@mjaga Just in case somebody wants to test this, here is a minimal example demonstrating the problem:

#include <QApplication> #include <QProgressBar> int main(int argc, char *argv[]) { QApplication a(argc, argv); a.setStyle("plastique"); /* working... */ // a.setStyle("cleanlooks"); /* working... */ // a.setStyle("Windows"); /* working... */ // a.setStyle("Fusion"); /* working... */ // a.setStyle("gtk2"); /* NOT working! */ QProgressBar pb; pb.setMaximum(0); pb.setMinimum(0); pb.setValue(0); pb.show(); return a.exec(); }