lightweight variant (#1)

Reviewed-on: #1 Co-authored-by: Aleksandr Neychev <alexnejchev73@gmail.com>
2026-08-12 13:37:30 +00:00
parent a0d3098fe4
commit 55ac8e6556
147 changed files with 4055 additions and 2349 deletions
@@ -0,0 +1,164 @@
+using System.ComponentModel;
+using System.Windows;
+using System.Windows.Interop;
+using CursorLang.Core.Models;
+using CursorLang.Settings.Interop;
+using Microsoft.Win32;
+
+namespace CursorLang.Settings.Services;
+
+/// <summary>
+/// Keeps the palette of the chosen theme in the application resources and swaps it
+/// when the setting changes — the windows are recoloured without a restart.
+/// </summary>
+public sealed class ThemeService : IThemeService, IDisposable
+{
+    private const string PersonalizeKey =
+        @"Software\Microsoft\Windows\CurrentVersion\Themes\Personalize";
+
+    private readonly AppSettings _settings;
+    private readonly Func<AppTheme> _detectSystemTheme;
+    private readonly List<Window> _windows = [];
+    private ResourceDictionary? _palette;
+    private AppTheme _current;
+
+    public ThemeService(AppSettings settings)
+        : this(settings, DetectSystemTheme)
+    {
+    }
+
+    /// <summary>
+    /// Takes the source of the system theme explicitly: in tests it is not the registry
+    /// that provides it.
+    /// </summary>
+    internal ThemeService(AppSettings settings, Func<AppTheme> detectSystemTheme)
+    {
+        _settings = settings;
+        _detectSystemTheme = detectSystemTheme;
+        _settings.PropertyChanged += OnSettingsChanged;
+        SystemEvents.UserPreferenceChanged += OnUserPreferenceChanged;
+        Apply();
+    }
+
+    /// <summary>The theme the user sees: <c>System</c> is already resolved here.</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>The app theme from the Windows settings.</summary>
+    internal 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 reports a theme change from outside the interface thread
+    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 = PaletteUri(theme),
+        };
+
+        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);
+        }
+    }
+
+    // The assembly name in the address is there on purpose: without it the dictionary
+    // is looked up in the assembly the process started from, which is not always the
+    // one holding the palettes. It is taken from the type rather than spelt out —
+    // the name of this assembly has changed once already, and a wrong one here is a
+    // crash on startup rather than a build error
+    internal static Uri PaletteUri(AppTheme theme) => new(
+        $"pack://application:,,,/{typeof(ThemeService).Assembly.GetName().Name};component/Themes/{theme}.xaml",
+        UriKind.Absolute);
+
+    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);
+        }
+    }
+}