1// Copyright (c) 2010 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5#ifndef CHROME_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_ 6#define CHROME_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_ 7#pragma once 8 9#include "base/basictypes.h" 10 11template <typename T> struct DefaultSingletonTraits; 12 13// The BrowserAccessibilityState class is used to determine if Chrome should be 14// customized for users with assistive technology, such as screen readers. We 15// modify the behavior of certain user interfaces to provide a better experience 16// for screen reader users. The way we detect a screen reader program is 17// different for each platform. 18// 19// Screen Reader Detection 20// (1) On windows many screen reader detection mechinisms will give false 21// positives like relying on the SPI_GETSCREENREADER system parameter. In Chrome 22// we attempt to dynamically detect a MSAA client screen reader by calling 23// NotifiyWinEvent in WidgetWin with a custom ID and wait to see if the ID 24// is requested by a subsequent call to WM_GETOBJECT. 25// (2) On mac we detect if VoiceOver is running. This is stored in a preference 26// file for Universal Access with the key "voiceOverOnOffKey". 27class BrowserAccessibilityState { 28 public: 29 // Returns the singleton instance. 30 static BrowserAccessibilityState* GetInstance(); 31 32 ~BrowserAccessibilityState(); 33 34 // Called when screen reader client is detected. 35 void OnScreenReaderDetected(); 36 37 // Returns true if the Chrome browser should be customized for accessibility. 38 bool IsAccessibleBrowser(); 39 40 private: 41 BrowserAccessibilityState(); 42 friend struct DefaultSingletonTraits<BrowserAccessibilityState>; 43 44 // Set to true when a screen reader client is detected. 45 bool screen_reader_active_; 46 47 DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityState); 48}; 49 50#endif // CHROME_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_H_ 51