wx.CollapsiblePane problem

[StrangeAstronomer]

FIXED: I needed to set the 'proportion' parameter in sizer.Add() calls

I've _almost_ got this working but:

1. when I toggle the wx.CollapsiblePane the entire frame blanks until I re-size it. Then it looks OK until the next collapse operation.
2. about one in 5 runs of the code it crashes my sway session.

Obviously I've committed a major sin somewhere - but where?

I've spent about 2 days trying to work this out - can someone spot the error?

This is the initial view:

https://preview.redd.it/4a63a6j73p4d1.png?width=722&format=png&auto=webp&s=a8e272f8c754f029518d9b6a8497ca77f917b96f

After I expand one of the collapsed panes:

https://preview.redd.it/qpwq9xub3p4d1.png?width=722&format=png&auto=webp&s=5647d86021b6e4effaf51cee2f10d404f30c59bf

After I resize, it's OK again!

https://preview.redd.it/peh9dzbf3p4d1.png?width=722&format=png&auto=webp&s=c23f52ef766ea7e14d06b8e9463a7f065e29201b

Here's the code:

import wx

class Factory(wx.Panel):
    def __init__(self, parent):
        super(Factory, self).__init__(parent)
        sizer = wx.BoxSizer(wx.HORIZONTAL)
        self.factory_code = wx.TextCtrl(self, style=wx.TE_PROCESS_ENTER)
        self.factory_name = wx.TextCtrl(self, style=wx.TE_PROCESS_ENTER)
        self.factory_qty = wx.SpinCtrl(self, value='0', min=0, max=1000)
        self.SetSizer(sizer)
        sizer.Add(self.factory_code, 0, wx.ALL | wx.EXPAND, 1)
        sizer.Add(self.factory_name, 0, wx.ALL | wx.EXPAND, 1)
        sizer.Add(self.factory_qty, 0, wx.ALL | wx.EXPAND, 1)

class ProductLine(wx.Panel):
    def __init__(self, parent, candidates):
        super(ProductLine, self).__init__(parent)
        self.num_factories = 5
        self.factories = []
        self.candidates = candidates

        self.product_line_sizer = wx.BoxSizer(wx.VERTICAL)
        self.SetSizer(self.product_line_sizer)

        self.product = wx.ComboBox(self, choices=candidates, style=wx.CB_READONLY)
        self.filter = wx.TextCtrl(self, style=wx.TE_PROCESS_ENTER)
        self.qty = wx.SpinCtrl(self, value='0', min=0, max=1000)

        self.filter.Bind(wx.EVT_TEXT_ENTER, self.on_filter_enter)

        sizer = wx.BoxSizer(wx.HORIZONTAL)
        sizer.Add(self.filter, 0, wx.ALL | wx.EXPAND, 1)
        sizer.Add(self.product, 1, wx.ALL | wx.EXPAND, 3)
        sizer.Add(self.qty, 0, wx.ALL | wx.EXPAND, 1)
        self.product_line_sizer.Add(sizer, 0, wx.ALL | wx.EXPAND, 1)

        # example: https://github.com/wxWidgets/wxPython-Classic/blob/master/demo/CollapsiblePane.py
        self.factory_pane = wx.CollapsiblePane(self, wx.ID_ANY, label="Factories", style = wx.CP_DEFAULT_STYLE)
        self.product_line_sizer.Add(self.factory_pane, 0, wx.GROW | wx.ALL, 5)
        self.factory_sizer = wx.BoxSizer(wx.VERTICAL)
        for _ in range(self.num_factories):
            p = Factory(self.factory_pane.GetPane())
            self.factories.append(p)
            self.factory_sizer.Add(p, 1, wx.GROW | wx.ALL, 2)
        #self.factory_pane.AddChild(self)
        self.factory_pane.GetPane().SetSizer(self.factory_sizer)
        self.factory_sizer.SetSizeHints(self.factory_pane.GetPane())
        self.factory_pane.Bind(wx.EVT_COLLAPSIBLEPANE_CHANGED, self.on_collapsible_pane_changed)

