Thread: [wxhaskell-users] Segmentation fault when setting listbox items within a listbox event handler

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Hi all

If I run the following program:

{-# OPTIONS -fglasgow-exts #-}

module Main where

import Graphics.UI.WX

main = start $
    do w  <- frame [text := "ListBox Event Handling"]
       p  <- panel w []
       listBox  <- multiListBox p [ items := [ "Foobar" ] ]
       set listBox [ on select := do set listBox [ items := [ "foo", "Bar"] ]
                                     propagateEvent
                   ]
       set w [ layout := container p $ widget listBox
             ]

and click on the listbox item "Foobar", the program crashes with:

(L:6279): Gtk-WARNING **: unable to find signal handler for object(GtkListItem:0x8425e40) with func((nil)) and data(0x845ac18)

The problem is that I change the listbox items from within a listbox
event handler. Do anybody know if this expected behavior or is it a bug
somewhere in WxHaskell, Wxwindows, or GTK?

Of cause I can use this clumsy workaround:

main2 = start $
    do w  <- frame [text := "ListBox Event Handling"]
       p  <- panel w []
       listBox  <- multiListBox p [ items := [ "Foobar" ] ]
       let setListBoxItems =
                 mdo t <- timer listBox [ interval := 100
                                        , on command := do set listBox [ items := [ "foo", "Bar"] ]
                                                           objectDelete t
                                        ]
                     return()
       set listBox [ on select := do setListBoxItems
                                     propagateEvent
                   ]
       set w [ layout := container p $ widget listBox
             ]

but I would rather not have to.

Greetings,

Mads Lindstrøm

Thread: [wxhaskell-users] Segmentation fault when setting listbox items within a listbox event handler

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