Add Simplified Chinese localization and language settings

README.md

@@ -39,6 +39,8 @@ of `codex.cmd` or `codex.exe`.
   including credits, spend controls, earned resets, token activity, and model-specific limits
   when Codex returns them
 - System, light, and dark themes with five preset accent colors selected from Settings
+- Automatic Windows-language selection with English fallback, plus English and Simplified
+  Chinese overrides in Settings
 - A movable, always-on-top desktop widget and a compact label beside the notification area
 - Live task activity dots based on official local Codex lifecycle hooks
 - Automatic refresh every two minutes plus live rate-limit notifications
@@ -66,9 +68,9 @@ subscription percentage.
 
 Select the `−` button to move the widget to the taskbar. Right-click the taskbar label or
 tray icon to refresh, change the display mode, open Settings, check for updates, or exit.
-The Settings window opens from the gear button on the widget too. Theme, accent color,
-widget layout, displayed limit, and Start with Windows changes apply as soon as they are
-selected.
+The Settings window opens from the gear button on the widget too. Language, theme, accent
+color, widget layout, displayed limit, and Start with Windows changes apply as soon as they
+are selected.
 
 ## Activity dots
 
@@ -101,6 +103,7 @@ The application writes only under `%LOCALAPPDATA%\CodexUsageWidget`:
 - `displayed-limit.txt`: selected summary limit
 - `theme.txt`: system, light, or dark theme preference
 - `accent-palette.txt`: selected preset accent color
+- `language.txt`: system, English, or Simplified Chinese language preference
 - `logs\codex-usage-widget-YYYYMMDD.log`: diagnostic logs retained for 14 days
 
 The widget displays ChatGPT and Codex subscription limits. It does not display OpenAI API

docs/ARCHITECTURE.md

@@ -42,7 +42,9 @@ tests/CodexUsageWidget.Tests/ Unit tests for parsing, formatting and persistence
 11. `AppThemeController` applies the saved system, light, or dark theme plus the selected
     accent palette, and observes Windows theme changes without leaking registry access into
     view code.
-12. `MainWindow` remains a window-lifecycle shell while the Settings window coordinates
+12. `AppLanguageController` resolves the saved system, English, or Simplified Chinese
+    preference, while standard .NET resources and a notifying WPF binding refresh existing UI.
+13. `MainWindow` remains a window-lifecycle shell while the Settings window coordinates
     activity-hook setup plus immediate theme, accent, widget-layout, displayed-limit, and Windows
     startup preferences. Focused user controls render compact, detailed, and repeated limit-row
     content.

src/CodexUsageWidget/App.xaml.cs

@@ -7,6 +7,7 @@
 using CodexUsageWidget.Infrastructure.Preview;
 using CodexUsageWidget.Infrastructure.Settings;
 using CodexUsageWidget.Infrastructure.Windows;
+using CodexUsageWidget.Localization;
 using CodexUsageWidget.Views;
 
 namespace CodexUsageWidget;
@@ -18,8 +19,20 @@ public partial class App : System.Windows.Application, IDisposable
     private FileLogger? _logger;
     private GlobalExceptionHandler? _exceptionHandler;
     private AppThemeController? _themeController;
+    private readonly AppLanguageController _languageController;
     private bool _disposed;
 
+    public App()
+        : this(new AppLanguageController(new LanguagePreferenceStore()))
+    {
+    }
+
+    public App(AppLanguageController languageController)
+    {
+        ArgumentNullException.ThrowIfNull(languageController);
+        _languageController = languageController;
+    }
+
     protected override void OnStartup(StartupEventArgs e)
     {
         base.OnStartup(e);
@@ -84,7 +97,8 @@ protected override void OnStartup(StartupEventArgs e)
                 new DisplayedLimitPreferenceStore(),
                 startupRegistrationService,
                 new TrayIconService(),
-                _themeController);
+                _themeController,
+                _languageController);
             MainWindow = window;
             activityMonitor.StartAsync().GetAwaiter().GetResult();
             window.Show();
@@ -100,8 +114,8 @@ protected override void OnStartup(StartupEventArgs e)
             activityMonitor?.DisposeAsync().AsTask().GetAwaiter().GetResult();
             _logger.LogError("Application startup failed.", ex);
             System.Windows.MessageBox.Show(
-                "Codex Usage Widget could not start. See the log under " + AppPaths.LogDirectory,
-                "Codex Usage Widget",
+                Strings.Format("App_StartupFailure", AppPaths.LogDirectory),
+                Strings.Get("App_Name"),
                 MessageBoxButton.OK,
                 MessageBoxImage.Error);
             Shutdown(-1);

