1// Copyright (c) 2013 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// Given a starting render_process_id and main_render_frame_id, the
6// WebContentsTracker tracks changes to the active RenderFrameHost tree during
7// the lifetime of a WebContents instance.  This is used when mirroring tab
8// video and audio so that user navigations, crashes, iframes, etc., during a
9// tab's lifetime allow the capturing code to remain active on the
10// current/latest render frame tree.
11//
12// Threading issues: Start(), Stop() and the ChangeCallback are invoked on the
13// same thread.  This can be any thread, and the decision is locked-in by
14// WebContentsTracker when Start() is called.
15
16#ifndef CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_TRACKER_H_
17#define CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_TRACKER_H_
18
19#include "base/callback.h"
20#include "base/memory/ref_counted.h"
21#include "content/common/content_export.h"
22#include "content/public/browser/web_contents_observer.h"
23
24namespace base {
25class MessageLoopProxy;
26}
27
28namespace content {
29
30class RenderWidgetHost;
31
32class CONTENT_EXPORT WebContentsTracker
33    : public base::RefCountedThreadSafe<WebContentsTracker>,
34      public WebContentsObserver {
35 public:
36  // If |track_fullscreen_rwh| is true, the ChangeCallback will be run when a
37  // WebContents shows/destroys a fullscreen RenderWidgetHost view.  If false,
38  // fullscreen events are ignored.  Specify true for video tab capture and
39  // false for audio tab capture.
40  explicit WebContentsTracker(bool track_fullscreen_rwh);
41
42  // Callback to indicate a new RenderWidgetHost should be targeted for capture.
43  // This is also invoked with NULL to indicate tracking will not continue
44  // (i.e., the WebContents instance was not found or has been destroyed).
45  typedef base::Callback<void(RenderWidgetHost* rwh)> ChangeCallback;
46
47  // Start tracking.  The last-known |render_process_id| and
48  // |main_render_frame_id| are provided, and |callback| will be run once to
49  // indicate the current capture target (this may occur during the invocation
50  // of Start(), or in the future).  The callback will be invoked on the same
51  // thread calling Start().
52  virtual void Start(int render_process_id, int main_render_frame_id,
53                     const ChangeCallback& callback);
54
55  // Stop tracking.  Once this method returns, the callback is guaranteed not to
56  // be invoked again.
57  virtual void Stop();
58
59  // Current target.  This must only be called on the UI BrowserThread.
60  RenderWidgetHost* GetTargetRenderWidgetHost() const;
61
62 protected:
63  friend class base::RefCountedThreadSafe<WebContentsTracker>;
64  virtual ~WebContentsTracker();
65
66 private:
67  // Determine the target RenderWidgetHost and, if different from that last
68  // reported, runs the ChangeCallback on the appropriate thread.  If
69  // |force_callback_run| is true, the ChangeCallback is run even if the
70  // RenderWidgetHost has not changed.
71  void OnPossibleTargetChange(bool force_callback_run);
72
73  // Called on the thread that Start()/Stop() are called on.  Checks whether the
74  // callback is still valid and, if so, runs it.
75  void MaybeDoCallback(RenderWidgetHost* rwh);
76
77  // Look-up the current WebContents instance associated with the given
78  // |render_process_id| and |main_render_frame_id| and begin observing it.
79  void StartObservingWebContents(int render_process_id,
80                                 int main_render_frame_id);
81
82  // WebContentsObserver overrides: According to web_contents_observer.h, these
83  // two method overrides are all that is necessary to track the set of active
84  // RenderFrameHosts.
85  virtual void RenderFrameDeleted(RenderFrameHost* render_frame_host) OVERRIDE;
86  virtual void RenderFrameHostChanged(RenderFrameHost* old_host,
87                                      RenderFrameHost* new_host) OVERRIDE;
88
89  // WebContentsObserver override to notify the client that the capture target
90  // has been permanently lost.
91  virtual void WebContentsDestroyed() OVERRIDE;
92
93  // WebContentsObserver overrides to notify the client that the capture target
94  // may have changed due to a separate fullscreen widget shown/destroyed.
95  virtual void DidShowFullscreenWidget(int routing_id) OVERRIDE;
96  virtual void DidDestroyFullscreenWidget(int routing_id) OVERRIDE;
97
98  // If true, the client is interested in the showing/destruction of fullscreen
99  // RenderWidgetHosts.
100  const bool track_fullscreen_rwh_;
101
102  // MessageLoop corresponding to the thread that called Start().
103  scoped_refptr<base::MessageLoopProxy> message_loop_;
104
105  // Callback to run when the target RenderWidgetHost has changed.
106  ChangeCallback callback_;
107
108  // Pointer to the RenderWidgetHost provided in the last run of |callback_|.
109  // This is used to eliminate duplicate callback runs.
110  RenderWidgetHost* last_target_;
111
112  DISALLOW_COPY_AND_ASSIGN(WebContentsTracker);
113};
114
115}  // namespace content
116
117#endif  // CONTENT_BROWSER_MEDIA_CAPTURE_WEB_CONTENTS_TRACKER_H_
118