Implement computedRole and computedName (behind a flag)

Source/modules/accessibility/AXObject.h

 /*
  * Copyright (C) 2008, 2009, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nuanti Ltd.
  *
  * 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.
@@ skipping 22 matching lines @@
 #include "core/editing/VisiblePosition.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/LayoutRect.h"
 #include "wtf/Forward.h"
 #include "wtf/RefPtr.h"
 #include "wtf/Vector.h"
 
 namespace blink {
 
 class AXObject;
+class AXObjectCache;
 class AXObjectCacheImpl;
 class Element;
 class FrameView;
 class IntPoint;
 class Node;
 class RenderObject;
 class ScrollableArea;
 class Widget;
 
 typedef unsigned AXID;
 
 enum AccessibilityRole {
+    NoRole = 0,

[dmazzoni, 2014/12/09 00:49:51]

I still vote for reusing UnknownRole rather than introducing a new NoRole.

If you introduce NoRole, you'll have to add a WebAXRole and plumb it through to
Chromium code too.

[aboxhall, 2014/12/13 01:38:36]

Is that accurate? It seems to compile and run fine without it. Note that we're
never actually setting it as something's official role - it's a placeholder for
"this thing doesn't have any particular role".

It's also nice to have a zero value so that NumRoles accurately reflects the
number of roles.

[dmazzoni, 2014/12/16 19:18:19]

Switch statements on enums should always explicitly handle all cases - it's a
very important tool to catch bugs at compile time. The only reason we can't do
that now is because Blink is a separate repository. As soon as the repositories
merge I'm going to fix that.

Right now we have to manually ensure that all Blink role enums are handled by
Chromium. By introducing a role that Blink won't actually return, you're
imposing a cognitive load on anyone who's tracing through the code and trying to
figure out if we're handling all of the possible roles.
Yes, but how is that different than UnknownRole? It's just a different name for
the same thing.
Great, so you're welcome to move UnknownRole to the top of the list and set it
to value 0.

[aboxhall, 2014/12/16 23:56:37]

Done.

     AlertDialogRole = 1,
     AlertRole,
     AnnotationRole,
     ApplicationRole,
     ArticleRole,
     BannerRole,
     BlockquoteRole,
     BusyIndicatorRole,
     ButtonRole,
     CanvasRole,
@@ skipping 95 matching lines @@
     TimerRole,
     ToggleButtonRole,
     ToolbarRole,
     TreeGridRole,
     TreeItemRole,
     TreeRole,
     UnknownRole,
     UserInterfaceTooltipRole,
     WebAreaRole,
     WindowRole,
+    NumRoles
 };
 
 enum AccessibilityTextSource {
     AlternativeText,
     ChildrenText,
     SummaryText,
     HelpText,
     VisibleText,
     TitleTagText,
     PlaceholderText,
@@ skipping 94 matching lines @@
 
         PlainTextRange(unsigned s, unsigned l)
             : start(s)
             , length(l)
         { }
 
         bool isNull() const { return !start && !length; }
     };
 
 protected:
-    AXObject();
+    AXObject(AXObjectCache*);
 
 public:
     virtual ~AXObject();
 
     // After constructing an AXObject, it must be given a
     // unique ID, then added to AXObjectCacheImpl, and finally init() must
     // be called last.
     void setAXObjectID(AXID axObjectID) { m_id = axObjectID; }
     virtual void init() { }
 
@@ skipping 274 matching lines @@
     virtual VisiblePosition visiblePositionForIndex(int) const { return VisiblePosition(); }
     int lineForPosition(const VisiblePosition&) const;
     virtual int index(const VisiblePosition&) const { return -1; }
     virtual void lineBreaks(Vector<int>&) const { }
 
     // Static helper functions.
     static bool isARIAControl(AccessibilityRole);
     static bool isARIAInput(AccessibilityRole);
     static AccessibilityRole ariaRoleToWebCoreRole(const String&);
     static IntRect boundingBoxForQuads(RenderObject*, const Vector<FloatQuad>&);
+    static const AtomicString& roleName(const AccessibilityRole);
 
 protected:
     AXID m_id;
     AccessibilityChildrenVector m_children;
     mutable bool m_haveChildren;
     AccessibilityRole m_role;
     AXObjectInclusion m_lastKnownIsIgnoredValue;
     LayoutRect m_explicitElementRect;
 
     virtual bool computeAccessibilityIsIgnored() const { return true; }
@@ skipping 10 matching lines @@
     bool m_detached;
 
     mutable AXObject* m_parent;
 
     // The following cached attribute values (the ones starting with m_cached*)
     // are only valid if m_lastModificationCount matches AXObjectCacheImpl::modificationCount().
     mutable int m_lastModificationCount;
     mutable bool m_cachedIsIgnored;
     mutable const AXObject* m_cachedLiveRegionRoot;
 
+    AXObjectCacheImpl* m_axObjectCache;
+
     // Updates the cached attribute values. This may be recursive, so to prevent deadlocks,
     // functions called here may only search up the tree (ancestors), not down.
     void updateCachedAttributeValuesIfNeeded() const;
 };
 
 #define DEFINE_AX_OBJECT_TYPE_CASTS(thisType, predicate) \
     DEFINE_TYPE_CASTS(thisType, AXObject, object, object->predicate, object.predicate)
 
 } // namespace blink
 
 #endif // AXObject_h