检测wx.gizmos.TreeListCtrl列标签单击

Question

如何检测在使用gizmo创建的TreeList中单击了哪个列。以下代码检测到标签区域单击，但我无法获取单击的列。

import wx.gizmos

class MyGizmos(wx.gizmos.TreeListCtrl):
    def __init__(self, parent):
        super(MyGizmos, self).__init__(parent)
        self.AddColumn('vars')
        self.AddColumn('vals')
        self.SetColumnWidth(0, 100)
        self.SetColumnWidth(1, 100)        
        root = self.AddRoot('foodata')
        self.SetItemText(self.AppendItem(root, 'var 1'), 'val 1', 1)
        self.Bind(wx.EVT_LIST_COL_CLICK, self.OnLabel)

    def OnLabel(self, event):
        print 'col label clicked, but which one ???'
        item = event.GetItem()
        print item # prints wx._controls.ListItem
        print item.GetColumn() # always 0
        #print item.GetColumn(0) # fails

class _demo_Frame(wx.Frame):
    def __init__(self):
        wx.Frame.__init__(self, None, title='gizmos label click')
        self.tree = MyGizmos(self)

if __name__ == '__main__':
    app = wx.PySimpleApp()
    frame = _demo_Frame()
    frame.Show()
    app.MainLoop()