app_window property returns misleading value in a MultiPlotter setting

[jomade]

In a MultiPlotter, the BackGroundPlotter.app_window property of the children does not contain the application window but a child (or more precise a grandchild)-window of the application window.

It seems the application consists of a Mainwindow that is parent to a QWidget that is parent to the multiple plotters. So each BackgroundPlotter in the MultiPlotter has its own MainWindow which are nested in the application.

I would have expected that:

• Either BackGroundPlotter.app_window always returns the application window independent whether it is nested in a MultiPlotter
• or MultiPlotter would have a MultiPlotter.app_window that contains the reference to the global application window.

Maybe adding a qt_window in the BackGroundplotter which in the MultiplotterCase contains the child-widgets, and for the single-case also contains the app-window and setting the correct app_window could resolve it - however that would be a breaking change if someone already relies on the app_window to return the child-widgets.

Some code to highlight the issue:

import pyvista as pv
from pyvistaqt import BackgroundPlotter, MultiPlotter
from PySide6 import QtGui

print("BackGroundPlotter")
plotter = BackgroundPlotter()
it = plotter.app_window
print(f'plotter.app_window: {str(it)}')
while it.parent():
    print(it.parent())
    it = it.parent()
print('done')

print("MultiPlotter")
mplotter = MultiPlotter(nrows=1, ncols=2)
plotter = mplotter[0, 0]
it = plotter.app_window
print(f'plotter.app_window: {str(it)}')
while it.parent():
    print(it.parent())
    it = it.parent()
print('done')

Which outputs:

BackGroundPlotter
plotter.app_window: <pyvistaqt.window.MainWindow(0x600000325d40) at 0x10a4c7900>
done
MultiPlotter
plotter.app_window: <pyvistaqt.window.MainWindow(0x600000336b80) at 0x12f4eef00>
<PySide6.QtWidgets.QWidget(0x600000336820) at 0x12f4ec6c0>
<pyvistaqt.window.MainWindow(0x6000003370c0) at 0x12f48bf00>
done