Implement declarativeContent API.

chrome/renderer/extensions/content_watcher.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 "chrome/common/extensions/extension_messages.h"
+#include "chrome/renderer/extensions/chrome_v8_context.h"
+#include "chrome/renderer/extensions/chrome_v8_extension.h"
+#include "chrome/renderer/extensions/content_watcher.h"
+#include "chrome/renderer/extensions/dispatcher.h"
+#include "content/public/renderer/render_view.h"
+#include "content/public/renderer/render_view_visitor.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebDocument.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebFrame.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebView.h"
+
+namespace extensions {
+
+namespace {
+class MutationHandler : public ChromeV8Extension {
+ public:
+  explicit MutationHandler(Dispatcher* dispatcher,
+                           base::WeakPtr<ContentWatcher> content_watcher)
+      : ChromeV8Extension(dispatcher),
+        content_watcher_(content_watcher) {
+    RouteFunction("FrameMutated",
+                  base::Bind(&MutationHandler::FrameMutated,
+                             base::Unretained(this)));
+  }
+
+ private:
+  v8::Handle<v8::Value> FrameMutated(const v8::Arguments& args) {
+    if (content_watcher_) {
+      content_watcher_->ScanAndNotify(
+          WebKit::WebFrame::frameForCurrentContext());
+    }
+    return v8::Undefined();
+  }
+
+  base::WeakPtr<ContentWatcher> content_watcher_;
+};
+
+}  // namespace
+
+ContentWatcher::ContentWatcher(Dispatcher* dispatcher)
+    : weak_ptr_factory_(this),
+      dispatcher_(dispatcher) {}
+ContentWatcher::~ContentWatcher() {}
+
+scoped_ptr<NativeHandler> ContentWatcher::MakeNatives() {
+  return scoped_ptr<NativeHandler>(
+      new MutationHandler(dispatcher_, weak_ptr_factory_.GetWeakPtr()));
+}
+
+void ContentWatcher::OnWatchPages(
+    const std::vector<std::string>& new_css_selectors) {
+  if (new_css_selectors == css_selectors_)
+    return;
+
+  css_selectors_ = new_css_selectors;
+
+  for (std::map<WebKit::WebFrame*,
+                std::vector<base::StringPiece> >::iterator
+           it = matching_selectors_.begin();
+       it != matching_selectors_.end(); ++it) {
+    WebKit::WebFrame* frame = it->first;
+    if (!css_selectors_.empty())
+      EnsureWatchingMutations(frame);
+
+    // Make sure to replace the contents of it->second because it contains
+    // dangling StringPieces that referred into the old css_selectors_ content.
+    it->second = FindMatchingSelectors(frame);
+  }
+
+  // For each top-level frame, inform the browser about its new matching set of
+  // selectors.
+  struct NotifyVisitor : public content::RenderViewVisitor {
+    explicit NotifyVisitor(ContentWatcher* watcher) : watcher_(watcher) {}
+    virtual bool Visit(content::RenderView* view) {
+      watcher_->NotifyBrowserOfChange(view->GetWebView()->mainFrame());
+      return true;  // Continue visiting.
+    }
+    ContentWatcher* watcher_;
+  };
+  NotifyVisitor visitor(this);
+  content::RenderView::ForEach(&visitor);
+}
+
+void ContentWatcher::DidCreateDocumentElement(WebKit::WebFrame* frame) {
+  // Make sure the frame is represented in the matching_selectors_ map.
+  matching_selectors_[frame];
+
+  if (!css_selectors_.empty()) {
+    EnsureWatchingMutations(frame);
+  }
+}
+
+void ContentWatcher::EnsureWatchingMutations(WebKit::WebFrame* frame) {
+  v8::HandleScope scope;
+  v8::Context::Scope context_scope(frame->mainWorldScriptContext());
+  if (ModuleSystem* module_system = GetModuleSystem(frame)) {
+    ModuleSystem::NativesEnabledScope scope(module_system);
+    module_system->Require("contentWatcher");
+  }
+}
+
+ModuleSystem* ContentWatcher::GetModuleSystem(WebKit::WebFrame* frame) const {
+  ChromeV8Context* v8_context =
+      dispatcher_->v8_context_set().GetByV8Context(
+          frame->mainWorldScriptContext());
+
+  if (!v8_context)
+    return NULL;
+  return v8_context->module_system();
+}
+
+void ContentWatcher::ScanAndNotify(WebKit::WebFrame* frame) {
+  std::vector<base::StringPiece> new_matches = FindMatchingSelectors(frame);
+  std::vector<base::StringPiece>& old_matches = matching_selectors_[frame];
+  if (new_matches == old_matches)
+    return;
+
+  using std::swap;

[Matt Perry, 2013/01/24 01:55:17]

err... why :)

[Jeffrey Yasskin, 2013/01/24 03:10:22]

It has the same effect in this case, because old_matches is in namespace std,
but it's the right habit to be in when calling swap(), since calling std::swap()
directly does the wrong thing for types outside the STL, and unqualified swap()
doesn't work for primitive types.

