Esri ClusterFeatureLayer

This is a slightly revised version of the Cluster Example provided here.

A couple of things I added:

Works off a URL instead of a data option, like a FeatureLayer.
Option to add a Font for the Clusters TextSymbol. Default is 10pt and Arial.
If a service of geometryType esriGeometryPolygon is provided, it will convert those geometries to points and cluster them.
A zoomOnClick option that will zoom the map 1 zoom level on the clicked cluster graphic.
Has a MODE_SNAPSHOT that will cache all features in the service for increased performance. Refresh the layer using updateClusters().
Has an outFields option for the Features returned.
Has an option to use the services default renderer for single features.
And more, check source for more options.

All options

url required - Will generate clusters based on Features returned from map service.
MODE_SNAPSHOT optional - Will download and cache all features in service to draw clusters much quicker. Takes a little longer to loader, but improves performance during continued usage. Use updateClusters() to refresh clusters with service. Default is true.
outFields optional - Defines what fields are returned with Features. Deafult is ['*'].
objectIdField optional - Defines the OBJECTID field of service. Default is 'OBJECTID'.
where optional - Where clause for query. Default is null.
useDefaultSymbol optional - Use the services default symbology for single features. Default is false. If clustering a polygon service, will always default to false.
returnLimit optional - Return limit of features returned from query. Default is 1000.
distance optional - The max number of pixels between points to group points in the same cluster. Default value is 50.
labelColor optional - Hex string or array of rgba values used as the color for cluster labels. Default value is #fff (white).
labelOffset optional - Number of pixels to shift a cluster label vertically. Defaults to -5 to align labels with circle symbols. Does not work in IE.
resolution required - Width of a pixel in map coordinates. Example of how to calculate: map.extent.getWidth() / map.width.
showSingles optional - Whether or graphics should be displayed when a cluster graphic is clicked. Default is true.
zoomOnClick optionl - Will zoom the map when a cluster graphic is clicked. Default is true.
singleSymbol optional - Symbol to use for graphics that represent single points. Default is a small gray SimpleMarkerSymbol.
singleRenderer optional - Can provide a renderer for single features to override the default renderer.
singleTemplate optional Popup template used to format attributes for graphics that represent single points. Default shows all attributes as 'attribute = value' (not recommended).
maxSingles optional Threshold for whether or not to show graphics for points in a cluster. Default is 1000.
font optional Font to use for TextSymbol. Default is 10pt, Arial.
spatialReferenc optional Spatial reference for all graphics in the layer. This has to match the spatial reference of the map. Default is 102100. Omit this if the map uses basemaps in web mercator.

Events

clusters-shown - fires when clusters have been drawn and shown on map. Fires after the map extent changes.
details-loaded - fires when the layer has downloaded the default renderer properties from the service.
cluster-click - will return all points that make up a cluster when a cluster is clicked.

Notes

Although this behaves similar to a FeatureLayer, it does not have all the optimizations of a FeatureLayer. There is no Vector Tiling for the points. ~~A possible optimization could be to break up the request by objectIds in to multiple queries.~~ I added the ability to send requests by objectIds in chunks of 1000 by default. Can be set in options. I also added a cache for clustered graphics and a clearCache() method.

Demo

A demo can be seen here. A demo using a service of polygons shown as clusters can be seen here.

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