Overview
Declared in "polygon.h"
Base class. Declared in namespace tal.
This is a basic twodimensional polygon class.
This class uses some C functions from the GPC (Generic Polygon Clipper)
library by Alan Murta, Advanced
Interfaces Group, University of Manchester. The GPC library is declared
in the namespace gpc.
Note that you do not need to understand the GPC
library to use this polygon class.
Construction, Assignment and Destruction
polygon()
Constructs a polygon object.
polygon(const polygon &rhs)
Copy constructor.
polygon &operator=(const polygon &rhs)
Assignment operator.
virtual ~polygon()
Destroys the polygon object.
Polygon Vertices
int Count() const
Number of vertices (n) the polygon has.
POINT &operator[](int nIdx)
Returns a reference to a specified polygon vertex. Argument nIdx
is a zerobased index of the polygon vertices. If nIdx exceeds
the total number of vertices minus 1 (n  1), new vertices are
added to the polygon until nIdx equals (n  1). Added vertices
will have default values of (0, 0).
const POINT At(int nIdx) const
Returns a copy of a specified polygon vertex. Argument nIdx is
a zerobased index of the polygon vertices. Unlike the overloaded subscript
operator[], no new vertices will be added if nIdx exceeds
(n  1).
void Set(int nIdx, POINT pt)
Sets a specified polygon vertex to a new value.
void Add(POINT
pt)
Adds a new vertex to the polygon.
void Del(int nIdx)
Deletes a specified polygon vertex. Argument nIdx is a zerobased
index of the polygon vertices.
void Clear()
Deletes all polygon vertices.
Validity Check
virtual bool IsValid() const
Checks the validity of the polygon vertices. Valid if there are more than
three vertices, and its member function Orientation() returns a
nonzero value.
Services
int Orientation() const
Orientation or order of the stored polygon vertices. Returns 1 for counterclockwise
direction, 1 for clockwise, and 0 for error (e.g., vertices along
a straight line).
double Area() const
Area of polygon.
const POSITION Find(POINT
pt) const
The position of a given point in the polygon.
const POINT Centroid() const
The center of the polygon.
const polygon Clip(const polygon &pg) const
Intersects a given polygon, and returns their overlap, if any.
const polygon Difference(const polygon &pg) const
Intersects a given polygon, and returns their difference, if any.
const polygon XOR(const polygon &pg) const
Intersects a given polygon, and returns their exclusiveOR overlap, if
any.
const polygon Union(const polygon &pg) const
Intersects a given polygon, and returns their union, if any.
