bundles/org.eclipse.draw2d/src/org/eclipse/draw2d/MidpointLocator.java

/*******************************************************************************
 * Copyright (c) 2000, 2010 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.draw2d;

import org.eclipse.draw2d.geometry.Point;

/**
 * A ConnectionLocator that is used to place figures at the midpoint between two
 * points on a {@link org.eclipse.draw2d.Connection}.
 */
public class MidpointLocator extends ConnectionLocator {

	private int index;

	/**
	 * Constructs a MidpointLocator with associated Connection <i>c</i> and
	 * index <i>i</i>. The points at index i and i+1 on the connection are used
	 * to calculate the midpoint of the line segment.
	 * 
	 * @param c
	 *            the connection associated with the locator
	 * @param i
	 *            the point from where the connection's midpoint will be
	 *            calculated.
	 * @since 2.0
	 */
	public MidpointLocator(Connection c, int i) {
		super(c);
		index = i;
	}

	/**
	 * Returns this MidpointLocator's index. This integer represents the
	 * position of the start point in this MidpointLocator's associated
	 * {@link Connection} from where midpoint calculation will be made.
	 * 
	 * @return the locator's index
	 * @since 2.0
	 */

	protected int getIndex() {
		return index;
	}

	/**
	 * Returns the point of reference associated with this locator. This point
	 * will be midway between points at 'index' and 'index' + 1.
	 * 
	 * @return the reference point
	 * @since 2.0
	 */
	protected Point getReferencePoint() {
		Connection conn = getConnection();
		Point p = Point.SINGLETON;
		Point p1 = conn.getPoints().getPoint(getIndex());
		Point p2 = conn.getPoints().getPoint(getIndex() + 1);
		conn.translateToAbsolute(p1);
		conn.translateToAbsolute(p2);
		p.x = (p2.x - p1.x) / 2 + p1.x;
		p.y = (p2.y - p1.y) / 2 + p1.y;
		return p;
	}

}