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

[Phil Thompson]

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.

Phil