annotate java/src/uk/ac/qmul/eecs/ccmi/gui/Direction.java @ 0:9418ab7b7f3f

Initial import

/*  
 CCmI Editor - A Collaborative Cross-Modal Diagram Editing Tool
	  
 Copyright (C) 2002 Cay S. Horstmann (http://horstmann.com)
 Copyright (C) 2011  Queen Mary University of London (http://ccmi.eecs.qmul.ac.uk/)

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.

 You should have received a copy of the GNU General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

package uk.ac.qmul.eecs.ccmi.gui;

import java.awt.geom.Point2D;

/**
   This class describes a direction in the 2D plane. 
   A direction is a vector of length 1 with an angle between 0 
   (inclusive) and 360 degrees (exclusive). There is also
   a degenerate direction of length 0. 
*/
public class Direction
{
   /**
      Constructs a direction (normalized to length 1).
      @param dx the x-value of the direction
      @param dy the corresponding y-value of the direction
   */
   public Direction(double dx, double dy)
   {
      x = dx;
      y = dy;
      double length = Math.sqrt(x * x + y * y);
      if (length == 0) return;
      x = x / length;
      y = y / length;
   }

   /**
      Constructs a direction between two points
      @param p the starting point
      @param q the ending point
   */
   public Direction(Point2D p, Point2D q)
   {
      this(q.getX() - p.getX(),
         q.getY() - p.getY());
   }
   
   public boolean isParallel(Direction d){
	   if(equals(d.x,d.y,DELTA)||turn(180).equals(d.x,d.y,DELTA))
		   return true;
	   else 
		   return false;
   }

   /**
      Turns this direction by an angle.
      @param angle the angle in degrees
   */
   public Direction turn(double angle){
      double a = Math.toRadians(angle);
      return new Direction(
         x * Math.cos(a) - y * Math.sin(a),
         x * Math.sin(a) + y * Math.cos(a));
   }

   /**
      Gets the x-component of this direction
      @return the x-component (between -1 and 1)
   */
   public double getX()
   {
      return x;
   }

   /**
      Gets the y-component of this direction
      @return the y-component (between -1 and 1)
   */
   public double getY()
   {
      return y;
   }
   
   private boolean equals(double dx, double dy ){
	   return ((x==dx)&&(y==dy));
   }
   
   private boolean equals(double dx, double dy , double delta){
	   return ((Math.abs(x-dx)<delta)&&(Math.abs(y-dy)<delta));
   }
   
   @Override
   public String toString(){
	   return "("+x+","+y+")";
   }

   private double x;
   private double y;
   
   private static final double DELTA = 0.05;

   public static final Direction NORTH = new Direction(0, -1);
   public static final Direction SOUTH = new Direction(0, 1);
   public static final Direction EAST = new Direction(1, 0);
   public static final Direction WEST = new Direction(-1, 0);
   public static final Direction NONE = new Direction(0, 0);
   
   public static Direction compute(Point2D p, Point2D q){
	  double x,y;
	  x = p.getX() - q.getX();
	  y = p.getY() - q.getY();
      double length = Math.sqrt(x * x + y * y);
      if (length == 0) 
    	  return NONE;
      x = x / length;
      y = y / length;
      if(NORTH.equals(x, y))
    	  return NORTH;
      if(SOUTH.equals(x, y))
    	  return SOUTH;
      if(EAST.equals(x, y))
    	  return EAST;
      if(WEST.equals(x, y))
    	  return WEST;
      return NONE;
   }
}