Reimplement web content accessibility by caching in browser process

chrome/browser/browser_accessibility_manager.cc

Index: chrome/browser/browser_accessibility_manager.cc
===================================================================
--- chrome/browser/browser_accessibility_manager.cc	(revision 46908)
+++ chrome/browser/browser_accessibility_manager.cc	(working copy)
@@ -1,4 +1,4 @@
-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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.
 
@@ -8,161 +8,130 @@
 #include "chrome/browser/browser_accessibility.h"
 #include "chrome/browser/renderer_host/render_process_host.h"
 #include "chrome/browser/renderer_host/render_view_host.h"
-#include "chrome/common/notification_service.h"
 #include "chrome/common/render_messages.h"
 
 using webkit_glue::WebAccessibility;
 
-// The time in ms after which we give up and return an error when processing an
-// accessibility message and no response has been received from the renderer.
-static const int kAccessibilityMessageTimeOut = 10000;
+// Factory method to create an instance of BrowserAccessibility
+BrowserAccessibility* BrowserAccessibilityFactory::Create() {
+  CComObject<BrowserAccessibility>* instance;
+  HRESULT hr = CComObject<BrowserAccessibility>::CreateInstance(&instance);
+  DCHECK(SUCCEEDED(hr));
+  return instance->NewReference();
+}
 
 // static
-BrowserAccessibilityManager* BrowserAccessibilityManager::GetInstance() {
-  return Singleton<BrowserAccessibilityManager>::get();
-}
+// Start child IDs at -1 and decrement each time, because clients use
+// child IDs of 1, 2, 3, ... to access the children of an object by
+// index, so we use negative IDs to clearly distinguish between indices
+// and unique IDs.
+LONG BrowserAccessibilityManager::next_child_id_ = -1;
 
-BrowserAccessibilityManager::BrowserAccessibilityManager() {
-  registrar_.Add(this, NotificationType::RENDERER_PROCESS_TERMINATED,
-                 NotificationService::AllSources());
+BrowserAccessibilityManager::BrowserAccessibilityManager(
+    HWND parent_hwnd,
+    const webkit_glue::WebAccessibility& src,
+    BrowserAccessibilityFactory* factory)
+    : parent_hwnd_(parent_hwnd),
+      factory_(factory) {
+  HRESULT hr = ::CreateStdAccessibleObject(
+      parent_hwnd_, OBJID_WINDOW, IID_IAccessible,
+      reinterpret_cast<void **>(&window_iaccessible_));
+  DCHECK(SUCCEEDED(hr));
+  root_ = CreateAccessibilityTree(NULL, src, 0);
+  if (!focus_)
+    focus_ = root_;
 }
 
 BrowserAccessibilityManager::~BrowserAccessibilityManager() {
-  // Clear hashmap.
-  render_process_host_map_.clear();
+  // Clients could still hold references to some nodes of the tree, so
+  // calling Inactivate will make sure that as many nodes as possible are
+  // released now, and remaining nodes are marked as inactive so that
+  // calls to any methods on them will return E_FAIL;
+  root_->InactivateTree();
+  root_->Release();
 }
 
-STDMETHODIMP BrowserAccessibilityManager::CreateAccessibilityInstance(
-    REFIID iid, int acc_obj_id, int routing_id, int process_id,
-    HWND parent_hwnd, void** interface_ptr) {
-  if (IID_IUnknown == iid || IID_IDispatch == iid || IID_IAccessible == iid) {
-    CComObject<BrowserAccessibility>* instance = NULL;
-
-    HRESULT hr = CComObject<BrowserAccessibility>::CreateInstance(&instance);
-    DCHECK(SUCCEEDED(hr));
-
-    if (!instance)
-      return E_FAIL;
-
-    ScopedComPtr<IAccessible> accessibility_instance(instance);
-
-    // Set class member variables.
-    instance->Initialize(acc_obj_id, routing_id, process_id, parent_hwnd);
-
-    // Retrieve the RenderViewHost connected to this request.
-    RenderViewHost* rvh = RenderViewHost::FromID(process_id, routing_id);
-
-    // Update cache with RenderProcessHost/BrowserAccessibility pair.
-    if (rvh && rvh->process()) {
-      render_process_host_map_.insert(MapEntry(rvh->process()->id(), instance));
-    } else {
-      // No RenderProcess active for this instance.
-      return E_FAIL;
-    }
-
-    // All is well, assign the temp instance to the output pointer.
-    *interface_ptr = accessibility_instance.Detach();
-    return S_OK;
-  }
-  // No supported interface found, return error.
-  *interface_ptr = NULL;
-  return E_NOINTERFACE;
+BrowserAccessibility* BrowserAccessibilityManager::GetRoot() {
+  return root_;
 }
 
