From 72141bac52e3548cdc638f10b549680ccc6cf3ef Mon Sep 17 00:00:00 2001
From: Zsolt Ero <zsolt.ero@gmail.com>
Date: Fri, 11 Oct 2024 01:13:47 +0300
Subject: [PATCH] feat(cluster.html): add example HTML file to demonstrate
 clustering with MapLibre GL JS for visualizing earthquake data

---
 website/src/examples/cluster.html | 149 ++++++++++++++++++++++++++++++
 1 file changed, 149 insertions(+)
 create mode 100644 website/src/examples/cluster.html
diff --git a/website/src/examples/cluster.html b/website/src/examples/cluster.html
new file mode 100644
index 0000000..e2ec29c
--- /dev/null
+++ b/website/src/examples/cluster.html
@@ -0,0 +1,149 @@
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <title>Create and style clusters</title>
+    <meta property="og:description" content="Use MapLibre GL JS' built-in functions to visualize points as clusters." />
+    <meta charset='utf-8'>
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <link rel='stylesheet' href='https://unpkg.com/maplibre-gl@4/dist/maplibre-gl.css' />
+    <script src='https://unpkg.com/maplibre-gl@4/dist/maplibre-gl.js'></script>
+    <style>
+        body { margin: 0; padding: 0; }
+        html, body, #map { height: 100%; }
+    </style>
+</head>
+<body>
+<div id="map"></div>
+
+<script>
+    const map = new maplibregl.Map({
+        container: 'map',
+        style: 'https://tiles.openfreemap.org/styles/positron',
+        center: [-103.59179687498357, 40.66995747013945],
+        zoom: 3
+    });
+
+    map.on('load', () => {
+        // Add a new source from our GeoJSON data and
+        // set the 'cluster' option to true. GL-JS will
+        // add the point_count property to your source data.
+        map.addSource('earthquakes', {
+            type: 'geojson',
+            // Point to GeoJSON data. This example visualizes all M1.0+ earthquakes
+            // from 12/22/15 to 1/21/16 as logged by USGS' Earthquake hazards program.
+            data: 'https://maplibre.org/maplibre-gl-js/docs/assets/earthquakes.geojson',
+            cluster: true,
+            clusterMaxZoom: 14, // Max zoom to cluster points on
+            clusterRadius: 50 // Radius of each cluster when clustering points (defaults to 50)
+        });
+
+        map.addLayer({
+            id: 'clusters',
+            type: 'circle',
+            source: 'earthquakes',
+            filter: ['has', 'point_count'],
+            paint: {
+                // Use step expressions (https://maplibre.org/maplibre-style-spec/#expressions-step)
+                // with three steps to implement three types of circles:
+                //   * Blue, 20px circles when point count is less than 100
+                //   * Yellow, 30px circles when point count is between 100 and 750
+                //   * Pink, 40px circles when point count is greater than or equal to 750
+                'circle-color': [
+                    'step',
+                    ['get', 'point_count'],
+                    '#51bbd6',
+                    100,
+                    '#f1f075',
+                    750,
+                    '#f28cb1'
+                ],
+                'circle-radius': [
+                    'step',
+                    ['get', 'point_count'],
+                    20,
+                    100,
+                    30,
+                    750,
+                    40
+                ]
+            }
+        });
+
+        map.addLayer({
+            id: 'cluster-count',
+            type: 'symbol',
+            source: 'earthquakes',
+            filter: ['has', 'point_count'],
+            layout: {
+                'text-field': '{point_count_abbreviated}',
+                'text-font': ['Noto Sans Regular'],
+                'text-size': 12
+            }
+        });
+
+        map.addLayer({
+            id: 'unclustered-point',
+            type: 'circle',
+            source: 'earthquakes',
+            filter: ['!', ['has', 'point_count']],
+            paint: {
+                'circle-color': '#11b4da',
+                'circle-radius': 4,
+                'circle-stroke-width': 1,
+                'circle-stroke-color': '#fff'
+            }
+        });
+
+        // inspect a cluster on click
+        map.on('click', 'clusters', async (e) => {
+            const features = map.queryRenderedFeatures(e.point, {
+                layers: ['clusters']
+            });
+            const clusterId = features[0].properties.cluster_id;
+            const zoom = await map.getSource('earthquakes').getClusterExpansionZoom(clusterId);
+            map.easeTo({
+                center: features[0].geometry.coordinates,
+                zoom
+            });
+        });
+
+        // When a click event occurs on a feature in
+        // the unclustered-point layer, open a popup at
+        // the location of the feature, with
+        // description HTML from its properties.
+        map.on('click', 'unclustered-point', (e) => {
+            const coordinates = e.features[0].geometry.coordinates.slice();
+            const mag = e.features[0].properties.mag;
+            let tsunami;
+
+            if (e.features[0].properties.tsunami === 1) {
+                tsunami = 'yes';
+            } else {
+                tsunami = 'no';
+            }
+
+            // Ensure that if the map is zoomed out such that
+            // multiple copies of the feature are visible, the
+            // popup appears over the copy being pointed to.
+            while (Math.abs(e.lngLat.lng - coordinates[0]) > 180) {
+                coordinates[0] += e.lngLat.lng > coordinates[0] ? 360 : -360;
+            }
+
+            new maplibregl.Popup()
+                .setLngLat(coordinates)
+                .setHTML(
+                    `magnitude: ${mag}<br>Was there a tsunami?: ${tsunami}`
+                )
+                .addTo(map);
+        });
+
+        map.on('mouseenter', 'clusters', () => {
+            map.getCanvas().style.cursor = 'pointer';
+        });
+        map.on('mouseleave', 'clusters', () => {
+            map.getCanvas().style.cursor = '';
+        });
+    });
+</script>
+</body>
+</html>
