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

       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.

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

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.

Grid(floatw,floath,floatxincr,floatyincr)
              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 constructor.

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

       virtualvoidConstrain(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.

       virtualvoidVisiblity(boolean)
              Make the grid visible (specify true) or invisible (specify false).

       virtualbooleanIsVisible()
              Return whether the grid is visible or not.

       virtualvoidSetSpacing(floatxincr,floatyincr)
              Reset the grid's units of graduation.

Graphic(3U), Viewer(3U)

Unidraw                                           30 July 1990                                          Grid(3U)

#include<Unidraw/grid.h>