Handling of different types of empty alt

third_party/WebKit/Source/modules/accessibility/AXNodeObject.cpp

 /*
  * Copyright (C) 2012, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 1844 matching lines @@
       return String::Number(ValueForRange());
     }
 
     return StringValue();
   }
 
   // Step 2D from: http://www.w3.org/TR/accname-aam-1.1
   text_alternative =
       NativeTextAlternative(visited, name_from, related_objects, name_sources,
                             &found_text_alternative);
-  if (!text_alternative.IsEmpty() && !name_sources)
+  const bool has_text_alternative =
+      !text_alternative.IsEmpty() ||
+      name_from == kAXNameFromExplicitlyEmptyAttribute;
+  if (has_text_alternative && !name_sources)
     return text_alternative;
 
   // Step 2F / 2G from: http://www.w3.org/TR/accname-aam-1.1
   if (recursive || NameFromContents()) {
     name_from = kAXNameFromContents;
     if (name_sources) {
       name_sources->push_back(NameSource(found_text_alternative));
       name_sources->back().type = name_from;
     }
 
@@ skipping 748 matching lines @@
         }
       }
     }
     return text_alternative;
   }
 
   // 5.3 input type="image"
   if (input_element &&
       input_element->getAttribute(typeAttr) == InputTypeNames::image) {
     // alt attr
-    name_from = kAXNameFromAttribute;
+    const AtomicString& alt = input_element->getAttribute(altAttr);
+    const bool isEmpty = alt.IsEmpty() && !alt.IsNull();

[dmazzoni, 2017/05/01 17:49:23]

nit: isEmpty -> is_empty (just as you were getting used
to the style! At least it's consistent everywhere now)

[aleventhal, 2017/05/17 17:45:47]

What would I do without you! :)

+    name_from =
+        isEmpty ? kAXNameFromExplicitlyEmptyAttribute : kAXNameFromAttribute;
     if (name_sources) {
       name_sources->push_back(NameSource(*found_text_alternative, altAttr));
       name_sources->back().type = name_from;
     }
-    const AtomicString& alt = input_element->getAttribute(altAttr);
     if (!alt.IsNull()) {
       text_alternative = alt;
       if (name_sources) {
         NameSource& source = name_sources->back();
         source.attribute_value = alt;
         source.text = text_alternative;
         *found_text_alternative = true;
       } else {
         return text_alternative;
       }
@@ skipping 121 matching lines @@
         }
       }
     }
     return text_alternative;
   }
 
   // 5.8 img or area Element
   if (isHTMLImageElement(GetNode()) || isHTMLAreaElement(GetNode()) ||
       (GetLayoutObject() && GetLayoutObject()->IsSVGImage())) {
     // alt
-    name_from = kAXNameFromAttribute;
+    const AtomicString& alt = GetAttribute(altAttr);
+    const bool isEmpty = alt.IsEmpty() && !alt.IsNull();
+    name_from =
+        isEmpty ? kAXNameFromExplicitlyEmptyAttribute : kAXNameFromAttribute;
     if (name_sources) {
       name_sources->push_back(NameSource(*found_text_alternative, altAttr));
       name_sources->back().type = name_from;
     }
-    const AtomicString& alt = GetAttribute(altAttr);
     if (!alt.IsNull()) {
       text_alternative = alt;
       if (name_sources) {
         NameSource& source = name_sources->back();
         source.attribute_value = alt;
         source.text = text_alternative;
         *found_text_alternative = true;
       } else {
         return text_alternative;
       }
@@ skipping 420 matching lines @@
     return String();
   return ToTextControlElement(node)->StrippedPlaceholder();
 }
 
 DEFINE_TRACE(AXNodeObject) {
   visitor->Trace(node_);
   AXObject::Trace(visitor);
 }
 
 }  // namespace blink