Refactor preference syncing.

chrome/browser/prefs/pref_service.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_PREFS_PREF_SERVICE_H_
 #define CHROME_BROWSER_PREFS_PREF_SERVICE_H_
 #pragma once
 
 #include <set>
 #include <string>
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "base/values.h"
 #include "chrome/common/json_pref_store.h"
 
 class DefaultPrefStore;
 class FilePath;
 class NotificationObserver;
 class PersistentPrefStore;
-class PrefChangeObserver;
+class PrefModelAssociator;
 class PrefNotifier;
 class PrefNotifierImpl;
 class PrefStore;
 class PrefValueStore;
 class Profile;
+class SyncableService;
 
 namespace subtle {
 class PrefMemberBase;
 class ScopedUserPrefUpdateBase;
 };
 
 class PrefService;
 
 class PrefServiceDelegate {
  public:
@@ skipping 124 matching lines @@
   // we need to save immediately (basically, during shutdown).  Otherwise, you
   // should use ScheduleSavePersistentPrefs.
   bool SavePersistentPrefs();
 
   // Serializes the data and schedules save using ImportantFileWriter.
   void ScheduleSavePersistentPrefs();
 
   // Lands pending writes to disk.
   void CommitPendingWrite();
 
-  // Make the PrefService aware of a pref.
-  void RegisterBooleanPref(const char* path, bool default_value);
-  void RegisterIntegerPref(const char* path, int default_value);
-  void RegisterDoublePref(const char* path, double default_value);
-  void RegisterStringPref(const char* path, const std::string& default_value);
-  void RegisterFilePathPref(const char* path, const FilePath& default_value);
-  void RegisterListPref(const char* path);
-  void RegisterDictionaryPref(const char* path);
+  // Make the PrefService aware of a pref, and inform the Sync model associator
+  // if we want to synchronize it.
+  void RegisterBooleanPref(const char* path,
+                           bool default_value,
+                           bool syncable);
+  void RegisterIntegerPref(const char* path,
+                           int default_value,
+                           bool syncable);
+  void RegisterDoublePref(const char* path,
+                          double default_value,
+                          bool syncable);
+  void RegisterStringPref(const char* path,
+                          const std::string& default_value,
+                          bool syncable);
+  void RegisterFilePathPref(const char* path,
+                            const FilePath& default_value,
+                            bool syncable);
+  void RegisterListPref(const char* path, bool syncable);
+  void RegisterDictionaryPref(const char* path, bool syncable);
   // These take ownership of the default_value:
-  void RegisterListPref(const char* path, ListValue* default_value);
-  void RegisterDictionaryPref(const char* path, DictionaryValue* default_value);
+  void RegisterListPref(const char* path,
+                        ListValue* default_value,
+                        bool syncable);
+  void RegisterDictionaryPref(const char* path,
+                              DictionaryValue* default_value,
+                              bool syncable);
 
   // These variants use a default value from the locale dll instead.
   void RegisterLocalizedBooleanPref(const char* path,
-                                    int locale_default_message_id);
+                                    int locale_default_message_id,
+                                    bool syncable);
   void RegisterLocalizedIntegerPref(const char* path,
-                                    int locale_default_message_id);
+                                    int locale_default_message_id,
+                                    bool syncable);
   void RegisterLocalizedDoublePref(const char* path,
-                                   int locale_default_message_id);
+                                   int locale_default_message_id,
+                                   bool syncable);
   void RegisterLocalizedStringPref(const char* path,
-                                   int locale_default_message_id);
+                                   int locale_default_message_id,
+                                   bool syncable);
 
   // If the path is valid and the value at the end of the path matches the type
   // specified, it will return the specified value.  Otherwise, the default
   // value (set when the pref was registered) will be returned.
   bool GetBoolean(const char* path) const;
   int GetInteger(const char* path) const;
   double GetDouble(const char* path) const;
   std::string GetString(const char* path) const;
   FilePath GetFilePath(const char* path) const;
 
@@ skipping 16 matching lines @@
   void SetInteger(const char* path, int value);
   void SetDouble(const char* path, double value);
   void SetString(const char* path, const std::string& value);
   void SetFilePath(const char* path, const FilePath& value);
 
