content/browser/renderer_host/media/web_contents_tracker.h

   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 render_view_id, the WebContentsTracker
   6 // tracks RenderViewHost instance swapping during the lifetime of a WebContents
   7 // instance.  This is used when mirroring tab video and audio so that user
   8 // navigations, crashes, etc., during a tab's lifetime allow the capturing code
   9 // to remain active on the current/latest RenderView.
  10 //
  11 // Threading issues: Start(), Stop() and the ChangeCallback are invoked on the
  12 // same thread.  This can be any thread, and the decision is locked-in by
  13 // WebContentsTracker when Start() is called.
  14
  15 #ifndef CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_
  16 #define CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_
  17
  18 #include "base/callback.h"
  19 #include "base/memory/ref_counted.h"
  20 #include "content/common/content_export.h"
  21 #include "content/public/browser/web_contents_observer.h"
  22
  23 namespace base {
  24 class MessageLoopProxy;
  25 }
  26
  27 namespace content {
  28
  29 class CONTENT_EXPORT WebContentsTracker
  30     : public base::RefCountedThreadSafe<WebContentsTracker>,
  31       public WebContentsObserver {
  32  public:
  33   WebContentsTracker();
  34
  35   // Callback for whenever the target is swapped.  The callback is also invoked
  36   // with both arguments set to MSG_ROUTING_NONE to indicate tracking will not
  37   // continue (i.e., the WebContents instance was not found or has been
  38   // destroyed).
  39   typedef base::Callback<void(int render_process_id, int render_view_id)>
  40       ChangeCallback;
  41
  42   // Start tracking.  The last-known |render_process_id| and |render_view_id|
  43   // are provided, and the given callback is invoked asynchronously one or more
  44   // times.  The callback will be invoked on the same thread calling Start().
  45   virtual void Start(int render_process_id, int render_view_id,
  46                      const ChangeCallback& callback);
  47
  48   // Stop tracking.  Once this method returns, the callback is guaranteed not to
  49   // be invoked again.
  50   virtual void Stop();
  51
  52  protected:
  53   friend class base::RefCountedThreadSafe<WebContentsTracker>;
  54   virtual ~WebContentsTracker();
  55
  56  private:
  57   // Reads the render_process_id/render_view_id from the current WebContents
  58   // instance and then invokes the callback.
  59   void OnWebContentsChangeEvent();
  60
  61   // Called on the thread that Start()/Stop() are called on, check whether the
  62   // callback is still valid and, if so, invoke it.
  63   void MaybeDoCallback(int render_process_id, int render_view_id);
  64
  65   // Look-up the current WebContents instance associated with the given
  66   // |render_process_id| and |render_view_id| and begin observing it.
  67   void LookUpAndObserveWebContents(int render_process_id,
  68                                    int render_view_id);
  69
  70   // WebContentsObserver overrides to react to events of interest.
  71   virtual void RenderViewReady() OVERRIDE;
  72   virtual void AboutToNavigateRenderView(RenderViewHost* render_view_host)
  73       OVERRIDE;
  74   virtual void DidNavigateMainFrame(const LoadCommittedDetails& details,
  75                                     const FrameNavigateParams& params) OVERRIDE;
  76   virtual void WebContentsDestroyed(WebContents* web_contents) OVERRIDE;
  77
  78   scoped_refptr<base::MessageLoopProxy> message_loop_;
  79   ChangeCallback callback_;
  80
  81   DISALLOW_COPY_AND_ASSIGN(WebContentsTracker);
  82 };
  83
  84 }  // namespace content
  85
  86 #endif  // CONTENT_BROWSER_RENDERER_HOST_MEDIA_WEB_CONTENTS_TRACKER_H_