[PyQt] Segfault when trying to rely on QStyledItemDelegate.setEditorData/ModelData default behavior

[Phil Thompson]

On 12 Feb 2016, at 5:14 pm, Elvis Stansvik <elvstone at gmail.com> wrote:
> 
> 2016-02-12 17:42 GMT+01:00 Phil Thompson <phil at riverbankcomputing.com>:
>> On 12 Feb 2016, at 2:27 pm, Elvis Stansvik <elvstone at gmail.com> wrote:
>>> 
>>> 2016-02-12 13:35 GMT+01:00 Phil Thompson <phil at riverbankcomputing.com>:
>>>> On 12 Feb 2016, at 12:31 pm, Elvis Stansvik <elvstone at gmail.com> wrote:
>>>>> 
>>>>> 2016-02-12 12:14 GMT+01:00 Phil Thompson <phil at riverbankcomputing.com>:
>>>>>> On 11 Feb 2016, at 8:53 pm, Elvis Stansvik <elvstone at gmail.com> wrote:
>>>>>>> 
>>>>>>> 2016-02-11 21:14 GMT+01:00 Elvis Stansvik <elvstone at gmail.com>:
>>>>>>>> I found the problem, I had forgot to change the user property from
>>>>>>>> dict to QVariant (was testing around).
>>>>>>>> 
>>>>>>>> With the property of type QVariant, it seems to work fine.
>>>>>>> 
>>>>>>> I'm actually still interested in why I need to declare the Qt property
>>>>>>> as QVariant here. Why do I get a segfault if I declare it as dict?
>>>>>>> 
>>>>>>> That is, in the paste
>>>>>>> https://gist.github.com/estan/c051d1f798c4c46caa7d , why must it be
>>>>>>> 
>>>>>>> @pyqtProperty(QVariant, user=True)
>>>>>>> def values(self):
>>>>>>>     return self._values
>>>>>>> 
>>>>>>> and not
>>>>>>> 
>>>>>>> @pyqtProperty(dict, user=True)
>>>>>>> def values(self):
>>>>>>>     return self._values
>>>>>>> 
>>>>>>> ?
>>>>>>> 
>>>>>>> The value I store there (self._values) is a dict after all. Does it
>>>>>>> have something to do with the way in which
>>>>>>> QStyledItemDelegate::setEditorData sets the property?
>>>>>> 
>>>>>> Yes. It passes the address of a QVariant. PyQt uses the type of the property to tell it what to do with the address.
>>>>> 
>>>>> Aha, I think I understand: QStyledItemDelegate::setEditorData wraps
>>>>> the value in a QVariant, and then crashes when trying to set the
>>>>> property, because QVariant can't be converted to dict..?
>>>> 
>>>> A QVariant can be converted to a dict (otherwise your code wouldn't work at all) - but PyQt needs to know that it is a QVariant in the first place.
>>> 
>>> Hm, okay. But my goal was to keep this property as a dict, since
>>> that's the data I'm storing, and not a QVariant. Why can't I declare
>>> the property as a dict (since that's the data the editor is working
>>> with), and then when QStyledItemDelegate::setEditorData sets the
>>> property with a QVariant (which contains my dict), that QVariant is
>>> automatically converted to a dict? (since that's what the property is
>>> declared as).
>>> 
>>> Sorry if I'm a little thick :/
>> 
>> No, I am.
>> 
>> Should be fixed in tonight's snapshot.
> 
> Excellent! :) Since we're basing our product on Debian packaged PyQt,
> I'll just live with having the "transport" QVariant property for now.
> 
> Just out of curiosity, was this a fix of some general problem so to
> speak, or was the fix to add some custom code (to the wrapping of
> QStyledItemDelegate::setEditorData) that handles this particular case?

It was a general problem.

Phil