EllipseAnchor.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.Point;
import org.eclipse.draw2d.geometry.Rectangle;

/**
 * Similar to a {@link org.eclipse.draw2d.ChopboxAnchor}, except this anchor is located on
 * the ellipse defined by the owners bounding box.
 * @author Alex Selkov
 * Created 31.08.2002 23:11:43
 */
public class EllipseAnchor extends AbstractConnectionAnchor {

/**
 * @see org.eclipse.draw2d.AbstractConnectionAnchor#AbstractConnectionAnchor()
 */
public EllipseAnchor() { }

/**
 * @see org.eclipse.draw2d.AbstractConnectionAnchor#AbstractConnectionAnchor(IFigure)
 */
public EllipseAnchor(IFigure owner) {
	super(owner);
}

/**
 * Returns a point on the ellipse (defined by the owner's bounding box) where the
 * connection should be anchored.
 * @see org.eclipse.draw2d.ConnectionAnchor#getLocation(Point)
 */
public Point getLocation(Point reference) {
	Rectangle r = Rectangle.SINGLETON;
	r.setBounds(getOwner().getBounds());
	r.translate(-1, -1);
	r.resize(1, 1);
	getOwner().translateToAbsolute(r);
	
	Point ref = r.getCenter().negate().translate(reference);
	
	if (ref.x == 0)
		return new Point(reference.x, (ref.y > 0) ? r.bottom() : r.y);
	if (ref.y == 0)
		return new Point((ref.x > 0) ? r.right() : r.x, reference.y);
	
	float dx = (ref.x > 0) ? 0.5f : -0.5f;
	float dy = (ref.y > 0) ? 0.5f : -0.5f;
	  
	// ref.x, ref.y, r.width, r.height != 0 => safe to proceed
	  
	float k = (float)(ref.y * r.width) / (ref.x * r.height);
	k = k * k;
	  
	return r.getCenter().translate((int)(r.width * dx / Math.sqrt(1 + k)),
	                                (int)(r.height * dy / Math.sqrt(1 + 1 / k)));
}
}