[PyQt] why do closeEvent and destroyed slot not get called on accepting PyQt4 QDialog?

Demetrius Cassidy dcassidy36 at gmail.com
Thu Apr 7 16:18:29 BST 2011

Sorry found destroyed() - that's what happens when you reply to emails
before you have morning coffee. Anyway I'm not sure why destroyed() is never
fired. I tried your code and even modified it a bit to use the new style
slots and signals but it's not being fired.

Either way, I think the other points I raised in my last email are still
valid. IMHO using destroyed() in python is the wrong approach.

On Thu, Apr 7, 2011 at 11:02 AM, Demetrius Cassidy <dcassidy36 at gmail.com>wrote:

> I truly believe you are approaching this from the wrong angle. If you need
> to know when your QDialog is going away, you override closeEvent and do your
> cleanup from there.
> However, looking through the docs, it does not appear that destroy is
> actually a signal. It's called from the QWidget dtor, so it makes sense that
> if you call destroy(), you get the runtime error because you are deleting
> the C++ object before the Python object. Do not call destroy yourself - call
> self.close and override closeEvent. From there you can accept or reject
> closing the dialog, and do any cleanup prior to your dialog being destroyed.
> From the Qt Docs:
> void QWidget::destroy ( bool destroyWindow = true, bool destroySubWindows =
> true ) [protected]
> Frees up window system resources. Destroys the widget window if
> destroyWindow is true.
> destroy() calls itself recursively for all the child widgets, passing
> destroySubWindows for the destroyWindow parameter. To have more control over
> destruction of subwidgets, destroy subwidgets selectively first.
> This function is usually called from the QWidget destructor.
> On Thu, Apr 7, 2011 at 3:04 AM, Rui DaCosta <ruidc at yahoo.com> wrote:
>> I know it can close it manually, the problem is that this is a
>> simplification of a problem I had, in which we were expecting the QDialog to
>> close as per the docs, but it did not.
>> The *real* problem we are facing, is a bit further down the line, where we
>> are getting the "RuntimeError: underlying C/C++ object has been deleted"
>> but we never receive a destroyed signal.
>> The only reason I need this signal or event is to do some teardown code
>> for some callbacks to avoid getting this c++ error elsewhere.
>> ------------------------------
>> *From:* Demetrius Cassidy <dcassidy36 at gmail.com>
>> *To:* RuiDC <ruidc at yahoo.com>
>> *Sent:* Thu, 7 April, 2011 0:39:33
>> *Subject:* Re: [PyQt] why do closeEvent and destroyed slot not get called
>> on accepting PyQt4 QDialog?
>> If you want to close, just call self.close. It's a slot, so you can map it
>> to any signal. Also not sure why you want to know when your widget is
>> destroyed? Let Python take care of it, you should not need to call
>> sip.delete yourself. closeEvent is there if you need to know _when_ your app
>> was requested to close. If you want to allow or reject closing the app, you
>> need to use the QEvent object which gets passed to that function.
>> On Wed, Apr 6, 2011 at 5:27 PM, RuiDC <ruidc at yahoo.com> wrote:
>>> The question & code are here:
>>> http://stackoverflow.com/questions/5570402/why-do-closeevent-and-destroyed-slot-not-get-called-on-accepting-pyqt4-qdialog
>>> but hopefully someone here can give me an answer on:
>>> 1. how to get the closeEvent to fire from accepting (or do I have to do a
>>> self.close()?)
>>> 2. how to get the destroyed message to print (or do I have to go through
>>> sip.delete(my_widget)?)
>>> 3. why, if I comment out the del my_widget, and uncomment the
>>> my_widget.destroy() I get a:
>>> RuntimeError: underlying C/C++ object has been deleted
>>> on the destroy() without the print!  i.e. how is it that it can be
>>> destroyed
>>> but not raise the signal?
>>> Thanks in advance,
>>> R
>>> --
>>> View this message in context:
>>> http://old.nabble.com/why-do-closeEvent-and-destroyed-slot-not-get-called-on-accepting-PyQt4-QDialog--tp31336229p31336229.html
>>> Sent from the PyQt mailing list archive at Nabble.com.
>>> _______________________________________________
>>> PyQt mailing list    PyQt at riverbankcomputing.com
>>> http://www.riverbankcomputing.com/mailman/listinfo/pyqt
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.riverbankcomputing.com/pipermail/pyqt/attachments/20110407/9119ffeb/attachment.html>

More information about the PyQt mailing list