Mojom interface for Preferences

services/preferences/public/cpp/pref_observer_store.h

+// Copyright 2016 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 SERVICES_PREFERENCES_PUBLIC_CPP_PREFS_OBSERVER_STORE_H_
+#define SERVICES_PREFERENCES_PUBLIC_CPP_PREFS_OBSERVER_STORE_H_
+
+#include <set>
+
+#include "base/macros.h"
+#include "components/prefs/value_map_pref_store.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "services/preferences/public/cpp/preferences_export.h"
+#include "services/preferences/public/interfaces/preferences.mojom.h"
+
+namespace shell {
+class Connector;
+}
+
+class PrefObserverStoreTest;
+
+// An implementation of PrefStore which uses prefs::mojom::PreferenceManager as
+// the backing of the preferences.
+//
+// PrefObserverStore caches the values locally to provide synchronous access.
+// The cache is empty until the first notification of OnPreferencesChanged is
+// received from the prefs::mojom::PreferenceManager. Upon this completion any
+// PrefStore::Observer will be notified of OnInitializationCompleted.
+//
+// Currently this does not support RemoveValue or GetMutableValue.

[Elliot Glaysher, 2016/07/26 21:11:58]

In the case of GetMutableValue, there are few enough callers to GetMutableValue
(about 20) that converting those to not use GetMutableValue might be easier than
implementing it.

+class SERVICES_PREFERENCES_EXPORT PrefObserverStore
+    : public ValueMapPrefStore,
+      public prefs::mojom::PreferenceObserver {
+ public:
+  PrefObserverStore(prefs::mojom::PreferenceManagerPtr prefs_manager_ptr);
+
+  // Defines the set of |keys| which PrefOvserverStore will handle. Begins
+  // listening for changes to these from |prefs_manager_|.
+  void Init(const std::set<std::string>& keys);
+
+  // PrefStore:
+  bool GetValue(const std::string& key,
+                const base::Value** value) const override;
+
+  // ValueMapPrefStore:
+  void SetValue(const std::string& key,
+                std::unique_ptr<base::Value> value,
+                uint32_t flags) override;
+  void RemoveValue(const std::string& key, uint32_t flags) override;
+  bool GetMutableValue(const std::string& key, base::Value** value) override;
+  void ReportValueChanged(const std::string& key, uint32_t flags) override;
+  void SetValueSilently(const std::string& key,
+                        std::unique_ptr<base::Value> value,
+                        uint32_t flags) override;
+
+ protected:
+  // base::RefCounted<PrefStore>:
+  ~PrefObserverStore() override;
+
+ private:
+  friend class PrefObserverStoreTest;
+
+  // Notifies |prefs_manager_| of the change in |key| - |value| pair.
+  void SetValueOnPreferenceManager(const std::string& key, base::Value* value);
+
+  // prefs::mojom::PreferenceObserver:
+  void OnPreferencesChanged(
+      std::unordered_map<std::string, prefs::mojom::PreferencePtr> preferences)
+      override;
+
+  mojo::Binding<prefs::mojom::PreferenceObserver> prefs_binding_;
+  prefs::mojom::PreferenceManagerPtr prefs_manager_ptr_;
+  // Typically contained in |prefs_manager_ptr_| however tests may override.
+  prefs::mojom::PreferenceManager* prefs_manager_;
+
+  std::set<std::string> keys_;
+
+  // True upon the first OnPreferencesChanged received after Init.
+  bool initialized_;
+
+  DISALLOW_COPY_AND_ASSIGN(PrefObserverStore);
+};
+
+#endif  // SERVICES_PREFERENCES_PUBLIC_CPP_PREFS_OBSERVER_STORE_H_