src/CodexUsageWidget/Application/UsageMonitor.cs

@@ -1,4 +1,5 @@
 using CodexUsageWidget.Domain;
+using CodexUsageWidget.Localization;
 
 namespace CodexUsageWidget.Application;
 
@@ -67,7 +68,7 @@ public async Task RefreshAsync(CancellationToken cancellationToken = default)
         }
         catch (OperationCanceledException) when (!_lifetime.IsCancellationRequested)
         {
-            RefreshFailed?.Invoke("Codex did not respond in time.");
+            RefreshFailed?.Invoke(Strings.Get("Error_ResponseTimeout"));
         }
         catch (Exception ex)
         {

src/CodexUsageWidget/Application/UsageTextFormatter.cs

@@ -1,3 +1,6 @@
+using System.Globalization;
+using CodexUsageWidget.Localization;
+
 namespace CodexUsageWidget.Application;
 
 public static class UsageTextFormatter
@@ -7,32 +10,38 @@ public static string ToFriendlyError(string message)
         if (message.Contains("not found", StringComparison.OrdinalIgnoreCase) ||
             message.Contains("cannot find", StringComparison.OrdinalIgnoreCase))
         {
-            return "Codex CLI was not found on PATH.";
+            return Strings.Get("Error_CliNotFound");
         }
 
         if (message.Contains("login", StringComparison.OrdinalIgnoreCase) ||
             message.Contains("unauthorized", StringComparison.OrdinalIgnoreCase))
         {
-            return "Run codex login, then refresh.";
+            return Strings.Get("Error_LoginRequired");
         }
 
-        return message.Length > 100 ? message[..100] + "…" : message;
+        var detail = message.Length > 100 ? message[..100] + "…" : message;
+        return Strings.Format("Error_Unexpected", detail);
     }
 
     public static string FormatReset(DateTimeOffset reset, DateTimeOffset? now = null)
     {
         var remaining = reset - (now ?? DateTimeOffset.Now);
         if (remaining <= TimeSpan.Zero)
         {
-            return "now";
+            return Strings.Get("Usage_ResetsNow");
         }
 
         if (remaining < TimeSpan.FromHours(24))
         {
-            return $"in {Math.Max(1, (int)Math.Ceiling(remaining.TotalHours))}h · {reset:HH:mm}";
+            return Strings.Format(
+                "Usage_ResetsInHours",
+                Math.Max(1, (int)Math.Ceiling(remaining.TotalHours)),
+                reset.ToString("HH:mm", CultureInfo.CurrentCulture));
         }
 
-        return $"{reset:ddd HH:mm}";
+        return Strings.Format(
+            "Usage_ResetsAt",
+            reset.ToString("ddd HH:mm", CultureInfo.CurrentCulture));
     }
 
     public static string ColorForRemaining(double remainingPercent) => remainingPercent switch

src/CodexUsageWidget/Infrastructure/AppPaths.cs

@@ -18,6 +18,8 @@ public static class AppPaths
 
     public static string ThemePreferenceFile => Path.Combine(LocalDataDirectory, "theme.txt");
 
