Refactor 4 (#80)

* fix: resolve 8 bugs across tray, settings, dialog, and lifecycle

Bug fixes:
- SystemTrayService.updateMenuState now rebuilds tray context menu after
  updating labels (menu was stale until next right-click)
- BuiltinInstanceService.dispose() explicitly discards stopInstance() future
  instead of fire-and-forget, and removes duplicate _upnpService.shutdown()
  call (stopInstance() already handles UPnP shutdown)
- AppearanceDialog: await async setThemeMode/setPrimaryColor calls so
  try-catch blocks can actually catch failures; add mounted guard before
  showing SnackBar after await
- SettingsPage locale dialog: await setLocale() before Navigator.pop so
  save failures are not silently swallowed; add mounted guard
- DebugProvider: replace in-place VNode list mutation (add/removeRange/clear)
  with immutable list reassignment to maintain VNode setter contract
- Input: add didUpdateWidget to sync _obscureText when parent changes
  obscureText prop
- App: remove duplicate loadSettings() call from _ThemeProviderState.initState
  (HomeWrapper._initialize already handles loading with proper await)

* perf: reduce repeated settings reads and remove dead initialization code

Performance:
- Refactor _getConfiguredRpcPort/Secret to accept optional settings map
  parameter, eliminating 2 redundant _readSettingsSnapshot() calls in both
  _buildArgs() and getBuiltinInstanceConfig() (6 sync file reads → 4)
- Remove unreachable duplicate guards in SystemTrayService.initialize()
  (dead code after in-flight await)

* refactor: code quality improvements across settings, widgets, and app

Code quality:
- SettingsPage._buildSettingsGroup: remove no-op identity map
  (.map((child) => child))
- Settings._settingsFileName: change from final to static const
- Settings: inline trivial _getDataDirectory() wrapper (single caller)
- CustomAppBar/CardX: remove redundant key forwarding to inner widget
  (Flutter handles key reconciliation on the outermost widget)
- App: extract _swapListener<T> helper to deduplicate 3 near-identical
  listener swap blocks in didChangeDependencies

* chore: minor cleanup across settings, enums, and virtual window frame

Cleanup:
- Remove unused dart:async import in AutoHideWindowService
- Fix _formatVersionLabel to display full version string (was showing
  only patch number, e.g. 'v3' instead of 'v1.2.3')
- Remove redundant inline comments on enum values in enums.dart
  (comments restated the value names)
- Simplify VirtualWindowFrame switch to a single conditional expression
  (first and third switch arms produced identical output)

* Update packages

* fix: resolve 5 bugs in RPC client, debug provider, and selection pruning

Bug fixes:
- DebugProvider: trim widgets.value alongside lines and _widgetCounts
  (widgets list was growing unboundedly while lines was capped at 100)
- Aria2RpcClient._handleWebSocketMessage: add type guard for non-Map
  JSON responses (arrays/primitives caused NoSuchMethodError)
- Aria2RpcClient._callHttpRpc: replace _httpClient! force-unwrap with
  null check + ConnectionFailedException (prevents crash after close())
- Aria2RpcClient: store WebSocket StreamSubscription in
  _webSocketSubscription field; cancel in close() and _connectWebSocket
  to prevent callbacks firing on disposed client
- DownloadPage._pruneSelection: skip setState when no keys were removed
  (prevents unnecessary rebuild cycles on every data change)

* perf: optimize filter, sort, and pieces grid rendering

Performance:
- DownloadPage._filterTasks: combine category filter, status/type filter,
  and search filter into a single retainWhere pass (was creating 3-5
  intermediate lists via .where().toList() per filter call)
- DownloadPage._filterTasks: inline sort key computation in comparator
  (eliminates O(n) sortKeys map allocation per sort)
- TaskDetailsBtHelpers._buildPiecesGrid: replace Wrap+List.generate with
  CustomPaint painter (renders thousands of pieces without creating
  individual Container widgets, eliminates O(n) widget allocation)

