001    /* PathIterator.java -- describes a shape by iterating over its vertices
002       Copyright (C) 2000, 2002, 2003 Free Software Foundation
003    
004    This file is part of GNU Classpath.
005    
006    GNU Classpath is free software; you can redistribute it and/or modify
007    it under the terms of the GNU General Public License as published by
008    the Free Software Foundation; either version 2, or (at your option)
009    any later version.
010    
011    GNU Classpath is distributed in the hope that it will be useful, but
012    WITHOUT ANY WARRANTY; without even the implied warranty of
013    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014    General Public License for more details.
015    
016    You should have received a copy of the GNU General Public License
017    along with GNU Classpath; see the file COPYING.  If not, write to the
018    Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
019    02110-1301 USA.
020    
021    Linking this library statically or dynamically with other modules is
022    making a combined work based on this library.  Thus, the terms and
023    conditions of the GNU General Public License cover the whole
024    combination.
025    
026    As a special exception, the copyright holders of this library give you
027    permission to link this library with independent modules to produce an
028    executable, regardless of the license terms of these independent
029    modules, and to copy and distribute the resulting executable under
030    terms of your choice, provided that you also meet, for each linked
031    independent module, the terms and conditions of the license of that
032    module.  An independent module is a module which is not derived from
033    or based on this library.  If you modify this library, you may extend
034    this exception to your version of the library, but you are not
035    obligated to do so.  If you do not wish to do so, delete this
036    exception statement from your version. */
037    
038    package java.awt.geom;
039    
040    /**
041     * This interface provides a directed path over the boundary of a shape. The
042     * path can contain 1st through 3rd order Bezier curves (lines, and quadratic
043     * and cubic splines). A shape can have multiple disjoint paths via the
044     * MOVETO directive, and can close a circular path back to the previos
045     * MOVETO via the CLOSE directive.
046     *
047     * @author Tom Tromey (tromey@cygnus.com)
048     * @author Eric Blake (ebb9@email.byu.edu)
049     * @see java.awt.Shape
050     * @see java.awt.Stroke
051     * @see FlatteningPathIterator
052     * @since 1.2
053     * @status updated to 1.4
054     */
055    public interface PathIterator
056    {
057      /**
058       * The even-odd winding mode: a point is internal to the shape if a ray
059       * from the point to infinity (in any direction) crosses an odd number of
060       * segments.
061       */
062      int WIND_EVEN_ODD = 0;
063    
064      /**
065       * The non-zero winding mode: a point is internal to the shape if a ray
066       * from the point to infinity (in any direction) crosses a different number
067       * of segments headed clockwise than those headed counterclockwise.
068       */
069      int WIND_NON_ZERO = 1;
070    
071      /**
072       * Starts a new subpath. There is no segment from the previous vertex.
073       */
074      int SEG_MOVETO = 0;
075    
076      /**
077       * The current segment is a line.
078       */
079      int SEG_LINETO = 1;
080    
081      /**
082       * The current segment is a quadratic parametric curve. It is interpolated
083       * as t varies from 0 to 1 over the current point (CP), first control point
084       * (P1), and final interpolated control point (P2):
085       * <pre>
086       *  P(t) = B(2,0)*CP + B(2,1)*P1 + B(2,2)*P2
087       *    0 &lt;= t &lt;= 1
088       *  B(n,m) = mth coefficient of nth degree Bernstein polynomial
089       *         = C(n,m) * t^(m) * (1 - t)^(n-m)
090       *  C(n,m) = Combinations of n things, taken m at a time
091       *         = n! / (m! * (n-m)!)
092       * </pre>
093       */
094      int SEG_QUADTO = 2;
095    
096      /**
097       * The current segment is a cubic parametric curve (more commonly known as
098       * a Bezier curve). It is interpolated as t varies from 0 to 1 over the
099       * 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      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      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 true, 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 true.
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