net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDragAdapter.java

   1 /*******************************************************************************
   2  * Copyright (c) 2000, 2003 IBM Corporation and others.
   3  * All rights reserved. This program and the accompanying materials
   4  * are made available under the terms of the Common Public License v1.0
   5  * which accompanies this distribution, and is available at
   6  * http://www.eclipse.org/legal/cpl-v10.html
   7  *
   8  * Contributors:
   9  *     IBM Corporation - initial API and implementation
  10  *******************************************************************************/
  11 package net.sourceforge.phpdt.internal.ui.dnd;
  12
  13 import java.util.ArrayList;
  14 import java.util.Iterator;
  15 import java.util.List;
  16
  17 import org.eclipse.jface.util.Assert;
  18 import org.eclipse.swt.dnd.DragSource;
  19 import org.eclipse.swt.dnd.DragSourceEvent;
  20 import org.eclipse.swt.dnd.DragSourceListener;
  21 import org.eclipse.swt.dnd.Transfer;
  22 import org.eclipse.swt.dnd.TransferData;
  23
  24 /**
  25  * A delegating drag adapter negotiates between a set of
  26  * <code>TransferDragSourceListener</code>s On <code>dragStart</code> the
  27  * adapter determines the listener to be used for any further <code>drag*</code>
  28  * callback.
  29  */
  30 public class DelegatingDragAdapter implements DragSourceListener {
  31
  32         private TransferDragSourceListener[] fPossibleListeners;
  33
  34         private List fActiveListeners;
  35
  36         private TransferDragSourceListener fFinishListener;
  37
  38         public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
  39                 setPossibleListeners(listeners);
  40         }
  41
  42         protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
  43                 Assert.isNotNull(listeners);
  44                 Assert
  45                                 .isTrue(fActiveListeners == null,
  46                                                 "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
  47                 fPossibleListeners = listeners;
  48         }
  49
  50         /*
  51          * non Java-doc
  52          *
  53          * @see DragSourceListener
  54          */
  55         public void dragStart(DragSourceEvent event) {
  56                 fFinishListener = null;
  57                 boolean saveDoit = event.doit;
  58                 Object saveData = event.data;
  59                 boolean doIt = false;
  60                 List transfers = new ArrayList(fPossibleListeners.length);
  61                 fActiveListeners = new ArrayList(fPossibleListeners.length);
  62
  63                 for (int i = 0; i < fPossibleListeners.length; i++) {
  64                         TransferDragSourceListener listener = fPossibleListeners[i];
  65                         event.doit = saveDoit;
  66                         listener.dragStart(event);
  67                         if (event.doit) {
  68                                 transfers.add(listener.getTransfer());
  69                                 fActiveListeners.add(listener);
  70                         }
  71                         doIt = doIt || event.doit;
  72                 }
  73                 if (doIt) {
  74                         ((DragSource) event.widget).setTransfer((Transfer[]) transfers
  75                                         .toArray(new Transfer[transfers.size()]));
  76                 }
  77                 event.data = saveData;
  78                 event.doit = doIt;
  79         }
  80
  81         /*
  82          * non Java-doc
  83          *
  84          * @see DragSourceListener
  85          */
  86         public void dragSetData(DragSourceEvent event) {
  87                 fFinishListener = getListener(event.dataType);
  88                 if (fFinishListener != null)
  89                         fFinishListener.dragSetData(event);
  90         }
  91
  92         /*
  93          * non Java-doc
  94          *
  95          * @see DragSourceListener
  96          */
  97         public void dragFinished(DragSourceEvent event) {
  98                 try {
  99                         if (fFinishListener != null) {
 100                                 fFinishListener.dragFinished(event);
 101                         } else {
 102                                 // If the user presses Escape then we get a dragFinished without
 103                                 // getting a dragSetData before.
 104                                 fFinishListener = getListener(event.dataType);
 105                                 if (fFinishListener != null)
 106                                         fFinishListener.dragFinished(event);
 107                         }
 108                 } finally {
 109                         fFinishListener = null;
 110                         fActiveListeners = null;
 111                 }
 112         }
 113
 114         private TransferDragSourceListener getListener(TransferData type) {
 115                 if (type == null)
 116                         return null;
 117
 118                 for (Iterator iter = fActiveListeners.iterator(); iter.hasNext();) {
 119                         TransferDragSourceListener listener = (TransferDragSourceListener) iter
 120                                         .next();
 121                         if (listener.getTransfer().isSupportedType(type)) {
 122                                 return listener;
 123                         }
 124                 }
 125                 return null;
 126         }
 127 }