bundles/org.eclipse.draw2d/src/org/eclipse/draw2d/ConnectionLocator.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.Dimension;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.draw2d.geometry.PointList;

/**
 * Repositions a {@link Figure} attached to a {@link Connection} when the
 * Connection is moved. Provides for alignment at the start (source), middle, or
 * end (target) of the Connection.
 */
public class ConnectionLocator extends AbstractLocator {

	/** @deprecated Use {@link #SOURCE} */
	public static final int START = 2;
	/** The start (or source) of the Connection */
	public static final int SOURCE = 2;

	/** @deprecated Use {@link #TARGET} */
	public static final int END = 3;
	/** The end (or target) of the Connection */
	public static final int TARGET = 3;

	/**
	 * @deprecated Use {@link #MIDDLE} instead, since the location is not the
	 *             midpoint of a line-segment, but the middle of a polyline.
	 */
	public static final int MIDPOINT = 4;
	/** The middle of the Connection */
	public static final int MIDDLE = 4;

	private Connection connection;
	private int alignment;

	/**
	 * Constructs a ConnectionLocator with the passed connection and
	 * {@link #MIDDLE} alignment.
	 * 
	 * @param connection
	 *            The Connection
	 * @since 2.0
	 */
	public ConnectionLocator(Connection connection) {
		this(connection, MIDDLE);
	}

	/**
	 * Constructs a ConnectionLocator with the passed Connection and alignment.
	 * Valid values for the alignment are integer constants {@link #SOURCE},
	 * {@link #MIDDLE}, and {@link #TARGET}.
	 * 
	 * @param connection
	 *            The Connection
	 * @param align
	 *            The alignment
	 * 
	 * @since 2.0
	 */
	public ConnectionLocator(Connection connection, int align) {
		setConnection(connection);
		setAlignment(align);
	}

	/**
	 * Returns the alignment of ConnectionLocator.
	 * 
	 * @return The alignment
	 * @since 2.0
	 */
	public int getAlignment() {
		return alignment;
	}

	/**
	 * Returns connection associated with ConnectionLocator.
	 * 
	 * @return The Connection
	 * @since 2.0
	 */
	protected Connection getConnection() {
		return connection;
	}

	/**
	 * Returns ConnectionLocator's reference point in absolute coordinates.
	 * 
	 * @return The reference point
	 * @since 2.0
	 */
	protected Point getReferencePoint() {
		Point p = getLocation(getConnection().getPoints());
		getConnection().translateToAbsolute(p);
		return p;
	}

	/**
	 * Returns a point from the passed PointList, dependent on
	 * ConnectionLocator's alignment. If the alignment is {@link #SOURCE}, it
	 * returns the first point in <i>points</i>. If {@link #TARGET}, it returns
	 * the last point in <i>points</i>. If {@link #MIDDLE}, it returns the
	 * middle of line represented by <i>points</i>.
	 * 
	 * @param points
	 *            The points in the Connection
	 * @return The location
	 * @since 2.0
	 */
	protected Point getLocation(PointList points) {
		switch (getAlignment()) {
		case SOURCE:
			return points.getPoint(Point.SINGLETON, 0);
		case TARGET:
			return points.getPoint(Point.SINGLETON, points.size() - 1);
		case MIDDLE:
			if (points.size() % 2 == 0) {
				int i = points.size() / 2;
				int j = i - 1;
				Point p1 = points.getPoint(j);
				Point p2 = points.getPoint(i);
				Dimension d = p2.getDifference(p1);
				return Point.SINGLETON.setLocation(p1.x + d.width / 2, p1.y
						+ d.height / 2);
			}
			int i = (points.size() - 1) / 2;
			return points.getPoint(Point.SINGLETON, i);
		default:
			return new Point();
		}
	}

	/**
	 * Sets the alignment. Possible values are {@link #SOURCE}, {@link #MIDDLE},
	 * and {@link #TARGET}.
	 * 
	 * @param align
	 *            The alignment
	 * @since 2.0
	 */
	protected void setAlignment(int align) {
		alignment = align;
	}

	/**
	 * Sets the Connection to be associated with this ConnectionLocator.
	 * 
	 * @param connection
	 *            The Connection
	 * @since 2.0
	 */
	protected void setConnection(Connection connection) {
		this.connection = connection;
	}

}