h3_flutter 0.4.0 h3_flutter: ^0.4.0 copied to clipboard
The package provides Dart version of the H3 Core library, a hexagon-based geographic grid system
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.
Tests #
To make tests work you need to execute prepare_tests.sh
script. The script builds h3 library from C code.
The script is designed for macOS and therefore it probably work only under this system.
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 c/h3lib
folder:
cmake ..
rm -rf ../../../c/h3lib // recreate the folder to remove old h3 files
mkdir ../../../c/h3lib
cp src/h3lib/include/h3api.h ../../../c/h3lib
Copy other source files (*.h and *.c) to the folder.
cd ..
cp src/h3lib/include/* ../../c/h3lib
cp src/h3lib/lib/* ../../c/h3lib
Copy c/h3lib folder to ios and macos folders with sync_h3lib.sh
script:
sh sync_h3lib.sh
You need to add .h and .c files to the project using XCode if you want to launch example (for iOS and macOS).
You can 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