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// ==++==
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// ==--==
/*============================================================
**
** Class: ResourceFallbackManager
**
** <OWNER>Microsoft</OWNER>
**
**
** Purpose: Encapsulates CultureInfo fallback for resource
** lookup
**
**
===========================================================*/
using System;
using System.Collections;
using System.Collections.Generic;
#if FEATURE_CORECLR
using System.Diagnostics.Contracts;
#endif
using System.Globalization;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
namespace System.Resources
{
internal class ResourceFallbackManager : IEnumerable<CultureInfo>
{
private CultureInfo m_startingCulture;
private CultureInfo m_neutralResourcesCulture;
private bool m_useParents;
// Added but disabled from desktop in .NET 4.0, stayed disabled in .NET 4.5
#if FEATURE_CORECLR
// This is a cache of the thread, process, user, and OS-preferred fallback cultures.
// However, each thread may have a different value, and these may change during the
// lifetime of the process. So this cache must be verified each time we use it.
// Hence, we'll keep an array of strings for culture names & check it each time,
// but we'll really cache an array of CultureInfo's. Using thread-local statics
// as well to avoid differences across threads.
[ThreadStatic]
private static CultureInfo[] cachedOsFallbackArray;
#endif // FEATURE_CORECLR
internal ResourceFallbackManager(CultureInfo startingCulture, CultureInfo neutralResourcesCulture, bool useParents)
{
if (startingCulture != null)
{
m_startingCulture = startingCulture;
}
else
{
m_startingCulture = CultureInfo.CurrentUICulture;
}
m_neutralResourcesCulture = neutralResourcesCulture;
m_useParents = useParents;
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
// WARING: This function must be kept in sync with ResourceManager.GetFirstResourceSet()
public IEnumerator<CultureInfo> GetEnumerator()
{
bool reachedNeutralResourcesCulture = false;
// 1. starting culture chain, up to neutral
CultureInfo currentCulture = m_startingCulture;
do
{
if (m_neutralResourcesCulture != null && currentCulture.Name == m_neutralResourcesCulture.Name)
{
// Return the invariant culture all the time, even if the UltimateResourceFallbackLocation
// is a satellite assembly. This is fixed up later in ManifestBasedResourceGroveler::UltimateFallbackFixup.
yield return CultureInfo.InvariantCulture;
reachedNeutralResourcesCulture = true;
break;
}
yield return currentCulture;
currentCulture = currentCulture.Parent;
} while (m_useParents && !currentCulture.HasInvariantCultureName);
if (!m_useParents || m_startingCulture.HasInvariantCultureName)
{
yield break;
}
// Added but disabled from desktop in .NET 4.0, stayed disabled in .NET 4.5
#if FEATURE_CORECLR
#if FEATURE_LEGACYNETCF
if(!CompatibilitySwitches.IsAppEarlierThanWindowsPhone8)
{
#endif // FEATURE_LEGACYNETCF
// 2. user preferred cultures, omitting starting culture if tried already
// Compat note: For console apps, this API will return cultures like Arabic
// or Hebrew that are displayed right-to-left. These don't work with today's
// CMD.exe. Since not all apps can short-circuit RTL languages to look at
// US English resources, we're exposing an appcompat flag for this, to make the
// osFallbackArray an empty array, mimicing our V2 behavior. Apps should instead
// be using CultureInfo.GetConsoleFallbackUICulture, and then test whether that
// culture's code page can be displayed on the console, and if not, they should
// set their culture to their neutral resources language.
// Note: the app compat switch will omit the OS Preferred fallback culture.
// Compat note 2: This feature breaks certain apps dependent on fallback to neutral
// resources. See extensive note in GetResourceFallbackArray.
CultureInfo[] osFallbackArray = LoadPreferredCultures();
if (osFallbackArray != null)
{
foreach (CultureInfo ci in osFallbackArray)
{
// only have to check starting culture and immediate parent for now.
// in Dev10, revisit this policy.
if (m_startingCulture.Name != ci.Name && m_startingCulture.Parent.Name != ci.Name)
{
yield return ci;
}
}
}
#if FEATURE_LEGACYNETCF
}
#endif // FEATURE_LEGACYNETCF
#endif // FEATURE_CORECLR
// 3. invariant
// Don't return invariant twice though.
if (reachedNeutralResourcesCulture)
yield break;
yield return CultureInfo.InvariantCulture;
}
// Added but disabled from desktop in .NET 4.0, stayed disabled in .NET 4.5
#if FEATURE_CORECLR
private static CultureInfo[] LoadPreferredCultures()
{
// The list of preferred cultures includes thread, process, user, and OS
// information and may theoretically change every time we call it.
// The caching does save us some allocations - this complexity saved about
// 7% of the wall clock time on a US English machine, and may save more on non-English
// boxes (since the fallback list may be longer).
