net.sourceforge.phpeclipse.ui/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDropAdapter.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 //incastrix
  14 //import org.eclipse.jface.text.Assert;
  15 import org.eclipse.core.runtime.Assert;
  16 import org.eclipse.swt.dnd.DropTargetEvent;
  17 import org.eclipse.swt.dnd.DropTargetListener;
  18 import org.eclipse.swt.dnd.TransferData;
  19
  20 /**
  21  * A delegating drop adapter negotiates between a set of
  22  * <code>TransferDropTargetListener</code>s On <code>dragEnter</code> the
  23  * adapter determines the listener to be used for any further <code>drag*</code>
  24  * callback.
  25  */
  26 public class DelegatingDropAdapter implements DropTargetListener {
  27
  28         private TransferDropTargetListener[] fListeners;
  29
  30         private TransferDropTargetListener fChosenListener;
  31
  32         /**
  33          * Creates a new delegating drop adapter.
  34          *
  35          * @param listeners
  36          *            an array of potential listeners
  37          */
  38         public DelegatingDropAdapter(TransferDropTargetListener[] listeners) {
  39                 fListeners = listeners;
  40                 Assert.isNotNull(listeners);
  41         }
  42
  43         /*
  44          * non Java-doc
  45          *
  46          * @see DropTargetListener
  47          */
  48         public void dragEnter(DropTargetEvent event) {
  49                 fChosenListener = null;
  50                 event.currentDataType = selectPreferredListener(event.dataTypes);
  51                 if (fChosenListener != null)
  52                         fChosenListener.dragEnter(event);
  53         }
  54
  55         /*
  56          * non Java-doc
  57          *
  58          * @see DropTargetListener
  59          */
  60         public void dragLeave(DropTargetEvent event) {
  61                 if (fChosenListener != null)
  62                         fChosenListener.dragLeave(event);
  63         }
  64
  65         /*
  66          * non Java-doc
  67          *
  68          * @see DropTargetListener
  69          */
  70         public void dragOperationChanged(DropTargetEvent event) {
  71                 if (fChosenListener != null)
  72                         fChosenListener.dragOperationChanged(event);
  73         }
  74
  75         /*
  76          * non Java-doc
  77          *
  78          * @see DropTargetListener
  79          */
  80         public void dragOver(DropTargetEvent event) {
  81                 if (fChosenListener != null)
  82                         fChosenListener.dragOver(event);
  83         }
  84
  85         /*
  86          * non Java-doc
  87          *
  88          * @see DropTargetListener
  89          */
  90         public void drop(DropTargetEvent event) {
  91                 if (fChosenListener != null)
  92                         fChosenListener.drop(event);
  93                 fChosenListener = null;
  94         }
  95
  96         /*
  97          * non Java-doc
  98          *
  99          * @see DropTargetListener
 100          */
 101         public void dropAccept(DropTargetEvent event) {
 102                 if (fChosenListener != null)
 103                         fChosenListener.dropAccept(event);
 104         }
 105
 106         private TransferData selectPreferredListener(TransferData[] dataTypes) {
 107                 for (int i = 0; i < fListeners.length; i++) {
 108                         TransferData data = computeTransferData(dataTypes, fListeners[i]);
 109                         if (data != null)
 110                                 return data;
 111                 }
 112                 return null;
 113         }
 114
 115         private TransferData computeTransferData(TransferData[] dataTypes,
 116                         TransferDropTargetListener listener) {
 117                 for (int i = 0; i < dataTypes.length; i++) {
 118                         if (listener.getTransfer().isSupportedType(dataTypes[i])) {
 119                                 fChosenListener = listener;
 120                                 return dataTypes[i];
 121                         }
 122                 }
 123                 return null;
 124         }
 125 }