1 | /****************************************************************************
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2 | **
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3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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4 | ** All rights reserved.
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5 | ** Contact: Nokia Corporation ([email protected])
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7 | ** This file is part of the documentation of the Qt Toolkit.
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8 | **
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9 | ** $QT_BEGIN_LICENSE:FDL$
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13 | ** Software or, alternatively, in accordance with the terms contained in a
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14 | ** written agreement between you and Nokia.
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15 | **
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16 | ** GNU Free Documentation License
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17 | ** Alternatively, this file may be used under the terms of the GNU Free
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22 | ** If you have questions regarding the use of this file, please contact
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23 | ** Nokia at [email protected].
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24 | ** $QT_END_LICENSE$
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25 | **
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26 | ****************************************************************************/
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27 |
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28 | /*!
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29 | \example widgets/spinboxes
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30 | \title Spin Boxes Example
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31 |
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32 | The Spin Boxes example shows how to use the many different types of spin boxes
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33 | available in Qt, from a simple QSpinBox widget to more complex editors like
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34 | the QDateTimeEdit widget.
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35 |
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36 | \image spinboxes-example.png
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37 |
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38 | The example consists of a single \c Window class that is used to display the
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39 | different spin box-based widgets available with Qt.
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40 |
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41 | \section1 Window Class Definition
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42 |
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43 | The \c Window class inherits QWidget and contains two slots that are used
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44 | to provide interactive features:
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45 |
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46 | \snippet examples/widgets/spinboxes/window.h 0
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47 |
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48 | The private functions are used to set up each type of spin box in the window.
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49 | We use member variables to keep track of various widgets so that they can
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50 | be reconfigured when required.
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51 |
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52 | \section1 Window Class Implementation
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53 |
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54 | The constructor simply calls private functions to set up the different types
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55 | of spin box used in the example, and places each group in a layout:
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56 |
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57 | \snippet examples/widgets/spinboxes/window.cpp 0
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58 |
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59 | We use the layout to manage the arrangement of the window's child widgets,
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60 | and change the window title.
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61 |
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62 | The \c createSpinBoxes() function constructs a QGroupBox and places three
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63 | QSpinBox widgets inside it with descriptive labels to indicate the types of
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64 | input they expect.
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65 |
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66 | \snippet examples/widgets/spinboxes/window.cpp 1
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67 |
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68 | The first spin box shows the simplest way to use QSpinBox. It accepts values
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69 | from -20 to 20, the current value can be increased or decreased by 1 with
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70 | either the arrow buttons or \key{Up} and \key{Down} keys, and the default
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71 | value is 0.
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72 |
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73 | The second spin box uses a larger step size and displays a suffix to
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74 | provide more information about the type of data the number represents:
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75 |
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76 | \snippet examples/widgets/spinboxes/window.cpp 2
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77 |
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78 | This spin box also displays a
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79 | \l{QAbstractSpinBox::specialValueText}{special value} instead of the minimum
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80 | value defined for it. This means that it will never show \gui{0%}, but will
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81 | display \gui{Automatic} when the minimum value is selected.
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82 |
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83 | The third spin box shows how a prefix can be used:
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84 |
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85 | \snippet examples/widgets/spinboxes/window.cpp 4
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86 |
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87 | For simplicity, we show a spin box with a prefix and no suffix. It is also
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88 | possible to use both at the same time.
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89 |
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90 | \snippet examples/widgets/spinboxes/window.cpp 5
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91 |
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92 | The rest of the function sets up a layout for the group box and places each
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93 | of the widgets inside it.
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94 |
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95 | The \c createDateTimeEdits() function constructs another group box with a
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96 | selection of spin boxes used for editing dates and times.
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97 |
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98 | \snippet examples/widgets/spinboxes/window.cpp 6
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99 |
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100 | The first spin box is a QDateEdit widget that is able to accept dates
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101 | within a given range specified using QDate values. The arrow buttons and
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102 | \key{Up} and \key{Down} keys can be used to increase and decrease the
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103 | values for year, month, and day when the cursor is in the relevant section.
