Implemented IAccessible2 reverse relations.

content/browser/accessibility/browser_accessibility_win.cc

Index: content/browser/accessibility/browser_accessibility_win.cc
diff --git a/content/browser/accessibility/browser_accessibility_win.cc b/content/browser/accessibility/browser_accessibility_win.cc
index 88c5c8254a951210390b272d1ba3c65483f47732..4e2d2e8ab315a0bc46f3df8d6b3965b06efbb110 100644
--- a/content/browser/accessibility/browser_accessibility_win.cc
+++ b/content/browser/accessibility/browser_accessibility_win.cc
@@ -3526,11 +3526,20 @@ void BrowserAccessibilityWin::UpdateStep1ComputeWinAttributes() {
     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
@@ -4436,22 +4445,39 @@ bool BrowserAccessibilityWin::IsListBoxOptionOrMenuListOption() {
   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.

   }
 }