Accessor of the adjustment slot of the gtk-range class.
The gtk-range-adjustment slot access function gets the gtk-adjustment object which is the "model" object for gtk-range.
The (setf gtk-range-adjustment) slot access function sets the adjustment to be used as the "model" object for this range widget.
The adjustment indicates the current range value, the minimum and maximum range values, the step/page increments used for keybindings and scrolling, and the page size. The page size is normally 0 for gtk-scale and nonzero for gtk-scrollbar, and indicates the size of the visible area of the widget being scrolled. The page size affects the size of the scrollbar slider.