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.swt.dnd.DragSource;
  18 import org.eclipse.swt.dnd.DragSourceEvent;
  19 import org.eclipse.swt.dnd.DragSourceListener;
  20 import org.eclipse.swt.dnd.Transfer;
  21 import org.eclipse.swt.dnd.TransferData;
  22
  23 import org.eclipse.jface.util.Assert;
  24
  25 /**
  26  * A delegating drag adapter negotiates between a set of <code>TransferDragSourceListener</code>s
  27  * On <code>dragStart</code> the adapter determines the listener to be used for any further
  28  * <code>drag*</code> callback.
  29  */
  30 public class DelegatingDragAdapter implements DragSourceListener {
  31
  32         private TransferDragSourceListener[] fPossibleListeners;
  33         private List fActiveListeners;
  34         private TransferDragSourceListener fFinishListener;
  35
  36         public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
  37                 setPossibleListeners(listeners);
  38         }
  39
  40         protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
  41                 Assert.isNotNull(listeners);
  42                 Assert.isTrue(fActiveListeners == null, "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
  43                 fPossibleListeners= listeners;
  44         }
  45
  46         /* non Java-doc
  47          * @see DragSourceListener
  48          */
  49         public void dragStart(DragSourceEvent event) {
  50                 fFinishListener= null;
  51                 boolean saveDoit= event.doit;
  52                 Object saveData= event.data;
  53                 boolean doIt= false;
  54                 List transfers= new ArrayList(fPossibleListeners.length);
  55                 fActiveListeners= new ArrayList(fPossibleListeners.length);
  56
  57                 for (int i= 0; i < fPossibleListeners.length; i++) {
  58                         TransferDragSourceListener listener= fPossibleListeners[i];
  59                         event.doit= saveDoit;
  60                         listener.dragStart(event);
  61                         if (event.doit) {
  62                                 transfers.add(listener.getTransfer());
  63                                 fActiveListeners.add(listener);
  64                         }
  65                         doIt= doIt || event.doit;
  66                 }
  67                 if (doIt) {
  68                         ((DragSource)event.widget).setTransfer((Transfer[])transfers.toArray(new Transfer[transfers.size()]));
  69                 }
  70                 event.data= saveData;
  71                 event.doit= doIt;
  72         }
  73
  74         /* non Java-doc
  75          * @see DragSourceListener
  76          */
  77         public void dragSetData(DragSourceEvent event) {
  78                 fFinishListener= getListener(event.dataType);
  79                 if (fFinishListener != null)
  80                         fFinishListener.dragSetData(event);
  81         }
  82
  83         /* non Java-doc
  84          * @see DragSourceListener
  85          */
  86         public void dragFinished(DragSourceEvent event) {
  87                 try{
  88                         if (fFinishListener != null) {
  89                                 fFinishListener.dragFinished(event);
  90                         } else {
  91                                 // If the user presses Escape then we get a dragFinished without
  92                                 // getting a dragSetData before.
  93                                 fFinishListener= getListener(event.dataType);
  94                                 if (fFinishListener != null)
  95                                         fFinishListener.dragFinished(event);
  96                         }
  97                 } finally{
  98                         fFinishListener= null;
  99                         fActiveListeners= null;
 100                 }
 101         }
 102
 103         private TransferDragSourceListener getListener(TransferData type) {
 104                 if (type == null)
 105                         return null;
 106
 107                 for (Iterator iter= fActiveListeners.iterator(); iter.hasNext();) {
 108                         TransferDragSourceListener listener= (TransferDragSourceListener)iter.next();
 109                         if (listener.getTransfer().isSupportedType(type)) {
 110                                 return listener;
 111                         }
 112                 }
 113                 return null;
 114         }
 115 }