libjava/java/awt/geom/PathIterator.java

   1 /* PathIterator.java -- describes a shape by iterating over its vertices
   2    Copyright (C) 2000, 2002 Free Software Foundation
   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., 59 Temple Place, Suite 330, Boston, MA
  19 02111-1307 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 package java.awt.geom;
  39
  40 /**
  41  * This interface provides a directed path over the boundary of a shape. The
  42  * path can contain 1st through 3rd order Bezier curves (lines, and quadratic
  43  * and cubic splines). A shape can have multiple disjoint paths via the
  44  * MOVETO directive, and can close a circular path back to the previos
  45  * MOVETO via the CLOSE directive.
  46  *
  47  * @author Tom Tromey <tromey@cygnus.com>
  48  * @author Eric Blake <ebb9@email.byu.edu>
  49  * @see Shape
  50  * @see Stroke
  51  * @see FlatteningPathIterator
  52  * @since 1.2
  53  * @status updated to 1.4
  54  */
  55 public interface PathIterator
  56 {
  57   /**
  58    * The even-odd winding mode: a point is internal to the shape if a ray
  59    * from the point to infinity (in any direction) crosses an odd number of
  60    * segments.
  61    */
  62   static final int WIND_EVEN_ODD = 0;
  63
  64   /**
  65    * The non-zero winding mode: a point is internal to the shape if a ray
  66    * from the point to infinity (in any direction) crosses a different number
  67    * of segments headed clockwise than those headed counterclockwise.
  68    */
  69   static final int WIND_NON_ZERO = 1;
  70
  71   /**
  72    * Starts a new subpath. There is no segment from the previous vertex.
  73    */
  74   static final int SEG_MOVETO = 0;
  75
  76   /**
  77    * The current segment is a line.
  78    */
  79   static final int SEG_LINETO = 1;
  80
  81   /**
  82    * The current segment is a quadratic parametric curve. It is interpolated
  83    * as t varies from 0 to 1 over the current point (CP), first control point
  84    * (P1), and final interpolated control point (P2):
  85    * <pre>
  86    *  P(t) = B(2,0)*CP + B(2,1)*P1 + B(2,2)*P2
  87    *    0 &lt;= t &lt;= 1
  88    *  B(n,m) = mth coefficient of nth degree Bernstein polynomial
  89    *         = C(n,m) * t^(m) * (1 - t)^(n-m)
  90    *  C(n,m) = Combinations of n things, taken m at a time
  91    *         = n! / (m! * (n-m)!)
  92    * </pre>
  93    */
  94   static final int SEG_QUADTO = 2;
  95
  96   /**
  97    * The current segment is a cubic parametric curve (more commonly known as
  98    * a Bezier curve). It is interpolated as t varies from 0 to 1 over the
  99    * current point (CP), first control point (P1), the second control point
 100    * (P2), and final interpolated control point (P3):
 101    * <pre>
 102    *  P(t) = B(3,0)*CP + B(3,1)*P1 + B(3,2)*P2 + B(3,3)*P3
 103    *    0 &lt;= t &lt;= 1
 104    *  B(n,m) = mth coefficient of nth degree Bernstein polynomial
 105    *         = C(n,m) * t^(m) * (1 - t)^(n-m)
 106    *  C(n,m) = Combinations of n things, taken m at a time
 107    *         = n! / (m! * (n-m)!)
 108    * </pre>
 109    */
 110   static final int SEG_CUBICTO = 3;
 111
 112   /**
 113    * The current segment closes a loop by an implicit line to the previous
 114    * SEG_MOVETO coordinate.
 115    */
 116   static final int SEG_CLOSE = 4;
 117
 118   /**
 119    * Returns the winding rule to determine which points are inside this path.
 120    *
 121    * @return the winding rule
 122    * @see #WIND_EVEN_ODD
 123    * @see #WIND_NON_ZERO
 124    */
 125   int getWindingRule();
 126
 127   /**
 128    * Tests if the iterator is exhausted. If this returns false, currentSegment
 129    * and next may throw a NoSuchElementException (although this is not
 130    * required).
 131    *
 132    * @return true if the iteration is complete
 133    */
 134   boolean isDone();
 135
 136   /**
 137    * Advance to the next segment in the iteration. It is not specified what
 138    * this does if called when isDone() returns false.
 139    *
 140    * @throws java.util.NoSuchElementException optional when isDone() is true
 141    */
 142   void next();
 143
 144   /**
 145    * Returns the coordinates of the next point(s), as well as the type of
 146    * line segment. The input array must be at least a float[6], to accomodate
 147    * up to three (x,y) point pairs (although if you know the iterator is
 148    * flat, you can probably get by with a float[2]). If the returned type is
 149    * SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if
 150    * the returned type is SEG_QUADTO, the first two points are modified; if
 151    * the returned type is SEG_CUBICTO, all three points are modified; and if
 152    * the returned type is SEG_CLOSE, the array is untouched.
 153    *
 154    * @param coords the array to place the point coordinates in
 155    * @return the segment type
 156    * @throws NullPointerException if coords is null
 157    * @throws ArrayIndexOutOfBoundsException if coords is too small
 158    * @throws java.util.NoSuchElementException optional when isDone() is true
 159    * @see #SEG_MOVETO
 160    * @see #SEG_LINETO
 161    * @see #SEG_QUADTO
 162    * @see #SEG_CUBICTO
 163    * @see #SEG_CLOSE
 164    */
 165   int currentSegment(float[] coords);
 166
 167   /**
 168    * Returns the coordinates of the next point(s), as well as the type of
 169    * line segment. The input array must be at least a double[6], to accomodate
 170    * up to three (x,y) point pairs (although if you know the iterator is
 171    * flat, you can probably get by with a double[2]). If the returned type is
 172    * SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if
 173    * the returned type is SEG_QUADTO, the first two points are modified; if
 174    * the returned type is SEG_CUBICTO, all three points are modified; and if
 175    * the returned type is SEG_CLOSE, the array is untouched.
 176    *
 177    * @param coords the array to place the point coordinates in
 178    * @return the segment type
 179    * @throws NullPointerException if coords is null
 180    * @throws ArrayIndexOutOfBoundsException if coords is too small
 181    * @throws java.util.NoSuchElementException optional when isDone() is true
 182    * @see #SEG_MOVETO
 183    * @see #SEG_LINETO
 184    * @see #SEG_QUADTO
 185    * @see #SEG_CUBICTO
 186    * @see #SEG_CLOSE
 187    */
 188   int currentSegment(double[] coords);
 189 } // interface PathIterator