SET(SCROLL_BAR_AUTO_THUMB)
  Enables or disables automatic adjustment of the scroll bar slider.
  Syntax
     SET (SCROLL_BAR_AUTO_THUMB, window, {HORIZONTAL | VERTICAL},
          {ON | OFF})
  Parameters
     SCROLL_BAR_AUTO_THUMB A keyword directing DECTPU to enable or disable
                          automatic adjustment of a scroll bar slider in a
                          DECTPU window.
     window               The window whose scroll bar slider you want DECTPU
                          to adjust.
     HORIZONTAL           A keyword directing DECTPU to set the slider on a
                          horizontal scroll bar.
     VERTICAL             A keyword directing DECTPU to set the slider on a
                          vertical scroll bar.
     ON                   A keyword directing DECTPU to enable automatic
                          adjustment of the scroll bar slider.
     OFF                  A keyword directing DECTPU to disable automatic
                          adjustment of the scroll bar slider.