Description The GtkScrollbar widget is an abstract base class for GtkHScrollbar and GtkVScrollbar. It is not very useful in itself. The position of the thumb in a scrollbar is controlled by the scroll adjustments. See GtkAdjustment for the fields in an adjustment - for GtkScrollbar, the "value" field represents the position of the scrollbar, which must be between the "lower" field and "upper - page_size." The "page_size" field represents the size of the visible scrollable area. The "step_increment" and "page_increment" fields are used when the user asks to step down (using the small stepper arrows) or page down (using for example the PageDown key).