/************************************************************************/
/* Scroll using arrow keys and quit if Escape is pressed                */
/************************************************************************/

smooth_vertical()
        {
        #define KEY_ESC         0x011B
        #define KEY_UP          0x4800
        #define KEY_DOWN        0x5000
        #define KEY_LEFT        0x4B00
        #define KEY_RIGHT       0x4D00
        #define KEY_ENTER       0x1C0D

        int     y = 0, key;
        while((key = get_key()) != KEY_ENTER)
                switch (key)
                    {
                    case KEY_UP:
                        y = (--y) < 0 ? 0 : y;
                        vertical_scroll(y);             /* Scroll up    */
                        break;
                    case KEY_DOWN:
                        vertical_scroll(++y);           /* Scroll down  */
                        break;
                    default:
                        break;
                    }

        vertical_scroll(0);
        }