bundles/org.eclipse.gef/src/org/eclipse/gef/editpolicies/FeedbackHelper.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.gef.editpolicies;

import org.eclipse.draw2d.Connection;
import org.eclipse.draw2d.ConnectionAnchor;
import org.eclipse.draw2d.XYAnchor;
import org.eclipse.draw2d.geometry.Point;

/**
 * Helps display connection feedback during drags of the connection ends. This
 * class is used internally by the provided EditPolicy implementation.
 * 
 * @author hudsonr
 */
public class FeedbackHelper {

	private Connection connection;
	private XYAnchor dummyAnchor;
	private boolean isMovingStartAnchor = false;

	/**
	 * Constructs a new FeedbackHelper.
	 */
	public FeedbackHelper() {
		dummyAnchor = new XYAnchor(new Point(10, 10));
	}

	/**
	 * Returns the connection being used to show feedback.
	 * 
	 * @return the connection
	 */
	protected Connection getConnection() {
		return connection;
	}

	/**
	 * Returns true is the feedback is moving the source anchor
	 * 
	 * @return <code>true</code> if moving start
	 */
	protected boolean isMovingStartAnchor() {
		return isMovingStartAnchor;
	}

	/**
	 * Sets the connection.
	 * 
	 * @param c
	 *            connection
	 */
	public void setConnection(Connection c) {
		connection = c;
	}

	/**
	 * Sets if moving start of connection.
	 * 
	 * @param value
	 *            <code>true</code> if the starts is being moved
	 */
	public void setMovingStartAnchor(boolean value) {
		isMovingStartAnchor = value;
	}

	/**
	 * Sets the anchor for the end being moved.
	 * 
	 * @param anchor
	 *            the new anchor
	 */
	protected void setAnchor(ConnectionAnchor anchor) {
		if (isMovingStartAnchor())
			getConnection().setSourceAnchor(anchor);
		else
			getConnection().setTargetAnchor(anchor);
	}

	/**
	 * Updates the feedback based on the given anchor or point. The anchor is
	 * used unless <code>null</code>. The point is used when there is no anchor.
	 * 
	 * @param anchor
	 *            <code>null</code> or an anchor
	 * @param p
	 *            the point to use when there is no anchor
	 */
	public void update(ConnectionAnchor anchor, Point p) {
		if (anchor != null)
			setAnchor(anchor);
		else {
			dummyAnchor.setLocation(p);
			setAnchor(dummyAnchor);
		}
	}

}