private List subplots;

    /** Total weight of all charts. */
    private int totalWeight = 0;

    /** The gap between subplots. */
    private double gap = 5.0;

    /** Temporary storage for the subplot areas. */
    private transient Rectangle2D[] subplotAreas;
    // TODO:  the subplot areas needs to be moved out of the plot into the plot
    //        state

    /**
     * Default constructor.
     */
    public CombinedDomainXYPlot() {
        this(new NumberAxis());