| 1 | /******************************************************************************* |
| 2 | * Copyright (c) 2000, 2007 IBM Corporation and others. |
| 3 | * All rights reserved. This program and the accompanying materials |
| 4 | * are made available under the terms of the Eclipse Public License v1.0 |
| 5 | * which accompanies this distribution, and is available at |
| 6 | * http://www.eclipse.org/legal/epl-v10.html |
| 7 | * |
| 8 | * Contributors: |
| 9 | * IBM Corporation - initial API and implementation |
| 10 | *******************************************************************************/ |
| 11 | package org.eclipse.jface.util; |
| 12 | |
| 13 | import java.util.ArrayList; |
| 14 | import java.util.Iterator; |
| 15 | import java.util.List; |
| 16 | |
| 17 | import org.eclipse.swt.dnd.DND; |
| 18 | import org.eclipse.swt.dnd.DropTargetEvent; |
| 19 | import org.eclipse.swt.dnd.DropTargetListener; |
| 20 | import org.eclipse.swt.dnd.Transfer; |
| 21 | import org.eclipse.swt.dnd.TransferData; |
| 22 | |
| 23 | /** |
| 24 | * A <code>DelegatingDropAdapter</code> is a <code>DropTargetListener</code> that |
| 25 | * maintains and delegates to a set of {@link TransferDropTargetListener}s. Each |
| 26 | * <code>TransferDropTargetListener</code> can then be implemented as if it were |
| 27 | * the DropTarget's only <code>DropTargetListener</code>. |
| 28 | * <p> |
| 29 | * On <code>dragEnter</code>, <code>dragOperationChanged</code>, <code>dragOver</code> |
| 30 | * and <code>drop</code>, a <i>current</i> listener is obtained from the set of all |
| 31 | * <code>TransferDropTargetListeners</code>. The current listener is the first listener |
| 32 | * to return <code>true</code> for |
| 33 | * {@link TransferDropTargetListener#isEnabled(DropTargetEvent)}. |
| 34 | * The current listener is forwarded all <code>DropTargetEvents</code> until some other |
| 35 | * listener becomes the current listener, or the drop terminates. |
| 36 | * </p> |
| 37 | * <p> |
| 38 | * After adding all <code>TransferDropTargetListeners</code> to the |
| 39 | * <code>DelegatingDropAdapter</code> the combined set of <code>Transfers</code> should |
| 40 | * be set in the SWT <code>DropTarget</code>. <code>#getTransfers()</code> provides the |
| 41 | * set of <code>Transfer</code> types of all <code>TransferDropTargetListeners</code>. |
| 42 | * </p> |
| 43 | * <p> |
| 44 | * The following example snippet shows a <code>DelegatingDropAdapter</code> with two |
| 45 | * <code>TransferDropTargetListeners</code>. One supports dropping resources and |
| 46 | * demonstrates how a listener can be disabled in the isEnabled method. |
| 47 | * The other listener supports text transfer. |
| 48 | * </p> |
| 49 | * <code><pre> |
| 50 | * final TreeViewer viewer = new TreeViewer(shell, SWT.NONE); |
| 51 | * DelegatingDropAdapter dropAdapter = new DelegatingDropAdapter(); |
| 52 | * dropAdapter.addDropTargetListener(new TransferDropTargetListener() { |
| 53 | * public Transfer getTransfer() { |
| 54 | * return ResourceTransfer.getInstance(); |
| 55 | * } |
| 56 | * public boolean isEnabled(DropTargetEvent event) { |
| 57 | * // disable drop listener if there is no viewer selection |
| 58 | * if (viewer.getSelection().isEmpty()) |
| 59 | * return false; |
| 60 | * return true; |
| 61 | * } |
| 62 | * public void dragEnter(DropTargetEvent event) {} |
| 63 | * public void dragLeave(DropTargetEvent event) {} |
| 64 | * public void dragOperationChanged(DropTargetEvent event) {} |
| 65 | * public void dragOver(DropTargetEvent event) {} |
| 66 | * public void drop(DropTargetEvent event) { |
| 67 | * if (event.data == null) |
| 68 | * return; |
| 69 | * IResource[] resources = (IResource[]) event.data; |
| 70 | * if (event.detail == DND.DROP_COPY) { |
| 71 | * // copy resources |
| 72 | * } else { |
| 73 | * // move resources |
| 74 | * } |
| 75 | * |
| 76 | * } |
| 77 | * public void dropAccept(DropTargetEvent event) {} |
| 78 | * }); |
| 79 | * dropAdapter.addDropTargetListener(new TransferDropTargetListener() { |
| 80 | * public Transfer getTransfer() { |
| 81 | * return TextTransfer.getInstance(); |
| 82 | * } |
