[embedder][glfw] Add support for locales to glfw shell (flutter#22657)

The other linux shell (and all the other embedding) have support for
getting the locales from the system and sending them over the
flutter/localization channel. The glfw shell does not have that which is
causing a crash on an assert now that Locale is no longer nullable
in Platform.

This adds a similar approach to what is going on over in the other linux
shell.

Author: rokob

BUILD.gn

@@ -4,6 +4,7 @@
 
 import("//flutter/common/config.gni")
 import("//flutter/shell/platform/config.gni")
+import("//flutter/shell/platform/glfw/config.gni")
 import("//flutter/testing/testing.gni")
 
 # Whether to build the dartdevc sdk, libraries, and source files
@@ -140,6 +141,10 @@ group("flutter") {
       if (is_linux) {
         public_deps +=
             [ "//flutter/shell/platform/linux:flutter_linux_unittests" ]
+        if (build_glfw_shell) {
+          public_deps +=
+              [ "//flutter/shell/platform/glfw:flutter_glfw_unittests" ]
+        }
       }
 
       if (is_mac) {

ci/licenses_golden/licenses_flutter

@@ -1298,6 +1298,9 @@ FILE: ../../../flutter/shell/platform/glfw/keyboard_hook_handler.h
 FILE: ../../../flutter/shell/platform/glfw/platform_handler.cc
 FILE: ../../../flutter/shell/platform/glfw/platform_handler.h
 FILE: ../../../flutter/shell/platform/glfw/public/flutter_glfw.h
+FILE: ../../../flutter/shell/platform/glfw/system_utils.cc
+FILE: ../../../flutter/shell/platform/glfw/system_utils.h
+FILE: ../../../flutter/shell/platform/glfw/system_utils_test.cc
 FILE: ../../../flutter/shell/platform/glfw/text_input_plugin.cc
 FILE: ../../../flutter/shell/platform/glfw/text_input_plugin.h
 FILE: ../../../flutter/shell/platform/linux/egl_utils.cc

shell/platform/glfw/BUILD.gn

@@ -2,6 +2,8 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//flutter/testing/testing.gni")
+
 _public_headers = [ "public/flutter_glfw.h" ]
 
 # Any files that are built by clients (client_wrapper code, library headers for
@@ -28,6 +30,8 @@ source_set("flutter_glfw_headers") {
 }
 
 source_set("flutter_glfw") {
+  public = [ "system_utils.h" ]
+
   sources = [
     "event_loop.cc",
     "event_loop.h",
@@ -41,6 +45,7 @@ source_set("flutter_glfw") {
     "keyboard_hook_handler.h",
     "platform_handler.cc",
     "platform_handler.h",
+    "system_utils.cc",
     "text_input_plugin.cc",
     "text_input_plugin.h",
   ]
@@ -71,6 +76,21 @@ source_set("flutter_glfw") {
   }
 }
 
+test_fixtures("flutter_glfw_fixtures") {
+  fixtures = []
+}
+
+executable("flutter_glfw_unittests") {
+  testonly = true
+  sources = [ "system_utils_test.cc" ]
+  deps = [
+    ":flutter_glfw",
+    ":flutter_glfw_fixtures",
+    "//flutter/shell/platform/embedder:embedder_headers",
+    "//flutter/testing",
+  ]
+}
+
 copy("publish_headers_glfw") {
   sources = _public_headers
   outputs = [ "$root_out_dir/{{source_file_part}}" ]

shell/platform/glfw/flutter_glfw.cc

@@ -22,6 +22,7 @@
 #include "flutter/shell/platform/glfw/key_event_handler.h"
 #include "flutter/shell/platform/glfw/keyboard_hook_handler.h"
 #include "flutter/shell/platform/glfw/platform_handler.h"
+#include "flutter/shell/platform/glfw/system_utils.h"
 #include "flutter/shell/platform/glfw/text_input_plugin.h"
 