String[] cultureNames = GetResourceFallbackArray();
if (cultureNames == null)
return null;
bool useCachedNames = (cachedOsFallbackArray != null && cultureNames.Length == cachedOsFallbackArray.Length);
if (useCachedNames)
{
for (int i = 0; i < cultureNames.Length; i++)
{
if (!String.Equals(cultureNames[i], cachedOsFallbackArray[i].Name))
{
useCachedNames = false;
break;
}
}
}
if (useCachedNames)
return cachedOsFallbackArray;
cachedOsFallbackArray = LoadCulturesFromNames(cultureNames);
return cachedOsFallbackArray;
}
private static CultureInfo[] LoadCulturesFromNames(String[] cultureNames)
{
if (cultureNames == null)
return null;
CultureInfo[] cultures = new CultureInfo[cultureNames.Length];
int culturesIndex = 0;
for (int i = 0; i < cultureNames.Length; i++)
{
// get cached, read-only cultures to avoid excess allocations
cultures[culturesIndex] = CultureInfo.GetCultureInfo(cultureNames[i]);
// Note GetCultureInfo can return null for a culture name that we don't support on the current OS.
// Don't leave a null in the middle of the array.
if (!Object.ReferenceEquals(cultures[culturesIndex], null))
culturesIndex++;
}
// If we couldn't create a culture, return an array of the right length.
if (culturesIndex != cultureNames.Length)
{
CultureInfo[] ret = new CultureInfo[culturesIndex];
Array.Copy(cultures, ret, culturesIndex);
cultures = ret;
}
return cultures;
}
// Note: May return null.
[System.Security.SecuritySafeCritical] // auto-generated
private static String[] GetResourceFallbackArray()
{
// AppCompat note: We've added this feature for desktop V4 but we ripped it out
// before shipping V4. It shipped in SL 2 and SL 3. We preserved this behavior in SL 4
// for compat with previous Silverlight releases. We considered re-introducing this in .NET
// 4.5 for Windows 8 but chose not to because the Windows 8 immersive resources model
// has been redesigned from the ground up and we chose to support it (for portable libraries
// only) instead of further enhancing support for the classic resources model.
// ---------------------------------------------------------------------
//
// We have an appcompat problem that prevents us from adopting the ideal MUI model for
// culture fallback. Up until .NET Framework v4, our fallback was this:
//
// CurrentUICulture & parents Neutral
//
// We also had applications that took a dependency on falling back to neutral resources.
// IE, say an app is developed by US English developers - they may include English resources
// in the main assembly, not ship an "en" satellite assembly, and ship a French satellite.
// They may also omit the NeutralResourcesLanguageAttribute.
//
// Starting with Silverlight v2 and following advice from the MUI team, we wanted to call
// the OS's GetThreadPreferredUILanguages, inserting the results like this:
//
// CurrentUICulture & parents user-preferred fallback OS-preferred fallback Neutral
//
// This does not fit well for two reasons:
// 1) There is no concept of neutral resources in MUI
// 2) The user-preferred culture fallbacks make no sense in servers & non-interactive apps
// This leads to bad results on certain combinations of OS language installations, user
// settings, and applications built in certain styles. The OS-preferred fallback should
// be last, and the user-preferred fallback just breaks certain apps no matter where you put it.
//
// Necessary and sufficient conditions for an AppCompat bug (if we respected user & OS fallbacks):
// 1) A French OS (ie, you walk into an Internet café in Paris)
// 2) A .NET application whose neutral resources are authored in English.
// 3) The application did not provide an English satellite assembly (a common pattern).
// 4) The application is localized to French.
// 5) The user wants to read English, expressed in either of two ways:
// a. Changing Windows’ Display Language in the Regional Options Control Panel
// b. The application explicitly ASKS THE USER what language to display.
//
// Obviously the exact languages above can be interchanged a bit - I’m keeping this concrete.
// Also the NeutralResourcesLanguageAttribute will allow this to work, but usually we set it
// to en-US for our assemblies, meaning all other English cultures are broken.
//
// Workarounds:
// *) Use the NeutralResourcesLanguageAttribute and tell us that your neutral resources
// are in region-neutral English (en).
// *) Consider shipping a region-neutral English satellite assembly.
// Future work:
// 2) Consider a mechanism for individual assemblies to opt into wanting user-preferred fallback.
// They should ship their neutral resources in a satellite assembly, or use the
// NeutralResourcesLanguageAttribute to say their neutral resources are in a REGION-NEUTRAL
// language. An appdomain or process-wide flag may not be sufficient.
// 3) Ask Windows to clarify the scenario for the OS preferred fallback list, to decide whether
// we should probe there before or after looking at the neutral resources. If we move it
// to after the neutral resources, ask Windows to return a user-preferred fallback list
// without the OS preferred fallback included. This is a feature request for
// GetThreadPreferredUILanguages. We can muddle through without it by removing the OS
// preferred fallback cultures from end of the combined user + OS preferred fallback list, carefully.
// 4) Do not look at user-preferred fallback if Environment.UserInteractive is false. (IE,
// the Windows user who launches ASP.NET shouldn't determine how a web page gets
// localized - the server itself must respect the remote client's requested languages.)
// 6) Figure out what should happen in servers (ASP.NET, SQL, NT Services, etc).
//
// Done:
// 1) Got data from Windows on priority of supporting OS preferred fallback. We need to do it.
// Helps with consistency w/ Windows, and may be necessary for a long tail of other languages
// (ie, Windows has various degrees of localization support for ~135 languages, and fallbacks
// to certain languages is important.)
// 5) Revisited guidance for using the NeutralResourcesLanguageAttribute. Our docs should now say
// always pick a region-neutral language (ie, "en").
return CultureInfo.nativeGetResourceFallbackArray();
}
#endif // FEATURE_CORECLR
}
}
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