@maximo Ok :) I am going to test again with stylesheets. It would be very nice it it worked as docs says. Or at least to understand why it did not. Update: Ok, one must unpolish/ polish each widget as doing it to Mainwindow doesn't seems to work. But it also works with setStyleSheet(styleSheet()); in MainWindow to reload (whole) style sheet. Update 2: Ok. Having qframes with bool error property. It will update in Designer, if setting it. No code. Sheet on MWindow. So it does work with properties it seems.