added interface themes

CursorLang/Services/IThemeService.cs

@@ -0,0 +1,19 @@
+using System.Windows;
+using CursorLang.Models;
+
+namespace CursorLang.Services;
+
+/// <summary>
+/// Применяет светлое или тёмное оформление к окнам приложения.
+/// </summary>
+public interface IThemeService
+{
+    /// <summary>Тема, действующая сейчас.</summary>
+    AppTheme CurrentTheme { get; }
+
+    /// <summary>
+    /// Подключает окно к смене темы: заголовок окна рисует Windows,
+    /// и его цвет приходится переключать для каждого окна отдельно.
+    /// </summary>
+    void Register(Window window);
+}

CursorLang/Services/SettingsService.cs

@@ -90,12 +90,10 @@ public sealed class SettingsService : IDisposable
         }
         catch (Exception e) when (e is IOException or UnauthorizedAccessException or JsonException)
         {
-            // Испорченный файл не должен мешать запуску: начнём с умолчаний
             return null;
         }
     }
 
-    // Язык по умолчанию берём системный, если он поддерживается
     private static AppSettings CreateDefault()
     {
         string uiLanguage = System.Globalization.CultureInfo.CurrentUICulture.TwoLetterISOLanguageName;

CursorLang/Services/ThemeService.cs

@@ -0,0 +1,144 @@
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Interop;
+using CursorLang.Interop;
+using CursorLang.Models;
+using Microsoft.Win32;
+
+namespace CursorLang.Services;
+
+/// <summary>
+/// Держит в ресурсах приложения палитру выбранной темы и подменяет её
+/// при смене настройки — окна перекрашиваются без перезапуска.
+/// </summary>
+public sealed class ThemeService : IThemeService, IDisposable
+{
+    private const string PersonalizeKey =
+        @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
+
+    private readonly AppSettings _settings;
+    private readonly List<Window> _windows = [];
+    private ResourceDictionary? _palette;
+    private AppTheme _current;
+
+    public ThemeService(AppSettings settings)
+    {
+        _settings = settings;
+        _settings.PropertyChanged += OnSettingsChanged;
+        SystemEvents.UserPreferenceChanged += OnUserPreferenceChanged;
+        Apply();
+    }
+
+    /// <summary>Тема, которую видит пользователь: <c>System</c> здесь уже разрешён.</summary>
+    public AppTheme CurrentTheme => _current;
+
+    public void Register(Window window)
+    {
+        _windows.Add(window);
+        window.Closed += OnWindowClosed;
+
+        if (new WindowInteropHelper(window).Handle == IntPtr.Zero)
+        {
+            window.SourceInitialized += OnWindowSourceInitialized;
+            return;
+        }
+
+        ApplyTitleBar(window);
+    }
+
+    public void Dispose()
+    {
+        _settings.PropertyChanged -= OnSettingsChanged;
+        SystemEvents.UserPreferenceChanged -= OnUserPreferenceChanged;
+
+        foreach (Window window in _windows)
+        {
+            window.Closed -= OnWindowClosed;
+            window.SourceInitialized -= OnWindowSourceInitialized;
+        }
+
+        _windows.Clear();
+    }
+
+    /// <summary>Тема приложений в настройках Windows.</summary>
+    private static AppTheme DetectSystemTheme()
+    {
+        try
+        {
+            using RegistryKey? key = Registry.CurrentUser.OpenSubKey(PersonalizeKey);
+            return key?.GetValue("AppsUseLightTheme") is int light && light == 0
+                ? AppTheme.Dark
+                : AppTheme.Light;
+        }
+        catch (Exception e) when (e is System.Security.SecurityException or UnauthorizedAccessException)
+        {
+            return AppTheme.Light;
+        }
+    }
+
+    private void OnSettingsChanged(object? sender, PropertyChangedEventArgs e)
+    {
+        if (e.PropertyName == nameof(AppSettings.Theme))
+        {
+            Apply();
+        }
+    }
+
+    // Windows сообщает о смене оформления не из потока интерфейса
+    private void OnUserPreferenceChanged(object? sender, UserPreferenceChangedEventArgs e) =>
+        Application.Current?.Dispatcher.InvokeAsync(Apply);
+
+    private void Apply()
+    {
+        AppTheme theme = _settings.Theme == AppTheme.System ? DetectSystemTheme() : _settings.Theme;
+        if (_palette is not null && theme == _current)
+        {
+            return;
+        }
+
+        _current = theme;
+
+        var next = new ResourceDictionary
+        {
+            Source = new Uri($"pack://application:,,,/Themes/{theme}.xaml", UriKind.Absolute),
+        };
+
+        ICollection<ResourceDictionary> dictionaries = Application.Current.Resources.MergedDictionaries;
+        dictionaries.Add(next);
+
+        if (_palette is not null)
+        {
+            dictionaries.Remove(_palette);
+        }
+
+        _palette = next;
+
+        foreach (Window window in _windows)
+        {
+            ApplyTitleBar(window);
+        }
+    }
+
+    private void ApplyTitleBar(Window window) =>
+        WindowThemeNative.SetDarkTitleBar(
+            new WindowInteropHelper(window).Handle,
+            _current == AppTheme.Dark);
+
+    private void OnWindowSourceInitialized(object? sender, EventArgs e)
+    {
+        if (sender is Window window)
+        {
+            window.SourceInitialized -= OnWindowSourceInitialized;
+            ApplyTitleBar(window);
+        }
+    }
+
+    private void OnWindowClosed(object? sender, EventArgs e)
+    {
+        if (sender is Window window)
+        {
+            window.Closed -= OnWindowClosed;
+            _windows.Remove(window);
+        }
+    }
+}