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SWT is an open source widget toolkit for Java designed to provide efficient, portable access to the user-interface facilities of the operating systems on which it is implemented.
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/*******************************************************************************
 * Copyright (c) 2000, 2013 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.cairo.Cairo;
import org.eclipse.swt.internal.gtk.*;
import org.eclipse.swt.widgets.*;

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

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

	/**
	 * This implementation of dragFinished disposes the image
	 * that was created in TreeDragSourceEffect.dragStart.
	 * 
	 * Subclasses that override this method should call super.dragFinished(event)
	 * 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 dragStart will create a default
	 * image that will be used during the drag. The image should be disposed
	 * when the drag is completed in the TreeDragSourceEffect.dragFinished
	 * method.
	 * 
	 * Subclasses that override this method should call super.dragStart(event)
	 * 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;

		Tree tree = (Tree) control;
		//TEMPORARY CODE
		if (tree.isListening(SWT.EraseItem) || tree.isListening (SWT.PaintItem)) return null;

		/*
		 * Bug in GTK.  gtk_tree_selection_get_selected_rows() segmentation faults
		 * in versions smaller than 2.2.4 if the model is NULL.  The fix is
		 * to give a valid pointer instead.
		 */
		int /*long*/ handle = tree.handle;
		int /*long*/ selection = OS.gtk_tree_view_get_selection (handle);
		int /*long*/ [] model =  null;
		int /*long*/ list = OS.gtk_tree_selection_get_selected_rows (selection, model);
		if (list == 0) return null;
		int count = Math.min(10, OS.g_list_length (list));

		Display display = tree.getDisplay();
		if (count == 1) {
			int /*long*/ path = OS.g_list_nth_data (list, 0);
			int /*long*/ icon = OS.gtk_tree_view_create_row_drag_icon (handle, path);
			dragSourceImage =  Image.gtk_new (display, SWT.ICON, icon, 0);
			OS.gtk_tree_path_free (path);
		} else {
			int width = 0, height = 0;
			int[] w = new int[1], h = new int[1];
			int[] yy = new int[count], hh = new int[count];
			int /*long*/ [] icons = new int /*long*/ [count];
			GdkRectangle rect = new GdkRectangle ();
			for (int i=0; i= OS.VERSION(2, 24, 0)) {
					OS.gdk_pixmap_get_size(icons[i], w, h);
				} else {
					OS.gdk_drawable_get_size(icons[i], w, h);
				}
				width = Math.max(width, w[0]);
				height = rect.y + h[0] - yy[0];
				yy[i] = rect.y;
				hh[i] = h[0];
				OS.gtk_tree_path_free (path);
			}
			if (OS.GTK3) {
				int /*long*/ surface = Cairo.cairo_image_surface_create(Cairo.CAIRO_FORMAT_ARGB32, width, height);
				if (surface == 0) SWT.error(SWT.ERROR_NO_HANDLES);
				int /*long*/ cairo = Cairo.cairo_create(surface);
				if (cairo == 0) SWT.error(SWT.ERROR_NO_HANDLES);
				Cairo.cairo_set_operator(cairo, Cairo.CAIRO_OPERATOR_SOURCE);
				for (int i=0; i