Reimplement web content accessibility by caching in browser process

chrome/browser/browser_accessibility_manager.h

Index: chrome/browser/browser_accessibility_manager.h
===================================================================
--- chrome/browser/browser_accessibility_manager.h	(revision 46908)
+++ chrome/browser/browser_accessibility_manager.h	(working copy)
@@ -1,104 +1,102 @@
-// 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.
 
 #ifndef CHROME_BROWSER_BROWSER_ACCESSIBILITY_MANAGER_H_
 #define CHROME_BROWSER_BROWSER_ACCESSIBILITY_MANAGER_H_
 
+#include <atlbase.h>
+#include <atlcom.h>
+#include <oleacc.h>
+
 #include <map>
 
-#include "base/singleton.h"
-#include "chrome/common/notification_registrar.h"
+#include "base/hash_tables.h"
+#include "base/scoped_comptr_win.h"
+#include "base/scoped_ptr.h"
 #include "webkit/glue/webaccessibility.h"
 
 class BrowserAccessibility;
 class RenderProcessHost;
 class RenderWidgetHost;
 
-using webkit_glue::WebAccessibility;
-
-////////////////////////////////////////////////////////////////////////////////
-//
-// BrowserAccessibilityManager
-//
-// Used to manage instance creation and memory handling for browser side
-// accessibility. A singleton class. It implements NotificationObserver to
-// ensure that a termination of a renderer process gets propagated to the
-// active BrowserAccessibility instances calling into it. Each such instance
-// will upon such an event be set to an inactive state, failing calls from the
-// assistive technology gracefully.
-////////////////////////////////////////////////////////////////////////////////
-class BrowserAccessibilityManager : public NotificationObserver {
+class BrowserAccessibilityFactory {
  public:
-  // Gets the singleton BrowserAccessibilityManager object. The first time this
-  // method is called, a CacheManagerHost object is constructed and returned.
-  // Subsequent calls will return the same object.
-  static BrowserAccessibilityManager* GetInstance();
+  virtual ~BrowserAccessibilityFactory() {}
 
-  // Creates an instance of BrowserAccessibility, initializes it and sets the
-  // |acc_obj_id|, which is used for IPC communication, and |instance_id|,
-  // which is used to identify the mapping between accessibility instance and
-  // RenderProcess.
-  STDMETHODIMP CreateAccessibilityInstance(REFIID iid,
-                                           int acc_obj_id,
-                                           int routing_id,
-                                           int process_id,
-                                           HWND parent_hwnd,
-                                           void** interface_ptr);
+  // Create an instance of BrowserAccessibility and return a new
+  // reference to it.
+  virtual BrowserAccessibility* Create();
+};
 
-  // Composes and sends a message for requesting needed accessibility
-  // information.
-  bool RequestAccessibilityInfo(WebAccessibility::InParams* in,
-                                int routing_id,
-                                int process_id);
+// Manages a tree of BrowserAccessibility objects.
+class BrowserAccessibilityManager {
+ public:
+  BrowserAccessibilityManager(
+      HWND parent_hwnd,
+      const webkit_glue::WebAccessibility& src,
+      BrowserAccessibilityFactory* factory = new BrowserAccessibilityFactory());
 
-  // Notifies assistive technology that renderer focus changed, through the
-  // platform-specific channels.
-  bool ChangeAccessibilityFocus(int acc_obj_id, int process_id, int routing_id);
+  virtual ~BrowserAccessibilityManager();
 
-  // Notifies assistive technology that an object's state changed, through the
-  // platform-specific channels.
-  bool OnAccessibilityObjectStateChange(int acc_obj_id,
-                                        int process_id,
-                                        int routing_id);
+  // Return a pointer to the root of the tree, does not make a new reference.
+  BrowserAccessibility* GetRoot();
 
-  // Wrapper function, for cleaner code.
-  const WebAccessibility::OutParams& response();
+  // Return a pointer to the object corresponding to the given child_id,
+  // does not make a new reference.
+  BrowserAccessibility* GetFromChildID(LONG child_id);
 
-  // NotificationObserver implementation.
-  virtual void Observe(NotificationType type,
-                       const NotificationSource& source,
-                       const NotificationDetails& details);
+  // Get a the default IAccessible for the parent window, does not make a
+  // new reference.
+  IAccessible* GetParentWindowIAccessible();
 
- protected:
-  // This class is a singleton.  Do not instantiate directly.
-  BrowserAccessibilityManager();
-  friend struct DefaultSingletonTraits<BrowserAccessibilityManager>;
+  // Get the parent window.
+  HWND GetParentHWND();
 
-  ~BrowserAccessibilityManager();
+  // Return the object that has focus, if it's a descandant of the
+  // given root (inclusive). Does not make a new reference.
+  BrowserAccessibility* GetFocus(BrowserAccessibility* root);
 
+  // Called when the renderer process has notified us of a focus or state
+  // change. Send a notification to MSAA clients of the change.
+  void OnAccessibilityFocusChange(int acc_obj_id);
+  void OnAccessibilityObjectStateChange(int acc_obj_id);
+
  private:
-  // Retrieves the BrowserAccessibility instance connected to the
-  // RenderProcessHost identified by the process/routing id pair.
-  BrowserAccessibility* GetBrowserAccessibility(int process_id, int routing_id);
+  // Recursively build a tree of BrowserAccessibility objects from
+  // the WebAccessibility tree received from the renderer process.
+  BrowserAccessibility* CreateAccessibilityTree(
+      BrowserAccessibility* parent,
+      const webkit_glue::WebAccessibility& src,
+      int index_in_parent);
 
-  // Multi-map from process id (key) to active BrowserAccessibility instances
-  // for that RenderProcessHost.
-  typedef std::multimap<int, BrowserAccessibility*> RenderProcessHostMap;
-  typedef std::pair<int, BrowserAccessibility*> MapEntry;
+  // The parent window.
+  HWND parent_hwnd_;
 
-  NotificationRegistrar registrar_;
+  // Factory to create BrowserAccessibility objects (for dependency injection).
+  scoped_ptr<BrowserAccessibilityFactory> factory_;
 
-  // Mapping to track which RenderProcessHosts ids are active. If a
-  // RenderProcessHost is found to be terminated, its id (key) should be removed
-  // from this mapping, and the connected BrowserAccessibility ids/instances
-  // invalidated.
-  RenderProcessHostMap render_process_host_map_;
+  // A default IAccessible instance for the parent window.
+  ScopedComPtr<IAccessible> window_iaccessible_;
 
-  // Structure passed by reference to hold response parameters from the
-  // renderer.
-  WebAccessibility::OutParams out_params_;
+  // The root of the tree of IAccessible objects and the element that
+  // currently has focus, if any.
+  BrowserAccessibility* root_;
+  BrowserAccessibility* focus_;
 
+  // A mapping from the IDs of objects in the renderer, to the child IDs
+  // we use internally here.
+  base::hash_map<int, LONG> renderer_id_to_child_id_map_;
+
+  // A mapping from child IDs to BrowserAccessibility objects.
+  base::hash_map<LONG, BrowserAccessibility*> child_id_map_;
+
+  // The next child ID to use; static so that they're global to the process.
+  // Screen readers cache these IDs to see if they've seen the same object
+  // before so we should avoid reusing them within the same project.
+  static LONG next_child_id_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityManager);
 };
+
 #endif  // CHROME_BROWSER_BROWSER_ACCESSIBILITY_MANAGER_H_