Extract snackbar notifications to UISnackbars utility

Centralises all SnackBar calls behind UISnackbars.showError/showSuccess/
showWarning/showInfo, each themed via AppColorExtension. New warning and
info colour tokens added to both themes. Calling any method clears any
visible snackbar before showing the new one.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/lib/devices/device_list.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import '../model/device.dart';
 import '../utils/friendly_date_formatter.dart';
 import '../utils/oott_api.dart';
+import '../utils/ui_snackbars.dart';
 import '../widgets/status_badge.dart';
 
 const _deviceTypes = [
@@ -69,8 +70,7 @@ class _DeviceListState extends State<DeviceList> {
     }
   }
 
-  Future<void> _confirmForget(BuildContext context, Device device) async {
-    final messenger = ScaffoldMessenger.of(context);
+  Future<void> _confirmForget(Device device) async {
     final colorScheme = Theme.of(context).colorScheme;
 
     final confirmed = await showDialog<bool>(
@@ -99,28 +99,15 @@ class _DeviceListState extends State<DeviceList> {
     try {
       await BackendAPI.instance.forgetDevice(device.macAddress);
       if (!mounted) return;
-      messenger.showSnackBar(
-        const SnackBar(
-          content: Text('Device forgotten'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
-      );
+      UISnackbars.showSuccess(context, 'Device forgotten');
       _loadDevices();
     } catch (e) {
       if (!mounted) return;
-      messenger.showSnackBar(
-        SnackBar(
-          content: Text('Failed to forget device: $e'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
-      );
+      UISnackbars.showError(context, 'Failed to forget device: $e');
     }
   }
 
-  Future<void> _showRegisterDialog(BuildContext context, Device device) async {
-    final messenger = ScaffoldMessenger.of(context);
+  Future<void> _showRegisterDialog(Device device) async {
     final formKey = GlobalKey<FormState>();
     String owner = '';
     String deviceType = _deviceTypes.contains(device.deviceType)
@@ -189,23 +176,11 @@ class _DeviceListState extends State<DeviceList> {
         deviceType,
       );
       if (!mounted) return;
-      messenger.showSnackBar(
-        const SnackBar(
-          content: Text('Device registered'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
-      );
+      UISnackbars.showSuccess(context, 'Device registered');
       _loadDevices();
     } catch (e) {
       if (!mounted) return;
-      messenger.showSnackBar(
-        SnackBar(
-          content: Text('Failed to register device: $e'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
-      );
+      UISnackbars.showError(context, 'Failed to register device: $e');
     }
   }
 
@@ -335,12 +310,9 @@ class _DeviceListState extends State<DeviceList> {
                                   icon: const Icon(Icons.more_vert),
                                   onSelected: (value) async {
                                     if (value == 'forget') {
-                                      await _confirmForget(context, device);
+                                      await _confirmForget(device);
                                     } else if (value == 'register') {
-                                      await _showRegisterDialog(
-                                        context,
-                                        device,
-                                      );
+                                      await _showRegisterDialog(device);
                                     }
                                   },
                                   itemBuilder: (context) => [

frontend/lib/notifications/notification_list.dart

@@ -6,6 +6,7 @@ import 'package:infinite_scroll_pagination/infinite_scroll_pagination.dart';
 import '../model/notification.dart' as oott_model;
 import '../utils/friendly_date_formatter.dart';
 import '../utils/oott_api.dart';
+import '../utils/ui_snackbars.dart';
 
 class NotificationList extends StatefulWidget {
   const NotificationList({super.key});
@@ -48,13 +49,7 @@ class _NotificationListState extends State<NotificationList> {
     await BackendAPI.instance.markAllNotificationsAsRead();
     _pagingController.refresh();
     if (context.mounted) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(
-          content: Text('All notifications marked as read'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
-      );
+      UISnackbars.showSuccess(context, 'All notifications marked as read');
     }
   }
 
