/*******************************************************************************
 * Copyright (c) 2007, 2009 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.dnd;

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.internal.cocoa.*;
import org.eclipse.swt.widgets.*;

/**
 * This class provides default implementations to display a source image
 * when a drag is initiated from a <code>Tree</code>.
 * 
 * <p>Classes that wish to provide their own source image for a <code>Tree</code> can
 * extend <code>TreeDragSourceEffect</code> class and override the <code>TreeDragSourceEffect.dragStart</code>
 * method and set the field <code>DragSourceEvent.image</code> with their own image.</p>
 *
 * Subclasses that override any methods of this class must call the corresponding
 * <code>super</code> method to get the default drag under effect implementation.
 *
 * @see DragSourceEffect
 * @see DragSourceEvent
 * @see <a href="http://www.eclipse.org/swt/">Sample code and further information</a>
 * 
 * @since 3.3
 */
public class TreeDragSourceEffect extends DragSourceEffect {
	Image dragSourceImage = null;

	/**
	 * Creates a new <code>TreeDragSourceEffect</code> to handle drag effect 
	 * from the specified <code>Tree</code>.
	 *
	 * @param tree the <code>Tree</code> that the user clicks on to initiate the drag
	 */
	public TreeDragSourceEffect(Tree tree) {
		super(tree);
	}

	/**
	 * This implementation of <code>dragFinished</code> disposes the image
	 * that was created in <code>TreeDragSourceEffect.dragStart</code>.
	 * 
	 * Subclasses that override this method should call <code>super.dragFinished(event)</code>
	 * to dispose the image in the default implementation.
	 * 
	 * @param event the information associated with the drag finished event
	 */
	public void dragFinished(DragSourceEvent event) {
		if (dragSourceImage != null) dragSourceImage.dispose();
		dragSourceImage = null;
	}

	/**
	 * This implementation of <code>dragStart</code> will create a default
	 * image that will be used during the drag. The image should be disposed
	 * when the drag is completed in the <code>TreeDragSourceEffect.dragFinished</code>
	 * method.
	 * 
	 * Subclasses that override this method should call <code>super.dragStart(event)</code>
	 * to use the image from the default implementation.
	 * 
	 * @param event the information associated with the drag start event
	 */
	public void dragStart(DragSourceEvent event) {
		event.image = getDragSourceImage(event);
	}

	Image getDragSourceImage(DragSourceEvent event) {
		if (dragSourceImage != null) dragSourceImage.dispose();
		dragSourceImage = null;		
		NSPoint point = new NSPoint();
		int /*long*/ ptr = OS.malloc(NSPoint.sizeof);
		OS.memmove(ptr, point, NSPoint.sizeof);
		NSEvent nsEvent = NSApplication.sharedApplication().currentEvent();
		NSTableView widget = (NSTableView)control.view;
		NSImage nsImage = widget.dragImageForRowsWithIndexes(widget.selectedRowIndexes(), widget.tableColumns(), nsEvent, ptr);
		OS.memmove(point, ptr, NSPoint.sizeof);
		OS.free(ptr);
		//TODO: Image representation wrong???
		Image image = Image.cocoa_new(control.getDisplay(), SWT.BITMAP, nsImage);
		dragSourceImage = image;
		nsImage.retain();
		event.offsetX = (int)point.x;
		event.offsetY = (int)point.y;
		return image;
	}
}