Skip to content
MDI

Rendering model and the Chromium/PDF boundary

Prerequisites: Document IR and Export profiles.

One semantic source, two layers of settings

Section titled “One semantic source, two layers of settings”

Rust owns the .mdi parse, diagnostic codes and UTF-8 spans, and semantic HTML/baseline EPUB/DOCX/TXT output. It is the authority for ruby, tate-chu-yoko, no-break, kerning, blank paragraphs, page breaks, and all other MDI meaning.

Publication settings are deliberately separate. EPUB/DOCX adapters apply metadata, chapters, typography, page setup, and numbering to that already-parsed IR. A host applies browser/PDF settings such as Chromium location and application UI preferences. This avoids putting platform-specific print policy into the parser.

Configured publication exports require one explicit layout.system. japanese-publisher is the strict Japanese book contract: horizontal pages use Shirokuban, 10 pt Mincho, mirrored spreads, left binding, and 27×26; vertical pages use the A4-landscape novel manuscript, mirrored spreads, right binding, and 40×30. word is intentionally incompatible: A4, 25.4 mm on all four sides, no mirroring, and flowing typographic layout; it rejects strict.

OutputBaseline APIConfigured route
HTMLrenderHtml(source){ bodyOnly: true }, or renderHtmlWithDiagnostics for output + headings/spans.
TXTrenderTextFormat(source, format, indentPrefix)caller supplies text indentation.
EPUBrenderEpub(source)await renderEpub(source, { profile, cover }) or aliases such as title, chapterSplitLevel, and coverImage.
DOCXrenderDocx(source)await renderDocx(source, profile) with metadata, page, type, and page-number values.
PDF—@illusions-lab/mdi/node hands Rust HTML and an ExportProfile to a Chromium-capable host.

Diagnostics, headings, and semantic HTML

Section titled “Diagnostics, headings, and semantic HTML”

Call parse(source) or prepareRender(source) before offering export when the UI must display warnings. Its document preserves spans and diagnostics; source errors do not become exceptions merely because an export can fall back to literal text. renderHtmlWithDiagnostics(source, options) retains the same information with the HTML plus source-order headings. The renderer cannot yet take a serialized IR handle, so this helper validates and renders from the same source in sequence rather than inventing a second parser.

HTML is semantic and stable: renderHtml returns a complete page including MDI CSS, while bodyOnly returns only <body> contents for an app shell. Ruby uses <ruby>, <rt>, and <rp>; MDI extensions have predictable mdi-* classes for host styling.

EPUB and DOCX

Section titled “EPUB and DOCX”

The single-argument calls are synchronous Rust baseline exports: useful when front matter is enough and no publication profile is required. The configured calls are asynchronous because the package structurally converts the Rust IR to the EPUB/DOCX publication adapters — MDI source is not reparsed in JavaScript.

Configured EPUB accepts title/author/publisher/language/date/identifier, vertical writing, font family, text indent, h1/h2/h3/none chapter splitting, and a JPEG/PNG cover. Configured DOCX accepts metadata; page size, orientation and four margins; writing direction, font family, font size, line spacing and indent; and page-number visibility, position and simple/dash/fraction format.

DOCX maps page breaks, writing direction, ordinary paragraphs, and available inline/run formatting to OOXML. Its ruby, tate-chu-yoko, kinsoku/no-break, kerning, and forced-blank behavior is necessarily an OOXML approximation, not a claim of browser-identical typography. Verify a target reader when those features determine layout.

The Chromium/PDF boundary

Section titled “The Chromium/PDF boundary”

preparePdfExport(source, profile) in @illusions-lab/mdi/node returns Rust-produced HTML, the profile, and front-matter writing direction. Electron can print that request through its own BrowserWindow. renderPdfWithChromium(source, profile) instead loads the optional, separately installable @illusions-lab/mdi-to-pdf Node adapter (Playwright) unless you pass an Electron-compatible { renderHtmlToPdf } adapter.

The PDF adapter owns Chromium execution and applies paper size, landscape, margins, vertical/horizontal flow, font family/size/line spacing, characters-per-line, lines-per-page, first-line indentation, and page numbers. Browser WASM cannot spawn Chromium; browser code should prepare the request and send it to a Node, Electron, Tauri, or CLI host. Chromium receives completed HTML/CSS, never .mdi source, so it cannot change MDI syntax meaning.

Next steps

Section titled “Next steps”