h3_core 1.0.3

Dart/Flutter bindings for the H3 geospatial indexing library. Uses dart:ffi on native platforms, h3-js on web.

h3_core

Dart/Flutter bindings for the H3 geospatial indexing library.

Wraps H3 v4.4.1 via dart:ffi on native platforms and h3-js via dart:js_interop on web. Same API on all platforms.

Features

• Full H3 v4.4.1 API (~80 functions)
• Native: zero-overhead FFI calls via Build Hooks (compiles C natively — no pre-built binaries)
• Web: h3-js interop via dart:js_interop
• Single package, identical API on all platforms
• Type-safe Dart API with extension types (H3Index, LatLng, CellBoundary)
• Async wrappers for heavy operations

Platform Support

Platform	Backend	CI Tested
Android	dart:ffi (C)	via macOS build
iOS	dart:ffi (C)	via macOS build
macOS	dart:ffi (C)	macOS stable
Linux	dart:ffi (C)	Ubuntu stable + beta
Windows	dart:ffi (C)	Windows stable
Web	h3-js (JS)	Chrome stable

Installation

dependencies:
  h3_core: ^1.0.3

Quick Start

import 'package:h3_core/h3_core.dart';

// Convert coordinates to H3 cell
final cell = latLngToCell(LatLng(37.7749, -122.4194), 9);
print(cell.toHex()); // 89283082803ffff

// Get cell center
final center = cellToLatLng(cell);
print('${center.lat}, ${center.lng}');

// Get neighbors
final neighbors = gridDisk(cell, 1); // 7 cells (origin + 6 neighbors)

// Check cell properties
print(getResolution(cell)); // 9
print(isValidCell(cell));   // true
print(isPentagon(cell));    // false

API Overview

Indexing

• latLngToCell — Convert coordinates to H3 cell
• cellToLatLng — Get cell center point
• cellToBoundary — Get cell boundary vertices

Inspection

• getResolution, getBaseCellNumber, isValidCell, isPentagon, isResClassIII
• getIcosahedronFaces, isValidIndex, isValidDirectedEdge, isValidVertex

Traversal

• gridDisk, gridDiskDistances — Get cells within k distance
• gridRing — Get hollow ring at distance k
• gridDistance — Distance between two cells
• gridPathCells — Line of cells between two cells

Hierarchy

• cellToParent, cellToChildren, cellToCenterChild
• cellToChildPos, childPosToCell
• compactCells, uncompactCells

Directed Edges

• areNeighborCells, cellsToDirectedEdge
• getDirectedEdgeOrigin, getDirectedEdgeDestination
• originToDirectedEdges, directedEdgeToBoundary

Vertices

• cellToVertex, cellToVertexes, vertexToLatLng

Measurements

• greatCircleDistanceKm, greatCircleDistanceM
• cellAreaKm2, cellAreaM2
• edgeLengthKm, edgeLengthM
• getHexagonAreaAvgKm2, getHexagonEdgeLengthAvgKm
• getNumCells

Regions

• polygonToCells — Fill polygon with cells
• cellsToMultiPolygon — Convert cells to polygon boundaries

Coordinates

• cellToLocalIj, localIjToCell

Async

• polygonToCellsAsync, gridDiskAsync, compactCellsAsync, uncompactCellsAsync

Web Setup

Add the h3-js script tag to your web/index.html before the Flutter bootstrap:

<script src="https://cdn.jsdelivr.net/npm/h3-js@4/dist/h3-js.umd.js"></script>
<script src="flutter_bootstrap.js" async></script>

Versioning

Package version uses its own semver. Wraps H3 C library v4.4.1.

License

Apache 2.0 (matching H3)