title: wxpython: how to keep three wxTextCtrls having same size in flexgridsizer
body: <p>I want to use wxpython to implement a GUI that has three <code>wxTextCtrls</code> widgets, and I want to keep them having the same size when I change the size of the window</p>
  
  <p>If I do nothing to these <code>wxTextCtrls</code>, it works well. But when I add many lines of contents in one of these three widgets, like the first one, it's size will be bigger than the others' when I change the size of the window. How could I keep these widgets having same size? Thanks!</p>
  
  <p>(PS: I think the image of the generated GUI could explain my question better, but I can't post image. Sorry)</p>
  
  <p>My code is </p>
  
  <pre><code>import os
  import wx
  
  class My_Gui(wx.Frame):
      def __init__(self, parent, title):
          super(My_Gui, self).__init__(parent, title = title,size=(800,600))
  
          self.InitUI()
          self.Centre()
          self.Show()
  
      def InitUI(self):
  
          my_panel = wx.Panel(self)
  
          hbox = wx.BoxSizer(wx.HORIZONTAL)
  
          fgs = wx.FlexGridSizer(3, 2, 25, 30)
  
          button1 = wx.Button(my_panel, label='button1', size=(120,150))
  
          button2 = wx.Button(my_panel, label='button2', size=(120,150))
  
          button3 = wx.Button(my_panel, label='button3', size=(120,150))
  
  
          self.tc1 = wx.TextCtrl(my_panel, style=wx.TE_MULTILINE | wx.HSCROLL)
          self.tc2 = wx.TextCtrl(my_panel, style=wx.TE_MULTILINE | wx.HSCROLL)
          self.tc3 = wx.TextCtrl(my_panel, style=wx.TE_MULTILINE | wx.HSCROLL)
  
  
          fgs.AddMany([(button1),(self.tc1, 1, wx.EXPAND),  (button2), \
                    (self.tc2, 1, wx.EXPAND), (button3), (self.tc3, 1, wx.EXPAND)])
  
          fgs.AddGrowableRow(2, 1)
          fgs.AddGrowableRow(1, 1)
          fgs.AddGrowableRow(0, 1)
          fgs.AddGrowableCol(1, 1)
  
          hbox.Add(fgs, proportion=1, flag=wx.ALL|wx.EXPAND, border=40)
          my_panel.SetSizer(hbox)
  
  
  if __name__ == "__main__":
      app = wx.App()
      My_Gui(None, title='Example')
      app.MainLoop()
  </code></pre>