NAME

       Adjuster - button-like interactors for incremental scrolling and zooming

SYNOPSIS

       #include <InterViews/adjuster.h>

DESCRIPTION

       Adjuster  objects  manipulate  a perspective using a pushbutton-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 repeatedly 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 interactor 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 highlighted 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 redefine this function  to  implement  the  desired
              behavior.

DERIVED CLASSES

       Enlarger(Interactor*)
       Reducer(Interactor*)
              Enlargers and reducers adjust an interactor's perspective to enlarge and reduce the
              visible area 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)