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// 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_H_
#define CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_
#include <vector>
#include "base/containers/hash_tables.h"
#include "base/macros.h"
#include "base/memory/weak_ptr.h"
#include "content/common/ax_content_node_data.h"
#include "content/public/renderer/render_frame_observer.h"
#include "content/renderer/accessibility/blink_ax_tree_source.h"
#include "third_party/WebKit/public/web/WebAXObject.h"
#include "ui/accessibility/ax_tree_serializer.h"
struct AccessibilityHostMsg_EventParams;
namespace blink {
class WebDocument;
class WebNode;
};
namespace content {
class RenderFrameImpl;
// The browser process implements native accessibility APIs, allowing
// assistive technology (e.g., screen readers, magnifiers) to access and
// control the web contents with high-level APIs. These APIs are also used
// by automation tools, and Windows 8 uses them to determine when the
// on-screen keyboard should be shown.
//
// An instance of this class belongs to RenderFrameImpl. Accessibility is
// initialized based on the AccessibilityMode of RenderFrameImpl; it lazily
// starts as Off or EditableTextOnly depending on the operating system, and
// switches to Complete if assistive technology is detected or a flag is set.
//
// A tree of accessible objects is built here and sent to the browser process;
// the browser process maintains this as a tree of platform-native
// accessible objects that can be used to respond to accessibility requests
// from other processes.
//
// This class implements complete accessibility support for assistive
// technology. It 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 RendererAccessibility : public RenderFrameObserver {
public:
// Request a one-time snapshot of the accessibility tree without
// enabling accessibility if it wasn't already enabled.
static void SnapshotAccessibilityTree(
RenderFrameImpl* render_frame,
AXContentTreeUpdate* response);
explicit RendererAccessibility(RenderFrameImpl* render_frame);
~RendererAccessibility() override;
// RenderFrameObserver implementation.
bool OnMessageReceived(const IPC::Message& message) override;
// Called when an accessibility notification occurs in Blink.
void HandleWebAccessibilityEvent(const blink::WebAXObject& obj,
blink::WebAXEvent event);
// Called when a new find in page result is highlighted.
void HandleAccessibilityFindInPageResult(
int identifier,
int match_index,
const blink::WebAXObject& start_object,
int start_offset,
const blink::WebAXObject& end_object,
int end_offset);
void AccessibilityFocusedNodeChanged(const blink::WebNode& node);
// This can be called before deleting a RendererAccessibility instance due
// to the accessibility mode changing, as opposed to during frame destruction
// (when there'd be no point).
void DisableAccessibility();
void HandleAXEvent(const blink::WebAXObject& obj, ui::AXEvent event);
protected:
// Returns the main top-level document for this page, or NULL if there's
// no view or frame.
blink::WebDocument GetMainDocument();
// 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();
// The RenderFrameImpl that owns us.
RenderFrameImpl* render_frame_;
private:
// Handlers for messages from the browser to the renderer.
void OnDoDefaultAction(int acc_obj_id);
void OnEventsAck();
void OnFatalError();
void OnHitTest(gfx::Point point);
void OnSetAccessibilityFocus(int acc_obj_id);
void OnReset(int reset_token);
void OnScrollToMakeVisible(int acc_obj_id, gfx::Rect subfocus);
void OnScrollToPoint(int acc_obj_id, gfx::Point point);
void OnSetScrollOffset(int acc_obj_id, gfx::Point offset);
void OnSetFocus(int acc_obj_id);
void OnSetSelection(int anchor_acc_obj_id,
int anchor_offset,
int focus_acc_obj_id,
int focus_offset);
void OnSetValue(int acc_obj_id, base::string16 value);
void OnShowContextMenu(int acc_obj_id);
// 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.
using BlinkAXTreeSerializer =
ui::AXTreeSerializer<blink::WebAXObject,
AXContentNodeData,
AXContentTreeData>;
BlinkAXTreeSerializer 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_;
// Nonzero if the browser requested we reset the accessibility state.
// We need to return this token in the next IPC.
int reset_token_;
// So we can queue up tasks to be executed later.
base::WeakPtrFactory<RendererAccessibility> weak_factory_;
DISALLOW_COPY_AND_ASSIGN(RendererAccessibility);
};
} // namespace content
#endif // CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_
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