[wxPython-dev] Problem with MenuItem.Destroy()

[Paul McNett]

Robin Dunn wrote:
> In a nutshell the problem is this:  The wx.MenuItem class isn't able to 
> use the OOR capabilities that I can use for wx.Window and etc., so the 
> normal SWIG proxy mechanisms are used instead.  So that means that each 
> time a wx.MenuItem is returned from a method a new Python proxy object 
> is created for it, even if one wrapping the same C++ object already 
> exists.  Normally this is all transparent and we don't care about it, 
> but object ownership rules are tossing a spanner in the works here... 
> AppendItem takes ownership of the C++ object, so I set a flag that tells 
> the proxy object that it no longer owns the C++ object and so it doesn't 
> try to destroy it when the proxy is GC'd.  However RemoveItem 
> relinquishes ownership of the C++ object, so the proxy used for the 
> return value is set to own the C++ object.  In your original code since 
> you were not assigning the return value proxy to a variable it was 
> getting GC's immediately and so the C++ object was being destroyed. 
> However since the proxy used for the parameter points to the same (now 
> destroyed) C++ object when you try to use it for the next AppendItem you 
> get the segfault.
> 
> Since we know that with RemoveItem that the parameter and the return 
> value will always be the same C++ object I think that there should be a 
> way that I can fix this such that either code snippet will work as 
> expected.  I'll see what I can do.

Thank you for the full explanation Robin. I wish I had more available 
time (as in somebody paying me <g>) in which case I'd start learning the 
wxWidgets internals and be better able to actually assist.

But the main question on my mind now is: what changed in wxPython 
2.7/2.8 versus 2.6 that didn't show these problems?

-- 
pkm ~ http://paulmcnett.com