pyside6-designer custom widget already deleted issue

[Okko Willeboordse]

Running: Python 3.11.1, PySide6==6.4.2 on Windows 11.

Given the following custom widget;

class MyWidget(PySide6.QtWidgets.QCheckBox):

    def _update_screen(self, screen):
        pass

    def showEvent(self, event):
        window = self.window().windowHandle()
        window.screenChanged.connect(self._update_screen)

This widget runs fine when used in an application.

However when this widget is deployed as a custom widget in pyside6-designer and dragged onto a UI, pyside6-designer runs into an exception which is shown when pyside6-designer is stopped;

Error: Traceback (most recent call last):
  File "C:\Temp\designer_issue\widget.py", line 12, in showEvent
    window.screenChanged.connect(self._update_screen)
RuntimeError: Internal C++ object (PySide6.QtGui.QWindow) already deleted.

while executing 'C:\Temp\designer_issue\.venv\Lib\site-packages\PySide6\designer'

The self.window() is;

<PySide6.QtWidgets.QMainWindow(0x1f873cc70a0, name="MDIWindow") at 0x000001F8748946C0>

and the apparently deleted self.window().windowHandle() is;

<PySide6.QtGui.QWindow(0x1f873f47020, name="MDIWindowWindow") at 0x000001F874894740>

Do I need to check if the Internal C++ object is deleted and how do I do this?

As to the origin of the Widget code, see;

matplotlib.backends.backend_qt.FigureCanvasQT