jedarden 51f33b2b67 docs(pdftract-5f92): add verification note for Type3 font loader

Documents the completed Type3 font loader implementation,
acceptance criteria status, and test coverage.

Verification:
- All 13 unit tests pass
- All acceptance criteria PASS
- Commit ece0442 contains the implementation

2026-05-24 01:08:36 -04:00

3.1 KiB

Raw Blame History

Verification Note: pdftract-5f92 - Type 3 Font Loader

Summary

Implemented Type3 font loader in crates/pdftract-core/src/font/type3.rs with complete support for:

/CharProcs (HashMap<Arc, ObjRef> from glyph name to content stream reference)
/FirstChar, /LastChar (character code range)
/Widths array (advance widths in glyph space)
/FontMatrix 3x3 transform (default [0.001 0 0 0.001 0 0])
/Resources (optional resource dictionary for glyph streams)
/Encoding (code -> glyph name mapping)

Implementation

File: crates/pdftract-core/src/font/type3.rs

Struct: Type3Font with all required fields plus diagnostics vector.

Methods:

load(font_dict) - Main entry point for loading Type3 fonts
advance_for(code) - Get advance width for a character code (applies FontMatrix transform)
char_proc(glyph_name) - Get stream reference for a glyph
has_glyph(glyph_name) - Check if glyph exists
glyph_count() - Get number of glyphs

Acceptance Criteria Status

✅ PASS: Valid Type 3 font loads with all fields populated
✅ PASS: /FontMatrix [0.001 0 0 0.001 0 0]: advance for code with width 500 -> 0.5 text-units
✅ PASS: /FontMatrix [1 0 0 1 0 0] (identity): same width 500 -> 500 text-units
✅ PASS: Missing /Widths defaults to all-zero with diagnostic
✅ PASS: Code outside [FirstChar, LastChar] returns advance 0 with no panic

Test Coverage

13 unit tests covering:

test_type3_load_minimal - Basic loading with defaults
test_type3_with_char_procs - CharProcs dictionary parsing
test_advance_for_with_standard_font_matrix - Standard FontMatrix scaling
test_advance_for_with_identity_font_matrix - Identity FontMatrix (no scaling)
test_advance_for_out_of_range - Out-of-range code handling
test_widths_length_mismatch - Widths validation (pad with zeros)
test_widths_too_long - Widths validation (truncate)
test_missing_widths - Default to all-zero with diagnostic
test_missing_char_procs - Empty char_procs map
test_custom_font_matrix - Custom FontMatrix values
test_with_resources - Resources dictionary parsing
test_arbitrary_glyph_names - Non-AGL glyph name support
test_encoding_parse - Encoding parsing integration

All tests pass:

running 13 tests
test result: ok. 13 passed; 0 failed

Critical Considerations Handled

✅ Advance width calculation: Widths[C - FirstChar] * FontMatrix[0]
✅ Widths length mismatch emits TYPE3_WIDTHS_LENGTH_MISMATCH diagnostic and clamps/pads
✅ Empty CharProcs treated as zero-glyph font (malformed but handled)
✅ Arbitrary glyph names supported (not assumed to be AGL names)
✅ FontMatrix default [0.001 0 0 0.001 0 0] applied correctly
✅ Resources optional (defaults to None, page resources used downstream)

Commit

Commit: ece0442 - "feat(pdftract-5f92): implement Type3 font loader"

Integration

Exported from font/mod.rs as pub use type3::Type3Font
Classified by classify_font() as FontKind::Type3
Ready for integration with Phase 2.2 resolver chain for encoding resolution

3.1 KiB Raw Blame History