TreeView无法从TreeStore可视化树

Question

当我运行此程序时，treeWiew小部件显示为白色背景，没有别的。我想，这是一个错误，但我不确定。我不想报告一个不是bug的bug。

testTree :: Tree String
testTree =
    (Node "root" 
        [(Node "child" 
            [(Node "rose" []),
            (Node "cry" 
                [(Node "karma" [])])]),
        (Node "future" []),
        (Node "destiny" 
            [(Node "call" []),
            (Node "saw" [])]),
        (Node "reason" [])])

start :: IO ()
start =
    builderNew >>= (\builder ->
        builderAddFromFile builder "graphic.glade" >>
        builderGetObject builder castToWindow "mainWindow" >>= (\window ->
            widgetShowAll window >>
            windowMaximize window >>
            (window `on` deleteEvent) (liftIO (widgetDestroy window >> mainQuit >> return True))) >>
        builderGetObject builder castToTreeView "treeView" >>= (\tv -> 
            treeStoreNew [testTree] >>= (\ts ->
                treeViewSetModel tv ts)) >>
        return ())

gtkmain :: IO ()
gtkmain = 
    initGUI     >>  
    start >>
    mainGUI  

main = gtkmain