Steffen Becker
1a1505071c
A second copy of a family LibreOffice bundles makes its render non-deterministic: it resolves the same family to either file per run — the PDF names them Carlito and Carlito-Regular — and their vertical metrics differ, so a page led by a large-font heading lands 1.85mm lower on some runs. Measured 5/5 identical once the duplicates were gone, against a 2-of-4 flip before, and one fixture's count swinging 21↔62 with no code change. README now says to install only what the local LibreOffice does not already ship. Also skips the `~$name` lock file a word processor leaves beside a fixture it has open, which the corpus was picking up as a document.
94 lines
4.3 KiB
Markdown
94 lines
4.3 KiB
Markdown
# Render parity
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Opens the same document in **LibreOffice** and in **the editor**, then compares the
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resulting text layout. Everything else in `tests/` compares documents at the model
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level (JSON → export → import); this leg is the only one that checks what a page
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actually looks like.
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```bash
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npm run test:parity:fixtures # (re)generate the baseline .docx corpus
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npm run test:parity # whole corpus
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npm run test:parity -- path/to/file.docx --json report.json
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```
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Exit code 1 when any document differs. `--json` also dumps both sides' lines
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(`y`, `x`, `x2` in mm, per page) — that dump is what you diagnose from.
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## How it compares
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| | reference | editor |
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|---|---|---|
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| render | `soffice --convert-to pdf` | Playwright Chromium, real app, real file input |
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| read | `pdftotext -bbox-layout` (word boxes, pt) | `Range.getClientRects()` (word boxes, px) |
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Both sides are normalized to mm from the top-left of each page, grouped into lines,
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and compared as: page count → line count → line text → line position. Comparison is
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whitespace-insensitive, because the spell-check decorations split text nodes
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mid-word and the two engines needn't agree on word boundaries — only on what sits
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on a line.
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Reported differences are `pageCount`, `lineCount`, `lineBreak` (same line, different
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words) and `position` (same words, off by more than `POS_TOL_MM`). Comparison of a
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page stops at the first line-level divergence, since everything after it is noise.
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## Prerequisites
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```bash
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apt-get install -y --no-install-recommends libreoffice-writer poppler-utils
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npm install --no-save playwright-core && npx playwright-core install chromium
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cp src/assets/fonts/*.ttf /usr/local/share/fonts/ && fc-cache -f
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```
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**The font step is not optional.** LibreOffice renders with system fonts; without
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the repo's own TTFs installed it substitutes DejaVu for Liberation Serif and every
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line breaks differently for a reason that is not a bug. With them, both engines
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resolve Times New Roman → Liberation Serif, Arial → Liberation Sans, Calibri →
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Carlito, Cambria → Caladea — the same files the editor bundles.
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**But install only what LibreOffice does not already ship.** A second copy of a
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family it bundles makes its render *non-deterministic*: it picks between the two
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files per run — measured as `Carlito` against `Carlito-Regular` in the PDF's font
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list — and their vertical metrics differ, so a page carrying a large-font heading
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lands 1.85mm lower on some runs and a fixture's issue count swings by 40. The
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browser side never needs the install: the app `@font-face`s its own copies. On a
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macOS install `/Applications/LibreOffice.app/Contents/Resources/fonts/truetype/`
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already holds Carlito, Caladea and Liberation, so **skip the `cp` there entirely**;
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check any other platform with `fc-list | grep -ci carlito` before copying.
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The runner starts `npm run dev` on port 5199 itself if nothing answers there.
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## Fixtures
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`make-fixtures.mjs` authors the baseline corpus with the `docx` lib **directly**,
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not through `src/lib/export/docx.ts` — otherwise the corpus would test our exporter
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against itself. Real-world `.docx`/`.odt` files dropped into `fixtures/` are picked
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up too. The directory is gitignored: run the generator once, and keep whatever
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real-world files you test against local.
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## Names stay local
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A real-world document's name goes in no file, and a commit message names no document at
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all — write the rule that changed and what it measured. `FINDINGS.md` is gitignored for
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that reason.
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Only this harness reads `fixtures/`. The directory is gitignored, so a `tests/unit/` test
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reading it fails with `ENOENT` on a fresh clone; it zips its own document instead
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(`docx-onoff.test.ts` — both importers take a `Uint8Array`, not a path). CI greps for the
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read.
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## Prerequisites, part two: Calibri Light
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Word's default theme heading font. LibreOffice's substitution table knows Calibri but
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not Calibri Light, so without an alias it falls to fontconfig's generic — DejaVu Serif,
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a serif heading nothing else renders. Word substitutes plain Calibri, and so does the
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editor (`global.css`), so give LibreOffice the same answer:
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```xml
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<!-- /etc/fonts/conf.d/30-calibri-light.conf, then fc-cache -f -->
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<match target="pattern">
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<test name="family"><string>Calibri Light</string></test>
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<edit name="family" mode="prepend" binding="strong"><string>Carlito</string></edit>
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</match>
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```
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