title: How do you add an infowindow to a cluster marker?
body: <p>The documentation and stackoverflow tickets are very sparse in this area.</p>
  
  <p>I want to open an infowindow when a user mouseover's a cluster marker. I want this infowindow to be generated using two things, a piece of data from the clusters's markers, and a rails partial. </p>
  
  <p>How do I:</p>
  
  <ol>
  <li>add a mouseover listener to a cluster </li>
  <li>get the markers inside the cluster (select the right object) create an infowindow for this</li>
  <li>cluster based on a partial (using data from the above)</li>
  </ol>
  
  <p>I am using google maps for rail's gem and the Marker Clusterer Plus libary.</p>
  
  <p>I have the following in my builder:</p>
  
  <pre><code>handler = Gmaps.build("Google",
    { markers:
      { clusterer: {
          gridSize: 8,
          maxZoom: 12,
          zoomOnClick: true,
          styles: [ {
                textSize: 1,
                textColor: '#45A6DD',
                url: 'images/maps/cluster.marker.png',
                height: 51,
                width: 51 }
              ]
        }
      },
      builders: {
        Marker: KhMarker
      }
    });
  </code></pre>
  
  <p>And I have added the following script onto the page with the map. This listens for the 'clusterclick' event. I would like to use the MarkerClustererPlus mouseover event, but I can't figure out which js object I should pass into the addListener event.</p>
  
  <pre><code>    google.maps.event.addListener(handler.clusterer.getServiceObject(), 'clusterclick', function(cluster) {
        // console.log("Cluster clicked")
  
        var content = '';
  
        content = this;
        console.log (content)
  
        // Convert lat/long from cluster object to a usable MVCObject
        // var info = new google.maps.MVCObject;
        // info.set('position', cluster.center_);
  
        // var infowindow = new google.maps.InfoWindow();
        // infowindow.close();
        // infowindow.setContent();
  
        // infowindow.open(handler.map.getServiceObject(), info);
      });
  </code></pre>
  
  <p>In the console I am seeing the MarkerClusterer object, but what I am trying to get is the specific cluster I just moused over and the markers it contains. I need to grab the city name (or lat/long) of the first marker to then get the region it is from so I can pass this data to the infowindow.</p>
  
  <p>I can get a basic infowindow to open on click. I want to have the infowindow open from a partial similar to the way that my markers do.</p>
  
  <pre><code>  marker.infowindow render_to_string(partial: "/destinations/map_tile.html", locals: { city: city })
  </code></pre>
  
  <p>How do I do these 3 things?</p>