public double getItemMargin() {
        return this.itemMargin;
    }

    /**
     * Sets the item margin and sends a {@link RendererChangeEvent} to all
     * registered listeners.
     *
     * @param margin  the margin (a percentage).
     *
     * @see #getItemMargin()
     */
    public void setItemMargin(double margin) {
        this.itemMargin = margin;
        fireChangeEvent();