chromium/extensions/browser/extension_pref_value_map.h

// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_
#define EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_

#include <map>
#include <memory>
#include <set>
#include <string>

#include "base/observer_list.h"
#include "components/keyed_service/core/keyed_service.h"
#include "extensions/common/api/types.h"
#include "extensions/common/extension_id.h"

class PrefValueMap;

namespace base {
class Time;
class Value;
}

// Non-persistent data container that is shared by ExtensionPrefStores. All
// extension pref values (incognito and regular) are stored herein and
// provided to ExtensionPrefStores.
//
// The semantics of the ExtensionPrefValueMap are:
// - A regular setting applies to regular browsing sessions as well as incognito
//   browsing sessions.
// - An incognito setting applies only to incognito browsing sessions, not to
//   regular ones. It takes precedence over a regular setting set by the same
//   extension.
// - A regular-only setting applies only to regular browsing sessions, not to
//   incognito ones. It takes precedence over a regular setting set by the same
//   extension.
// - If two different extensions set a value for the same preference (and both
//   values apply to the regular/incognito browsing session), the extension that
//   was installed later takes precedence, regardless of whether the settings
//   are regular, incognito or regular-only.
//
// The following table illustrates the behavior:
//   A.reg | A.reg_only | A.inc | B.reg | B.reg_only | B.inc | E.reg | E.inc
//     1   |      -     |   -   |   -   |      -     |   -   |   1   |   1
//     1   |      2     |   -   |   -   |      -     |   -   |   2   |   1
//     1   |      -     |   3   |   -   |      -     |   -   |   1   |   3
//     1   |      2     |   3   |   -   |      -     |   -   |   2   |   3
//     1   |      -     |   -   |   4   |      -     |   -   |   4   |   4
//     1   |      2     |   3   |   4   |      -     |   -   |   4   |   4
//     1   |      -     |   -   |   -   |      5     |   -   |   5   |   1
//     1   |      -     |   3   |   4   |      5     |   -   |   5   |   4
//     1   |      -     |   -   |   -   |      -     |   6   |   1   |   6
//     1   |      2     |   -   |   4   |      -     |   6   |   4   |   6
//     1   |      2     |   3   |   -   |      5     |   6   |   5   |   6
//
// A = extension A, B = extension B, E = effective value
// .reg = regular value
// .reg_only = regular-only value
// .inc = incognito value
// Extension B has higher precedence than A.
class ExtensionPrefValueMap : public KeyedService { … };

#endif  // EXTENSIONS_BROWSER_EXTENSION_PREF_VALUE_MAP_H_