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

Elvis Stansvik elvstone at gmail.com
Fri Feb 12 14:27:34 GMT 2016

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 :/


> Phil

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