Struct Polygon2View

Non-owning read-only view of an ordered sequence of polygon rings.

struct Polygon2View(T)
  
if (isGeoScalar!T);

Supported scalar types are int, long, float, double, and real.

Polygon2View.init is an empty polygon view.

Polygon2View does not allocate or copy ring descriptors or point data. The caller retains ownership of both the backing ring-descriptor storage and the point storage referenced by those descriptors. The ring-descriptor storage must remain valid for the lifetime of the Polygon2View. Point storage referenced by a stored ring descriptor must remain valid for as long as that descriptor can be accessed through the Polygon2View.

The view aliases this backing storage. Changes made through the owners of mutable ring-descriptor or point storage remain visible through an existing Polygon2View. Mutation is not exposed through Polygon2View itself.

For a non-empty polygon, ring zero is the exterior ring. Subsequent rings are interior rings. Ring roles are structural and do not depend on winding direction.

Polygon2View does not validate topology or normalize ring orientation. Empty and degenerate rings remain representable through LinearRing2View.

Constructors

NameDescription
this (rings) Constructs a view over contiguous ring-descriptor storage.

Properties

NameTypeDescription
empty[get] boolTrue when the polygon contains no rings.
exterior[get] const(LinearRing2View!T)Returns the exterior ring by value.
holeCount[get] size_tNumber of interior rings.
length[get] size_tNumber of rings, including the exterior ring when present.

Methods

NameDescription
hole (index) Returns one interior ring by zero-based hole index.
opIndex (index) Returns one ring descriptor by value.

Example

Example using structural exterior and hole ring roles. 

import geo;

alias P = Point2!double;
alias R = LinearRing2View!double;
alias G = Polygon2View!double;

P[4] exteriorPoints = [
    P(0.0, 0.0),
    P(10.0, 0.0),
    P(10.0, 10.0),
    P(0.0, 10.0)
];

P[4] holePoints = [
    P(2.0, 2.0),
    P(4.0, 2.0),
    P(4.0, 4.0),
    P(2.0, 4.0)
];

R[2] rings = [
    R(exteriorPoints[]),
    R(holePoints[])
];

auto polygon =
    G(rings[]);

assert(!polygon.empty);
assert(polygon.length == 2);
assert(polygon.holeCount == 1);

assert(
    polygon[0][0] ==
    P(0.0, 0.0)
);

assert(
    polygon.exterior[2] ==
    P(10.0, 10.0)
);

assert(
    polygon.hole(0)[1] ==
    P(4.0, 2.0)
);