title: scrollToTop not working correctly in ScrollPanel with RadioBox
body: <p>I'm having a problem with a <code>wxPython</code> scrolled panel which contains a radiobox. The scroll bar jumps to the top when trying to select an item from the radiobox when changing focus from another panel. You then need to scroll and click again. A minimal example which reproduces the problem:</p>
  
  <pre><code>#!/bin/env python
  import wx
  import wx.lib.scrolledpanel as SP
  
  class MyFrame(wx.Frame):
      def __init__(self):
          wx.Frame.__init__(self, None, - 1, "Frame", size=(300, 300))
          self.scrolledPanel = ScrollPanel(self, size=(-1, 200))
          self.panel = PlotTypePanel(self)
          hbox = wx.BoxSizer(wx.VERTICAL)
          hbox.Add(self.scrolledPanel, 0, wx.EXPAND | wx.ALL, 0)
          hbox.Add(self.panel, 1, wx.EXPAND | wx.ALL, 0)
          self.SetSizer(hbox)
  
  class PlotTypePanel(wx.Panel):
      def __init__(self, parent, **kwargs):
          wx.Panel.__init__(self, parent,**kwargs)
          self.anotherradiobox =  wx.RadioBox(self,label='other',    
                                      style=wx.RA_SPECIFY_COLS,
                                      choices=["some", "other", "box"])
  
  class ScrollPanel(SP.ScrolledPanel):
      def __init__(self, parent, **kwargs):
          SP.ScrolledPanel.__init__(self, parent, -1, **kwargs)
          self.parent = parent
          self.SetupScrolling(scroll_x=False, scroll_y=True, scrollToTop=False)
          choices = [l for l in "abcdefghijklmnopqrstuv"]
          self.fieldradiobox = wx.RadioBox(self,label='letters',    
                                      style=wx.RA_SPECIFY_ROWS,
                                      choices=choices)
          vbox = wx.BoxSizer(wx.VERTICAL)
          vbox.Add(self.fieldradiobox, 0, wx.EXPAND|wx.ALL, 10)
          self.SetSizer(vbox)
          self.SetupScrolling(scroll_x=False, scrollToTop=False)
  
  if __name__ == '__main__':
      app = wx.App()
      frame = MyFrame()
      frame.Show(True)
      app.MainLoop() 
  </code></pre>
  
  <p>When I click on the other radio panel and back to the scrolled panel, as here,</p>
  
  <p><a href="https://i.stack.imgur.com/S72pj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/S72pj.png" alt="enter image description here"></a></p>
  
  <p>it jumps to the top and doesn't select the radio button. I've checked and it seems the <code>EVT_COMBOBOX</code> is not triggered by this first click. I've also tried adding <code>scrollToTop=False</code> which didn't help. I'm using Python 2.7.3 with wxPython version 3.0.2.0.</p>