icon_font_extractor

Generate strongly-typed IconData constants from any icon font's ligature table (GSUB). Drop a font into your pubspec.yaml, add a single icon_fonts: entry, run a command, and use the icons with Flutter's built-in Icon widget — no boilerplate, no hand-curated codepoint maps.

Why?

Icon fonts (Material Icons, Material Symbols, custom Figma exports from IcoMoon / Fontello, FontAwesome Pro…) ship a GSUB ligature substitution table that maps human-readable strings like "home", "arrow_back", "settings_outlined" to glyphs. Flutter's Icon widget renders glyphs by codepoint, not by ligature, which means you normally have to hand-write or copy/paste a static const IconData for every icon you use.

icon_font_extractor reads the font's GSUB + cmap tables in pure Dart and emits that boilerplate for you.

Plus: Flutters Tree-Shaking for icons works out-of-the-box!

Install

You don't even need to install that package inside your app. Just install it globally with

dart pub global activate icon_font_extractor

Configure

Update your Apps pubspec.yaml:

flutter:
  fonts:
    - family: MaterialIcons # <-- Add your icon font
      fonts:
        - asset: assets/fonts/MaterialIcons-Regular.otf

# Run `icon_font_extractor generate` from this directory after
# `flutter pub get` to (re)generate `lib/material_icons.dart`.
icon_fonts:
  - family: MaterialIcons        # must match a family under flutter.fonts
    outputFile: lib/material_icons.g.dart
    # outputFamily: MaterialSymbols  # optional: overrides fontFamily in generated IconData
    # iconPrefix: icn               # optional: identifier prefix (default: icn)
    # naming: snake                # optional: snake (default), pascal, camel, keep
    # useLigatures: true          # optional: true (default) = GSUB ligatures, false = cmap + post table

Generate

# Run
icon_font_extractor generate

You'll get a generated file like:

// GENERATED CODE - DO NOT MODIFY BY HAND.
import 'package:flutter/widgets.dart';

@staticIconProvider
abstract final class MyIcons {
  MyIcons._();

  /// Ligature: `home`
  static const IconData icnHome = IconData(0xE900, fontFamily: 'MyIcons');

  /// Ligature: `search`
  static const IconData icnSearch = IconData(0xE901, fontFamily: 'MyIcons');
  // ...
}

Use

Icon(MyIcons.icnHome, size: 32, color: Colors.blue)

That's it — the generated IconData works with every existing Flutter widget that accepts IconData (Icon, IconButton, BottomNavigationBarItem, …).

CLI flags

Flag	Description
--pubspec <path>	Path to the pubspec.yaml (default: pubspec.yaml).
--check	Don't write; exit non-zero if any output would change. CI-friendly.
--verbose	Extra diagnostic output.
--help	Show usage.

Naming rules

The iconPrefix key (default icn) is prepended to every identifier. The naming key controls how ligature words are cased:

Strategy	Example ligature	Result (prefix icn)
snake (default)	arrow_back_ios	icn_arrow_back_ios
pascal	arrow_back_ios	IcnArrowBackIos
camel	arrow_back_ios	icnArrowBackIos
keep	arrowBack_iOS	icnarrowBack_iOS

Additional sanitisation applied for all strategies:

• Whitespace is removed.
• Characters that are not valid in a Dart identifier are replaced with _.
• Duplicate identifiers are disambiguated with a numeric suffix (icnHome, icnHome2, icnHome3, …).

How codepoints are chosen

useLigatures: true (default)

The generator reads the font's GSUB table (LookupType 4 ligature substitution) to map multi-character ligature strings to glyph IDs, then finds each glyph's codepoint via cmap, preferring Unicode Private Use Areas. This is the best choice for icon fonts that encode icon names as OpenType ligatures (e.g. Material Icons, Font Awesome).

useLigatures: false

Use this for fonts that have no GSUB ligatures but expose icon names via the post table. The generator iterates every entry in cmap, looks up the glyph name from the post table, and uses that as the icon identifier. The same naming strategies apply. Glyph names in the standard placeholder set (.notdef, space, etc.) are skipped. If no post table is present, a hex-based fallback name (uE001) is used.

icon_fonts:
  - family: MyCustomIcons
    outputFile: lib/my_custom_icons.g.dart
    useLigatures: false

Limitations

• Only LookupType 4 (Ligature Substitution) is read from GSUB; LookupType 7 (Extension Substitution) wrappers around type 4 are unwrapped automatically.
• Contextual / chained substitutions are not consulted.
• TrueType collections (ttcf) are not supported — point at a single-font TTF/OTF.

License

MIT — see LICENSE.