Rewrite renderer accessibility to not use WebAccessibilityCache.

content/renderer/renderer_accessibility.cc

+// Copyright (c) 2011 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 "base/command_line.h"
+#include "content/common/content_switches.h"
+#include "content/common/view_messages.h"
+#include "content/renderer/render_view.h"
+#include "content/renderer/renderer_accessibility.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebAccessibilityObject.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"
+#include "webkit/glue/webaccessibility.h"
+
+using WebKit::WebAccessibilityNotification;
+using WebKit::WebAccessibilityObject;
+using WebKit::WebDocument;
+using WebKit::WebFrame;
+using WebKit::WebNode;
+using WebKit::WebView;
+using webkit_glue::WebAccessibility;
+
+bool WebAccessibilityNotificationToViewHostMsg(
+    WebAccessibilityNotification notification,
+    ViewHostMsg_AccEvent::Value* type) {
+  switch (notification) {
+    case WebKit::WebAccessibilityNotificationActiveDescendantChanged:
+      *type = ViewHostMsg_AccEvent::ACTIVE_DESCENDANT_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationCheckedStateChanged:
+      *type = ViewHostMsg_AccEvent::CHECK_STATE_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationChildrenChanged:
+      *type = ViewHostMsg_AccEvent::CHILDREN_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationFocusedUIElementChanged:
+      *type = ViewHostMsg_AccEvent::FOCUS_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationLayoutComplete:
+      *type = ViewHostMsg_AccEvent::LAYOUT_COMPLETE;
+      break;
+    case WebKit::WebAccessibilityNotificationLiveRegionChanged:
+      *type = ViewHostMsg_AccEvent::LIVE_REGION_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationLoadComplete:
+      *type = ViewHostMsg_AccEvent::LOAD_COMPLETE;
+      break;
+    case WebKit::WebAccessibilityNotificationMenuListValueChanged:
+      *type = ViewHostMsg_AccEvent::MENU_LIST_VALUE_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationRowCollapsed:
+      *type = ViewHostMsg_AccEvent::ROW_COLLAPSED;
+      break;
+    case WebKit::WebAccessibilityNotificationRowCountChanged:
+      *type = ViewHostMsg_AccEvent::ROW_COUNT_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationRowExpanded:
+      *type = ViewHostMsg_AccEvent::ROW_EXPANDED;
+      break;
+    case WebKit::WebAccessibilityNotificationScrolledToAnchor:
+      *type = ViewHostMsg_AccEvent::SCROLLED_TO_ANCHOR;
+      break;
+    case WebKit::WebAccessibilityNotificationSelectedChildrenChanged:
+      *type = ViewHostMsg_AccEvent::SELECTED_CHILDREN_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationSelectedTextChanged:
+      *type = ViewHostMsg_AccEvent::SELECTED_TEXT_CHANGED;
+      break;
+    case WebKit::WebAccessibilityNotificationValueChanged:
+      *type = ViewHostMsg_AccEvent::VALUE_CHANGED;
+      break;
+    default:
+      return false;

[David Tseng, 2011/09/27 21:26:13]

NOTREACHED?

[dmazzoni, 2011/09/28 05:28:50]

Done.

+  }
+  return true;
+}
+
+RendererAccessibility::RendererAccessibility(RenderView* render_view)
+    : RenderViewObserver(render_view),
+      ALLOW_THIS_IN_INITIALIZER_LIST(method_factory_(this)),
+      browser_root_(NULL),
+      ack_pending_(false),
+      logging_(false),
+      sent_load_complete_(false) {
+  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  if (command_line.HasSwitch(switches::kEnableAccessibility))
+    WebAccessibilityObject::enableAccessibility();
+  if (command_line.HasSwitch(switches::kEnableAccessibilityLogging))
+    logging_ = true;
+}
+
+RendererAccessibility::~RendererAccessibility() {
+}
+
+bool RendererAccessibility::OnMessageReceived(const IPC::Message& message) {
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP(RendererAccessibility, message)
+    IPC_MESSAGE_HANDLER(ViewMsg_EnableAccessibility, OnEnableAccessibility)
+    IPC_MESSAGE_HANDLER(ViewMsg_SetAccessibilityFocus, OnSetAccessibilityFocus)
+    IPC_MESSAGE_HANDLER(ViewMsg_AccessibilityDoDefaultAction,
+                        OnAccessibilityDoDefaultAction)
+    IPC_MESSAGE_HANDLER(ViewMsg_AccessibilityNotifications_ACK,
+                        OnAccessibilityNotificationsAck)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  return handled;
+}
+
+void RendererAccessibility::FocusedNodeChanged(const WebNode& node) {
+  if (!WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;

[David Tseng, 2011/09/27 21:26:13]

Should this be a DCHECK?

