Optimize BlinkAXTreeSource by adding freeze/thaw for things like root, focus.

content/renderer/accessibility/blink_ax_tree_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 "content/renderer/accessibility/blink_ax_tree_source.h"
 
 #include <stddef.h>
 
 #include <set>
 
@@ skipping 93 matching lines @@
                                        AXContentNodeData* dst) {
   std::vector<int32_t> ids;
   for(size_t i = 0; i < objects.size(); i++)
     ids.push_back(objects[i].axID());
   if (ids.size() > 0)
     dst->AddIntListAttribute(attr, ids);
 }
 
 }  // namespace
 
+ScopedFreezeBlinkAXTreeSource::ScopedFreezeBlinkAXTreeSource(
+    BlinkAXTreeSource* tree_source)
+    : tree_source_(tree_source) {
+  tree_source_->Freeze();
+}

[David Tseng, 2016/09/07 18:59:27]

nit: indent

[dmazzoni, 2016/09/08 05:26:43]

I'm not 100% sure what indentation error you saw, but to be safe I just ran "git
cl format" and accepted all of its suggestions, so it should be fine now.

+
+ScopedFreezeBlinkAXTreeSource::~ScopedFreezeBlinkAXTreeSource() {
+  tree_source_->Thaw();
+}
+
 BlinkAXTreeSource::BlinkAXTreeSource(RenderFrameImpl* render_frame)
     : render_frame_(render_frame),
-      accessibility_focus_id_(-1) {
+      accessibility_focus_id_(-1),
+      frozen_(false) {
 }
 
 BlinkAXTreeSource::~BlinkAXTreeSource() {
 }
 
+void BlinkAXTreeSource::Freeze() {
+  CHECK(!frozen_);
+
+  if (render_frame_ && render_frame_->GetWebFrame())
+    document_ = render_frame_->GetWebFrame()->document();
+  else
+    document_ = WebDocument();
+
+  if (!explicit_root_.isNull())
+    root_ = explicit_root_;
+  else if (!document_.isNull())
+    root_ = document_.accessibilityObject();
+  else
+    root_ = WebAXObject();
+
+  if (!document_.isNull())
+    focus_ = document_.focusedAccessibilityObject();
+  else
+    focus_ = WebAXObject();
+
+  frozen_ = true;
+}
+

[David Tseng, 2016/09/07 18:59:27]

Could we move this to the beginning of the function?

[dmazzoni, 2016/09/08 05:26:43]

Sure, done.

+void BlinkAXTreeSource::Thaw() {
+  CHECK(frozen_);
+  frozen_ = false;
+}
+
 void BlinkAXTreeSource::SetRoot(blink::WebAXObject root) {
-  root_ = root;
+  CHECK(!frozen_);
+  explicit_root_ = root;
 }
 
 bool BlinkAXTreeSource::IsInTree(blink::WebAXObject node) const {
-  const blink::WebAXObject& root = GetRoot();
+  CHECK(frozen_);
   while (IsValid(node)) {
-    if (node.equals(root))
+    if (node.equals(root_))
       return true;
     node = GetParent(node);
   }
   return false;
 }
 
 bool BlinkAXTreeSource::GetTreeData(AXContentTreeData* tree_data) const {
-  blink::WebDocument document = BlinkAXTreeSource::GetMainDocument();
-  const blink::WebAXObject& root = GetRoot();
+  CHECK(frozen_);
+  tree_data->doctype = "html";
+  tree_data->loaded = root_.isLoaded();
+  tree_data->loading_progress = root_.estimatedLoadingProgress();
+  tree_data->mimetype =
+      document_.isXHTMLDocument() ? "text/xhtml" : "text/html";
+  tree_data->title = document_.title().utf8();
+  tree_data->url = document_.url().string().utf8();
 
-  tree_data->doctype = "html";
-  tree_data->loaded = root.isLoaded();
-  tree_data->loading_progress = root.estimatedLoadingProgress();
-  tree_data->mimetype = document.isXHTMLDocument() ? "text/xhtml" : "text/html";
-  tree_data->title = document.title().utf8();
-  tree_data->url = document.url().string().utf8();
-
-  WebAXObject focus = document.focusedAccessibilityObject();
-  if (!focus.isNull())
-    tree_data->focus_id = focus.axID();
+  if (!focus_.isNull())
+    tree_data->focus_id = focus_.axID();
 
