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1 /*
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2 CCmI Editor - A Collaborative Cross-Modal Diagram Editing Tool
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3
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4 Copyright (C) 2002 Cay S. Horstmann (http://horstmann.com)
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5 Copyright (C) 2011 Queen Mary University of London (http://ccmi.eecs.qmul.ac.uk/)
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6
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7 This program is free software: you can redistribute it and/or modify
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8 it under the terms of the GNU General Public License as published by
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9 the Free Software Foundation, either version 3 of the License, or
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10 (at your option) any later version.
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11
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12 This program is distributed in the hope that it will be useful,
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13 but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 GNU General Public License for more details.
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16
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17 You should have received a copy of the GNU General Public License
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18 along with this program. If not, see <http://www.gnu.org/licenses/>.
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19 */
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20
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21 package uk.ac.qmul.eecs.ccmi.gui;
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22
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23 import java.awt.geom.Point2D;
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24
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25 /**
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26 This class describes a direction in the 2D plane.
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27 A direction is a vector of length 1 with an angle between 0
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28 (inclusive) and 360 degrees (exclusive). There is also
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29 a degenerate direction of length 0.
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30 */
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31 public class Direction
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32 {
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33 /**
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34 Constructs a direction (normalized to length 1).
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35 @param dx the x-value of the direction
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36 @param dy the corresponding y-value of the direction
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37 */
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38 public Direction(double dx, double dy)
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39 {
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40 x = dx;
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41 y = dy;
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42 double length = Math.sqrt(x * x + y * y);
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43 if (length == 0) return;
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44 x = x / length;
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45 y = y / length;
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46 }
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47
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48 /**
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49 Constructs a direction between two points
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50 @param p the starting point
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51 @param q the ending point
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52 */
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53 public Direction(Point2D p, Point2D q)
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54 {
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55 this(q.getX() - p.getX(),
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56 q.getY() - p.getY());
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57 }
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58
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59 /**
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60 * Checks whether the direction passed as argument is parallel to this direction.
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61 *
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62 * @param d the direction to check against
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63 * @return {@code true} if this direction and {@code d} are parallel to each other, false otherwise
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64 */
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65 public boolean isParallel(Direction d){
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66 if(equals(d.x,d.y,DELTA)||turn(180).equals(d.x,d.y,DELTA))
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67 return true;
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68 else
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69 return false;
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70 }
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71
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72 /**
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73 Turns this direction by an angle.
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74 @param angle the angle in degrees
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75
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76 @return a new object representing the turned direction
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77 */
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78 public Direction turn(double angle){
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79 double a = Math.toRadians(angle);
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80 return new Direction(
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81 x * Math.cos(a) - y * Math.sin(a),
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82 x * Math.sin(a) + y * Math.cos(a));
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83 }
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84
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85 /**
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86 Gets the x-component of this direction
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87 @return the x-component (between -1 and 1)
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88 */
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89 public double getX() {
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90 return x;
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91 }
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92
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93 /**
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94 Gets the y-component of this direction
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95 @return the y-component (between -1 and 1)
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96 */
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97 public double getY() {
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98 return y;
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99 }
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100
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101 private boolean equals(double dx, double dy ){
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102 return ((x==dx)&&(y==dy));
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103 }
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104
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105 private boolean equals(double dx, double dy , double delta){
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106 return ((Math.abs(x-dx)<delta)&&(Math.abs(y-dy)<delta));
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107 }
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108
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109 @Override
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110 public String toString(){
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111 return "("+x+","+y+")";
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112 }
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113
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114 private double x;
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115 private double y;
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116
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117 private static final double DELTA = 0.05;
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118
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119 public static final Direction NORTH = new Direction(0, -1);
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120 public static final Direction SOUTH = new Direction(0, 1);
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121 public static final Direction EAST = new Direction(1, 0);
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122 public static final Direction WEST = new Direction(-1, 0);
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123 public static final Direction NONE = new Direction(0, 0);
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124
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125 public static Direction compute(Point2D p, Point2D q){
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126 double x,y;
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127 x = p.getX() - q.getX();
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128 y = p.getY() - q.getY();
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129 double length = Math.sqrt(x * x + y * y);
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130 if (length == 0)
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131 return NONE;
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132 x = x / length;
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133 y = y / length;
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134 if(NORTH.equals(x, y))
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135 return NORTH;
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136 if(SOUTH.equals(x, y))
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137 return SOUTH;
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138 if(EAST.equals(x, y))
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139 return EAST;
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140 if(WEST.equals(x, y))
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141 return WEST;
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142 return NONE;
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143 }
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144 }
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