libjava/classpath/gnu/java/awt/java2d/Segment.java

   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   // segment type, PathIterator segment types are used.
  46   public Point2D P1;
  47   public Point2D P2;
  48   public Segment next;
  49   public Segment last;
  50   protected double radius;
  51
  52   public Segment()
  53   {
  54     P1 = P2 = null;
  55     next = null;
  56     last = this;
  57   }
  58
  59   public void add(Segment newsegment)
  60   {
  61     last.next = newsegment;
  62     last = last.next;
  63   }
  64
  65   /**
  66    * Reverses the orientation of the whole polygon
  67    */
  68   public void reverseAll()
  69   {
  70     reverse();
  71     Segment v = next;
  72     Segment former = this;
  73     next = null;
  74
  75     while (v != null)
  76       {
  77         v.reverse();
  78         v.last = this;
  79         Segment oldnext = v.next;
  80         v.next = former;
  81
  82         former = v;
  83         v = oldnext; // move to the next in list
  84       }
  85   }
  86
  87   public String toString()
  88   {
  89     return "Segment:"+P1+", "+P2;
  90   }
  91
  92   /**
  93    * Get the normal vector to the slope of the line.
  94    * Returns: 0.5*width*(norm of derivative of the (x0,y0)-(x1,y1) vector)
  95    */
  96   protected double[] normal(double x0, double y0, double x1, double y1)
  97   {
  98     double dx = (x1 - x0);
  99     double dy = (y1 - y0);
 100     if( dy == 0 )
 101       {
 102         dy = radius * ((dx > 0)?1:-1);
 103         dx = 0;
 104       }
 105     else if( dx == 0 )
 106       {
 107         dx = radius * ((dy > 0)?-1:1);
 108         dy = 0;
 109       }
 110     else
 111       {
 112         double N = Math.sqrt(dx * dx + dy * dy);
 113         double odx = dx;
 114         dx = -radius * dy / N;
 115         dy = radius * odx / N;
 116       }
 117     return new double[]{ dx, dy };
 118   }
 119
 120   public abstract void reverse();
 121
 122   /**
 123    * Get the "top" and "bottom" segments of a segment.
 124    * First array element is p0 + normal, second is p0 - normal.
 125    */
 126   public abstract Segment[] getDisplacedSegments(double radius);
 127
 128   public abstract double[] first();
 129   public abstract double[] last();
 130
 131 }