allocating more size in sizer to wx.CollapsiblePane when expanded

Question

I have several CollapsiblePanes in a vertical BoxSizer. I would like to be able to expand and collapse them without having them run into each other. I am running wxPython 2.8.10.1 on Windows 7.

Runnable sample application demonstrating the problem is below.

import wx

class SampleCollapsiblePane(wx.CollapsiblePane):
    def __init__(self, *args, **kwargs):
        wx.CollapsiblePane.__init__(self,*args,**kwargs)
        sizer = wx.BoxSizer(wx.VERTICAL)
        for x in range(5):
            sizer.Add(wx.Button(self.GetPane(), label = str(x)))
        self.GetPane().SetSizer(sizer)


class Main_Frame(wx.Frame):
    def __init__(self, *args, **kwargs):
        wx.Frame.__init__(self, *args, **kwargs)
        self.main_panel = wx.Panel(self)
        sizer = wx.BoxSizer(wx.VERTICAL)
        for x in range(5):
            sizer.Add(SampleCollapsiblePane(self.main_panel, label = str(x)), 1)
        self.main_panel.SetSizer(sizer)


class SampleApp(wx.App):
    def OnInit(self):
        frame = Main_Frame(None, title = "Sample App")
        frame.Show(True)
        frame.Centre()
        return True

def main():
    app = SampleApp(0)
    app.MainLoop()

if __name__ == "__main__":
    main()

Answer 1

The documentation explicitly states that you should use proportion=0 when adding collapsible panes to a sizer.

http://docs.wxwidgets.org/stable/wx_wxcollapsiblepane.html

So, first, change the 1 at the end of this line to a 0:

sizer.Add(SampleCollapsiblePane(self.main_panel, label = str(x)), 1)

Next, add this to your SampleCollapsiblePane to force the parent frame to re-layout when a pane is collapsed or expanded:

def __init__(...):
    ...
    self.Bind(wx.EVT_COLLAPSIBLEPANE_CHANGED, self.on_change)
def on_change(self, event):
    self.GetParent().Layout()

There might be a better way, but this is what I've got working at the moment. I'm good with wxPython but haven't used CollapsiblePanes before.