content/public/browser/notification_service.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file describes a central switchboard for notifications that might
   6 // happen in various parts of the application, and allows users to register
   7 // observers for various classes of events that they're interested in.
   8
   9 #ifndef CONTENT_PUBLIC_BROWSER_NOTIFICATION_SERVICE_H_
  10 #define CONTENT_PUBLIC_BROWSER_NOTIFICATION_SERVICE_H_
  11
  12 #include "content/common/content_export.h"
  13 #include "content/public/browser/notification_details.h"
  14 #include "content/public/browser/notification_source.h"
  15
  16 namespace content {
  17
  18 class CONTENT_EXPORT NotificationService {
  19  public:
  20   // Returns the NotificationService object for the current thread, or NULL if
  21   // none.
  22   static NotificationService* current();
  23
  24   static NotificationService* Create();
  25
  26   virtual ~NotificationService() {}
  27
  28   // Synchronously posts a notification to all interested observers.
  29   // Source is a reference to a NotificationSource object representing
  30   // the object originating the notification (can be
  31   // NotificationService::AllSources(), in which case
  32   // only observers interested in all sources will be notified).
  33   // Details is a reference to an object containing additional data about
  34   // the notification.  If no additional data is needed, NoDetails() is used.
  35   // There is no particular order in which the observers will be notified.
  36   virtual void Notify(int type,
  37                       const NotificationSource& source,
  38                       const NotificationDetails& details) = 0;
  39
  40   // Returns a NotificationSource that represents all notification sources
  41   // (for the purpose of registering an observer for events from all sources).
  42   static Source<void> AllSources() { return Source<void>(NULL); }
  43
  44   // Returns the same value as AllSources(). This function has semantic
  45   // differences to the programmer: We have checked that this AllSources()
  46   // usage is safe in the face of multiple profiles. Objects that were
  47   // singletons now will always have multiple instances, one per browser
  48   // context.
  49   //
  50   // Some usage is safe, where the Source is checked to see if it's a member of
  51   // a container before use. But, we want the number of AllSources() calls to
  52   // drop to almost nothing, because most usages are not multiprofile safe and
  53   // were done because it was easier to listen to everything.
  54   static Source<void> AllBrowserContextsAndSources() {
  55     return Source<void>(NULL);
  56   }
  57
  58   // Returns a NotificationDetails object that represents a lack of details
  59   // associated with a notification.  (This is effectively a null pointer.)
  60   static Details<void> NoDetails() { return Details<void>(NULL); }
  61 };
  62
  63 }  // namespace content
  64
  65 #endif  // CONTENT_PUBLIC_BROWSER_NOTIFICATION_SERVICE_H_