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

Demetrius Cassidy dcassidy36 at gmail.com
Thu Apr 7 16:02:04 BST 2011

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.
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