Use Windows Display Language (flutter#43341)

Get the Windows Display Language for locale selection instead of the
preferred languages.

flutter/flutter#129786

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- [x] I read the [Tree Hygiene] wiki page, which explains my
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- [x] I read and followed the [Flutter Style Guide] and the [C++,
Objective-C, Java style guides].
- [x] I listed at least one issue that this PR fixes in the description
above.
- [x] I added new tests to check the change I am making or feature I am
adding, or Hixie said the PR is test-exempt. See [testing the engine]
for instructions on writing and running engine tests.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [ ] I signed the [CLA].
- [x] All existing and new tests are passing.

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on [Discord].

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---------

Co-authored-by: Loïc Sharma <[email protected]>

Author: yaakovschectman

ci/licenses_golden/licenses_flutter

@@ -3235,8 +3235,6 @@ ORIGIN: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.cc + .
 ORIGIN: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/windows_proc_table.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/windows_proc_table.h + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/shell/platform/windows/windows_registry.cc + ../../../flutter/LICENSE
-ORIGIN: ../../../flutter/shell/platform/windows/windows_registry.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/platform/windows/windowsx_shim.h + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/profiling/sampling_profiler.cc + ../../../flutter/LICENSE
 ORIGIN: ../../../flutter/shell/profiling/sampling_profiler.h + ../../../flutter/LICENSE
@@ -5939,8 +5937,6 @@ FILE: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.cc
 FILE: ../../../flutter/shell/platform/windows/windows_lifecycle_manager.h
 FILE: ../../../flutter/shell/platform/windows/windows_proc_table.cc
 FILE: ../../../flutter/shell/platform/windows/windows_proc_table.h
-FILE: ../../../flutter/shell/platform/windows/windows_registry.cc
-FILE: ../../../flutter/shell/platform/windows/windows_registry.h
 FILE: ../../../flutter/shell/platform/windows/windowsx_shim.h
 FILE: ../../../flutter/shell/profiling/sampling_profiler.cc
 FILE: ../../../flutter/shell/profiling/sampling_profiler.h

shell/platform/windows/BUILD.gn

@@ -107,8 +107,6 @@ source_set("flutter_windows_source") {
     "windows_lifecycle_manager.h",
     "windows_proc_table.cc",
     "windows_proc_table.h",
-    "windows_registry.cc",
-    "windows_registry.h",
     "windowsx_shim.h",
   ]
 

shell/platform/windows/flutter_windows_engine.cc

@@ -156,12 +156,9 @@ FlutterLocale CovertToFlutterLocale(const LanguageInfo& info) {
 
 }  // namespace
 
-FlutterWindowsEngine::FlutterWindowsEngine(
-    const FlutterProjectBundle& project,
-    std::unique_ptr<WindowsRegistry> registry)
+FlutterWindowsEngine::FlutterWindowsEngine(const FlutterProjectBundle& project)
     : project_(std::make_unique<FlutterProjectBundle>(project)),
       aot_data_(nullptr, nullptr),
-      windows_registry_(std::move(registry)),
       lifecycle_manager_(std::make_unique<WindowsLifecycleManager>(this)) {
   embedder_api_.struct_size = sizeof(FlutterEngineProcTable);
   FlutterEngineGetProcAddresses(&embedder_api_);
@@ -572,7 +569,7 @@ void FlutterWindowsEngine::SetLifecycleState(flutter::AppLifecycleState state) {
 
 void FlutterWindowsEngine::SendSystemLocales() {
   std::vector<LanguageInfo> languages =
-      GetPreferredLanguageInfo(*windows_registry_);
+      GetPreferredLanguageInfo(windows_proc_table_);
   std::vector<FlutterLocale> flutter_locales;
   flutter_locales.reserve(languages.size());
   for (const auto& info : languages) {

shell/platform/windows/flutter_windows_engine.h

@@ -37,7 +37,7 @@
 #include "flutter/shell/platform/windows/window_proc_delegate_manager.h"
 #include "flutter/shell/platform/windows/window_state.h"
 #include "flutter/shell/platform/windows/windows_lifecycle_manager.h"
-#include "flutter/shell/platform/windows/windows_registry.h"
+#include "flutter/shell/platform/windows/windows_proc_table.h"
 #include "third_party/rapidjson/include/rapidjson/document.h"
 
