ratex_flutter

ratex_flutter

KaTeX-compatible math rendering for Flutter, on every platform, including the web. Wraps the pure-Dart ratex package (which drives the Rust RaTeX engine) and adds:

• RatexMath: a widget that lays out a LaTeX formula and paints it with the bundled KaTeX fonts. Inherits the ambient text color; reports parse errors (with source spans) through errorBuilder.
• RatexPainter: the underlying CustomPainter, for painting display lists onto your own canvas.
• Automatic native builds: the ratex_ffi Rust crate is compiled by cargokit during flutter build on Android, iOS, Linux, macOS, and Windows. Rust is the only extra build-time requirement, and precompiled binaries can remove even that.
• Bundled fonts: the KaTeX fonts ship with the package and are referenced as packages/ratex_flutter/<family>, so apps need no font configuration. (Fonts are SIL OFL 1.1; see lib/fonts/.)

import 'package:ratex_flutter/ratex_flutter.dart';

// Optional but recommended: eager init in main() so load errors surface
// early and all later renders are synchronous.
await RatexFlutter.ensureInitialized();

// Anywhere in your tree:
RatexMath(r'\frac{-b \pm \sqrt{b^2-4ac}}{2a}', fontSize: 28)

The full package:ratex API is re-exported: Ratex.renderDisplayList, Ratex.renderSvg, custom backends, options, and models.

Web

Flutter web has no dart:ffi, so the same engine runs as WebAssembly:

1. Build the binary: melos run native:build:web (in this repo), or cargo build --release --target wasm32-unknown-unknown in native/ratex-ffi.
2. Serve ratex_ffi.wasm from your app's web/ directory (files there ship verbatim with a web build), matching the default Ratex.wasmUrl. Or bundle it as an asset and pass wasmAsset: to RatexFlutter.ensureInitialized, or set Ratex.wasmBytes yourself.

Example

example/ is a formula playground: presets, live LaTeX editing, font-size slider, display/inline toggle. flutter run on any platform (see its README for the one-step web setup).