[wxPython-users] Re: How to do cleanup when system shutdown closes the app?

[Robin Dunn]

Avery.Andrews at anu.edu.au wrote:
> This thread has been in abeyance for a bit, so I'll review and rephrase.
> I have an app which I want to save its data when the system shuts down,
> as well as when the app itself is explicitly shut down.  It seems like
> processing the EVT_QUERY_END_SESSION ought to be the right thing to do,
> but, on the Windows platform, using Python 2.4.2 and Ansi wxpython 2.6.3.2
> (and various prior versions), this code doesn't produce any dialog window
> on system shutdown:
> 
> class RunnerApp(wx.App):
>     def OnInit(self):
>         frame = RunnerFrame(None, "TreeRunner")
>         self.SetTopWindow(frame)
>         frame.Show(True)
>         self.Bind(wx.EVT_QUERY_END_SESSION, self.Query)
>         return True
> 
>     def Query(self, event):
>         dlg = wx.MessageDialog(self, 'OK to Quit?',
>                                'A Message Box',
>                                 wx.YES_NO
>                                )

AS has already been mentioned you can't use the app as the parent of the 
dialog.  Either change that to None, or save a reference to the frame to 
use.

>         answer =  dlg.ShowModal()
>         dlg.Destroy()
>         if answer!=wx.ID_YES:
>             return 1
>         return 0

Also, the return value of an event handler is ignored.  The way to 
signal that the session should not be ended is to call event.Veto().

> 
> if __name__ == '__main__':
> 
>     app = RunnerApp(redirect=0)
>     app.MainLoop()
> 
> So is it possible that the EVT_QUERY_END_SESSION msg is simply not being
> processed in the Windows version of wxpython?  Or an I making some mistake
> in using it.

As I think I said before, the code is in place and looks like it should 
work fine, but I can't debug it to see what is really happening because 
the debugger gets the WM_QUERYENDSESSION before the debugged app does, 
and so I can't see what's really going on because it either stops the 
shutdown or kills the app and exits.

Please enter a bug report about this with a category of "wxMSW Specific"

-- 
Robin Dunn
Software Craftsman
http://wxPython.org  Java give you jitters?  Relax with wxPython!