bundles/org.eclipse.draw2d/src/org/eclipse/draw2d/ChopboxAnchor.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;
import org.eclipse.draw2d.geometry.Rectangle;

/**
 * The ChopboxAnchor's location is found by calculating the intersection of a
 * line drawn from the center point of its owner's box to a reference point on
 * that box. Thus {@link Connection Connections} using the ChopBoxAnchor will be
 * oriented such that they point to their owner's center.
 */
public class ChopboxAnchor extends AbstractConnectionAnchor {

	/**
	 * Constructs a new ChopboxAnchor.
	 */
	protected ChopboxAnchor() {
	}

	/**
	 * Constructs a ChopboxAnchor with the given <i>owner</i> figure.
	 * 
	 * @param owner
	 *            The owner figure
	 * @since 2.0
	 */
	public ChopboxAnchor(IFigure owner) {
		super(owner);
	}

	/**
	 * Gets a Rectangle from {@link #getBox()} and returns the Point where a
	 * line from the center of the Rectangle to the Point <i>reference</i>
	 * intersects the Rectangle.
	 * 
	 * @param reference
	 *            The reference point
	 * @return The anchor location
	 */
	public Point getLocation(Point reference) {
		Rectangle r = Rectangle.SINGLETON;
		r.setBounds(getBox());
		r.translate(-1, -1);
		r.resize(1, 1);

		getOwner().translateToAbsolute(r);
		float centerX = r.x + 0.5f * r.width;
		float centerY = r.y + 0.5f * r.height;

		if (r.isEmpty()
				|| (reference.x == (int) centerX && reference.y == (int) centerY))
			return new Point((int) centerX, (int) centerY); // This avoids
															// divide-by-zero

		float dx = reference.x - centerX;
		float dy = reference.y - centerY;

		// r.width, r.height, dx, and dy are guaranteed to be non-zero.
		float scale = 0.5f / Math.max(Math.abs(dx) / r.width, Math.abs(dy)
				/ r.height);

		dx *= scale;
		dy *= scale;
		centerX += dx;
		centerY += dy;

		return new Point(Math.round(centerX), Math.round(centerY));
	}

	/**
	 * Returns the bounds of this ChopboxAnchor's owner. Subclasses can override
	 * this method to adjust the box the anchor can be placed on. For instance,
	 * the owner figure may have a drop shadow that should not be included in
	 * the box.
	 * 
	 * @return The bounds of this ChopboxAnchor's owner
	 * @since 2.0
	 */
	protected Rectangle getBox() {
		return getOwner().getBounds();
	}

	/**
	 * Returns the anchor's reference point. In the case of the ChopboxAnchor,
	 * this is the center of the anchor's owner.
	 * 
	 * @return The reference point
	 */
	public Point getReferencePoint() {
		Point ref = getBox().getCenter();
		getOwner().translateToAbsolute(ref);
		return ref;
	}

	/**
	 * Returns <code>true</code> if the other anchor has the same owner and box.
	 * 
	 * @param obj
	 *            the other anchor
	 * @return <code>true</code> if equal
	 */
	public boolean equals(Object obj) {
		if (obj instanceof ChopboxAnchor) {
			ChopboxAnchor other = (ChopboxAnchor) obj;
			return other.getOwner() == getOwner()
					&& other.getBox().equals(getBox());
		}
		return false;
	}

	/**
	 * The owning figure's hashcode is used since equality is approximately
	 * based on the owner.
	 * 
	 * @return the hash code.
	 */
	public int hashCode() {
		if (getOwner() != null)
			return getOwner().hashCode();
		else
			return super.hashCode();
	}

}