Hey @DietmarSchwertberger, I think this should finally resolve the issue with CreateAccessible. Do you mind checking? Sorry for the long delay.

I have just downloaded (4, 3, 0, 'a16049+8d28af9e'), but unfortunately it does not work.
GetOrCreateAccessible() still returns None.

This change hasn't been merged yet, so isn't in a snapshot build yet. I'll go ahead and merge it now.

I did download (4, 3, 0, 'a16049+8d28af9e') from the PR wheel, but will check again once the snapshot is built.

Oh. That version didn't make sense as being from the PR, that's why I thought you had downloaded from the snapshot builds server.

However, I noticed you mentioned GetOrCreateAccessible. I only fixed CreateAccessible.

Do you have a code snippet you can share, so I can make sure it works? Not that I'll be able to test it, but just wanting to see how it is supposed to work.

Never mind about the code snippet. I see you provided that in one of the linked issues. I need to double check but it is possible my solution might not work in this case. Need to see compare the generated code with what gets generated just when you add a virtual method.

Thanks for your support.

Yes, it's two steps:
GetOrCreateAccessible() needs to call GetAccessible() if accessibility is implemented / wxUSE_ACCESSIBILITY is defined.
(In wxWidgets, GetOrCreateAccessible is not implemented at all if wxUSE_ACCESSIBILITY is not defined.)
Then GetAccessible needs to be virtual, such that it can be implemented in Python. Otherwise only the empty implementation from C++ would be called.

sip_corewxWindow.cpp looks reasonable, IMHO, but means that on wxPython now GetOrCreateAccessible() is always defined?

    wxAccessible * _wxWindow_GetOrCreateAccessible(wxWindow* self)
    {
        #if wxUSE_ACCESSIBILITY
            return self->GetOrCreateAccessible();
        #else
            wxPyRaiseNotImplemented();
            return NULL;
        #endif
    }

When I install the current snapshot on Windows:

>>> import wx
>>> wx.VERSION
(4, 3, 0, 'a16051+1a5e2cf2')
>>> app = wx.App()
>>> frame = wx.Frame()
>>> frame.GetOrCreateAccessible()
>>>

That means it was compiled with wxUSE_ACCESSIBILITY, right? Otherwise there would be an exception?

On Ubuntu, a build from the master branch shows that both methods are there, while previously the build would not have had them:

>>> import wx
>>> wx.VERSION
(4, 3, 0, 'a1')
>>> app = wx.App()
>>> frame = wx.Frame()
>>> frame.GetOrCreateAccessible()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NotImplementedError
>>> frame.CreateAccessible()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NotImplementedError

For comparison, an old version on Ubuntu, where GetOrCreateAccessible is not available at all:

>>> import wx
>>> wx.VERSION
(4, 2, 1, '')
>>> app = wx.App()
>>> frame = wx.Frame()
>>> frame.GetOrCreateAccessible()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'Frame' object has no attribute 'GetOrCreateAccessible'

So, to summarize: contrary to wxWidgets, we now always have both methods, no matter whether wxUSE_ACCESSIBILITY is defined or not. I hope that this does not cause any problems.
A program can check for accessibility support instead of checking these methods:

>>> wx.USE_ACCESSIBILITY
1

The problem is that CreateAccessible is not virtual.

May initial approach from https://github.com/wxWidgets/Phoenix/pull/2618/changes was this change to tweaker_tools.py:

    if isWindows:
        # does not compile on GTK and macOS.
        publicWindowVirtuals.append( ('CreateAccessible', 'wxAccessible* CreateAccessible()') )

Now we have

    if klass.name not in ['wxWindow', 'wxProgressDialog', 'wxRichTextCtrl']:
        klass.addCppMethod('wxAccessible*', 'CreateAccessible', '()', """\
            #if wxUSE_ACCESSIBILITY
                return self->CreateAccessible();
            #else
                wxPyRaiseNotImplemented();
                return NULL;
            #endif
            """, factory=True)

I don't see where this creates the virtuality, but I'm not a C++ guy.

I will only be online after Easter again. Happy Easter!