MapLibre GL JS in React

Basic Map Component

// src/components/map/TacticalMap.tsx
'use client';

import { useEffect, useRef, useCallback } from 'react';
import maplibregl from 'maplibre-gl';
import 'maplibre-gl/dist/maplibre-gl.css';
import { useIncidentStore } from '@/stores/incidents';

const NYC_CENTER: [number, number] = [-73.98, 40.75];
const DEFAULT_ZOOM = 11;

export function TacticalMap() {
  const mapContainer = useRef<HTMLDivElement>(null);
  const map = useRef<maplibregl.Map | null>(null);
  const { incidents, selectIncident } = useIncidentStore();
  
  // Initialize map once
  useEffect(() => {
    if (!mapContainer.current || map.current) return;
    
    map.current = new maplibregl.Map({
      container: mapContainer.current,
      style: '/map-style-dark.json',
      center: NYC_CENTER,
      zoom: DEFAULT_ZOOM,
      maxZoom: 18,
      minZoom: 8,
    });
    
    map.current.on('load', () => {
      setupSources(map.current!);
      setupLayers(map.current!);
      setupEventHandlers(map.current!);
    });
    
    // Cleanup
    return () => {
      map.current?.remove();
      map.current = null;
    };
  }, []);
  
  // Update incidents when data changes
  useEffect(() => {
    if (!map.current?.isStyleLoaded()) return;
    
    const source = map.current.getSource('incidents') as maplibregl.GeoJSONSource;
    if (source) {
      source.setData(incidentsToGeoJSON(incidents));
    }
  }, [incidents]);
  
  return (
    <div 
      ref={mapContainer} 
      className="w-full h-full"
      style={{ background: '#0a0a0f' }}
    />
  );
}

GeoJSON Conversion

// src/lib/geo.ts
import type { Incident } from '@/types/incidents';

interface GeoJSONFeature {
  type: 'Feature';
  geometry: {
    type: 'Point';
    coordinates: [number, number];
  };
  properties: {
    id: string;
    title: string;
    category: string;
    severity: string;
    eventTime: string;
  };
}

export function incidentsToGeoJSON(incidents: Incident[]): GeoJSON.FeatureCollection {
  const features: GeoJSONFeature[] = incidents
    .filter(i => i.location)
    .map(incident => ({
      type: 'Feature',
      geometry: incident.location!,
      properties: {
        id: incident.id,
        title: incident.title,
        category: incident.category,
        severity: incident.severity,
        eventTime: incident.eventTime.toISOString(),
      },
    }));
  
  return {
    type: 'FeatureCollection',
    features,
  };
}

Source Setup with Clustering

function setupSources(map: maplibregl.Map) {
  map.addSource('incidents', {
    type: 'geojson',
    data: { type: 'FeatureCollection', features: [] },
    cluster: true,
    clusterMaxZoom: 14, // Cluster until zoom 14
    clusterRadius: 50, // Pixel radius for clustering
    clusterProperties: {
      // Aggregate severity counts per cluster
      critical: ['+', ['case', ['==', ['get', 'severity'], 'critical'], 1, 0]],
      high: ['+', ['case', ['==', ['get', 'severity'], 'high'], 1, 0]],
    },
  });
}

Layer Setup

// Severity color mapping
const SEVERITY_COLORS = {
  critical: '#ff2d55',
  high: '#ff6b35',
  moderate: '#ffb800',
  low: '#00d4ff',
  info: '#a1a1aa',
};

function setupLayers(map: maplibregl.Map) {
  // Cluster circles
  map.addLayer({
    id: 'clusters',
    type: 'circle',
    source: 'incidents',
    filter: ['has', 'point_count'],
    paint: {
      'circle-color': [
        'case',
        ['>', ['get', 'critical'], 0], SEVERITY_COLORS.critical,
        ['>', ['get', 'high'], 0], SEVERITY_COLORS.high,
        SEVERITY_COLORS.moderate,
      ],
      'circle-radius': [
        'step',
        ['get', 'point_count'],
        20,  // 20px for < 10
        10, 30, // 30px for 10-49
        50, 40, // 40px for 50+
      ],
      'circle-opacity': 0.8,
      'circle-stroke-width': 2,
      'circle-stroke-color': '#ffffff',
    },
  });
  