   WebAXObject anchor_object, focus_object;
   int anchor_offset, focus_offset;
   blink::WebAXTextAffinity anchor_affinity, focus_affinity;
-  root.selection(anchor_object, anchor_offset, anchor_affinity,
-                 focus_object, focus_offset, focus_affinity);
+  root_.selection(anchor_object, anchor_offset, anchor_affinity,
+                  focus_object, focus_offset, focus_affinity);
   if (!anchor_object.isNull() && !focus_object.isNull() &&
       anchor_offset >= 0 && focus_offset >= 0) {
     int32_t anchor_id = anchor_object.axID();
     int32_t focus_id = focus_object.axID();
     tree_data->sel_anchor_object_id = anchor_id;
     tree_data->sel_anchor_offset = anchor_offset;
     tree_data->sel_focus_object_id = focus_id;
     tree_data->sel_focus_offset = focus_offset;
     tree_data->sel_anchor_affinity = AXTextAffinityFromBlink(anchor_affinity);
     tree_data->sel_focus_affinity = AXTextAffinityFromBlink(focus_affinity);
   }
 
   // Get the tree ID for this frame and the parent frame.
-  WebLocalFrame* web_frame = document.frame();
+  WebLocalFrame* web_frame = document_.frame();
   if (web_frame) {
     RenderFrame* render_frame = RenderFrame::FromWebFrame(web_frame);
     tree_data->routing_id = render_frame->GetRoutingID();
 
     // Get the tree ID for the parent frame.
     blink::WebFrame* parent_web_frame = web_frame->parent();
     if (parent_web_frame) {
       tree_data->parent_routing_id =
           GetRoutingIdForFrameOrProxy(parent_web_frame);
     }
   }
 
   return true;
 }
 
 blink::WebAXObject BlinkAXTreeSource::GetRoot() const {
-  if (!root_.isNull())
-    return root_;
-  return GetMainDocument().accessibilityObject();
+  CHECK(frozen_);
+  return root_;
 }
 
 blink::WebAXObject BlinkAXTreeSource::GetFromId(int32_t id) const {
   return GetMainDocument().accessibilityObjectFromID(id);
 }
 
 int32_t BlinkAXTreeSource::GetId(blink::WebAXObject node) const {
   return node.axID();
 }
 
 void BlinkAXTreeSource::GetChildren(
     blink::WebAXObject parent,
     std::vector<blink::WebAXObject>* out_children) const {
+  CHECK(frozen_);
+
   if (parent.role() == blink::WebAXRoleStaticText) {
     blink::WebAXObject ancestor = parent;
     while (!ancestor.isDetached()) {
-      int32_t focus_id = GetMainDocument().focusedAccessibilityObject().axID();
+      int32_t focus_id = focus_.axID();
       if (ancestor.axID() == accessibility_focus_id_ ||
           (ancestor.axID() == focus_id && ancestor.isEditable())) {
         parent.loadInlineTextBoxes();
         break;
       }
       ancestor = ancestor.parentObject();
     }
   }
 
   bool is_iframe = false;
@@ skipping 12 matching lines @@
     // As an exception, include children of an iframe element.
     if (!is_iframe && !IsParentUnignoredOf(parent, child))
       continue;
 
     out_children->push_back(child);
   }
 }
 
 blink::WebAXObject BlinkAXTreeSource::GetParent(
     blink::WebAXObject node) const {
+  CHECK(frozen_);
+
   // Blink returns ignored objects when walking up the parent chain,
   // we have to skip those here. Also, stop when we get to the root
   // element.
-  blink::WebAXObject root = GetRoot();
   do {
-    if (node.equals(root))
+    if (node.equals(root_))
       return blink::WebAXObject();
     node = node.parentObject();
   } while (!node.isDetached() && node.accessibilityIsIgnored());
 
   return node;
 }
 
 bool BlinkAXTreeSource::IsValid(blink::WebAXObject node) const {
   return !node.isDetached();  // This also checks if it's null.
 }
@@ skipping 428 matching lines @@
     dst->AddIntAttribute(ui::AX_ATTR_SCROLL_X_MIN, minScrollOffset.x());
     dst->AddIntAttribute(ui::AX_ATTR_SCROLL_Y_MIN, minScrollOffset.y());
 
     const gfx::Point& maxScrollOffset = src.maximumScrollOffset();
     dst->AddIntAttribute(ui::AX_ATTR_SCROLL_X_MAX, maxScrollOffset.x());
     dst->AddIntAttribute(ui::AX_ATTR_SCROLL_Y_MAX, maxScrollOffset.y());
   }
 }
 
 blink::WebDocument BlinkAXTreeSource::GetMainDocument() const {
-  if (render_frame_ && render_frame_->GetWebFrame())
-    return render_frame_->GetWebFrame()->document();
-  return WebDocument();
+  CHECK(frozen_);
+  return document_;
 }
 
 }  // namespace content