Getting QWidget winId

[Neosettler]

Greetings everyone,

I'm trying to convert a piece of code form PySide to PythonQt and I'm having a hard time so far figuring this one out, here is the working PySide version:

def setHandle(self, in_widget):
    import ctypes
    ctypes.pythonapi.PyCObject_AsVoidPtr.restype = ctypes.c_void_p
    ctypes.pythonapi.PyCObject_AsVoidPtr.argtypes = [ctypes.py_object]
    self._winid = ctypes.pythonapi.PyCObject_AsVoidPtr(in_widget.winId())

When translated to PythonQt in_widget.winId() becomes in_widget.winId but I'm getting this error:

TypeError: PyCObject_AsVoidPtr with non-C-object

Anyone could help me clear this up?

Thx

[Neosettler]

So basically, QWidget.winId is not a C-object and not an integer... I'm totally mystified.

[Neosettler]

If I had one last question to ask on this forum it would be this one:

Could anyone share how to pass a widget winId from PyhtonQt to c++?

[Neosettler]

To specified: when winId is cast as a long:

self._winid = long(in_widget.winId)

it returns:
TypeError: long() argument must be a string or a number, not 'builtin_qt_slot'

I also tried to keep the same nomenclature as Qt C++ and retrieve QWidget.data.winid but data is not recognized.

I'm guessing that WId is a special case and I'd be very interested in knowing how to deal with this via PythonQt.

Thx.

[Neosettler]

Also, when using

self._winid = long(in_widget.winId())

I get:

ValueError: Called WId winId(), return type 'WId' is ignored because it is unknown to PythonQt. Probably you should register it using qRegisterMetaType() or add a default constructor decorator to the class.

Maybe someone could point me in the right direction how to accomplish just that?

[Chris Bevan]

Hi,

I don't know much about WId objects I'm afraid - but it looks like that's a QWidget method, so if you're trying to get that into C++, it'd seem easiest to pass the QWidget to C++ and call pWidget->winId() to get the value you're after.

Cheers,
- Chris

[Neosettler]

Hi Chris, thank you for your input,

I guess WId is not very popular in general but still covered by the PySide or PyQt community and I cant find any information on this within PythonQt. I'll think about your suggestion but I basically need to retrieve the WId to send it to C++ via Cython and Qt is unknown to the library I'm sending it to. I think the key is to convert the WId to either a pylong or a c++ void pointer otherwise I'll have to make a major change in my API design.

[Chris Bevan]

Ah, right; I see what you mean. I think Qt probably doesn't cover it too much because it's platform-specific. The docs only seem to say this:

typedef WId
Platform dependent window identifier.

It looks like it's a HWND, so yeah, that does sound like it could be handy elsewhere on Windows.

kernel/qwindowdefs_win.h
118:typedef HWND WId;

You could try calling qRegisterMetaType<WId>() in your C++ code that initialises PythonQt, and see if that works. Some other variant such as qRegisterMetaType<QWidget::WId>("WId") might also help. Otherwise I can't think of much that might be of use, though, sorry.

• Chris

[Florian Link]

PythonQt does not yet support this out-of-the-box.

You can one of the below options:

a) register WId as a basic type in PythonQtMethodInfo.cpp,
but the type will be different on 32bit/64bit and might be different between platforms:

int PythonQtMethodInfo::nameToType(const char* name)
...
// TODO: check for 32/64bit and use a different type
_parameterTypeDict.insert("WId", QMetaType::LongLong);

// alternative, that may work as well:
//_parameterTypeDict.insert("WId", QMetaType::VoidStar);

b) You can patch the generated wrapper slot for QWidget::winId().
Search for winId() in the generated_cpp dir and patch the method to cast/return a void* or a long long or even a pylong created using the Python API.

c) You can also add your own decorator methods to QWidget, see the decorator docs/examples.

No sure if any of those interoperates well with Cython, I never used that.

[Neosettler]

Alright, thank you gentlemen, I'm going to chew on this for a while.