* refactor: code quality improvements across RPC client, dialogs, and models

Code quality:
- Aria2RpcClient._callHttpRpc: remove redundant response.body.contains
  check for 'Unauthorized' (structured JSON check is sufficient)
- Aria2RpcClient.getVersion: delegate to getVersionInfo() to eliminate
  duplicate RPC call
- Aria2RpcClient._handleWebSocketError: always wrap errors in
  ConnectionFailedException instead of leaking raw error types
- AddTaskDialog: move outputField creation inside two-column branch
  (was allocated but unused in single-column path)
- DownloadTask: add key getter ('::') to eliminate
  duplicate _taskKey function in download_page.dart and task_list_view.dart
- FilterSelector: inline trivial _getInstanceFilterOptions wrapper

* chore: minor cleanup in task service, utils, and helpers

Cleanup:
- DownloadTaskService: inline trivial _stoppingSeedingTip and
  _failedToStopSeedingMessage wrappers (single-line l10n accessors)
- task_utils: use Uri.file() instead of Uri.parse('file://...') for
  correct platform-specific file URI construction (handles paths with
  spaces and special characters on Linux/macOS)
- TaskDetailsBtHelpers: add explanatory comment to catch(_) block in
  parseTorrentMetadata (best-effort parsing returns empty on malformed
  torrent data)

* fix: address review findings — guards, error handling, and formatting

Bug fixes:
- TaskDetailsBtHelpers._buildPiecesGrid: add empty pieces guard to
  prevent ArgumentError from .clamp(1, 0) when pieces list is empty
- Aria2RpcClient._callHttpRpc: guard data['error'] is Map before
  accessing ['message'] to prevent TypeError on malformed responses
- Aria2RpcClient._handleWebSocketMessage: same guard for data['error']
  is Map before accessing ['message']
- AppearanceDialog: add try-catch to G and B slider onChangeEnd handlers
  (R slider already had error handling, G/B were missing)

Formatting:
- Run dart format on 7 files to comply with project 80-column style:
  virtual_window_frame, task_details_bt_helpers, download_page, enums,
  download_task_service, system_tray_service, aria2_rpc_client

Skipped findings (not valid):
- _connectWebSocket await subscription cancel: cancel() returns
  synchronously for non-pending operations, no race condition risk
- settings_page setLocale try-catch: already has await + context.mounted
  guard, setLocale failures propagate as unhandled which is acceptable

Author: GT-610

lib/app.dart

@@ -45,13 +45,6 @@ class _ThemeProvider extends StatefulWidget {
 }
 
 class _ThemeProviderState extends State<_ThemeProvider> {
-  @override
-  void initState() {
-    super.initState();
-    // Load settings
-    Provider.of<Settings>(context, listen: false).loadSettings();
-  }
-
   @override
   Widget build(BuildContext context) {
     final display = context
@@ -279,38 +272,45 @@ class _MainWindowState extends State<MainWindow> with WindowListener, Loggable {
   @override
   void didChangeDependencies() {
     super.didChangeDependencies();
-    final nextDownloadDataService = Provider.of<DownloadDataService>(
-      context,
-      listen: false,
+    _downloadDataService = _swapListener(
+      Provider.of<DownloadDataService>(context, listen: false),
+      _downloadDataService,
+      (l) => l?.removeListener(_handleDownloadNotifications),
+      (l) => l?.addListener(_handleDownloadNotifications),
     );
-    if (_downloadDataService != nextDownloadDataService) {
-      _downloadDataService?.removeListener(_handleDownloadNotifications);
-      _downloadDataService = nextDownloadDataService;
-      _downloadDataService?.addListener(_handleDownloadNotifications);
-    }
 
-    final nextInstanceManager = Provider.of<InstanceManager>(
-      context,
-      listen: false,
+    _instanceManager = _swapListener(
+      Provider.of<InstanceManager>(context, listen: false),
+      _instanceManager,
+      (l) => l?.removeListener(_handleInstanceManagerChanged),
+      (l) => l?.addListener(_handleInstanceManagerChanged),
     );
-    if (_instanceManager != nextInstanceManager) {
-      _instanceManager?.removeListener(_handleInstanceManagerChanged);
-      _instanceManager = nextInstanceManager;
-      _instanceManager?.addListener(_handleInstanceManagerChanged);
-    }
 
