Improve omnibox accessibility on Windows.

views/widget/native_widget_win.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 "views/widget/native_widget_win.h"
 
 #include <dwmapi.h>
 #include <shellapi.h>
 
 #include <algorithm>
@@ skipping 362 matching lines @@
 NativeWidgetWin::NativeWidgetWin(internal::NativeWidgetDelegate* delegate)
     : delegate_(delegate),
       ALLOW_THIS_IN_INITIALIZER_LIST(close_widget_factory_(this)),
       active_mouse_tracking_flags_(0),
       use_layered_buffer_(false),
       layered_alpha_(255),
       ALLOW_THIS_IN_INITIALIZER_LIST(paint_layered_window_factory_(this)),
       ownership_(Widget::InitParams::NATIVE_WIDGET_OWNS_WIDGET),
       can_update_layered_window_(true),
       restore_focus_when_enabled_(false),
-      accessibility_view_events_index_(-1),
-      accessibility_view_events_(kMaxAccessibilityViewEvents),
       previous_cursor_(NULL),
       fullscreen_(false),
       force_hidden_count_(0),
       lock_updates_count_(0),
       saved_window_style_(0),
       ignore_window_pos_changes_(false),
       ALLOW_THIS_IN_INITIALIZER_LIST(ignore_pos_changes_factory_(this)),
       last_monitor_(NULL),
       is_right_mouse_pressed_on_caption_(false),
       restored_enabled_(false),
@@ skipping 45 matching lines @@
   // We need to explicitly activate the window if we've been shown with a state
   // that should activate, because if we're opened from a desktop shortcut while
   // an existing window is already running it doesn't seem to be enough to use
   // one of these flags to activate the window.
   if (show_state == SW_SHOWNORMAL || show_state == SW_SHOWMAXIMIZED)
     Activate();
 
   SetInitialFocus();
 }
 
-View* NativeWidgetWin::GetAccessibilityViewEventAt(int id) {
-  // Convert from MSAA child id.
-  id = -(id + 1);
-  DCHECK(id >= 0 && id < kMaxAccessibilityViewEvents);
-  return accessibility_view_events_[id];
-}
-
-int NativeWidgetWin::AddAccessibilityViewEvent(View* view) {
-  accessibility_view_events_index_ =
-      (accessibility_view_events_index_ + 1) % kMaxAccessibilityViewEvents;
-  accessibility_view_events_[accessibility_view_events_index_] = view;
-
-  // Convert to MSAA child id.
-  return -(accessibility_view_events_index_ + 1);
-}
-
-void NativeWidgetWin::ClearAccessibilityViewEvent(View* view) {
-  for (std::vector<View*>::iterator it = accessibility_view_events_.begin();
-      it != accessibility_view_events_.end();
-      ++it) {
-    if (*it == view)
-      *it = NULL;
-  }
+View* NativeWidgetWin::GetAccessibilityViewFromChildId(long child_id) {
+  long unique_id = -child_id;

[sky, 2011/10/25 20:08:45]

Why do you negate this?

[dmazzoni, 2011/10/26 16:46:13]

It's explained in SendNativeAccessibilityEvent; I added a comment pointing
there.

+  base::hash_map<long, View*>::iterator iter =
+      accessibility_id_view_map_.find(unique_id);
+  if (iter != accessibility_id_view_map_.end())

[sky, 2011/10/25 20:08:45]

nit: convert to a return statement.

+    return iter->second;
+  else
+    return NULL;
 }
 
 void NativeWidgetWin::PushForceHidden() {
   if (force_hidden_count_++ == 0)
     Hide();
 }
 
 void NativeWidgetWin::PopForceHidden() {
   if (--force_hidden_count_ <= 0) {
     force_hidden_count_ = 0;
@@ skipping 98 matching lines @@
 }
 
 void NativeWidgetWin::CalculateOffsetToAncestorWithLayer(
     gfx::Point* offset,
     ui::Layer** layer_parent) {
 }
 
 void NativeWidgetWin::ReorderLayers() {
 }
 
 void NativeWidgetWin::ViewRemoved(View* view) {

[sky, 2011/10/25 20:08:45]

Don't you need to do this for all descendants of view too?

[dmazzoni, 2011/10/26 16:46:13]

Doesn't apply anymore now that we search.

   if (drop_target_.get())
     drop_target_->ResetTargetViewIfEquals(view);
 
-  ClearAccessibilityViewEvent(view);
+  // Remove this view from the map from accessibility unique IDs to views.
+  IAccessible* accessible = view->GetNativeViewAccessible();
+  IAccessible2* accessible2 = NULL;
+  HRESULT hr = accessible->QueryInterface(

[sky, 2011/10/25 20:08:45]

How expensive is this? Would it be better to maintain the inverse mapping
(view->id)?

