show badges totaled in more areas

lib/widgets/count_badge.dart

@@ -0,0 +1,16 @@
+import "package:material_ui/material_ui.dart";
+
+/// Shows [count] in a badge on [child]: nothing if null, a dot if 0, and the
+/// number otherwise.
+class const CountBadge(
+  final int? count, {
+  required final Widget child,
+  super.key,
+}) extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) => switch (count) {
+    null => child,
+    0 => Badge(child: child),
+    final count => Badge.count(count: count, child: child),
+  };
+}

lib/widgets/room_appbar.dart

@@ -3,8 +3,10 @@ import "package:hooks_riverpod/hooks_riverpod.dart";
 import "package:nexus/controllers/rooms.dart";
 import "package:nexus/widgets/appbar.dart";
 import "package:nexus/widgets/avatar_or_hash.dart";
+import "package:nexus/widgets/count_badge.dart";
 import "package:nexus/widgets/room_menu_button.dart";
 import "package:nexus/widgets/room_summary_dialog.dart";
+import "package:nexus/widgets/sidebar.dart";
 
 final class const RoomAppbar({
   required final String? roomId,
@@ -49,7 +51,14 @@ final class const RoomAppbar({
                     dimension: 24,
                     fallback: Icon(Icons.numbers),
                   )
-          : DrawerButton(onPressed: onOpenDrawer),
+          : IconButton(
+              onPressed: onOpenDrawer,
+              tooltip: MaterialLocalizations.of(context).openAppDrawerTooltip,
+              icon: CountBadge(
+                Sidebar.totalBadgeCount(ref),
+                child: const DrawerButtonIcon(),
+              ),
+            ),
       scrolledUnderElevation: 0,
       title: room == null
           ? null

lib/widgets/room_list.dart

@@ -13,6 +13,7 @@ import "package:nexus/widgets/pages/settings.dart";
 import "package:nexus/widgets/join_dialog.dart";
 import "package:nexus/widgets/room_menu_button.dart";
 import "package:nexus/controllers/key.dart";
+import "package:nexus/controllers/rooms.dart";
 import "package:nexus/controllers/spaces.dart";
 import "package:collection/collection.dart";
 
@@ -26,9 +27,26 @@ class const RoomList({super.key}) extends ConsumerWidget implements NavPage {
   @override
   IconData get icon => Icons.list;
 
-  // TODO: Show unread badge here and on sidebar hamburger
   @override
-  int? badgeCount(WidgetRef ref) => null;
+  int? badgeCount(WidgetRef ref) {
+    final (notifications, hasUnread) = ref.watch(
+      RoomsController.provider.select(
+        (rooms) => rooms.values.fold(
+          (0, false),
+          (total, room) => (
+            total.$1 + (room.metadata?.unreadNotifications ?? 0),
+            total.$2 || (room.metadata?.unreadMessages ?? 0) > 0,
+          ),
+        ),
+      ),
+    );
+
+    return notifications > 0
+        ? notifications
+        : hasUnread
+        ? 0
+        : null;
+  }
 
   @override
   Widget build(BuildContext context, WidgetRef ref) {

lib/widgets/sidebar.dart

@@ -1,23 +1,36 @@
+import "package:collection/collection.dart";
 import "package:hooks_riverpod/hooks_riverpod.dart";
 import "package:material_ui/material_ui.dart";
 import "package:nexus/controllers/sidebar_page.dart";
 import "package:nexus/models/nav_page.dart";
 import "package:nexus/models/sidebar_page.dart";
+import "package:nexus/widgets/count_badge.dart";
 import "package:nexus/widgets/invites_list.dart";
 import "package:nexus/widgets/notifications_list.dart";
 import "package:nexus/widgets/room_list.dart";
 
 class const Sidebar({super.key}) extends ConsumerWidget {
+  static NavPage pageFor(SidebarPage page) => switch (page) {
+    .rooms => const RoomList(),
+    .notifications => const NotificationsList(),
+    .invites => const InvitesList(),
+  };
+
+  /// The badges of every tab added together, e.g. for the drawer button.
+  ///
+  /// Like [NavPage.badgeCount], null means no badges and 0 means only dots.
+  static int? totalBadgeCount(WidgetRef ref) {
+    final counts = SidebarPage.values
+        .map((page) => pageFor(page).badgeCount(ref))
+        .nonNulls;
+
+    return counts.isEmpty ? null : counts.sum;
+  }
+
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final selected = ref.watch(SidebarPageController.provider);
-    final pages = SidebarPage.values.map<NavPage>(
-      (page) => switch (page) {
-        .rooms => const RoomList(),
-        .notifications => const NotificationsList(),
-        .invites => const InvitesList(),
-      },
-    );
+    final pages = SidebarPage.values.map(pageFor);
 
     return Drawer(
       width: 330,
@@ -27,18 +40,17 @@ class const Sidebar({super.key}) extends ConsumerWidget {
         body: pages.elementAt(selected.index),
         bottomNavigationBar: NavigationBar(
           selectedIndex: selected.index,
-          destinations: pages.map((page) {
-            final badgeCount = page.badgeCount(ref);
-
-            return NavigationDestination(
-              icon: Badge.count(
-                count: badgeCount ?? 0,
-                isLabelVisible: badgeCount != null,
-                child: Icon(page.icon),
-              ),
-              label: page.title,
-            );
-          }).toList(),
+          destinations: pages
+              .map(
+                (page) => NavigationDestination(
+                  icon: CountBadge(
+                    page.badgeCount(ref),
+                    child: Icon(page.icon),
+                  ),
+                  label: page.title,
+                ),
+              )
+              .toList(),
           onDestinationSelected: (index) => ref
               .read(SidebarPageController.provider.notifier)
               .set(SidebarPage.values[index]),