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