@@ -63,24 +58,15 @@ class _NotificationListState extends State<NotificationList> {
     oott_model.Notification item,
   ) async {
     if (!item.isNew) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text('Notification was already marked as read'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
+      UISnackbars.showWarning(
+        context,
+        'Notification was already marked as read',
       );
       return false;
     }
     await BackendAPI.instance.markNotificationAsRead(item.id);
     if (!context.mounted) return false;
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text('Event marked as read'),
-        behavior: SnackBarBehavior.floating,
-        showCloseIcon: true,
-      ),
-    );
+    UISnackbars.showSuccess(context, 'Event marked as read');
     if (_filterChoice != 3) {
       _pagingController.value = _pagingController.value.filterItems(
         (n) => n.id != item.id,
@@ -98,24 +84,15 @@ class _NotificationListState extends State<NotificationList> {
     oott_model.Notification item,
   ) async {
     if (item.isNew) {
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(
-          content: Text('Notification was already marked as unread'),
-          behavior: SnackBarBehavior.floating,
-          showCloseIcon: true,
-        ),
+      UISnackbars.showWarning(
+        context,
+        'Notification was already marked as unread',
       );
       return false;
     }
     await BackendAPI.instance.markNotificationAsNew(item.id);
     if (!context.mounted) return false;
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text('Event marked as unread'),
-        behavior: SnackBarBehavior.floating,
-        showCloseIcon: true,
-      ),
-    );
+    UISnackbars.showSuccess(context, 'Event marked as unread');
     if (_filterChoice != 3) {
       _pagingController.value = _pagingController.value.filterItems(
         (n) => n.id != item.id,
@@ -183,92 +160,86 @@ class _NotificationListState extends State<NotificationList> {
                 ),
               ),
             ),
-                PagedSliverList<int, oott_model.Notification>(
-                  state: state,
-                  fetchNextPage: fetchNextPage,
-                  builderDelegate: PagedChildBuilderDelegate(
-                    itemBuilder: (context, item, index) {
-                      return Column(
-                        children: [
-                          Dismissible(
-                            key: UniqueKey(),
-                            confirmDismiss: (direction) =>
-                                direction == DismissDirection.startToEnd
-                                ? _markAsNew(context, item)
-                                : _markAsRead(context, item),
-                            background: Container(
-                              color: Theme.of(
-                                context,
-                              ).colorScheme.tertiaryContainer,
-                              alignment: Alignment.centerLeft,
-                              padding: const EdgeInsets.only(left: 16),
-                              child: Icon(Icons.mark_email_unread),
-                            ),
-                            secondaryBackground: Container(
-                              color: Theme.of(
-                                context,
-                              ).colorScheme.primaryContainer,
-                              alignment: Alignment.centerRight,
-                              padding: const EdgeInsets.only(right: 16),
-                              child: Icon(Icons.done),
-                            ),
-                            child: ListTile(
-                              tileColor: item.isNew
-                                  ? Theme.of(
-                                      context,
-                                    ).colorScheme.secondaryContainer
-                                  : null,
-                              leading: Icon(
-                                item.notificationType.icon,
-                                color: item.isNew
-                                    ? Theme.of(context).colorScheme.primary
-                                    : null,
-                              ),
-                              title: Text(
-                                '${FriendlyDateFormatter().format(item.createdOn)} - ${item.title}',
-                                style: item.isNew
-                                    ? const TextStyle(
-                                        fontWeight: FontWeight.bold,
-                                      )
-                                    : null,
-                              ),
-                              subtitle: Text(item.body, maxLines: 5),
-                              trailing: PopupMenuButton<String>(
-                                icon: const Icon(Icons.more_vert),
-                                onSelected: (value) async {
-                                  if (value == 'mark_read') {
-                                    await _markAsRead(context, item);
-                                  } else if (value == 'mark_new') {
-                                    await _markAsNew(context, item);
-                                  }
-                                },
-                                itemBuilder: (context) => [
-                                  if (item.isNew)
-                                    const PopupMenuItem(
-                                      value: 'mark_read',
-                                      child: Text('Mark as read'),
-                                    ),
-                                  if (!item.isNew)
-                                    const PopupMenuItem(
-                                      value: 'mark_new',
-                                      child: Text('Mark as unread'),
-                                    ),
-                                ],
-                              ),
-                              onTap: () {},
-                              isThreeLine: true,
-                            ),
+            PagedSliverList<int, oott_model.Notification>(
+              state: state,
+              fetchNextPage: fetchNextPage,
+              builderDelegate: PagedChildBuilderDelegate(
+                itemBuilder: (context, item, index) {
+                  return Column(
+                    children: [
+                      Dismissible(
+                        key: UniqueKey(),
+                        confirmDismiss: (direction) =>
+                            direction == DismissDirection.startToEnd
+                            ? _markAsNew(context, item)
+                            : _markAsRead(context, item),
+                        background: Container(
+                          color: Theme.of(
+                            context,
+                          ).colorScheme.tertiaryContainer,
+                          alignment: Alignment.centerLeft,
+                          padding: const EdgeInsets.only(left: 16),
+                          child: Icon(Icons.mark_email_unread),
+                        ),
+                        secondaryBackground: Container(
+                          color: Theme.of(context).colorScheme.primaryContainer,
+                          alignment: Alignment.centerRight,
+                          padding: const EdgeInsets.only(right: 16),
+                          child: Icon(Icons.done),
+                        ),
+                        child: ListTile(
+                          tileColor: item.isNew
+                              ? Theme.of(context).colorScheme.secondaryContainer
+                              : null,
+                          leading: Icon(
+                            item.notificationType.icon,
+                            color: item.isNew
+                                ? Theme.of(context).colorScheme.primary
+                                : null,
                           ),
-                          Divider(),
-                        ],
-                      );
-                    },
-                  ),
-                ),
-              ],
+                          title: Text(
+                            '${FriendlyDateFormatter().format(item.createdOn)} - ${item.title}',
+                            style: item.isNew
+                                ? const TextStyle(fontWeight: FontWeight.bold)
+                                : null,
+                          ),
+                          subtitle: Text(item.body, maxLines: 5),
+                          trailing: PopupMenuButton<String>(
+                            icon: const Icon(Icons.more_vert),
+                            onSelected: (value) async {
+                              if (value == 'mark_read') {
+                                await _markAsRead(context, item);
+                              } else if (value == 'mark_new') {
+                                await _markAsNew(context, item);
+                              }
+                            },
+                            itemBuilder: (context) => [
+                              if (item.isNew)
+                                const PopupMenuItem(
+                                  value: 'mark_read',
+                                  child: Text('Mark as read'),
+                                ),
+                              if (!item.isNew)
+                                const PopupMenuItem(
+                                  value: 'mark_new',
+                                  child: Text('Mark as unread'),
+                                ),
+                            ],
+                          ),
+                          onTap: () {},
+                          isThreeLine: true,
+                        ),
+                      ),
+                      Divider(),
+                    ],
+                  );
+                },
+              ),
             ),
-          ),
-      );
+          ],
+        ),
+      ),
+    );
     // Paginated list end
   }
 

