[dom_distiller] Add support for incremental viewer.

components/dom_distiller/content/dom_distiller_viewer_source.cc

 // Copyright 2014 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 "components/dom_distiller/content/dom_distiller_viewer_source.h"
 
 #include <sstream>
 #include <string>
 #include <vector>
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
+#include "base/strings/utf_string_conversions.h"
 #include "components/dom_distiller/core/task_tracker.h"
 #include "components/dom_distiller/core/url_constants.h"
 #include "components/dom_distiller/core/viewer.h"
+#include "content/public/browser/navigation_details.h"
+#include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_view_host.h"
+#include "content/public/browser/web_contents.h"
+#include "content/public/browser/web_contents_observer.h"
+#include "net/base/url_util.h"
 #include "net/url_request/url_request.h"
 
 namespace dom_distiller {
 
 // Handles receiving data asynchronously for a specific entry, and passing
-// it along to the data callback for the data source.
+// it along to the data callback for the data source. Lifetime matches that of
+// the current main frame's page in the Viewer instance.
 class DomDistillerViewerSource::RequestViewerHandle
-    : public ViewRequestDelegate {
+    : public ViewRequestDelegate,
+      public content::WebContentsObserver {
  public:
   explicit RequestViewerHandle(
+      content::WebContents* web_contents,
+      const std::string& expected_scheme,
+      const std::string& expected_request_path,
       const content::URLDataSource::GotDataCallback& callback);
   virtual ~RequestViewerHandle();
 
   // ViewRequestDelegate implementation.
   virtual void OnArticleReady(
       const DistilledArticleProto* article_proto) OVERRIDE;
 
   virtual void OnArticleUpdated(
       ArticleDistillationUpdate article_update) OVERRIDE;
 
   void TakeViewerHandle(scoped_ptr<ViewerHandle> viewer_handle);
 
+  // WebContentsObserver:
+  virtual void DidNavigateMainFrame(
+      const content::LoadCommittedDetails& details,
+      const content::FrameNavigateParams& params) OVERRIDE;
+  virtual void RenderProcessGone(base::TerminationStatus status) OVERRIDE;
+  virtual void WebContentsDestroyed() OVERRIDE;
+  virtual void DidFinishLoad(
+      int64 frame_id,
+      const GURL& validated_url,
+      bool is_main_frame,
+      content::RenderViewHost* render_view_host) OVERRIDE;
+
  private:
+  // Sends JavaScript to the attached Viewer, buffering data if the viewer isn't
+  // ready.
+  void SendJavaScript(const std::string& buffer);
+
+  // Cancels the current view request. Once called, no updates will be
+  // propagated to the view, and the request to DomDistillerService will be
+  // cancelled.
+  void Cancel();
+
   // The handle to the view request towards the DomDistillerService. It
   // needs to be kept around to ensure the distillation request finishes.
   scoped_ptr<ViewerHandle> viewer_handle_;
 
-  // This holds the callback to where the data retrieved is sent back.
+  // WebContents associated with the Viewer's render process.
+  content::WebContents* web_contents_;
+
+  // The scheme hosting the current view request;
+  std::string expected_scheme_;
+
+  // The query path for the current view request.
+  std::string expected_request_path_;
+
+  // Holds the callback to where the data retrieved is sent back.
   content::URLDataSource::GotDataCallback callback_;
+
+  // Number of pages of the distilled article content that have been rendered by
+  // the viewer.
+  int page_count_;
+
+  // Whether the page is sufficiently initialized to handle updates from the
+  // distiller.
+  bool waiting_for_page_ready_;
+
+  // Temporary store of pending JavaScript if the page isn't ready to receive
+  // data from distillation.
+  std::string buffer_;
 };
 
 DomDistillerViewerSource::RequestViewerHandle::RequestViewerHandle(
+    content::WebContents* web_contents,
+    const std::string& expected_scheme,
+    const std::string& expected_request_path,
     const content::URLDataSource::GotDataCallback& callback)
-    : callback_(callback) {
+    : web_contents_(web_contents),
+      expected_scheme_(expected_scheme),
+      expected_request_path_(expected_request_path),
+      callback_(callback),
+      page_count_(0),
+      waiting_for_page_ready_(true) {
+  content::WebContentsObserver::Observe(web_contents_);
 }
 
