Allow TimeZoneInfo display names to use any of the installed Windows languages

src/libraries/Common/src/Interop/Windows/Kernel32/Interop.MUI.cs

@@ -7,9 +7,10 @@ internal static partial class Interop
 {
  internal static partial class Kernel32
  {
- internal const uint MUI_PREFERRED_UI_LANGUAGES = 0x10;
+ internal const uint MUI_USER_PREFERRED_UI_LANGUAGES = 0x10;
+ internal const uint MUI_USE_INSTALLED_LANGUAGES = 0x20;
 
  [DllImport(Libraries.Kernel32, CharSet = CharSet.Unicode, SetLastError = true, ExactSpelling = true)]
- internal static extern unsafe bool GetFileMUIPath(uint dwFlags, string pcwszFilePath, char* pwszLanguage, ref int pcchLanguage, char* pwszFileMUIPath, ref int pcchFileMUIPath, ref long pululEnumerator);
+ internal static extern unsafe bool GetFileMUIPath(uint dwFlags, string pcwszFilePath, char* pwszLanguage, ref uint pcchLanguage, char* pwszFileMUIPath, ref uint pcchFileMUIPath, ref ulong pululEnumerator);
  }
 }

src/libraries/System.Private.CoreLib/src/System/TimeZoneInfo.Win32.cs

@@ -36,6 +36,8 @@ public sealed partial class TimeZoneInfo
  private const int MaxKeyLength = 255;
  private const string InvariantUtcStandardDisplayName = "Coordinated Universal Time";
 
+ private static readonly Dictionary<string, string> s_FileMuiPathCache = new();
+
  private sealed partial class CachedData
  {
  private static TimeZoneInfo GetCurrentOneYearLocal()
@@ -736,6 +738,102 @@ private static bool TryCompareTimeZoneInformationToRegistry(in TIME_ZONE_INFORMA
  }
  }
 
+ /// <summary>
+ /// Helper function for getting the MUI path for a given resource and culture, using a cache to prevent duplicating work.
+ /// Searches the installed OS languages for either an exact matching culture, or one that has the same parent.
+ /// If not found, uses the preferred default OS UI language, to align with prior behavior.
+ /// </summary>
+ private static string GetCachedFileMuiPath(string filePath, CultureInfo cultureInfo)
+ {
+ string? result;
+ string cacheKey = $"{cultureInfo.Name};{filePath}";
+
+ lock (s_FileMuiPathCache)
+ {
+ if (s_FileMuiPathCache.TryGetValue(cacheKey, out result))
+ {
+ return result;
+ }
+ }
+
+ result = GetFileMuiPath(filePath, cultureInfo);
+
+ lock (s_FileMuiPathCache)
+ {
+ s_FileMuiPathCache.TryAdd(cacheKey, result);
+ }
+
+ return result;
+ }
+
+ /// <summary>
+ /// Helper function for getting the MUI path for a given resource and culture.
+ /// Searches the installed OS languages for either an exact matching culture, or one that has the same parent.
+ /// If not found, uses the preferred default OS UI language, to align with prior behavior.
+ /// </summary>
+ private static unsafe string GetFileMuiPath(string filePath, CultureInfo cultureInfo)
+ {
+ char* fileMuiPath = stackalloc char[Interop.Kernel32.MAX_PATH];
+ char* language = stackalloc char[Interop.Kernel32.LOCALE_NAME_MAX_LENGTH];
+ uint fileMuiPathLength = Interop.Kernel32.MAX_PATH;
+ uint languageLength = Interop.Kernel32.LOCALE_NAME_MAX_LENGTH;
+ ulong enumerator = 0;
+
+ while (true)
+ {
+ // Search all installed languages. The enumerator is re-used between loop iterations.
+ bool succeeded = Interop.Kernel32.GetFileMUIPath(
+ Interop.Kernel32.MUI_USE_INSTALLED_LANGUAGES,
+ filePath, language, ref languageLength,
+ fileMuiPath, ref fileMuiPathLength, ref enumerator);
+
+ if (!succeeded)
+ {
+ // Recurse to search using the parent of the desired culture.
+ if (cultureInfo.Parent.Name != string.Empty)
+ {
+ return GetFileMuiPath(filePath, cultureInfo.Parent);
+ }
+
+ // Final fallback, using the preferred installed UI language.
+ enumerator = 0;
+ succeeded = Interop.Kernel32.GetFileMUIPath(
+ Interop.Kernel32.MUI_USER_PREFERRED_UI_LANGUAGES,
+ filePath, language, ref languageLength,
+ fileMuiPath, ref fileMuiPathLength, ref enumerator);
+
+ if (succeeded)
+ {
+ return new string(fileMuiPath);
+ }
+
+ // Shouldn't get here, as there's always at least one language installed.
+ return string.Empty;
+ }
+
+ // Lookup succeeded. Check for exact match to the desired culture.
+ var lang = new string(language);
+ if (string.Equals(lang, cultureInfo.Name, StringComparison.OrdinalIgnoreCase))
+ {
+ return new string(fileMuiPath);
+ }
+
+ // Check for match of any parent of the language returned to the desired culture.
+ var ci = CultureInfo.GetCultureInfo(lang);
+ while (ci.Parent.Name != string.Empty)
+ {
+ if (ci.Parent.Name.Equals(cultureInfo.Name, StringComparison.OrdinalIgnoreCase))
+ {
+ return new string(fileMuiPath);
+ }
+
+ ci = ci.Parent;
+ }
+
+ // Not found yet. Continue with next iteration.
+ }
+ }
+
  /// <summary>
  /// Helper function for retrieving a localized string resource via MUI.
  /// The function expects a string in the form: "@resource.dll, -123"
@@ -746,13 +844,16 @@ private static bool TryCompareTimeZoneInformationToRegistry(in TIME_ZONE_INFORMA
  /// If a localized resource file exists, we LoadString resource ID "123" and
  /// return it to our caller.
  /// </summary>
- private static string TryGetLocalizedNameByMuiNativeResource(string resource)
+ private static string GetLocalizedNameByMuiNativeResource(string resource, CultureInfo? cultureInfo = null)
  {
  if (string.IsNullOrEmpty(resource))
  {
  return string.Empty;
  }
 
