udpipe_flutter 0.1.0+1

Flutter library and demo app for UDPipe 1 — NLP tokenization, POS tagging and dependency parsing across 50+ languages, with native FFI on desktop/mobile and WebAssembly on the web.

UDPipe Flutter

NLP tokenization, POS tagging and dependency parsing using UDPipe 1, built with Flutter.

Native FFI on desktop and mobile. WebAssembly via Emscripten on the web.

Platforms

Platform	Status
Android	✅
Web	✅
Windows	✅
Linux	✅
macOS	✅
iOS	🚧 planned

Features

• Tokenization, lemmatization, POS tagging and dependency parsing
• Runs fully on-device (no server required)
• Separable verb detection for German
• 50+ pre-trained language models available from ÚFAL
• Async batch processing keeps the UI thread free

Getting Started

git clone --recursive https://github.com/konyshevgmbh/udpipe_flutter.git
flutter pub get
flutter run -d windows         # Windows desktop
flutter run -d linux           # Linux desktop
flutter run -d macos           # macOS desktop
flutter run                    # Android (device or emulator)

Web (WASM)

Build the WebAssembly module first, then run on Chrome:

make run-web                   # builds WASM via Docker, then launches Chrome

Requires Docker Desktop.

Model files

Download models from ufal.mff.cuni.cz/udpipe/1/models and place them in assets/models/:

Model ID	File	Size
gsd	german-gsd.udpipe	~20 MB
hdt	german-hdt.udpipe	~60 MB

Library API

import 'package:udpipe_flutter/udpipe_flutter.dart';

final svc = UDPipeService();

// Load a model once per session
await svc.init(modelId: 'gsd');

// Process text (synchronous)
final result = svc.process('Er steigt aus dem Bus aus.');

for (final sentence in result.sentences) {
  for (final token in sentence.tokens) {
    print('${token.form}  ${token.upos}  ${token.lemma}');
  }
  for (final sv in sentence.sepVerbs) {
    print('sep.verb: ${sv.particle}+${sv.verbForm} → ${sv.fullLemma}');
  }
}

// Async batch — runs in a background isolate
final results = await svc.processAllBlocksAsync(['Block one.', 'Block two.']);

Architecture

lib/udpipe/
  udpipe_flutter.dart          — public API
  src/
    conllu_parser.dart         — CoNLL-U parser (pure Dart)
    udpipe_types.dart          — data classes and result builders
    udpipe_bindings.dart       — dart:ffi bindings
    udpipe_service.dart        — conditional export (native vs web)
    udpipe_service_native.dart — FFI service (Windows / Linux / macOS / Android)
    udpipe_service_web.dart    — WASM/JS service (web)

native/
  CMakeLists.txt               — builds udpipe_flutter.dll / .so / .dylib
  udpipe_ffi.cpp               — thin C wrapper around UDPipe
  udpipe_src/                  — git submodule: ufal/udpipe
  build_web.sh                 — Emscripten build script

Tech Stack

Component	Library
UI	Flutter 3.x + Material 3
Native bindings	ffi
NLP engine	UDPipe 1 (C++, MPL 2.0)
Web engine	Emscripten WASM

License

Wrapper code — MIT
UDPipe © ÚFAL MFF UK — MPL 2.0