| 83 | * public boolean isEnabled(DropTargetEvent event) { |
| 84 | * return true; |
| 85 | * } |
| 86 | * public void dragEnter(DropTargetEvent event) {} |
| 87 | * public void dragLeave(DropTargetEvent event) {} |
| 88 | * public void dragOperationChanged(DropTargetEvent event) {} |
| 89 | * public void dragOver(DropTargetEvent event) {} |
| 90 | * public void drop(DropTargetEvent event) { |
| 91 | * if (event.data == null) |
| 92 | * return; |
| 93 | * System.out.println(event.data); |
| 94 | * } |
| 95 | * public void dropAccept(DropTargetEvent event) {} |
| 96 | * }); |
| 97 | * viewer.addDropSupport(DND.DROP_COPY | DND.DROP_MOVE, dropAdapter.getTransfers(), dropAdapter); |
| 98 | * </pre></code> |
| 99 | * @since 3.0 |
| 100 | */ |
| 101 | public class DelegatingDropAdapter implements DropTargetListener { |
| 102 | private List listeners = new ArrayList(); |
| 103 | |
| 104 | private TransferDropTargetListener currentListener; |
| 105 | |
| 106 | private int originalDropType; |
| 107 | |
| 108 | /** |
| 109 | * Adds the given <code>TransferDropTargetListener</code>. |
| 110 | * |
| 111 | * @param listener the new listener |
| 112 | */ |
| 113 | public void addDropTargetListener(TransferDropTargetListener listener) { |
| 114 | listeners.add(listener); |
| 115 | } |
| 116 | |
| 117 | /** |
| 118 | * The cursor has entered the drop target boundaries. The current listener is |
| 119 | * updated, and <code>#dragEnter()</code> is forwarded to the current listener. |
| 120 | * |
| 121 | * @param event the drop target event |
| 122 | * @see DropTargetListener#dragEnter(DropTargetEvent) |
| 123 | */ |
| 124 | public void dragEnter(DropTargetEvent event) { |
| 125 | // if (Policy.DEBUG_DRAG_DROP) |
| 126 | // System.out.println("Drag Enter: " + toString()); //$NON-NLS-1$ |
| 127 | originalDropType = event.detail; |
| 128 | updateCurrentListener(event); |
| 129 | } |
| 130 | |
| 131 | /** |
| 132 | * The cursor has left the drop target boundaries. The event is forwarded to the |
| 133 | * current listener. |
| 134 | * |
| 135 | * @param event the drop target event |
| 136 | * @see DropTargetListener#dragLeave(DropTargetEvent) |
| 137 | */ |
| 138 | public void dragLeave(final DropTargetEvent event) { |
| 139 | // if (Policy.DEBUG_DRAG_DROP) |
| 140 | // System.out.println("Drag Leave: " + toString()); //$NON-NLS-1$ |
| 141 | setCurrentListener(null, event); |
| 142 | } |
| 143 | |
| 144 | /** |
| 145 | * The operation being performed has changed (usually due to the user changing |
| 146 | * a drag modifier key while dragging). Updates the current listener and forwards |
| 147 | * this event to that listener. |
| 148 | * |
| 149 | * @param event the drop target event |
| 150 | * @see DropTargetListener#dragOperationChanged(DropTargetEvent) |
| 151 | */ |
| 152 | public void dragOperationChanged(final DropTargetEvent event) { |
| 153 | // if (Policy.DEBUG_DRAG_DROP) |
| 154 | // System.out.println("Drag Operation Changed to: " + event.detail); //$NON-NLS-1$ |
| 155 | originalDropType = event.detail; |
| 156 | TransferDropTargetListener oldListener = getCurrentListener(); |
| 157 | updateCurrentListener(event); |
| 158 | final TransferDropTargetListener newListener = getCurrentListener(); |
| 159 | // only notify the current listener if it hasn't changed based on the |
| 160 | // operation change. otherwise the new listener would get a dragEnter |
| 161 | // followed by a dragOperationChanged with the exact same event. |
| 162 | if (newListener != null && newListener == oldListener) { |
| 163 | SafeRunnable.run(new SafeRunnable() { |
| 164 | public void run() throws Exception { |
| 165 | newListener.dragOperationChanged(event); |
| 166 | } |
| 167 | }); |
| 168 | } |
| 169 | } |
| 170 | |
| 171 | /** |
| 172 | * The cursor is moving over the drop target. Updates the current listener and |
| 173 | * forwards this event to that listener. If no listener can handle the drag |
| 174 | * operation the <code>event.detail</code> field is set to <code>DND.DROP_NONE</code> |
| 175 | * to indicate an invalid drop. |
| 176 | * |
| 177 | * @param event the drop target event |
