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 //incastrix
  18 //import org.eclipse.jface.text.Assert;
  19 import org.eclipse.core.runtime.Assert;
  20 import org.eclipse.swt.dnd.DragSource;
  21 import org.eclipse.swt.dnd.DragSourceEvent;
  22 import org.eclipse.swt.dnd.DragSourceListener;
  23 import org.eclipse.swt.dnd.Transfer;
  24 import org.eclipse.swt.dnd.TransferData;
  25
  26 /**
  27  * A delegating drag adapter negotiates between a set of
  28  * <code>TransferDragSourceListener</code>s On <code>dragStart</code> the
  29  * adapter determines the listener to be used for any further <code>drag*</code>
  30  * callback.
  31  */
  32 public class DelegatingDragAdapter implements DragSourceListener {
  33
  34         private TransferDragSourceListener[] fPossibleListeners;
  35
  36         private List fActiveListeners;
  37
  38         private TransferDragSourceListener fFinishListener;
  39
  40         public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
  41                 setPossibleListeners(listeners);
  42         }
  43
  44         protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
  45                 Assert.isNotNull(listeners);
  46                 Assert
  47                                 .isTrue(fActiveListeners == null,
  48                                                 "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
  49                 fPossibleListeners = listeners;
  50         }
  51
  52         /*
  53          * non Java-doc
  54          *
  55          * @see DragSourceListener
  56          */
  57         public void dragStart(DragSourceEvent event) {
  58                 fFinishListener = null;
  59                 boolean saveDoit = event.doit;
  60                 Object saveData = event.data;
  61                 boolean doIt = false;
  62                 List transfers = new ArrayList(fPossibleListeners.length);
  63                 fActiveListeners = new ArrayList(fPossibleListeners.length);
  64
  65                 for (int i = 0; i < fPossibleListeners.length; i++) {
  66                         TransferDragSourceListener listener = fPossibleListeners[i];
  67                         event.doit = saveDoit;
  68                         listener.dragStart(event);
  69                         if (event.doit) {
  70                                 transfers.add(listener.getTransfer());
  71                                 fActiveListeners.add(listener);
  72                         }
  73                         doIt = doIt || event.doit;
  74                 }
  75                 if (doIt) {
  76                         ((DragSource) event.widget).setTransfer((Transfer[]) transfers
  77                                         .toArray(new Transfer[transfers.size()]));
  78                 }
  79                 event.data = saveData;
  80                 event.doit = doIt;
  81         }
  82
  83         /*
  84          * non Java-doc
  85          *
  86          * @see DragSourceListener
  87          */
  88         public void dragSetData(DragSourceEvent event) {
  89                 fFinishListener = getListener(event.dataType);
  90                 if (fFinishListener != null)
  91                         fFinishListener.dragSetData(event);
  92         }
  93
  94         /*
  95          * non Java-doc
  96          *
  97          * @see DragSourceListener
  98          */
  99         public void dragFinished(DragSourceEvent event) {
 100                 try {
 101                         if (fFinishListener != null) {
 102                                 fFinishListener.dragFinished(event);
 103                         } else {
 104                                 // If the user presses Escape then we get a dragFinished without
 105                                 // getting a dragSetData before.
 106                                 fFinishListener = getListener(event.dataType);
 107                                 if (fFinishListener != null)
 108                                         fFinishListener.dragFinished(event);
 109                         }
 110                 } finally {
 111                         fFinishListener = null;
 112                         fActiveListeners = null;
 113                 }
 114         }
 115
 116         private TransferDragSourceListener getListener(TransferData type) {
 117                 if (type == null)
 118                         return null;
 119
 120                 for (Iterator iter = fActiveListeners.iterator(); iter.hasNext();) {
 121                         TransferDragSourceListener listener = (TransferDragSourceListener) iter
 122                                         .next();
 123                         if (listener.getTransfer().isSupportedType(type)) {
 124                                 return listener;
 125                         }
 126                 }
 127                 return null;
 128         }
 129 }