-bool BrowserAccessibilityManager::RequestAccessibilityInfo(
-    WebAccessibility::InParams* in, int routing_id, int process_id) {
-  // Create and populate IPC message structure, for retrieval of accessibility
-  // information from the renderer.
-  WebAccessibility::InParams in_params;
-  in_params.object_id = in->object_id;
-  in_params.function_id = in->function_id;
-  in_params.child_id = in->child_id;
-  in_params.input_long1 = in->input_long1;
-  in_params.input_long2 = in->input_long2;
-
-  // Retrieve the RenderViewHost connected to this request.
-  RenderViewHost* rvh = RenderViewHost::FromID(process_id, routing_id);
-
-  // Send accessibility information retrieval message to the renderer.
-  bool success = false;
-  if (rvh && rvh->process() && rvh->process()->HasConnection()) {
-    IPC::SyncMessage* msg =
-        new ViewMsg_GetAccessibilityInfo(routing_id, in_params, &out_params_);
-    // Necessary for the send to keep the UI responsive.
-    msg->EnableMessagePumping();
-    success = rvh->process()->SendWithTimeout(msg,
-        kAccessibilityMessageTimeOut);
+BrowserAccessibility* BrowserAccessibilityManager::GetFromChildID(
+    LONG child_id) {
+  base::hash_map<LONG, BrowserAccessibility*>::iterator iter =
+      child_id_map_.find(child_id);
+  if (iter != child_id_map_.end()) {
+    return iter->second;
+  } else {
+    return NULL;
   }
-  return success;
 }
 
-bool BrowserAccessibilityManager::ChangeAccessibilityFocus(int acc_obj_id,
-                                                           int process_id,
-                                                           int routing_id) {
-  BrowserAccessibility* browser_acc =
-      GetBrowserAccessibility(process_id, routing_id);
-  if (browser_acc) {
-    // Notify Access Technology that there was a change in keyboard focus.
-    ::NotifyWinEvent(EVENT_OBJECT_FOCUS, browser_acc->parent_hwnd(),
-                     OBJID_CLIENT, static_cast<LONG>(acc_obj_id));
-    return true;
-  }
-  return false;
+IAccessible* BrowserAccessibilityManager::GetParentWindowIAccessible() {
+  return window_iaccessible_;
 }
 
-bool BrowserAccessibilityManager::OnAccessibilityObjectStateChange(
-    int acc_obj_id, int process_id, int routing_id) {
-  BrowserAccessibility* browser_acc =
-      GetBrowserAccessibility(process_id, routing_id);
-  if (browser_acc) {
-    // Notify Access Technology that there was a change in state.
-    ::NotifyWinEvent(EVENT_OBJECT_STATECHANGE, browser_acc->parent_hwnd(),
-                     OBJID_CLIENT, static_cast<LONG>(acc_obj_id));
-    return true;
-  }
-  return false;
+HWND BrowserAccessibilityManager::GetParentHWND() {
+  return parent_hwnd_;
 }
 
-const WebAccessibility::OutParams& BrowserAccessibilityManager::response() {
-  return out_params_;
+BrowserAccessibility* BrowserAccessibilityManager::GetFocus(
+    BrowserAccessibility* root) {
+  if (focus_ && (!root || focus_->IsDescendantOf(root)))
+    return focus_;
+
+  return NULL;
 }
 
