content/browser/frame_host/navigation_entry_screenshot_manager.cc

   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 #include "content/browser/frame_host/navigation_entry_screenshot_manager.h"
   6
   7 #include "base/command_line.h"
   8 #include "base/threading/worker_pool.h"
   9 #include "content/browser/frame_host/navigation_controller_impl.h"
  10 #include "content/browser/frame_host/navigation_entry_impl.h"
  11 #include "content/browser/renderer_host/render_view_host_impl.h"
  12 #include "content/public/browser/overscroll_configuration.h"
  13 #include "content/public/browser/render_widget_host.h"
  14 #include "content/public/browser/render_widget_host_view.h"
  15 #include "content/public/common/content_switches.h"
  16 #include "ui/gfx/codec/png_codec.h"
  17
  18 namespace {
  19
  20 // Minimum delay between taking screenshots.
  21 const int kMinScreenshotIntervalMS = 1000;
  22
  23 }
  24
  25 namespace content {
  26
  27 // Encodes the A8 SkBitmap to grayscale PNG in a worker thread.
  28 class ScreenshotData : public base::RefCountedThreadSafe<ScreenshotData> {
  29  public:
  30   ScreenshotData() {
  31   }
  32
  33   void EncodeScreenshot(const SkBitmap& bitmap, base::Closure callback) {
  34     if (!base::WorkerPool::PostTaskAndReply(FROM_HERE,
  35             base::Bind(&ScreenshotData::EncodeOnWorker,
  36                        this,
  37                        bitmap),
  38             callback,
  39             true)) {
  40       callback.Run();
  41     }
  42   }
  43
  44   scoped_refptr<base::RefCountedBytes> data() const { return data_; }
  45
  46  private:
  47   friend class base::RefCountedThreadSafe<ScreenshotData>;
  48   virtual ~ScreenshotData() {
  49   }
  50
  51   void EncodeOnWorker(const SkBitmap& bitmap) {
  52     DCHECK_EQ(bitmap.colorType(), kAlpha_8_SkColorType);
  53     // Encode the A8 bitmap to grayscale PNG treating alpha as color intensity.
  54     std::vector<unsigned char> data;
  55     if (gfx::PNGCodec::EncodeA8SkBitmap(bitmap, &data))
  56       data_ = new base::RefCountedBytes(data);
  57   }
  58
  59   scoped_refptr<base::RefCountedBytes> data_;
  60
  61   DISALLOW_COPY_AND_ASSIGN(ScreenshotData);
  62 };
  63
  64 NavigationEntryScreenshotManager::NavigationEntryScreenshotManager(
  65     NavigationControllerImpl* owner)
  66     : owner_(owner),
  67       min_screenshot_interval_ms_(kMinScreenshotIntervalMS),
  68       screenshot_factory_(this) {
  69
  70 }
  71
  72 NavigationEntryScreenshotManager::~NavigationEntryScreenshotManager() {
  73 }
  74
  75 void NavigationEntryScreenshotManager::TakeScreenshot() {
  76   static bool overscroll_enabled = base::CommandLine::ForCurrentProcess()->
  77       GetSwitchValueASCII(switches::kOverscrollHistoryNavigation) != "0";
  78   if (!overscroll_enabled)
  79     return;
  80
  81   NavigationEntryImpl* entry = owner_->GetLastCommittedEntry();
  82   if (!entry)
  83     return;
  84
  85   if (!owner_->delegate()->CanOverscrollContent())
  86     return;
  87
  88   RenderViewHost* render_view_host =
  89       owner_->delegate()->GetRenderViewHost();
  90   content::RenderWidgetHostView* view = render_view_host->GetView();
  91   if (!view)
  92     return;
  93
  94   // Make sure screenshots aren't taken too frequently.
  95   base::Time now = base::Time::Now();
  96   if (now - last_screenshot_time_ <
  97           base::TimeDelta::FromMilliseconds(min_screenshot_interval_ms_)) {
  98     return;
  99   }
 100
 101   last_screenshot_time_ = now;
 102
 103   TakeScreenshotImpl(render_view_host, entry);
 104 }
 105
 106 // Implemented here and not in NavigationEntry because this manager keeps track
 107 // of the total number of screen shots across all entries.
