Re-land: Implement NativeViewAccessibilityWin using AXPlatformNodeWin.

ui/accessibility/platform/ax_platform_node_delegate.h

 // Copyright 2014 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 UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
 #define UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_
 
 #include "ui/accessibility/ax_enums.h"
 #include "ui/accessibility/ax_export.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace ui {
 
 struct AXNodeData;
 class AXPlatformNode;
 
+// An object that wants to be accessible should derive from this class.
+// AXPlatformNode subclasses use this interface to query all of the information
+// about the object in order to implement native accessibility APIs.
+//
+// Note that AXPlatformNode has support for accessibility trees where some
+// of the objects in the tree are not implemented using AXPlatformNode.
+// For example, you may have a native window with platform-native widgets
+// in it, but in that window you have custom controls that use AXPlatformNode
+// to provide accessibility. That's why GetParent, ChildAtIndex, HitTestSync,
+// and GetFocus all return a gfx::NativeViewAccessible - so you can return a
+// native accessible if necessary, and AXPlatformNode::GetNativeViewAccessible
+// otherwise.
 class AX_EXPORT AXPlatformNodeDelegate {
  public:
   // Get the accessibility data that should be exposed for this node.
-  virtual AXNodeData* GetData() = 0;
+  // Virtually all of the information is obtained from this structure
+  // (role, state, name, cursor position, etc.) - the rest of this interface
+  // is mostly to implement support for walking the accessibility tree.
+  virtual const AXNodeData& GetData() = 0;
 
-  // Get the parent of the node unless it's the root, then it returns NULL.
+  // Get the parent of the node, which may be an AXPlatformNode or it may
+  // be a native accessible object implemented by another class.
   virtual gfx::NativeViewAccessible GetParent() = 0;
 
   // Get the number of children of this node.
   virtual int GetChildCount() = 0;
 
-  // Get the child of a node from [0...GetChildCount() - 1]
+  // Get the child of a node given a 0-based index.
   virtual gfx::NativeViewAccessible ChildAtIndex(int index) = 0;
 
   // Get the offset to convert local coordinates to screen global coordinates.
   virtual gfx::Vector2d GetGlobalCoordinateOffset() = 0;
 
+  // Do a *synchronous* hit test of the given location in global screen
+  // coordinates, and the node within this node's subtree (inclusive) that's
+  // hit, if any.
+  //
+  // If the result is anything other than this object or NULL, it will be
+  // hit tested again recursively - that allows hit testing to work across
+  // implementation classes. It's okay to take advantage of this and return
+  // only an immediate child and not the deepest descendant.
+  //
+  // This function is mainly used by accessibility debugging software.
+  // Platforms with touch accessibility use a different asynchronous interface.
+  virtual gfx::NativeViewAccessible HitTestSync(int x, int y) = 0;
+
+  // Return the node within this node's subtree (inclusive) that currently
+  // has focus.
+  virtual gfx::NativeViewAccessible GetFocus() = 0;
+
   //
   // Events.
   //
-  virtual void NotifyAccessibilityEvent(ui::AXEvent event_type) = 0;
 
+  // Return the platform-native GUI object that should be used as a target
+  // for accessibility events.
+  virtual gfx::AcceleratedWidget GetTargetForNativeAccessibilityEvent() = 0;
+
+  //
+  // Actions.
+  //
+
+  // Perform the default action, e.g. click a button, follow a link, or
+  // toggle a checkbox.
+  virtual void DoDefaultAction() = 0;
+
+  // Change the value of a control, such as the text content of a text field.
+  virtual bool SetStringValue(const base::string16& new_value) = 0;
 };
 
 }  // namespace ui
 
 #endif  // UI_ACCESSIBILITY_PLATFORM_AX_PLATFORM_NODE_DELEGATE_H_