[dmazzoni, 2011/09/28 05:28:50]

I don't think so; I hit this when the page was first loading or being torn down
and we received a stale notification.

+
+  if (node.isNull()) {
+    // When focus is cleared, implicitly focus the document.
+    // TODO(dmazzoni): Make WebKit send this notification instead.
+    PostAccessibilityNotification(
+        document.accessibilityObject(),
+        WebKit::WebAccessibilityNotificationFocusedUIElementChanged);
+  }
+}
+
+void RendererAccessibility::DidFinishLoad(WebKit::WebFrame* frame) {
+  if (!WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;
+
+  // Check to see if the root accessibility object has changed, to work
+  // around WebKit bugs that cause AXObjectCache to be cleared
+  // unnecessarily.
+  // TODO(dmazzoni): remove this once rdar://5794454 is fixed.
+  WebAccessibilityObject new_root = document.accessibilityObject();
+  if (!browser_root_ || new_root.axID() != browser_root_->id) {
+    PostAccessibilityNotification(
+        new_root,
+        WebKit::WebAccessibilityNotificationLoadComplete);
+  }
+}
+
+void RendererAccessibility::PostAccessibilityNotification(
+    const WebAccessibilityObject& obj,
+    WebAccessibilityNotification notification) {
+  if (!WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;

[David Tseng, 2011/09/27 21:26:13]

DCHECK?

+
+  if (notification != WebKit::WebAccessibilityNotificationLoadComplete &&
+      !sent_load_complete_) {
+    // Load complete should be our first notification sent. Send it manually
+    // in cases where we don't get it first to avoid focus problems.
+    PostAccessibilityNotification(
+        document.accessibilityObject(),
+        WebKit::WebAccessibilityNotificationLoadComplete);
+    sent_load_complete_ = true;

[David Tseng, 2011/09/27 21:26:13]

Is this necessary given the below if clause?

[dmazzoni, 2011/09/28 05:28:50]

Done.

+  }
+
+  if (notification == WebKit::WebAccessibilityNotificationLoadComplete)
+    sent_load_complete_ = true;
+
+  // Add the accessibility object to our cache and ensure it's valid.
+  Notification acc_notification;
+  acc_notification.id = obj.axID();
+  acc_notification.type = notification;
+
+  ViewHostMsg_AccEvent::Value temp;
+  if (!WebAccessibilityNotificationToViewHostMsg(notification, &temp))
+    return;
+
+  // Discard duplicate accessibility notifications.
+  for (uint32 i = 0; i < pending_notifications_.size(); i++) {

[David Tseng, 2011/09/27 21:26:13]

++i

[dmazzoni, 2011/09/28 05:28:50]

Fixed throughout.

+    if (pending_notifications_[i].id == acc_notification.id &&
+        pending_notifications_[i].type == acc_notification.type) {
+      return;
+    }
+  }
+  pending_notifications_.push_back(acc_notification);
+
+  if (!ack_pending_ && method_factory_.empty()) {
+    // When no accessibility notifications are in-flight post a task to send
+    // the notifications to the browser. We use PostTask so that we can queue
+    // up additional notifications.
+    MessageLoop::current()->PostTask(
+        FROM_HERE,
+        method_factory_.NewRunnableMethod(
+            &RendererAccessibility::SendPendingAccessibilityNotifications));
+  }
+}
+
+void RendererAccessibility::SendPendingAccessibilityNotifications() {
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;

[David Tseng, 2011/09/27 21:26:13]

DCHECK?

+
+  if (pending_notifications_.empty())
+    return;
+
+  // Send all pending accessibility notifications.
+  std::vector<ViewHostMsg_AccessibilityNotification_Params> notifications;
+  for (size_t i = 0; i < pending_notifications_.size(); i++) {
+    Notification& notification = pending_notifications_[i];
+
+    bool includes_children = ShouldIncludeChildren(notification);
+    WebAccessibilityObject obj = document.accessibilityObjectFromID(
+        notification.id);
+
+    if (!obj.isValid())
+      continue;

[David Tseng, 2011/09/27 21:26:13]

Do we want to place some logging here? Is this ever expected?

