feat: show unread count badge on favicon

Closes #560. Composes the active inbox's unread count over the base favicon as an SVG badge, served as a percent-encoded data: URL, so new mail is visible on a tab that is not focused — including when the browser collapses tabs to icon-only, where a title-based count disappears entirely. The base icon is read from the rendered <link rel="icon"> rather than from config, so admin and per-domain branding overrides are inherited for free: the count is drawn on whatever logo the deployment actually serves. Keeping the badge in SVG rather than rasterising to a canvas also means the browser can rasterise it at whatever size it asks for, so a HiDPI tab is not served a 16px bitmap. Notes on the approach: - The badge link is an *additional* icon link that we append and mark as ours; we never remove or mutate a link we did not create. Next's metadata icons are rendered by React, which keeps a fiber pointing at that DOM node, so removing it would leave React holding a detached node and throw "Cannot read properties of null (reading 'removeChild')" on the next commit that deletes the fiber. Appending instead means the last-declared icon wins, and non-SVG fallback links survive with their type/sizes intact. (The usual recipe for this feature — assign canvas.toDataURL() to the existing link's href — does both of the things that break here.) - Every change of state is an *insertion* of a fresh link of ours, never a mutation or a removal, because that is the only signal a browser reliably re-reads the favicon on. Firefox ignores an in-place href change, and it equally ignores a removal — so clearing the badge by deleting our link left a stale count painted on the tab until a hard reload. Clearing it instead inserts a new link of ours carrying the original base href. - Holding last place has to be defended: on a client-side navigation React re-hoists its metadata icon link into <head>, landing after ours, and the base icon silently wins again. A MutationObserver on <head> moves our own link back to the end whenever a foreign icon link appears — moving only our node, never anyone else's. It no-ops once ours is last again, so a move cannot feed itself. - The badge is a full-width band across the foot of the icon, drawn to the metrics measured from Gmail's own 16px favicon: band height 0.625 of the icon, digit cap height 0.44, flush to the edges, corners rounded by about a pixel. Full width is what keeps a three-glyph label legible — rounded ends waste exactly the horizontal space it needs. Neutral white with black digits rather than the conventional red: faviconUrl is admin-overridable and Bulwark's own icon is rgb(219,45,84), so a red badge sat red-on-red. - The base SVG may be admin-uploaded, and the branding route deliberately serves it under a sandboxing CSP because SVG can carry script. Re-emitting it as a same-origin data: URL would un-fence that, so script, foreignObject and every on* handler are stripped before serialising. - Mounted in the root layout, not on the mail route: the badge belongs to the tab, so mounting it on the page would clear it on every hop to settings, calendar or contacts.
2026-07-16 18:00:41 +02:00
parent 578339c400
commit 334fdbfb86
32 changed files with 1598 additions and 1 deletions
@@ -0,0 +1,33 @@
+"use client";
+
+import { useEmailStore } from "@/stores/email-store";
+import { useSettingsStore } from "@/stores/settings-store";
+import { useFaviconBadge } from "@/hooks/use-favicon-badge";
+
+/**
+ * Badges the browser-tab favicon with the inbox unread count, so new mail is
+ * visible without focusing the tab. See issue #560.
+ *
+ * Opt-out via the `faviconUnreadBadge` setting (Settings -> Appearance); on by
+ * default.
+ *
+ * Mounted in the root layout rather than on the mail route: the badge belongs
+ * to the tab, not to a page. Mounting it on the mail page unmounted it — and so
+ * cleared the badge, and flickered the icon — on every hop to /settings,
+ * /calendar or /contacts.
+ *
+ * Renders nothing.
+ */
+export function FaviconBadge() {
+  // The store's canonical inbox selector. `role === 'inbox'` alone is not
+  // enough: shared and group inboxes ship in the same `mailboxes` array, so on
+  // a delegated setup the first match can be somebody else's inbox.
+  const inboxUnread = useEmailStore(
+    (s) => s.mailboxes.find((m) => m.role === "inbox" && !m.isShared)?.unreadEmails ?? 0,
+  );
+  const enabled = useSettingsStore((s) => s.faviconUnreadBadge);
+
+  useFaviconBadge(inboxUnread, enabled);
+
+  return null;
+}