[PyQt] Custom QQuickWindow crashes when created from QML with PyQt 5.8/Qt 5.8

[Arjen Hiemstra]

Hi,

I have attached a minimal test case that crashes when run. The code exposes a 
custom QQuickWindow subclass to QML, then uses QML to instantiate it. I have 
also attached a C++ file which does the same thing as the Python code, but does 
not crash. The same code also works fine when run with PyQt 5.7.1/Qt 5.7.

Additionally, changing all the property assignments to a Component.onCompleted 
signal handler will not crash. But that means manually setting up connections 
for signals, which gets ugly really fast.

This is the backtrace:

#0  0x00007ffff5b26594 in QWindow::screen() const () from /usr/lib/
libQt5Gui.so.5
#1  0x00007ffff5b28e8d in QWindowPrivate::applyCursor() () from /usr/lib/
libQt5Gui.so.5
#2  0x00007ffff5b2a7bb in QWindow::setVisible(bool) () from /usr/lib/
libQt5Gui.so.5
#3  0x00007ffff5b2c7a8 in ?? () from /usr/lib/libQt5Gui.so.5
#4  0x00007fffedb58aa8 in ?? () from /usr/lib/libQt5Qml.so.5
#5  0x00007fffedbd9d3a in ?? () from /usr/lib/libQt5Qml.so.5
#6  0x00007fffedbdd56c in ?? () from /usr/lib/libQt5Qml.so.5
#7  0x00007fffedbded6c in ?? () from /usr/lib/libQt5Qml.so.5
#8  0x00007fffedbdb392 in ?? () from /usr/lib/libQt5Qml.so.5
#9  0x00007fffedbdc104 in ?? () from /usr/lib/libQt5Qml.so.5
#10 0x00007fffedbdd18e in ?? () from /usr/lib/libQt5Qml.so.5
#11 0x00007fffedb5ca67 in QQmlComponentPrivate::beginCreate(QQmlContextData*) 
() from /usr/lib/libQt5Qml.so.5
#12 0x00007fffedb59f69 in QQmlComponent::create(QQmlContext*) () from /usr/
lib/libQt5Qml.so.5
#13 0x00007fffedbd0c83 in QQmlApplicationEnginePrivate::_q_finishLoad(QObject*) 
() from /usr/lib/libQt5Qml.so.5
#14 0x00007fffedbd0e92 in QQmlApplicationEnginePrivate::startLoad(QUrl const&, 
QByteArray const&, bool) () from /usr/lib/libQt5Qml.so.5
#15 0x00007fffedbd0ff0 in QQmlApplicationEngine::load(QString const&) () from 
/usr/lib/libQt5Qml.so.5
#16 0x00007fffedf64390 in meth_QQmlApplicationEngine_load 
(sipSelf=0x7fffee2683a8, sipArgs=0x7fffee222828) at 
sipQtQmlQQmlApplicationEngine.cpp:375
#17 0x00007ffff741891f in _PyCFunction_FastCallDict () from /usr/lib/
libpython3.6m.so.1.0
#18 0x00007ffff7427a0f in ?? () from /usr/lib/libpython3.6m.so.1.0
#19 0x00007ffff73e3d77 in _PyEval_EvalFrameDefault () from /usr/lib/
libpython3.6m.so.1.0
#20 0x00007ffff7427f47 in PyEval_EvalCodeEx () from /usr/lib/libpython3.6m.so.
1.0
#21 0x00007ffff73e3a5b in PyEval_EvalCode () from /usr/lib/libpython3.6m.so.
1.0
#22 0x00007ffff74acdc2 in ?? () from /usr/lib/libpython3.6m.so.1.0
#23 0x00007ffff74af62d in PyRun_FileExFlags () from /usr/lib/libpython3.6m.so.
1.0
#24 0x00007ffff74af817 in PyRun_SimpleFileExFlags () from /usr/lib/
libpython3.6m.so.1.0
#25 0x00007ffff74a46f1 in Py_Main () from /usr/lib/libpython3.6m.so.1.0
#26 0x0000000000400a5d in main ()
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