button1.setBounds(new Rectangle(120, 10, 60, 20));
button2.setBounds(new Rectangle(190, 10, 140, 20));
button3.setBounds(new Rectangle(340, 10, 50, 20));
button4.setBounds(new Rectangle(400, 10, 80, 20));
shell.addListener(SWT.Paint, new Listener() {
@Override
public void handleEvent(Event event) {
GC gc = event.gc;
Color foreground = gc.getForeground();
Color background = gc.getBackground();