Extracting resident fonts from a Genera world

Bottom line

The tracked scripts/extract-genera-fonts.py program recovers the one-bit glyphs and display metrics of resident FONT objects directly from a little-endian VLM VLOD V2 world. For the inspected Genera 8.5 base world it finds 89 distinct font objects. A separate symbol walk finds 90 bindings because TV:*DEFAULT-FONT* and FONTS:CPTFONT point to the same object.

This repository's direct licensed-world extraction products are generated under build/fonts/genera/, which is ignored by Git, and must not be committed here. The extractor contains no font bitmaps and remains the tracked re-extraction deliverable.

A separate public Genera Fonts repository publishes a closed font-only reproduction of the same 89 resident objects as raw and Unicode BDF, Unicode-derived OTB, normalized records, and specimens. It excludes the VLOD, supplied Genera BFD/BDF files, source, executable code, manuals, Help, and unrelated heap data. Its NOTICE.md states the U.S. “typeface as typeface” publication basis and separates the historical glyph-shape payload from the BSD-licensed project tooling. Use that reviewed corpus, not this repository's local build/ intermediates, when a public font package is needed.

Reproduce the extraction

The examples assume the licensed Open Genera installation is in the repository's usual local-only .lm-home directory. List the resident fonts without writing any derived files:

python3 scripts/extract-genera-fonts.py \
  .lm-home/opengenera/runtime/Genera-8-5.vlod \
  --list

Extract the complete local collection:

python3 scripts/extract-genera-fonts.py \
  .lm-home/opengenera/runtime/Genera-8-5.vlod \
  --output build/fonts/genera \
  --clean

Validate the decoded world objects against the BDF and BFD files supplied with the same licensed Genera release:

python3 scripts/extract-genera-fonts.py \
  .lm-home/opengenera/runtime/Genera-8-5.vlod \
  --output build/fonts/genera \
  --clean \
  --reference-bdf-dir \
    .lm-home/opengenera/runtime/sys.sct/x11/fonts/bdf/genera \
  --reference-bfd-dir \
    .lm-home/opengenera/runtime/sys.sct/fonts/tv

One font or glyph can be inspected without extracting the whole collection:

python3 scripts/extract-genera-fonts.py \
  .lm-home/opengenera/runtime/Genera-8-5.vlod \
  --font CPTFONT --glyph 0o101

--glyph accepts Python-style hexadecimal or octal notation. Run --help for sheet scale, column-count, and filtering options.

An existing output directory is rejected unless --clean is explicit. Clean mode removes only the extractor-owned bdf, json, sheets, manifest, and validation paths; it refuses to proceed if the directory contains an unrecognized entry. This prevents renamed or removed fonts from leaving stale derivatives in a later run.

Generated files

Each extraction writes:

• manifest.json, with source filename, byte size, SHA-256 digest, format, font count, metrics, and generated relative paths;
• json/*.json, normalized glyph rasters and metrics for machine inspection;
• bdf/*.bdf, a portable reconstruction of the represented display font;
• sheets/*.png, deterministic visual inventories of all represented glyphs; and
• validation.json when either reference-directory option is supplied.

The specimen sheets sort glyphs by code and label them in octal, the convention used by much Lisp-machine documentation and source material. A pale horizontal line in each cell marks the decoded baseline. The dark pixels are positioned using the resident advance, left-kern, vertical offset, raster height, and baseline values; the sheet is therefore also a visual check of placement rather than only a bitmap dump.

Do not link these local sheets from the public catalog or copy them into docs/. Their predictable location is build/fonts/genera/sheets/<lowercase-name>.png, for example build/fonts/genera/sheets/cptfont.png.

What the decoder reconstructs

The program reads the VLOD header and load map, reconstructs tagged Qs at their Genera virtual addresses, follows forwarding pointers, and recognizes rank-two one-bit arrays whose named structure is FONT. It then decodes the array leader, packed raster, per-character existence, width, indexing, and left-kern tables. It also handles the historical non-spacing character slots that some fonts retain above their apparent array fill pointer; simply iterating to the fill pointer would omit those glyphs.

