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