Bug 455443 - cache the parent for the accessibilityAttributeValue(NSAccessibilityParentAttribute). r=surkov

accessible/src/mac/mozAccessible.h

@@ -46,16 +46,32 @@
 
 @interface mozAccessible : NSObject <mozAccessible>
 {
-  nsAccessibleWrap *mGeckoAccessible;  // weak reference; it owns us.
-  NSMutableArray   *mChildren;         // strong ref to array of children
+  /**
+   * Weak reference; it owns us.
+   */
+  nsAccessibleWrap* mGeckoAccessible;
   
-  // we can be marked as 'expired' if Shutdown() is called on our geckoAccessible.
-  // since we might still be retained by some third-party, we need to do cleanup
-  // in |expire|, and prevent any potential harm that could come from someone using us
-  // after this point.
+  /**
+   * Strong ref to array of children
+   */
+  NSMutableArray* mChildren;
+  
+  /** 
+   * Weak reference to the parent
+   */
+  mozAccessible* mParent;
+  
+  /**
+   * We can be marked as 'expired' if Shutdown() is called on our geckoAccessible.
+   * since we might still be retained by some third-party, we need to do cleanup
+   * in |expire|, and prevent any potential harm that could come from someone using us
+   * after this point.
+   */
   BOOL mIsExpired;
   
-  // the nsIAccessible role of our gecko accessible.
+  /**
+   * The nsIAccessible role of our gecko accessible.
+   */
   PRUint32        mRole;
 }
 
@@ -114,6 +130,9 @@
 // invalidates and removes all our children from our cached array.
 - (void)invalidateChildren;
 
+// invalidates the cached parent, used by invalidateChildren.
+- (void)invalidateParent;
+
 // makes ourselves "expired". after this point, we might be around if someone
 // has retained us (e.g., a third-party), but we really contain no information.
 - (void)expire;
@@ -124,7 +143,7 @@
 - (void)printHierarchyWithLevel:(unsigned)numSpaces;
 
 - (void)sanityCheckChildren;
-- (void)sanityCheckChildren:(NSArray *)theChildren;
+- (void)sanityCheckChildren:(NSArray*)theChildren;
 #endif
 
 // ---- NSAccessibility methods ---- //

accessible/src/mac/mozAccessible.mm

@@ -355,11 +355,15 @@ GetNativeFromGeckoAccessible(nsIAccessible *anAccessible)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK_NIL;
 
+  if (mParent)
+    return mParent;
+
   nsCOMPtr<nsIAccessible> accessibleParent(mGeckoAccessible->GetUnignoredParent());
   if (accessibleParent) {
     id nativeParent = GetNativeFromGeckoAccessible(accessibleParent);
-    if (nativeParent)
-      return GetClosestInterestingAccessible(nativeParent);
+    if (nativeParent) {
+      return mParent = GetClosestInterestingAccessible(nativeParent);
+    }
   }
   
   // GetUnignoredParent() returns null when there is no unignored accessible all the way up to
@@ -371,7 +375,8 @@ GetNativeFromGeckoAccessible(nsIAccessible *anAccessible)
   id nativeParent = GetNativeFromGeckoAccessible(static_cast<nsIAccessible*>(root));
   NSAssert1 (nativeParent, @"!!! we can't find a parent for %@", self);
   
-  return GetClosestInterestingAccessible(nativeParent);
+  mParent = GetClosestInterestingAccessible(nativeParent);
+  return mParent;
 
   NS_OBJC_END_TRY_ABORT_BLOCK_NIL;
 }
@@ -610,6 +615,8 @@ GetNativeFromGeckoAccessible(nsIAccessible *anAccessible)
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;
 
+  [mChildren makeObjectsPerformSelector:@selector(invalidateParent)];
+
   // make room for new children
   [mChildren release];
   mChildren = nil;
@@ -617,6 +624,11 @@ GetNativeFromGeckoAccessible(nsIAccessible *anAccessible)
   NS_OBJC_END_TRY_ABORT_BLOCK;
 }
 
+- (void)invalidateParent
+{
+  mParent = nil;
+}
+
 - (void)expire
 {
   NS_OBJC_BEGIN_TRY_ABORT_BLOCK;