   // Int64 helper methods that actually store the given value as a string.
   // Note that if obtaining the named value via GetDictionary or GetList, the
   // Value type will be TYPE_STRING.
   void SetInt64(const char* path, int64 value);
   int64 GetInt64(const char* path) const;
-  void RegisterInt64Pref(const char* path, int64 default_value);
+  void RegisterInt64Pref(const char* path, int64 default_value, bool syncable);
 
   // 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 char* path) const;
 
   // Returns a dictionary with effective preference values. The ownership
   // is passed to the caller.
   DictionaryValue* GetPreferenceValues() const;
 
   // A helper method to quickly look up a preference.  Returns NULL if the
   // preference is not registered.
   const Preference* FindPreference(const char* pref_name) const;
 
   bool ReadOnly() const;
 
+  // SyncableService getter.
+  // TODO(zea): Have PrefService implement SyncableService directly.
+  SyncableService* GetSyncableService();
+
  protected:
   // Construct a new pref service, specifying the pref sources as explicit
   // PrefStore pointers. This constructor is what CreatePrefService() ends up
   // calling. It's also used for unit tests.
   PrefService(PrefStore* managed_platform_prefs,
               PrefStore* managed_cloud_prefs,
               PrefStore* extension_prefs,
               PrefStore* command_line_prefs,
               PersistentPrefStore* user_prefs,
               PrefStore* recommended_platform_prefs,
@@ skipping 42 matching lines @@
   // method with PREF_CHANGED. Note that observers should not call these methods
   // directly but rather use a PrefChangeRegistrar to make sure the observer
   // gets cleaned up properly.
   virtual void AddPrefObserver(const char* path, NotificationObserver* obs);
   virtual void RemovePrefObserver(const char* path, NotificationObserver* obs);
 
   // Registers a new preference at |path|. The |default_value| must not be
   // NULL as it determines the preference value's type.
   // RegisterPreference must not be called twice for the same path.
   // This method takes ownership of |default_value|.
-  void RegisterPreference(const char* path, Value* default_value);
+  void RegisterPreference(const char* path,
+                          Value* default_value,
+                          bool syncable);
 
   // Sets the value for this pref path in the user pref store and informs the
   // PrefNotifier of the change.
   void SetUserPrefValue(const char* path, Value* new_value);
 
   // Load preferences from storage, attempting to diagnose and handle errors.
   // This should only be called from the constructor.
   void InitFromStorage();
 
   // Used to set the value of dictionary or list values in the user pref store.
@@ skipping 15 matching lines @@
 
   // Local cache of registered Preference objects. The default_store_
   // is authoritative with respect to what the types and default values
   // of registered preferences are.
   mutable PreferenceSet prefs_;
 
   // Holds delegator to be called after initialization, if async version
   // is used.
   PrefServiceDelegate* delegate_;
 
+  // The model associator that maintains the links with the sync db.
+  scoped_ptr<PrefModelAssociator> pref_sync_associator_;

[Mattias Nissler (ping if slow), 2011/05/06 04:00:02]

What's the advantage of adding the PrefModelAssociator into the internals of the
already non-trivial pref system? It seems like PrefModelAssociator needs two
things:
(a) check whether a pref is to be synced
(b) respond to pref notifications
We could achieve (a) by adding a state bit that can be queried through the
PrefService::Preference and (b) is already observable through the public
interface, so there'd be no need to host the associator within the PrefService.

[tim (not reviewing), 2011/05/06 04:27:54]

Part of this is we're getting rid of our "glue" layer in sync and organizing
per-data type glue code alongside the main services as part of the "think sync"
effort.

Perhaps we should discuss over VC / in person? Nicolas / myself would be happy
to discuss how we anticipate this making life easier for maintainers of prefs.

We were assuming that prefs ownership was as decentralized as use of
RegisterPref :)  It's a relief to know there's someone we can talk to.

+
   DISALLOW_COPY_AND_ASSIGN(PrefService);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_SERVICE_H_