+ // Use the current UI culture when culture not specified
+ cultureInfo ??= CultureInfo.CurrentUICulture;
+
  // parse "@tzres.dll, -100"
  //
  // filePath = "C:\Windows\System32\tzres.dll"
@@ -782,34 +883,23 @@ private static string TryGetLocalizedNameByMuiNativeResource(string resource)
  return string.Empty;
  }
 
- if (!int.TryParse(resources[1], NumberStyles.Integer, CultureInfo.InvariantCulture, out int resourceId))
+ // Get the MUI File Path
+ string fileMuiPath = GetCachedFileMuiPath(filePath, cultureInfo);
+ if (fileMuiPath == string.Empty)
  {
+ // not likely, but we could not resolve a MUI path
  return string.Empty;
  }
- resourceId = -resourceId;
 
- try
- {
- unsafe
- {
- char* fileMuiPath = stackalloc char[Interop.Kernel32.MAX_PATH];
- int fileMuiPathLength = Interop.Kernel32.MAX_PATH;
- int languageLength = 0;
- long enumerator = 0;
-
- bool succeeded = Interop.Kernel32.GetFileMUIPath(
- Interop.Kernel32.MUI_PREFERRED_UI_LANGUAGES,
- filePath, null /* language */, ref languageLength,
- fileMuiPath, ref fileMuiPathLength, ref enumerator);
- return succeeded ?
- TryGetLocalizedNameByNativeResource(new string(fileMuiPath, 0, fileMuiPathLength), resourceId) :
- string.Empty;
- }
- }
- catch (EntryPointNotFoundException)
+ // Get the resource ID
+ if (!int.TryParse(resources[1], NumberStyles.Integer, CultureInfo.InvariantCulture, out int resourceId))
  {
  return string.Empty;
  }
+ resourceId = -resourceId;
+
+ // Finally, get the resource from the resource path
+ return GetLocalizedNameByNativeResource(fileMuiPath, resourceId);
  }
 
  /// <summary>
@@ -819,7 +909,7 @@ private static string TryGetLocalizedNameByMuiNativeResource(string resource)
  /// "resource.dll" is a language-specific resource DLL.
  /// If the localized resource DLL exists, LoadString(resource) is returned.
  /// </summary>
- private static unsafe string TryGetLocalizedNameByNativeResource(string filePath, int resource)
+ private static unsafe string GetLocalizedNameByNativeResource(string filePath, int resource)
  {
  IntPtr handle = IntPtr.Zero;
  try
@@ -869,17 +959,17 @@ private static void GetLocalizedNamesByRegistryKey(RegistryKey key, out string?
  // try to load the strings from the native resource DLL(s)
  if (!string.IsNullOrEmpty(displayNameMuiResource))
  {
- displayName = TryGetLocalizedNameByMuiNativeResource(displayNameMuiResource);
+ displayName = GetLocalizedNameByMuiNativeResource(displayNameMuiResource);
  }
 
  if (!string.IsNullOrEmpty(standardNameMuiResource))
  {
- standardName = TryGetLocalizedNameByMuiNativeResource(standardNameMuiResource);
+ standardName = GetLocalizedNameByMuiNativeResource(standardNameMuiResource);
  }
 
  if (!string.IsNullOrEmpty(daylightNameMuiResource))
  {
- daylightName = TryGetLocalizedNameByMuiNativeResource(daylightNameMuiResource);
+ daylightName = GetLocalizedNameByMuiNativeResource(daylightNameMuiResource);
  }
 
  // fallback to using the standard registry keys
@@ -901,7 +991,7 @@ private static void GetLocalizedNamesByRegistryKey(RegistryKey key, out string?
  /// Helper function that takes a string representing a time_zone_name registry key name
  /// and returns a TimeZoneInfo instance.
  /// </summary>
- private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo? value, out Exception? e)
+ private static TimeZoneInfoResult GetTimeZoneFromLocalMachine(string id, out TimeZoneInfo? value, out Exception? e)
  {
  e = null;
 
