508ca5d0bb
Implement Phase 4.4 block formation with 5 ordered heuristics for grouping lines into semantic blocks (paragraphs, headings, etc.): 1. Vertical gap > 1.5 * line_height → new block 2. Indent change > 0.03 * column_width → new block 3. Font size change > 1pt → new block 4. Rendering mode change → new block 5. Column boundary → MANDATORY block break Changes: - Extended Line<S> with median_font_size, rendering_mode, column fields - Added LineMetadata trait for abstracting line representations - Added Block<S> and BlockInput<L> structs for block representation - Implemented group_lines_into_blocks() with column-aware sorting All acceptance criteria tests pass (21/21). Closes: pdftract-fy89c
71 lines
2.9 KiB
Markdown
71 lines
2.9 KiB
Markdown
# Verification Note: pdftract-fy89c
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## Bead
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Line-to-block heuristic detector (5 break triggers in order)
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## Implementation
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### Files Modified
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- `crates/pdftract-core/src/layout/line.rs`
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- `crates/pdftract-core/src/layout/mod.rs`
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### Changes Made
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1. **Extended `Line<S>` struct** with new fields:
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- `median_font_size: f32` - median font size of spans in the line
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- `rendering_mode: Option<u32>` - PDF text rendering mode (Tr operator)
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- `column: Option<usize>` - column index assigned by Phase 4.3
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2. **Added `LineMetadata` trait** - abstracts over different line representations for block formation
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3. **Added `Block<S>` struct** - represents a block of text composed of one or more lines
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4. **Added `BlockInput<L>` struct** - internal block representation used during formation
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5. **Implemented `group_lines_into_blocks()` function** with 5 ordered heuristics:
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- **Trigger 1:** Vertical gap > 1.5 * line_height → new block
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- **Trigger 2:** Indent change > 0.03 * column_width → new block
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- **Trigger 3:** Font size change > 1pt → new block
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- **Trigger 4:** Rendering mode change → new block
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- **Trigger 5:** Column boundary → MANDATORY block break
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### Key Implementation Details
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- Lines are sorted by (column ASC, baseline DESC) before processing
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- Column changes are MANDATORY block breaks (per INV in bead description)
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- Line height is computed as baseline-to-baseline distance
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- Vertical gap is computed as previous baseline minus current baseline
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- Block state (avg_x0, median_font_size, rendering_mode, column) is tracked per block
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### Tests Added
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All acceptance criteria tests pass:
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1. `test_five_lines_equal_spacing_one_block` - 5 lines with equal spacing/font → 1 block ✓
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2. `test_thirty_pt_gap_creates_two_blocks` - 30pt gap → 2 blocks ✓
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3. `test_heading_18pt_above_12pt_body_two_blocks` - Font size change (18pt vs 12pt) → 2 blocks ✓
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4. `test_two_column_separate_blocks` - Column boundary → 2 blocks ✓
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5. `test_indented_first_line_new_block` - Indent change (>9pt offset, 300pt column_width) → 2 blocks ✓
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6. `test_rendering_mode_change_creates_new_block` - Rendering mode change → 2 blocks ✓
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7. `test_empty_lines_returns_empty_blocks` - Empty input → empty blocks ✓
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8. `test_single_line_returns_single_block` - Single line → single block ✓
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9. `test_lines_sorted_by_column_then_baseline` - Sorting verification ✓
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## Acceptance Criteria
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- [PASS] 5 lines equal spacing/font: 1 block
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- [PASS] 5 lines, 30pt gap, 5 more: 2 blocks
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- [PASS] Heading 18pt above 12pt body: 2 blocks
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- [PASS] Two-column: lines in col 0 separate from col 1
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- [PASS] Indented first line (>9pt offset, 300pt column_width): NEW BLOCK starts
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## Gates Passed
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- [PASS] `cargo check --all-targets`
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- [PASS] `cargo fmt`
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- [PASS] `cargo test --package pdftract-core --lib layout::line` (21/21 tests passed)
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## References
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- Plan section: Phase 4.4 Heuristics (lines 1694-1699)
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- Bead ID: pdftract-fy89c
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