chromium/content/browser/media/audio_stream_monitor.h

// Copyright 2014 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_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_
#define CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_

#include "base/containers/flat_map.h"
#include "base/memory/raw_ptr.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "base/threading/thread_checker.h"
#include "base/time/time.h"
#include "base/timer/timer.h"
#include "build/build_config.h"
#include "content/common/content_export.h"
#include "content/public/browser/global_routing_id.h"
#include "content/public/browser/web_contents_observer.h"

namespace content {

class WebContents;

// Keeps track of the audible state of audio output streams and uses it to
// maintain a "was recently audible" binary state for the audio indicators in
// the tab UI.  The logic is to: 1) Turn on immediately when sound is audible;
// and 2) Hold on for X amount of time after sound has gone silent, then turn
// off if no longer audible.  Said another way, we don't want tab indicators to
// turn on/off repeatedly and annoy the user.  AudioStreamMonitor sends UI
// update notifications only when needed, but may be queried at any time.
//
// When monitoring is not available, audibility is approximated with having
// active audio streams.
//
// Each WebContentsImpl owns an AudioStreamMonitor.
class CONTENT_EXPORT AudioStreamMonitor : public WebContentsObserver { … };

}  // namespace content

#endif  // CONTENT_BROWSER_MEDIA_AUDIO_STREAM_MONITOR_H_