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fix(fonts): CID-as-Unicode passthrough and subscript merging (#8)

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* fix(fonts): CID-as-Unicode passthrough and subscript/superscript merging

Add smart CID-as-Unicode passthrough for Identity-H fonts without
ToUnicode maps. Uses /W array median CID heuristic to distinguish
Unicode-CID PDFs (Chromium-generated) from GID-based subsets.

Add merge_subscript_items() pass that merges small-font items (<75%
of dominant font size, ≤4 chars, tightly adjacent) into parent items.
Fixes chemical formulas (NH3, H2O, KClO3), footnote references, and
subscript notation (vf, Hfg, m3/kg) that were previously orphaned
as separate text items.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(subscripts): restrict merge to purely numeric text only

Tighten subscript merging to only merge items containing ASCII digits
(0-9). This avoids false positives with ordinal indicators (º), letter
subscripts (sol, vf), and small bullet characters (▶) that caused
table restructuring regressions.

Numeric-only keeps the primary wins: chemical formulas (NH3, H2O),
footnote references, and unit notation (m2, m3).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(subscripts): restrict merge to parent text ending with a letter

Only merge numeric subscripts when the parent item's text ends with
an alphabetic character. Prevents false merges like "33" + "1" in
fractions (33 1/3%), table credit numbers after spaces, and footnote
refs after punctuation (land.1 → land. 1). Chemical formulas (NH3,
H2O, KClO3) still merge correctly since parent ends with a letter.

Reduces pdf-eval regressions from 13 to 2 (both are correct reversions
of over-aggressive footnote merging from the prior commit).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Abimael Martell
2026-03-23 09:41:10 -07:00
committed by GitHub
co-authored by Claude Opus 4.6
parent 7f2995ad0c
commit 6c005ef4c2
4 changed files with 339 additions and 24 deletions
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tests/snapshots/thermo-freon12.md
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@@ -48,7 +48,7 @@ l
|Temp|Pressure|Volume||Density|||Enthalpy||Entropy||Temp|
|---|---|---|---|---|---|---|---|---|---|---|---|
|°C|[kPa]|[m Liquid v|/kg] Vapour v|[kg/m3] Liquid d|Vapour d|Liquid H|[kJ/kg] Latent H|Vapour H|[kJ/K-kg] Liquid S|Vapour S|°C|
|°C|[kPa]|[m3/kg] Liquid v|Vapour v|[kg/m3] Liquid d|Vapour d|Liquid H|[kJ/kg] Latent H|Vapour H|[kJ/K-kg] Liquid S|Vapour S|°C|
|-100|1.2|0.0006|10.0000|1679.0|0.100|113.3|192.8|306.1|0.6077|1.7210|-100|
|-99|1.3|0.0006|9.1670|1677.0|0.109|114.1|192.4|306.5|0.6124|1.7170|-99|
|-98|1.4|0.0006|8.4100|1674.0|0.119|115.0|192.0|307.0|0.6171|1.7130|-98|
@@ -104,7 +104,5 @@ l
|-48|43.4|0.0007|0.3499|1539.0|2.858|156.9|173.4|330.3|0.8274|1.5980|-48|
|-47|45.6|0.0007|0.3339|1536.0|2.995|157.8|173.0|330.8|0.8313|1.5960|-47|
**3**
**f g f g f** fg **g f g**