ConnectionLocator.java

/*******************************************************************************
 * Copyright (c) 2000, 2005 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;
}

}