QStatusTipEvent Class

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QWidget *myWidget = new QWidget;
    myWidget->setStatusTip(tr("This is my widget."));

    setCentralWidget(myWidget);
    ...
}

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
{
    QMenu *fileMenu = menuBar()->addMenu(tr("File"));

    QAction *newAct = new QAction(tr("&New"), this);
    newAct->setStatusTip(tr("Create a new file."));
    fileMenu->addAction(newAct);
    ...
}