dcd05d13ce
git-svn-id: http://svn.openlayers.org/tags/openlayers/release-2.4-rc5@3182 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
126 lines
4.8 KiB
JavaScript
126 lines
4.8 KiB
JavaScript
/* Copyright (c) 2006 MetaCarta, Inc., published under the BSD license.
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* See http://svn.openlayers.org/trunk/openlayers/release-license.txt
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* for the full text of the license. */
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/**
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* @class
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*
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* A Linear Ring is a special LineString which is closed. It closes itself
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* automatically on every addPoint/removePoint by adding a copy of the first
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* point as the last point.
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*
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* Also, as it is the first in the line family to close itself, a getArea()
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* function is defined to calculate the enclosed area of the linearRing
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*
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* @requires OpenLayers/Geometry/LineString.js
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*/
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OpenLayers.Geometry.LinearRing = OpenLayers.Class.create();
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OpenLayers.Geometry.LinearRing.prototype =
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OpenLayers.Class.inherit(OpenLayers.Geometry.LineString, {
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/**
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* An array of class names representing the types of components that
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* the collection can include. A null value means the component types
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* are not restricted.
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* @type Array(String)
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*/
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componentTypes: ["OpenLayers.Geometry.Point"],
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/**
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* Linear rings are constructed with an array of points. This array
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* can represent a closed or open ring. If the ring is open (the last
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* point does not equal the first point), the constructor will close
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* the ring. If the ring is already closed (the last point does equal
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* the first point), it will be left closed.
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*
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* @constructor
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* @param {Array(OpenLayers.Geometry.Point)} points
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*/
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initialize: function(points) {
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OpenLayers.Geometry.LineString.prototype.initialize.apply(this,
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arguments);
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},
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/**
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* Adds a point to geometry components. If the point is to be added to
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* the end of the components array and it is the same as the last point
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* already in that array, the duplicate point is not added. This has the
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* effect of closing the ring if it is not already closed, and doing the
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* right thing if it is already closed. This behavior can be overridden
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* by calling the method with a non-null index as the second argument.
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*
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* @param {OpenLayers.Geometry.Point} point
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* @param {int} index Index into the array to insert the component
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* @type Boolean
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* @return Point was successfully added
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*/
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addComponent: function(point, index) {
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var added = false;
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//remove last point
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var lastPoint = this.components[this.components.length-1];
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OpenLayers.Geometry.Collection.prototype.removeComponent.apply(this,
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[lastPoint]);
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// given an index, add the point
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// without an index only add non-duplicate points
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if(index != null || !point.equals(lastPoint)) {
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added = OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
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arguments);
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}
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//append copy of first point
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var firstPoint = this.components[0];
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OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
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[firstPoint.clone()]);
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return added;
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},
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/**
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* Removes a point from geometry components
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*
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* @param {OpenLayers.Geometry.Point} point
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*/
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removeComponent: function(point) {
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if (this.components.length > 4) {
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//remove last point
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var lastPoint = this.components[this.components.length-1];
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OpenLayers.Geometry.Collection.prototype.removeComponent.apply(this,
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[lastPoint]);
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//remove our point
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OpenLayers.Geometry.Collection.prototype.removeComponent.apply(this,
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arguments);
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//append copy of first point
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var firstPoint = this.components[0];
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OpenLayers.Geometry.Collection.prototype.addComponent.apply(this,
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[firstPoint.clone()]);
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}
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},
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/** Note: The area is positive if the ring is oriented CW, otherwise
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* it will be negative.
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*
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* @returns The signed area for a ring.
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* @type float
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*/
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getArea: function() {
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var area = 0.0;
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if ( this.components && (this.components.length > 2)) {
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var sum = 0.0;
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for (var i = 0; i < this.components.length - 1; i++) {
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var b = this.components[i];
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var c = this.components[i+1];
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sum += (b.x + c.x) * (c.y - b.y);
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}
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area = - sum / 2.0;
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}
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return area;
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},
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/** @final @type String */
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CLASS_NAME: "OpenLayers.Geometry.LinearRing"
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});
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