Bug 468451 - Images with empty alt attribute no longer get an empty accessible name, but return NULL instead, r=aaronlev, marcoz, davidb

accessible/public/nsIAccessible.idl

@@ -103,7 +103,14 @@ interface nsIAccessible : nsISupports
   readonly attribute long indexInParent;
 
   /**
-   * Accessible name -- the main text equivalent for this node
+   * Accessible name -- the main text equivalent for this node. The name is
+   * specified by ARIA or by native markup. Example of ARIA markup is
+   * aria-labelledby attribute placed on element of this accessible. Example
+   * of native markup is HTML label linked with HTML element of this accessible.
+   *
+   * Value can be string or null. A null value indicates that AT may attempt to
+   * compute the name. Any string value, including the empty string, should be
+   * considered author-intentional, and respected.
    */
   attribute AString name;
 

accessible/src/base/nsAccessible.cpp

@@ -308,7 +308,7 @@ nsAccessible::GetName(nsAString& aName)
   if (content->GetAttr(kNameSpaceID_None, tooltipAttr, name)) {
     name.CompressWhitespace();
     aName = name;
-  } else {
+  } else if (rv != NS_OK_EMPTY_NAME) {
     aName.SetIsVoid(PR_TRUE);
   }
 

accessible/src/base/nsAccessible.h

@@ -66,9 +66,14 @@ class nsIDOMNode;
 class nsIAtom;
 class nsIView;
 
+// see nsAccessible::GetAttrValue
 #define NS_OK_NO_ARIA_VALUE \
 NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_GENERAL, 0x21)
 
+// see nsAccessible::GetNameInternal
+#define NS_OK_EMPTY_NAME \
+NS_ERROR_GENERATE_SUCCESS(NS_ERROR_MODULE_GENERAL, 0x23)
+
 // Saves a data member -- if child count equals this value we haven't
 // cached children or child count yet
 enum { eChildCountUninitialized = -1 };
@@ -135,7 +140,13 @@ public:
 
   /**
    * Returns the accessible name provided by native markup. It doesn't take
-   * into account ARIA stuffs used to specify the name.
+   * into account ARIA markup used to specify the name.
+   *
+   * @param  aName             [out] the accessible name
+   *
+   * @return NS_OK_EMPTY_NAME  points empty name was specified by native markup
+   *                           explicitly (see nsIAccessible::name attribute for
+   *                           details)
    */
   virtual nsresult GetNameInternal(nsAString& aName);
 

accessible/src/html/nsHTMLImageAccessible.cpp

@@ -127,10 +127,6 @@ nsHTMLImageAccessible::GetStateInternal(PRUint32 *aState, PRUint32 *aExtraState)
 nsresult
 nsHTMLImageAccessible::GetNameInternal(nsAString& aName)
 {
-  // No alt attribute means AT can repair if there is no accessible name
-  // alt="" with no title or aria-labelledby means image is presentational and 
-  // AT should leave accessible name empty
-
   nsCOMPtr<nsIContent> content(do_QueryInterface(mDOMNode));
   PRBool hasAltAttrib =
     content->GetAttr(kNameSpaceID_None, nsAccessibilityAtoms::alt, aName);
@@ -140,10 +136,12 @@ nsHTMLImageAccessible::GetNameInternal(nsAString& aName)
   nsresult rv = nsAccessible::GetNameInternal(aName);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  if (aName.IsVoid() && hasAltAttrib) {
-    // No accessible name but empty alt attribute is present. This means a name
-    // was provided by author and AT repair of the name isn't allowed.
-    aName.Truncate();
+  if (aName.IsEmpty() && hasAltAttrib) {
+    // No accessible name but empty 'alt' attribute is present. If further name
+    // computation algorithm doesn't provide non empty name then it means
+    // an empty 'alt' attribute was used to indicate a decorative image (see
+    // nsIAccessible::name attribute for details).
+    return NS_OK_EMPTY_NAME;
   }
 
   return NS_OK;

accessible/tests/mochitest/test_nsIAccessibleImage.html

@@ -147,10 +147,10 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=429659
       testThis("linkedImageWithTitle", "Link to MoFo", "moz.png", 93, 42);
 
       // Test simple image with empty alt attribute
-//      testThis("nonLinkedImageEmptyAlt", "", "moz.png", 89, 38);
+      testThis("nonLinkedImageEmptyAlt", "", "moz.png", 89, 38);
 
       // Test linked image with empty alt attribute
-//      testThis("linkedImageEmptyAlt", "", "moz.png", 93, 42);
+      testThis("linkedImageEmptyAlt", "", "moz.png", 93, 42);
 
       // Test simple image with empty alt attribute and title
       testThis("nonLinkedImageEmptyAltAndTitle", "MozillaFoundation", "moz.png", 89, 38);