 // GLFW_TRUE & GLFW_FALSE are introduced since libglfw-3.3,
@@ -690,6 +691,27 @@ static bool RunFlutterEngine(
   return true;
 }
 
+// Passes locale information to the Flutter engine.
+static void SetUpLocales(FlutterDesktopEngineState* state) {
+  std::vector<flutter::LanguageInfo> languages =
+      flutter::GetPreferredLanguageInfo();
+  std::vector<FlutterLocale> flutter_locales =
+      flutter::ConvertToFlutterLocale(languages);
+  // Convert the locale list to the locale pointer list that must be provided.
+  std::vector<const FlutterLocale*> flutter_locale_list;
+  flutter_locale_list.reserve(flutter_locales.size());
+  std::transform(
+      flutter_locales.begin(), flutter_locales.end(),
+      std::back_inserter(flutter_locale_list),
+      [](const auto& arg) -> const auto* { return &arg; });
+  FlutterEngineResult result = FlutterEngineUpdateLocales(
+      state->flutter_engine, flutter_locale_list.data(),
+      flutter_locale_list.size());
+  if (result != kSuccess) {
+    std::cerr << "Failed to set up Flutter locales." << std::endl;
+  }
+}
+
 // Populates |state|'s helper object fields that are common to normal and
 // headless mode.
 //
@@ -713,6 +735,8 @@ static void SetUpCommonEngineState(FlutterDesktopEngineState* state,
   // System channel handler.
   state->platform_handler = std::make_unique<flutter::PlatformHandler>(
       state->internal_plugin_registrar->messenger(), window);
+
+  SetUpLocales(state);
 }
 
