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 =
  82       NavigationEntryImpl::FromNavigationEntry(owner_->GetLastCommittedEntry());
  83   if (!entry)
  84     return;
  85
  86   if (!owner_->delegate()->CanOverscrollContent())
  87     return;
  88
  89   RenderViewHost* render_view_host =
  90       owner_->delegate()->GetRenderViewHost();
  91   content::RenderWidgetHostView* view = render_view_host->GetView();
  92   if (!view)
  93     return;
  94
  95   // Make sure screenshots aren't taken too frequently.
  96   base::Time now = base::Time::Now();
  97   if (now - last_screenshot_time_ <
  98           base::TimeDelta::FromMilliseconds(min_screenshot_interval_ms_)) {
  99     return;
 100   }
 101
 102   last_screenshot_time_ = now;
 103
 104   TakeScreenshotImpl(render_view_host, entry);
 105 }
 106
 107 // Implemented here and not in NavigationEntry because this manager keeps track
 108 // of the total number of screen shots across all entries.
 109 void NavigationEntryScreenshotManager::ClearAllScreenshots() {
 110   int count = owner_->GetEntryCount();
 111   for (int i = 0; i < count; ++i) {
 112     ClearScreenshot(NavigationEntryImpl::FromNavigationEntry(
 113         owner_->GetEntryAtIndex(i)));
 114   }
 115   DCHECK_EQ(GetScreenshotCount(), 0);
 116 }
 117
 118 void NavigationEntryScreenshotManager::TakeScreenshotImpl(
 119     RenderViewHost* host,
 120     NavigationEntryImpl* entry) {
 121   DCHECK(host && host->GetView());
 122   DCHECK(entry);
 123   host->CopyFromBackingStore(
 124       gfx::Rect(),
 125       host->GetView()->GetViewBounds().size(),
 126       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotTaken,
 127                  screenshot_factory_.GetWeakPtr(),
 128                  entry->GetUniqueID()),
 129       kAlpha_8_SkColorType);
 130 }
 131
 132 void NavigationEntryScreenshotManager::SetMinScreenshotIntervalMS(
 133     int interval_ms) {
 134   DCHECK_GE(interval_ms, 0);
 135   min_screenshot_interval_ms_ = interval_ms;
 136 }
 137
 138 void NavigationEntryScreenshotManager::OnScreenshotTaken(int unique_id,
 139                                                      bool success,
 140                                                      const SkBitmap& bitmap) {
 141   NavigationEntryImpl* entry = NULL;
 142   int entry_count = owner_->GetEntryCount();
 143   for (int i = 0; i < entry_count; ++i) {
 144     NavigationEntry* iter = owner_->GetEntryAtIndex(i);
 145     if (iter->GetUniqueID() == unique_id) {
 146       entry = NavigationEntryImpl::FromNavigationEntry(iter);
 147       break;
 148     }
 149   }
 150
 151   if (!entry) {
 152     LOG(ERROR) << "Invalid entry with unique id: " << unique_id;
 153     return;
 154   }
 155
 156   if (!success || bitmap.empty() || bitmap.isNull()) {
 157     if (!ClearScreenshot(entry))
 158       OnScreenshotSet(entry);
 159     return;
 160   }
 161
 162   scoped_refptr<ScreenshotData> screenshot = new ScreenshotData();
 163   screenshot->EncodeScreenshot(
 164       bitmap,
 165       base::Bind(&NavigationEntryScreenshotManager::OnScreenshotEncodeComplete,
 166                  screenshot_factory_.GetWeakPtr(),
 167                  unique_id,
 168                  screenshot));
 169 }
 170
 171 int NavigationEntryScreenshotManager::GetScreenshotCount() const {
 172   int screenshot_count = 0;
 173   int entry_count = owner_->GetEntryCount();
 174   for (int i = 0; i < entry_count; ++i) {
 175     NavigationEntryImpl* entry =
 176         NavigationEntryImpl::FromNavigationEntry(owner_->GetEntryAtIndex(i));
 177     if (entry->screenshot().get())
 178       screenshot_count++;
 179   }
 180   return screenshot_count;
 181 }
 182
 183 void NavigationEntryScreenshotManager::OnScreenshotEncodeComplete(
 184     int unique_id,
 185     scoped_refptr<ScreenshotData> screenshot) {
