Fontforge Utility Plugin on References and Selections

This plugin helps finding:

• Glyphs with nested references and flatten such references
• Glyphs with distorted references and unlink references
• Unused glyphs and remove them

Required Python version is:

• 3.9 to 3.11 for limited features
  • "Select unused glyphs" menu will be disabled in this case due to possible crash
• 3.12 or later for full features

Details

Glyphs with nested references

Nested references are known to cause problems in certain environments. More information can be found at fontbakery issue 2961 and arrowtype issue 412.

Glyphs with distorted references

While each references can have affine transformation, ttfautohint tool cannot deal with distorted references well. Unlinking such references will be needed if you plan to use ttfautohint.

Unused glyphs (Python ≥ 3.12 only)

When a glyph is expressed as unused or unreachable, such glyphs neither has Unicode encodings nor is referenced from another glyph or a GSUB table. They can be dropped to reduce the file size.

Install

pip3 install fontforge-ref-sel-util

Make sure Fontforge Python module is usable

In interactive mode of Python, run:

import fontforge

If it raises ModuleNotFoundError exception, install Fontforge first. If installed, make sure the build option set that the Python module gets also installed. If already so, Python interpreter does not recognize the module path where the required module.

export PYTHONPATH=/path/to/fontforge/python/module:$PYTHONPATH

Usage

In Fontforge GUI

This plugin adds following items into "Tools" menu:

• Select
  • Glyphs with nested references
  • Glyphs with distorted references
  • Glyphs referring currently selected glyphs
    • Direct refs only
    • Including indirect refs
  • Unused glyphs
• Decompose nested references

In Python script

import fontforge
import fontforge_refsel

font = fontforge.open('path/to/font.sfd')

# Select glyphs with nested references
fontforge_refsel.selectGlyphsWithNestedRefs(font)      # set selection
fontforge_refsel.selectGlyphsWithNestedRefs(font, 0)   # set selection
fontforge_refsel.selectGlyphsWithNestedRefs(font, 1)   # append selection
fontforge_refsel.selectGlyphsWithNestedRefs(font, -1)  # deselect

# Select glyphs with distorted references
# (i.e. non-identity linearly transformed references)
fontforge_refsel.selectGlyphsWithDistortedRefs(font)      # set selection
fontforge_refsel.selectGlyphsWithDistortedRefs(font, 0)   # set selection
fontforge_refsel.selectGlyphsWithDistortedRefs(font, 1)   # append selection
fontforge_refsel.selectGlyphsWithDistortedRefs(font, -1)  # deselect

# Select unreachable glyphs
fontforge_refsel.selectUnusedGlyphs(font)      # set selection
fontforge_refsel.selectUnusedGlyphs(font, 0)   # set selection
fontforge_refsel.selectUnusedGlyphs(font, 1)   # append selection
fontforge_refsel.selectUnusedGlyphs(font, -1)  # deselect

# Check a glyph
glyph = font['foo']
result = fontforge_refsel.glyphHasNestedRefs(glyph)
result = fontforge_refsel.glyphHasDistortedRefs(glyph)
result = glyph.glyphname in fontforge_refsel.unusedGlyphs(font)

# List of glyphs with...
result = [glyph.glyphname for glyph in filter(fontforge_refsel.glyphHasNestedRefs, font.glyphs())]
result = [glyph.glyphname for glyph in filter(fontforge_refsel.glyphHasDistortedRefs, font.glyphs())]
result = list(fontforge_refsel.unusedGlyphs(font))  # unusedGlyphs() returns a frozenset object

# Decompose nested references
fontforge_refsel.decomposeNestedRefs(font)         # selected glyphs
fontforge_refsel.decomposeNestedRefs(font, False)  # selected glyphs
fontforge_refsel.decomposeNestedRefs(font, True)   # all glyphs
# if no glyphs are selected, processes all glyphs

# Unlink distorted references (Python < 3.12 may crash)
fontforge_refsel.selectGlyphsWithDistortedRefs(font)
font.unlinkReferences()
font.removeOverlap()  # may or may not needed

# Drop unused glyphs (Python < 3.12 may crash)
for glyph in fontforge_refsel.unusedGlyphs(font):
    font.removeGlyph(glyph)

# Check what glyph refers certain glyph
glyph = font['foo']
result = fontforge_refsel.whatRefers(glyph)         # direct references only
result = fontforge_refsel.whatRefers(glyph, False)  # direct references only
result = fontforge_refsel.whatRefers(glyph, True)   # also indirect references