Add a scoped notifier for pref dictionaries / lists.

chrome/browser/pref_service.h

 // Copyright (c) 2006-2008 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.
 
 // This provides a way to access the application's current preferences.
 // This service has two preference stores, one for "persistent" preferences,
 // which get serialized for use in the next session, and one for "transient"
 // preferences, which are in effect for only the current session
 // (this usually encodes things like command-line switches).
 //
 // Calling the getter functions in this class basically looks at both the
 // persistent and transient stores, where any corresponding value in the
 // transient store overrides the one in the persistent store.
 
 #ifndef CHROME_BROWSER_PREF_SERVICE_H_
 #define CHROME_BROWSER_PREF_SERVICE_H_
 
 #include <set>
 
 #include "base/file_path.h"
 #include "base/hash_tables.h"
 #include "base/non_thread_safe.h"
 #include "base/observer_list.h"
 #include "base/scoped_ptr.h"
 #include "base/values.h"
 #include "chrome/browser/important_file_writer.h"
 
 class NotificationObserver;
 class Preference;
+class ScopedPrefUpdate;
 
 class PrefService : public NonThreadSafe,
                     public ImportantFileWriter::DataSerializer {
  public:
 
   // A helper class to store all the information associated with a preference.
   class Preference {
    public:
 
     // The type of the preference is determined by the type of |default_value|.
@@ skipping 111 matching lines @@
   // Value type will be TYPE_STRING.
   void SetInt64(const wchar_t* path, int64 value);
   int64 GetInt64(const wchar_t* path) const;
   void RegisterInt64Pref(const wchar_t* path, int64 default_value);
 
   // Used to set the value of dictionary or list values in the pref tree.  This
   // will create a dictionary or list if one does not exist in the pref tree.
   // This method returns NULL only if you're requesting an unregistered pref or
   // a non-dict/non-list pref.
   // WARNING: Changes to the dictionary or list will not automatically notify
-  // pref observers. TODO(tc): come up with a way to still fire observers.
+  // pref observers.
+  // Use a ScopedPrefUpdate to update observers on changes.
   DictionaryValue* GetMutableDictionary(const wchar_t* path);
   ListValue* GetMutableList(const wchar_t* path);
 
   // Returns true if a value has been set for the specified path.
   // NOTE: this is NOT the same as FindPreference. In particular
   // FindPreference returns whether RegisterXXX has been invoked, where as
   // this checks if a value exists for the path.
   bool HasPrefPath(const wchar_t* path) const;
 
   class PreferencePathComparator {
@@ skipping 37 matching lines @@
   // A set of all the registered Preference objects.
   PreferenceSet prefs_;
 
   // A map from pref names to a list of observers.  Observers get fired in the
   // order they are added.
   typedef ObserverList<NotificationObserver> NotificationObserverList;
   typedef base::hash_map<std::wstring, NotificationObserverList*>
       PrefObserverMap;
   PrefObserverMap pref_observers_;
 
+  friend class ScopedPrefUpdate;
+
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };
 
 #endif  // CHROME_BROWSER_PREF_SERVICE_H_