[PyQt] QMainWindow bug?

[Erik Janssens]

Hello Nicola,

I'm not sure what happens when you reset the parent of a widget to None,
(wether it then transfers ownership back to python).

If you get that run-time error, this means that qt deleted the widget, this
random effect might have been triggered by the garbage collector.

you can verify this by disabling the garbage collector and see if
it still happens :

import gc
gc.disable()

I'm don't know if this trick with reparenting works, but it looks like
a good trick to have speedups ??

Erik

On Fri, Jan 21, 2011 at 10:21 AM, Mailing List SVR
<lists at svrinformatica.it> wrote:
> Hi Erik,
>
> attacched is a small sample of what I'm doing in my app, I have a dialog
> that require some time to open, to speed up the things I store it in a
> global object and use this global object to reopen the dialog,
>
> this seems to work, I'm reusing the same dialog from different central
> widget, some times (I'm unable to reproduce) I see in the logs:
>
> RuntimeError: underlying C/C++ object has been deleted
>
> so I added a try except when I open the dialog, until today noone
> reported segfault, what do you think about this usage?
>
> thanks
> Nicola
>
> Il giorno ven, 21/01/2011 alle 08.47 +0100, Erik Janssens ha scritto:
>> Hi,
>>
>> I wrote some general documentation around these
>> issues, with regard to Camelot development, but
>> it might be of use to others as well :
>>
>> http://downloads.conceptive.be/downloads/camelot/doc/sphinx/build/advanced/development.html
>>
>> all remarks/corrections are welcome.
>>
>> Regards,
>>
>> Erik
>>
>> On Thu, 2011-01-20 at 10:22 +0100, Mailing List SVR wrote:
>> > Ok, in a my pyqt app (I'm still using pyqt-4.7.x), I have a dialog that
>> > require much time to open so I keep a reference to it in a app global
>> > variable and I use this reference to reopen the dialog after the first
>> > time. This seems to work and the dialog open much quicker, however in
>> > some undeterminated cases I get:
>> >
>> > RuntimeError: underlying C/C++ object has been deleted
>> >
>> > when I get this error I recreate the dialog and update the global
>> > reference,
>> >
>> > can you please explain the right way to keep a reference in python to a
>> > qt object?
>> >
>> > thanks
>> > NIcola
>> >
>> >
>> > Il giorno mer, 19/01/2011 alle 23.47 +0100, Erik Janssens ha scritto:
>> > > there was a change in sip/pyqt from 4.8.1 to 4.8.2 regarding
>> > > the detection of objects deleted by qt but still referenced in
>> > > python (which is the case here).  in 4.8.1 sip/pyqt tried to
>> > > detect this to avoid segfaults.  this detection however brought
>> > > other issues with it, therefor the detection was turned off again
>> > > in 4.8.2
>> > >
>> > > the solution is not to keep references in python of objects
>> > > owned by qt when they might get deleted.
>> > >
>> > > On Wed, Jan 19, 2011 at 12:36 PM, Mailing List SVR
>> > > <lists at svrinformatica.it> wrote:
>> > > > I can confirm the segfault:
>> > > >
>> > > > - linux, kernel 2.6.36
>> > > > - python 2.7.1
>> > > > - pyqt 4.8.2
>> > > > - qt 4.7.1
>> > > >
>> > > > works fine with PySide,
>> > > >
>> > > > Nicola
>> > > >
>> > > >
>> > > > Il giorno mer, 19/01/2011 alle 08.36 +0100, Vicent Mas ha scritto:
>> > > >> 2011/1/18 Nick Gaens <mail at nickgaens.com>:
>> > > >> > - Win7 64bit
>> > > >> > - Python 2.6.6 (r266:84297, Aug 24 2010, 18:46:32) [MSC v.1500 32 bit
>> > > >> > (Intel)] on win32
>> > > >> > - Qt v4.7.0
>> > > >> > - PyQt GPL v4.8.1 for Python v2.6
>> > > >> > Result: no crashes, works like a charm..
>> > > >> >
>> > > >>
>> > > >> Hi,
>> > > >>
>> > > >> I get the crash also on Windows Vista 32bit (again Python 2.6 and PyQt 4.8.2)
>> > > >>
>> > > >> Vicent
>> > > >>
>> > > >
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>> >
>>
>>
>