QWidget::repaint does not immediately call paintEvent on Mac

According to the documentation, QWidget::repaint should immediately call QWidget::paintEvent. (As opposed to QWidget::update, which puts a paint request on the event loop.) I am seeing this behavior on Windows, but on Mac, repaint appears to behave identically to update, i.e. it postpones the paint request until later.

#include <QtGui>

class MyWidget : public QWidget {
  Q_OBJECT
public slots:
  void DoRepaint() {
    QUuid id(QUuid::createUuid());
    qDebug() << "Before repaint call" << id;
    repaint();
    qDebug() << "After repaint call" << id;
  }

protected:
  void paintEvent(QPaintEvent *event) {
    qDebug() << "paintEvent";
    QWidget::paintEvent(event);
  }
};

int main(int argc, char** argv) {
  QApplication app(argc, argv);

  MyWidget w;
  w.show();

  QTimer timer;
  timer.connect(&timer, SIGNAL(timeout()), &w, SLOT(DoRepaint()));
  timer.start(1000);

  return app.exec();
}

#include "main.moc"

The expected output (which happens on Windows and X11) would be:

Before repaint call "{2463f6a3-85b6-4ba8-b886-6e11910916e8}" 
paintEvent
After repaint call "{2463f6a3-85b6-4ba8-b886-6e11910916e8}" 

The actual output is:

Before repaint call "{2463f6a3-85b6-4ba8-b886-6e11910916e8}" 
After repaint call "{2463f6a3-85b6-4ba8-b886-6e11910916e8}" 
paintEvent 

If I call qApp->processEvents() immediately after the repaint, then it works. But this obviously has other side-effects. In this sample application it is no big deal, but in my actual application I need an immediate repaint; an update will not do.

I am also seeing similar behavior in X11, although this sample code works there. I was not able to create a simple application that could reproduce the behavior, but X11 has a similar problem where you must call qApp->syncX() to get the repaint to take effect.