[Haskell-cafe] submenu doesn't seem to work properly in wxhaskell

[Maarten]

Dear all,

The following code doesn't seem to work properly. Either the main entry 
(m1/mp1) or it's sub menu entry (ms1/mps1) do not seem to propagate the 
event when pressed. It is possible to make it working by uncomments the 
lines where the menu commands are registered in the frame.

I have the following two questions:
1. Why doesn't the plain code work. Am I missing something or doing 
something wrong?
2. Doesn't registering eventhandlers in the frame introduce a 
memory/resource leak, especially in the case of popups?

Any suggestions or comments appreciated. Thanks.
Kind regards,

Maarten

Code:

<imports>

gui :: IO ()
gui = do
  f <- frame [ text := "Hello world!" ]

  m   <- menuPane [ text := "&Menu" ]
  m1 <- menuItem m [ text := "Menu m1", on command := putStrLn "menu m1"]
--  set f [ on (menu m1) := putStrLn "menu m1" ]
  menuLine m
  sub <- menuPane [text := "Sub menu"]
  ms1 <- menuItem sub [ text := "submenu ms1", on command := putStrLn 
"submenu ms1" ]
--  set f [ on (menu ms1) := putStrLn "submenu ms1" ]
  menuSub m sub [ text := "Sub" ]
  menuItem m [text := "E&xit", on command := close f]

  set f [menuBar := [m], on mouse := mouseEvent f, clientSize := sz 200 
200 ]
  return ()

mouseEvent f eventMouse = do
  case eventMouse of
    MouseRightDown mousePoint _ -> doPopup f mousePoint
    _ -> return ()

doPopup f mousePoint = do
  m <- makePopupMenu f "&Popup" "Doesnt' work..."
  menuPopup m mousePoint f
  objectDelete m

makePopupMenu f c t = do
  mp   <- menuPane [ text := c ]
  mp1 <- menuItem mp [ text := "Popup mp1", on command := putStrLn 
"popup mp1"]
--  set f [ on (menu mp1) := putStrLn "popup mp1" ]
  menuLine mp
  sub <- menuPane [text := "more text"]
  mps1 <- menuItem sub [ text := "Popup mps1", on command := putStrLn 
"popup mps1"]
  menuSub mp sub [ text := "Sub" ]
--  set f [ on (menu mps1) := putStrLn "popup mps1" ]
  return mp