native_spell_checker

A Flutter plugin for native OS spell checking on desktop (Windows, Linux) — zero bundled dictionaries, uses the operating system's built-in spell checker. On Android, it defers to Flutter's built-in DefaultSpellCheckService.

• pub.dev: https://pub.dev/packages/native_spell_checker
• Repository: https://github.com/Sebastien-VZN/native_spell_checker

For the full technical reference (architecture, design decisions, testing protocol), see README_GH.md.

Version française : README_FR.md.

Screenshots

Windows	Linux	Android

Features

• Windows: Uses WinRT ISpellChecker2 (COM API) via the win32 package.
• Linux: Uses libhunspell-1.7 system library via dart:ffi. Dictionaries are read from /usr/share/hunspell/.
• Android: Defers to Flutter's built-in DefaultSpellCheckService (no code needed).
• Zero bundled dictionaries — the OS provides everything.
• Multi-language — automatically uses the OS-installed dictionaries for the current locale.
• 100% offline — no cloud APIs, no network calls.
• Context menu suggestions — right-click a misspelled word on desktop to see OS suggestions.
• Drop-in widgets — SpellCheckTextField / SpellCheckTextFormField as direct replacements for TextField / TextFormField.

Getting started

Add the dependency:

dependencies:
  native_spell_checker: ^0.4.0

Linux prerequisite

The libhunspell-1.7-0 package must be installed on the target system. On Debian/Ubuntu:

sudo apt-get install libhunspell-1.7-0 hunspell-fr hunspell-en-us

Dictionaries are provided by hunspell-* packages and stored in /usr/share/hunspell/.

Usage

Option A — drop-in widget (recommended)

Use SpellCheckTextField or SpellCheckTextFormField as a drop-in replacement for TextField / TextFormField. Spell checking, context menu suggestions, and right-click caret positioning are all pre-wired:

import 'package:native_spell_checker/native_spell_checker.dart';

SpellCheckTextField(
  controller: myController,
  maxLines: 5,
  decoration: const InputDecoration(hintText: 'Type here...'),
)

For forms with validation:

SpellCheckTextFormField(
  controller: myController,
  validator: (value) => value!.isEmpty ? 'Required' : null,
  maxLines: 5,
  decoration: const InputDecoration(hintText: 'Type here...'),
  misspelledTextStyle: myCustomStyle,
  misspelledSelectionColor: Colors.red,
)

Why the wrapper widget?

On desktop (Windows, Linux), Flutter's TextField does not reposition the caret when the user right-clicks. The internal TextSelectionGestureDetector only stores the tap position to anchor the context menu visually — it does not move the text selection to the clicked word. So the context menu's suggestions are looked up at the current caret position, not at the word the user actually right-clicked.

SpellCheckTextField / SpellCheckTextFormField wrap the native TextField / TextFormField in a Listener that intercepts the secondary button (right-click), repositions the caret to the clicked word via RenderEditable.getPositionForPoint, then lets Flutter open the context menu normally. The suggestions shown are for the right-clicked word, without requiring a prior left-click selection.

On Android, the wrapper is a no-op — the OS handles everything natively.

Option B — manual wiring

If you need full control, wire the three building blocks yourself:

import 'package:flutter/gestures.dart' show kSecondaryButton;
import 'package:native_spell_checker/native_spell_checker.dart';

final GlobalKey _key = GlobalKey();

Listener(
  onPointerDown: (event) {
    if (event.buttons == kSecondaryButton) {
      NativeSpellChecker.onSecondaryTapDown(_key, controller, event);
    }
  },
  child: TextField(
    key: _key,
    controller: controller,
    spellCheckConfiguration: NativeSpellChecker.configuration(),
    contextMenuBuilder: NativeSpellChecker.contextMenuBuilder,
  ),
)

Available building blocks:

• NativeSpellChecker.configuration(misspelledTextStyle) — returns a SpellCheckConfiguration wired to the OS spell checker.
• NativeSpellChecker.contextMenuBuilder — builds a context menu with spelling suggestions above the standard Cut/Copy/Paste/Select All buttons.
• NativeSpellChecker.onSecondaryTapDown(key, controller, event) — repositions the caret to the right-click location.

Discover the language the spell checker will use

// null locale → resolve from the OS default locale.
final tag = await NativeSpellChecker.resolvedLanguageTag();
// e.g. "fr-FR" (Windows BCP-47) / "fr_FR" (Linux Hunspell) / null (Android)

// explicit locale → same fallback chain used during spell checking.
final enTag = await NativeSpellChecker.resolvedLanguageTag(locale: const Locale('en', 'US'));

Returns null on Android (where the plugin defers to Flutter). Use Platform.localeName to read the system locale on Android.

How it works

Platform	Backend	Dictionary source	Language tag format
Android	Flutter DefaultSpellCheckService	OS (TextServicesManager)	null (use Platform.localeName)
Windows	WinRT ISpellChecker2 (COM FFI)	OS (Windows SpellChecker)	BCP-47 (fr-FR, en-US)
Linux	libhunspell-1.7 (dart:ffi)	/usr/share/hunspell/	Hunspell (fr_FR, en_US)

Platforms

Platform	Status
Android	Manually validated
Linux	Manually validated
Windows	Manually validated
iOS	Not supported
macOS	Not supported

License

MIT — see LICENSE.