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