Folder image slideshow sites; Electron 42 -> 44

Slideshow: a site whose path is a local folder (/home/kiosk/photos/, or
any existing directory) plays its images full-screen instead of showing
Chromium's directory listing. kiosk-app/slideshow.js maps the folder URL
to slideshow.html (resolveSiteUrl - used where main.js loads a view and
where attachView re-checks the configured URL) and pushes the image list
into the page from the main process (the page has no fs access), re-read
every minute so added/removed images show up without a restart. Natural
file-name order, crossfade, letterboxed by default; optional
slideshow.json in the folder: interval, shuffle, fit, transition,
recursive. provision_install_app already copies kiosk-app/*.js/*.html,
so new installs and Advanced -> Upgrade pick it up.

Electron: ^42.0.0 -> ^44.0.0. Electron supports the latest three majors
(44/43/42), so 42 drops out when 45 ships. Checked the 43/44 breaking
changes against kiosk-app: nothing it uses changed (no clipboard,
safeStorage, net.request, utilityProcess; BrowserView is deprecated but
still present through 46). The offline bundle builder now retries
Electron's install.js download, which crashes outright if a large
download is cut off mid-stream.

Tested with the real main.js on Electron 44.5.1 under Xvfb + Openbox:
slideshow fills the screen, cycles in order (01, 02, 10) skipping a .txt
file, honours slideshow.json, and an image added mid-run joined the
rotation after the refresh. Offline bundle rebuilt with Electron 44.5.1.

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

kiosk-app/slideshow.js

@@ -0,0 +1,127 @@
+// Folder slideshow support for main.js.
+//
+// A site whose URL is a local folder (file:///home/kiosk/photos, entered
+// in the Sites menu or Web UI as /home/kiosk/photos/) is shown as a
+// full-screen slideshow of the images in it, instead of Chromium's
+// directory listing. main.js swaps the folder URL for slideshow.html via
+// resolveSiteUrl(), then hands the page its image list with attach() -
+// the page itself has no filesystem access (contextIsolation, no Node).
+// The folder is re-read every minute, so images added or removed show up
+// without restarting the kiosk.
+//
+// Optional slideshow.json in the folder (all keys optional):
+//   { "interval": 10,        seconds per image (default 10, minimum 2)
+//     "shuffle": false,      random order instead of by file name
+//     "fit": "contain",      "contain" (whole image, letterboxed) or
+//                            "cover" (fill the screen, cropped)
+//     "transition": 1,       crossfade seconds (0 = instant cut)
+//     "recursive": false }   include images in subfolders
+
+const fs = require('fs');
+const path = require('path');
+const { fileURLToPath, pathToFileURL } = require('url');
+
+const SLIDESHOW_PAGE = path.join(__dirname, 'slideshow.html');
+const IMAGE_EXT = new Set(['.jpg', '.jpeg', '.png', '.gif', '.webp', '.bmp', '.svg', '.avif']);
+const REFRESH_MS = 60000;
+const DEFAULTS = { interval: 10, shuffle: false, fit: 'contain', transition: 1, recursive: false };
+
+// The folder path a site URL points at, or null if it isn't a slideshow.
+// A file:// URL counts when it's an existing directory, or ends in "/"
+// (so a folder that isn't there yet - e.g. a USB stick not plugged in -
+// still shows the slideshow's "no images" message, not an error page).
+function slideshowDir(url) {
+    if (typeof url !== 'string' || !url.startsWith('file://')) return null;
+    let p;
+    try {
+        p = fileURLToPath(url);
+    } catch (e) {
+        return null;
+    }
+    if (url.endsWith('/')) return p;
+    try {
+        return fs.statSync(p).isDirectory() ? p : null;
+    } catch (e) {
+        return null;
+    }
+}
+
+// What a view should actually load for a configured site URL.
+function resolveSiteUrl(url) {
+    const dir = slideshowDir(url);
+    if (!dir) return url;
+    const u = pathToFileURL(SLIDESHOW_PAGE);
+    u.searchParams.set('dir', dir);
+    return u.href;
+}
+
+function readOptions(dir) {
+    const opts = { ...DEFAULTS };
+    try {
+        const user = JSON.parse(fs.readFileSync(path.join(dir, 'slideshow.json'), 'utf8'));
+        if (Number(user.interval) > 0) opts.interval = Math.max(2, Number(user.interval));
+        if (typeof user.shuffle === 'boolean') opts.shuffle = user.shuffle;
+        if (user.fit === 'contain' || user.fit === 'cover') opts.fit = user.fit;
+        if (Number(user.transition) >= 0) opts.transition = Math.min(Number(user.transition), opts.interval / 2);
+        if (typeof user.recursive === 'boolean') opts.recursive = user.recursive;
+    } catch (e) {
+        // No (or unreadable) slideshow.json - defaults.
+    }
+    return opts;
+}
+
+function listImages(dir, recursive, depth = 0) {
+    let entries;
+    try {
+        entries = fs.readdirSync(dir, { withFileTypes: true });
+    } catch (e) {
+        return [];
+    }
+    const out = [];
+    for (const e of entries) {
+        if (e.name.startsWith('.')) continue;
+        const full = path.join(dir, e.name);
+        if (e.isDirectory()) {
+            if (recursive && depth < 8) out.push(...listImages(full, recursive, depth + 1));
+        } else if (IMAGE_EXT.has(path.extname(e.name).toLowerCase())) {
+            out.push(full);
+        }
+    }
+    return out;
+}
+
+function snapshot(dir) {
+    const options = readOptions(dir);
+    const files = listImages(dir, options.recursive)
+        .sort((a, b) => a.localeCompare(b, undefined, { numeric: true, sensitivity: 'base' }));
+    return {
+        dir,
+        exists: fs.existsSync(dir),
+        options,
+        images: files.map((f) => pathToFileURL(f).href),
+    };
+}
+
+// Feed a view's slideshow page its image list now and every REFRESH_MS
+// while it stays on a slideshow. Call once per view (main.js does, right
+// after creating it); safe on views that never show a slideshow.
+function attach(webContents) {
+    let lastSent = '';
+    const send = (force) => {
+        if (webContents.isDestroyed()) return;
+        const current = webContents.getURL();
+        if (!current.startsWith(pathToFileURL(SLIDESHOW_PAGE).href)) return;
+        const dir = new URL(current).searchParams.get('dir');
+        if (!dir) return;
+        const payload = JSON.stringify(snapshot(dir));
+        if (!force && payload === lastSent) return;
+        lastSent = payload;
+        webContents.executeJavaScript(`window.kioskSlideshow&&window.kioskSlideshow.update(${payload})`)
+            .catch(() => {});
+    };
+    webContents.on('did-finish-load', () => send(true));
+    const timer = setInterval(() => send(false), REFRESH_MS);
+    webContents.once('destroyed', () => clearInterval(timer));
+}
+
+module.exports = { resolveSiteUrl, slideshowDir, attach, snapshot };