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      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 #ifndef CHROME_BROWSER_THUMBNAILS_RENDER_WIDGET_SNAPSHOT_TAKER_H_
      6 #define CHROME_BROWSER_THUMBNAILS_RENDER_WIDGET_SNAPSHOT_TAKER_H_
      7 
      8 #include <map>
      9 
     10 #include "base/basictypes.h"
     11 #include "base/callback_forward.h"
     12 #include "base/gtest_prod_util.h"
     13 #include "base/memory/linked_ptr.h"
     14 #include "content/public/browser/notification_observer.h"
     15 #include "content/public/browser/notification_registrar.h"
     16 
     17 class SkBitmap;
     18 
     19 namespace content {
     20 class RenderWidgetHost;
     21 }
     22 
     23 namespace gfx {
     24 class Size;
     25 }
     26 
     27 class RenderWidgetSnapshotTaker : public content::NotificationObserver {
     28  public:
     29   typedef base::Callback<void(const SkBitmap&)> SnapshotReadyCallback;
     30 
     31   RenderWidgetSnapshotTaker();
     32   virtual ~RenderWidgetSnapshotTaker();
     33 
     34   // This registers a callback that can receive the resulting SkBitmap
     35   // from the renderer when it is done rendering it.  This is asynchronous,
     36   // and it will also fetch the bitmap even if the tab is hidden.
     37   // In addition, if the renderer has to be invoked, the scaling of
     38   // the thumbnail happens on the rendering thread.
     39   //
     40   // Takes ownership of the callback object.
     41   //
     42   // |page_size| is the size to render the page, and |desired_size| is
     43   // the size to scale the resulting rendered page to (which is done
     44   // efficiently if done in the rendering thread). The resulting image
     45   // will be less then twice the size of the |desired_size| in both
     46   // dimensions, but might not be the exact size requested.
     47   void AskForSnapshot(content::RenderWidgetHost* renderer,
     48                       const SnapshotReadyCallback& callback,
     49                       gfx::Size page_size,
     50                       gfx::Size desired_size);
     51 
     52   // Cancel any pending snapshots requested via AskForSnapshot.
     53   void CancelSnapshot(content::RenderWidgetHost* renderer);
     54 
     55  private:
     56   FRIEND_TEST_ALL_PREFIXES(RenderWidgetSnapshotTakerTest,
     57                            WidgetDidReceivePaintAtSizeAck);
     58   FRIEND_TEST_ALL_PREFIXES(RenderWidgetSnapshotTakerTest,
     59                            WidgetDidReceivePaintAtSizeAckFail);
     60 
     61   // content::NotificationObserver overrides.
     62   virtual void Observe(int type,
     63                        const content::NotificationSource& source,
     64                        const content::NotificationDetails& details) OVERRIDE;
     65 
     66   // Start or stop monitoring notifications for |renderer| based on the value
     67   // of |monitor|.
     68   void MonitorRenderer(content::RenderWidgetHost* renderer, bool monitor);
     69 
     70   void WidgetDidReceivePaintAtSizeAck(content::RenderWidgetHost* widget,
     71                                       int tag,
     72                                       const gfx::Size& size);
     73 
     74   content::NotificationRegistrar registrar_;
     75 
     76   // Map of callback objects by sequence number.
     77   struct AsyncRequestInfo;
     78   typedef std::map<int,
     79                    linked_ptr<AsyncRequestInfo> > SnapshotCallbackMap;
     80   SnapshotCallbackMap callback_map_;
     81 
     82   // Count of how many outstanding snapshot requests there are for each
     83   // RenderWidgetHost.
     84   std::map<content::RenderWidgetHost*, int> host_monitor_counts_;
     85 
     86   DISALLOW_COPY_AND_ASSIGN(RenderWidgetSnapshotTaker);
     87 };
     88 
     89 #endif  // CHROME_BROWSER_THUMBNAILS_RENDER_WIDGET_SNAPSHOT_TAKER_H_
     90