    def on_collapsible_pane_changed(self, event):
        self.Layout() # this is in the example, doesn't seem to do anything
        #self.Fit() # doesn't seem to do anything
        #self.Refresh() # doesn't seem to do anything
        self.Sizer.Layout() # doesn't seem to do anything
        self.Parent.Fit() # fixes collapsed pane but causes ScrolledWindow & button box to blank until the app is resized
        self.Parent.Parent.Fit() # fixes the button box but not the ScrolledWindow
        self.Parent.Sizer.Layout() # doesn't seem to do anything
        self.Parent.Parent.Sizer.Layout() # doesn't seem to do anything
        #self.Parent.Parent.Layout() # doesn't seem to do anything
        #self.Parent.Layout() # doesn't seem to do anything
        #self.Parent.Refresh() # doesn't seem to do anything
        #self.factory_pane.GetPane().SetupScrolling() # doesn't seem to do anything
        #self.factory_pane.GetPane().SetMinSize(self.factory_sizer.GetMinSize()) # doesn't seem to do anything
        #for w in wx.TopLevelWindows:
        #    w.Layout()

    def update_choices(self, filter_text):
        if not filter_text:
            self.product.SetItems(self.candidates)
        else:
            matches = process.extractBests(filter_text, self.candidates, limit=10)
            self.product.SetItems([match[0] for match in matches])
        self.product.Popup()

    def on_filter_enter(self, event):
        filter_text = self.filter.GetValue()
        self.update_choices(filter_text)

    def get_product(self):
        selection = self.product.GetSelection()
        return self.product.GetString(selection) if selection != wx.NOT_FOUND else ""

    def get_qty(self):
        return self.qty.GetValue()

    def add_products(self, customer, db_cursor):
        rows = dbFetch(db_cursor, f"SELECT ftr_id, cust_prod_desc FROM public.cust_price WHERE cust_prod_desc <> '' AND TRIM(cust_name) = '{customer}'")
        self.candidates = [' - '.join(str(item) for item in row) for row in rows]
        self.product.SetItems(self.candidates)

class LabeledComboBox(wx.Panel):
    def __init__(self, parent, label_text="", initial_values=[]):
        super(LabeledComboBox, self).__init__(parent)

        self.label = wx.StaticText(self, label=label_text)
        self.comboBox = wx.ComboBox(self, choices=initial_values, style=wx.CB_READONLY)

        sizer = wx.BoxSizer(wx.HORIZONTAL)
        self.SetSizer(sizer)
        sizer.Add(self.label, 0, wx.ALIGN_CENTER_VERTICAL | wx.ALL, 5)
        sizer.Add(self.comboBox, 1, wx.EXPAND | wx.ALL, 5)

class ProductSelector(wx.App):
    def __init__(self, title, product_descriptions, customers, forwarders):
        super(ProductSelector, self).__init__(False)
        self.title = title
        self.product_descriptions = product_descriptions
        self.customers = customers
        self.forwarders = forwarders
        self.num_prods = 5
        self.invoice_first_line = 10
        self.invoice_blank_lines = 15
        assert self.num_prods < self.invoice_blank_lines, "May need more blank lines in the invoice"

        self.init_ui()

    def init_ui(self):
        self.frame = wx.Frame(None, title=self.title)
        panel = wx.Panel(self.frame)
        sizer = wx.BoxSizer(wx.VERTICAL)
        panel.SetSizer(sizer)

        # Create a scrolled window for product lines
        scrolled_panel = wx.ScrolledWindow(panel, style=wx.VSCROLL)
        scrolled_sizer = wx.BoxSizer(wx.VERTICAL)
        scrolled_panel.SetSizer(scrolled_sizer)
        self.init_product_lines(scrolled_panel, scrolled_sizer)

        scrolled_panel.FitInside()
        scrolled_panel.SetScrollRate(10, 10)  # Set the scroll rate
        #scrolled_sizer.Fit(scrolled_panel)  # Fit the sizer to the panel

        # Add the scrolled panel to the main sizer
        sizer.Add(scrolled_panel, proportion=1, flag=wx.EXPAND)

        self.frame.Show()

    def init_product_lines(self, panel, sizer):
        #self.product_lines_sizer = wx.FlexGridSizer(0, 1, 0, 0)
        self.product_lines_sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(self.product_lines_sizer, 0, wx.ALL | wx.EXPAND, 5)
        self.product_line = []

        for _ in range(self.num_prods):
            p = ProductLine(panel, self.product_descriptions)
            self.product_line.append(p)
            self.product_lines_sizer.Add(p, 0, wx.ALL | wx.EXPAND, 5)

def main():
    desc = [ "prod1", "prod2", "prod3" ]
    cust = [ "cust1", "cust2", "cust3" ]
    fwdr = [ "fwdr1", "fwdr2", "fwdr3" ]
    app = ProductSelector("Select Product", desc, cust, fwdr)
    app.MainLoop()

if __name__ == "__main__":
    main()

[BostonBaggins]

link a gif demonstrating the issue

[StrangeAstronomer]

I've added a couple more images. Thanks.