setLayout( new GridBagLayout() );
constraints.weightx = 1.0;
constraints.weighty = 1.0;
constraints.fill = GridBagConstraints.BOTH;
int x, y; // for clarity
constraints.gridheight = 2; // Span two rows
addGB( new Button("one"), x=0, y=0 );
constraints.gridheight = 1; // set it back
addGB( new Button("two"), x=1, y=0 );
addGB( new Button("three"), x=2, y=0 );
constraints.gridwidth = 2; // Span two columns
addGB( new Button("four"), x=1, y=1 );
constraints.gridwidth = 1; // set it back
