// Define the overlay, derived from google.maps.OverlayView
function Label(opt_options) {
    // Initialization
    this.setValues(opt_options);

    // Label specific
    var span = this.span_ = document.createElement('span');
    span.style.cssText = 'position: relative; left: -50%; top: -8px; ' +
                      'white-space: nowrap; border: 1px solid blue; ' +
                      'padding: 2px; background-color: white';

    var div = this.div_ = document.createElement('div');
    div.appendChild(span);
    div.style.cssText = 'position: absolute; display: none';
};
Label.prototype = new google.maps.OverlayView;

// Implement onAdd
Label.prototype.onAdd = function () {
    var pane = this.getPanes().overlayLayer;
    pane.appendChild(this.div_);

    // Ensures the label is redrawn if the text or position is changed.
    var me = this;
    this.listeners_ = [
   google.maps.event.addListener(this, 'position_changed',
       function () { me.draw(); }),
   google.maps.event.addListener(this, 'text_changed',
       function () { me.draw(); })
 ];
};

// Implement onRemove
Label.prototype.onRemove = function () {
    this.div_.parentNode.removeChild(this.div_);

    // Label is removed from the map, stop updating its position/text.
    for (var i = 0, I = this.listeners_.length; i < I; ++i) {
        google.maps.event.removeListener(this.listeners_[i]);
    }
};

// Implement draw
Label.prototype.draw = function () {
    var projection = this.getProjection();
    var position = projection.fromLatLngToDivPixel(this.get('position'));

    var div = this.div_;
    var y = position.y + 10;
    div.style.left = position.x + 'px';
    div.style.top = y + 'px';
    div.style.display = 'block';

    this.span_.innerHTML = this.get('text').toString();
};