L.LabelTextCollision = L.Canvas
        .extend({

            options : {
                /**
                 * Collision detection
                 */
                collisionFlg : true
            },

            initialize : function(options) {
                options = L.Util.setOptions(this, options);
            },

            _handleMouseHover : function(e, point) {
                var id, layer;

                for (id in this._drawnLayers) {
                    layer = this._drawnLayers[id];
                    if (layer.options.interactive
                            && layer._containsPoint(point)) {
                        L.DomUtil.addClass(this._containerText,
                                'leaflet-interactive'); // change cursor
                        this._fireEvent([ layer ], e, 'mouseover');
                        this._hoveredLayer = layer;
                    }
                }

                if (this._hoveredLayer) {
                    this._fireEvent([ this._hoveredLayer ], e);
                }
            },

            _handleMouseOut : function(e, point) {
                var layer = this._hoveredLayer;
                if (layer
                        && (e.type === 'mouseout' || !layer
                                ._containsPoint(point))) {
                    // if we're leaving the layer, fire mouseout
                    L.DomUtil.removeClass(this._containerText,
                            'leaflet-interactive');
                    this._fireEvent([ layer ], e, 'mouseout');
                    this._hoveredLayer = null;
                }
            },

            _updateTransform : function(center, zoom) {

                L.Canvas.prototype._updateTransform.call(this, center, zoom);

                var scale = this._map.getZoomScale(zoom, this._zoom), position = L.DomUtil
                        .getPosition(this._container), viewHalf = this._map
                        .getSize().multiplyBy(0.5 + this.options.padding), currentCenterPoint = this._map
                        .project(this._center, zoom), destCenterPoint = this._map
                        .project(center, zoom), centerOffset = destCenterPoint
                        .subtract(currentCenterPoint),

                topLeftOffset = viewHalf.multiplyBy(-scale).add(position).add(
                        viewHalf).subtract(centerOffset);

                if (L.Browser.any3d) {
                    L.DomUtil.setTransform(this._containerText, topLeftOffset,
                            scale);
                } else {
                    L.DomUtil.setPosition(this._containerText, topLeftOffset);
                }
            },
            _initContainer : function(options) {
                L.Canvas.prototype._initContainer.call(this);

                this._containerText = document.createElement('canvas');

                L.DomEvent.on(this._containerText, 'mousemove',
                        L.Util.throttle(this._onMouseMove, 32, this), this).on(
                        this._containerText,
                        'click dblclick mousedown mouseup contextmenu',
                        this._onClick, this).on(this._containerText,
                        'mouseout', this._handleMouseOut, this);

                this._ctxLabel = this._containerText.getContext('2d');

                L.DomUtil
                        .addClass(this._containerText, 'leaflet-zoom-animated');
                this.getPane().appendChild(this._containerText);

            },

            _update : function() {
                // textList
                this._textList = [];

                L.Renderer.prototype._update.call(this);
                var b = this._bounds, container = this._containerText, size = b
                        .getSize(), m = L.Browser.retina ? 2 : 1;

                L.DomUtil.setPosition(container, b.min);

                // set canvas size (also clearing it); use double size on retina
                container.width = m * size.x;
                container.height = m * size.y;
                container.style.width = size.x + 'px';
                container.style.height = size.y + 'px';

                // display text on the whole surface
                container.style.zIndex = '4';
                this._container.style.zIndex = '3';

                if (L.Browser.retina) {
                    this._ctxLabel.scale(2, 2);
                }

                // translate so we use the same path coordinates after canvas
                // element moves
                this._ctxLabel.translate(-b.min.x, -b.min.y);
                L.Canvas.prototype._update.call(this);

            },

            _updatePoly : function(layer, closed) {
                L.Canvas.prototype._updatePoly.call(this, layer, closed);
                this._text(this._ctxLabel, layer);
            },

            _updateCircle : function(layer) {
                L.Canvas.prototype._updateCircle.call(this, layer);
                this._text(this._ctxLabel, layer);
            },

            _text : function(ctx, layer) {

                if (layer.options.text != undefined) {

                    ctx.globalAlpha = 1;

                    var p = layer._point;
                    var textPoint;

                    if (p == undefined) {
                        // polygon or polyline
                        if (layer._parts.length == 0
                                || layer._parts[0].length == 0) {
                            return;
                        }
                        p = this._getCenter(layer._parts[0]);
                    }

                    // label bounds offset
                    var offsetX = 0;
                    var offsetY = 0;

                    /**
                     * TODO setting for custom font
                     */
                    ctx.lineWidth = 4.0;
                    ctx.font = "16px 'Meiryo'";

                    // Collision detection
                    var textWidth = (ctx.measureText(layer.options.text).width)
                            + p.x;// + offsetX;

                    var textHeight = p.y + offsetY + 20;

                    var bounds = L.bounds(
                            L.point(p.x + offsetX, p.y + offsetY), L.point(
                                    textWidth, textHeight));

                    if (this.options.collisionFlg) {

                        for ( var index in this._textList) {
                            var pointBounds = this._textList[index];
                            if (pointBounds.intersects(bounds)) {
                                return;
                            }
                        }
                    }

                    this._textList.push(bounds);

                    ctx.strokeStyle = "white";
                    ctx.strokeText(layer.options.text, p.x + offsetX, p.y
                            + offsetY);

                    if (layer.options.textColor == undefined) {
                        ctx.fillStyle = "blue";
                    } else {
                        ctx.fillStyle = layer.options.textColor;
                    }

                    ctx.fillText(layer.options.text, p.x + offsetX, p.y
                            + offsetY);
                }
            },

            _getCenter : function(points) {

                var i, halfDist, segDist, dist, p1, p2, ratio, 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 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;
                        var resutl = [ p2.x - ratio * (p2.x - p1.x),
                                p2.y - ratio * (p2.y - p1.y) ];

                        return L.point(resutl[0], resutl[1]);
                    }
                }
            },

        });