QState *s3 = new QState();
s3->assignProperty(label, "text", "In s3");
QMessageBox *mbox = new QMessageBox(mainWindow);
mbox->addButton(QMessageBox::Ok);
mbox->setText("Interrupted!");
mbox->setIcon(QMessageBox::Information);
QObject::connect(s3, SIGNAL(entered()), mbox, SLOT(exec()));
s3->addTransition(s1h);
machine.addState(s3);

s1->addTransition(interruptButton, SIGNAL(clicked()), s3);@

//------------

this snippet from Qt document about QHistoryState

i wonder to know one of statements : s3->addTransition(s1h);

how the s3 state transition to s1h (QHistoryState) without signal or event,
it should be some thing like that: s3->addTransition( button, SIGNAL(clicked(), s1h) );