Unsolved Busy progressbar not working in gtk2 style

[mjaga]

I have been playing around with the QProgressBar, which allows you to use it as a busy indicator by setting minimum and maximum, as well as its value, to 0. This works fine with all styles. It looks different in each case but the "busy" look is clearly there. However, using "-style gtk2" (on Ubuntu) simply produces a progress bar which is about 30% filled. Is this a known bug/feature?

[mjaga]

@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();
}