()
test = do
f <- frame [text := "Test"]
add <- button f [ text := "+" ]
prv <- button f [ text := "<" ]
cur <- staticText f []
nxt <- button f [ text := ">" ]
tab <- panel f [ clientSize := sz 200 300 ]
deb <- staticText f []
ref <- button f [ text := "refresh" ]
let networkDescription :: MomentIO ()
networkDescription = mdo
eAdd <- event0 add command
eRef <- event0 ref command
let bNotFirst = (>0) <$> bCur
bNotLast = (<) <$> bCur <*> bNext
sink prv [ enabled :== bNotFirst ]
sink cur [ text :== show <$> bCur ]
sink nxt [ enabled :== bNotLast ]
ePrev <- event0 prv command
eNext <- event0 nxt command
let eDelta :: Enum n => Event (n -> n)
eDelta = unions [ pred <$ whenE bNotFirst ePrev
, succ <$ whenE bNotLast eNext ]
eChange = flip ($) <$> bCur <#> eDelta
bCur <- stepper 0 $ eChange
(eIndex, bCount) <- mapAccum 0 ((\x -> (x, succ x)) <$ eAdd)
let bView = (\n i -> if_ (n==0) (0) i) <$> bCount <*> bCur
bNext = pred <$> bCount
eCreate = (\n -> create tab n bView eChange $ anyEvent [eRef,eAdd]) <$> eIndex
reCreate <- execute eCreate
bItemer <- accumB id $ flip (.) . (:) <$> reCreate
let bItems = ($[]) <$> bItemer
bThis = (widget!?(nullLayouts!!0)) <$> bCur <*> bItems
sink tab [ layout :== bThis ]
liftIO $ set f [ layout := column 5 [ margin 10 $ row 5 [ widget add
, widget prv
, widget cur
, widget nxt
, widget ref
]
, fill $ widget tab
]
]
network <- compile networkDescription
actuate network
>