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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies). |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 |
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42 /*! |
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43 \page qt4-accessibility.html |
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44 \title Cross-Platform Accessibility Support in Qt 4 |
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45 |
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46 \contentspage {What's New in Qt 4}{Home} |
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47 \previouspage The New Qt Designer |
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48 \nextpage The Qt 4 Database GUI Layer |
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49 |
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50 Qt 4 allows developers to write cross-platform applications that |
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51 are usable by visually impaired users as well as by users with |
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52 other disabilities. Qt accessibility will make applications |
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53 accessible to more users and opens the governmental market, where |
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54 accessibility is often a requirement. |
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55 |
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56 \section1 General Overview |
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57 |
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58 The accessibility classes have been extended in |
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59 various ways since Qt 3. We added new functions and new enum |
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60 values, and revised the API to make it more consistent with the |
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61 rest of Qt. We also added two properties to QWidget, |
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62 \l{QWidget::accessibleName}{accessibleName} and |
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63 \l{QWidget::accessibleDescription}{accessibleDescription}, that |
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64 can be set in \e{Qt Designer} to provide basic help texts without |
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65 having to write any code. |
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66 |
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67 Qt's accessibility architecture is as follows. Qt offers one |
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68 generic interface, QAccessibleInterface, that can be used to |
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69 wrap all widgets and objects (e.g., QPushButton). This single |
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70 interface provides all the metadata necessary for the assistive |
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71 technologies. Qt provides implementations of this interface for |
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72 its built-in widgets as plugins. |
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73 |
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74 A more detailed overview of the accessibility support in Qt can |
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75 be found on the \l Accessibility page. |
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76 |
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77 \section1 Enabling Accessibility Support |
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78 |
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79 By default, Qt applications are run with accessibility support |
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80 enabled on Windows and Mac OS X. On Unix/X11 platforms, applications |
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81 must be launched in an environment with the \c QT_ACCESSIBILITY |
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82 variable set to 1. For example, this is set in the following way with |
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83 the bash shell: |
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84 |
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85 \snippet doc/src/snippets/code/doc_src_qt4-accessibility.qdoc environment |
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86 |
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87 Accessibility features are built into Qt by default when the libraries |
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88 are configured and built. |
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89 |
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90 \section1 Creating New Accessible Interfaces |
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91 |
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92 When you develop custom widgets, you can create custom subclasses |
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93 of QAccessibleInterface and distribute them as plugins (using |
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94 QAccessiblePlugin) or compile them into the application. |
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95 Likewise, Qt's predefined accessibility support can be built as |
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96 plugin (the default) or directly into the Qt library. The main |
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97 advantage of using plugins is that the accessibility classes are |
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98 only loaded into memory if they are actually used; they don't |
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99 slow down the common case where no assistive technology is being |
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100 used. |
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101 |
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102 In addition to QAccessibleInterface, Qt includes two convenience |
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103 classes, QAccessibleObject and QAccessibleWidget, that |
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104 provide the lowest common denominator of metadata (e.g., widget |
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105 geometry, window title, basic help text). You can use them as |
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106 base classes when wrapping your custom QObject or QWidget |
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107 subclasses. |
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108 |
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109 Another new feature in Qt 4 is that Qt can now support other |
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110 backends in addition to the predefined ones. This is done by |
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111 subclassing QAccessibleBridge. |
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112 |
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113 \omit |
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114 \section1 Software Layering |
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115 |
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116 Qt Application |
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117 | links to |
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118 Qt Accessibility Module |
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119 | Plugin (in-process) |
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120 Qt ATK Bridge |
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121 | links to |
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122 ATK |
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123 | Plugin (in-process) |
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124 at-spi |
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125 | CORBA |
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126 assistive technologies |
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127 |
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128 Windows: |
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129 |
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130 Qt Application |
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131 | links to |
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132 Qt Accessibility Module |
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133 | COM (?) |
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134 MSAA |
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135 | ? |
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136 assistive technologies |
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137 |
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138 Mac: |
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139 |
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140 ? |
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141 \endomit |
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142 |
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143 \section1 Example Code |
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144 |
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145 The first example illustrates how to provide accessibility |
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146 information for a custom widget. We can use QAccessibleWidget as |
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147 a base class and reimplement various functions: |
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148 |
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149 \snippet doc/src/snippets/code/doc_src_qt4-accessibility.qdoc 0 |
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150 |
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151 Here's how we would implement the |
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152 \l{QAccessibleInterface::doAction()}{doAction()} function to call |
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153 a function named click() on the wrapped MyWidget object when the |
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154 user invokes the object's default action or "presses" it. |
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155 |
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156 \snippet doc/src/snippets/code/doc_src_qt4-accessibility.qdoc 1 |
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157 |
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158 To export the widget interface as a plugin, we must subclass |
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159 QAccessibleFactory: |
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160 |
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161 \snippet doc/src/snippets/code/doc_src_qt4-accessibility.qdoc 2 |
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162 */ |