1// Copyright (c) 2011 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_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_
6#define CHROME_BROWSER_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_
7#pragma once
8
9#include <map>
10#include <utility>
11#include <vector>
12
13#include "base/basictypes.h"
14#include "base/callback.h"
15#include "base/memory/linked_ptr.h"
16#include "base/timer.h"
17#include "content/browser/renderer_host/backing_store.h"
18#include "content/common/notification_observer.h"
19#include "content/common/notification_registrar.h"
20
21class GURL;
22class Profile;
23class RenderWidgetHost;
24class SkBitmap;
25class TabContents;
26
27namespace history {
28class TopSites;
29}
30
31class ThumbnailGenerator : NotificationObserver {
32 public:
33  typedef Callback1<const SkBitmap&>::Type ThumbnailReadyCallback;
34  // The result of clipping. This can be used to determine if the
35  // generated thumbnail is good or not.
36  enum ClipResult {
37    // The source image is smaller.
38    kSourceIsSmaller,
39    // Wider than tall, clip horizontally.
40    kWiderThanTall,
41    // Taller than wide, clip vertically.
42    kTallerThanWide,
43    // The source and destination aspect ratios are identical.
44    kNotClipped,
45  };
46
47  // Bitmasks of options for generating a thumbnail.
48  enum ThumbnailOptions {
49    // No options.
50    kNoOptions = 0,
51    // Request a clipped thumbnail with the aspect ratio preserved.
52    kClippedThumbnail = 1 << 0,
53  };
54
55  // This class will do nothing until you call StartThumbnailing.
56  ThumbnailGenerator();
57  ~ThumbnailGenerator();
58
59  // Ensures that we're properly hooked in to generated thumbnails. This can
60  // be called repeatedly and with wild abandon to no ill effect.
61  void StartThumbnailing();
62
63  // This registers a callback that can receive the resulting SkBitmap
64  // from the renderer when it is done rendering it.  This differs
65  // from GetThumbnailForRenderer in that it may be asynchronous, and
66  // because it will also fetch the bitmap even if the tab is hidden.
67  // In addition, if the renderer has to be invoked, the scaling of
68  // the thumbnail happens on the rendering thread.
69  //
70  // Takes ownership of the callback object.
71  //
72  // If |prefer_backing_store| is set, then the function will try and
73  // use the backing store for the page if it exists.  |page_size| is
74  // the size to render the page, and |desired_size| is the size to
75  // scale the resulting rendered page to (which is done efficiently
76  // if done in the rendering thread).  If |prefer_backing_store| is
77  // set, and the backing store is used, then the resulting image will
78  // be less then twice the size of the |desired_size| in both
79  // dimensions, but might not be the exact size requested.
80  void AskForSnapshot(RenderWidgetHost* renderer,
81                      bool prefer_backing_store,
82                      ThumbnailReadyCallback* callback,
83                      gfx::Size page_size,
84                      gfx::Size desired_size);
85
86  // This returns a thumbnail of a fixed, small size for the given
87  // renderer.
88  SkBitmap GetThumbnailForRenderer(RenderWidgetHost* renderer) const;
89
90  // This returns a thumbnail of a fixed, small size for the given
91  // renderer. |options| is a bitmask of ThumbnailOptions. If
92  // |clip_result| is non-NULL, the result of clipping will be written.
93  SkBitmap GetThumbnailForRendererWithOptions(RenderWidgetHost* renderer,
94                                              int options,
95                                              ClipResult* clip_result) const;
96
97  // Start or stop monitoring notifications for |renderer| based on the value
98  // of |monitor|.
99  void MonitorRenderer(RenderWidgetHost* renderer, bool monitor);
100
101  // Calculates how "boring" a thumbnail is. The boring score is the
102  // 0,1 ranged percentage of pixels that are the most common
103  // luma. Higher boring scores indicate that a higher percentage of a
104  // bitmap are all the same brightness.
105  static double CalculateBoringScore(SkBitmap* bitmap);
106
107  // Gets the clipped bitmap from |bitmap| per the aspect ratio of the
108  // desired width and the desired height. For instance, if the input
109  // bitmap is vertically long (ex. 400x900) and the desired size is
110  // square (ex. 100x100), the clipped bitmap will be the top half of the
111  // input bitmap (400x400).
112  static SkBitmap GetClippedBitmap(const SkBitmap& bitmap,
113                                   int desired_width,
114                                   int desired_height,
115                                   ClipResult* clip_result);
116
117  // Update the thumbnail of the given tab contents if necessary.
118  void UpdateThumbnailIfNecessary(TabContents* tab_contents);
119
120  // Returns true if we should update the thumbnail of the given URL.
121  static bool ShouldUpdateThumbnail(Profile* profile,
122                                    history::TopSites* top_sites,
123                                    const GURL& url);
124
125 private:
126  virtual void WidgetDidReceivePaintAtSizeAck(
127      RenderWidgetHost* widget,
128      int tag,
129      const gfx::Size& size);
130
131  // NotificationObserver interface.
132  virtual void Observe(NotificationType type,
133                       const NotificationSource& source,
134                       const NotificationDetails& details);
135
136  // Indicates that the given widget has changed is visibility.
137  void WidgetHidden(RenderWidgetHost* widget);
138
139  // Called when the given tab contents are disconnected (either
140  // through being closed, or because the renderer is no longer there).
141  void TabContentsDisconnected(TabContents* contents);
142
143  NotificationRegistrar registrar_;
144
145  // Map of callback objects by sequence number.
146  struct AsyncRequestInfo;
147  typedef std::map<int,
148                   linked_ptr<AsyncRequestInfo> > ThumbnailCallbackMap;
149  ThumbnailCallbackMap callback_map_;
150
151  DISALLOW_COPY_AND_ASSIGN(ThumbnailGenerator);
152};
153
154#endif  // CHROME_BROWSER_TAB_CONTENTS_THUMBNAIL_GENERATOR_H_
155