| // Copyright 2021 The Chromium Authors |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #ifndef CONTENT_COMMON_PROCESS_VISIBILITY_TRACKER_H_ |
| #define CONTENT_COMMON_PROCESS_VISIBILITY_TRACKER_H_ |
| |
| #include <optional> |
| |
| #include "base/memory/scoped_refptr.h" |
| #include "base/no_destructor.h" |
| #include "base/observer_list_threadsafe.h" |
| #include "base/sequence_checker.h" |
| #include "base/synchronization/lock.h" |
| #include "base/thread_annotations.h" |
| #include "content/common/content_export.h" |
| |
| namespace content { |
| |
| // This class represents overall on-screen visibility for a given process of the |
| // embedding application. Currently only works/is used in the browser process on |
| // Android (Chrome and WebView). |
| // TODO(crbug.com/1177542): implement usage in other processes. |
| // Observers can be added from any sequence, but OnProcessVisibilityChanged() |
| // should be called from the thread that created the tracker instance. |
| class CONTENT_EXPORT ProcessVisibilityTracker { |
| public: |
| // Creates the tracker on the current thread. This should be the same thread |
| // that calls OnProcessVisibilityChanged(), usually the main thread. |
| static ProcessVisibilityTracker* GetInstance(); |
| |
| class ProcessVisibilityObserver : public base::CheckedObserver { |
| public: |
| virtual void OnVisibilityChanged(bool visible) = 0; |
| }; |
| |
| // Should be called when the embedder app becomes visible or invisible, from |
| // the thread that created the tracker. Notifies the registered observers of |
| // the change. |
| void OnProcessVisibilityChanged(bool visible); |
| |
| // Can be called from any thread. |
| void AddObserver(ProcessVisibilityObserver* observer); |
| void RemoveObserver(ProcessVisibilityObserver* observer); |
| |
| private: |
| friend class base::NoDestructor<ProcessVisibilityTracker>; |
| ProcessVisibilityTracker(); |
| ~ProcessVisibilityTracker(); |
| |
| base::Lock lock_; |
| std::optional<bool> is_visible_ GUARDED_BY(lock_); |
| scoped_refptr<base::ObserverListThreadSafe<ProcessVisibilityObserver>> |
| observers_ GUARDED_BY(lock_); |
| |
| SEQUENCE_CHECKER(main_thread_); |
| }; |
| |
| } // namespace content |
| |
| #endif // CONTENT_COMMON_PROCESS_VISIBILITY_TRACKER_H_ |