modified ThemeService

CursorLang/Services/ThemeService.cs

@@ -17,13 +17,24 @@ public sealed class ThemeService : IThemeService, IDisposable
         @"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();
@@ -90,7 +101,7 @@ public sealed class ThemeService : IThemeService, IDisposable
 
     private void Apply()
     {
-        AppTheme theme = _settings.Theme == AppTheme.System ? DetectSystemTheme() : _settings.Theme;
+        AppTheme theme = _settings.Theme == AppTheme.System ? _detectSystemTheme() : _settings.Theme;
         if (_palette is not null && theme == _current)
         {
             return;
@@ -100,7 +111,7 @@ public sealed class ThemeService : IThemeService, IDisposable
 
         var next = new ResourceDictionary
         {
-            Source = new Uri($"pack://application:,,,/Themes/{theme}.xaml", UriKind.Absolute),
+            Source = PaletteUri(theme),
         };
 
         ICollection<ResourceDictionary> dictionaries = Application.Current.Resources.MergedDictionaries;
@@ -119,6 +130,12 @@ public sealed class ThemeService : IThemeService, IDisposable
         }
     }
 
+    // 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
+    // application itself
+    internal static Uri PaletteUri(AppTheme theme) =>
+        new($"pack://application:,,,/CursorLang;component/Themes/{theme}.xaml", UriKind.Absolute);
+
     private void ApplyTitleBar(Window window) =>
         WindowThemeNative.SetDarkTitleBar(
             new WindowInteropHelper(window).Handle,