wx python 3.0.2 classic: C++ assertion "hWnd" failed at .. in wxWindow::SetFocus(): can't set focus to invalid window

[Mr&Mrs D]

I had a Progress class that was working fine in 2.8.12.1 unicode:

class Progress(bolt.Progress):
    """Progress as progress dialog."""
    def __init__(self,title=_(u'Progress'),message=u' '*60,parent=None,
            style=wx.PD_APP_MODAL|wx.PD_ELAPSED_TIME|wx.PD_AUTO_HIDE|wx.PD_SMOOTH,
            abort=False, onAbort=None):
        if abort:
            style |= wx.PD_CAN_ABORT
            self.fnAbort = onAbort
        self.dialog = wx.ProgressDialog(title,message,100,parent,style)
        self.dialog.SetFocus() #### line 1295 in the traceback is here ####
        bolt.Progress.__init__(self)
        self.message = message
        self.isDestroyed = False
        self.prevMessage = u''
        self.prevState = -1
        self.prevTime = 0

(bolt.Progress has no wx in it)

In 3.02 however blows with:

Traceback (most recent call last):
  File "bash\basher\__init__.py", line 3610, in OnShowPage
    self.currentPage.ShowPanel()
  File "bash\basher\__init__.py", line 2646, in ShowPanel
    fullRefresh, scan_data_dir)
  File "bash\balt.py", line 1571, in _conversation_wrapper
    return func(*args, **kwargs)
  File "bash\bosh\__init__.py", line 5806, in _projects_walk_cache_wrapper
    return func(self, *args, **kwargs)
  File "bash\basher\__init__.py", line 2670, in _refresh_installers_if_needed
    with balt.Progress(_(u'Refreshing Installers...'),u'\n'+u' '*60, abort=canCancel) as progress:
  File "bash\balt.py", line 1295, in __init__
    self.dialog.SetFocus()
  File "C:\_\Python27\lib\site-packages\wx-3.0-msw\wx\_core.py", line 10129, in SetFocus
    return _core_.Window_SetFocus(*args, **kwargs)
wx._core.PyAssertionError: C++ assertion "hWnd" failed at ..\..\src\msw\window.cpp(562) in wxWindow::SetFocus(): can't set focus to invalid window


Now can anyone spot what is invalid about this window ? As seen the Progress is instantiated in:

with balt.Progress(_(u'Refreshing Installers...'),u'\n'+u' '*60, abort=canCancel) as progress:

so parent is None - is it because of that ? However why the change in behavior in 3.0.2 ?

Incidentally if I remove the SetFocus call it goes on to blow in another setFocus call later on:

def doProgress(self,state,message):
    if not self.dialog:
        raise StateError(u'Dialog already destroyed.')
    elif (state == 0 or state == 1 or (message != self.prevMessage) or
        (state - self.prevState) > 0.05 or (time.time() - self.prevTime) > 0.5):
        self.dialog.SetFocus() #### blows here, this self.dialog is really really invalid ####
        if message != self.prevMessage:
            ret = self.dialog.Update(int(state*100),message)
            if not ret[0]:
                if self.onAbort():
                    raise CancelError
        else:
            ret = self.dialog.Update(int(state*100))
            if not ret[0]:
                if self.onAbort():
                    raise CancelError
        self.prevMessage = message
        self.prevState = state
        self.prevTime = time.time()

Not sure if all this hocus pocus is needed or if it could be simplified, but my immediate concern is why the window is invalid.

Code attached too.

[Mr&Mrs D]

Update - I posted a stack overflow question http://stackoverflow.com/q/38012813/281545

Apparently what breaks it (see comments there) is the  wx.PD_APP_MODAL style, I display a Progress dialog _before_ the main window is shown which displays pretty fine __but__ once the window is shown (so wx.PD_APP_MODAL takes effect) the hell breaks loose.

Is is a bug ?

[Mr&Mrs D]

And here is The SSCCE (attached)