All 7 sub-phases (4.1-4.7) are now fully implemented:
- 4.1 Glyph to Span Merging: grouping consecutive glyphs into spans
- 4.2 Line Formation: baseline clustering and direction detection
- 4.3 Column Detection: histogram-based gap analysis
- 4.4 Block Formation: paragraph/heading/list/table/caption/figure/code classification
- 4.5 Reading Order: XY-cut algorithm with Docstrum fallback
- 4.6 Output Serialization: plain text projection with configurable filters
- 4.7 Text Readability: composite scoring and correction pipeline
Closes pdftract-4k1x4. Verification: notes/pdftract-4k1x4.md.
Changes:
- extract.rs: integrate Phase 4 modules into main pipeline
- layout/correction.rs: expand correction pipeline with 2048 lines of tests
- layout/readability.rs: five-signal scoring with char-weighted median
- text.rs: plain text serialization with page breaks and filters
- span/mod.rs: Span struct with flags and confidence tracking
- layout/columns.rs: column assignment to lines and spans
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
The indent trigger was using .abs() which fired on both increased indent
(non-indented → indented) AND decreased indent (indented → non-indented).
This caused drop-cap style paragraphs (indented first line, flush-left
continuation) to incorrectly split into two blocks.
Per plan Phase 4.4 heuristic #2, indent change should only trigger when the
current line is MORE indented (to the right, larger x0) than the block
average - i.e., a new paragraph starting after non-indented text. It should
NOT trigger for decreased indent (first line indented, rest flush-left).
Fix: Remove .abs() and only check if line_x0 - block_avg_x0 > threshold.
Tests:
- test_indented_first_line_new_block: PASS (non-indented → indented splits)
- test_indented_first_line_of_paragraph_not_split: PASS (drop cap stays together)
- All 179 line module tests: PASS
