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      1 // Copyright 2013 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 #ifndef UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
      6 #define UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
      7 
      8 #include "base/observer_list.h"
      9 #include "ui/message_center/message_center_export.h"
     10 #include "ui/message_center/notification.h"
     11 
     12 namespace message_center {
     13 class MessageCenter;
     14 
     15 // NotificationBlocker manages the availability of notifications based on the
     16 // current system status. Each NotificationBlocker implementation covers a
     17 // single state such as screen lock or fullscreen.
     18 class MESSAGE_CENTER_EXPORT NotificationBlocker {
     19  public:
     20   class Observer {
     21    public:
     22     virtual void OnBlockingStateChanged(NotificationBlocker* blocker) = 0;
     23   };
     24 
     25   explicit NotificationBlocker(MessageCenter* message_center);
     26   virtual ~NotificationBlocker();
     27 
     28   void AddObserver(Observer* observer);
     29   void RemoveObserver(Observer* observer);
     30 
     31   // Checks the current state and updates the availability.
     32   virtual void CheckState() {}
     33 
     34   // Returns true when notifications from |notifier_id| should appear in the
     35   // message center. Default returns true always.
     36   virtual bool ShouldShowNotification(const NotifierId& notifier_id) const;
     37 
     38   // Returns true when notifications from |notifier_id| should be shown as
     39   // popups on screen.  If it's false, those notifications should be queued.
     40   // When a blocker starts returning false for a notification which is already
     41   // shown as a popup, the notification should be closed as a popup immediately.
     42   virtual bool ShouldShowNotificationAsPopup(
     43       const NotifierId& notifier_id) const = 0;
     44 
     45  protected:
     46   MessageCenter* message_center() { return message_center_; }
     47   void NotifyBlockingStateChanged();
     48 
     49  private:
     50   ObserverList<Observer> observers_;
     51   MessageCenter* message_center_;  // weak
     52 };
     53 
     54 typedef std::vector<NotificationBlocker*> NotificationBlockers;
     55 
     56 }  // namespace message_center
     57 
     58 #endif  // UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
     59