 namespace flutter {
@@ -77,13 +77,8 @@ static void WindowsPlatformThreadPrioritySetter(
 // run in headless mode.
 class FlutterWindowsEngine {
  public:
-  // Creates a new Flutter engine with an injectible windows registry.
-  FlutterWindowsEngine(const FlutterProjectBundle& project,
-                       std::unique_ptr<WindowsRegistry> windows_registry);
-
   // Creates a new Flutter engine object configured to run |project|.
-  explicit FlutterWindowsEngine(const FlutterProjectBundle& project)
-      : FlutterWindowsEngine(project, std::make_unique<WindowsRegistry>()) {}
+  explicit FlutterWindowsEngine(const FlutterProjectBundle& project);
 
   virtual ~FlutterWindowsEngine();
 
@@ -405,12 +400,11 @@ class FlutterWindowsEngine {
   // The on frame drawn callback.
   fml::closure next_frame_callback_;
 
-  // Wrapper providing Windows registry access.
-  std::unique_ptr<WindowsRegistry> windows_registry_;
-
   // Handler for top level window messages.
   std::unique_ptr<WindowsLifecycleManager> lifecycle_manager_;
 
+  WindowsProcTable windows_proc_table_;
+
   FML_DISALLOW_COPY_AND_ASSIGN(FlutterWindowsEngine);
 };
 

shell/platform/windows/system_utils.cc

@@ -13,8 +13,9 @@
 namespace flutter {
 
 std::vector<LanguageInfo> GetPreferredLanguageInfo(
-    const WindowsRegistry& registry) {
-  std::vector<std::wstring> languages = GetPreferredLanguages(registry);
+    const WindowsProcTable& windows_proc_table) {
+  std::vector<std::wstring> languages =
+      GetPreferredLanguages(windows_proc_table);
   std::vector<LanguageInfo> language_info;
   language_info.reserve(languages.size());
 
@@ -24,63 +25,29 @@ std::vector<LanguageInfo> GetPreferredLanguageInfo(
   return language_info;
 }
 
-std::wstring GetPreferredLanguagesFromRegistry(const WindowsRegistry& registry,
-                                               ULONG buffer_size) {
-  std::wstring buffer(buffer_size, '\0');
-  if (registry.GetRegistryValue(HKEY_CURRENT_USER, kGetPreferredLanguageRegKey,
-                                kGetPreferredLanguageRegValue,
-                                RRF_RT_REG_MULTI_SZ, NULL, buffer.data(),
-                                &buffer_size) != ERROR_SUCCESS) {
-    return std::wstring();
-  }
-  return buffer;
-}
-
-std::wstring GetPreferredLanguagesFromMUI() {
-  ULONG buffer_size;
+std::wstring GetPreferredLanguagesFromMUI(
+    const WindowsProcTable& windows_proc_table) {
+  ULONG buffer_size = 0;
   ULONG count = 0;
   DWORD flags = MUI_LANGUAGE_NAME | MUI_UI_FALLBACK;
-  if (!GetThreadPreferredUILanguages(flags, &count, nullptr, &buffer_size)) {
+  if (!windows_proc_table.GetThreadPreferredUILanguages(flags, &count, nullptr,
+                                                        &buffer_size)) {
     return std::wstring();
   }
   std::wstring buffer(buffer_size, '\0');
-  if (!GetThreadPreferredUILanguages(flags, &count, buffer.data(),
-                                     &buffer_size)) {
+  if (!windows_proc_table.GetThreadPreferredUILanguages(
+          flags, &count, buffer.data(), &buffer_size)) {
     return std::wstring();
   }
   return buffer;
 }
 
 std::vector<std::wstring> GetPreferredLanguages(
-    const WindowsRegistry& registry) {
+    const WindowsProcTable& windows_proc_table) {
   std::vector<std::wstring> languages;
-  BOOL languages_from_registry = TRUE;
-  ULONG buffer_size = 0;
-  ULONG count = 0;
-  DWORD flags = MUI_LANGUAGE_NAME | MUI_UI_FALLBACK;
-
-  // Determine where languages are defined and get buffer length
-  if (registry.GetRegistryValue(HKEY_CURRENT_USER, kGetPreferredLanguageRegKey,
-                                kGetPreferredLanguageRegValue,
-                                RRF_RT_REG_MULTI_SZ, NULL, NULL,
-                                &buffer_size) != ERROR_SUCCESS) {
-    languages_from_registry = FALSE;
-  }
-
-  // Multi-string must be at least 3-long if non-empty,
-  // as a multi-string is terminated with 2 nulls.
-  //
-  // See:
-  // https://learn.microsoft.com/windows/win32/sysinfo/registry-value-types
-  if (languages_from_registry && buffer_size < 3) {
-    languages_from_registry = FALSE;
-  }
 