+  swap(old_matches, new_matches);
+  NotifyBrowserOfChange(frame);
+}
+
+std::vector<base::StringPiece> ContentWatcher::FindMatchingSelectors(
+    WebKit::WebFrame* frame) const {
+  std::vector<base::StringPiece> result;
+  v8::HandleScope scope;
+
+  // Get the indices within |css_selectors_| that match elements in
+  // |frame|, as a JS Array.
+  v8::Local<v8::Value> selector_indices;
+  if (ModuleSystem* module_system = GetModuleSystem(frame)) {
+    v8::Context::Scope context_scope(frame->mainWorldScriptContext());
+    v8::Local<v8::Array> js_css_selectors =
+        v8::Array::New(css_selectors_.size());
+    for (size_t i = 0; i < css_selectors_.size(); ++i) {
+      js_css_selectors->Set(i, v8::String::New(css_selectors_[i].c_str(),

[Matt Perry, 2013/01/24 01:55:17]

nit: use data() in conjunction with size() since c_str potentially reallocs the
string to add a null.

[Jeffrey Yasskin, 2013/01/24 03:10:22]

Done.

+                                               css_selectors_[i].size()));
+    }
+    std::vector<v8::Handle<v8::Value> > find_selectors_args;
+    find_selectors_args.push_back(js_css_selectors);
+    selector_indices = module_system->CallModuleMethod("contentWatcher",
+                                                       "FindMatchingSelectors",
+                                                       &find_selectors_args);
+  }
+  if (selector_indices.IsEmpty() || !selector_indices->IsArray())
+    return result;
+
+  // Iterate over the array, and extract the indices, laboriously
+  // converting them back to integers.
+  v8::Local<v8::Array> index_array = selector_indices.As<v8::Array>();
+  const size_t length = index_array->Length();
+  result.reserve(length);
+  for (size_t i = 0; i < length; ++i) {
+    v8::Local<v8::Value> index_value = index_array->Get(i);
+    if (!index_value->IsNumber())
+      continue;
+    double index = index_value->NumberValue();
+    // Make sure the index is within bounds.
+    if (index < 0 || css_selectors_.size() <= index)
+      continue;
+    // Push a StringPiece referring to the CSS selector onto the result.
+    result.push_back(
+        base::StringPiece(css_selectors_[static_cast<size_t>(index)]));
+  }
+  return result;
+}
+
+void ContentWatcher::NotifyBrowserOfChange(
+    WebKit::WebFrame* changed_frame) const {
+  WebKit::WebFrame* const top_frame = changed_frame->top();
+  const WebKit::WebSecurityOrigin top_origin =
+      top_frame->document().securityOrigin();
+  // Want to aggregate matched selectors from all frames where an
+  // extension with access to top_origin could run on the frame.
+  if (!top_origin.canAccess(changed_frame->document().securityOrigin())) {
+    // If the changed frame can't be accessed by the top frame, than

[Matt Perry, 2013/01/24 01:55:17]

then*

[Jeffrey Yasskin, 2013/01/24 03:10:22]

Oops.

+    // no change in it could affect the set of selectors we'd send back.
+    return;
+  }
+
+  std::set<base::StringPiece> transitive_selectors;
+  for (WebKit::WebFrame* frame = top_frame; frame;
+       frame = frame->traverseNext(/*wrap=*/false)) {
+    if (top_origin.canAccess(frame->document().securityOrigin())) {
+      std::map<WebKit::WebFrame*,
+               std::vector<base::StringPiece> >::const_iterator
+          frame_selectors = matching_selectors_.find(frame);
+      if (frame_selectors != matching_selectors_.end()) {
+        transitive_selectors.insert(frame_selectors->second.begin(),
+                                    frame_selectors->second.end());
+      }
+    }
+  }
+  std::vector<std::string> selector_strings;
+  for (std::set<base::StringPiece>::const_iterator
+           it = transitive_selectors.begin();
+       it != transitive_selectors.end(); ++it)
+    selector_strings.push_back(it->as_string());
+  content::RenderView* view =
+      content::RenderView::FromWebView(top_frame->view());
+  view->Send(new ExtensionHostMsg_OnWatchedPageChange(
+      view->GetRoutingID(), selector_strings));
+}
+
+}  // namespace extensions