jedarden 20d3b10ed5 test(bf-6afe3): add test demonstrating unmapped glyph skip behavior

- Add test_unmapped_glyph_skip_behavior test to encoding.rs
- Verifies unmapped glyphs (.notdef) are skipped during CMAP generation
- Verifies mapped glyphs (A, space, B) appear correctly
- Test is simple, readable, and clearly documents the behavior

Closes bf-6afe3. Verification: notes/bf-6afe3.md. Tests: PASS (all 27 encoding tests pass).

2026-07-06 13:43:59 -04:00

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Verification Note: bf-6afe3 - Test demonstrating unmapped glyph skip behavior

Summary

Added a focused test (test_unmapped_glyph_skip_behavior) that verifies unmapped glyphs are correctly skipped during CMAP generation while normal mapped glyphs are preserved.

Acceptance Criteria

✅ PASS: Test exists and passes

Test added to crates/pdftract-core/src/font/encoding.rs (lines 873-902)
Test passes: cargo test -p pdftract-core --lib encoding::tests::test_unmapped_glyph_skip_behavior
All 27 encoding tests pass

✅ PASS: Test demonstrates unmapped glyphs are skipped

Test verifies that .notdef at codes 32 and 67 does NOT appear in the overlay
Uses assert_eq!(overlay.get(32), None) and assert_eq!(overlay.get(67), None) with clear error messages

✅ PASS: Test demonstrates mapped glyphs still appear

Test verifies that normal glyphs A, space, and B DO appear in the overlay at codes 65, 66, and 68
Uses assert_eq!(overlay.get(65), Some(Arc::from("A"))) and similar assertions

✅ PASS: Simple, readable test case

Test is self-contained with clear documentation comment explaining the behavior
Uses descriptive variable names and assertion messages
Covers multiple unmapped glyphs and multiple mapped glyphs in one test

Implementation Details

The test creates a /Differences array with mixed glyphs:

Code 32: .notdef (unmapped, should skip)
Code 65: A (normal, should appear)
Code 66: space (normal, should appear)
Code 67: .notdef (unmapped, should skip)
Code 68: B (normal, should appear)

Then verifies:

Unmapped glyphs (.notdef) return None from overlay.get()
Mapped glyphs return Some(name) from overlay.get()
Final overlay has exactly 3 entries (not 5)
No diagnostics are emitted for normal skip behavior

Files Modified

crates/pdftract-core/src/font/encoding.rs - Added test (lines 873-902)

Verification Commands

# Run the new test
cargo test -p pdftract-core --lib encoding::tests::test_unmapped_glyph_skip_behavior

# Run all encoding tests
cargo test -p pdftract-core --lib encoding::tests

The skip logic is in DifferencesOverlay::parse() at lines 221-231 in encoding.rs
The is_unmapped_glyph_name() method at lines 274-282 checks against unmapped_glyph_names set
Default unmapped glyphs include .notdef and others from UNMAPPED_GLYPH_NAMES

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