content/public/renderer/render_view_observer_tracker.h

   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
  33 namespace content {
  34
  35 class RenderView;
  36
  37 template <class T>
  38 class 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
  61 template <class T>
  62 base::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_