Implement "Language Switcher" for Chromium OS.

chrome/browser/chromeos/language_library.h

+// Copyright (c) 2009 The Chromium 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 CHROME_BROWSER_CHROMEOS_LANGUAGE_LIBRARY_H_
+#define CHROME_BROWSER_CHROMEOS_LANGUAGE_LIBRARY_H_
+
+#include <string>
+
+#include "base/observer_list.h"
+#include "base/singleton.h"
+#include "base/time.h"
+#include "third_party/cros/chromeos_language.h"
+
+namespace chromeos {
+
+// This class handles the interaction with the ChromeOS language library APIs.
+// Classes can add themselves as observers. Users can get an instance of this
+// library class like this: LanguageLibrary::Get()
+class LanguageLibrary {
+ public:
+  class Observer {
+   public:
+    virtual ~Observer() = 0;
+    virtual void LanguageChanged(LanguageLibrary* obj) = 0;
+  };
+
+  // This gets the singleton LanguageLibrary
+  static LanguageLibrary* Get();
+
+  // Makes sure the library is loaded, loading it if necessary. Returns true if
+  // the library has been successfully loaded.
+  static bool EnsureLoaded();
+
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // Returns the list of IMEs and keyboard layouts we can select. If the cros
+  // library is not found or IBus/DBus daemon is not alive, this function
+  // returns a fallback language list (and never returns NULL).
+  InputLanguageList* GetLanguages();
+
+  // Changes the current IME engine to |id| and enable IME (when |category|
+  // is LANGUAGE_CATEGORY_IME). Changes the current XKB layout to |id| and
+  // disable IME (when |category| is LANGUAGE_CATEGORY_XKB). |id| is a unique
+  // identifier of a IME engine or XKB layout. Please check chromeos_language.h
+  // in src third_party/cros/ for details.
+  void ChangeLanguage(LanguageCategory category, const std::string& id);
+
+  const InputLanguage& current_language() const {
+    return current_language_;
+  }
+
+ private:
+  friend struct DefaultSingletonTraits<LanguageLibrary>;
+
+  LanguageLibrary();
+  ~LanguageLibrary();
+
+  // This method is called when there's a change in language status.
+  // This method is called on a background thread.
+  static void LanguageChangedHandler(
+      void* object, const InputLanguage& current_language);
+
+  // This methods starts the monitoring of language changes.
+  void Init();
+
+  // Called by the handler to update the language status.
+  // This will notify all the Observers.
+  void UpdateCurrentLanguage(const InputLanguage& current_language);
+
+  // A reference to the language api, to allow callbacks when the language
+  // status changes.
+  LanguageStatusConnection* language_status_connection_;
+  ObserverList<Observer> observers_;
+
+  // The language (IME or XKB layout) which currently selected.
+  InputLanguage current_language_;
+
+  DISALLOW_COPY_AND_ASSIGN(LanguageLibrary);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_LANGUAGE_LIBRARY_H_
+