@LuGRU Very cool! I finally was able to pull this off with my promoted widget, whereas other techniques didn't work unless I switched the effect to width/height animation.

// w is my widget QGraphicsOpacityEffect *eff = new QGraphicsOpacityEffect(this); w->setGraphicsEffect(eff); QPropertyAnimation *a = new QPropertyAnimation(eff,"opacity"); a->setDuration(300); a->setStartValue(0); a->setEndValue(1); a->start(QPropertyAnimation::DeleteWhenStopped);