-    final nextSettings = Provider.of<Settings>(context, listen: false);
-    if (_settings != nextSettings) {
-      _settings?.removeListener(_handleSettingsChanged);
-      _settings = nextSettings;
-      _settings?.addListener(_handleSettingsChanged);
-    }
+    _settings = _swapListener(
+      Provider.of<Settings>(context, listen: false),
+      _settings,
+      (l) => l?.removeListener(_handleSettingsChanged),
+      (l) => l?.addListener(_handleSettingsChanged),
+    );
 
     WidgetsBinding.instance.addPostFrameCallback((_) {
       unawaited(_applyShellSettings());
     });
   }
 
+  T _swapListener<T>(
+    T next,
+    T? current,
+    void Function(T? l) remove,
+    void Function(T l) add,
+  ) {
+    if (current != next) {
+      remove(current);
+      add(next);
+    }
+    return next;
+  }
+
   void _handleSettingsChanged() {
     unawaited(_handleTrayStateChanged());
     unawaited(_applyShellSettings());

lib/kit/provider/debug.dart

@@ -28,7 +28,7 @@ final class DebugProvider {
     lines.add('$title$level$message');
 
     var widgetCount = 1;
-    widgets.value.add(
+    final newWidgets = <Widget>[
       Text.rich(
         TextSpan(
           children: [
@@ -47,10 +47,10 @@ final class DebugProvider {
           ],
         ),
       ),
-    );
+    ];
     if (record.stackTrace != null) {
       widgetCount++;
-      widgets.value.add(
+      newWidgets.add(
         SingleChildScrollView(
           scrollDirection: Axis.horizontal,
           child: Text(
@@ -61,24 +61,24 @@ final class DebugProvider {
       );
     }
     widgetCount++;
-    widgets.value.add(UIs.height13);
+    newWidgets.add(UIs.height13);
     _widgetCounts.add(widgetCount);
 
     while (lines.length > maxLines) {
-      final removed = _widgetCounts.removeAt(0);
+      final removeCount = _widgetCounts.removeAt(0);
       lines.removeAt(0);
-      if (widgets.value.length >= removed) {
-        widgets.value.removeRange(0, removed);
+      if (widgets.value.length >= removeCount) {
+        widgets.value = widgets.value.sublist(removeCount);
       }
     }
-    widgets.notify();
+
+    widgets.value = [...widgets.value, ...newWidgets];
   }
 
   static void clear() {
-    widgets.value.clear();
+    widgets.value = [];
     lines.clear();
     _widgetCounts.clear();
-    widgets.notify();
   }
 
   static void copy() =>

lib/kit/widgets/appbar.dart

@@ -30,7 +30,6 @@ class CustomAppBar extends StatelessWidget implements PreferredSizeWidget {
   @override
   Widget build(BuildContext context) {
     return AppBar(
-      key: key,
       title: title,
       actions: actions,
       centerTitle: centerTitle,

lib/kit/widgets/card.dart

@@ -19,7 +19,6 @@ class CardX extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     return Card(
-      key: key,
       clipBehavior: clipBehavior,
       color: color,
       shape: RoundedRectangleBorder(borderRadius: radius ?? borderRadius),

lib/kit/widgets/input.dart

@@ -69,6 +69,14 @@ class Input extends StatefulWidget {
 class _InputState extends State<Input> {
   late bool _obscureText = widget.obscureText;
 
