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// 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.
// This file describes a central switchboard for notifications that might
// happen in various parts of the application, and allows users to register
// observers for various classes of events that they're interested in.
#include "content/common/content_export.h"
#include "content/public/browser/notification_details.h"
#include "content/public/browser/notification_source.h"
namespace content {
class CONTENT_EXPORT NotificationService {
// Returns the NotificationService object for the current thread, or nullptr
// if none.
static NotificationService* current();
static NotificationService* Create();
virtual ~NotificationService() {}
// Synchronously posts a notification to all interested observers.
// Source is a reference to a NotificationSource object representing
// the object originating the notification (can be
// NotificationService::AllSources(), in which case
// only observers interested in all sources will be notified).
// Details is a reference to an object containing additional data about
// the notification. If no additional data is needed, NoDetails() is used.
// There is no particular order in which the observers will be notified.
virtual void Notify(int type,
const NotificationSource& source,
const NotificationDetails& details) = 0;
// Returns a NotificationSource that represents all notification sources
// (for the purpose of registering an observer for events from all sources).
static Source<void> AllSources() { return Source<void>(nullptr); }
// Returns the same value as AllSources(). This function has semantic
// differences to the programmer: We have checked that this AllSources()
// usage is safe in the face of multiple profiles. Objects that were
// singletons now will always have multiple instances, one per browser
// context.
// Some usage is safe, where the Source is checked to see if it's a member of
// a container before use. But, we want the number of AllSources() calls to
// drop to almost nothing, because most usages are not multiprofile safe and
// were done because it was easier to listen to everything.
static Source<void> AllBrowserContextsAndSources() {
return Source<void>(nullptr);
// Returns a NotificationDetails object that represents a lack of details
// associated with a notification. (This is effectively a null pointer.)
static Details<void> NoDetails() { return Details<void>(nullptr); }
} // namespace content