 108 void NavigationEntryScreenshotManager::ClearAllScreenshots() {
 109   int count = owner_->GetEntryCount();
 110   for (int i = 0; i < count; ++i) {
 111     ClearScreenshot(owner_->GetEntryAtIndex(i));
 112   }
 113   DCHECK_EQ(GetScreenshotCount(), 0);
 114 }
 115
 116 void NavigationEntryScreenshotManager::TakeScreenshotImpl(
 117     RenderViewHost* host,
 118     NavigationEntryImpl* entry) {
 119   DCHECK(host && host->GetView());
 120   DCHECK(entry);
 121   host->CopyFromBackingStore(
 122       gfx::Rect(),
 123       host->GetView()->GetViewBounds().size(),
 124       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotTaken,
 125                  screenshot_factory_.GetWeakPtr(),
 126                  entry->GetUniqueID()),
 127       kAlpha_8_SkColorType);
 128 }
 129
 130 void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
 131     int interval_ms) {
 132   DCHECK_GE(interval_ms, 0);
 133   min_screenshot_interval_ms_ = interval_ms;
 134 }
 135
 136 void NavigationEntryScreenshotManager::OnScreenshotTaken(
 137     int unique_id,
 138     const SkBitmap& bitmap,
 139     ReadbackResponse response) {
 140   NavigationEntryImpl* entry = NULL;
 141   int entry_count = owner_->GetEntryCount();
 142   for (int i = 0; i < entry_count; ++i) {
 143     NavigationEntryImpl* iter = owner_->GetEntryAtIndex(i);
 144     if (iter->GetUniqueID() == unique_id) {
 145       entry = iter;
 146       break;
 147     }
 148   }
 149
 150   if (!entry) {
 151     LOG(ERROR) << "Invalid entry with unique id: " << unique_id;
 152     return;
 153   }
 154
 155   if ((response != READBACK_SUCCESS) || bitmap.empty() || bitmap.isNull()) {
 156     if (!ClearScreenshot(entry))
 157       OnScreenshotSet(entry);
 158     return;
 159   }
 160
 161   scoped_refptr<ScreenshotData> screenshot = new ScreenshotData();
 162   screenshot->EncodeScreenshot(
 163       bitmap,
 164       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotEncodeComplete,
 165                  screenshot_factory_.GetWeakPtr(),
 166                  unique_id,
 167                  screenshot));
 168 }
 169
 170 int NavigationEntryScreenshotManager::GetScreenshotCount() const {
 171   int screenshot_count = 0;
 172   int entry_count = owner_->GetEntryCount();
 173   for (int i = 0; i < entry_count; ++i) {
 174     NavigationEntryImpl* entry = owner_->GetEntryAtIndex(i);
 175     if (entry->screenshot().get())
 176       screenshot_count++;
 177   }
 178   return screenshot_count;
 179 }
 180
 181 void NavigationEntryScreenshotManager::OnScreenshotEncodeComplete(
 182     int unique_id,
 183     scoped_refptr<ScreenshotData> screenshot) {
 184   NavigationEntryImpl* entry = NULL;
 185   int entry_count = owner_->GetEntryCount();
 186   for (int i = 0; i < entry_count; ++i) {
 187     NavigationEntryImpl* iter = owner_->GetEntryAtIndex(i);
 188     if (iter->GetUniqueID() == unique_id) {
 189       entry = iter;
 190       break;
 191     }
 192   }
 193   if (!entry)
 194     return;
 195   entry->SetScreenshotPNGData(screenshot->data());
 196   OnScreenshotSet(entry);
 197 }
 198
 199 void NavigationEntryScreenshotManager::OnScreenshotSet(
 200     NavigationEntryImpl* entry) {
 201   if (entry->screenshot().get())
 202     PurgeScreenshotsIfNecessary();
 203 }
 204
 205 bool NavigationEntryScreenshotManager::ClearScreenshot(
 206     NavigationEntryImpl* entry) {
 207   if (!entry->screenshot().get())
 208     return false;
 209
 210   entry->SetScreenshotPNGData(NULL);
 211   return true;
 212 }
 213
 214 void NavigationEntryScreenshotManager::PurgeScreenshotsIfNecessary() {
 215   // Allow only a certain number of entries to keep screenshots.
 216   const int kMaxScreenshots = 10;
 217   int screenshot_count = GetScreenshotCount();
 218   if (screenshot_count < kMaxScreenshots)
 219     return;
 220
 221   const int current = owner_->GetCurrentEntryIndex();
 222   const int num_entries = owner_->GetEntryCount();
 223   int available_slots = kMaxScreenshots;
 224   if (owner_->GetEntryAtIndex(current)->screenshot().get()) {
 225     --available_slots;
 226   }
 227
 228   // Keep screenshots closer to the current navigation entry, and purge the ones
 229   // that are farther away from it. So in each step, look at the entries at
 230   // each offset on both the back and forward history, and start counting them
 231   // to make sure that the correct number of screenshots are kept in memory.
 232   // Note that it is possible for some entries to be missing screenshots (e.g.
 233   // when taking the screenshot failed for some reason). So there may be a state
 234   // where there are a lot of entries in the back history, but none of them has
 235   // any screenshot. In such cases, keep the screenshots for |kMaxScreenshots|
 236   // entries in the forward history list.
 237   int back = current - 1;
 238   int forward = current + 1;
 239   while (available_slots > 0 && (back >= 0 || forward < num_entries)) {
 240     if (back >= 0) {
 241       NavigationEntryImpl* entry = owner_->GetEntryAtIndex(back);
 242       if (entry->screenshot().get())
 243         --available_slots;
 244       --back;
 245     }
 246
 247     if (available_slots > 0 && forward < num_entries) {
 248       NavigationEntryImpl* entry = owner_->GetEntryAtIndex(forward);
 249       if (entry->screenshot().get())
 250         --available_slots;
 251       ++forward;
 252     }
 253   }
 254
 255   // Purge any screenshot at |back| or lower indices, and |forward| or higher
 256   // indices.
 257   while (screenshot_count > kMaxScreenshots && back >= 0) {
 258     NavigationEntryImpl* entry = owner_->GetEntryAtIndex(back);
 259     if (ClearScreenshot(entry))
 260       --screenshot_count;
 261     --back;
 262   }
 263
 264   while (screenshot_count > kMaxScreenshots && forward < num_entries) {
 265     NavigationEntryImpl* entry = owner_->GetEntryAtIndex(forward);
 266     if (ClearScreenshot(entry))
 267       --screenshot_count;
 268     ++forward;
 269   }
 270   CHECK_GE(screenshot_count, 0);
 271   CHECK_LE(screenshot_count, kMaxScreenshots);
 272 }
 273
 274 }  // namespace content