+    public static string LanguagePreferenceFile => Path.Combine(LocalDataDirectory, "language.txt");
+
     public static string AccentPaletteFile => Path.Combine(LocalDataDirectory, "accent-palette.txt");
 
     public static string LogDirectory => Path.Combine(LocalDataDirectory, "logs");

src/CodexUsageWidget/Infrastructure/Codex/Hooks/CodexActivityHookSetupService.cs

@@ -70,7 +70,7 @@ public async Task<ActivityHookSetupStatus> GetStatusAsync(
         {
             return new ActivityHookSetupStatus(
                 ActivityHookSetupState.InstalledStatusUnavailable,
-                $"Codex could not report hook trust status: {ex.Message}");
+                ex.Message);
         }
     }
 
@@ -123,8 +123,6 @@ private static ActivityHookSetupStatus FromTrustEvaluation(
                 new ActivityHookSetupStatus(ActivityHookSetupState.Active),
             CodexHookTrustEvaluation.Modified =>
                 new ActivityHookSetupStatus(ActivityHookSetupState.Modified),
-            _ => new ActivityHookSetupStatus(
-                ActivityHookSetupState.InstalledStatusUnavailable,
-                "The hook definitions are installed, but Codex did not report all expected hooks.")
+            _ => new ActivityHookSetupStatus(ActivityHookSetupState.InstalledStatusUnavailable)
         };
 }

src/CodexUsageWidget/Infrastructure/Settings/LanguagePreference.cs

@@ -0,0 +1,8 @@
+namespace CodexUsageWidget.Infrastructure.Settings;
+
+public enum LanguagePreference
+{
+    System,
+    English,
+    SimplifiedChinese
+}

src/CodexUsageWidget/Infrastructure/Settings/LanguagePreferenceResolver.cs

@@ -0,0 +1,30 @@
+using System.Globalization;
+
+namespace CodexUsageWidget.Infrastructure.Settings;
+
+public static class LanguagePreferenceResolver
+{
+    public static LanguagePreference Resolve(
+        LanguagePreference preference,
+        CultureInfo uiCulture) => preference switch
+        {
+            LanguagePreference.English => LanguagePreference.English,
+            LanguagePreference.SimplifiedChinese => LanguagePreference.SimplifiedChinese,
+            _ => IsSimplifiedChinese(uiCulture)
+                ? LanguagePreference.SimplifiedChinese
+                : LanguagePreference.English
+        };
+
+    private static bool IsSimplifiedChinese(CultureInfo culture)
+    {
+        for (var current = culture; !string.IsNullOrEmpty(current.Name); current = current.Parent)
+        {
+            if (string.Equals(current.Name, "zh-Hans", StringComparison.OrdinalIgnoreCase))
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

src/CodexUsageWidget/Infrastructure/Settings/LanguagePreferenceStore.cs

@@ -0,0 +1,56 @@
+using System.IO;
+
+namespace CodexUsageWidget.Infrastructure.Settings;
+
+public sealed class LanguagePreferenceStore
+{
+    private readonly string _path;
+
+    public LanguagePreferenceStore(string? path = null)
+    {
+        _path = path ?? AppPaths.LanguagePreferenceFile;
+    }
+
+    public LanguagePreference Load()
+    {
+        try
+        {
+            return File.ReadAllText(_path).Trim().ToLowerInvariant() switch
+            {
+                "english" => LanguagePreference.English,
+                "simplified-chinese" => LanguagePreference.SimplifiedChinese,
+                _ => LanguagePreference.System
+            };
+        }
+        catch (IOException)
+        {
+            return LanguagePreference.System;
+        }
+        catch (UnauthorizedAccessException)
+        {
+            return LanguagePreference.System;
+        }
+    }
+
+    public void Save(LanguagePreference preference)
+    {
+        try
+        {
+            Directory.CreateDirectory(Path.GetDirectoryName(_path)!);
+            File.WriteAllText(
+                _path,
+                preference switch
+                {
+                    LanguagePreference.English => "english",
+                    LanguagePreference.SimplifiedChinese => "simplified-chinese",
+                    _ => "system"
+                });
+        }
+        catch (IOException)
+        {
+        }
+        catch (UnauthorizedAccessException)
+        {
+        }
+    }
+}