 186   NavigationEntryImpl* entry = NULL;
 187   int entry_count = owner_->GetEntryCount();
 188   for (int i = 0; i < entry_count; ++i) {
 189     NavigationEntry* iter = owner_->GetEntryAtIndex(i);
 190     if (iter->GetUniqueID() == unique_id) {
 191       entry = NavigationEntryImpl::FromNavigationEntry(iter);
 192       break;
 193     }
 194   }
 195   if (!entry)
 196     return;
 197   entry->SetScreenshotPNGData(screenshot->data());
 198   OnScreenshotSet(entry);
 199 }
 200
 201 void NavigationEntryScreenshotManager::OnScreenshotSet(
 202     NavigationEntryImpl* entry) {
 203   if (entry->screenshot().get())
 204     PurgeScreenshotsIfNecessary();
 205 }
 206
 207 bool NavigationEntryScreenshotManager::ClearScreenshot(
 208     NavigationEntryImpl* entry) {
 209   if (!entry->screenshot().get())
 210     return false;
 211
 212   entry->SetScreenshotPNGData(NULL);
 213   return true;
 214 }
 215
 216 void NavigationEntryScreenshotManager::PurgeScreenshotsIfNecessary() {
 217   // Allow only a certain number of entries to keep screenshots.
 218   const int kMaxScreenshots = 10;
 219   int screenshot_count = GetScreenshotCount();
 220   if (screenshot_count < kMaxScreenshots)
 221     return;
 222
 223   const int current = owner_->GetCurrentEntryIndex();
 224   const int num_entries = owner_->GetEntryCount();
 225   int available_slots = kMaxScreenshots;
 226   if (NavigationEntryImpl::FromNavigationEntry(owner_->GetEntryAtIndex(current))
 227           ->screenshot().get()) {
 228     --available_slots;
 229   }
 230
 231   // Keep screenshots closer to the current navigation entry, and purge the ones
 232   // that are farther away from it. So in each step, look at the entries at
 233   // each offset on both the back and forward history, and start counting them
 234   // to make sure that the correct number of screenshots are kept in memory.
 235   // Note that it is possible for some entries to be missing screenshots (e.g.
 236   // when taking the screenshot failed for some reason). So there may be a state
 237   // where there are a lot of entries in the back history, but none of them has
 238   // any screenshot. In such cases, keep the screenshots for |kMaxScreenshots|
 239   // entries in the forward history list.
 240   int back = current - 1;
 241   int forward = current + 1;
 242   while (available_slots > 0 && (back >= 0 || forward < num_entries)) {
 243     if (back >= 0) {
 244       NavigationEntryImpl* entry = NavigationEntryImpl::FromNavigationEntry(
 245           owner_->GetEntryAtIndex(back));
 246       if (entry->screenshot().get())
 247         --available_slots;
 248       --back;
 249     }
 250
 251     if (available_slots > 0 && forward < num_entries) {
 252       NavigationEntryImpl* entry = NavigationEntryImpl::FromNavigationEntry(
 253           owner_->GetEntryAtIndex(forward));
 254       if (entry->screenshot().get())
 255         --available_slots;
 256       ++forward;
 257     }
 258   }
 259
 260   // Purge any screenshot at |back| or lower indices, and |forward| or higher
 261   // indices.
 262   while (screenshot_count > kMaxScreenshots && back >= 0) {
 263     NavigationEntryImpl* entry = NavigationEntryImpl::FromNavigationEntry(
 264         owner_->GetEntryAtIndex(back));
 265     if (ClearScreenshot(entry))
 266       --screenshot_count;
 267     --back;
 268   }
 269
 270   while (screenshot_count > kMaxScreenshots && forward < num_entries) {
 271     NavigationEntryImpl* entry = NavigationEntryImpl::FromNavigationEntry(
 272         owner_->GetEntryAtIndex(forward));
 273     if (ClearScreenshot(entry))
 274       --screenshot_count;
 275     ++forward;
 276   }
 277   CHECK_GE(screenshot_count, 0);
 278   CHECK_LE(screenshot_count, kMaxScreenshots);
 279 }
 280
 281 }  // namespace content