@@ -1003,7 +1093,7 @@ private static string GetUtcStandardDisplayName()
  // try to load the string from the native resource DLL(s)
  if (!string.IsNullOrEmpty(standardNameMuiResource))
  {
- standardDisplayName = TryGetLocalizedNameByMuiNativeResource(standardNameMuiResource);
+ standardDisplayName = GetLocalizedNameByMuiNativeResource(standardNameMuiResource);
  }
 
  // fallback to using the standard registry key

src/libraries/System.Runtime/tests/System/TimeZoneInfoTests.cs

@@ -7,6 +7,7 @@
 using System.Diagnostics;
 using System.IO;
 using System.Linq;
+using System.Runtime.InteropServices;
 using System.Runtime.Serialization.Formatters.Binary;
 using System.Text.RegularExpressions;
 using Microsoft.DotNet.RemoteExecutor;
@@ -2720,7 +2721,30 @@ public static void TestNameWithInvariantCulture()
  Assert.True(pacific.DisplayName.IndexOf("Pacific", StringComparison.OrdinalIgnoreCase) >= 0, $"'{pacific.DisplayName}' is not the expected display name for Pacific time zone");
 
  }).Dispose();
+ }
+
+ private static bool CanTestWindowsNlsDisplayNames => s_isWindows && RemoteExecutor.IsSupported && WindowsUILanguageHelper.GetInstalledWin32CulturesWithUniqueLanguages().Length > 1;
+
+ [PlatformSpecific(TestPlatforms.Windows)]
+ [ConditionalFact(nameof(CanTestWindowsNlsDisplayNames))]
+ public static void TestWindowsNlsDisplayNames()
+ {
+ RemoteExecutor.Invoke(() =>
+ {
+ var cultures = WindowsUILanguageHelper.GetInstalledWin32CulturesWithUniqueLanguages();
+
+ CultureInfo.CurrentUICulture = cultures[0];
+ TimeZoneInfo.ClearCachedData();
+ TimeZoneInfo tz1 = TimeZoneInfo.FindSystemTimeZoneById(s_strPacific);
+
+ CultureInfo.CurrentUICulture = cultures[1];
+ TimeZoneInfo.ClearCachedData();
+ TimeZoneInfo tz2 = TimeZoneInfo.FindSystemTimeZoneById(s_strPacific);
 
+ Assert.True(tz1.StandardName != tz2.DisplayName, $"The display name '{tz1.DisplayName}' should be different between {cultures[0].Name} and {cultures[1].Name}.");
+ Assert.True(tz1.StandardName != tz2.StandardName, $"The standard name '{tz1.StandardName}' should be different between {cultures[0].Name} and {cultures[1].Name}.");
+ Assert.True(tz1.StandardName != tz2.DaylightName, $"The daylight name '{tz1.DaylightName}' should be different between {cultures[0].Name} and {cultures[1].Name}.");
+ }).Dispose();
  }
 
  [Theory]
@@ -2983,5 +3007,51 @@ private static void VerifyCustomTimeZoneException<TException>(string id, TimeSpa
  }
  });
  }
+
+ // This helper class is used to retrieve information about installed OS languages from Windows.
+ // It should only be using in Windows platform-specific tests.
+ private static class WindowsUILanguageHelper
+ {
+ public static CultureInfo[] GetInstalledWin32CulturesWithUniqueLanguages() =>
+ GetInstalledWin32Cultures()
+ .GroupBy(c => c.TwoLetterISOLanguageName)
+ .Select(g => g.First())
+ .ToArray();
+
+ public static CultureInfo[] GetInstalledWin32Cultures()
+ {
+ var context = new EnumContext();
+ EnumUILanguagesProc proc = EnumUiLanguagesCallback;
+
+ EnumUILanguages(proc, MUI_ALL_INSTALLED_LANGUAGES | MUI_LANGUAGE_NAME, context);
+ GC.KeepAlive(proc);
+ return context.InstalledCultures.ToArray();
+ }
+
+ private static bool EnumUiLanguagesCallback(IntPtr lpUiLanguageString, EnumContext lParam)
+ {
+ var cultureName = Marshal.PtrToStringUni(lpUiLanguageString);
+ if (cultureName != null)
+ {
+ lParam.InstalledCultures.Add(CultureInfo.GetCultureInfo(cultureName));
+ return true;
+ }
+
+ return false;
+ }
+
+ private const uint MUI_LANGUAGE_NAME = 0x8;
+ private const uint MUI_ALL_INSTALLED_LANGUAGES = 0x20;
+
+ [DllImport("Kernel32.dll", CharSet = CharSet.Auto)]
+ private static extern bool EnumUILanguages(EnumUILanguagesProc lpUILanguageEnumProc, uint dwFlags, EnumContext lParam);
+
+ private delegate bool EnumUILanguagesProc(IntPtr lpUILanguageString, EnumContext lParam);
+
+ private class EnumContext
+ {
+ public readonly List<CultureInfo> InstalledCultures = new();
+ }
+ }
  }
 }