[dmazzoni, 2011/09/28 05:28:50]

This does happen, but it's a WebKit bug when it does. One example I found is
where a children changed notification is sent on an object being removed from
the tree, rather than on its parent.

I added a log in debug mode.

+
+    // The browser may not have this object yet, for example if we get a
+    // notification on an object that was recently added, or if we get a
+    // notification on a node before the page has loaded. Work our way
+    // up the parent chain until we find a node the browser has, or until
+    // we reach the root.
+    int root_id = document.accessibilityObject().axID();
+    while (browser_id_map_.find(obj.axID()) == browser_id_map_.end() &&
+           obj.axID() != root_id) {
+      obj = obj.parentObject();
+      includes_children = true;
+      if (notification.type ==
+          WebKit::WebAccessibilityNotificationChildrenChanged) {
+        notification.id = obj.axID();
+      }
+    }
+
+    // Another potential problem is that this notification may be on an
+    // object that is detached from the tree. Determine if this node is not a
+    // child of its parent, and if so move the notification to the parent.
+    // TODO(dmazzoni): see if this can be removed after
+    // https://bugs.webkit.org/show_bug.cgi?id=68466 is fixed.
+    if (obj.axID() != root_id) {
+      WebAccessibilityObject parent = obj.parentObject();
+      while (!parent.isNull() && parent.accessibilityIsIgnored())
+        parent = parent.parentObject();
+      if (parent.isNull()) {
+        NOTREACHED();
+      }
+      bool is_child_of_parent = false;
+      for (unsigned int i = 0; i < parent.childCount(); i++) {

[David Tseng, 2011/09/27 21:26:13]

++i

+        if (parent.childAt(i).equals(obj)) {
+          is_child_of_parent = true;
+          break;
+        }
+      }
+      if (!is_child_of_parent) {
+        obj = parent;
+        notification.id = obj.axID();
+        includes_children = true;
+      }
+    }
+
+    ViewHostMsg_AccessibilityNotification_Params param;
+    WebAccessibilityNotificationToViewHostMsg(
+        notification.type, &param.notification_type);
+    param.id = notification.id;
+    param.includes_children = includes_children;
+    param.acc_tree = WebAccessibility(obj, includes_children);
+    if (obj.axID() == root_id) {
+      DCHECK_EQ(param.acc_tree.role, WebAccessibility::ROLE_WEB_AREA);
+      param.acc_tree.role = WebAccessibility::ROLE_ROOT_WEB_AREA;
+    }
+    notifications.push_back(param);
+
+    if (includes_children)
+      UpdateBrowserTree(param.acc_tree);
+
+#ifndef NDEBUG
+    if (logging_) {
+      LOG(INFO) << "Accessibility update: "
+                << param.acc_tree.DebugString(true,
+                                              routing_id(),
+                                              param.notification_type);
+    }
+#endif
+  }
+  pending_notifications_.clear();
+  Send(new ViewHostMsg_AccessibilityNotifications(routing_id(), notifications));
+  ack_pending_ = true;
+}
+
+void RendererAccessibility::UpdateBrowserTree(
+    const webkit_glue::WebAccessibility& renderer_node) {
+  BrowserTreeNode* browser_node = NULL;
+  base::hash_map<int32, BrowserTreeNode*>::iterator iter =
+      browser_id_map_.find(renderer_node.id);
+  if (iter != browser_id_map_.end()) {
+    browser_node = iter->second;
+    ClearBrowserTree(browser_node);
+  } else {
+    DCHECK_EQ(renderer_node.role, WebAccessibility::ROLE_ROOT_WEB_AREA);
+    if (browser_root_) {
+      ClearBrowserTree(browser_root_);
+      browser_id_map_.erase(browser_root_->id);

[David Tseng, 2011/09/27 21:26:13]

optional: you could do this within ClearBrowserTree if you also deleted the
parameter node.

[dmazzoni, 2011/09/28 05:28:50]

I don't always want to delete the parameter node; in the above case I just want
to clear it.

