feat(fonts): honor selected fonts in PDF export

Interpolate the book's body and heading families into the Typst
preamble, title page, cover, and contents. Embed the needed bundled
fonts and load any chosen system fonts (via fontdb) into the Typst
engine so PDF preview and export match the on-screen fonts.

src/components/Dock.tsx

@@ -107,8 +107,8 @@ function PdfDock() {
     clearTimeout(timer.current);
     setBusy(true);
     timer.current = setTimeout(() => {
-      const { source, images } = coverActive ? coverToPdfInputs(book) : chapterToPdfInputs(book, idx);
-      compilePdf(source, images)
+      const { source, images, fonts } = coverActive ? coverToPdfInputs(book) : chapterToPdfInputs(book, idx);
+      compilePdf(source, images, false, fonts)
         .then((bytes) => {
           setPdf(bytes);
           setError(null);

src/export/exporters.ts

@@ -8,8 +8,8 @@ const PDF = [{ name: "PDF", extensions: ["pdf"] }];
 const EPUB = [{ name: "EPUB", extensions: ["epub"] }];
 
 export async function exportPdf(book: Book): Promise<void> {
-  const { source, images } = bookToPdfInputs(book);
-  const bytes = await compilePdf(source, images, true);
+  const { source, images, fonts } = bookToPdfInputs(book);
+  const bytes = await compilePdf(source, images, true, fonts);
   await saveBytes(bytes, `${book.metadata.title || "Untitled"}.pdf`, PDF);
 }
 

src/export/typst.ts

@@ -1,7 +1,18 @@
 import type { JSONContent } from "@tiptap/core";
 import { type Book, type FigurePlacement, type TrimSize, FIGURE_WIDTH, bodyNumber, chapterKind, isResizablePlacement } from "../model/book";
+import { fontFamilyName, fontsUsed } from "../model/fonts";
 import type { ImageInput } from "../ipc";
 
+export interface PdfFonts {
+  bundled: string[];
+  system: string[];
+}
+
+function pdfFonts(book: Book): PdfFonts {
+  const used = fontsUsed(book.settings.fonts);
+  return { bundled: used.bundled.map((f) => f.id), system: used.system };
+}
+
 const TRIM: Record<TrimSize, { w: string; h: string }> = {
   "6x9": { w: "6in", h: "9in" },
   "5.5x8.5": { w: "5.5in", h: "8.5in" },
@@ -104,6 +115,8 @@ function preamble(book: Book): string {
   const trim = TRIM[book.settings.trim];
   const meta = book.metadata;
   const bleed = book.settings.bleed ? "0.125in" : "0in";
+  const body = fontFamilyName(book.settings.fonts.body);
+  const heading = fontFamilyName(book.settings.fonts.heading);
   return `#set document(title: ${str(meta.title || "Untitled")}, author: ${str(meta.author)})
 #set page(
   width: ${trim.w} + ${bleed},
@@ -111,9 +124,9 @@ function preamble(book: Book): string {
   margin: (inside: 0.875in, outside: 0.625in + ${bleed}, top: 0.8in + ${bleed}, bottom: 0.8in + ${bleed}),
   binding: left,
 )
-#set text(font: "Literata", size: 11pt, lang: ${str(meta.language || "en")}, hyphenate: true)
+#set text(font: ${str(body)}, size: 11pt, lang: ${str(meta.language || "en")}, hyphenate: true)
 #set par(justify: true, leading: 0.72em, spacing: 0.72em)
-#show heading: set text(font: "Literata", weight: "medium")
+#show heading: set text(font: ${str(heading)}, weight: "medium")
 #show heading.where(level: 1): set text(size: 22pt)
 #show heading.where(level: 2): set block(above: 1.4em, below: 0.6em)
 #show heading.where(level: 3): set block(above: 1.2em, below: 0.5em)
@@ -125,10 +138,10 @@ function preamble(book: Book): string {
 #let titlepage(title, subtitle, author) = {
   v(2.4in)
   align(center)[
-    #text(font: "Literata", size: 30pt, weight: "medium")[#title]
+    #text(font: ${str(heading)}, size: 30pt, weight: "medium")[#title]
     #if subtitle != "" {
       v(0.6em)
-      text(font: "Literata", size: 15pt, style: "italic", fill: rgb("#6b6458"))[#subtitle]
+      text(font: ${str(body)}, size: 15pt, style: "italic", fill: rgb("#6b6458"))[#subtitle]
     }
     #if author != "" {
       v(1.7em)
@@ -164,7 +177,7 @@ function preamble(book: Book): string {
   set par(justify: false, first-line-indent: 0pt)
   block(below: 2em)[
     #show heading: set block(above: 0pt, below: 0pt)
-    #heading(level: 1, numbering: none, outlined: false, bookmarked: true)[#text(font: "Literata", size: 24pt, weight: "medium")[Contents]]
+    #heading(level: 1, numbering: none, outlined: false, bookmarked: true)[#text(font: ${str(heading)}, size: 24pt, weight: "medium")[Contents]]
   ]
   context {
     let items = query(<chap>).filter(it => it.value.toc != false)
@@ -200,13 +213,15 @@ function imageExtension(dataUrl: string): string {
 function coverBlock(book: Book, coverPath?: string): string {
   const c = book.cover;
   const meta = book.metadata;
+  const body = fontFamilyName(book.settings.fonts.body);
+  const heading = fontFamilyName(book.settings.fonts.heading);
 
