examples/org.eclipse.swt.snippets/src/org/eclipse/swt/snippets/Snippet220.java

/*******************************************************************************
 * Copyright (c) 2000, 2016 IBM Corporation and others.
 *
 * This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package org.eclipse.swt.snippets;
/*
 * Tree example snippet: Images on the right side of the TreeItem
 *
 * For a detailed explanation of this snippet see
 * http://www.eclipse.org/articles/Article-CustomDrawingTableAndTreeItems/customDraw.htm#_example5
 *
 * For a list of all SWT example snippets see
 * http://www.eclipse.org/swt/snippets/
 *
 * @since 3.2
 */

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

public class Snippet220 {

public static void main(String [] args) {
	Display display = new Display();
	Shell shell = new Shell(display);
	shell.setText("Snippet 220");
	shell.setBounds(10, 10, 350, 200);
	Image xImage = new Image (display, 16, 16);
	GC gc = new GC(xImage);
	gc.setForeground(display.getSystemColor(SWT.COLOR_RED));
	gc.drawLine(1, 1, 14, 14);
	gc.drawLine(1, 14, 14, 1);
	gc.drawOval(2, 2, 11, 11);
	gc.dispose();
	final int IMAGE_MARGIN = 2;
	final Tree tree = new Tree(shell, SWT.CHECK);
	tree.setBounds(10, 10, 300, 150);
	TreeItem item = new TreeItem(tree, SWT.NONE);
	item.setText("root item");
	for (int i = 0; i < 4; i++) {
		TreeItem newItem = new TreeItem(item, SWT.NONE);
		newItem.setText("descendent " + i);
		if (i % 2 == 0) newItem.setData(xImage);
		item.setExpanded(true);
		item = newItem;
	}

	/*
	 * NOTE: MeasureItem and PaintItem are called repeatedly.  Therefore it is
	 * critical for performance that these methods be as efficient as possible.
	 */
	tree.addListener(SWT.MeasureItem, event -> {
		TreeItem item1 = (TreeItem)event.item;
		Image trailingImage = (Image)item1.getData();
		if (trailingImage != null) {
			event.width += trailingImage.getBounds().width + IMAGE_MARGIN;
		}
	});
	tree.addListener(SWT.PaintItem, event -> {
		TreeItem item1 = (TreeItem)event.item;
		Image trailingImage = (Image)item1.getData();
		if (trailingImage != null) {
			int x = event.x + event.width + IMAGE_MARGIN;
			int itemHeight = tree.getItemHeight();
			int imageHeight = trailingImage.getBounds().height;
			int y = event.y + (itemHeight - imageHeight) / 2;
			event.gc.drawImage(trailingImage, x, y);
		}
	});

	shell.open();
	while (!shell.isDisposed()) {
		if (!display.readAndDispatch()) display.sleep();
	}
	xImage.dispose();
	display.dispose();
}
}