1. Take the mainwindow Qt demo, and modify the createStatusBar routine like so:

//! [32]
void MainWindow::createStatusBar()
//! [32] //! [33]

{ QWidget *w = new QWidget(); statusBar()->addWidget(w, 1); QLabel *l = new QLabel(); statusBar()->addWidget(l, 0); QFrame *frame = new QFrame(this); frame->setFrameStyle(QFrame::VLine); frame->setFrameShadow(QFrame::Plain); statusBar()->addWidget(frame, 0); QLabel *label = new QLabel("00:00"); statusBar()->addWidget(label, 0); statusBar()->showMessage(tr("Ready")); }

//! [33]

2. qmake -spec macx-g++
3. make
4. open mainwindow.app

When the application is run, moving the mouse over the toolbar buttons
quickly results in either a badly drawn status bar, or at times the
app will freeze for a period of a few seconds and the swirly progress
bar on OSX will appear. This only seems to happen in 4.5.x.

(osx 10.4 if that's relevant)