GeoJSON features, given inline or fetched from a URL.

<HoloMap.Source.GeoJSON id="parcels" data={@feature_collection} />
<HoloMap.Source.GeoJSON id="stops" data="/api/stops.geojson" cluster cluster_radius={60} />

This is the source to reach for when the data comes from your own application. data is a plain Elixir map. Build it in a command, put it in state, and the map follows:

def command(:load_parcels, params, server) do
  put_action(server, :parcels_loaded, parcels: Repo.geojson(params.bbox))
end

def action(:parcels_loaded, params, component) do
  put_state(component, :parcels, params.parcels)
end

Changing data is the one source update that costs nothing structurally. MapLibre's setData swaps the features in place, leaving every layer built on top of it untouched.

Props

Clustering

Clustered sources emit two kinds of feature, and they usually want two layers: one for clusters, one for the leftover single points.

<HoloMap.Source.GeoJSON id="stops" data={@stops} cluster cluster_radius={60} />

<HoloMap.Layer.Circle
  id="clusters"
  source="stops"
  filter={["has", "point_count"]}
  paint={%{circle_color: "#51bbd6", circle_radius: 18}}
/>

<HoloMap.Layer.Circle
  id="unclustered"
  source="stops"
  filter={["!", ["has", "point_count"]]}
  paint={%{circle_color: "#11b4da", circle_radius: 6}}
/>

Feature state

HoloMap.API.set_feature_state/3 needs every feature to have an id. GeoJSON features often do not carry one, so set generate_id or point promote_id at a property that is already unique.