size_t desktopDx = QApplication::desktop()->width(); size_t desktopDy = QApplication::desktop()->height(); size_t windowDx = uiPass.width(); size_t windowDy = uiPass.height(); uiPass.setGeometry((desktopDx-windowDx)/2, (desktopDy-windowDy)/2,windowDx, windowDy);