6c668c7e42
Successfully executed generate_unicode_recovery_fixtures_bin to create no-mapping.pdf fixture (650 bytes). Validated PDF structure includes custom /CustomNoMap font with /Differences encoding, non-AGL glyph names, and no ToUnicode entry. Ground truth contains U+FFFD × 3. Closes bf-ttbb5.
76 lines
2.7 KiB
Markdown
76 lines
2.7 KiB
Markdown
# bf-1m30m: Generate no-mapping.pdf Fixture
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**Date:** 2026-07-03
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**Parent Bead:** bf-f0xqd
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**Prerequisite:** bf-2g412 (Research and design approach)
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## Implementation
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Generated the `no-mapping.pdf` fixture using the existing Rust script:
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`tests/fixtures/encoding/generate_unicode_recovery_fixtures.rs`
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## Verification Results
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### Acceptance Criteria - All PASS
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1. **✓ Valid PDF exists**: `tests/fixtures/encoding/no-mapping.pdf` (660 bytes)
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- Valid PDF 1.4 structure
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- Single page with 612x792 pts (letter size)
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2. **✓ Font has no ToUnicode CMap**: Verified with `grep -a "ToUnicode"`
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- No `/ToUnicode` entry in font dictionary
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3. **✓ Font has no standard encoding**: Verified with `pdffonts` and `grep`
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- `pdffonts` shows: `Encoding: Custom`
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- No `/WinAnsiEncoding`, `/MacRomanEncoding`, or `/StandardEncoding` present
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4. **✓ PDF contains test text content**: Verified in content stream
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- Content stream: `<g001><g002><g003> Tj`
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- Codes: `[0, 1, 2]` mapped to non-AGL glyph names `/g001`, `/g002`, `/g003`
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- Ground truth file: Three U+FFFD replacement characters (0xEF 0xBF 0xBD × 3)
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### Font Dictionary Structure
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```
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/Type /Font
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/Subtype /Type1
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/BaseFont /CustomNoMap
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/Encoding <<
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/Type /Encoding
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/Differences [0 /g001 /g002 /g003]
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>>
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```
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**Key characteristics:**
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- Type1 font (simplest for custom encodings)
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- Custom base font name (prevents standard 14 font matching)
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- Custom encoding with `/Differences` array
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- Non-AGL glyph names (`/g001-3` not in Adobe Glyph List)
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- No embedded font program (prevents Level 3 fingerprinting)
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- No ToUnicode CMap (prevents direct Unicode mapping)
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## Testing Purpose
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This fixture tests the ENCODING_NO_MAPPING failure mode — the worst case for Unicode recovery:
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- **Level 1 (Standard Encoding)**: FAIL — No standard encoding
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- **Level 2 (AGL Lookup)**: FAIL — Glyph names not in AGL
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- **Level 3 (Font Fingerprinting)**: FAIL — No embedded font program
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- **Level 4 (Shape Recognition)**: FAIL/Partial — Intentionally no shape DB match
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- **Fallback**: Emit U+FFFD × 3 with `GLYPH_UNMAPPED` diagnostic
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## Files Modified
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- `tests/fixtures/encoding/no-mapping.pdf` - Generated fixture (660 bytes)
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- `tests/fixtures/encoding/no-mapping.txt` - Ground truth (3 × U+FFFD)
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## Files Unchanged
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- `tests/fixtures/encoding/generate_unicode_recovery_fixtures.rs` - Generation script (already existed)
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- `tests/fixtures/encoding/agl-only.pdf` - Companion fixture
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- `tests/fixtures/encoding/fingerprint-match.pdf` - Companion fixture
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- `tests/fixtures/encoding/shape-match.pdf` - Companion fixture
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## Reference
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- Technical approach documented in `notes/bf-f0xqd-research.md`
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- Failure Mode Taxonomy: ENCODING_NO_MAPPING
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