+      delete browser_root_;
+    }
+    browser_root_ = new BrowserTreeNode;
+    browser_node = browser_root_;
+    browser_node->id = renderer_node.id;
+    browser_id_map_[browser_node->id] = browser_node;
+  }
+  browser_node->children.reserve(renderer_node.children.size());
+  for (size_t i = 0; i < renderer_node.children.size(); i++) {

[David Tseng, 2011/09/27 21:26:13]

++i

+    BrowserTreeNode* browser_child_node = new BrowserTreeNode;
+    browser_child_node->id = renderer_node.children[i].id;
+    browser_id_map_[browser_child_node->id] = browser_child_node;
+    browser_node->children.push_back(browser_child_node);
+    UpdateBrowserTree(renderer_node.children[i]);
+  }
+}
+
+void RendererAccessibility::ClearBrowserTree(BrowserTreeNode* browser_node) {
+  for (size_t i = 0; i < browser_node->children.size(); i++) {

[David Tseng, 2011/09/27 21:26:13]

++i

+    browser_id_map_.erase(browser_node->children[i]->id);
+    ClearBrowserTree(browser_node->children[i]);
+    delete browser_node->children[i];
+  }
+  browser_node->children.clear();
+}
+
+void RendererAccessibility::OnAccessibilityDoDefaultAction(int acc_obj_id) {
+  if (!WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;

[David Tseng, 2011/09/27 21:26:13]

DCHECK?

+
+  WebAccessibilityObject obj = document.accessibilityObjectFromID(acc_obj_id);
+  if (!obj.isValid())
+    return;

[David Tseng, 2011/09/27 21:26:13]

DCHECK? (out of sync renderer <-> browser).

[dmazzoni, 2011/09/28 05:28:50]

I added logging instead; I think this can happen legitimately during a race
condition.

+
+  obj.performDefaultAction();
+}
+
+void RendererAccessibility::OnAccessibilityNotificationsAck() {
+  DCHECK(ack_pending_);
+  ack_pending_ = false;
+  SendPendingAccessibilityNotifications();
+}
+
+void RendererAccessibility::OnEnableAccessibility() {
+  if (WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  WebAccessibilityObject::enableAccessibility();
+
+  if (render_view()->webview()) {

[David Tseng, 2011/09/27 21:26:13]

GetMainDocument().isNull()?

[dmazzoni, 2011/09/28 05:28:50]

Done.

+    // It's possible that the webview has already loaded a webpage without
+    // accessibility being enabled. Initialize the browser's cached
+    // accessibility tree by sending it a 'load complete' notification.
+    PostAccessibilityNotification(
+        render_view()->webview()->accessibilityObject(),

[David Tseng, 2011/09/27 21:26:13]

GetMainDocument().accessibilityObject()?

[dmazzoni, 2011/09/28 05:28:50]

Done.

+        WebKit::WebAccessibilityNotificationLoadComplete);
+    sent_load_complete_ = true;
+  }
+}
+
+void RendererAccessibility::OnSetAccessibilityFocus(int acc_obj_id) {
+  if (!WebAccessibilityObject::accessibilityEnabled())
+    return;
+
+  const WebDocument& document = GetMainDocument();
+  if (document.isNull())
+    return;
+
+  WebAccessibilityObject obj = document.accessibilityObjectFromID(acc_obj_id);
+  WebAccessibilityObject root = document.accessibilityObject();
+  if (!obj.isValid() || !root.isValid())
+    return;
+
+  // By convention, calling SetFocus on the root of the tree should clear the
+  // current focus. Otherwise set the focus to the new node.
+  if (acc_obj_id == root.axID())
+    render_view()->webview()->clearFocusedNode();
+  else
+    obj.setFocused(true);
+}
+
+bool RendererAccessibility::ShouldIncludeChildren(
+    const RendererAccessibility::Notification& notification) {
+  WebKit::WebAccessibilityNotification type = notification.type;
+  if (type == WebKit::WebAccessibilityNotificationChildrenChanged ||
+      type == WebKit::WebAccessibilityNotificationLoadComplete ||
+      type == WebKit::WebAccessibilityNotificationLiveRegionChanged) {
+    return true;
+  }
+  return false;
+}
+
+WebDocument RendererAccessibility::GetMainDocument() {
+  WebView* view = render_view()->webview();
+  WebFrame* main_frame = view ? view->mainFrame() : NULL;
+
+  if (main_frame)
+    return main_frame->document();
+  else
+    return WebDocument();
+}