[dmazzoni, 2011/10/26 16:46:13]

It couldn't be that expensive - it's called thousands of times per second when
accessibility is enabled.

Maintaining view->id would be just as ugly as maintaining id->view, we'd have to
update it every time the view hierarchy changed.

Since I changed it to search the view hierarchy, QueryInterface will now only be
called once per accessibility notification (these are rare, one or two per user
event like a click), and additional calls will only happen if assistive
technology is running and triggers GetViewByAccessibleId.

+      IID_IAccessible2, reinterpret_cast<void**>(&accessible2));
+  if (hr == S_OK) {
+    long unique_id;
+    hr = accessible2->get_uniqueID(&unique_id);
+    if (hr == S_OK) {

[sky, 2011/10/25 20:08:45]

nit: no {}

+      accessibility_id_view_map_.erase(unique_id);
+    }
+  }
 }
 
 void NativeWidgetWin::SetNativeWindowProperty(const char* name, void* value) {
   // Remove the existing property (if any).
   for (ViewProps::iterator i = props_.begin(); i != props_.end(); ++i) {
     if ((*i)->Key() == name) {
       props_.erase(i);
       break;
     }
   }
@@ skipping 10 matching lines @@
   return tooltip_manager_.get();
 }
 
 bool NativeWidgetWin::IsScreenReaderActive() const {
   return screen_reader_active_;
 }
 
 void NativeWidgetWin::SendNativeAccessibilityEvent(
     View* view,
     ui::AccessibilityTypes::Event event_type) {
-  // Now call the Windows-specific method to notify MSAA clients of this
-  // event.  The widget gives us a temporary unique child ID to associate
-  // with this view so that clients can call get_accChild in
-  // NativeViewAccessibilityWin to retrieve the IAccessible associated
-  // with this view.
-  int child_id = AddAccessibilityViewEvent(view);
-  ::NotifyWinEvent(NativeViewAccessibilityWin::MSAAEvent(event_type),
-                   GetNativeView(), OBJID_CLIENT, child_id);
+  DWORD native_event = NativeViewAccessibilityWin::MSAAEvent(event_type);
+  gfx::NativeView native_view = this->GetNativeView();
+
+  // Get the unique ID from the view's IAccessible2 interface.
+  IAccessible* accessible = view->GetNativeViewAccessible();
+  IAccessible2* accessible2 = NULL;
+  HRESULT hr = accessible->QueryInterface(
+      IID_IAccessible2, reinterpret_cast<void**>(&accessible2));
+  if (hr != S_OK) {
+    // If this is reached, you're probably trying to fire a notification on a
+    // views::NativeViewHost that has only a default IAccessible. You have to
+    // either call ::NotifyWinEvent directly, or override
+    // GetNativeViewAccessible for that view.
+    NOTREACHED();
+    return;
+  }
+  long unique_id;
+  hr = accessible2->get_uniqueID(&unique_id);
+  DCHECK_EQ(hr, S_OK);
+  if (!accessibility_id_view_map_[unique_id])

[sky, 2011/10/25 20:08:45]

Can you reset the map all the time? Or maybe DCHECK that NULL or == view.

+    accessibility_id_view_map_[unique_id] = view;
+
+  // Send the negation of the unique id as the child id parameter to
+  // NotifyWinEvent. The client will call get_accChild on the top-level
+  // NativeViewAccessibilityWin object, where positive child ids are
+  // interpreted as 1-based child indices, and negative child ids are
+  // interpreted as unique ids.
+  ::NotifyWinEvent(native_event, native_view, OBJID_CLIENT, -unique_id);
 }
 
 void NativeWidgetWin::SetMouseCapture() {
   DCHECK(!HasMouseCapture());
   SetCapture(hwnd());
 }
 
 void NativeWidgetWin::ReleaseMouseCapture() {
   ReleaseCapture();
 }
@@ skipping 1981 matching lines @@
   return (GetKeyState(VK_LBUTTON) & 0x80) ||
     (GetKeyState(VK_RBUTTON) & 0x80) ||
     (GetKeyState(VK_MBUTTON) & 0x80) ||
     (GetKeyState(VK_XBUTTON1) & 0x80) ||
     (GetKeyState(VK_XBUTTON2) & 0x80);
 }
 
 }  // namespace internal
 
 }  // namespace views