This is an effect-level reconstruction of the resident screen asset. It preserves the represented pixels and the basic metrics needed to position them. It does not claim to recreate byte-identical source BFD or BDF files, comments, discarded authoring properties, source filenames, or an earlier tool's choice of compact glyph rectangle. For preservation of the supplied authoring representation, the licensed release's separate font files remain preferable to a heap reconstruction.

Raster display fonts and outline hardcopy fonts

All 89 objects recovered by this extractor are raster fonts: each is a rank-two, one-bit FONT array containing display pixels and associated metrics. This agrees with Genera's documented screen-font model and with the BDF representations supplied for the Genera X client. Scaling or rotating an image made from one of these fonts does not turn its stored representation into an outline font.

That result must not be generalized to mean that Genera had no outline-font support. The licensed Genera 8.5 PostScript hardcopy source has a separate font abstraction with both built-in and downloadable outline-font classes. Built-in PostScript device fonts are selected by family and point size. For downloadable fonts, Genera can read Bitstream BSFONT character contours, retain their outline segments, and emit the used contours as a scalable PostScript Type 3 font. The same hardcopy implementation also supports downloadable bitmap fonts. These objects are not named one-bit FONT arrays, so the resident-screen-font extractor neither enumerates nor converts them.

A low-level audit of the exact base world identified below enumerated every mapped data-page Q with the tracked VLOD reader, found the compiled outline-font machinery and two symbol objects named BS-FONT, and checked every reference to those symbols. It found no property-list association of the form used to register a loaded Bitstream font family. The evidence therefore supports this narrower conclusion: the base world contains the implementation, but does not appear to contain a configured downloadable Bitstream outline-font library. This reference audit is not a complete heap decompiler, so it is not formal proof that no unreachable contour-shaped object could exist.

For preservation work, the useful distinction is:

Validation result

The matching Genera 8.5 release provides two useful, independent comparisons. The validation command above produced these results:

The BFD comparison covers font name, line spacing, baseline, default width, character-code set, per-character advance, and positioned pixels. The BDF comparison covers character-code set, DWIDTH, BBX, and bitmap. It deliberately does not claim equality for untested properties, comments, scalable-width convention, or file bytes. The two substantive BDF differences are retained as findings, not silently normalized away. Whether they reflect a different source revision, a load-time transformation, or another cause remains TODO; the matching BFD fields show that the world decoder agrees with the supplied native font assets for those objects within this comparison boundary.

Artifact and implementation scope

The observations on this page apply to this exact licensed local artifact:

• filename: Genera-8-5.vlod;
• size: 54,804,480 bytes;
• SHA-256: a8ee5e86cc7e322f7385af3e0cd579d7650d4dcfc3ce328acbf8b25515dd0672;
• format accepted by the extractor: little-endian VLM VLOD V2.

The decoder is intentionally narrower than a general Genera heap reader. It supports the VLOD operations and array layouts needed by this world and fails on a wrong cookie or unsupported structure rather than treating arbitrary data as a font. Results for another release or an incremental world must be validated again.

For the distinction between resident assets and original source files, see Recovering code and assets from a Genera world. For the complete evidence-graded inventory, see the Genera 8.5 resident font catalog.

Sources

• Symbolics, Programming the User Interface, especially PDF pages 344–347, for screen-font representation and metrics.
• Symbolics, Open Genera User's Guide, “Font Support in the Genera X Client,” for the supplied X BDF fonts.
• X Consortium, Glyph Bitmap Distribution Format 2.1, for the public BDF interchange format.
• Genera Fonts, commit 892fa057622389b43cdd8f725dc5a2384ab656f8, for the closed public 89-font reproduction, conversion pipeline, provenance, and publication notice.
• Licensed Genera 8.5 source inspected locally, identified without quotation or redistribution: sys.sct/io1/lfont-defs.lisp.~2~, sys.sct/io1/bfd.lisp.~135~, sys.sct/io1/bfd-misc.lisp.~1521~, and sys.sct/io1/pxl.lisp.~1520~ for screen fonts, plus sys.sct/hardcopy/postscript.lisp.~1681~ for built-in, bitmap-downloadable, and outline-downloadable hardcopy font handling.

Last verified: 2026-07-26.