-BrowserAccessibility* BrowserAccessibilityManager::GetBrowserAccessibility(
-    int process_id, int routing_id) {
-  // Retrieve the BrowserAccessibility connected to the requester's id. There
-  // could be multiple BrowserAccessibility connected to the given |process_id|,
-  // but they all have the same parent HWND, so using the first hit is fine.
-  RenderProcessHostMap::iterator it =
-      render_process_host_map_.lower_bound(process_id);
+void BrowserAccessibilityManager::OnAccessibilityFocusChange(int renderer_id) {
+  base::hash_map<int, LONG>::iterator iter =
+      renderer_id_to_child_id_map_.find(renderer_id);
+  if (iter == renderer_id_to_child_id_map_.end())
+    return;
 
-  RenderProcessHostMap::iterator end_of_matching_objects =
-    render_process_host_map_.upper_bound(process_id);
-
-  for (; it != end_of_matching_objects; ++it) {
-    if (it->second && it->second->routing_id() == routing_id)
-      return it->second;
-  }
-  return NULL;
+  LONG child_id = iter->second;
+  base::hash_map<LONG, BrowserAccessibility*>::iterator uniq_iter =
+    child_id_map_.find(child_id);
+  if (uniq_iter != child_id_map_.end())
+    focus_ = uniq_iter->second;
+  ::NotifyWinEvent(EVENT_OBJECT_FOCUS, parent_hwnd_, OBJID_CLIENT, child_id);
 }
 
-void BrowserAccessibilityManager::Observe(NotificationType type,
-                                          const NotificationSource& source,
-                                          const NotificationDetails& details) {
-  DCHECK(type == NotificationType::RENDERER_PROCESS_TERMINATED);
-  RenderProcessHost* rph = Source<RenderProcessHost>(source).ptr();
-  DCHECK(rph);
+void BrowserAccessibilityManager::OnAccessibilityObjectStateChange(
+    int renderer_id) {
+  base::hash_map<int, LONG>::iterator iter =
+      renderer_id_to_child_id_map_.find(renderer_id);
+  if (iter == renderer_id_to_child_id_map_.end())
+    return;
 
-  RenderProcessHostMap::iterator it =
-      render_process_host_map_.lower_bound(rph->id());
+  LONG child_id = iter->second;
+  ::NotifyWinEvent(EVENT_OBJECT_FOCUS, parent_hwnd_, OBJID_CLIENT, child_id);
+}
 
-  RenderProcessHostMap::iterator end_of_matching_objects =
-    render_process_host_map_.upper_bound(rph->id());
+BrowserAccessibility* BrowserAccessibilityManager::CreateAccessibilityTree(
+    BrowserAccessibility* parent,
+    const webkit_glue::WebAccessibility& src,
+    int index_in_parent) {
+  BrowserAccessibility* instance = factory_->Create();
 
-  for (; it != end_of_matching_objects; ++it) {
-    if (it->second) {
-      // Set all matching BrowserAccessibility instances to inactive state.
-      // TODO(klink): Do more active memory cleanup as well.
-      it->second->set_instance_active(false);
-    }
+  // Get the next child ID, and wrap around when we get near the end
+  // of a 32-bit integer range. It's okay to wrap around; we just want
+  // to avoid it as long as possible because clients may cache the ID of
+  // an object for a while to determine if they've seen it before.
+  LONG child_id = next_child_id_;
+  next_child_id_--;
+  if (next_child_id_ == -2000000000)
+    next_child_id_ = -1;
+
+  instance->Initialize(this, parent, child_id, index_in_parent, src);
+  child_id_map_[child_id] = instance;
+  renderer_id_to_child_id_map_[src.id] = child_id;
+  if ((src.state >> WebAccessibility::STATE_FOCUSED) & 1)
+    focus_ = instance;
+  for (int i = 0; i < static_cast<int>(src.children.size()); ++i) {
+    BrowserAccessibility* child = CreateAccessibilityTree(
+        instance, src.children[i], i);
+    instance->AddChild(child);
   }
+
+  return instance;
 }