def addResultSubWindow(self, plotWidget): subWindow = QMdiSubWindow(parent=self.getMdiArea()) subWindow.setAttribute(Qt.WA_DeleteOnClose) subWindow.setWidget(plotWidget) subWindow.setOption(QMdiSubWindow.RubberBandResize, True) self.getMdiArea().addSubWindow(subWindow) subWindow.showMaximized() subWindow.activateWindow() subWindow.show() # important! self.show()