[pentaoa]

Related Issue(s)

Fixes #613. Related: #614.

Motivation and Context

The Stanford CS336 assignment PDF uses NewCM10-Regular, NewCM10-Bold, and NewCM10-Italic for ordinary prose, alongside NewCMMath-Book for mathematics. The precise formula-font patterns currently match every NewCM / NewComputerModern font, so the body text is classified as formulas and protected with placeholders rather than sent for translation.

This also explains why --formular-font-pattern ".*Math.*" cannot work around the issue: the precise built-in pattern returns before the custom pattern is evaluated.

Summary of Changes

In babeldoc/format/pdf/document_il/utils/formular_helper.py, narrow the two precise matches to NewCMMath and NewComputerModernMath. Ordinary NewCM fonts can then follow the existing text/custom-pattern classification, while actual math fonts remain protected.

In tests/test_formular_helper.py, cover regular/bold/italic text, PDF subset prefixes, both math-font spellings, existing Computer Modern/Latin Modern behavior, and page/XObject font scopes. Each case runs with the default formula pattern and the custom .*Math.* pattern.

#614 restores the paragraph bounding-box IoU fallback; this change addresses the separate font-classification cause documented in #613.

PR Type

• 🐛 Bug Fix
• 🧪 Test

Breaking Changes

None.

Testing Instructions

• uv run pytest tests/test_formular_helper.py -q: 24 passed, importing the production module and using the real IL dataclasses.
• uv run ruff check .: passed.
• uv run ruff format --check babeldoc/format/pdf/document_il/utils/formular_helper.py tests/test_formular_helper.py: passed.
• git diff --check: passed.

PyMuPDF inspection of the linked PDF found 97,688 characters in NewCM10-Regular, 6,105 in bold, 884 in italic, and 2,674 in NewCMMath-Book, confirming that the affected font names occur in the reported document.

Contributor Checklist

• Read the contribution guide and kept the patch small.
• Reviewed the changed code.
• Linked the existing issue and added regression tests.
• The changed files follow the project's formatting and lint rules.
• No new dependency or user-facing configuration is introduced.

Limitations

Verification covers offline font classification, font-resource scopes, and the source PDF's font metadata. End-to-end translation through an external service is unverified.

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Summary by cubic

Fixes #613: NewCM text fonts (e.g. NewCM10-Regular) were matched by the precise formula-font pattern and protected as math, preventing translation. The pattern now only matches math fonts (NewCMMath*, NewComputerModernMath*), so ordinary NewCM text fonts classify as text. Adds regression tests for font classification and page/XObject scopes, including the custom .*Math.* pattern.

^{Written for commit 2c86910. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files

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