frontend/lib/theme/app_colors.dart

@@ -2,17 +2,38 @@ import 'package:flutter/material.dart';
 
 @immutable
 class AppColorExtension extends ThemeExtension<AppColorExtension> {
-  const AppColorExtension({required this.success, required this.onSuccess});
+  const AppColorExtension({
+    required this.success,
+    required this.onSuccess,
+    required this.warning,
+    required this.onWarning,
+    required this.info,
+    required this.onInfo,
+  });
 
   final Color success;
   final Color onSuccess;
+  final Color warning;
+  final Color onWarning;
+  final Color info;
+  final Color onInfo;
 
   @override
-  AppColorExtension copyWith({Color? success, Color? onSuccess}) =>
-      AppColorExtension(
-        success: success ?? this.success,
-        onSuccess: onSuccess ?? this.onSuccess,
-      );
+  AppColorExtension copyWith({
+    Color? success,
+    Color? onSuccess,
+    Color? warning,
+    Color? onWarning,
+    Color? info,
+    Color? onInfo,
+  }) => AppColorExtension(
+    success: success ?? this.success,
+    onSuccess: onSuccess ?? this.onSuccess,
+    warning: warning ?? this.warning,
+    onWarning: onWarning ?? this.onWarning,
+    info: info ?? this.info,
+    onInfo: onInfo ?? this.onInfo,
+  );
 
