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content / common / process_visibility_tracker.h [blame]
// 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/40168826): 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_