gistfile1.txt

from PySide2 import QtCore, QtGui, QtWidgets
from maya import OpenMayaUI as omui
from shiboken2 import wrapInstance

class ClosingWindow(QtGui.QWindow):
    def eventFilter(self, object, event):
        # Prevent this window from being closed.  It should stay alive until Maya exits.
        if object is self and event.type() == QtCore.QEvent.Close:
            return True

        return False

    def __init__(self):
        super().__init__()

        # Try to stay hidden and at the end of alt-tab, but make sure we have an alt-tab entry.
        self.setTitle('Closing...')
        self.setFlags(QtCore.Qt.Dialog|QtCore.Qt.Window|QtCore.Qt.WindowStaysOnBottomHint)
        self.installEventFilter(self)

class MainWindowFilter(QtCore.QObject):
    def eventFilter(self, object, event):
        # Open CloseWindow when the main Maya window is closed.
        global window
        if event.type() == QtCore.QEvent.Close:
            window = ClosingWindow()
            window.show()
            window.setVisibility(QtGui.QWindow.Minimized)

        return False

    def __init__(self):
        super().__init__()
        main_window = omui.MQtUtil.mainWindow()
        window = wrapInstance(int(main_window), QtWidgets.QMainWindow)
        window.window().installEventFilter(self)

def go():
    global filter
    filter = MainWindowFilter()