content/renderer/accessibility/renderer_accessibility_complete.h

// Copyright (c) 2012 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 CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_COMPLETE_H_
#define CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_COMPLETE_H_

#include <set>
#include <vector>

#include "base/containers/hash_tables.h"
#include "base/memory/weak_ptr.h"
#include "content/public/renderer/render_view_observer.h"
#include "content/renderer/accessibility/blink_ax_tree_source.h"
#include "content/renderer/accessibility/renderer_accessibility.h"
#include "third_party/WebKit/public/web/WebAXEnums.h"
#include "third_party/WebKit/public/web/WebAXObject.h"
#include "ui/accessibility/ax_node_data.h"
#include "ui/accessibility/ax_tree_serializer.h"

namespace blink {
class WebDocument;
class WebNode;
};

namespace content {
class RenderViewImpl;

// This is the subclass of RendererAccessibility that implements
// complete accessibility support for assistive technology (as opposed to
// partial support - see RendererAccessibilityFocusOnly).
//
// This version turns on Blink's accessibility code and sends
// a serialized representation of that tree whenever it changes. It also
// handles requests from the browser to perform accessibility actions on
// nodes in the tree (e.g., change focus, or click on a button).
class CONTENT_EXPORT RendererAccessibilityComplete
    : public RendererAccessibility {
 public:
  explicit RendererAccessibilityComplete(RenderViewImpl* render_view);
  virtual ~RendererAccessibilityComplete();

  // RenderView::Observer implementation.
  virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
  virtual void FocusedNodeChanged(const blink::WebNode& node) OVERRIDE;
  virtual void DidFinishLoad(blink::WebLocalFrame* frame) OVERRIDE;

  // RendererAccessibility.
  virtual void HandleWebAccessibilityEvent(
      const blink::WebAXObject& obj, blink::WebAXEvent event) OVERRIDE;
  virtual RendererAccessibilityType GetType() OVERRIDE;

  void HandleAXEvent(const blink::WebAXObject& obj, ui::AXEvent event);

 protected:
  // Send queued events from the renderer to the browser.
  void SendPendingAccessibilityEvents();

  // Check the entire accessibility tree to see if any nodes have
  // changed location, by comparing their locations to the cached
  // versions. If any have moved, send an IPC with the new locations.
  void SendLocationChanges();

 private:
  // Handlers for messages from the browser to the renderer.
  void OnDoDefaultAction(int acc_obj_id);
  void OnEventsAck();
  void OnChangeScrollPosition(int acc_obj_id, int scroll_x, int scroll_y);
  void OnScrollToMakeVisible(int acc_obj_id, gfx::Rect subfocus);
  void OnScrollToPoint(int acc_obj_id, gfx::Point point);
  void OnSetFocus(int acc_obj_id);
  void OnSetTextSelection(int acc_obj_id, int start_offset, int end_offset);
  void OnHitTest(gfx::Point point);
  void OnFatalError();

  // So we can queue up tasks to be executed later.
  base::WeakPtrFactory<RendererAccessibilityComplete> weak_factory_;

  // Events from Blink are collected until they are ready to be
  // sent to the browser.
  std::vector<AccessibilityHostMsg_EventParams> pending_events_;

  // The adapter that exposes Blink's accessibility tree to AXTreeSerializer.
  BlinkAXTreeSource tree_source_;

  // The serializer that sends accessibility messages to the browser process.
  ui::AXTreeSerializer<blink::WebAXObject> serializer_;

  // Current location of every object, so we can detect when it moves.
  base::hash_map<int, gfx::Rect> locations_;

  // The most recently observed scroll offset of the root document element.
  // TODO(dmazzoni): remove once https://bugs.webkit.org/show_bug.cgi?id=73460
  // is fixed.
  gfx::Size last_scroll_offset_;

  // Set if we are waiting for an accessibility event ack.
  bool ack_pending_;

  DISALLOW_COPY_AND_ASSIGN(RendererAccessibilityComplete);
};

#endif  // CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_COMPLETE_H_

}  // namespace content