docs(pdftract-3qz): add verification note for Phase 2.1 Font Type Detection coordinator
All 5 child beads completed: - pdftract-3uq: Font subtype classifier and BaseFont prefix stripper - pdftract-juc: Standard 14 font registry with hardcoded metrics - pdftract-6ah: Embedded font program loader (ttf-parser/owned_ttf_parser) - pdftract-cv4: Type 0 composite font + descendant CIDFont loader - pdftract-5sh: CIDToGIDMap resolver (Identity and stream forms) 77 font module tests pass. Acceptance criteria: - PASS: All children closed - PASS: Classifier returns all 8 FontKind variants - PASS: Subset prefix stripping works correctly - PASS: CIDToGIDMap Identity and stream forms verified - PASS: No unwrap/expect on resource dict access Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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notes/pdftract-3qz.md
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notes/pdftract-3qz.md
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# pdftract-3qz: Phase 2.1 Font Type Detection (coordinator)
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## Summary
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Coordinator for sub-phase 2.1: Font Type Detection. All 5 child beads completed successfully, delivering a comprehensive font module that can classify, load, and provide metrics for all PDF font types.
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## Children Completed
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| Bead ID | Title | Commit | Verification Note |
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|---------|-------|--------|-------------------|
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| pdftract-3uq | Font subtype classifier and BaseFont prefix stripper | 46c515e | notes/pdftract-3uq.md |
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| pdftract-juc | Standard 14 font registry with hardcoded metrics | 7429a67 | (included below) |
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| pdftract-6ah | Embedded font program loader (ttf-parser/owned_ttf_parser) | ffaaf69 | notes/pdftract-6ah.md |
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| pdftract-cv4 | Type 0 composite font + descendant CIDFont loader | 5e2390f | notes/pdftract-cv4.md |
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| pdftract-5sh | CIDToGIDMap resolver (Identity and stream forms) | 03aa4da | notes/pdftract-5sh.md |
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## Acceptance Criteria Status
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| Criterion | Status |
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|-----------|--------|
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| All children closed | PASS - All 5 child beads closed |
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| Classifier returns one of {Type1, Type1Std14, TrueType, Type0, CIDFontType0, CIDFontType2, Type3, OpenTypeCFF} | PASS |
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| Subset prefix `ABCDEF+Times-Roman` strips to `Times-Roman` for Std-14 lookup | PASS |
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| CIDFontType2 with `/CIDToGIDMap /Identity`: GID == CID | PASS |
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| CIDFontType2 with stream CIDToGIDMap: 2-byte big-endian decode verified | PASS |
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| Module unit tests in `crates/pdftract-core/src/font/` pass | PASS - 77 tests |
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| No unwrap/expect on resource dict access | PASS - uses `.and_then()` and defaults |
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## Module Structure
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```
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crates/pdftract-core/src/font/
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├── mod.rs # FontKind enum, classify_font(), strip_subset_prefix()
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├── std14.rs # Standard 14 font metrics registry (build.rs generated)
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├── embedded.rs # EmbeddedFont, FontMetrics, OpenTypeMetrics, EmptyFontMetrics
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└── type0.rs # Type0Font, DescendantCIDFont, CIDToGIDMap, /W array parsing
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```
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## Test Results
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```
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test result: ok. 77 passed; 0 failed; 0 ignored
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```
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All font module tests pass, covering:
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- Font classification (Type1, Type1Std14, TrueType, Type0, CIDFontType0, CIDFontType2, Type3, OpenTypeCFF)
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- Subset prefix stripping (valid, invalid, edge cases)
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- Standard 14 font detection
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- Type0 composite font loading
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- CIDToGIDMap resolution (Identity and stream forms)
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- /W array parsing (per-CID and range forms)
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- Embedded font program loading (TrueType, OpenType CFF)
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## Child Bead Summaries
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### pdftract-3uq: Font subtype classifier and BaseFont prefix stripper
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- Implemented `FontKind` enum with all 8 PDF font types
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- `strip_subset_prefix()` - validates exactly 6 ASCII uppercase + `+`
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- `classify_font()` - reads `/Subtype`, `/BaseFont`, descendant CIDFont, FontDescriptor
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- 21 unit tests covering all branches
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### pdftract-juc: Standard 14 font registry with hardcoded metrics
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- `build.rs` generates compile-time metrics from AFM-derived JSON
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- `Std14Metrics` struct with widths, ascent, descent, italic_angle, font_bbox
