lookAndFeel/plugins/org.eclipse.papyrus.uml.diagram.clazz.lf.associationlabellayout/src/org/eclipse/papyrus/uml/diagram/clazz/lf/associationlabellayout/locators/AbstractAssociatedSegment.java

/*****************************************************************************
 * Copyright (c) 2019 CEA LIST.
 *
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License 2.0
 * which accompanies this distribution, and is available at
 * https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *  Xavier Le Pallec (for CEA LIST) xlepallec@lilo.org - Bug 558456
 *
 *****************************************************************************/

package org.eclipse.papyrus.uml.diagram.clazz.lf.associationlabellayout.locators;

import org.eclipse.draw2d.IFigure;
import org.eclipse.draw2d.geometry.Point;
import org.eclipse.gef.editparts.AbstractGraphicalEditPart;
import org.eclipse.papyrus.uml.diagram.clazz.edit.parts.AssociationEditPart;

/**
 * This class defines objects that are helpers for associationEditPart for
 * geometric operations.<BR>
 * This class will be specialized for source and for target sides. <BR>
 * Instances will allow to calculate:
 * <UL>
 * <LI>the gradient of segment (of the association) attached to the
 * source/target class/side</LI>
 * <LI>the angle of this segment from the attached class</LI>
 * <LI>the direction of the segment (to the back ?)</LI>
 * <LI>a point on the segment with a given distant to the beginning of the
 * segment (connector segment-class)</LI>
 * </UL>
 *
 */
public abstract class AbstractAssociatedSegment {
	protected IFigure target;
	protected Point startingPoint = null;
	protected Point endPoint = null;
	protected AssociationEditPart associationEditPart;

	/**
	 * The object need the visual element (figure) and the whole association edit
	 * part
	 * 
	 * @param target              the visual element
	 * @param associationEditPart the whole manager of the association (the
	 *                            association edit part)
	 */
	public AbstractAssociatedSegment(IFigure target, AssociationEditPart associationEditPart) {
		this.target = target;
		this.associationEditPart = associationEditPart;
	}

	/**
	 * Abstract method that will be implemented to give the starting point of the
	 * related segment
	 * 
	 * @return the starting point of the segment (connector segment-class)
	 */
	public abstract Point getStartingPoint();

	/**
	 * Abstract method that will be implemented to give the end point of the related
	 * segment (that can be the connector segment-class of the other side if the
	 * association is not multi-segmented)
	 * 
	 * @return the end point of the segment (connector segment-class)
	 */
	public abstract Point getEndPoint();

	/**
	 * Abstract method that will be implemented to give the class concerned by this
	 * side of the association (starting point is on this class)
	 * 
	 * @return class related to this side of the association
	 */
	public abstract AbstractGraphicalEditPart getConnectedElement();

	/**
	 * Gets the gradient of the segment (of the association if it is not
	 * multi-segmented)
	 * 
	 * @return the gradiant
	 */
	public double getGradient() {
		Point p1 = getStartingPoint();
		Point p2 = getEndPoint();
		return (double) (p2.y - p1.y) / (double) (p2.x - p1.x);
	}

	/**
	 * Gets the angle of the segment (of the association if it is not
	 * multi-segmented) compared to a horizontal line.
	 * 
	 * @return the angle (not in degrees)
	 */
	public double getAngle() {
		return Math.atan(getGradient());
	}

	/**
	 * This method returns true if the end of the segment is "before" the start.
	 * 
	 * @return true if the segment get back to the left.
	 */
	public boolean doesSegmentPointToBack() {
		Point p1 = getStartingPoint();
		Point p2 = getEndPoint();
		return (p2.x < p1.x);
	}

	/**
	 * Important method: gives a point on the segment with a given distant to the
	 * beginning of the segment
	 * 
	 * @param distance distance between the starting point and the returned point
	 * @return the point at the wanted distant and on the segment
	 */
	public Point getThePointDistantOf(double distance) {
		try {

			double angle = getAngle();
			double dx = distance * Math.cos(angle);
			double dy = distance * Math.sin(angle);
			Point currentStartingPoint = getStartingPoint();
			if (doesSegmentPointToBack())
				return new Point((int) (currentStartingPoint.x - dx), (int) (currentStartingPoint.y - dy));

			return new Point((int) (currentStartingPoint.x + dx), (int) (currentStartingPoint.y + dy));

		} catch (ArithmeticException ex) {
			int x = getStartingPoint().x;
			int y = getStartingPoint().y;
			if (getStartingPoint().y < getEndPoint().y)
				y += distance;
			else
				y -= distance;
			return new Point(x, y);
		}

	}
}