Decision 0014 - Exclude bitmap / non-OpenType fonts from inventory

Date: 26/01/2026 Status: Accepted

Context

Fontshow builds a structured font inventory intended for:

• OpenType / TrueType analysis
• Unicode coverage inspection
• LaTeX and typographic catalog generation
• Semantic validation of font metadata

During testing, it was observed that the system font database (via Fontconfig) may include legacy bitmap fonts (e.g. .pcf, .pcf.gz) that:

• are not OpenType or TrueType fonts
• are not supported by fontTools
• cannot be used by LuaLaTeX or HarfBuzz
• do not expose reliable family/style metadata
• often lack scalable outlines

These fonts appear in Fontconfig results but are not usable for Fontshow’s intended purposes.

Decision

Fontshow explicitly excludes bitmap and non-OpenType fonts from the inventory generation phase.

A font is excluded if:

• fonttools cannot parse it, or
• its detected format is not OpenType / TrueType

Such fonts are ignored during dump-fonts and never reach later pipeline stages.

Rationale

• Bitmap fonts cannot be used by LuaLaTeX
• They cannot be analyzed semantically
• They introduce invalid or incomplete entries
• They break inventory validation invariants
• Their inclusion provides no practical value

This decision keeps the inventory:

• semantically consistent
• usable for downstream tooling
• aligned with Fontshow’s purpose

Consequences

• Bitmap fonts (e.g. PCF) are silently skipped
• Inventory size is reduced but semantically correct
• No changes are required in parse-inventory
• No schema changes are needed

Alternatives considered

Accept bitmap fonts

Rejected — leads to invalid or unusable inventory entries.

Treat bitmap fonts as warnings

Rejected — increases complexity without benefit.

Filter at parse time

Rejected — less clear separation of responsibilities.

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Notes

This decision does not prevent future support for bitmap fonts, but such support would require a separate data model and rendering path.