Initial skeleton of Accessibility Object Model Phase 1

third_party/WebKit/Source/core/dom/AccessibleNode.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef AccessibleNode_h
+#define AccessibleNode_h
+
+#include "bindings/core/v8/ScriptWrappable.h"
+#include "core/CoreExport.h"
+#include "wtf/HashMap.h"
+#include "wtf/text/AtomicString.h"
+#include "wtf/text/AtomicStringHash.h"
+
+namespace blink {
+
+class Element;
+
+// All of the properties of AccessibleNode that have type "string".
+// TODO(dmazzoni): Add similar enums for all of the properties with
+// type bool, float, reference, and reference list.
+enum class AOMStringProperty { kFirst, kRole = kFirst, kLabel, kCount };
+
+const unsigned kAOMStringPropertyCount =
+    static_cast<unsigned>(AOMStringProperty::kCount);
+
+// Accessibility Object Model node
+// Explainer: https://github.com/WICG/aom/blob/master/explainer.md
+// Spec: https://wicg.github.io/aom/spec/
+class CORE_EXPORT AccessibleNode
+    : public GarbageCollectedFinalized<AccessibleNode>,
+      public ScriptWrappable {
+  DEFINE_WRAPPERTYPEINFO();
+
+ public:
+  explicit AccessibleNode(Element*);
+  virtual ~AccessibleNode();
+
+  // Returns the given string property if the Element has an AccessibleNode,
+  // otherwise returns the equivalent ARIA attribute.
+  static const AtomicString& getProperty(Element*, AOMStringProperty);
+
+  AtomicString role() const;
+  void setRole(const AtomicString&);
+
+  AtomicString label() const;
+  void setLabel(const AtomicString&);
+
+  DECLARE_VIRTUAL_TRACE();
+
+ private:
+  AtomicString m_stringProperties[kAOMStringPropertyCount];

[esprehn, 2017/03/24 01:59:39]

fwiw I was actually suggesting using a Vector of pairs, since that avoids making
your object huge when only a few properties are set, and the linear lookup cost
is probably not that bad for this

[dmazzoni, 2017/03/24 17:51:12]

Oh good, I like that better.

Do you see anyone else using this pattern? Maybe we should
have a VectorMap class that stores a vector of pairs but
presents a map-like interface.

+  bool m_stringPropertyDirty[kAOMStringPropertyCount] = {false};

[esprehn, 2017/03/24 01:59:39]

I think you want a std::bitset ?

I don't think you need this though, use the null value of AtomicString to signal
if the value is set or not. assigning null from the AOM should be equivalent to
doing a reset.

[aboxhall, 2017/03/24 02:17:51]

We want this to work equivalently to value, where once you have set the property
the attribute is ignored forever.

[dmazzoni, 2017/03/24 17:51:12]

Now that I'm using a vector of pairs, we can simply use presence of
the property in the vector to indicate whether it's ever been set or not.
No explicit bit field needed.

As Alice said, the current plan is to make it work like value.
That seems to be the rough consensus now so I want to implement it
that way, but it's definitely not set in stone - feel free to make an
argument for other behavior on the issue.

+
+  // This object's owner Element.
+  WeakMember<Element> m_element;
+};
+
+}  // namespace blink
+
+#endif  // AccessibleNode_h