this.setLayoutManager(new StackLayout() {
public void layout(IFigure figure) {
Rectangle r = figure.getClientArea();
List children = figure.getChildren();

IFigure child;
Dimension d;
for (int i = 0; i < children.size(); i++) {
child = (IFigure)children.get(i);
d = child.getPreferredSize(r.width, r.height);
d.width = Math.min(d.width, r.width);
d.height = Math.min(d.height, r.height);
Rectangle childRect = new Rectangle(
r.x + (r.width - d.width)/2,
r.y + (r.height - d.height)/2,
d.width,
d.height);
child.setBounds(childRect);
}
}
});