public boolean getVerticalAxisTrace() {
        return this.verticalAxisTrace;    
    }
    
    /**
     * A flag that controls trace lines on the vertical axis.
     *
     * @param flag  <code>true</code> enables trace lines for the mouse
     *              pointer on the vertical axis.
     */
    public void setVerticalAxisTrace(boolean flag) {
        this.verticalAxisTrace = flag;