[Yun-0000]

Checklist:

• Documentation has been updated, if necessary.
• Examples have been added, if necessary.
• Tests have been added, if necessary.

See #4995.

The default PDF backend paints non-embedded fonts with host fonts. A host with no match leaves the page image blank, so layout and table detection can drop the text, and nothing said so. This does not make the render independent of the host. It warns once per document when visible text cells contain almost no ink, and the installation guide lists the font packages and DOCLING_PARSE_FALLBACK_FONT.

Review evidence:

Before: get_page_image() on a page whose text cells sit on a blank image logged nothing.
After: the same call logs one warning that names DOCLING_PARSE_FALLBACK_FONT. A second call does not log again. Ink inside the text cells, and a crop, do not warn. A real render of tests/data/pdf/invisible_text_layer.pdf on this host has an ink fraction of 0.25, so it does not warn.

Passed:

• uv run pytest tests/test_docling_parse_missing_font.py on main: 2 failed (test_unpainted_text_warns_once, test_a_crop_does_not_warn_before_the_full_page), 1 passed (test_ink_inside_text_cells_does_not_warn).
• Same file after the change: 3 passed.
• uv run pytest tests/test_backend_docling_parse.py tests/test_docling_parse_missing_font.py: 37 passed.
• make validate: passed.

Failed:

• none after the change.

Not run:

• make test. No PDF reference files were regenerated. This host has DejaVu fonts, so the no-font render itself was not reproduced here.

[github-actions]

✅ DCO Check Passed

Thanks @Yun-0000, all your commits are properly signed off. 🎉

[mergify]

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• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert)(?:\(.+\))?(!)?:

[github-actions]

AI triage (advisory)

Checked commit 3833103aa4. The analysis read the diff only. It did not run code from this pull request.

The PR adds a one-time warning in the docling-parse backend. It fires when get_page_image() returns a full-page image with almost no dark pixels inside the visible text cells, which means no host font painted the text. It also adds a font-install section to the installation guide, a line in the usage skill, and a new test file.

Topic labels added: bug, pdf, pdf parsing, documentation, tests.

CI safety: no concern found. A maintainer must still approve CI.

1 related pull request(s) in the same code

PR	State	Signal	Assessment
#4833	open	changes the same code	related: Both PRs edit docling/backend/docling_parse_backend.py. PR 4833 adds a password-protected PDF error in the load path. This PR adds a font-paint warning in page rendering. The changes do not conflict in purpose.

_{The ai:* labels are advisory. They do not approve CI and they do not add tests:full. A new push runs this check again.}

[github-actions]

AI first review (advisory): no blocker found

This review covers the full diff at 3833103aa4. It read the code and did not run it.

Checked the text ink fraction check, the single warning state per document backend, and the test coverage for blank and drawn pages with no issues found.

_{A maintainer makes the merge decision. This review never approves the pull request.}

[codecov]

Codecov Report

❌ Patch coverage is 81.48148% with 10 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
docling/backend/docling_parse_backend.py	81.48%	5 Missing and 5 partials ⚠️

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