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

diff --git a/net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDragAdapter.java b/net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDragAdapter.java
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+++ b/net.sourceforge.phpeclipse/src/net/sourceforge/phpdt/internal/ui/dnd/DelegatingDragAdapter.java
@@ -0,0 +1,115 @@
+/*******************************************************************************
+ * Copyright (c) 2000, 2003 IBM Corporation and others.
+ * All rights reserved. This program and the accompanying materials 
+ * are made available under the terms of the Common Public License v1.0
+ * which accompanies this distribution, and is available at
+ * http://www.eclipse.org/legal/cpl-v10.html
+ * 
+ * Contributors:
+ *     IBM Corporation - initial API and implementation
+ *******************************************************************************/
+package net.sourceforge.phpdt.internal.ui.dnd;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+
+import org.eclipse.swt.dnd.DragSource;
+import org.eclipse.swt.dnd.DragSourceEvent;
+import org.eclipse.swt.dnd.DragSourceListener;
+import org.eclipse.swt.dnd.Transfer;
+import org.eclipse.swt.dnd.TransferData;
+
+import org.eclipse.jface.util.Assert;
+
+/**
+ * A delegating drag adapter negotiates between a set of <code>TransferDragSourceListener</code>s
+ * On <code>dragStart</code> the adapter determines the listener to be used for any further
+ * <code>drag*</code> callback.
+ */
+public class DelegatingDragAdapter implements DragSourceListener {
+
+       private TransferDragSourceListener[] fPossibleListeners;
+       private List fActiveListeners;
+       private TransferDragSourceListener fFinishListener;
+       
+       public DelegatingDragAdapter(TransferDragSourceListener[] listeners) {
+               setPossibleListeners(listeners);
+       }
+       
+       protected void setPossibleListeners(TransferDragSourceListener[] listeners) {
+               Assert.isNotNull(listeners);
+               Assert.isTrue(fActiveListeners == null, "Can only set possible listeners before drag operation has started"); //$NON-NLS-1$
+               fPossibleListeners= listeners;
+       }
+       
+       /* non Java-doc
+        * @see DragSourceListener
+        */
+       public void dragStart(DragSourceEvent event) {
+               fFinishListener= null;
+               boolean saveDoit= event.doit;
+               Object saveData= event.data;
+               boolean doIt= false;
+               List transfers= new ArrayList(fPossibleListeners.length);
+               fActiveListeners= new ArrayList(fPossibleListeners.length);
+               
+               for (int i= 0; i < fPossibleListeners.length; i++) {
+                       TransferDragSourceListener listener= fPossibleListeners[i];
+                       event.doit= saveDoit;
+                       listener.dragStart(event);
+                       if (event.doit) {
+                               transfers.add(listener.getTransfer());
+                               fActiveListeners.add(listener);
+                       }
+                       doIt= doIt || event.doit;
+               }
+               if (doIt) {
+                       ((DragSource)event.widget).setTransfer((Transfer[])transfers.toArray(new Transfer[transfers.size()]));
+               }
+               event.data= saveData;
+               event.doit= doIt;
+       }
+
+       /* non Java-doc
+        * @see DragSourceListener
+        */
+       public void dragSetData(DragSourceEvent event) {
+               fFinishListener= getListener(event.dataType);
+               if (fFinishListener != null)
+                       fFinishListener.dragSetData(event);
+       }
+       
+       /* non Java-doc
+        * @see DragSourceListener
+        */
+       public void dragFinished(DragSourceEvent event) {
+               try{
+                       if (fFinishListener != null) {
+                               fFinishListener.dragFinished(event);
+                       } else {
+                               // If the user presses Escape then we get a dragFinished without
+                               // getting a dragSetData before.
+                               fFinishListener= getListener(event.dataType);
+                               if (fFinishListener != null)
+                                       fFinishListener.dragFinished(event);
+                       }
+               } finally{
+                       fFinishListener= null;
+                       fActiveListeners= null;
+               }       
+       }
+       
+       private TransferDragSourceListener getListener(TransferData type) {
+               if (type == null)
+                       return null;
+                       
+               for (Iterator iter= fActiveListeners.iterator(); iter.hasNext();) {
+                       TransferDragSourceListener listener= (TransferDragSourceListener)iter.next();
+                       if (listener.getTransfer().isSupportedType(type)) {
+                               return listener;
+                       }
+               }
+               return null;
+       }       
+}