anchorsfactory 0.2.0

Rule-driven anchor placement for UFO fonts

AnchorsFactory

Rule-driven anchor placement for UFO fonts. You describe, in a compact text file, where anchors should sit on your glyphs; AnchorsFactory computes the coordinates from each glyph's own geometry and writes the anchors into the font.

It does the pre-marking step of accent handling: place top/bottom/_top/… anchors consistently across hundreds of glyphs, so a tool like GlyphConstruction can then assemble composite glyphs by snapping mark anchors to base anchors.

Install

pip install anchorsfactory          # once published
# or, from a checkout:
pip install -e .

Requires Python 3.10+, fontParts and fontTools.

Quick start

# place anchors using the bundled default ruleset, save to font_anchored.ufo
anchorsfactory MyFont.ufo --rules default

# your own rules, overwrite in place, with a backup of existing anchors
anchorsfactory MyFont.ufo --rules my-rules.af --in-place --backup-dir backups/

# a whole folder of UFOs
anchorsfactory masters/ --rules default

By default the source UFO is never overwritten — output goes to *_anchored.ufo unless you pass --in-place.

The rule language

Rules are stacked: define reusable labels, then mark glyphs with them, mixing labels and one-off anchors. An anchor is a name and a parenthesised X Y placement.

# a label
@ = top (box.center capHeight), bottom (box.center 0)

# apply it, by name / unicode / range
A = @, ogonek (outline.right 0)
U+0410..U+044F = @            # all Russian Cyrillic
U+0413 += desc (outline.right 0)   # Г also gets a descender anchor

• X is frame.position: width.* (advance), box.* (bounding box) or outline.* (the contour at height Y, with .first/.last to pick a stem).
• Y is a number, a font metric (capHeight, xHeight, ascender, …), or a reference glyph ($H, $H.bottom, $H*5/6).
• Selectors: name, U+XXXX, range U+A..U+B, glob *.sc, category {Lu}.
• = replace · += add · -= remove; !extends default inherits a ruleset.

Full reference: docs/anchor-rules.md.

Presets and migration

Bundled rulesets default and default-italics are usable by name in --rules or !extends. Old .txt rule files (see examples/) convert to the new syntax — verified lossless:

anchorsfactory-convert examples/default-anchors-list.txt -o my-rules.af

Library API

from anchorsfactory import process_ufo, load_document, apply_document

process_ufo("MyFont.ufo", "default")          # high-level: open, apply, save

from fontParts.world import OpenFont
font = OpenFont("MyFont.ufo")
apply_document(font, load_document("my-rules.af"))
font.save()

Development

make venv      # create .venv, install the package (editable) + dev deps, via uv
make test      # run the test suite
make build     # build sdist + wheel into dist/

License

See LICENSE.