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104 |
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105 | The second spin box is a QTimeEdit widget:
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106 |
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107 | \snippet examples/widgets/spinboxes/window.cpp 7
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108 |
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109 | Acceptable values for the time are defined using QTime values.
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110 |
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111 | The third spin box is a QDateTimeEdit widget that can display both date and
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112 | time values, and we place a label above it to indicate the range of allowed
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113 | times for a meeting. These widgets will be updated when the user changes a
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114 | format string.
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115 |
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116 | \snippet examples/widgets/spinboxes/window.cpp 8
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117 |
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118 | The format string used for the date time editor, which is also shown in the
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119 | string displayed by the label, is chosen from a set of strings in a combobox:
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120 |
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121 | \snippet examples/widgets/spinboxes/window.cpp 9
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122 | \codeline
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123 | \snippet examples/widgets/spinboxes/window.cpp 10
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124 |
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125 | A signal from this combobox is connected to a slot in the \c Window class
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126 | (shown later).
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127 |
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128 | \snippet examples/widgets/spinboxes/window.cpp 11
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129 |
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130 | Each child widget of the group box in placed in a layout.
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131 |
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132 | The \c setFormatString() slot is called whenever the user selects a new
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133 | format string in the combobox. The display format for the QDateTimeEdit
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134 | widget is set using the raw string passed by the signal:
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135 |
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136 | \snippet examples/widgets/spinboxes/window.cpp 12
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137 |
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138 | Depending on the visible sections in the widget, we set a new date or time
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139 | range, and update the associated label to provide relevant information for
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140 | the user:
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141 |
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142 | \snippet examples/widgets/spinboxes/window.cpp 13
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143 |
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144 | When the format string is changed, there will be an appropriate label and
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145 | entry widget for dates, times, or both types of input.
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146 |
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147 | The \c createDoubleSpinBoxes() function constructs three spin boxes that are
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148 | used to input double-precision floating point numbers:
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149 |
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150 | \snippet examples/widgets/spinboxes/window.cpp 14
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151 |
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152 | Before the QDoubleSpinBox widgets are constructed, we create a spin box to
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153 | control how many decimal places they show. By default, only two decimal places
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154 | are shown in the following spin boxes, each of which is the equivalent of a
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155 | spin box in the group created by the \c createSpinBoxes() function.
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156 |
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157 | The first double spin box shows a basic double-precision spin box with the
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158 | same range, step size, and default value as the first spin box in the
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159 | \c createSpinBoxes() function:
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160 |
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161 | \snippet examples/widgets/spinboxes/window.cpp 15
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162 |
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163 | However, this spin box also allows non-integer values to be entered.
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164 |
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165 | The second spin box displays a suffix and shows a special value instead
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166 | of the minimum value:
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167 |
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168 | \snippet examples/widgets/spinboxes/window.cpp 16
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169 |
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170 | The third spin box displays a prefix instead of a suffix:
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171 |
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172 | \snippet examples/widgets/spinboxes/window.cpp 17
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173 |
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174 | We connect the QSpinBox widget that specifies the precision to a slot in
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175 | the \c Window class.
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176 |
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177 | \snippet examples/widgets/spinboxes/window.cpp 18
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178 |
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179 | The rest of the function places each of the widgets into a layout for the
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180 | group box.
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181 |
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182 | The \c changePrecision() slot is called when the user changes the value in
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183 | the precision spin box:
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184 |
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185 | \snippet examples/widgets/spinboxes/window.cpp 19
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186 |
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187 | This function simply uses the integer supplied by the signal to specify the
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188 | number of decimal places in each of the QDoubleSpinBox widgets. Each one
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189 | of these will be updated automatically when their
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190 | \l{QDoubleSpinBox::decimals}{decimals} property is changed.
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191 | */
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