   // Initialize the buffer
-  std::wstring buffer =
-      languages_from_registry
-          ? GetPreferredLanguagesFromRegistry(registry, buffer_size)
-          : GetPreferredLanguagesFromMUI();
+  std::wstring buffer = GetPreferredLanguagesFromMUI(windows_proc_table);
 
   // Extract the individual languages from the buffer.
   size_t start = 0;

shell/platform/windows/system_utils.h

@@ -10,7 +10,7 @@
 #include <string>
 #include <vector>
 
-#include "flutter/shell/platform/windows/windows_registry.h"
+#include "flutter/shell/platform/windows/windows_proc_table.h"
 
 namespace flutter {
 
@@ -29,20 +29,17 @@ struct LanguageInfo {
 // Returns the list of user-preferred languages, in preference order,
 // parsed into LanguageInfo structures.
 std::vector<LanguageInfo> GetPreferredLanguageInfo(
-    const WindowsRegistry& registry);
-
-// Retrieve the preferred languages from the registry.
-std::wstring GetPreferredLanguagesFromRegistry(const WindowsRegistry& registry,
-                                               ULONG buffer_size);
+    const WindowsProcTable& windows_proc_table);
 
 // Retrieve the preferred languages from the MUI API.
-std::wstring GetPreferredLanguagesFromMUI();
+std::wstring GetPreferredLanguagesFromMUI(
+    const WindowsProcTable& windows_proc_table);
 
 // Returns the list of user-preferred languages, in preference order.
 // The language names are as described at:
 // https://docs.microsoft.com/en-us/windows/win32/intl/language-names
 std::vector<std::wstring> GetPreferredLanguages(
-    const WindowsRegistry& registry);
+    const WindowsProcTable& windows_proc_table);
 
 // Parses a Windows language name into its components.
 LanguageInfo ParseLanguageName(std::wstring language_name);

shell/platform/windows/system_utils_unittests.cc

@@ -7,71 +7,47 @@
 
 #include "flutter/fml/macros.h"
 #include "flutter/shell/platform/windows/system_utils.h"
+#include "flutter/shell/platform/windows/testing/mock_windows_proc_table.h"
 #include "gtest/gtest.h"
 
 namespace flutter {
 namespace testing {
 
-class MockWindowsRegistry : public WindowsRegistry {
- public:
-  MockWindowsRegistry() = default;
-  virtual ~MockWindowsRegistry() = default;
-
-  virtual LSTATUS GetRegistryValue(HKEY hkey,
-                                   LPCWSTR key,
-                                   LPCWSTR value,
-                                   DWORD flags,
-                                   LPDWORD type,
-                                   PVOID data,
-                                   LPDWORD data_size) const {
-    using namespace std::string_literals;
-    static const std::wstring locales =
-        L"en-US\0zh-Hans-CN\0ja\0zh-Hant-TW\0he\0\0"s;
-    static DWORD locales_len = locales.size() * sizeof(wchar_t);
-    if (data != nullptr) {
-      if (*data_size < locales_len) {
-        return ERROR_MORE_DATA;
-      }
-      std::memcpy(data, locales.data(), locales_len);
-      *data_size = locales_len;
-    } else if (data_size != NULL) {
-      *data_size = locales_len;
-    }
-    return ERROR_SUCCESS;
-  }
-
- private:
-  FML_DISALLOW_COPY_AND_ASSIGN(MockWindowsRegistry);
-};
-
 TEST(SystemUtils, GetPreferredLanguageInfo) {
-  WindowsRegistry registry;
-  std::vector<LanguageInfo> languages = GetPreferredLanguageInfo(registry);
+  WindowsProcTable proc_table;
+  std::vector<LanguageInfo> languages =
+      GetPreferredLanguageInfo(WindowsProcTable());
   // There should be at least one language.
   ASSERT_GE(languages.size(), 1);
   // The info should have a valid languge.
   EXPECT_GE(languages[0].language.size(), 2);
 }
 
