Bug 358884 Add assertion to ensure accessible object with a text child supports the right interfaces

patch by Evan Yan at sun.com r=aaronleventhal,hwaara

accessible/src/atk/nsAccessibleWrap.cpp

@@ -810,6 +810,12 @@ getRoleCB(AtkObject *aAtkObj)
 {
     NS_ENSURE_SUCCESS(CheckMaiAtkObject(aAtkObj), ATK_ROLE_INVALID);
 
+#ifdef DEBUG_A11Y
+        nsAccessibleWrap *testAccWrap =
+            NS_REINTERPRET_CAST(MaiAtkObject*, aAtkObj)->accWrap;
+        NS_ASSERTION(nsAccessible::IsTextInterfaceSupportCorrect(testAccWrap), "Does not support nsIAccessibleText when it should");
+#endif
+
     if (aAtkObj->role == ATK_ROLE_INVALID) {
         nsAccessibleWrap *accWrap =
             NS_REINTERPRET_CAST(MaiAtkObject*, aAtkObj)->accWrap;

accessible/src/base/nsAccessible.cpp

@@ -107,6 +107,40 @@
 NS_IMPL_ADDREF_INHERITED(nsAccessible, nsAccessNode)
 NS_IMPL_RELEASE_INHERITED(nsAccessible, nsAccessNode)
 
+#ifdef DEBUG_A11Y
+/*
+ * static
+ * help method. to detect whether this accessible object implements
+ * nsIAccessibleText, when it is text or has text child node.
+ */
+PRBool nsAccessible::IsTextInterfaceSupportCorrect(nsIAccessible *aAccessible)
+{
+  PRBool foundText = PR_FALSE;
+
+  if (IsText(aAccessible)) {
+    foundText = PR_TRUE;
+  }
+  nsCOMPtr<nsIAccessible> child, nextSibling;
+  aAccessible->GetFirstChild(getter_AddRefs(child));
+  while (child) {
+    if (IsText(child)) {
+      foundText = PR_TRUE;
+      break;
+    }
+    child->GetNextSibling(getter_AddRefs(nextSibling));
+    child.swap(nextSibling);
+  }
+  if (foundText) {
+    // found text child node
+    nsCOMPtr<nsIAccessibleText> text = do_QueryInterface(aAccessible);
+    if (!text) {
+      return PR_FALSE;
+    }
+  }
+  return PR_TRUE; 
+}
+#endif
+
 nsresult nsAccessible::QueryInterface(REFNSIID aIID, void** aInstancePtr)
 {
   // Custom-built QueryInterface() knows when we support nsIAccessibleSelectable

accessible/src/base/nsAccessible.h

@@ -142,6 +142,10 @@ public:
                                    nsIFrame **aFirstTextFrame, const nsIFrame *aTextFrame);
 #endif
 
+#ifdef DEBUG_A11Y
+  static PRBool IsTextInterfaceSupportCorrect(nsIAccessible *aAccessible);
+#endif
+
   static PRBool IsCorrectFrameType(nsIFrame* aFrame, nsIAtom* aAtom);
   static PRUint32 State(nsIAccessible *aAcc) { PRUint32 state; aAcc->GetFinalState(&state); return state; }
   static PRUint32 Role(nsIAccessible *aAcc) { PRUint32 role; aAcc->GetFinalRole(&role); return role; }

accessible/src/mac/mozAccessible.mm

@@ -366,6 +366,9 @@ ObjectOrUnignoredAncestor(id anObject)
 
 - (NSString*)role
 {
+#ifdef DEBUG_A11Y
+  NS_ASSERTION(nsAccessible::IsTextInterfaceSupportCorrect(mGeckoAccessible), "Does not support nsIAccessibleText when it should");
+#endif
   PRUint32 roleInt = 0;
   mGeckoAccessible->GetFinalRole (&roleInt);
   return AXRoles[roleInt]; // see nsRoleMap.h

accessible/src/msaa/nsAccessibleWrap.cpp

@@ -434,6 +434,10 @@ STDMETHODIMP nsAccessibleWrap::get_accRole(
   if (!xpAccessible)
     return E_FAIL;
 
+#ifdef DEBUG_A11Y
+  NS_ASSERTION(nsAccessible::IsTextInterfaceSupportCorrect(xpAccessible), "Does not support nsIAccessibleText when it should");
+#endif
+
   PRUint32 xpRole = 0, msaaRole = 0;
   if (NS_FAILED(xpAccessible->GetFinalRole(&xpRole)))
     return E_FAIL;