plucky (3) Perspective.3I.gz

NAME

       Perspective - visible portion of an interactor

SYNOPSIS

       #include <InterViews/perspective.h>

DESCRIPTION

       A  perspective  object  describes  which  part  of  an  interactor's total display area is visible in the
       interactor's canvas.  The main use of perspectives is for scrolling, panning,  and  zooming  interactors.
       The member variables (x0, y0) define the origin of the interactor's display area; width and height define
       the total height of the area.  The member variables (curx, cury) define  the  lower-left  corner  of  the
       interactor's  canvas relative to the total area; curwidth and curheight define how much of the total area
       is displayed in the canvas.

       The member variables sx, sy, lx, and ly specify small and large  increments  in  each  dimension.   These
       increments are used by a scroller to implement line and page scrolling.

PUBLIC OPERATIONS

       Perspective()
              Define a new perspective with all member variables initialized to zero.

       void Attach(Interactor*)
              Add  to  the  list  of  interactors  that  are  interested  in  updates to the perspective.  These
              interactors reflect the perspective visually; examples include scrollers and sliders.

       void Detach(Interactor*)
              Remove an interactor from the list of those interested  in  updates.   This  operation  should  be
              called from the interactor's destructor.

       void Init(Coord x0, Coord y0, Coord width, Coord height)
              Initialize the perspective display area.

       void Update()
              Notify  all  the interactors interested in the perspective that it has changed.  The perspective's
              interactor should call Update after modifying its perspective.

SEE ALSO

       Adjuster(3I), Interactor(3I), Panner(3I), Scroller(3I)