^{Originally posted by adam-grant-hendry July 8, 2022}
When using QtInteractor (Windows 10 with PySide6)

from pyvistaqt import MainWindow, QtInteractor
from qtpy import QtWidgets

class Window(MainWindow):
    def __init__(self):
        super().__init__()
        self.setWindowTitle('Example')

        self.layout_ = QtWidgets.QVBoxLayout()

        self.container = QtWidgets.QFrame()
        self.container.setLayout(self.layout_)
        self.setCentralWidget(self.container)

        self.plotter = QtInteractor(parent=self.container)
        self.layout_.addWidget(self.plotter)
        self.plotter.show()

        self.signal_close.connect(self.plotter.close)


app = QtWidgets.QApplication([])
window = Window()
window.show()
app.exec_()

The error:

QPainter::begin: Paint device returned engine == 0, type: 1

appears every time the screen is updated (even if plotter.show() is placed after window.show().

From the PySide6 QPaintEngine docs, the error is saying Qt thinks I am on X11:

• QPaintEngine.X11 == 0
• QPainEngine.Windows == 1

After debugging in VSCode with the following launch.json so the debugger goes into packages:

{
    "configurations": [
        {
            "name": "Python: Current File",
            "type": "python",
            "request": "launch",
            "program": "${file}",
            "console": "integratedTerminal",
            "justMyCode": false
        }
    ],
}

I found the error happens when rwi.py::QVTKRenderWindowInteractor.paintEngine() is called in response to a Paint event:

def paintEngine(self):
    return None

I also noticed pyvistaqt.rwi::QVTKRenderWindowInteractor.__init__() sets widget attribute

self.setAttribute(WidgetAttribute.WA_PaintOnScreen)

From the PySide6 docs, this flag is only supported on X11 and requires returning NULL (None) from paintEngine:

Hence, an alternative is needed for non-X11 systems (Windows, Mac) running PySide for OpenGL to be possible.