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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//
// A helper class that assists preferences in firing notifications when lists
// or dictionaries are changed.
#ifndef COMPONENTS_PREFS_SCOPED_USER_PREF_UPDATE_H_
#define COMPONENTS_PREFS_SCOPED_USER_PREF_UPDATE_H_
#include <string>
#include <string_view>
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ref.h"
#include "base/sequence_checker.h"
#include "base/values.h"
#include "components/prefs/pref_service.h"
#include "components/prefs/prefs_export.h"
class PrefService;
namespace subtle {
// Base class for ScopedUserPrefUpdateTemplate that contains the parts
// that do not depend on ScopedUserPrefUpdateTemplate's template parameter.
//
// We need this base class mostly for making it a friend of PrefService
// and getting access to PrefService::GetMutableUserPref and
// PrefService::ReportUserPrefChanged.
class COMPONENTS_PREFS_EXPORT ScopedUserPrefUpdateBase {
public:
ScopedUserPrefUpdateBase(const ScopedUserPrefUpdateBase&) = delete;
ScopedUserPrefUpdateBase& operator=(const ScopedUserPrefUpdateBase&) = delete;
protected:
ScopedUserPrefUpdateBase(PrefService* service, std::string_view path);
// Calls Notify().
virtual ~ScopedUserPrefUpdateBase();
// Sets `value_` to `service_`->GetMutableUserPref and returns it.
base::Value* GetValueOfType(base::Value::Type type);
private:
// If `value_` is not null, triggers a notification of PrefObservers and
// resets `value_`.
void Notify();
// Weak pointer.
const raw_ref<PrefService> service_;
// Path of the preference being updated.
const std::string path_;
// Cache of value from user pref store (set between Get() and Notify() calls).
raw_ptr<base::Value> value_ = nullptr;
SEQUENCE_CHECKER(sequence_checker_);
};
} // namespace subtle
// Class to support modifications to base::Value::Dicts while guaranteeing
// that PrefObservers are notified of changed values.
//
// This class may only be used on the UI thread as it requires access to the
// PrefService.
class COMPONENTS_PREFS_EXPORT ScopedDictPrefUpdate
: public subtle::ScopedUserPrefUpdateBase {
public:
// The underlying dictionary must not be removed from `service` during
// the lifetime of the created ScopedDictPrefUpdate.
ScopedDictPrefUpdate(PrefService* service, std::string_view path)
: ScopedUserPrefUpdateBase(service, path) {}
ScopedDictPrefUpdate(const ScopedDictPrefUpdate&) = delete;
ScopedDictPrefUpdate& operator=(const ScopedDictPrefUpdate&) = delete;
// Triggers an update notification if Get() was called.
~ScopedDictPrefUpdate() override = default;
// Returns a mutable `base::Value::Dict` instance that
// - is already in the user pref store, or
// - is (silently) created and written to the user pref store if none existed
// before.
//
// Calling Get() will result in an update notification automatically
// being triggered at destruction time.
//
// The ownership of the return value remains with the user pref store.
base::Value::Dict& Get();
base::Value::Dict& operator*() { return Get(); }
base::Value::Dict* operator->() { return &Get(); }
};
// Class to support modifications to base::Value::Lists while guaranteeing
// that PrefObservers are notified of changed values.
//
// This class may only be used on the UI thread as it requires access to the
// PrefService.
class COMPONENTS_PREFS_EXPORT ScopedListPrefUpdate
: public subtle::ScopedUserPrefUpdateBase {
public:
// The underlying list must not be removed from `service` during
// the lifetime of the created ScopedListPrefUpdate.
ScopedListPrefUpdate(PrefService* service, std::string_view path)
: ScopedUserPrefUpdateBase(service, path) {}
ScopedListPrefUpdate(const ScopedListPrefUpdate&) = delete;
ScopedListPrefUpdate& operator=(const ScopedListPrefUpdate&) = delete;
// Triggers an update notification if Get() was called.
~ScopedListPrefUpdate() override = default;
// Returns a mutable `base::Value::List` instance that
// - is already in the user pref store, or
// - is (silently) created and written to the user pref store if none existed
// before.
//
// Calling Get() will result in an update notification automatically
// being triggered at destruction time.
//
// The ownership of the return value remains with the user pref store.
base::Value::List& Get();
base::Value::List& operator*() { return Get(); }
base::Value::List* operator->() { return &Get(); }
};
#endif // COMPONENTS_PREFS_SCOPED_USER_PREF_UPDATE_H_
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