Expose an accessible relation between the main window and active alert.

ui/views/accessibility/native_view_accessibility_win.cc

Index: ui/views/accessibility/native_view_accessibility_win.cc
diff --git a/ui/views/accessibility/native_view_accessibility_win.cc b/ui/views/accessibility/native_view_accessibility_win.cc
index 10c17ff3d6d636f153644cf34b0ece332e4d2a6a..f0a1ae510e15d2c203b250fd899a8830ad6185dd 100644
--- a/ui/views/accessibility/native_view_accessibility_win.cc
+++ b/ui/views/accessibility/native_view_accessibility_win.cc
@@ -189,6 +189,7 @@ void AccessibleWebViewRegistry::QueryIAccessible2Interface(View* web_view) {
 long NativeViewAccessibilityWin::next_unique_id_ = 1;
 int NativeViewAccessibilityWin::view_storage_ids_[kMaxViewStorageIds] = {0};
 int NativeViewAccessibilityWin::next_view_storage_id_index_ = 0;
+std::vector<int> NativeViewAccessibilityWin::alert_target_view_storage_ids_;
 
 // static
 NativeViewAccessibility* NativeViewAccessibility::Create(View* view) {
@@ -210,6 +211,7 @@ NativeViewAccessibilityWin::NativeViewAccessibilityWin()
 }
 
 NativeViewAccessibilityWin::~NativeViewAccessibilityWin() {
+  RemoveAlertTarget();
 }
 
 void NativeViewAccessibilityWin::NotifyAccessibilityEvent(
@@ -236,6 +238,10 @@ void NativeViewAccessibilityWin::NotifyAccessibilityEvent(
   ::NotifyWinEvent(MSAAEvent(event_type), hwnd, OBJID_CLIENT, child_id);
   next_view_storage_id_index_ =
       (next_view_storage_id_index_ + 1) % kMaxViewStorageIds;
+
+  // Keep track of views that are a target of an alert event.
+  if (event_type == ui::AX_EVENT_ALERT)
+    AddAlertTarget();
 }
 
 gfx::NativeViewAccessible NativeViewAccessibilityWin::GetNativeObject() {
@@ -865,6 +871,39 @@ STDMETHODIMP NativeViewAccessibilityWin::get_windowHandle(HWND* window_handle) {
   return *window_handle ? S_OK : S_FALSE;
 }
 
+STDMETHODIMP NativeViewAccessibilityWin::get_relationTargetsOfType(
+    BSTR type_bstr,
+    long max_targets,
+    IUnknown ***targets,
+    long *n_targets) {
+  if (!view_)
+    return E_FAIL;
+
+  if (!targets || !n_targets || max_targets <= 0)
+    return E_INVALIDARG;
+
+  *n_targets = 0;
+  base::string16 type(type_bstr);
+  if (type != L"alerts" || view_->parent())
+    return S_OK;
+
+  ViewStorage* view_storage = ViewStorage::GetInstance();
+  for (size_t i = 0; i < alert_target_view_storage_ids_.size(); ++i) {
+    int view_storage_id = alert_target_view_storage_ids_[i];
+    View* view = view_storage->RetrieveView(view_storage_id);
+    if (!view || !view_->Contains(view))
+      continue;
+
+    (*targets)[*n_targets] = view->GetNativeViewAccessible();

[aboxhall, 2014/05/07 15:26:30]

This will put targets in *targets in chronological order, right? Is that what we
want (as opposed to reverse chronological order)? Alternatively, if it is
chronological order we want, do we want to start at max(0,
alert_target_view_storage_ids_.size() - max_targets) to avoid missing the most
recent (and thus presumably most relevant) alerts in favour of older alerts?

[dmazzoni, 2014/05/07 15:31:41]

I hadn't thought about the order. I'm not even sure what we want, I think it may
be more up to the screen reader to decide what to do. I think NV Access was
thinking of announcing something like "There are <n> alerts" if there's more
than 1.

I can see an argument for window order / view order rather than chronological,
too.

I'd prefer to keep the code simple until we know what we want.

+    (*targets)[*n_targets]->AddRef();
+    ++(*n_targets);
+
+    if (*n_targets == max_targets)
+      break;
+  }
+  return S_OK;
+}
+
 //
 // IAccessibleText
 //
@@ -1071,11 +1110,12 @@ STDMETHODIMP NativeViewAccessibilityWin::QueryService(
   if (!view_)
     return E_FAIL;
 
-  if (riid == IID_IAccessible2)
+  if (riid == IID_IAccessible2 || riid == IID_IAccessible2_2)
     AccessibleWebViewRegistry::GetInstance()->EnableIAccessible2Support();
 
   if (guidService == IID_IAccessible ||
       guidService == IID_IAccessible2 ||
+      guidService == IID_IAccessible2_2 ||
       guidService == IID_IAccessibleText)  {
     return QueryInterface(riid, object);
   }
@@ -1412,4 +1452,32 @@ void NativeViewAccessibilityWin::PopulateChildWidgetVector(
   }
 }
 
+void NativeViewAccessibilityWin::AddAlertTarget() {
+  ViewStorage* view_storage = ViewStorage::GetInstance();
+  for (size_t i = 0; i < alert_target_view_storage_ids_.size(); ++i) {
+    int view_storage_id = alert_target_view_storage_ids_[i];
+    View* view = view_storage->RetrieveView(view_storage_id);
+    if (view == view_)

[aboxhall, 2014/05/07 15:26:30]

Similarly, do we want to bump up this view in the alert_target_view_storage_ids_
list if this method gets called again?

+      return;
+  }
+  int view_storage_id = view_storage->CreateStorageID();
+  view_storage->StoreView(view_storage_id, view_);
+  alert_target_view_storage_ids_.push_back(view_storage_id);
+}
+
+void NativeViewAccessibilityWin::RemoveAlertTarget() {
+  ViewStorage* view_storage = ViewStorage::GetInstance();
+  size_t i = 0;
+  while (i < alert_target_view_storage_ids_.size()) {
+    int view_storage_id = alert_target_view_storage_ids_[i];
+    View* view = view_storage->RetrieveView(view_storage_id);
+    if (view == NULL || view == view_) {
+      alert_target_view_storage_ids_.erase(
+          alert_target_view_storage_ids_.begin() + i);

[aboxhall, 2014/05/07 15:26:30]

Why don't we want to increment i in this case?

[dmazzoni, 2014/05/07 15:31:41]

We're erasing the ith element, which should shift everything over and then we
should check the new ith element (which used to be the i+1th element).

Please check my logic. Is there a more foolproof way to do this? I guess if
order doesn't matter I could use a set...

+    } else {
+      ++i;
+    }
+  }
+}
+
 }  // namespace views