feat(tools): add the font-coverage gate (RIG-3603) - #1208
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T8 retires the Unifont fallback pin from the e2e font set (`tools/toolchain/chromium-e2e-env.nix`). That is only safe once nothing in `apps/ui/src` renders a character the two branded faces lack, and until now the check for that was an eyeball pass over a hand-written census. The census has been wrong twice: it classified characters as safe prose by appearance, and `⟨`/`⟩`/`⌗` turned out to be absent from Space Mono while `−` and `→`, both assumed to need conversion, turned out to be present. The gate parses the `cmap` of `SpaceMono-Regular.ttf` and `DepartureMono-Regular.otf` (format 4 and format 12, TrueType and CFF), scans `apps/ui/src` for non-ASCII characters in rendered positions, and reports the ones neither face covers. Comments are stripped line-preservingly and string- aware, so a `//` inside a literal is not mistaken for a comment and a finding's reported line number survives the strip. The covered set is Space Mono's cmap alone, not the union of both faces. `--rigel-display` (Departure Mono) is used by exactly one rule (`apps/ui/src/app.css:444`); everything else resolves `--rigel-mono`, so a character present only in the display face still falls through to the pinned fallback at a body-text site. Departure is loaded, counted and plausibility-checked — it proves the format-12 parse path — but findings clear against Space Mono. That is deliberately conservative: at the single display site the gate can over-report, never under-report, so it cannot green a site that still needs the fallback. It runs in WARN mode (reports, exits 0) because 8 characters are uncovered today; `FONT_COVERAGE_GATE=error` exits non-zero, and T8 flips the default. A gate that cannot tell a clean tree from one it never read is worse than none, so a missing or unparseable font face exits 2 in both modes rather than reporting zero findings. Registered in `.moon/workspace.yml`: moon discovers projects only from that map, and an unregistered tool never runs. Verified: 15 unit tests pass; injecting a naive line-deleting comment strip reddens 2 of them, so the line-number assertion discriminates. Against the live tree the gate reports 24 findings over 8 distinct codepoints (`▸ ■ ⟩ ⟨ ⎇ ⌗ ➜ ▪`), matching an independent cmap measurement; warn exits 0, error exits 1, a missing font exits 2, a truncated font exits 2.
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September 13, 2026 20:10
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T8 retires the Unifont fallback pin from the e2e font set
(
tools/toolchain/chromium-e2e-env.nix). That is only safe once nothing inapps/ui/srcrenders a character the two branded faces lack, and until now thecheck for that was an eyeball pass over a hand-written census. The census has
been wrong twice: it classified characters as safe prose by appearance, and
⟨/⟩/⌗turned out to be absent from Space Mono while−and→, bothassumed to need conversion, turned out to be present.
The gate parses the
cmapofSpaceMono-Regular.ttfandDepartureMono-Regular.otf(format 4 and format 12, TrueType and CFF), scansapps/ui/srcfor non-ASCII characters in rendered positions, and reports theones neither face covers. Comments are stripped line-preservingly and string-
aware, so a
//inside a literal is not mistaken for a comment and a finding'sreported line number survives the strip.
The covered set is Space Mono's cmap alone, not the union of both faces.
--rigel-display(Departure Mono) is used by exactly one rule(
apps/ui/src/app.css:444); everything else resolves--rigel-mono, so acharacter present only in the display face still falls through to the pinned
fallback at a body-text site. Departure is loaded, counted and
plausibility-checked — it proves the format-12 parse path — but findings clear
against Space Mono. That is deliberately conservative: at the single display
site the gate can over-report, never under-report, so it cannot green a site
that still needs the fallback.
It runs in WARN mode (reports, exits 0) because 8 characters are uncovered
today;
FONT_COVERAGE_GATE=errorexits non-zero, and T8 flips the default. Agate that cannot tell a clean tree from one it never read is worse than none, so
a missing or unparseable font face exits 2 in both modes rather than reporting
zero findings.
Registered in
.moon/workspace.yml: moon discovers projects only from that map,and an unregistered tool never runs.
Verified: 15 unit tests pass; injecting a naive line-deleting comment strip
reddens 2 of them, so the line-number assertion discriminates. Against the live
tree the gate reports 24 findings over 8 distinct codepoints (
▸ ■ ⟩ ⟨ ⎇ ⌗ ➜ ▪),matching an independent cmap measurement; warn exits 0, error exits 1, a missing
font exits 2, a truncated font exits 2.