 TEST(SystemUtils, GetPreferredLanguages) {
-  WindowsRegistry registry;
-  std::vector<std::wstring> languages = GetPreferredLanguages(registry);
+  MockWindowsProcTable proc_table;
+  ON_CALL(proc_table, GetThreadPreferredUILanguages)
+      .WillByDefault(
+          [](DWORD flags, PULONG count, PZZWSTR languages, PULONG size) {
+            // Languages string ends in a double-null.
+            static const wchar_t lang[] = L"en-US\0";
+            static const size_t lang_len = sizeof(lang) / sizeof(wchar_t);
+            static const int cnt = 1;
+            if (languages == nullptr) {
+              *size = lang_len;
+              *count = cnt;
+            } else if (*size >= lang_len) {
+              memcpy(languages, lang, lang_len * sizeof(wchar_t));
+            }
+            return TRUE;
+          });
+  std::vector<std::wstring> languages = GetPreferredLanguages(proc_table);
   // There should be at least one language.
   ASSERT_GE(languages.size(), 1);
   // The language should be non-empty.
   EXPECT_FALSE(languages[0].empty());
   // There should not be a trailing null from the parsing step.
   EXPECT_EQ(languages[0].size(), wcslen(languages[0].c_str()));
-
-  // Test mock results
-  MockWindowsRegistry mock_registry;
-  languages = GetPreferredLanguages(mock_registry);
-  ASSERT_EQ(languages.size(), 5);
-  ASSERT_EQ(languages[0], std::wstring(L"en-US"));
-  ASSERT_EQ(languages[1], std::wstring(L"zh-Hans-CN"));
-  ASSERT_EQ(languages[2], std::wstring(L"ja"));
-  ASSERT_EQ(languages[3], std::wstring(L"zh-Hant-TW"));
-  ASSERT_EQ(languages[4], std::wstring(L"he"));
+  EXPECT_EQ(languages[0], L"en-US");
 }
 
 TEST(SystemUtils, ParseLanguageNameGeneric) {

shell/platform/windows/testing/mock_windows_proc_table.h

@@ -21,6 +21,9 @@ class MockWindowsProcTable : public WindowsProcTable {
   MOCK_METHOD2(GetPointerType,
                BOOL(UINT32 pointer_id, POINTER_INPUT_TYPE* pointer_type));
 
+  MOCK_CONST_METHOD4(GetThreadPreferredUILanguages,
+                     LRESULT(DWORD, PULONG, PZZWSTR, PULONG));
+
  private:
   FML_DISALLOW_COPY_AND_ASSIGN(MockWindowsProcTable);
 };

shell/platform/windows/windows_proc_table.cc

@@ -25,4 +25,11 @@ BOOL WindowsProcTable::GetPointerType(UINT32 pointer_id,
   return get_pointer_type_.value()(pointer_id, pointer_type);
 }
 
+LRESULT WindowsProcTable::GetThreadPreferredUILanguages(DWORD flags,
+                                                        PULONG count,
+                                                        PZZWSTR languages,
+                                                        PULONG length) const {
+  return ::GetThreadPreferredUILanguages(flags, count, languages, length);
+}
+
 }  // namespace flutter

shell/platform/windows/windows_proc_table.h

@@ -13,7 +13,7 @@
 namespace flutter {
 
 // Lookup table for Windows APIs that aren't available on all versions of
-// Windows.
+// Windows, or for mocking Windows API calls.
 class WindowsProcTable {
  public:
   WindowsProcTable();
@@ -26,6 +26,15 @@ class WindowsProcTable {
   virtual BOOL GetPointerType(UINT32 pointer_id,
                               POINTER_INPUT_TYPE* pointer_type);
 
+  // Get the preferred languages for the thread, and optionally the process,
+  // and system, in that order, depending on the flags.
+  // See
+  // https://learn.microsoft.com/windows/win32/api/winnls/nf-winnls-getthreadpreferreduilanguages
+  virtual LRESULT GetThreadPreferredUILanguages(DWORD flags,
+                                                PULONG count,
+                                                PZZWSTR languages,
+                                                PULONG length) const;
+
  private:
   using GetPointerType_ = BOOL __stdcall(UINT32 pointerId,
                                          POINTER_INPUT_TYPE* pointerType);