feat: add visual density settings and custom font preview function + fix settings apply

Author: 777genius

frontend/lib/core/hotkeys/keyboard_state_resetter.dart

@@ -0,0 +1,61 @@
+import 'package:flutter/services.dart';
+import 'package:flutter/widgets.dart';
+
+/// Следит за lifecycle и сбрасывает состояние клавиатуры при смене активности.
+///
+/// На desktop иногда теряются KeyUp события при потере фокуса/сворачивании окна,
+/// из‑за чего следующий KeyDown может вызвать assert в `HardwareKeyboard`.
+class KeyboardStateResetter extends StatefulWidget {
+  const KeyboardStateResetter({required this.child, super.key});
+
+  final Widget child;
+
+  @override
+  State<KeyboardStateResetter> createState() => _KeyboardStateResetterState();
+}
+
+class _KeyboardStateResetterState extends State<KeyboardStateResetter>
+    with WidgetsBindingObserver {
+  static const bool _isFlutterTest = bool.fromEnvironment('FLUTTER_TEST');
+
+  @override
+  void initState() {
+    super.initState();
+    if (_isFlutterTest) return;
+    WidgetsBinding.instance.addObserver(this);
+  }
+
+  @override
+  void didChangeAppLifecycleState(AppLifecycleState state) {
+    switch (state) {
+      case AppLifecycleState.resumed:
+      case AppLifecycleState.inactive:
+      case AppLifecycleState.paused:
+      case AppLifecycleState.detached:
+      case AppLifecycleState.hidden:
+        _clearKeyboardState();
+        break;
+    }
+  }
+
+  void _clearKeyboardState() {
+    // HardwareKeyboard API отличается между версиями Flutter — вызываем мягко.
+    try {
+      final dynamic hw = HardwareKeyboard.instance;
+      hw.clearState();
+    } catch (_) {}
+  }
+
+  @override
+  void dispose() {
+    if (_isFlutterTest) {
+      super.dispose();
+      return;
+    }
+    WidgetsBinding.instance.removeObserver(this);
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) => widget.child;
+}

frontend/lib/features/custom_fonts/application/font_service.dart

@@ -1,4 +1,6 @@
 import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+import 'package:uuid/uuid.dart';
 import '../domain/entities/custom_font.dart';
 import '../domain/repositories/font_repository.dart';
 import '../domain/usecases/load_custom_font.dart';
@@ -11,6 +13,7 @@ import '../infrastructure/repositories/font_repository_impl.dart';
 /// Following Facade Pattern and Single Responsibility Principle
 class FontService {
   static FontService? _instance;
+  static const _uuid = Uuid();
   late final FontRepository _repository;
   late final LoadCustomFontUseCase _loadUseCase;
   late final SaveCustomFontUseCase _saveUseCase;
@@ -19,6 +22,11 @@ class FontService {
   /// Current loaded custom font (null if using system font)
   final ValueNotifier<CustomFont?> currentFont = ValueNotifier(null);
 
+  /// Pending font for preview (not yet saved)
+  CustomFont? _pendingFont;
+  Uint8List? _pendingFontData;
+  bool _pendingRemove = false;
+
   /// Factory constructor for singleton
   factory FontService() {
     _instance ??= FontService._internal();
@@ -45,8 +53,90 @@ class FontService {
     }
   }
 
+  /// Load font for preview only (register in memory, don't save to storage)
+  /// Call commitPendingFont() to save permanently
+  Future<CustomFont> loadFontForPreview({
+    required Uint8List fontData,
+    required String fileName,
+    required String familyName,
+  }) async {
+    if (fontData.isEmpty) {
+      throw ArgumentError('Font data cannot be empty');
+    }
+    if (familyName.isEmpty) {
+      throw ArgumentError('Font family name cannot be empty');
+    }
+
+    // Создаём entity для превью
+    final font = CustomFont(
+      id: _uuid.v4(),
+      name: fileName,
+      familyName: familyName,
+      uploadedAt: DateTime.now(),
+      sizeInBytes: fontData.length,
+    );
+
+    // Регистрируем шрифт в Flutter (только в памяти)
+    final loader = FontLoader(familyName);
+    loader.addFont(Future.value(ByteData.sublistView(fontData)));
+    await loader.load();
+
+    // Сохраняем как pending
+    _pendingFont = font;
+    _pendingFontData = fontData;
+    _pendingRemove = false;
+
+    return font;
+  }
+
+  /// Get pending font (for preview in settings)
+  CustomFont? get pendingFont => _pendingFont;
+
+  /// Check if there's a pending remove operation
+  bool get hasPendingRemove => _pendingRemove;
+
+  /// Check if there are any pending changes
+  bool get hasPendingChanges => _pendingFont != null || _pendingRemove;
+
+  /// Mark current font for removal (will be removed on commit)
+  void markFontForRemoval() {
+    _pendingRemove = true;
+    _pendingFont = null;
+    _pendingFontData = null;
+  }
+
+  /// Commit pending changes (save font or remove)
+  Future<void> commitPendingChanges() async {
+    if (_pendingRemove) {
+      // Удаляем текущий шрифт
+      await _removeUseCase.execute();
+      currentFont.value = null;
+      _pendingRemove = false;
+    } else if (_pendingFont != null && _pendingFontData != null) {
+      // Удаляем старый шрифт если есть
+      if (currentFont.value != null) {
+        await _removeUseCase.execute();
+      }
+      // Сохраняем новый шрифт
+      await _repository.saveFontData(_pendingFont!.id, _pendingFontData!);
+      await _repository.saveCustomFont(_pendingFont!);
+      currentFont.value = _pendingFont;
+    }
+    // Очищаем pending состояние
+    _pendingFont = null;
+    _pendingFontData = null;
+  }
+
+  /// Cancel pending changes
+  void cancelPendingChanges() {
+    _pendingFont = null;
+    _pendingFontData = null;
+    _pendingRemove = false;
+  }
+
   /// Save and load a new custom font
   /// Returns the saved font metadata
+  @Deprecated('Use loadFontForPreview + commitPendingChanges instead')
   Future<CustomFont> saveCustomFont({
     required Uint8List fontData,
     required String fileName,
@@ -69,6 +159,7 @@ class FontService {
   }
 
