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1 /*******************************************************************************
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2 * Copyright (c) 2000, 2003 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwt.dnd.DropTargetListener;
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14
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15 import dwt.dwthelper.utils;
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16
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17 import dwt.internal.DWTEventListener;
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18 import dwt.dnd.DropTargetEvent;
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19
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20 /**
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21 * The <code>DropTargetListener</code> class provides event notification to the application
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22 * for DropTarget events.
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23 *
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24 * <p>As the user moves the cursor into, over and out of a Control that has been designated
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25 * as a DropTarget, events indicate what operation can be performed and what data can be
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26 * transferred if a drop where to occur at that point.
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27 * The application can respond to these events and change the type of data that will
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28 * be dropped by modifying event.currentDataType, or change the operation that will be performed
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29 * by modifying the event.detail field or stop any drop from happening on the current target
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30 * by setting the event.detail field to DND_DROP_NONE.</p>
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31 *
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32 * <p>When the user causes a drop to happen by releasing the mouse over a valid drop target,
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33 * the application has one last chance to change the data type of the drop through the
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34 * DropAccept event. If the drop is still allowed, the DropAccept event is immediately
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35 * followed by the Drop event. In the Drop event, the application can still change the
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36 * operation that is performed but the data type is fixed.</p>
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37 *
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38 * @see DropTargetEvent
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39 *
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40 */
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41 public interface DropTargetListener : DWTEventListener {
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42
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43 /**
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44 * The cursor has entered the drop target boundaries.
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45 *
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46 * <p>The following fields in the DropTargetEvent apply:
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47 * <ul>
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48 * <li>(in)widget
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49 * <li>(in)time
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50 * <li>(in)x
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51 * <li>(in)y
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52 * <li>(in)dataTypes
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53 * <li>(in,out)currentDataType
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54 * <li>(in)operations
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55 * <li>(in,out)detail
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56 * <li>(in,out)feedback
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57 * </ul></p>
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58 *
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59 * <p>The <code>operation</code> value is determined by the modifier keys pressed by the user.
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60 * If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT.
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61 * If the application does not set the <code>event.detail</code> to something other
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62 * than <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard
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63 * default.</p>
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64 *
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65 * <p>The <code>currentDataType</code> is determined by the first transfer agent specified in
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66 * setTransfer() that matches a data type provided by the drag source.</p>
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67 *
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68 * <p>It is possible to get a DragEnter event when the drag source does not provide any matching data.
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69 * In this case, the default operation is DND.DROP_NONE and the currentDataType is null.</p>
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70 *
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71 * <p>The application can change the operation that will be performed by modifying the
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72 * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>
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73 * field or DND.DROP_NONE.</p>
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74 *
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75 * <p>The application can also change the type of data being requested by
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76 * modifying the <code>currentDataTypes</code> field but the value must be one of the values
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77 * in the <code>dataTypes</code> list.</p>
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78 *
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79 * @param event the information associated with the drag enter event
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80 *
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81 * @see DropTargetEvent
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82 */
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83 public void dragEnter(DropTargetEvent event);
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84
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85 /**
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86 * The cursor has left the drop target boundaries OR the drop has been cancelled OR the data
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87 * is about to be dropped.
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88 *
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89 * <p>The following fields in the DropTargetEvent apply:
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90 * <ul>
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91 * <li>(in)widget
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92 * <li>(in)time
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93 * <li>(in)x
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94 * <li>(in)y
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95 * <li>(in)dataTypes
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96 * <li>(in)currentDataType
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97 * <li>(in)operations
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98 * <li>(in)detail
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99 * </ul></p>
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100 *
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101 * @param event the information associated with the drag leave event
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102 *
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103 * @see DropTargetEvent
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104 */
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105 public void dragLeave(DropTargetEvent event);
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106
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107 /**
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108 * The operation being performed has changed (usually due to the user changing the selected modifier key(s)
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109 * while dragging).
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110 *
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111 * <p>The following fields in the DropTargetEvent apply:
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112 * <ul>
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113 * <li>(in)widget
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114 * <li>(in)time
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115 * <li>(in)x
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116 * <li>(in)y
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117 * <li>(in)dataTypes
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118 * <li>(in,out)currentDataType
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119 * <li>(in)operations
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120 * <li>(in,out)detail
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121 * <li>(in,out)feedback
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122 * </ul></p>
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123 *
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124 * <p>The <code>operation</code> value is determined by the modifier keys pressed by the user.
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125 * If no keys are pressed the <code>event.detail</code> field is set to DND.DROP_DEFAULT.