   @override
   AppColorExtension lerp(AppColorExtension? other, double t) {
@@ -20,6 +41,10 @@ class AppColorExtension extends ThemeExtension<AppColorExtension> {
     return AppColorExtension(
       success: Color.lerp(success, other.success, t)!,
       onSuccess: Color.lerp(onSuccess, other.onSuccess, t)!,
+      warning: Color.lerp(warning, other.warning, t)!,
+      onWarning: Color.lerp(onWarning, other.onWarning, t)!,
+      info: Color.lerp(info, other.info, t)!,
+      onInfo: Color.lerp(onInfo, other.onInfo, t)!,
     );
   }
 }

frontend/lib/theme/catppuccin_mocha_theme.dart

@@ -84,6 +84,10 @@ final ThemeData catppuccinMochaDarkTheme = ThemeData(
     const AppColorExtension(
       success: CatppuccinMochaColors.green,
       onSuccess: CatppuccinMochaColors.crust,
+      warning: CatppuccinMochaColors.peach,
+      onWarning: CatppuccinMochaColors.crust,
+      info: CatppuccinMochaColors.blue,
+      onInfo: CatppuccinMochaColors.crust,
     ),
   ],
 );

frontend/lib/theme/gruvbox_theme.dart

@@ -81,6 +81,10 @@ final ThemeData gruvboxDarkTheme = ThemeData(
     const AppColorExtension(
       success: GruvboxColors.brightGreen,
       onSuccess: GruvboxColors.bgHard,
+      warning: GruvboxColors.brightYellow,
+      onWarning: GruvboxColors.bgHard,
+      info: GruvboxColors.brightBlue,
+      onInfo: GruvboxColors.bgHard,
     ),
   ],
 );

frontend/lib/utils/ui_snackbars.dart

@@ -3,30 +3,39 @@ import '../theme/app_colors.dart';
 
 class UISnackbars {
   static void showError(BuildContext context, String message) {
-    ScaffoldMessenger.of(context).showSnackBar(
-      SnackBar(
-        content: Text(
-          message,
-          style: TextStyle(color: Theme.of(context).colorScheme.onError),
-        ),
-        behavior: SnackBarBehavior.floating,
-        showCloseIcon: true,
-        backgroundColor: Theme.of(context).colorScheme.error,
-      ),
-    );
+    final colorScheme = Theme.of(context).colorScheme;
+    _show(context, message, colorScheme.error, colorScheme.onError);
   }
 
   static void showSuccess(BuildContext context, String message) {
     final appColors = Theme.of(context).extension<AppColorExtension>()!;
-    ScaffoldMessenger.of(context).showSnackBar(
+    _show(context, message, appColors.success, appColors.onSuccess);
+  }
+
+  static void showWarning(BuildContext context, String message) {
+    final appColors = Theme.of(context).extension<AppColorExtension>()!;
+    _show(context, message, appColors.warning, appColors.onWarning);
+  }
+
+  static void showInfo(BuildContext context, String message) {
+    final appColors = Theme.of(context).extension<AppColorExtension>()!;
+    _show(context, message, appColors.info, appColors.onInfo);
+  }
+
+  static void _show(
+    BuildContext context,
+    String message,
+    Color background,
+    Color foreground,
+  ) {
+    final messenger = ScaffoldMessenger.of(context);
+    messenger.clearSnackBars();
+    messenger.showSnackBar(
       SnackBar(
-        content: Text(
-          message,
-          style: TextStyle(color: appColors.onSuccess),
-        ),
+        content: Text(message, style: TextStyle(color: foreground)),
         behavior: SnackBarBehavior.floating,
         showCloseIcon: true,
-        backgroundColor: appColors.success,
+        backgroundColor: background,
       ),
     );
   }