h3_flutter 0.1.0

Bindings to H3 library

H3 FLUTTER

H3 version: 3.7.2

The package allows to use H3 library directly in your Flutter application

The package uses C version under the hood. Works via FFI, bindings are automatically generated using ffigen

Few functions were adopted to allow work with them in a "safe" mode:

// Get hexagons in specified triangle.
final hexagons = h3.polyfill(
  resolution: 5,
  coordinates: [
    GeoCoord(20.4522, 54.7104),
    GeoCoord(37.6173, 55.7558),
    GeoCoord(39.7015, 47.2357),
  ],
);

But most of them are not. You still can use them, but it's more complicated, because you'll need to work directly with FFI (calloc, malloc and everything). If you want to try, you can use h3c singletone.

The package also contains few methods from JS library Geojson2H3.

Setup

Just add the package to pubspec.yaml and that's all.

---

How to update the package to match latest H3 version

~Good luck~

You need cmake tool, if you're on macos use next command:

brew install cmake # install cmake

Clone h3 repository and prepare everything:

git clone https://github.com/uber/h3 tmp/h3_sources 
# git checkout ... - checkout on commit you need, currently stable versions are in stable-3.x branch
mkdir tmp/h3_sources/build
cd tmp/h3_sources/build

Generate h3api.h file and copy it to the ios folder (we use ios folder for both OS - Android and iOS):

cmake ..
rm -rf ../../../ios/Classes/h3lib // recreate the folder to remove old h3 files
mkdir ../../../ios/Classes/h3lib

cp src/h3lib/include/h3api.h ../../../ios/Classes/h3lib

Copy other source files (*.h and *.c) to the folder.

cd ..
tmp/h3_sources/src/h3lib/include
cp src/h3lib/include/* ../../ios/Classes/h3lib
cp src/h3lib/lib/* ../../ios/Classes/h3lib

You need to add .h and .c files to the project using XCode if you want to launch example (iOS).
Then, probably you will face some build errors, in my case i just followed xcode instructions to solve them.

Code generation tool called ffigen is used to create C-to-Dart bindings.
To run it, you need to install LLVM:

brew install llvm

If you're using M1 Mac, as of now, you need to install x86 version of LLVM, to do it you need to install x86 version of Homebrew.

All H3 public functions should be specified in ffigen.yaml file Run flutter pub run ffigen --config ffigen.yaml to generate bindings