NAME
       RectFill -- Fill a rectangular region in a rastport.

   SYNOPSIS

        RectFill( rp, xmin, ymin, xmax, ymax)
                 a1  d0:16 d1:16 d2:16 d3:16

        void RectFill( struct rastport *, short, short, short, short );

   FUNCTION
        Fills  the  rectangular  region  specified  by  the
        parameters  with the chosen pen  colors,  areafill
        pattern, and drawing mode. If no areafill pattern is
        specified, fill the rectangular region with the FgPen
        color, taking into account the drawing mode.

   INPUTS
        rp - pointer to a rastport structure
        (xmin,ymin) (xmax,ymax) are the coordinates of the upper
                left corner and the lower right corner, respectively, of the
                rectangle.
   NOTE

        The following relation MUST be true:
                (xmax >= xmin) and (ymax >= ymin)

   BUGS
        Complement mode with FgPen complements all bitplanes.

   SEE ALSO
        areaend() graphics/rastport.h