TypeError when returning MimeDataSelection to Python from Qt6

[Phil Thompson]

On 25/12/2025 19:34, Veronica Berglyd Olsen wrote:
> One of the users of my application came across a bug that looks to
> come from PyQt 6.10.0, where the QWidgetTextControl::inputMethodQuery
> returns a mine object wrapped in a struct that PyQt does not know
> about.
> 
> TypeError:
> unable to convert a C++ 'MimeDataSelection' instance to a Python
> object
> 
> The object in question comes from here:
> https://github.com/qt/qtbase/blob/a0cee3e49d7d20c43955bc1fc2a6a9733c8e1a69/src/gui/text/qinputcontrol.cpp#L115
> 
> The TypeError occurs, as far as I can tell, when processing the return
> value from here:
> https://github.com/qt/qtbase/blob/a0cee3e49d7d20c43955bc1fc2a6a9733c8e1a69/src/widgets/widgets/qwidgettextcontrol.cpp#L2193
> 
> The Python code that fails is a QPlainTextEdit with the following
> overload:
> 
>     def inputMethodQuery(self, query: Qt.InputMethodQuery) -> QRect |
> QVariant:
>         """Adjust completion windows for CJK input methods to consider
>         the viewport margins.
>         """
>         if query == QtImCursorRectangle:
>             # See issues #2267 and #2517
>             vM = self.viewportMargins()
>             rect = self.cursorRect()
>             rect.translate(vM.left(), vM.top())
>             return rect
>         return super().inputMethodQuery(query)
> 
> The failure happens on the last line, with the call to
> super().inputMethodQuery(query). It seems to happen when using
> Spotlight on MacOS according to my incoming bug report, but I don't
> have access to a Mac, so can't confirm.
> 
> I'm not very familiar with how PyQt extracts the objects to handle in
> the interface, but I suspect MimeDataSelection that lives entirely
> within the function in the first link is being missed here.
> 
> Veronica Berglyd Olsen

You could try disabling the auto-conversion of QVariants...

     orig_ac = sip.enableautoconversion(QVariant, False)
     variant = super().inputMethodQuery(query)
     sip.enableautoconversion(QVariant, orig_ac)
     return variant

Phil