  // Cluster count labels
  map.addLayer({
    id: 'cluster-count',
    type: 'symbol',
    source: 'incidents',
    filter: ['has', 'point_count'],
    layout: {
      'text-field': '{point_count_abbreviated}',
      'text-font': ['Open Sans Bold'],
      'text-size': 14,
    },
    paint: {
      'text-color': '#ffffff',
    },
  });
  
  // Individual incident points
  map.addLayer({
    id: 'incidents-point',
    type: 'circle',
    source: 'incidents',
    filter: ['!', ['has', 'point_count']],
    paint: {
      'circle-color': [
        'match',
        ['get', 'severity'],
        'critical', SEVERITY_COLORS.critical,
        'high', SEVERITY_COLORS.high,
        'moderate', SEVERITY_COLORS.moderate,
        'low', SEVERITY_COLORS.low,
        SEVERITY_COLORS.info,
      ],
      'circle-radius': 8,
      'circle-stroke-width': 2,
      'circle-stroke-color': '#ffffff',
    },
  });
  
  // Pulsing animation for critical incidents
  map.addLayer({
    id: 'incidents-pulse',
    type: 'circle',
    source: 'incidents',
    filter: ['all', 
      ['!', ['has', 'point_count']],
      ['==', ['get', 'severity'], 'critical'],
    ],
    paint: {
      'circle-color': SEVERITY_COLORS.critical,
      'circle-radius': 16,
      'circle-opacity': 0.3,
    },
  });
}

Event Handlers

function setupEventHandlers(map: maplibregl.Map) {
  // Change cursor on hover
  map.on('mouseenter', 'incidents-point', () => {
    map.getCanvas().style.cursor = 'pointer';
  });
  
  map.on('mouseleave', 'incidents-point', () => {
    map.getCanvas().style.cursor = '';
  });
  
  // Click handler for incidents
  map.on('click', 'incidents-point', (e) => {
    if (!e.features?.length) return;
    
    const feature = e.features[0];
    const id = feature.properties?.id;
    
    if (id) {
      // Update store
      useIncidentStore.getState().selectIncident(id);
      
      // Center on incident
      const coords = (feature.geometry as GeoJSON.Point).coordinates as [number, number];
      map.flyTo({ center: coords, zoom: 15 });
    }
  });
  
  // Click handler for clusters
  map.on('click', 'clusters', async (e) => {
    const features = map.queryRenderedFeatures(e.point, { layers: ['clusters'] });
    if (!features.length) return;
    
    const clusterId = features[0].properties?.cluster_id;
    const source = map.getSource('incidents') as maplibregl.GeoJSONSource;
    
    const zoom = await source.getClusterExpansionZoom(clusterId);
    const coords = (features[0].geometry as GeoJSON.Point).coordinates as [number, number];
    
    map.flyTo({ center: coords, zoom });
  });
}

Popup Component

// src/components/map/IncidentPopup.tsx
'use client';

import { useEffect, useRef } from 'react';
import maplibregl from 'maplibre-gl';
import { createRoot } from 'react-dom/client';
import type { Incident } from '@/types/incidents';

interface Props {
  map: maplibregl.Map;
  incident: Incident;
  onClose: () => void;
}

export function IncidentPopup({ map, incident, onClose }: Props) {
  const popupRef = useRef<maplibregl.Popup | null>(null);
  
  useEffect(() => {
    if (!incident.location) return;
    
    const container = document.createElement('div');
    const root = createRoot(container);
    
