Implemented IAccessible2 reverse relations.

content/browser/accessibility/browser_accessibility_win.cc

 // Copyright (c) 2012 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 "content/browser/accessibility/browser_accessibility_win.h"
 
 #include <UIAutomationClient.h>
 #include <UIAutomationCoreApi.h>
 
 #include <algorithm>
@@ skipping 3508 matching lines @@
   // attribute. This allows screen readers to read an empty link's destination.
   if (value.empty() && (ia_state() & STATE_SYSTEM_LINKED))
     value = GetString16Attribute(ui::AX_ATTR_URL);
   win_attributes_->value = value;
 
   // Clear any old relationships between this node and other nodes.
   for (size_t i = 0; i < relations_.size(); ++i)
     relations_[i]->Release();
   relations_.clear();
 
-  // Handle title UI element.
-  AddRelations(ui::AX_ATTR_CONTROLS_IDS, IA2_RELATION_CONTROLLER_FOR);
-  AddRelations(ui::AX_ATTR_DESCRIBEDBY_IDS, IA2_RELATION_DESCRIBED_BY);
-  AddRelations(ui::AX_ATTR_FLOWTO_IDS, IA2_RELATION_FLOWS_TO);
-  AddRelations(ui::AX_ATTR_LABELLEDBY_IDS, IA2_RELATION_LABELLED_BY);
+  AddBidirectionalRelations(IA2_RELATION_CONTROLLER_FOR,
+                            IA2_RELATION_CONTROLLED_BY,
+                            ui::AX_ATTR_CONTROLS_IDS);
+  AddBidirectionalRelations(IA2_RELATION_DESCRIBED_BY,
+                            IA2_RELATION_DESCRIPTION_FOR,
+                            ui::AX_ATTR_DESCRIBEDBY_IDS);
+  AddBidirectionalRelations(IA2_RELATION_FLOWS_TO, IA2_RELATION_FLOWS_FROM,
+                            ui::AX_ATTR_FLOWTO_IDS);
+  AddBidirectionalRelations(IA2_RELATION_LABELLED_BY, IA2_RELATION_LABEL_FOR,
+                            ui::AX_ATTR_LABELLEDBY_IDS);
+
+  int member_of_id;
+  if (GetIntAttribute(ui::AX_ATTR_MEMBER_OF_ID, &member_of_id))
+    AddRelation(IA2_RELATION_MEMBER_OF, member_of_id);
 
   UpdateRequiredAttributes();
   // If this is a web area for a presentational iframe, give it a role of
   // something other than DOCUMENT so that the fact that it's a separate doc
   // is not exposed to AT.
   if (IsWebAreaForPresentationalIframe()) {
     win_attributes_->ia_role = ROLE_SYSTEM_GROUPING;
     win_attributes_->ia2_role = ROLE_SYSTEM_GROUPING;
   }
 }
@@ skipping 885 matching lines @@
   }
 
   if (role == ui::AX_ROLE_MENU_LIST_OPTION &&
       parent_role == ui::AX_ROLE_MENU_LIST_POPUP) {
     return true;
   }
 
   return false;
 }
 
-void BrowserAccessibilityWin::AddRelations(
-    ui::AXIntListAttribute src_attr,
-    const base::string16& iaccessiblerelation_type) {
-  if (!HasIntListAttribute(src_attr))
+void BrowserAccessibilityWin::AddRelation(const base::string16& relation_type,
+                                          int target_id) {
+  CComObject<BrowserAccessibilityRelation>* relation;
+  HRESULT hr =
+      CComObject<BrowserAccessibilityRelation>::CreateInstance(&relation);
+  DCHECK(SUCCEEDED(hr));
+  relation->AddRef();
+  relation->Initialize(this, relation_type);
+  relation->AddTarget(target_id);
+  relations_.push_back(relation);
+}
+
+void BrowserAccessibilityWin::AddBidirectionalRelations(
+    const base::string16& relation_type,
+    const base::string16& reverse_relation_type,
+    ui::AXIntListAttribute attribute) {
+  if (!HasIntListAttribute(attribute))
     return;
 
-  const std::vector<int32_t>& ids = GetIntListAttribute(src_attr);
-  for (size_t i = 0; i < ids.size(); ++i) {
+  for (int target_id : GetIntListAttribute(attribute)) {
+    BrowserAccessibilityWin* target =
+        GetFromID(static_cast<int32_t>(target_id));
+    if (!target || !target->instance_active())
+      continue;
     CComObject<BrowserAccessibilityRelation>* relation;
     HRESULT hr =
         CComObject<BrowserAccessibilityRelation>::CreateInstance(&relation);
     DCHECK(SUCCEEDED(hr));
     relation->AddRef();
-    relation->Initialize(this, iaccessiblerelation_type);
-    relation->AddTarget(ids[i]);
+    relation->Initialize(this, relation_type);
+    relation->AddTarget(target_id);
     relations_.push_back(relation);
+    target->AddRelation(reverse_relation_type, target_id);

[dmazzoni, 2016/06/13 05:41:18]

I think this is going to keep adding this reverse relation to the target every
time this node is updated.

For example, suppose you have an <input> with aria-labelledby, and you focus it
and type into it. Every single time the <input> element is edited and its node
is updated, it's going to add a IA2_RELATION_LABEL_FOR relation to its target
label, since there's nothing to clear it.

One solution would be to clear all previous target relations first when a node
is updated. I'm wondering if a better solution might be to have some hash maps
of (source id, dest id) in a BrowserAccessibilityManager, that way we could more
easily update all of them when a node gets updated.

   }
 }
 
 void BrowserAccessibilityWin::UpdateRequiredAttributes() {
   // Expose slider value.
   if (ia_role() == ROLE_SYSTEM_PROGRESSBAR ||
       ia_role() == ROLE_SYSTEM_SCROLLBAR ||
       ia_role() == ROLE_SYSTEM_SLIDER) {
     base::string16 value_text = GetValueText();
     SanitizeStringAttributeForIA2(value_text, &value_text);
@@ skipping 623 matching lines @@
   return static_cast<BrowserAccessibilityWin*>(obj);
 }
 
 const BrowserAccessibilityWin*
 ToBrowserAccessibilityWin(const BrowserAccessibility* obj) {
   DCHECK(!obj || obj->IsNative());
   return static_cast<const BrowserAccessibilityWin*>(obj);
 }
 
 }  // namespace content