QWidget::windowHandle() call raises RuntimeError exception

[jiban]

Hi there, Thank you for the work you've done already. I really appreciate it.

Recently, I wanted to use this PySide6 port of QT ADS for my project, and bumped into an exception.

Traceback (most recent call last):
  File "C:\Users\jakej\Documents\workspace\pythonPlayground\venv\lib\site-packages\matplotlib\backends\backend_qt.py", line 495, in _draw_idle
    if self.height() < 0 or self.width() < 0:
  File "C:\Users\jakej\Documents\workspace\pythonPlayground\venv\lib\site-packages\matplotlib\backends\backend_qt.py", line 262, in showEvent
    window.screenChanged.connect(self._update_screen)
RuntimeError: Internal C++ object (PySide6.QtGui.QWindow) already deleted.

I was using matplotlib chart in the dock. The code that raised exception was following. venv/Lib/site-packages/matplotlib/backends/backend_qt.py

    def showEvent(self, event):
        # Set up correct pixel ratio, and connect to any signal changes for it,
        # once the window is shown (and thus has these attributes).
        window = self.window().windowHandle()
        window.screenChanged.connect(self._update_screen)
        self._update_screen(window.screen())

I investigated the code and found following. When I changed the code like this, it worked.

    def showEvent(self, event):
        # Set up correct pixel ratio, and connect to any signal changes for it,
        # once the window is shown (and thus has these attributes).
        dummy = self.window()  # <=== This is the code I inserted
        window = self.window().windowHandle()
        window.screenChanged.connect(self._update_screen)
        self._update_screen(window.screen())

However, I don't want to modify the code in matplotlib. So I investigate more and suspected that the return value from QWidget.windowHandle() might be lost. Finally I tried inserting following line in bindings.xml.

        <object-type name="CFloatingDockContainer">
            <!-- ... -->
            <declare-function signature="windowHandle()" return-type="QWindow"/>
            <!-- ... -->
        </object-type>

It works!

But I'm not sure if this correction is the way shiboken suggests because I'm not familiar with shiboken. And I don't know the exact mechanism why this should be added though CFloatingDockContainer inherits QWidget. The fact that a macro definition was used might make shiboken confusing.

#include <QWidget>
#define tFloatingWidgetBase QWidget

Could you please look into this issue and clarify what the root cause of it? Or we can just settle down on this declare-function solution.

Thank you for giving your precious attention on reading this issue.

Best regards, Jake