 bool FlutterDesktopInit() {

shell/platform/glfw/system_utils.cc

@@ -0,0 +1,154 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "flutter/shell/platform/glfw/system_utils.h"
+
+#include <cstdlib>
+#include <sstream>
+
+namespace flutter {
+
+namespace {
+
+const char* GetLocaleStringFromEnvironment() {
+  const char* retval;
+  retval = getenv("LANGUAGE");
+  if ((retval != NULL) && (retval[0] != '\0')) {
+    return retval;
+  }
+  retval = getenv("LC_ALL");
+  if ((retval != NULL) && (retval[0] != '\0')) {
+    return retval;
+  }
+  retval = getenv("LC_MESSAGES");
+  if ((retval != NULL) && (retval[0] != '\0')) {
+    return retval;
+  }
+  retval = getenv("LANG");
+  if ((retval != NULL) && (retval[0] != '\0')) {
+    return retval;
+  }
+
+  return NULL;
+}
+
+// The least specific to most specific components of a locale.
+enum Component {
+  kCodeset = 1 << 0,
+  kTerritory = 1 << 1,
+  kModifier = 1 << 2,
+};
+
+// Construct a mask indicating which of the components in |info| are set.
+int ComputeVariantMask(const LanguageInfo& info) {
+  int mask = 0;
+  if (!info.territory.empty()) {
+    mask |= kTerritory;
+  }
+  if (!info.codeset.empty()) {
+    mask |= kCodeset;
+  }
+  if (!info.modifier.empty()) {
+    mask |= kModifier;
+  }
+  return mask;
+}
+
+// Appends most specific to least specific variants of |info| to |languages|.
+// For example, "de_DE@euro" would append "de_DE@euro", "de@euro", "de_DE",
+// and "de".
+void AppendLocaleVariants(std::vector<LanguageInfo>& languages,
+                          LanguageInfo info) {
+  int mask = ComputeVariantMask(info);
+  for (int i = mask; i >= 0; --i) {
+    if ((i & ~mask) == 0) {
+      LanguageInfo variant;
+      variant.language = info.language;
+
+      if (i & kTerritory) {
+        variant.territory = info.territory;
+      }
+      if (i & kCodeset) {
+        variant.codeset = info.codeset;
+      }
+      if (i & kModifier) {
+        variant.modifier = info.modifier;
+      }
+      languages.push_back(variant);
+    }
+  }
+}
+
+// Parses a locale into its components.
+LanguageInfo ParseLocale(const std::string& locale) {
+  // Locales are of the form "language[_territory][.codeset][@modifier]"
+  LanguageInfo result;
+  std::string::size_type end = locale.size();
+  std::string::size_type modifier_pos = locale.rfind('@');
+  if (modifier_pos != std::string::npos) {
+    result.modifier = locale.substr(modifier_pos + 1, end - modifier_pos - 1);
+    end = modifier_pos;
+  }
+
+  std::string::size_type codeset_pos = locale.rfind('.', end);
+  if (codeset_pos != std::string::npos) {
+    result.codeset = locale.substr(codeset_pos + 1, end - codeset_pos - 1);
+    end = codeset_pos;
+  }
+
+  std::string::size_type territory_pos = locale.rfind('_', end);
+  if (territory_pos != std::string::npos) {
+    result.territory =
+        locale.substr(territory_pos + 1, end - territory_pos - 1);
+    end = territory_pos;
+  }
+
+  result.language = locale.substr(0, end);
+
+  return result;
+}
+
+}  // namespace
+
+std::vector<LanguageInfo> GetPreferredLanguageInfo() {
+  const char* locale_string;
+  locale_string = GetLocaleStringFromEnvironment();
+  if (!locale_string || locale_string[0] == '\0') {
+    // This is the default locale if none is specified according to ISO C.
+    locale_string = "C";
+  }
+  std::istringstream locales_stream(locale_string);
+  std::vector<LanguageInfo> languages;
+  std::string s;
+  while (getline(locales_stream, s, ':')) {
+    LanguageInfo info = ParseLocale(s);
+    AppendLocaleVariants(languages, info);
+  }
+  return languages;
+}
+
+std::vector<FlutterLocale> ConvertToFlutterLocale(
+    const std::vector<LanguageInfo>& languages) {
+  std::vector<FlutterLocale> flutter_locales;
+  flutter_locales.reserve(languages.size());
+  for (const auto& info : languages) {
+    FlutterLocale locale = {};
+    locale.struct_size = sizeof(FlutterLocale);
+    locale.language_code = info.language.c_str();
+    if (!info.territory.empty()) {
+      locale.country_code = info.territory.c_str();
+    }
+    if (!info.codeset.empty()) {
+      locale.script_code = info.codeset.c_str();
+    }
+    if (!info.modifier.empty()) {
+      locale.variant_code = info.modifier.c_str();
+    }
+    flutter_locales.push_back(locale);
+  }
+
+  return flutter_locales;
+}
+
+}  // namespace flutter

shell/platform/glfw/system_utils.h

@@ -0,0 +1,35 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef FLUTTER_SHELL_PLATFORM_GLFW_SYSTEM_UTILS_H_
+#define FLUTTER_SHELL_PLATFORM_GLFW_SYSTEM_UTILS_H_
+
+#include <string>
+#include <vector>
+
+#include "flutter/shell/platform/embedder/embedder.h"
+
+namespace flutter {
+
+// Components of a system language/locale.
+struct LanguageInfo {
+  std::string language;
+  std::string territory;
+  std::string codeset;
+  std::string modifier;
+};
+
+// Returns the list of user-preferred languages, in preference order,
+// parsed into LanguageInfo structures.
+std::vector<LanguageInfo> GetPreferredLanguageInfo();
+
+// Converts a  vector of LanguageInfo structs to a vector of FlutterLocale
+// structs. |languages| must outlive the returned value, since the returned
+// elements have pointers into it.
+std::vector<FlutterLocale> ConvertToFlutterLocale(
+    const std::vector<LanguageInfo>& languages);
+
+}  // namespace flutter
+
+#endif  // FLUTTER_SHELL_PLATFORM_GLFW_SYSTEM_UTILS_H_