   if (c.kind === "image" && coverPath) {
     return `#page(margin: 0pt, numbering: none)[#image(${str(coverPath)}, width: 100%, height: 100%, fit: "cover")]`;
   }
 
   const subtitle = meta.subtitle
-    ? `#v(0.55em)\n  #text(font: "Literata", size: 14pt, style: "italic")[${esc(meta.subtitle)}]`
+    ? `#v(0.55em)\n  #text(font: ${str(body)}, size: 14pt, style: "italic")[${esc(meta.subtitle)}]`
     : "";
   const author = meta.author
     ? `#v(1fr)\n  #text(font: "Hanken Grotesk", size: 11pt, weight: "semibold", tracking: 0.24em)[#upper[${esc(meta.author)}]]\n  #v(0.55in)`
@@ -216,7 +231,7 @@ function coverBlock(book: Book, coverPath?: string): string {
   #set align(center)
   #set text(fill: rgb(${str(c.ink)}))
   #v(1fr)
-  #text(font: "Literata", size: 30pt, weight: "medium")[${esc(meta.title || "Untitled")}]
+  #text(font: ${str(heading)}, size: 30pt, weight: "medium")[${esc(meta.title || "Untitled")}]
   #v(0.5em)
   #line(length: 16%, stroke: 0.6pt + rgb(${str(c.ink)}))
   ${subtitle}
@@ -334,16 +349,16 @@ export function bookToTypst(book: Book, paths: Map<string, string> = new Map(),
   return `${preamble(book)}\n\n${cover}\n\n${front}\n\n${body}\n`;
 }
 
-export function bookToPdfInputs(book: Book): { source: string; images: ImageInput[] } {
+export function bookToPdfInputs(book: Book): { source: string; images: ImageInput[]; fonts: PdfFonts } {
   const { images, paths } = extractImages(book);
   const coverPath = pushCoverImage(book, images);
-  return { source: bookToTypst(book, paths, coverPath), images };
+  return { source: bookToTypst(book, paths, coverPath), images, fonts: pdfFonts(book) };
 }
 
-export function coverToPdfInputs(book: Book): { source: string; images: ImageInput[] } {
+export function coverToPdfInputs(book: Book): { source: string; images: ImageInput[]; fonts: PdfFonts } {
   const images: ImageInput[] = [];
   const coverPath = pushCoverImage(book, images);
-  return { source: `${preamble(book)}\n\n${coverBlock(book, coverPath)}\n`, images };
+  return { source: `${preamble(book)}\n\n${coverBlock(book, coverPath)}\n`, images, fonts: pdfFonts(book) };
 }
 
 function chapterToTypst(book: Book, index: number, paths: Map<string, string>): string {
@@ -358,8 +373,8 @@ ${chapterBody(book.chapters[index].content, paths)}
 `;
 }
 
-export function chapterToPdfInputs(book: Book, index: number): { source: string; images: ImageInput[] } {
+export function chapterToPdfInputs(book: Book, index: number): { source: string; images: ImageInput[]; fonts: PdfFonts } {
   const chapter = book.chapters[index];
   const { images, paths } = collectImages([chapter.content]);
-  return { source: chapterToTypst(book, index, paths), images };
+  return { source: chapterToTypst(book, index, paths), images, fonts: pdfFonts(book) };
 }

src/ipc.ts

@@ -7,12 +7,24 @@ export interface ImageInput {
   data: string;
 }
 
+export interface PdfFonts {
+  bundled: string[];
+  system: string[];
+}
+
 export async function compilePdf(
   source: string,
   images: ImageInput[] = [],
   emitWarnings = false,
+  fonts: PdfFonts = { bundled: [], system: [] },
 ): Promise<Uint8Array> {
-  const buffer = await invoke<ArrayBuffer>("compile_pdf", { source, images, emitWarnings });
+  const buffer = await invoke<ArrayBuffer>("compile_pdf", {
+    source,
+    images,
+    emitWarnings,
+    bundledFonts: fonts.bundled,
+    systemFonts: fonts.system,
+  });
   return new Uint8Array(buffer);
 }