glyphs

Optically centered icon glyphs for Flutter, built from Font Awesome Free 7.x.

Standard Font Awesome glyphs are designed inside per-icon viewBoxes that do not coincide with the glyph's visual center. Dropped into a circular FAB or square Icon slot they often look slightly off-axis. This package solves that with per-glyph minimum-enclosing-circle (MEC) center baking: each glyph is shifted at font-build time so its MEC center lands at the viewBox center. The result: every extreme ink point sits on the same circle, so the glyph is equally distant from any larger concentric container.

Icon (Flutter's standard widget) renders glyphs from this font correctly with no wrapping widget — the centering is part of the font itself.

Installation

dependencies:
  glyphs:
    git:
      url: https://github.com/swipelab/glyphs

Usage

import 'package:flutter/widgets.dart';
import 'package:glyphs/glyphs.dart';

Icon(GlyphsSolid.anchor, size: 32)
Icon(GlyphsRegular.bell, size: 24)
Icon(GlyphsBrands.github, size: 20)

find.byIcon, IconButton, ListTile.leading and friends all work as expected — the package doesn't introduce any custom widgets.

How the correction is computed

Each glyph is rasterized at 256 px in a 512 px canvas (so heavily-shifted glyphs don't clip). The ink silhouette is extracted, then Welzl's algorithm computes the minimum enclosing circle. The offset from canvas center to MEC center is recorded as two em-fractions (dx, dy).

At font-build time tool/build_font.py bakes those offsets into each glyph: vertical shifts are applied via the path transform, horizontal shifts via the left side bearing (because Flutter/HarfBuzz re-anchors single glyphs to origin + lsb at render time, so a horizontal path shift on its own would be discarded).

The full offset table lives at assets/offsets.json and is mirrored as Dart constants in lib/src/glyph_offsets.g.dart for inspection — runtime rendering does not consume it.

Rebuilding the font

The fonts, codepoint tables, and Dart constants are all generated. Run:

dart run tool/build_font.dart

The build:

1. Hashes each icon name into a per-style PUA sub-range (FNV-1a + linear probing). The result is deterministic across machines.
2. Calls tool/build_font.py (uses fontTools) to compile each style into a TTF, converting cubic outlines to quadratics.
3. Runs flutter test tool/measure_offsets.dart to compute the MEC-center correction table via Welzl's algorithm.
4. Re-runs the python build with the offsets baked in (pass 2).
5. Regenerates lib/src/glyphs.g.dart and lib/src/glyph_offsets.g.dart.

System requirements

• Dart / Flutter SDK
• Python 3 with fontTools

  brew install python      # macOS, if needed
  pip3 install fonttools

The build script verifies both at startup and prints install instructions if either is missing.

Codepoint stability

Codepoints are derived from FNV-1a(name) mod range, with linear probing on collision. The full assignment is checked in at assets/codepoints.json so any drift caused by adding or removing icons is visible in code review.

Attribution

Icons are derived from Font Awesome Free by Fonticons, Inc., licensed under CC BY 4.0. See NOTICE.md for the full attribution and the list of changes made.

This package is not affiliated with, endorsed by, or sponsored by Fonticons, Inc.

License

• Code: MIT
• Icon artwork (SVGs and compiled glyph outlines): CC BY 4.0

See LICENSE and NOTICE.md.