Grid  -  displays a grid in a viewer and constrains points
       to lie on it

SYNOPSIS

       #include <Unidraw/grid.h>

DESCRIPTION

       The Grid object performs two functions: it displays a grid
       in  a  viewer,  and  it can constrain points to lie on the
       grid.  The base class draws the grid as a simple array  of
       dots; subclasses can draw arbitrarily complex grids.

PUBLIC OPERATIONS

       Grid(float w, float h, float xincr, float yincr)
              The constructor parameters correspond to a width, a
              height, and independent units of graduation for the
              horizontal  and  vertical axes, all in pixels.  The
              Grid base class employs a  special-purpose  graphic
              to  render  itself, one that draws an array of dots
              based on the information supplied in this construc-
              tor.

       virtual Graphic* GetGraphic()
              Return the graphic used to render the grid.

       virtual void Constrain(Coord&, Coord&)
              Constrain  the given coordinate pair to fall on the
              grid.  The pair is changed to fall on  the  nearest
              grid point by default.

       virtual void Visiblity(boolean)
              Make  the  grid visible (specify true) or invisible
              (specify false).

       virtual boolean IsVisible()
              Return whether the grid is visible or not.

       virtual void SetSpacing(float xincr, float yincr)
              Reset the grid's units of graduation.

PROTECTED OPERATIONS

       Grid(Graphic*)
              The  protected  constructor  allows  subclasses  to
              specify  an  arbitrary  graphic  for  rendering the
              grid.  Subclasses that use  this  constructor  must
              also redefine the Constrain operation.

SEE ALSO

       Graphic(3U), Viewer(3U)