Bigger matplot figure in a ScrolledWindow or ScrolledPanel

Question

I'd like plot a figure(having many subfigures) in a scrolledwindow(or scrolledpanel).

figure width depends on the width of window and figure height is calculated like width * 2.

if the height of window ls less than width * 2, scrollbar of window is enabled.

with the following code, I checked the size of figure, canvas and window.

the height of figure and figure is bigger than the height of window. but scrollbar is not enabled.

I tried with boxsizer also, but it did not work.

Can you make this code work?

from matplotlib.backends.backend_wxagg import \
      FigureCanvasWxAgg as FigureCanvas, \
      NavigationToolbar2WxAgg as NavigationToolbar
from matplotlib.figure import Figure
import numpy as np
import wx
from wx.lib.scrolledpanel import ScrolledPanel


class MyFrame(wx.Frame):
   def __init__(self, parent, title):
      wx.Frame.__init__(self, parent, id=wx.ID_ANY, title=title, 
            pos=wx.DefaultPosition, size=wx.Size(200, 300))

#     self.T_panel = wx.Panel(self)
#     self.T_wd = wx.ScrolledWindow(self.T_panel, -1, wx.DefaultPosition, 
#           wx.DefaultSize, wx.VSCROLL|wx.ALWAYS_SHOW_SB)
      self.T_wd = ScrolledPanel(self, -1, size=wx.Size(200, 300))
      self.Bind(wx.EVT_SIZE, self.onSize)
      self.T_wd.SetupScrolling()
      self.T_fig = Figure((5.0,5.0), dpi=80)
      self.T_canvas = FigureCanvas(self.T_wd, -1, self.T_fig)
      self.graph = self.T_fig.add_subplot(111)
      self.T_wd.Layout()


   def onSize(self, event):
      size = event.GetSize()
      x = np.arange(5)
      y = np.random.rand(5) * 5.
      self.T_fig.set_size_inches(size[0]/80., size[0]/40.)
      self.T_canvas.SetSize((size[0], size[0]*2))
      self.graph.hold(False)
      self.graph.plot(x,y)
      self.T_canvas.draw()
      self.T_wd.SetSize(size)
      self.T_wd.SetupScrolling()
      print 'event size', size
      print 'fig size', self.T_fig.get_size_inches()*80
      print 'canvas size', self.T_canvas.GetSize()
      print 'window(panel) wize', self.T_wd.GetSize()
      print ''



class my_App(wx.App):
   def OnInit(self):
      frame = MyFrame(None, title = 'test')
      frame.Show(True)
      self.SetTopWindow(frame)
      return True

my_App().MainLoop()