1// Copyright (c) 2012 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// Helper class used to find the RenderViewObservers for a given RenderView.
6//
7// Example usage:
8//
9//   class MyRVO : public RenderViewObserver,
10//                 public RenderViewObserverTracker<MyRVO> {
11//     ...
12//   };
13//
14//   MyRVO::MyRVO(RenderView* render_view)
15//       : RenderViewObserver(render_view),
16//         RenderViewObserverTracker<MyRVO>(render_view) {
17//     ...
18//   }
19//
20//  void SomeFunction(RenderView* rv) {
21//    MyRVO* my_rvo = new MyRVO(rv);
22//    MyRVO* my_rvo_tracked = MyRVO::Get(rv);
23//    // my_rvo == my_rvo_tracked
24//  }
25
26#ifndef CONTENT_PUBLIC_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_
27#define CONTENT_PUBLIC_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_
28
29#include <map>
30
31#include "base/lazy_instance.h"
32
33namespace content {
34
35class RenderView;
36
37template <class T>
38class RenderViewObserverTracker {
39 public:
40  static T* Get(const RenderView* render_view) {
41    return render_view_map_.Get()[render_view];
42  }
43
44  explicit RenderViewObserverTracker(const RenderView* render_view)
45      : render_view_(render_view) {
46    render_view_map_.Get()[render_view] = static_cast<T*>(this);
47  }
48  ~RenderViewObserverTracker() {
49    render_view_map_.Get().erase(render_view_);
50  }
51
52 private:
53  const RenderView* render_view_;
54
55  static base::LazyInstance<std::map<const RenderView*, T*> >
56    render_view_map_;
57
58  DISALLOW_COPY_AND_ASSIGN(RenderViewObserverTracker<T>);
59};
60
61template <class T>
62base::LazyInstance<std::map<const RenderView*, T*> >
63    RenderViewObserverTracker<T>::render_view_map_ = LAZY_INSTANCE_INITIALIZER;
64
65}  // namespace content
66
67#endif  // CONTENT_PUBLIC_RENDERER_RENDER_VIEW_OBSERVER_TRACKER_H_
68