 DomDistillerViewerSource::RequestViewerHandle::~RequestViewerHandle() {
+  // Balanced with constructor although can be a no-op if frame navigated away.
+  content::WebContentsObserver::Observe(NULL);
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::SendJavaScript(
+    const std::string& buffer) {
+  if (waiting_for_page_ready_) {
+    buffer_ += buffer;
+  } else {
+    if (web_contents_) {
+      web_contents_->GetMainFrame()->ExecuteJavaScript(
+          base::UTF8ToUTF16(buffer));
+    }
+  }
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::DidNavigateMainFrame(
+    const content::LoadCommittedDetails& details,
+    const content::FrameNavigateParams& params) {
+  const GURL& navigation = details.entry->GetURL();
+  if (details.is_in_page || (
+      navigation.SchemeIs(expected_scheme_.c_str()) &&
+      expected_request_path_ == navigation.query())) {
+    // In-page navigations, as well as the main view request can be ignored.
+    return;
+  }
+
+  Cancel();
+
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::RenderProcessGone(
+    base::TerminationStatus status) {
+  Cancel();
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::WebContentsDestroyed() {
+  Cancel();
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::Cancel() {
+  // Ensure we don't send any incremental updates to the Viewer.
+  web_contents_ = NULL;
+
+  // No need to listen for notifications.
+  content::WebContentsObserver::Observe(NULL);
+
+  // Schedule the Viewer for deletion. Ensures distillation is cancelled, and
+  // any pending data stored in |buffer_| is released.
+  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
+}
+
+void DomDistillerViewerSource::RequestViewerHandle::DidFinishLoad(
+     int64 frame_id,
+     const GURL& validated_url,
+     bool is_main_frame,
+     content::RenderViewHost* render_view_host)  {
+  if (!is_main_frame || web_contents_ == NULL) {
+    return;
+  }
+  waiting_for_page_ready_ = false;
+  if (buffer_.empty()) {
+    return;
+  }
+  if (web_contents_) {
+    web_contents_->GetMainFrame()->ExecuteJavaScript(
+        base::UTF8ToUTF16(buffer_));
+  }
+  buffer_.clear();
 }
 
 void DomDistillerViewerSource::RequestViewerHandle::OnArticleReady(
     const DistilledArticleProto* article_proto) {
-  std::string unsafe_page_html = viewer::GetUnsafeHtml(article_proto);
-  callback_.Run(base::RefCountedString::TakeString(&unsafe_page_html));
-  base::MessageLoop::current()->DeleteSoon(FROM_HERE, this);
+  if (page_count_ == 0) {
+    // This is a single-page article.
+    std::string unsafe_page_html = viewer::GetUnsafeArticleHtml(article_proto);
+    callback_.Run(base::RefCountedString::TakeString(&unsafe_page_html));
+  } else if (page_count_ == article_proto->pages_size()) {
+    // We may still be showing the "Loading" indicator.
+    SendJavaScript(viewer::GetToggleLoadingIndicatorJs(true));
+  } else {
+    // It's possible that we didn't get some incremental updates from the
+    // distiller. Ensure all remaining pages are flushed to the viewer.
+    for (;page_count_ < article_proto->pages_size(); page_count_++) {
+      const DistilledPageProto& page = article_proto->pages(page_count_);
+      SendJavaScript(
+          viewer::GetUnsafeIncrementalDistilledPageJs(
+              &page,
+              page_count_ == article_proto->pages_size()));
+    }
+  }
+  // No need to hold on to the ViewerHandle now that distillation is complete.
+  viewer_handle_.reset();
 }
 
