leaflet/src/layer/vector/Polyline.js

JavaScript library for mobile-friendly interactive maps

/*
 * L.Polyline implements polyline vector layer (a set of points connected with lines)
 */

L.Polyline = L.Path.extend({

	options: {
		// how much to simplify the polyline on each zoom level
		// more = better performance and smoother look, less = more accurate
		smoothFactor: 1.0
		// noClip: false
	},

	initialize: function (latlngs, options) {
		L.setOptions(this, options);
		this._setLatLngs(latlngs);
	},

	getLatLngs: function () {
		return this._latlngs;
	},

	setLatLngs: function (latlngs) {
		this._setLatLngs(latlngs);
		return this.redraw();
	},

	isEmpty: function () {
		return !this._latlngs.length;
	},

	closestLayerPoint: function (p) {
		var minDistance = Infinity,
		    minPoint = null,
		    closest = L.LineUtil._sqClosestPointOnSegment,
		    p1, p2;

		for (var j = 0, jLen = this._parts.length; j < jLen; j++) {
			var points = this._parts[j];

			for (var i = 1, len = points.length; i < len; i++) {
				p1 = points[i - 1];
				p2 = points[i];

				var sqDist = closest(p, p1, p2, true);

				if (sqDist < minDistance) {
					minDistance = sqDist;
					minPoint = closest(p, p1, p2);
				}
			}
		}
		if (minPoint) {
			minPoint.distance = Math.sqrt(minDistance);
		}
		return minPoint;
	},

	getCenter: function () {
		var i, halfDist, segDist, dist, p1, p2, ratio,
		    points = this._rings[0],
		    len = points.length;

		if (!len) { return null; }

		// polyline centroid algorithm; only uses the first ring if there are multiple

		for (i = 0, halfDist = 0; i < len - 1; i++) {
			halfDist += points[i].distanceTo(points[i + 1]) / 2;
		}

		// The line is so small in the current view that all points are on the same pixel.
		if (halfDist === 0) {
			return this._map.layerPointToLatLng(points[0]);
		}

		for (i = 0, dist = 0; i < len - 1; i++) {
			p1 = points[i];
			p2 = points[i + 1];
			segDist = p1.distanceTo(p2);
			dist += segDist;

			if (dist > halfDist) {
				ratio = (dist - halfDist) / segDist;
				return this._map.layerPointToLatLng([
					p2.x - ratio * (p2.x - p1.x),
					p2.y - ratio * (p2.y - p1.y)
				]);
			}
		}
	},

	getBounds: function () {
		return this._bounds;
	},

	addLatLng: function (latlng, latlngs) {
		latlngs = latlngs || this._defaultShape();
		latlng = L.latLng(latlng);
		latlngs.push(latlng);
		this._bounds.extend(latlng);
		return this.redraw();
	},

	_setLatLngs: function (latlngs) {
		this._bounds = new L.LatLngBounds();
		this._latlngs = this._convertLatLngs(latlngs);
	},

	_defaultShape: function () {
		return L.Polyline._flat(this._latlngs) ? this._latlngs : this._latlngs[0];
	},

	// recursively convert latlngs input into actual LatLng instances; calculate bounds along the way
	_convertLatLngs: function (latlngs) {
		var result = [],
		    flat = L.Polyline._flat(latlngs);

		for (var i = 0, len = latlngs.length; i < len; i++) {
			if (flat) {
				result[i] = L.latLng(latlngs[i]);
				this._bounds.extend(result[i]);
			} else {
				result[i] = this._convertLatLngs(latlngs[i]);
			}
		}

		return result;
	},

	_project: function () {
		this._rings = [];
		this._projectLatlngs(this._latlngs, this._rings);

		// project bounds as well to use later for Canvas hit detection/etc.
		var w = this._clickTolerance(),
		    p = new L.Point(w, -w);

		if (this._bounds.isValid()) {
			this._pxBounds = new L.Bounds(
				this._map.latLngToLayerPoint(this._bounds.getSouthWest())._subtract(p),
				this._map.latLngToLayerPoint(this._bounds.getNorthEast())._add(p));
		}
	},

	// recursively turns latlngs into a set of rings with projected coordinates
	_projectLatlngs: function (latlngs, result) {

		var flat = latlngs[0] instanceof L.LatLng,
		    len = latlngs.length,
		    i, ring;

		if (flat) {
			ring = [];
			for (i = 0; i < len; i++) {
				ring[i] = this._map.latLngToLayerPoint(latlngs[i]);
			}
			result.push(ring);
		} else {
			for (i = 0; i < len; i++) {
				this._projectLatlngs(latlngs[i], result);
			}
		}
	},

	// clip polyline by renderer bounds so that we have less to render for performance
	_clipPoints: function () {
		var bounds = this._renderer._bounds;

		this._parts = [];
		if (!this._pxBounds || !this._pxBounds.intersects(bounds)) {
			return;
		}

		if (this.options.noClip) {
			this._parts = this._rings;
			return;
		}

		var parts = this._parts,
		    i, j, k, len, len2, segment, points;

		for (i = 0, k = 0, len = this._rings.length; i < len; i++) {
			points = this._rings[i];

			for (j = 0, len2 = points.length; j < len2 - 1; j++) {
				segment = L.LineUtil.clipSegment(points[j], points[j + 1], bounds, j, true);

				if (!segment) { continue; }

				parts[k] = parts[k] || [];
				parts[k].push(segment[0]);

				// if segment goes out of screen, or it's the last one, it's the end of the line part
				if ((segment[1] !== points[j + 1]) || (j === len2 - 2)) {
					parts[k].push(segment[1]);
					k++;
				}
			}
		}
	},

	// simplify each clipped part of the polyline for performance
	_simplifyPoints: function () {
		var parts = this._parts,
		    tolerance = this.options.smoothFactor;

		for (var i = 0, len = parts.length; i < len; i++) {
			parts[i] = L.LineUtil.simplify(parts[i], tolerance);
		}
	},

	_update: function () {
		if (!this._map) { return; }

		this._clipPoints();
		this._simplifyPoints();
		this._updatePath();
	},

	_updatePath: function () {
		this._renderer._updatePoly(this);
	}
});

L.polyline = function (latlngs, options) {
	return new L.Polyline(latlngs, options);
};

L.Polyline._flat = function (latlngs) {
	// true if it's a flat array of latlngs; false if nested
	return !L.Util.isArray(latlngs[0]) || (typeof latlngs[0][0] !== 'object' && typeof latlngs[0][0] !== 'undefined');
};