Pref service: expose all read-only PrefStores through Mojo

components/prefs/pref_value_store.h

 // Copyright (c) 2012 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 COMPONENTS_PREFS_PREF_VALUE_STORE_H_
 #define COMPONENTS_PREFS_PREF_VALUE_STORE_H_
 
 #include <map>
 #include <string>
 #include <vector>
@@ skipping 12 matching lines @@
 // (e.g., configuration policies, extensions, and user settings). It returns
 // the value of a Preference from the source with the highest priority, and
 // allows setting user-defined values for preferences that are not managed.
 //
 // Unless otherwise explicitly noted, all of the methods of this class must
 // be called on the UI thread.
 class COMPONENTS_PREFS_EXPORT PrefValueStore {
  public:
   typedef base::Callback<void(const std::string&)> PrefChangedCallback;
 
+  // PrefStores must be listed here in order from highest to lowest priority.
+  //   MANAGED contains all managed preference values that are provided by
+  //      mandatory policies (e.g. Windows Group Policy or cloud policy).
+  //   SUPERVISED_USER contains preferences that are valid for supervised users.
+  //   EXTENSION contains preference values set by extensions.
+  //   COMMAND_LINE contains preference values set by command-line switches.
+  //   USER contains all user-set preference values.
+  //   RECOMMENDED contains all preferences that are provided by recommended
+  //      policies.
+  //   DEFAULT contains all application default preference values.
+  enum PrefStoreType {

[Bernhard Bauer, 2017/03/09 09:25:22]

Historically we haven't exposed the exact pref store types on purpose, but I
guess exposing it for the purpose of the Mojo service is probably okay, because
that is tied very closely to prefs anyway.

[tibell, 2017/03/09 23:07:12]

Yeah. I also felt it was a bit unfortunate but I couldn't see a better way once
we have store connecting to a central manager. We need a way to know which store
connected.

+    // INVALID_STORE is not associated with an actual PrefStore but used as
+    // an invalid marker, e.g. as a return value.
+    INVALID_STORE = -1,
+    MANAGED_STORE = 0,
+    SUPERVISED_USER_STORE,
+    EXTENSION_STORE,
+    COMMAND_LINE_STORE,
+    USER_STORE,
+    RECOMMENDED_STORE,
+    DEFAULT_STORE,
+    PREF_STORE_TYPE_MAX = DEFAULT_STORE
+  };
+
   // In decreasing order of precedence:
   //   |managed_prefs| contains all preferences from mandatory policies.
   //   |supervised_user_prefs| contains all preferences from supervised user
   //        settings, i.e. settings configured for a supervised user by their
   //        custodian.
   //   |extension_prefs| contains preference values set by extensions.
   //   |command_line_prefs| contains preference values set by command-line
   //        switches.
   //   |user_prefs| contains all user-set preference values.
   //   |recommended_prefs| contains all preferences from recommended policies.
@@ skipping 68 matching lines @@
   bool PrefValueUserModifiable(const std::string& name) const;
 
   // Check whether a Preference value is modifiable by an extension, i.e.
   // whether there is no higher-priority source controlling it.
   bool PrefValueExtensionModifiable(const std::string& name) const;
 
   // Update the command line PrefStore with |command_line_prefs|.
   void UpdateCommandLinePrefStore(PrefStore* command_line_prefs);
 
  private:
-  // PrefStores must be listed here in order from highest to lowest priority.
-  //   MANAGED contains all managed preference values that are provided by
-  //      mandatory policies (e.g. Windows Group Policy or cloud policy).
-  //   SUPERVISED_USER contains preferences that are valid for supervised users.
-  //   EXTENSION contains preference values set by extensions.
-  //   COMMAND_LINE contains preference values set by command-line switches.
-  //   USER contains all user-set preference values.
-  //   RECOMMENDED contains all preferences that are provided by recommended
-  //      policies.
-  //   DEFAULT contains all application default preference values.
-  enum PrefStoreType {
-    // INVALID_STORE is not associated with an actual PrefStore but used as
-    // an invalid marker, e.g. as a return value.
-    INVALID_STORE = -1,
-    MANAGED_STORE = 0,
-    SUPERVISED_USER_STORE,
-    EXTENSION_STORE,
-    COMMAND_LINE_STORE,
-    USER_STORE,
-    RECOMMENDED_STORE,
-    DEFAULT_STORE,
-    PREF_STORE_TYPE_MAX = DEFAULT_STORE
-  };
-
   // Keeps a PrefStore reference on behalf of the PrefValueStore and monitors
   // the PrefStore for changes, forwarding notifications to PrefValueStore. This
   // indirection is here for the sake of disambiguating notifications from the
   // individual PrefStores.
   class PrefStoreKeeper : public PrefStore::Observer {
    public:
     PrefStoreKeeper();
     ~PrefStoreKeeper() override;
 
     // Takes ownership of |pref_store|.
@@ skipping 95 matching lines @@
 
   // A mapping of preference names to their registered types.
   PrefTypeMap pref_types_;
 
   // True if not all of the PrefStores were initialized successfully.
   bool initialization_failed_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefValueStore);
 };
 
+namespace std {
+
+template <>
+struct hash<PrefValueStore::PrefStoreType> {

[Bernhard Bauer, 2017/03/09 09:25:22]

It might almost be worth making a macro out of this to allow hashing of enum
classes in general...

[tibell, 2017/03/09 23:07:12]

Agreed. I'll see what other Chromies think.

+  size_t operator()(PrefValueStore::PrefStoreType type) const {
+    return std::hash<
+        base::underlying_type<PrefValueStore::PrefStoreType>::type>()(type);
+  }
+};
+
+}  // namespace std
+
 #endif  // COMPONENTS_PREFS_PREF_VALUE_STORE_H_