 void DomDistillerViewerSource::RequestViewerHandle::OnArticleUpdated(
     ArticleDistillationUpdate article_update) {
-  // TODO(nyquist): Add support for displaying pages incrementally.
+  for (;page_count_ < static_cast<int>(article_update.GetPagesSize());
+       page_count_++) {
+    const DistilledPageProto& page =
+        article_update.GetDistilledPage(page_count_);
+    if (page_count_ == 0) {
+      // This is the first page, so send Viewer page scaffolding too.
+      std::string unsafe_page_html = viewer::GetUnsafePartialArticleHtml(&page);
+      callback_.Run(base::RefCountedString::TakeString(&unsafe_page_html));
+    } else {
+      SendJavaScript(
+          viewer::GetUnsafeIncrementalDistilledPageJs(&page, false));
+    }
+  }
 }
 
 void DomDistillerViewerSource::RequestViewerHandle::TakeViewerHandle(
     scoped_ptr<ViewerHandle> viewer_handle) {
   viewer_handle_ = viewer_handle.Pass();
 }
 
 DomDistillerViewerSource::DomDistillerViewerSource(
     DomDistillerServiceInterface* dom_distiller_service,
     const std::string& scheme)
@@ skipping 13 matching lines @@
     int render_frame_id,
     const content::URLDataSource::GotDataCallback& callback) {
   content::RenderFrameHost* render_frame_host =
       content::RenderFrameHost::FromID(render_process_id, render_frame_id);
   DCHECK(render_frame_host);
   content::RenderViewHost* render_view_host =
       render_frame_host->GetRenderViewHost();
   DCHECK(render_view_host);
   CHECK_EQ(0, render_view_host->GetEnabledBindings());
 
-  if (kCssPath == path) {
+  if (kViewerCssPath == path) {
     std::string css = viewer::GetCss();
     callback.Run(base::RefCountedString::TakeString(&css));
     return;
   }
-
+  if (kViewerJsPath == path) {
+    std::string js = viewer::GetJavaScript();
+    callback.Run(base::RefCountedString::TakeString(&js));
+    return;
+  }
+  content::WebContents* web_contents =
+      content::WebContents::FromRenderFrameHost(
+          content::RenderFrameHost::FromID(render_process_id,
+                                           render_frame_id));
+  DCHECK(web_contents);
   RequestViewerHandle* request_viewer_handle =
-      new RequestViewerHandle(callback);
+      new RequestViewerHandle(web_contents, scheme_, path.substr(1), callback);
   scoped_ptr<ViewerHandle> viewer_handle = viewer::CreateViewRequest(
       dom_distiller_service_, path, request_viewer_handle);
 
   if (viewer_handle) {
     // The service returned a |ViewerHandle| and guarantees it will call
     // the |RequestViewerHandle|, so passing ownership to it, to ensure the
     // request is not cancelled. The |RequestViewerHandle| will delete itself
     // after receiving the callback.
     request_viewer_handle->TakeViewerHandle(viewer_handle.Pass());
   } else {
     // The service did not return a |ViewerHandle|, which means the
     // |RequestViewerHandle| will never be called, so clean up now.
     delete request_viewer_handle;
 
     std::string error_page_html = viewer::GetErrorPageHtml();
     callback.Run(base::RefCountedString::TakeString(&error_page_html));
   }
 };
 
 std::string DomDistillerViewerSource::GetMimeType(
     const std::string& path) const {
-  if (path == kCssPath)
+  if (kViewerCssPath == path) {
     return "text/css";
+  }
+  if (kViewerJsPath == path) {
+    return "text/javascript";
+  }
   return "text/html";
 }
 
 bool DomDistillerViewerSource::ShouldServiceRequest(
     const net::URLRequest* request) const {
   return request->url().SchemeIs(scheme_.c_str());
 }
 
 // TODO(nyquist): Start tracking requests using this method.
 void DomDistillerViewerSource::WillServiceRequest(
     const net::URLRequest* request,
     std::string* path) const {

[nyquist, 2014/05/14 17:54:35]

Oh, and for future reference, you could abuse the |path| here and put the
hostname into it, and read it out again in StartDataRequest. That way it could
be mapped on the hostname as well in the RequestViewerHandle. But I'm okay with
not doing that now.

 }
 
 std::string DomDistillerViewerSource::GetContentSecurityPolicyObjectSrc()
     const {
   return "object-src 'none'; style-src 'self';";
 }
 
 }  // namespace dom_distiller