[#362,view/map][s]: disable auto-turn on of map clustering above a certain number of points - fixes #362.

docs/tutorial-maps.markdown

@@ -102,3 +102,30 @@ view.featureparse = function (e) {
 };
 {% endhighlight %}
 
+
+### Turning on clustering
+
+You can turn on clustering of markers by setting the cluster option:
+
+    var map = new recline.View.Map({
+      model: dataset
+      state: {
+        cluster: true;
+      }
+    });
+
+You could also enable marker clustering only if you have more than a
+certain number of markers. Here's an example:
+
+    // var map is recline.View.Map instance
+    // marker cluster threshold
+    var threshold = 65;
+      
+    // enable clustering if there is a large number of markers
+    var countAfter = 0;
+    map.features.eachLayer(function(){countAfter++;});
+    if (countAfter > threshold) {
+      // note the map will auto-redraw when you change state!
+      map.state.set({cluster: true});
+    }
+

src/view.map.js

@@ -28,6 +28,8 @@ this.recline.View = this.recline.View || {};
 //     latField: {id of field containing latitude in the dataset}
 //     autoZoom: true,
 //     // use cluster support
+//     // cluster: true = always on
+//     // cluster: false = always off
 //     cluster: false
 //   }
 // </pre>
@@ -217,15 +219,6 @@ my.Map = Backbone.View.extend({
         this._remove(doc);
       }
 
-      // enable clustering if there is a large number of markers
-      var countAfter = 0;
-      this.features.eachLayer(function(){countAfter++;});
-      var sizeIncreased = countAfter - countBefore > 0;
-      if (!this.state.get('cluster') && countAfter > 64 && sizeIncreased) {
-        this.state.set({cluster: true});
-        return;
-      }
-
       // this must come before zooming!
       // if not: errors when using e.g. circle markers like
       // "Cannot call method 'project' of undefined"

test/view.map.test.js

@@ -130,7 +130,7 @@ test('_getGeometryFromRecord non-GeoJSON', function () {
   });
 });
 
-test('many markers', function () {
+test('many markers and clustering', function () {
   var data = [];
   for (var i = 0; i<1000; i++) {
     data.push({ id: i, lon: 13+3*i, lat: 52+i/10});
@@ -150,7 +150,13 @@ test('many markers', function () {
 
   dataset.query();
 
+  // this whole test looks a bit odd now
+  // we used to turn on clustering automatically at a certain level but we do not any more
+  equal(view.state.get('cluster'), false);
+
+  view.state.set({cluster: true});
   equal(view.state.get('cluster'), true);
+
   view.remove();
 });