#include <QApplication>
#include <QMainWindow>
#include <QCheckBox>
#include <QVBoxLayout>
#include <QLabel>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QMainWindow w;
    w.setWindowState(Qt::WindowMaximized);

    QWidget centralWidget;

    QCheckBox box("CheckBox");
    QLabel label("Is checked!");

    QHBoxLayout layout(&centralWidget);
    layout.addWidget(&box);
    layout.addWidget(&label);
    layout.addStretch();

    QObject::connect(&box, SIGNAL(toggled(bool)), &label, SLOT(setVisible(bool)));
    label.setVisible(box.isChecked());

    w.setCentralWidget(&centralWidget);

    w.show();
    
    return a.exec();
}