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// Copyright (c) 2011 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_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_
#define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_
#pragma once
#include "base/basictypes.h"
#include "content/common/content_export.h"
template <typename T> struct DefaultSingletonTraits;
// The BrowserAccessibilityState class is used to determine if Chrome should be
// customized for users with assistive technology, such as screen readers. We
// modify the behavior of certain user interfaces to provide a better experience
// for screen reader users. The way we detect a screen reader program is
// different for each platform.
//
// Screen Reader Detection
// (1) On windows many screen reader detection mechinisms will give false
// positives like relying on the SPI_GETSCREENREADER system parameter. In Chrome
// we attempt to dynamically detect a MSAA client screen reader by calling
// NotifiyWinEvent in NativeWidgetWin with a custom ID and wait to see if the ID
// is requested by a subsequent call to WM_GETOBJECT.
// (2) On mac we detect dynamically if VoiceOver is running. We rely upon the
// undocumented accessibility attribute @"AXEnhancedUserInterface" which is set
// when VoiceOver is launched and unset when VoiceOver is closed. This is an
// improvement over reading defaults preference values (which has no callback
// mechanism).
class CONTENT_EXPORT BrowserAccessibilityState {
public:
// Returns the singleton instance.
static BrowserAccessibilityState* GetInstance();
~BrowserAccessibilityState();
// Called when screen reader client is detected.
void OnScreenReaderDetected();
// Returns true if the browser should be customized for accessibility.
bool IsAccessibleBrowser();
private:
BrowserAccessibilityState();
friend struct DefaultSingletonTraits<BrowserAccessibilityState>;
// Set to true when a screen reader client is detected.
bool screen_reader_active_;
DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityState);
};
#endif // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_
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