jedarden 691ff10066 docs(bf-10vsm): document generator config structure location

- Identified build/unmapped-glyph-names.json as the primary config file
- Documented DifferencesOverlay struct in encoding.rs as the Rust config structure
- Described the build-time generation process via build.rs
- Listed all files involved in the config pipeline
Closes bf-10vsm

2026-07-06 14:38:34 -04:00

2.3 KiB

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bf-10vsm: Generator Config Structure Location

Summary

Found the generator config structure for unmapped glyph names handling.

Config Structure Location

Primary config file: /home/coding/pdftract/build/unmapped-glyph-names.json

Rust config struct: crates/pdftract-core/src/font/encoding.rs - DifferencesOverlay struct

Current Fields and Types

JSON Config Format (`unmapped-glyph-names.json`)

{
  "unmapped_glyph_names": [
    ".notdef",
    ".null",
    "g000",
    "g001",
    // ... more glyph names
  ],
  "description": "...",
  "version": "1.0"
}

Fields:

unmapped_glyph_names - Array of strings (glyph names to skip during CMAP entry creation)
description - String (optional documentation)
version - String (format version identifier)

Rust Struct (`DifferencesOverlay` in `encoding.rs`)

pub struct DifferencesOverlay {
    entries: Vec<(u8, Arc<str>)>,
    unmapped_glyph_names: std::collections::HashSet<String>,
}

Fields:

entries - Sparse list of (code, glyph_name) overrides
unmapped_glyph_names - HashSet of glyph names to skip during CMAP entry creation

Build Process

The config is processed at build time by crates/pdftract-core/build.rs:

Reads build/unmapped-glyph-names.json
Calls generate_unmapped_glyph_names() function (lines 946-1050)
Emits unmapped_glyph_names.rs in OUT_DIR with a UNMAPPED_GLYPH_NAMES static HashSet
This is auto-included by crates/pdftract-core/src/font/unmapped.rs via include!()

Usage

The config is used in DifferencesOverlay::parse() (encoding.rs:190-241) to skip unmapped glyph names when creating CMAP entries. This prevents glyphs like .notdef from appearing in text extraction output.

Files Involved

Config: build/unmapped-glyph-names.json
Build script: crates/pdftract-core/build.rs (lines 946-1050)
Rust struct: crates/pdftract-core/src/font/encoding.rs (lines 128-297)
Auto-generated: target/*/build/*/out/unmapped_glyph_names.rs
Module: crates/pdftract-core/src/font/unmapped.rs

Verification

✅ JSON file exists and is valid
✅ Build script reads and processes the file
✅ Generated code is included in the font::unmapped module
✅ DifferencesOverlay uses the generated UNMAPPED_GLYPH_NAMES set

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