// ********************************* create_background_graphic

        /// <summary>
        /// Creates the background graphic.
        /// </summary>
        void create_background_graphic()
        {
            if (background != null)
            {
                background = background.DeleteGraphicsBuffer();
            }
            background = new ZeroitWin8ProgressRingGraphicsBuffer();
            background.CreateGraphicsBuffer(control_width,
                                            control_height);
            background.Graphic.SmoothingMode = SmoothingMode.
                                               HighQuality;
        }
        // ********************************** create_indicator_graphic

        /// <summary>
        /// Creates the indicator graphic.
        /// </summary>
        void create_indicator_graphic()
        {
            if (indicator != null)
            {
                indicator = indicator.DeleteGraphicsBuffer();
            }
            indicator = new ZeroitWin8ProgressRingGraphicsBuffer();
            indicator.CreateGraphicsBuffer(control_width,
                                           control_height);
            indicator.Graphic.SmoothingMode = SmoothingMode.
                                              HighQuality;
        }
        // ******************************************** memory_cleanup

        /// <summary>
        /// Memories the cleanup.
        /// </summary>
        void memory_cleanup()
        {
            // DeleteGraphicsBuffer
            // returns null
            if (background != null)
            {
                background = background.DeleteGraphicsBuffer();
            }

            if (indicator != null)
            {
                indicator = indicator.DeleteGraphicsBuffer();
            }
        }