    root.render(
      <div className="p-3 min-w-[200px]">
        <div className="flex items-center gap-2 mb-2">
          <span className={`w-2 h-2 rounded-full bg-severity-${incident.severity}`} />
          <span className="text-xs uppercase text-text-secondary">
            {incident.category}
          </span>
        </div>
        <h3 className="font-medium text-sm mb-1">{incident.title}</h3>
        {incident.locationText && (
          <p className="text-xs text-text-secondary">{incident.locationText}</p>
        )}
        <p className="text-xs text-text-muted mt-2">
          {new Date(incident.eventTime).toLocaleTimeString()}
        </p>
      </div>
    );
    
    popupRef.current = new maplibregl.Popup({
      closeButton: true,
      closeOnClick: false,
      className: 'incident-popup',
    })
      .setLngLat(incident.location.coordinates as [number, number])
      .setDOMContent(container)
      .addTo(map);
    
    popupRef.current.on('close', onClose);
    
    return () => {
      root.unmount();
      popupRef.current?.remove();
    };
  }, [map, incident, onClose]);
  
  return null;
}

Popup Styles

/* src/app/globals.css */
.incident-popup .maplibregl-popup-content {
  background: var(--bg-secondary);
  border: 1px solid var(--bg-tertiary);
  border-radius: 8px;
  padding: 0;
  color: var(--text-primary);
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.5);
}

.incident-popup .maplibregl-popup-tip {
  border-top-color: var(--bg-secondary);
}

.incident-popup .maplibregl-popup-close-button {
  color: var(--text-secondary);
  font-size: 18px;
  padding: 4px 8px;
}

Dark Tactical Map Style

// public/map-style-dark.json
{
  "version": 8,
  "name": "Tactical Dark",
  "sources": {
    "protomaps": {
      "type": "vector",
      "url": "pmtiles:///tiles/nyc.pmtiles"
    }
  },
  "layers": [
    {
      "id": "background",
      "type": "background",
      "paint": { "background-color": "#0a0a0f" }
    },
    {
      "id": "water",
      "type": "fill",
      "source": "protomaps",
      "source-layer": "water",
      "paint": { "fill-color": "#12121a" }
    },
    {
      "id": "roads",
      "type": "line",
      "source": "protomaps",
      "source-layer": "roads",
      "paint": {
        "line-color": "#1a1a24",
        "line-width": 1
      }
    },
    {
      "id": "buildings",
      "type": "fill",
      "source": "protomaps",
      "source-layer": "buildings",
      "paint": {
        "fill-color": "#15151f",
        "fill-opacity": 0.5
      }
    }
  ]
}

Fit Bounds to Incidents

function fitToIncidents(map: maplibregl.Map, incidents: Incident[]) {
  const validIncidents = incidents.filter(i => i.location);
  if (validIncidents.length === 0) return;
  
  const bounds = new maplibregl.LngLatBounds();
  
  validIncidents.forEach(incident => {
    bounds.extend(incident.location!.coordinates as [number, number]);
  });
  
  map.fitBounds(bounds, {
    padding: 50,
    maxZoom: 15,
    duration: 1000,
  });
}

Animate to Location

function flyToIncident(map: maplibregl.Map, incident: Incident) {
  if (!incident.location) return;
  
  map.flyTo({
    center: incident.location.coordinates as [number, number],
    zoom: 16,
    duration: 1500,
    essential: true,
  });
}

Get Visible Bounds

function getVisibleBbox(map: maplibregl.Map): [number, number, number, number] {
  const bounds = map.getBounds();
  return [
    bounds.getWest(),  // sw_lng
    bounds.getSouth(), // sw_lat
    bounds.getEast(),  // ne_lng
    bounds.getNorth(), // ne_lat
  ];
}

Performance Tips

1. Use clustering — essential for 1000+ points
2. Debounce updates — don't update source on every state change
3. Limit features — query with viewport bounds
4. Use WebGL layers — avoid HTML markers for many points
5. Simplify geometries — reduce polygon complexity server-side