   /// Remove custom font and revert to system font
+  @Deprecated('Use markFontForRemoval + commitPendingChanges instead')
   Future<void> removeCustomFont() async {
     await _removeUseCase.execute();
     currentFont.value = null;

frontend/lib/features/custom_fonts/presentation/providers/font_provider.dart

@@ -16,17 +16,43 @@ class FontProvider extends ChangeNotifier {
   bool get hasCustomFont => _fontService.hasCustomFont();
   String? get fontFamily => _fontService.getCurrentFontFamily();
 
+  /// Pending font for preview (not yet saved)
+  CustomFont? get pendingFont => _fontService.pendingFont;
+
+  /// Check if font marked for removal
+  bool get hasPendingRemove => _fontService.hasPendingRemove;
+
+  /// Check if there are pending changes
+  bool get hasPendingChanges => _fontService.hasPendingChanges;
+
+  /// Effective font family for preview (pending or current)
+  String? get previewFontFamily {
+    if (_fontService.hasPendingRemove) return null;
+    return _fontService.pendingFont?.familyName ?? currentFont?.familyName;
+  }
+
+  /// Effective font for display (pending or current)
+  CustomFont? get effectiveFont {
+    if (_fontService.hasPendingRemove) return null;
+    return _fontService.pendingFont ?? currentFont;
+  }
+
+  /// Check if effectively has a custom font (for preview)
+  bool get effectivelyHasCustomFont {
+    if (_fontService.hasPendingRemove) return false;
+    return _fontService.pendingFont != null || hasCustomFont;
+  }
+
   FontProvider() {
-    // Listen to font changes from service
     _fontService.currentFont.addListener(_onFontChanged);
   }
 
   void _onFontChanged() {
     notifyListeners();
   }
 
-  /// Load a custom font from file
-  Future<void> loadCustomFont({
+  /// Load font for preview (not saved yet)
+  Future<void> loadFontForPreview({
     required Uint8List fontData,
     required String fileName,
     required String familyName,
@@ -35,11 +61,12 @@ class FontProvider extends ChangeNotifier {
     _clearError();
 
     try {
-      await _fontService.saveCustomFont(
+      await _fontService.loadFontForPreview(
         fontData: fontData,
         fileName: fileName,
         familyName: familyName,
       );
+      notifyListeners();
     } catch (e) {
       _setError('Failed to load font: $e');
       rethrow;
@@ -48,21 +75,34 @@ class FontProvider extends ChangeNotifier {
     }
   }
 
-  /// Remove custom font and revert to system font
-  Future<void> removeCustomFont() async {
+  /// Mark font for removal (will be removed on commit)
+  void markFontForRemoval() {
+    _fontService.markFontForRemoval();
+    notifyListeners();
+  }
+
+  /// Commit pending changes (save or remove font)
+  Future<void> commitPendingChanges() async {
     _setLoading(true);
     _clearError();
 
     try {
-      await _fontService.removeCustomFont();
+      await _fontService.commitPendingChanges();
+      notifyListeners();
     } catch (e) {
-      _setError('Failed to remove font: $e');
+      _setError('Failed to save font changes: $e');
       rethrow;
     } finally {
       _setLoading(false);
     }
   }
 
+  /// Cancel pending changes
+  void cancelPendingChanges() {
+    _fontService.cancelPendingChanges();
+    notifyListeners();
+  }
+
   void _setLoading(bool value) {
     _isLoading = value;
     notifyListeners();