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 <code>TransferDragSourceListener</code>s
  26  * On <code>dragStart</code> the adapter determines the listener to be used for any further
  27  * <code>drag*</code> callback.
  28  */
  29 public class DelegatingDragAdapter implements DragSourceListener {
  30
  31         private TransferDragSourceListener[] fPossibleListeners;
  32         private List fActiveListeners;
  33         private TransferDragSourceListener fFinishListener;
  34
  35         public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
  36                 setPossibleListeners(listeners);
  37         }
  38
  39         protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
  40                 Assert.isNotNull(listeners);
  41                 Assert.isTrue(fActiveListeners == null, "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
  42                 fPossibleListeners= listeners;
  43         }
  44
  45         /* non Java-doc
  46          * @see DragSourceListener
  47          */
  48         public void dragStart(DragSourceEvent event) {
  49                 fFinishListener= null;
  50                 boolean saveDoit= event.doit;
  51                 Object saveData= event.data;
  52                 boolean doIt= false;
  53                 List transfers= new ArrayList(fPossibleListeners.length);
  54                 fActiveListeners= new ArrayList(fPossibleListeners.length);
  55
  56                 for (int i= 0; i < fPossibleListeners.length; i++) {
  57                         TransferDragSourceListener listener= fPossibleListeners[i];
  58                         event.doit= saveDoit;
  59                         listener.dragStart(event);
  60                         if (event.doit) {
  61                                 transfers.add(listener.getTransfer());
  62                                 fActiveListeners.add(listener);
  63                         }
  64                         doIt= doIt || event.doit;
  65                 }
  66                 if (doIt) {
  67                         ((DragSource)event.widget).setTransfer((Transfer[])transfers.toArray(new Transfer[transfers.size()]));
  68                 }
  69                 event.data= saveData;
  70                 event.doit= doIt;
  71         }
  72
  73         /* non Java-doc
  74          * @see DragSourceListener
  75          */
  76         public void dragSetData(DragSourceEvent event) {
  77                 fFinishListener= getListener(event.dataType);
  78                 if (fFinishListener != null)
  79                         fFinishListener.dragSetData(event);
  80         }
  81
  82         /* non Java-doc
  83          * @see DragSourceListener
  84          */
  85         public void dragFinished(DragSourceEvent event) {
  86                 try{
  87                         if (fFinishListener != null) {
  88                                 fFinishListener.dragFinished(event);
  89                         } else {
  90                                 // If the user presses Escape then we get a dragFinished without
  91                                 // getting a dragSetData before.
  92                                 fFinishListener= getListener(event.dataType);
  93                                 if (fFinishListener != null)
  94                                         fFinishListener.dragFinished(event);
  95                         }
  96                 } finally{
  97                         fFinishListener= null;
  98                         fActiveListeners= null;
  99                 }
 100         }
 101
 102         private TransferDragSourceListener getListener(TransferData type) {
 103                 if (type == null)
 104                         return null;
 105
 106                 for (Iterator iter= fActiveListeners.iterator(); iter.hasNext();) {
 107                         TransferDragSourceListener listener= (TransferDragSourceListener)iter.next();
 108                         if (listener.getTransfer().isSupportedType(type)) {
 109                                 return listener;
 110                         }
 111                 }
 112                 return null;
 113         }
 114 }