Source for gnu.java.awt.java2d.Segment

   1: /* Segment.java -- Abstract segment used for BasicStroke
   2:    Copyright (C) 2006 Free Software Foundation, Inc.
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: 
  39: package gnu.java.awt.java2d;
  40: 
  41: import java.awt.geom.Point2D;
  42: 
  43: public abstract class Segment implements Cloneable
  44: {
  45:   // Start and end points of THIS segment
  46:   public Point2D P1;
  47:   public Point2D P2;
  48: 
  49:   // Segments can be linked together internally as a linked list
  50:   public Segment first;
  51:   public Segment next;
  52:   public Segment last;
  53: 
  54:   // Half the stroke width
  55:   protected double radius;
  56: 
  57:   /**
  58:    * Create a new, empty segment
  59:    */
  60:   public Segment()
  61:   {
  62:     P1 = P2 = null;
  63:     first = this;
  64:     next = null;
  65:     last = this;
  66:   }
  67: 
  68:   /**
  69:    * Add a segment to the polygon
  70:    * @param newsegment segment to add
  71:    */
  72:   public void add(Segment newsegment)
  73:   {
  74:     newsegment.first = first;
  75:     last.next = newsegment;
  76:     last = last.next.last;
  77:   }
  78: 
  79:   /**
  80:    * Reverses the orientation of the whole polygon
  81:    */
  82:   public void reverseAll()
  83:   {
  84:     reverse();
  85:     first = last;
  86:     Segment v = next;
  87:     Segment former = this;
  88:     next = null;
  89: 
  90:     while (v != null)
  91:       {
  92:         v.reverse();
  93:         v.last = this;
  94:         Segment oldnext = v.next;
  95:         v.next = former;
  96: 
  97:         former = v;
  98:         v = oldnext; // move to the next in list
  99:       }
 100:   }
 101: 
 102:   public String toString()
 103:   {
 104:     return "Segment:"+P1+", "+P2;
 105:   }
 106: 
 107:   /**
 108:    * Get the normal vector to the slope of the line.
 109:    * @return vector of length radius, normal to the (x0,y0)-(x1,y1) vector)
 110:    */
 111:   protected double[] normal(double x0, double y0, double x1, double y1)
 112:   {
 113:     double dx = (x1 - x0);
 114:     double dy = (y1 - y0);
 115:     if( dy == 0 )
 116:       {
 117:         dy = radius * ((dx > 0)?1:-1);
 118:         dx = 0;
 119:       }
 120:     else if( dx == 0 )
 121:       {
 122:         dx = radius * ((dy > 0)?-1:1);
 123:         dy = 0;
 124:       }
 125:     else
 126:       {
 127:         double N = Math.sqrt(dx * dx + dy * dy);
 128:         double odx = dx;
 129:         dx = -radius * dy / N;
 130:         dy = radius * odx / N;
 131:       }
 132:     return new double[]{ dx, dy };
 133:   }
 134: 
 135:   /**
 136:    * Reverse the current segment
 137:    */
 138:   public abstract void reverse();
 139: 
 140:   /**
 141:    * Get the "top" and "bottom" segments of a segment.
 142:    * First array element is p0 + normal, second is p0 - normal.
 143:    */
 144:   public abstract Segment[] getDisplacedSegments(double radius);
 145: 
 146:   /**
 147:    * Returns the coordinates of the first control point, or the start point
 148:    * for a line segment.
 149:    */
 150:   public abstract double[] cp1();
 151: 
 152:   /**
 153:    * Returns the coordinates of the second control point, or the end point
 154:    * for a line segment.
 155:    */
 156:   public abstract double[] cp2();
 157: 
 158: }