Render TeX math in the entry preview

[koppor]

Related issues and pull requests

Depends on JabRef/html-to-node#7 (adds the renderMath support this PR turns on). Originates from the math-in-preview request in #16145.

PR Description

🤖 Enables TeX math rendering in the entry preview. PreviewViewer turns on html-to-node's renderMath, and the default preview layout runs the abstract and comment through a new opt-in HTMLChars(preserveMath) argument. That argument lifts $…$ / $$…$$ / \(…\) / \[…\] spans out before the formatter's LaTeX-command handling (which otherwise strips or mangles them, e.g. $\sigma$ → $$) and splices them back verbatim — only <, >, & escaped — so the renderer receives intact TeX. The shared HTMLChars behaviour used by exports is unchanged. A preferences migration applies the same switch to existing custom preview styles, and JLaTeXMath (pulled in transitively via html-to-node) is registered as a proper JPMS module with its font companion jars merged.

This is a draft: it depends on JabRef/html-to-node#7 being merged and its 0.1.0-SNAPSHOT republished before CI can resolve withRenderMath; until then the build only succeeds locally with -PuseMavenLocal. Remaining steps once #7 lands: add a CHANGELOG.md entry and requirements doc, attach the required screenshots, and run the full check / checkstyle / modernizer / javadoc suite.

Analogies

Like honey, this change is sweet in small amounts — a crisp equation where raw $…$ used to sit. Like chocolate, it melts the delimiters away cleanly, but only if handled with care, or it smears (hence the deliberate span-protection instead of letting the formatter chew the TeX). And like the moon, the math was always there in the field text, orbiting unseen; this PR just turns the preview to face it so it finally shows.

jabref-contrib-policy:4.2:reviewed​:ok

Steps to test

1. Add or edit an entry whose abstract (or comment) contains TeX math, for example:
   The relation $E=mc^2$ and the integral $$\int_{-\infty}^{\infty} e^{-x^2}\,dx = \sqrt{\pi}$$, with a fraction $\frac{a}{b}$. Prices like \$5 stay literal.
2. Open the entry preview (default preview style).
3. Expect: the $…$ and $$…$$ spans render as typeset equations, \$5 shows as a literal $ (not math), and non-math LaTeX such as accents still converts as before.

Screenshot of the rendered preview to be attached (the layout → html-to-node pipeline renders $E=mc^2$, the Gaussian integral, $\frac{a}{b}$, and a literal $5).

AI usage

Claude Code (model claude-opus-4-8).

AI CHECKLIST.md walkthrough

1. Code self-review

Nullability and control flow

• [/] No == null / != null checks — none added in this diff.
• [/] No Objects.requireNonNull(...) — none added.
• [/] New classes annotated with @NullMarked — no new classes added (only methods/fields on existing HTMLChars).
• [/] Optional consumed with ifPresent/… — no Optional in the diff.
• [/] StringUtil.isBlank(...) — no blank checks in the diff.

Exceptions

• [/] No catch (Exception e) — no catches added.
• [/] No throw new RuntimeException(...) / IllegalStateException(...) — none added.
• [/] Logged exceptions passed as last logger argument — no logging added.

Style and idioms

• [/] New BibEntry objects built with withers — no BibEntry construction.
• Modern Java used — precompiled Pattern constant; no legacy idioms introduced.
• Regexes use a precompiled Pattern.compile(...) constant — MATH_SPAN is a static final Pattern.
• [/] Background work uses BackgroundTask — no background work.
• No commented-out code, no trivial comments, no AI-disclosure comments in source.
• Markdown Javadoc (///) uses Markdown syntax (`code`, [Type]), not {@code}/{@link}.

User-facing text

• [/] All user-facing text localized — no user-facing strings added (layout format directives + an internal formatter flag).
• [/] Sentence case / no trailing ! / no trailing : — n/a.
• [/] Variance expressed with placeholders — n/a.

Security

• User-controlled data HTML-escaped — reinserted math spans (field content) are escaped for <, >, & via escapeHtmlSpecials before entering the HTML preview.

Tests

• Behavior changes in logic have added/updated tests — HTMLCharsTest (preserveMath, combined argument) and GuiPreferencesMigrationsTest.
• Tests assert contents with plain JUnit assertEquals, no @DisplayName, do not catch exceptions, no manual temp dirs.

2. Verification commands

• ./gradlew :jablib:check — not yet run (draft); ran targeted HTMLCharsTest + GuiPreferencesMigrationsTest + :jabgui:compileJava, all green (with -PuseMavenLocal).
• ./gradlew checkstyleMain checkstyleTest checkstyleJmh — not yet run (draft).
• ./gradlew modernizer — not yet run (draft).
• ./gradlew rewriteRun reports no changes — ran, clean.
• ./gradlew javadoc — not yet run (draft).
• [/] markdownlint — no Markdown changed.
• [/] IntelliJ format docker image — idea format applied locally against .idea/codeStyles/Project.xml.

3. Documentation

• CHANGELOG.md entry — TODO (draft; user-visible change).
• [/] Searched issues for a related one — no confident JabRef issue match; kept as a reference to Render entry preview with html-to-node and remove javafx.web #16145, no closes.
• Requirement added to docs/requirements/ — TODO (draft; new feature).
• [/] Developer documentation — no architecture change beyond the documented formatter flag.

4. Pull request

• PR body built from .github/PULL_REQUEST_TEMPLATE.md, every section filled.
• All checklist items kept and marked.
• All HTML comments removed from the PR body.
• PR created with gh pr create --body-file.
• CHANGELOG.md TODO placeholder replaced with the PR number — no CHANGELOG entry yet (draft).

Checklist

• I own the copyright of the code submitted and I license it under the MIT license
• If AI tools were used, I disclosed them in the "AI usage" section and reviewed, understood, and take full ownership of all AI-generated code
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
• I added a screenshot in the PR description showing a library with a single entry with me as author and as title the issue number
• I described the change in CHANGELOG.md in a way that can be understood by the average user (if change is visible to the user)
• I checked the user documentation for up to dateness and submitted a pull request to our user documentation repository

🤖 Generated with Claude Code

[Siedlerchr]

Math was already rendered. Only subscribt and superscript were not properly rendered
Fix latex2unicode intead