src/plugins/leaflet-draw/draw/handler/Draw.Polygon.js

/**
 * @class L.Draw.Polygon
 * @aka Draw.Polygon
 * @inherits L.Draw.Polyline
 */
L.Draw.Polygon = L.Draw.Polyline.extend({
	statics: {
		TYPE: 'polygon'
	},

	Poly: L.Polygon,

	options: {
		showArea: false,
		shapeOptions: {
			stroke: true,
			color: '#3388ff',
			weight: 4,
			opacity: 0.5,
			fill: true,
			fillColor: null, //same as color by default
			fillOpacity: 0.2,
			clickable: true
		},
		metric: true // Whether to use the metric measurement system or imperial
	},

	// @method initialize(): void
	initialize: function (map, options) {
		L.Draw.Polyline.prototype.initialize.call(this, map, options);

		// Save the type so super can fire, need to do this as cannot do this.TYPE :(
		this.type = L.Draw.Polygon.TYPE;
	},

	_updateFinishHandler: function () {
		var markerCount = this._markers.length;

		// The first marker should have a click handler to close the polygon
		if (markerCount === 1) {
			this._markers[0].on('click', this._finishShape, this);
		}

		// Add and update the double click handler
		if (markerCount > 2) {
			this._markers[markerCount - 1].on('dblclick', this._finishShape, this);
			// Only need to remove handler if has been added before
			if (markerCount > 3) {
				this._markers[markerCount - 2].off('dblclick', this._finishShape, this);
			}
		}
	},

	_getTooltipText: function () {
		var text, subtext;

		if (this._markers.length === 0) {
			text = L.drawLocal.draw.handlers.polygon.tooltip.start;
		} else if (this._markers.length < 3) {
			text = L.drawLocal.draw.handlers.polygon.tooltip.cont;
		} else {
			text = L.drawLocal.draw.handlers.polygon.tooltip.end;
			subtext = this._getMeasurementString();
		}

		return {
			text: text,
			subtext: subtext
		};
	},

	_getMeasurementString: function () {
		var area = this._area;

		if (!area) {
			return null;
		}

		return L.GeometryUtil.readableArea(area, this.options.metric);
	},

	_shapeIsValid: function () {
		return this._markers.length >= 3;
	},

	_vertexChanged: function (latlng, added) {
		var latLngs;

		// Check to see if we should show the area
		if (!this.options.allowIntersection && this.options.showArea) {
			latLngs = this._poly.getLatLngs();

			this._area = L.GeometryUtil.geodesicArea(latLngs);
		}

		L.Draw.Polyline.prototype._vertexChanged.call(this, latlng, added);
	},

	_cleanUpShape: function () {
		var markerCount = this._markers.length;

		if (markerCount > 0) {
			this._markers[0].off('click', this._finishShape, this);

			if (markerCount > 2) {
				this._markers[markerCount - 1].off('dblclick', this._finishShape, this);
			}
		}
	}
});