ios/web/public/active_state_manager.h

   1 // Copyright 2015 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 IOS_WEB_PUBLIC_ACTIVE_STATE_MANAGER_H_
   6 #define IOS_WEB_PUBLIC_ACTIVE_STATE_MANAGER_H_
   7
   8 #include "base/macros.h"
   9
  10 namespace web {
  11
  12 class BrowserState;
  13
  14 // Manages the active state associated with a particular BrowserState. Not
  15 // thread safe. Must be used only on the main thread.
  16 class ActiveStateManager {
  17  public:
  18   // Sets the active state of the ActiveStateManager. At most one
  19   // ActiveStateManager can be active at any given time in the app. A
  20   // ActiveStateManager must be made inactive before it is destroyed. It is
  21   // valid to call |SetActive(true)| on an already active ActiveStateManager.
  22   virtual void SetActive(bool active) = 0;
  23   // Returns true if the BrowserState is active.
  24   virtual bool IsActive() = 0;
  25
  26   // Observer that is notified when a ActiveStateManager becomes active,
  27   // inactive or destroyed.
  28   class Observer {
  29    public:
  30     // Called when the ActiveStateManager becomes active.
  31     virtual void OnActive() {}
  32     // Called when the ActiveStateManager becomes inactive.
  33     virtual void OnInactive() {}
  34     // Called just before the ActiveStateManager is destroyed.
  35     virtual void WillBeDestroyed() {}
  36   };
  37   // Adds an observer for this class. An observer should not be added more
  38   // than once. The caller retains the ownership of the observer object.
  39   virtual void AddObserver(Observer* observer) = 0;
  40   // Removes an observer.
  41   virtual void RemoveObserver(Observer* observer) = 0;
  42
  43  protected:
  44   virtual ~ActiveStateManager(){};
  45 };
  46
  47 }  // namespace web
  48
  49 #endif  // IOS_WEB_PUBLIC_ACTIVE_STATE_MANAGER_H_