setLayout( new GridBagLayout() );
constraints.fill = GridBagConstraints.BOTH;
constraints.weighty = 1.0;
int x, y; // for clarity
constraints.weightx = 0.1;
addGB( new Button("one"), x=0, y=0 );
constraints.weightx = 0.5;
addGB( new Button("two"), ++x, y );
constraints.weightx = 1.0;
addGB( new Button("three"), ++x, y );