content/public/renderer/render_frame_observer_tracker.h

   1 // Copyright 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 // Helper class used to find the RenderFrameObservers for a given RenderFrame.
   6 //
   7 // Example usage:
   8 //
   9 //   class MyRFO : public RenderFrameObserver,
  10 //                 public RenderFrameObserverTracker<MyRFO> {
  11 //     ...
  12 //   };
  13 //
  14 //   MyRFO::MyRFO(RenderFrame* render_frame)
  15 //       : RenderFrameObserver(render_frame),
  16 //         RenderFrameObserverTracker<MyRFO>(render_frame) {
  17 //     ...
  18 //   }
  19 //
  20 //  void SomeFunction(RenderFrame* rf) {
  21 //    MyRFO* my_rfo = new MyRFO(rf);
  22 //    MyRFO* my_rfo_tracked = MyRFO::Get(rf);
  23 //    // my_rfo == my_rfo_tracked
  24 //  }
  25
  26 #ifndef CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
  27 #define CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_
  28
  29 #include <map>
  30
  31 #include "base/lazy_instance.h"
  32
  33 namespace content {
  34
  35 class RenderFrame;
  36
  37 template <class T>
  38 class RenderFrameObserverTracker {
  39  public:
  40   static T* Get(const RenderFrame* render_frame) {
  41     return static_cast<T*>(render_frame_map_.Get()[render_frame]);
  42   }
  43
  44   explicit RenderFrameObserverTracker(const RenderFrame* render_frame)
  45       : render_frame_(render_frame) {
  46     render_frame_map_.Get()[render_frame] = this;
  47   }
  48   ~RenderFrameObserverTracker() {
  49     render_frame_map_.Get().erase(render_frame_);
  50   }
  51
  52  private:
  53   const RenderFrame* render_frame_;
  54
  55   static base::LazyInstance<
  56       std::map<const RenderFrame*, RenderFrameObserverTracker<T>*>>
  57       render_frame_map_;
  58
  59   DISALLOW_COPY_AND_ASSIGN(RenderFrameObserverTracker<T>);
  60 };
  61
  62 template <class T>
  63 base::LazyInstance<std::map<const RenderFrame*,
  64                             RenderFrameObserverTracker<T>*>>
  65     RenderFrameObserverTracker<T>::render_frame_map_ =
  66         LAZY_INSTANCE_INITIALIZER;
  67
  68 }  // namespace content
  69
  70 #endif  // CONTENT_PUBLIC_RENDERER_RENDER_FRAME_OBSERVER_TRACKER_H_