Word (.docx) documents as sites, via docx-preview

A site whose path is a local .docx renders as pages in the kiosk instead
of Chromium offering a download. kiosk-app/docview.js maps the file URL
to docview.html (alongside slideshow.js, through main.js's new
resolveLocalSite) and pushes the file's bytes into the page from the main
process; the page renders them with docx-preview + jszip, both pure-JS
npm dependencies of kiosk-app (so online installs, Advanced -> Upgrade
and the offline bundle all pick them up - no LibreOffice).

- Scaled to the screen width (capped at 160%), scrolls normally.
- Re-checked every minute; a changed file re-renders from the top.
- Word's Symbol/Wingdings private-use bullet glyphs (U+F0B7 etc.), which
  render blank without Microsoft fonts, are mapped to Unicode (•, ▪, ...).
- Missing/unreadable/oversized (>50 MB) files and a missing library show
  a message instead of a blank page. .doc/.odt aren't supported.

Tested with the real main.js on Electron 44.5.1 under Xvfb + Openbox:
heading, coloured bold run, image, bordered table, bullets and a page
break rendered; wheel scrolling works; replacing the file while running
re-rendered the new document within the refresh. Offline bundle rebuilt
and contains docx-preview and jszip.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Cjz8a58eB5P9sUweqd3NHm

kiosk-app/docview.js

@@ -0,0 +1,82 @@
+// Word document (.docx) support for main.js.
+//
+// A site whose URL is a local .docx file (file:///home/kiosk/docs/menu.docx,
+// entered in the Sites menu or Web UI as /home/kiosk/docs/menu.docx) is
+// rendered with docx-preview (an npm dependency of this app - pure
+// JavaScript, works offline) instead of Chromium offering to download it.
+// main.js swaps the file URL for docview.html via resolveSiteUrl(), then
+// attach() hands the page the file's bytes - the page itself has no
+// filesystem access (contextIsolation, no Node). The file is re-checked
+// every minute and re-rendered if it changed, so replacing the document
+// on disk updates the kiosk without a restart.
+//
+// Only .docx (Word 2007+). Old binary .doc and LibreOffice .odt aren't
+// supported by docx-preview - save those as .docx or PDF.
+
+const fs = require('fs');
+const path = require('path');
+const { fileURLToPath, pathToFileURL } = require('url');
+
+const VIEWER_PAGE = path.join(__dirname, 'docview.html');
+const REFRESH_MS = 60000;
+const MAX_BYTES = 50 * 1024 * 1024;
+
+// The .docx path a site URL points at, or null.
+function docxPath(url) {
+    if (typeof url !== 'string' || !url.startsWith('file://')) return null;
+    let p;
+    try {
+        p = fileURLToPath(url);
+    } catch (e) {
+        return null;
+    }
+    return path.extname(p).toLowerCase() === '.docx' ? p : null;
+}
+
+// What a view should actually load for a configured site URL.
+function resolveSiteUrl(url) {
+    const file = docxPath(url);
+    if (!file) return url;
+    const u = pathToFileURL(VIEWER_PAGE);
+    u.searchParams.set('file', file);
+    return u.href;
+}
+
+function readDoc(file) {
+    try {
+        const st = fs.statSync(file);
+        if (st.size > MAX_BYTES) return { file, error: `Document is too large to show (${Math.round(st.size / 1048576)} MB).` };
+        return { file, mtime: st.mtimeMs, data: fs.readFileSync(file).toString('base64') };
+    } catch (e) {
+        return { file, error: e.code === 'ENOENT' ? `File not found: ${file}` : `Can't read ${file}: ${e.message}` };
+    }
+}
+
+// Feed a view's viewer page the document now and again whenever the file
+// changes. Call once per view; safe on views that never show a document.
+function attach(webContents) {
+    let lastKey = '';
+    const send = (force) => {
+        if (webContents.isDestroyed()) return;
+        const current = webContents.getURL();
+        if (!current.startsWith(pathToFileURL(VIEWER_PAGE).href)) return;
+        const file = new URL(current).searchParams.get('file');
+        if (!file) return;
+        let key;
+        try {
+            const st = fs.statSync(file);
+            key = `${st.mtimeMs}:${st.size}`;
+        } catch (e) {
+            key = 'missing';
+        }
+        if (!force && key === lastKey) return;
+        lastKey = key;
+        webContents.executeJavaScript(`window.kioskDocView&&window.kioskDocView.show(${JSON.stringify(readDoc(file))})`)
+            .catch(() => {});
+    };
+    webContents.on('did-finish-load', () => send(true));
+    const timer = setInterval(() => send(false), REFRESH_MS);
+    webContents.once('destroyed', () => clearInterval(timer));
+}
+
+module.exports = { resolveSiteUrl, docxPath, attach };