Adjuster   -   button-like   interactors  for  incremental
       scrolling and zooming

SYNOPSIS

       #include <InterViews/adjuster.h>

DESCRIPTION

       Adjuster objects manipulate a perspective using a pushbut-
       ton-like interface.  Adjusters also provide an auto-repeat
       capability.  Depressing and holding down any mouse  button
       on  an  adjuster for a specified time causes it to repeat-
       edly perform its operation.   The  auto-repeat  terminates
       when the button is released.

       Predefined  subclasses  of  Adjuster  include  Zoomer  and
       Mover.  Zoomers  adjust  the  perspective's  curwidth  and
       curheight  members  to  suggest  magnification.   The user
       clicks on a zoomer to magnify or reduce  the  contents  of
       the  interactor  through  its  perspective.   The Enlarger
       zoomer subclass halves the perspective  values  while  the
       Reducer class doubles them.  Movers provide an incremental
       movement of the perspective in  one  of  four  directions;
       left,  right,  down, or up.  The user clicks on a mover to
       move the perspective.

PUBLIC OPERATIONS

       Adjuster(Interactor*, int = NO_AUTOREPEAT)
              Adjuster constructors take a pointer to the  inter-
              actor  whose  perspective  will  be  adjusted and a
              delay (in tenths of a  second)  after  which  auto-
              repeat will begin once the adjuster is ``pressed''.

       virtual void Highlight()
       virtual void UnHighlight()
              These  functions  define  how  the  adjuster  draws
              itself  when  it is pressed.  The adjuster is high-
              lighted when it is pressed with  any  mouse  button
              and unhighlighted when the button is released.  The
              default is to invert the adjuster when highlighted.

PROTECTED OPERATIONS

       virtual void AdjustView(Event&)
              This  function defines how the adjuster adjusts the
              interactor's perspective.  It is called  after  the
              adjuster  is  pressed  and  released, or repeatedly
              during auto-repeat.  Derived classes  should  rede-
              fine  this function to implement the desired behav-
              ior.

DERIVED CLASSES

       Enlarger(Interactor*)
       Reducer(Interactor*)
              by factors of one half and two, respectively.  This
              suggests  to an interactor to enlarge or reduce its
              contents.   Auto-repeat  is   disabled   on   these
              adjusters.

       LeftMover(Interactor*, int delay = NO_AUTOREPEAT)
       RightMover(Interactor*, int delay = NO_AUTOREPEAT)
       DownMover(Interactor*, int delay = NO_AUTOREPEAT)
       UpMover(Interactor*, int delay = NO_AUTOREPEAT)
              These subclasses of Mover adjust the current origin
              of the interactor's perspective by an amount in the
              corresponding  direction.  If the shift key is down
              while the mover is pressed, the amount  corresponds
              to  the  perspective's  lx  or ly member variables;
              otherwise, the sx or sy values are used.

SEE ALSO

       Interactor(3I), Perspective(3I)