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126 * If the application does not set the <code>event.detail</code> to something other than
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127 * <code>DND.DROP_DEFAULT</code> the operation will be set to the platform defined standard default.</p>
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128 *
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129 * <p>The <code>currentDataType</code> value is determined by the value assigned to
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130 * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p>
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131 *
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132 * <p>The application can change the operation that will be performed by modifying the
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133 * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>
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134 * field.</p>
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135 *
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136 * <p>The application can also change the type of data being requested by modifying
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137 * the <code>currentDataTypes</code> field but the value must be one of the values in the
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138 * <code>dataTypes</code> list.</p>
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139 *
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140 * @param event the information associated with the drag operation changed event
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141 *
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142 * @see DropTargetEvent
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143 */
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144 public void dragOperationChanged(DropTargetEvent event);
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145
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146 /**
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147 * The cursor is moving over the drop target.
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148 *
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149 * <p>The following fields in the DropTargetEvent apply:
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150 * <ul>
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151 * <li>(in)widget
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152 * <li>(in)time
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153 * <li>(in)x
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154 * <li>(in)y
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155 * <li>(in)dataTypes
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156 * <li>(in,out)currentDataType
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157 * <li>(in)operations
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158 * <li>(in,out)detail
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159 * <li>(in,out)feedback
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160 * </ul></p>
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161 *
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162 * <p>The <code>operation</code> value is determined by the value assigned to
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163 * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p>
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164 *
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165 * <p>The <code>currentDataType</code> value is determined by the value assigned to
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166 * <code>currentDataType</code> in previous dragEnter and dragOver calls.</p>
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167 *
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168 * <p>The application can change the operation that will be performed by modifying the
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169 * <code>detail</code> field but the choice must be one of the values in the <code>operations</code>
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170 * field.</p>
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171 *
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172 * <p>The application can also change the type of data being requested by modifying the
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173 * <code>currentDataTypes</code> field but the value must be one of the values in the
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174 * <code>dataTypes</code> list.</p>
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175 *
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176 * <p>NOTE: At this point the <code>data</code> field is null. On some platforms, it is possible
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177 * to obtain the data being transferred before the transfer occurs but in most platforms this is
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178 * not possible. On those platforms where the data is available, the application can access the
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179 * data as follows:</p>
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180 *
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181 * <pre><code>
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182 * public void dragOver(DropTargetEvent event) {
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183 * TextTransfer textTransfer = TextTransfer.getInstance();
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184 * String data = (String)textTransfer.nativeToJava(event.currentDataType);
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185 * if (data !is null) {
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186 * System.out.println("Data to be dropped is (Text)"+data);
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187 * }
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188 * };
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189 * </code></pre>
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190 *
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191 * @param event the information associated with the drag over event
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192 *
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193 * @see DropTargetEvent
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194 */
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195 public void dragOver(DropTargetEvent event);
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196
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197 /**
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198 * The data is being dropped. The data field contains java format of the data being dropped.
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199 * To determine the type of the data object, refer to the documentation for the Transfer subclass
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200 * specified in event.currentDataType.
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201 *
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202 * <p>The following fields in DropTargetEvent apply:
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203 * <ul>
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204 * <li>(in)widget
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205 * <li>(in)time
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206 * <li>(in)x
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207 * <li>(in)y
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208 * <li>(in,out)detail
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209 * <li>(in)currentDataType
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210 * <li>(in)data
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211 * </ul></p>
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212 *
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213 * <p>The application can refuse to perform the drop operation by setting the detail
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214 * field to DND.DROP_NONE.</p>
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215 *
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216 * @param event the information associated with the drop event
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217 *
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218 * @see DropTargetEvent
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219 */
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220 public void drop(DropTargetEvent event);
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221
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222 /**
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223 * The drop is about to be performed.
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224 * The drop target is given a last chance to change the nature of the drop.
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225 *
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226 * <p>The following fields in the DropTargetEvent apply:
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227 * <ul>
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228 * <li>(in)widget
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229 * <li>(in)time
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230 * <li>(in)x
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231 * <li>(in)y
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232 * <li>(in)dataTypes
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233 * <li>(in,out)currentDataType
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234 * <li>(in)operations
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235 * <li>(in,out)detail
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236 * </ul></p>
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237 *
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238 * <p>The application can veto the drop by setting the <code>event.detail</code> field to
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239 * <code>DND.DROP_NONE</code>.</p>
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240 *
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241 * <p>The application can change the operation that will be performed by modifying the
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242 * <code>detail</code> field but the choice must be one of the values in the
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243 * <code>operations</code> field.</p>
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244 *
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245 * <p>The application can also change the type of data being requested by modifying the
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246 * <code>currentDataTypes</code> field but the value must be one of the values in the <
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247 * code>dataTypes</code> list.</p>
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248 *
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249 * @param event the information associated with the drop accept event
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250 *
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251 * @see DropTargetEvent
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252 */
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253 public void dropAccept(DropTargetEvent event);
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254
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255 }
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