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- `get_std14_metrics()` lookup by canonical name (post-prefix-strip)
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- Symbol/ZapfDingbats use distinct encodings (SymbolEncoding, ZapfDingbatsEncoding)
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- Binary footprint: ~20 KB generated source, ~8 KB data (well under 60 KB limit)
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### pdftract-6ah: Embedded font program loader
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- `EmbeddedFont` wrapping `owned_ttf_parser::OwnedFace`
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- `FontMetrics` trait with `glyph_id_for()`, `advance()`, `bbox()`
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- `EmptyFontMetrics` fallback for corrupt/missing font programs
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- Graceful handling of subset fonts (unmapped chars return None)
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- Diagnostic `FONT_PARSE_FAILED` for corrupt programs
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### pdftract-cv4: Type 0 composite font + descendant CIDFont loader
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- `Type0Font` with descendant `DescendantCIDFont`
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- `/DW` default width parsing (default 1000)
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- `/W` array parsing (per-CID `[c [w1 w2 ...]]` and range `[cfirst clast w]`)
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- Sparse `BTreeMap<u32, u16>` storage for CID widths
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- CIDFontType0 (CFF) vs CIDFontType2 (TrueType) detection
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### pdftract-5sh: CIDToGIDMap resolver
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- `CidToGidMap::{Identity, Array(Box<[u16]>)}` enum
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- Identity short-circuit (zero allocation, GID == CID)
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- Stream form: 2-byte big-endian u16 array indexed by CID
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- Diagnostic `CIDTOGIDMAP_TRUNCATED` for odd-byte-count input
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- Out-of-range CID returns GID 0 (notdef glyph)
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## Integration Points
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This module delivers the `Font` value needed by:
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- **Phase 2.2**: Encoding resolution (ToUnicode, differences, AGL fallback)
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- **Phase 2.3**: CJK CMap parsing and CID-to-Unicode mapping
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- **Phase 2.4**: Type3 font content stream execution
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- **Phase 3**: Content stream execution (Tj, TJ, BT/ET operators)
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## Files Modified/Created
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**Created:**
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- `crates/pdftract-core/src/font/mod.rs`
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- `crates/pdftract-core/src/font/std14.rs`
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- `crates/pdftract-core/src/font/embedded.rs`
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- `crates/pdftract-core/src/font/type0.rs`
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- `crates/pdftract-core/build.rs`
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- `crates/pdftract-core/build/std14-metrics.json`
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- `crates/pdftract-core/build/generate_std14_metrics.py`
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- `crates/pdftract-core/build/fix_std14_weights.py`
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**Modified:**
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- `crates/pdftract-core/src/lib.rs` - added `pub mod font;`
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- `crates/pdftract-core/src/diagnostics.rs` - added `FONT_PARSE_FAILED`, `CIDTOGIDMAP_TRUNCATED`
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- `.gitignore` - added `!/crates/pdftract-core/build/` exceptions
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## Commits Referenced
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- `46c515e` feat(pdftract-3uq): add font type classifier and subset prefix stripper
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- `7429a67` feat(pdftract-juc): implement Standard 14 font metrics registry
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- `ffaaf69` feat(pdftract-6ah): implement embedded font program loader
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- `5e2390f` feat(pdftract-cv4): Type 0 composite font + descendant CIDFont loader
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- `03aa4da` feat(pdftract-5sh): CIDToGIDMap resolver for CIDFontType2
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- `075de55` docs(pdftract-cv4): add verification note
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- `b7392f1` docs(pdftract-6ah): add verification note
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## Notes
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- All child beads have verification notes in `notes/` directory
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- Type3 font `/CharProcs` execution deferred to Phase 2.4 (as planned)
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- OpenType CFF uses same `owned_ttf_parser` entrypoint as TrueType (CFF support via `opentype-layout` feature)
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- The classifier handles indirect references gracefully (returns default, does not crash)
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- Standard 14 fonts may have embedded font programs; registry serves as fallback
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## Ready for Next Phase
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Phase 2.1 is complete. The font module is ready for:
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- **Phase 2.2**: Encoding resolution (ToUnicode, differences, AGL)
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- **Phase 2.3**: CJK CMap parsing
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- **Phase 2.4**: Type3 content stream execution
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