| 178 | * @see DropTargetListener#dragOver(DropTargetEvent) |
| 179 | */ |
| 180 | public void dragOver(final DropTargetEvent event) { |
| 181 | TransferDropTargetListener oldListener = getCurrentListener(); |
| 182 | updateCurrentListener(event); |
| 183 | final TransferDropTargetListener newListener = getCurrentListener(); |
| 184 | |
| 185 | // only notify the current listener if it hasn't changed based on the |
| 186 | // drag over. otherwise the new listener would get a dragEnter |
| 187 | // followed by a dragOver with the exact same event. |
| 188 | if (newListener != null && newListener == oldListener) { |
| 189 | SafeRunnable.run(new SafeRunnable() { |
| 190 | public void run() throws Exception { |
| 191 | newListener.dragOver(event); |
| 192 | } |
| 193 | }); |
| 194 | } |
| 195 | } |
| 196 | |
| 197 | /** |
| 198 | * Forwards this event to the current listener, if there is one. Sets the |
| 199 | * current listener to <code>null</code> afterwards. |
| 200 | * |
| 201 | * @param event the drop target event |
| 202 | * @see DropTargetListener#drop(DropTargetEvent) |
| 203 | */ |
| 204 | public void drop(final DropTargetEvent event) { |
| 205 | // if (Policy.DEBUG_DRAG_DROP) |
| 206 | // System.out.println("Drop: " + toString()); //$NON-NLS-1$ |
| 207 | updateCurrentListener(event); |
| 208 | if (getCurrentListener() != null) { |
| 209 | SafeRunnable.run(new SafeRunnable() { |
| 210 | public void run() throws Exception { |
| 211 | getCurrentListener().drop(event); |
| 212 | } |
| 213 | }); |
| 214 | } |
| 215 | setCurrentListener(null, event); |
| 216 | } |
| 217 | |
| 218 | /** |
| 219 | * Forwards this event to the current listener if there is one. |
| 220 | * |
| 221 | * @param event the drop target event |
| 222 | * @see DropTargetListener#dropAccept(DropTargetEvent) |
| 223 | */ |
| 224 | public void dropAccept(final DropTargetEvent event) { |
| 225 | // if (Policy.DEBUG_DRAG_DROP) |
| 226 | // System.out.println("Drop Accept: " + toString()); //$NON-NLS-1$ |
| 227 | if (getCurrentListener() != null) { |
| 228 | SafeRunnable.run(new SafeRunnable() { |
| 229 | public void run() throws Exception { |
| 230 | getCurrentListener().dropAccept(event); |
| 231 | } |
| 232 | }); |
| 233 | } |
| 234 | } |
| 235 | |
| 236 | /** |
| 237 | * Returns the listener which currently handles drop events. |
| 238 | * |
| 239 | * @return the <code>TransferDropTargetListener</code> which currently |
| 240 | * handles drop events. |
| 241 | */ |
| 242 | private TransferDropTargetListener getCurrentListener() { |
| 243 | return currentListener; |
| 244 | } |
| 245 | |
| 246 | /** |
| 247 | * Returns the transfer data type supported by the given listener. |
| 248 | * Returns <code>null</code> if the listener does not support any of the |
| 249 | * specified data types. |
| 250 | * |
| 251 | * @param dataTypes available data types |
| 252 | * @param listener <code>TransferDropTargetListener</code> to use for testing |
| 253 | * supported data types. |
| 254 | * @return the transfer data type supported by the given listener or |
| 255 | * <code>null</code>. |
| 256 | */ |
| 257 | private TransferData getSupportedTransferType(TransferData[] dataTypes, |
| 258 | TransferDropTargetListener listener) { |
| 259 | for (int i = 0; i < dataTypes.length; i++) { |
| 260 | if (listener.getTransfer().isSupportedType(dataTypes[i])) { |
| 261 | return dataTypes[i]; |
| 262 | } |
| 263 | } |
| 264 | return null; |
| 265 | } |
| 266 | |
| 267 | /** |
| 268 | * Returns the combined set of <code>Transfer</code> types of all |
| 269 | * <code>TransferDropTargetListeners</code>. |
| 270 | * |
| 271 | * @return the combined set of <code>Transfer</code> types |
| 272 | */ |
| 273 | public Transfer[] getTransfers() { |
| 274 | Transfer[] types = new Transfer[listeners.size()]; |
| 275 | for (int i = 0; i < listeners.size(); i++) { |
| 276 | TransferDropTargetListener listener = (TransferDropTargetListener) listeners |
| 277 | .get(i); |
| 278 | types[i] = listener.getTransfer(); |
| 279 | } |
| 280 | return types; |
| 281 | } |
| 282 | |
| 283 | /** |
| 284 | * Returns <code>true</code> if there are no listeners to delegate events to. |
