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// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
#define UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
#include "base/memory/raw_ptr.h"
#include "base/observer_list.h"
#include "base/observer_list_types.h"
#include "ui/message_center/message_center_export.h"
#include "ui/message_center/public/cpp/notification.h"
namespace message_center {
class MessageCenter;
// NotificationBlocker manages the availability of notifications based on the
// current system status. Each NotificationBlocker implementation covers a
// single state such as screen lock or fullscreen.
//
// The current notification state is automatically updated when a blocker is
// initialized or destroyed. For instance, the `WelcomeTourNotificationBlocker`
// blocks all existing notifications when it is initialized (see below for how
// to properly initialize a `NotificationBlocker` subclass), and unblocks
// notifications when it is destructed.
//
// An object of a class that derives from this is not ready until `Init()` has
// been called. The following example demonstrates how to properly initialize
// such an object:
//
// class MyNotificationBlocker : public NotificationBlocker {
// public:
// MyNotificationBlocker(MessageCenter* message_center, ...)
// : NotificationBlocker(message_center), ... { ... }
// ...
// };
//
// void foo() {
// MessageCenter* message_center = ...;
// std::unique_ptr<MyNotificationBlocker> my_blocker =
// std::make_unique<MyNotificationBlocker>(message_center, ...);
// my_blocker->Init(); /* DON'T FORGET THIS LINE! */
// ...
// }
//
// TODO(b/290637034): Improve upon the `Init()` pattern as it is easy to forget
// to call `Init()` when initializing a `NotificationBlocker` subclass.
class MESSAGE_CENTER_EXPORT NotificationBlocker {
public:
class Observer : public base::CheckedObserver {
public:
virtual void OnBlockingStateChanged(NotificationBlocker* blocker) = 0;
};
explicit NotificationBlocker(MessageCenter* message_center);
virtual ~NotificationBlocker();
// Registers this `NotificationBlocker` with the `MessageCenter`. This cannot
// be done in the ctor because registering a notification blocker with the
// message center may indirectly call the virtual functions below (e.g.
// `ShouldShowNotification()` and `ShouldShowNotificationAsPopup()`), and
// virtual functions should not be called from a ctor.
void Init();
void AddObserver(Observer* observer);
void RemoveObserver(Observer* observer);
// Checks the current state and updates the availability.
virtual void CheckState() {}
// Returns true should be shown in the message center. Default returns true
// always.
virtual bool ShouldShowNotification(
const Notification& notification) const;
// Returns true if this notification should be shown as popups on screen.
// If it's false, those notifications should be queued.
// When a blocker starts returning false for a notification which is already
// shown as a popup, the notification should be closed as a popup immediately.
virtual bool ShouldShowNotificationAsPopup(
const Notification& notification) const = 0;
protected:
MessageCenter* message_center() { return message_center_; }
void NotifyBlockingStateChanged();
private:
bool is_initialized_ = false;
base::ObserverList<Observer> observers_;
raw_ptr<MessageCenter> message_center_; // weak
};
typedef std::vector<raw_ptr<NotificationBlocker, VectorExperimental>>
NotificationBlockers;
} // namespace message_center
#endif // UI_MESSAGE_CENTER_NOTIFICATION_BLOCKER_H_
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