Re: wxNotebook and DeleteAllPages()

PyMapper Developer wrote:
> Hello all, 
>     I'm updating older code that was running on python 2.7 and
> wxpython 2.8.12 to now run on python 3.6 and wxPhoenix.  I have run
> into the following error messages:
>
> <class 'wx._core.PaintEvent'> returned a result with an error set
>
> wx._core.wxAssertionError: C++ assertion "(int)m_pages.Count() ==
> (int)::SendMessageW((((HWND)GetHWND())), (0x1300 + 4), 0, 0L)" failed
> at ..\..\src\msw\notebook.cpp(343) in wxNotebook::GetPageCount():
>
> This occurs when I have an active wxNotebook (with any number of
> pages) where I try to create a new page, after having called the
> DeleteAllPages() method.  Did the behavior of wxNotebook change
> somewhere between 2.8.12 and 4.0, or is this a bug in the wxNotebook?
>

It's hard to say for sure but it's possible that there are some internal
values (in wx or the native libs) that are in an inconsistent state
immediately after a DeleteAllPages and the notebook isn't ready for new
pages again until it has cleaned those up. If that's the case then it
may help to not add any new pages until after the pending events have
been processed. Using wx.CallAfter can help you with that.

The fact that the error is detected while the in the wx.PainEvent code
is a red flag for me too... It is possible that the context that you are
calling DeleteAllPages in that is the trouble. Do you call it from the
EVT_PAINT handler? From another thread?

-- 
Robin Dunn
Software Craftsman
http://wxPython.org

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