title: How do I expand a wx.sizer of a wx.panel when the panel is expanded inside another wx.sizer?
body: <p>I have a wx.Panel that has a GridBagSizer associated with it.  This panel is placed inside another Sizer (BoxSizer), whose add has the expand flag - meaning that the panel takes up the full width of the sizer, which is great. ...But the panel's internal sizer does not fill the panel now.</p>
  
  <p>I've tried setting the internal sizer's flag to wx.Expand|wx.ALL when I add it's components, but that didn't work.  Anybody know how to make sure the sizer stays the same width as it's panel when the panel is expanded?</p>
  
  <p><em>Edit : My code that creates the panel containing the GridBagSizer:</em></p>
  
  <pre><code>def getNewButton(self, bmp1, bmp2, label):
          panel = wx.Panel(self.frame, -1, pos=(0,0), style=wx.BORDER_THEME)
          sizer = wx.GridBagSizer(0, 1)
  
          #The button
          b = buttons.GenBitmapToggleButton(panel, wx.ID_ANY, None)
          self.frame.Bind(wx.EVT_BUTTON, self.OnToggleButton, b)
          b.Bind(wx.EVT_ENTER_WINDOW, self.OnMouseEnter)
          b.Bind(wx.EVT_LEAVE_WINDOW, self.OnMouseLeave)
          mask = wx.Mask(bmp1, wx.BLUE)
          bmp1.SetMask(mask)
          b.SetBitmapLabel(bmp1)
          mask = wx.Mask(bmp2, wx.BLUE)
          bmp2.SetMask(mask)
          b.SetBitmapSelected(bmp2)
          b.SetToggle(False)
          b.SetInitialSize(size = wx.Size(30, 30))
          b.SetBezelWidth(0)
  
          #The Label Button
          l1 = buttons.GenButton(panel, wx.ID_ANY, label, style=wx.BORDER_NONE)
          self.frame.Bind(wx.EVT_BUTTON, self.OnFlatButton, l1)
          l1.Bind(wx.EVT_ENTER_WINDOW, self.OnMouseEnter)
          l1.Bind(wx.EVT_LEAVE_WINDOW, self.OnNonToggleMouseLeave)
  
          sizer.Add(b, wx.GBPosition(0,0))
          sizer.Add(l1, wx.GBPosition(0,1), flag=wx.EXPAND)
  
          panel.SetSizer(sizer)
          sizer.SetSizeHints(panel)
          self.buttonsList.append(ImgToggleButtonComponents(b,panel,l1))
          return panel
  </code></pre>