ratex

KaTeX-compatible mathematics rendering for Dart and Flutter. The Rust RaTeX engine handles mathematics, mhchem chemistry, and proof trees. It runs through FFI on native platforms and WebAssembly in browsers, using the same display-list format.

Native builds require Rust in addition to Dart or Flutter. Precompiled binary releases are planned.

This is a melos monorepo:

Package	What it is
packages/ratex_dart	Pure Dart (no Flutter); works in CLI tools and browsers. Renders LaTeX to display lists and self-contained SVG over dart:ffi natively and WebAssembly on the web, with a pluggable backend registry.
packages/ratex	Flutter plugin. Builds the native library automatically (via cargokit), bundles the KaTeX fonts, provides the RatexMath widget and RatexPainter, and re-exports the ratex_dart API.
packages/ratex/rust	Rust crate ratex_ffi (the portable C ABI behind both backends), shipped inside the Flutter plugin so cargokit can build it from a published package. One (pointer, length)-based ABI compiled as cdylib/staticlib for FFI and as wasm32-unknown-unknown for the web, no wasm-bindgen glue.
packages/ratex_wasm	JS package (@manymath/ratex-wasm, unpublished) for browsers and Node.js: loads the import-free ratex_ffi.wasm and renders SVG, display lists, sub-expression boxes, and into DOM elements.
apps/ratex_example	Minimal cross-platform Flutter application demonstrating one RatexMath expression without product state or external design-system dependencies.

Quick start (Dart CLI)

import 'package:ratex_dart/ratex_dart.dart';

final list = await Ratex.renderDisplayList(r'\frac{-b \pm \sqrt{b^2-4ac}}{2a}');
print(list); // DisplayList(14 items, 7.02em x 2.28em)
final svg = await Ratex.renderSvg(r'E = mc^2'); // self-contained, fonts embedded

Build the native library first: cargo build --release --manifest-path packages/ratex/rust/Cargo.toml.

Quick start (Flutter)

import 'package:ratex/ratex.dart';

RatexMath(r'\sum_{n=1}^{\infty} \frac{1}{n^2} = \frac{\pi^2}{6}', fontSize: 28)

cargokit compiles the native library and bundles its fonts during flutter build on Android/iOS/Linux/macOS/Windows. For Flutter web, build ratex_ffi.wasm once (melos run native:build:web) and serve it from your app's web/ directory.

Runnable demos

# CLI: display-list summaries + a self-contained SVG file.
dart run packages/ratex_dart/example/ratex_dart_example.dart

# Browser (no Flutter): LaTeX -> SVG, all client-side.
melos run native:build:web
dart compile js packages/ratex_dart/example/web/main.dart -o packages/ratex_dart/example/web/main.dart.js
python3 -m http.server -d packages/ratex_dart/example/web 8080

# Flutter: formula playground with presets and live editing.
cd packages/ratex/example && flutter run          # native
cd packages/ratex/example && flutter run -d chrome # web

# Minimal application integration.
cd apps/ratex_example && flutter run -d chrome

Status

Host	Status
Linux	Working (native FFI, verified end to end)
Web	Working (WebAssembly, verified end to end, dart2js and Flutter web)
macOS	Expected to work (pure-Rust engine; cargokit configured)
Windows	Expected to work (pure-Rust engine; cargokit configured)
Android	Expected to work (pure-Rust engine; cargokit configured)
iOS	Expected to work (pure-Rust engine; cargokit configured)

Planned work includes rendering in an isolate, PNG/PDF export, precompiled binaries, and upstream engine integration.

Development

Driven by melos (config lives in the root pubspec.yaml). The workspace includes the Flutter plugin and apps, so working in this repository requires the Flutter SDK (which bundles Dart); a standalone Dart SDK can't resolve it. The ratex_dart package itself has no Flutter dependency, so projects that depend on it need only Dart.

After flutter pub get:

dart run melos run native:build       # build the Rust dylib (release)
dart run melos run native:build:web   # build ratex_ffi.wasm + copy to web examples
dart run melos run native:test        # Rust crate tests
dart run melos run analyze            # analyze all packages
dart run melos run format             # check Dart formatting (format:fix to apply)
dart run melos run test               # Dart + Flutter tests

Building the Rust crate requires a stable Rust toolchain with the wasm32-unknown-unknown target for web builds (rustup target add wasm32-unknown-unknown). native:build:web builds without the crate's default system-fonts feature, so the module has no imports, and shrinks it with wasm-opt -Oz when binaryen is installed.

Licenses

MIT (see LICENSE). The bundled KaTeX fonts are SIL OFL 1.1 (see packages/ratex/lib/fonts/). RaTeX itself is MIT.