| 285 | * |
| 286 | * @return <code>true</code> if there are no <code>TransferDropTargetListeners</code> |
| 287 | * <code>false</code> otherwise |
| 288 | */ |
| 289 | public boolean isEmpty() { |
| 290 | return listeners.isEmpty(); |
| 291 | } |
| 292 | |
| 293 | /** |
| 294 | * Removes the given <code>TransferDropTargetListener</code>. |
| 295 | * Listeners should not be removed while a drag and drop operation is in progress. |
| 296 | * |
| 297 | * @param listener the listener to remove |
| 298 | */ |
| 299 | public void removeDropTargetListener(TransferDropTargetListener listener) { |
| 300 | if (currentListener == listener) { |
| 301 | currentListener = null; |
| 302 | } |
| 303 | listeners.remove(listener); |
| 304 | } |
| 305 | |
| 306 | /** |
| 307 | * Sets the current listener to <code>listener</code>. Sends the given |
| 308 | * <code>DropTargetEvent</code> if the current listener changes. |
| 309 | * |
| 310 | * @return <code>true</code> if the new listener is different than the previous |
| 311 | * <code>false</code> otherwise |
| 312 | */ |
| 313 | private boolean setCurrentListener(TransferDropTargetListener listener, |
| 314 | final DropTargetEvent event) { |
| 315 | if (currentListener == listener) { |
| 316 | return false; |
| 317 | } |
| 318 | if (currentListener != null) { |
| 319 | SafeRunnable.run(new SafeRunnable() { |
| 320 | public void run() throws Exception { |
| 321 | currentListener.dragLeave(event); |
| 322 | } |
| 323 | }); |
| 324 | } |
| 325 | currentListener = listener; |
| 326 | // if (Policy.DEBUG_DRAG_DROP) |
| 327 | // System.out.println("Current drop listener: " + listener); //$NON-NLS-1$ |
| 328 | if (currentListener != null) { |
| 329 | SafeRunnable.run(new SafeRunnable() { |
| 330 | public void run() throws Exception { |
| 331 | currentListener.dragEnter(event); |
| 332 | } |
| 333 | }); |
| 334 | } |
| 335 | return true; |
| 336 | } |
| 337 | |
| 338 | /** |
| 339 | * Updates the current listener to one that can handle the drop. There can be many |
| 340 | * listeners and each listener may be able to handle many <code>TransferData</code> |
| 341 | * types. The first listener found that can handle a drop of one of the given |
| 342 | * <code>TransferData</code> types will be selected. |
| 343 | * If no listener can handle the drag operation the <code>event.detail</code> field |
| 344 | * is set to <code>DND.DROP_NONE</code> to indicate an invalid drop. |
| 345 | * |
| 346 | * @param event the drop target event |
| 347 | */ |
| 348 | private void updateCurrentListener(DropTargetEvent event) { |
| 349 | int originalDetail = event.detail; |
| 350 | // revert the detail to the "original" drop type that the User indicated. |
| 351 | // this is necessary because the previous listener may have changed the detail |
| 352 | // to something other than what the user indicated. |
| 353 | event.detail = originalDropType; |
| 354 | |
| 355 | Iterator iter = listeners.iterator(); |
| 356 | while (iter.hasNext()) { |
| 357 | TransferDropTargetListener listener = (TransferDropTargetListener) iter |
| 358 | .next(); |
| 359 | TransferData dataType = getSupportedTransferType(event.dataTypes, |
| 360 | listener); |
| 361 | if (dataType != null) { |
| 362 | TransferData originalDataType = event.currentDataType; |
| 363 | // set the data type supported by the drop listener |
| 364 | event.currentDataType = dataType; |
| 365 | if (listener.isEnabled(event)) { |
| 366 | // if the listener stays the same, set its previously determined |
| 367 | // event detail |
| 368 | if (!setCurrentListener(listener, event)) { |
| 369 | event.detail = originalDetail; |
| 370 | } |
| 371 | return; |
| 372 | } |
| 373 | event.currentDataType = originalDataType; |
| 374 | } |
| 375 | } |
| 376 | setCurrentListener(null, event); |
| 377 | event.detail = DND.DROP_NONE; |
| 378 | |
| 379 | // -always- ensure that expand/scroll are on...otherwise |
| 380 | // if a valid drop target is a child of an invalid one |
| 381 | // you can't get there... |
| 382 | event.feedback = DND.FEEDBACK_EXPAND | DND.FEEDBACK_SCROLL; |
| 383 | } |
| 384 | } |