scroll bar

scroll bar

   <graphics> A {widget} found in {graphical user interfaces} and
   used to show and control ("scroll") which portion of a
   document is currently visible in a window.  A window may have
   a horizontal or, most often, vertical scroll bar or both.

   A vertical scroll bar is a narrow strip drawn up the side of
   the window containing a "bubble" whose position in the scroll
   bar represents the position of the visible part within the
   whole document.  By dragging the bubble with the mouse the
   user can scroll the view over the entire document.  Arrow
   buttons are usually provided at the end(s) of the scroll bar
   to allow the window to be scrolled by a small amount, e.g. one
   line of text, in either direction by clicking them with the
   mouse.  Some programs provide a second pair of buttons for
   scrolling a page at a time or some other unit.  Clicking on
   the scroll bar outside the bubble will either, depending on
   the particular {WIMP}, move the bubble to that point or move
   it some amount (typically a screenful) in that direction.

   Different {WIMP} systems define different standards for
   whether scroll bars appear on the left or right, top or bottom
   of the window, and for their behaviour.

   To reduce mouse movement, the up and down scroll buttons
   should either be next to each other at one end of the scroll
   bar (as in {NEXTSTEP}) or should reverse their effect when
   clicked with the right-hand mouse button (as in the {X Window
   System} and {RISC OS}).  The fraction of the scroll bar filled
   by the bubble should indicate the fraction of the document
   visible in the window.

   (1998-06-26)