navigation: Retain a screenshot of the page before it unloads

content/browser/web_contents/navigation_controller_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/navigation_controller_impl.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/logging.h"
 #include "base/string_number_conversions.h"  // Temporary
@@ skipping 10 matching lines @@
 #include "content/browser/web_contents/interstitial_page_impl.h"
 #include "content/browser/web_contents/navigation_entry_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/common/view_messages.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/invalidate_type.h"
 #include "content/public/browser/navigation_details.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
+#include "content/public/browser/render_widget_host.h"
+#include "content/public/browser/render_widget_host_view.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_contents_delegate.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_constants.h"
 #include "content/public/common/url_constants.h"
 #include "net/base/escape.h"
 #include "net/base/mime_util.h"
 #include "net/base/net_util.h"
+#include "skia/ext/platform_canvas.h"
+#include "ui/gfx/codec/png_codec.h"
 #include "webkit/glue/glue_serialize.h"
 
 namespace content {
 namespace {
 
 const int kInvalidateAll = 0xFFFFFFFF;
 
 // Invoked when entries have been pruned, or removed. For example, if the
 // current entries are [google, digg, yahoo], with the current entry google,
 // and the user types in cnet, then digg and yahoo are pruned.
@@ skipping 413 matching lines @@
   if (index < 0 || index >= GetEntryCount())
     return NULL;
 
   return entries_[index].get();
 }
 
 int NavigationControllerImpl::GetIndexForOffset(int offset) const {
   return GetCurrentEntryIndex() + offset;
 }
 
+void NavigationControllerImpl::TakeScreenshot() {
+  CHECK(web_contents_);
+
+  NavigationEntryImpl* active_entry =
+      NavigationEntryImpl::FromNavigationEntry(GetActiveEntry());
+  if (!active_entry)
+    return;
+
+  RenderViewHost* render_view_host = web_contents_->GetRenderViewHost();
+  content::RenderWidgetHostView* view = render_view_host->GetView();
+  if (!view)
+    return;
+
+  skia::PlatformBitmap* temp_bitmap = new skia::PlatformBitmap;
+  render_view_host->CopyFromBackingStore(gfx::Rect(),
+      view->GetViewBounds().size(),
+      base::Bind(&NavigationControllerImpl::TakingScreenshotComplete,
+                 base::Unretained(this),
+                 active_entry,
+                 base::Owned(temp_bitmap)),
+      temp_bitmap);
+}
+
+void NavigationControllerImpl::TakingScreenshotComplete(
+    NavigationEntryImpl* entry,
+    skia::PlatformBitmap* bitmap,
+    bool success) {
+  int index = GetIndexOfEntry(entry);
+  if (index < 0) {
+    LOG(ERROR) << "Invalid entry";
+    return;
+  }
+
+  if (!success) {
+    LOG(ERROR) << "Taking snapshot was unsuccessful for "
+               << entry->GetURL().spec();
+    return;
+  }
+
+  std::vector<unsigned char> data;
+  if (gfx::PNGCodec::EncodeBGRASkBitmap(bitmap->GetBitmap(), true, &data))
+    entry->SetScreenshotPNGData(data);
+}
+
 bool NavigationControllerImpl::CanGoBack() const {
   return entries_.size() > 1 && GetCurrentEntryIndex() > 0;
 }
 
 bool NavigationControllerImpl::CanGoForward() const {
   int index = GetCurrentEntryIndex();
   return index >= 0 && index < (static_cast<int>(entries_.size()) - 1);
 }
 
 bool NavigationControllerImpl::CanGoToOffset(int offset) const {
@@ skipping 951 matching lines @@
     DCHECK_EQ(max_entry_count(), entries_.size());
     DCHECK(last_committed_entry_index_ > 0);
     RemoveEntryAtIndex(0);
     NotifyPrunedEntries(this, true, 1);
   }
 }
 
 void NavigationControllerImpl::NavigateToPendingEntry(ReloadType reload_type) {
   needs_reload_ = false;
 
+  TakeScreenshot();

[sadrul, 2012/12/21 17:17:41]

Calling this here seems to work only for navigations that happen from the
browser (e.g. going back/forward in history, pressing enter in the omnibox
etc.), but not when doing a navigation from the page itself (e.g. clicking on a
link). Where should we take the screenshot in such cases?

+
   // If we were navigating to a slow-to-commit page, and the user performs
   // a session history navigation to the last committed page, RenderViewHost
   // will force the throbber to start, but WebKit will essentially ignore the
   // navigation, and won't send a message to stop the throbber. To prevent this
   // from happening, we drop the navigation here and stop the slow-to-commit
   // page from loading (which would normally happen during the navigation).
   if (pending_entry_index_ != -1 &&
       pending_entry_index_ == last_committed_entry_index_ &&
       (entries_[pending_entry_index_]->restore_type() ==
           NavigationEntryImpl::RESTORE_NONE) &&
@@ skipping 155 matching lines @@
     }
   }
 }
 
 void NavigationControllerImpl::SetGetTimestampCallbackForTest(
     const base::Callback<base::Time()>& get_timestamp_callback) {
   get_timestamp_callback_ = get_timestamp_callback;
 }
 
 }  // namespace content