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annotate dwtx/draw2d/geometry/Geometry.d @ 98:95307ad235d9

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Added Draw2d code, still work in progress
author Frank Benoit <benoit@tionex.de>
date Sun, 03 Aug 2008 00:52:14 +0200
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1 /*******************************************************************************
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2 * Copyright (c) 2005, 2008 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 * Port to the D programming language:
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11 * Frank Benoit <benoit@tionex.de>
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12 *******************************************************************************/
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13 module dwtx.draw2d.geometry.Geometry;
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14
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15 import dwt.dwthelper.utils;
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16
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17 /**
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18 * A Utilities class for geometry operations.
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19 * @author Pratik Shah
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20 * @since 3.1
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21 */
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22 public class Geometry
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23 {
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24
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25 /**
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26 * Determines whether the two line segments formed by the given coordinates intersect. If
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27 * one of the two line segments starts or ends on the other line, then they are considered
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28 * to be intersecting.
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29 *
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30 * @param ux x coordinate of starting point of line 1
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31 * @param uy y coordinate of starting point of line 1
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32 * @param vx x coordinate of ending point of line 1
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33 * @param vy y coordinate of endpoing point of line 1
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34 * @param sx x coordinate of the starting point of line 2
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35 * @param sy y coordinate of the starting point of line 2
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36 * @param tx x coordinate of the ending point of line 2
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37 * @param ty y coordinate of the ending point of line 2
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38 * @return <code>true</code> if the two line segments formed by the given coordinates
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39 * cross
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40 * @since 3.1
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41 */
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42 public static bool linesIntersect(int ux, int uy, int vx, int vy,
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43 int sx, int sy, int tx, int ty) {
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44 /*
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45 * Given the segments: u-------v. s-------t. If s->t is inside the triangle u-v-s,
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46 * then check whether the line u->u splits the line s->t.
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47 */
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48 /* Values are casted to long to avoid integer overflows */
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49 long usX = cast(long) ux - sx;
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50 long usY = cast(long) uy - sy;
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51 long vsX = cast(long) vx - sx;
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52 long vsY = cast(long) vy - sy;
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53 long stX = cast(long) sx - tx;
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54 long stY = cast(long) sy - ty;
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55 if (productSign(cross(vsX, vsY, stX, stY), cross(stX, stY, usX, usY)) >= 0) {
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56 long vuX = cast(long) vx - ux;
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57 long vuY = cast(long) vy - uy;
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58 long utX = cast(long) ux - tx;
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59 long utY = cast(long) uy - ty;
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60 return productSign(cross(-usX, -usY, vuX, vuY), cross(vuX, vuY, utX, utY)) <= 0;
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61 }
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62 return false;
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63 }
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64
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65 private static int productSign(long x, long y) {
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66 if (x is 0 || y is 0) {
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67 return 0;
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68 } else if (x < 0 ^ y < 0) {
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69 return -1;
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70 }
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71 return 1;
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72 }
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73
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74 private static long cross(long x1, long y1, long x2, long y2) {
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75 return x1 * y2 - x2 * y1;
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76 }
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77
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78 }