blob: 4c8884373d6c1ef25ed04c62d47369d1ccb310da (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
|
// 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_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_
#define CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_
#include <vector>
#include "base/basictypes.h"
#include "base/compiler_specific.h"
#include "base/memory/singleton.h"
#include "content/common/accessibility_mode_enums.h"
#include "content/public/browser/browser_accessibility_state.h"
namespace content {
// 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 BrowserAccessibilityStateImpl
: public base::RefCountedThreadSafe<BrowserAccessibilityStateImpl>,
public BrowserAccessibilityState {
public:
BrowserAccessibilityStateImpl();
static BrowserAccessibilityStateImpl* GetInstance();
void EnableAccessibility() override;
void DisableAccessibility() override;
void ResetAccessibilityMode() override;
void OnScreenReaderDetected() override;
bool IsAccessibleBrowser() override;
void AddHistogramCallback(base::Closure callback) override;
void UpdateHistogramsForTesting() override;
AccessibilityMode accessibility_mode() const { return accessibility_mode_; };
// Adds the given accessibility mode to the current accessibility mode bitmap.
void AddAccessibilityMode(AccessibilityMode mode);
// Removes the given accessibility mode from the current accessibility mode
// bitmap, managing the bits that are shared with other modes such that a
// bit will only be turned off when all modes that depend on it have been
// removed.
void RemoveAccessibilityMode(AccessibilityMode mode);
private:
friend class base::RefCountedThreadSafe<BrowserAccessibilityStateImpl>;
friend struct DefaultSingletonTraits<BrowserAccessibilityStateImpl>;
// Resets accessibility_mode_ to the default value.
void ResetAccessibilityModeValue();
// Called a short while after startup to allow time for the accessibility
// state to be determined. Updates histograms with the current state.
void UpdateHistograms();
// Leaky singleton, destructor generally won't be called.
~BrowserAccessibilityStateImpl() override;
void UpdatePlatformSpecificHistograms();
// Updates the accessibility mode of all web contents, including swapped out
// ones. |add| specifies whether the mode should be added or removed.
void AddOrRemoveFromAllWebContents(AccessibilityMode mode, bool add);
AccessibilityMode accessibility_mode_;
std::vector<base::Closure> histogram_callbacks_;
DISALLOW_COPY_AND_ASSIGN(BrowserAccessibilityStateImpl);
};
} // namespace content
#endif // CONTENT_BROWSER_ACCESSIBILITY_BROWSER_ACCESSIBILITY_STATE_IMPL_H_
|