+  @override
+  void didUpdateWidget(covariant Input oldWidget) {
+    super.didUpdateWidget(oldWidget);
+    if (widget.obscureText != oldWidget.obscureText) {
+      _obscureText = widget.obscureText;
+    }
+  }
+
   @override
   Widget build(BuildContext context) {
     final icon = widget.icon != null

lib/kit/widgets/virtual_window_frame.dart

@@ -22,16 +22,17 @@ class VirtualWindowFrame extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final content = switch (CustomAppBar.sysStatusBarHeight) {
-      0.0 => child,
-      _ when showCaption && WindowFrameConfig.showCaption => Column(
-        children: [
-          _WindowCaption(title: title),
-          Expanded(child: child),
-        ],
-      ),
-      _ => child,
-    };
+    final content =
+        (CustomAppBar.sysStatusBarHeight != 0.0 &&
+            showCaption &&
+            WindowFrameConfig.showCaption)
+        ? Column(
+            children: [
+              _WindowCaption(title: title),
+              Expanded(child: child),
+            ],
+          )
+        : child;
     return wm.VirtualWindowFrame(child: content);
   }
 }

lib/models/settings.dart

@@ -84,16 +84,11 @@ class Settings extends ChangeNotifier with Loggable {
       'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36'; // User agent
 
   // Settings file name
-  final String _settingsFileName = 'settings.json';
+  static const String _settingsFileName = 'settings.json';
 
   // Constructor initialization
   Settings();
 
-  /// Get program data directory
-  Directory _getDataDirectory() {
-    return getAppDataDirectory();
-  }
-
   Future<String> _defaultDownloadDirectory() {
     return Future.value(getDefaultDownloadDirectorySync());
   }
@@ -165,7 +160,7 @@ class Settings extends ChangeNotifier with Loggable {
 
   /// Get settings file path
   String _getSettingsFilePath() {
-    final dataDir = _getDataDirectory();
+    final dataDir = getAppDataDirectory();
     final configDir = Directory(p.join(dataDir.path, 'config'));
     if (!configDir.existsSync()) {
       configDir.createSync(recursive: true);

lib/pages/download_page/components/add_task_dialog.dart

@@ -559,18 +559,6 @@ class _AddTaskDialogState extends State<AddTaskDialog>
     return LayoutBuilder(
       builder: (context, constraints) {
         final useTwoColumns = constraints.maxWidth >= 480;
-        final splitField = _buildSplitStepper(l10n);
-        final outputField = Expanded(
-          flex: 3,
-          child: TextField(
-            controller: outputFileNameController,
-            enabled: !_isSubmitting,
-            decoration: InputDecoration(
-              labelText: l10n.renameOutput,
-              hintText: l10n.renameOutputPlaceholder,
-            ),
-          ),
-        );
 
         if (!useTwoColumns) {
           return Column(
@@ -589,6 +577,19 @@ class _AddTaskDialogState extends State<AddTaskDialog>
           );
         }
 
+        final splitField = _buildSplitStepper(l10n);
+        final outputField = Expanded(
+          flex: 3,
+          child: TextField(
+            controller: outputFileNameController,
+            enabled: !_isSubmitting,
+            decoration: InputDecoration(
+              labelText: l10n.renameOutput,
+              hintText: l10n.renameOutputPlaceholder,
+            ),
+          ),
+        );
+
         return Row(
           crossAxisAlignment: CrossAxisAlignment.start,
           children: [outputField, const SizedBox(width: 12), splitField],

lib/pages/download_page/components/filter_selector.dart

@@ -88,7 +88,7 @@ class FilterSelector extends StatelessWidget {
                               borderRadius: BorderRadius.circular(20),
                             ),
                           ),
-                          ..._getInstanceFilterOptions().map((instanceId) {
+                          ...instanceIds.map((instanceId) {
                             final isSelected = selectedInstanceId == instanceId;
                             final instanceColor = colorScheme.tertiary;
                             final instanceName =
@@ -220,10 +220,6 @@ class FilterSelector extends StatelessWidget {
     }
   }
 
-  List<String> _getInstanceFilterOptions() {
-    return instanceIds;
-  }
-
   List<FilterOption> _getFilterOptionsForCurrentCategory() {
     switch (currentCategoryType) {
       case CategoryType.byStatus: