gcc/libjava/java/awt/geom/PathIterator.java

/* PathIterator.java -- describes a shape by iterating over its vertices
   Copyright (C) 2000, 2002 Free Software Foundation

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
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WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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02111-1307 USA.

Linking this library statically or dynamically with other modules is
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permission to link this library with independent modules to produce an
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package java.awt.geom;

/**
 * This interface provides a directed path over the boundary of a shape. The
 * path can contain 1st through 3rd order Bezier curves (lines, and quadratic
 * and cubic splines). A shape can have multiple disjoint paths via the
 * MOVETO directive, and can close a circular path back to the previos
 * MOVETO via the CLOSE directive.
 *
 * @author Tom Tromey <tromey@cygnus.com>
 * @author Eric Blake <ebb9@email.byu.edu>
 * @see Shape
 * @see Stroke
 * @see FlatteningPathIterator
 * @since 1.2
 * @status updated to 1.4
 */
public interface PathIterator
{
  /**
   * The even-odd winding mode: a point is internal to the shape if a ray
   * from the point to infinity (in any direction) crosses an odd number of
   * segments.
   */
  static final int WIND_EVEN_ODD = 0;

  /**
   * The non-zero winding mode: a point is internal to the shape if a ray
   * from the point to infinity (in any direction) crosses a different number
   * of segments headed clockwise than those headed counterclockwise.
   */
  static final int WIND_NON_ZERO = 1;

  /**
   * Starts a new subpath. There is no segment from the previous vertex.
   */
  static final int SEG_MOVETO = 0;

  /**
   * The current segment is a line.
   */
  static final int SEG_LINETO = 1;

  /**
   * The current segment is a quadratic parametric curve. It is interpolated
   * as t varies from 0 to 1 over the current point (CP), first control point
   * (P1), and final interpolated control point (P2):
   * <pre>
   *  P(t) = B(2,0)*CP + B(2,1)*P1 + B(2,2)*P2
   *    0 <= t <= 1
   *  B(n,m) = mth coefficient of nth degree Bernstein polynomial
   *         = C(n,m) * t^(m) * (1 - t)^(n-m)
   *  C(n,m) = Combinations of n things, taken m at a time
   *         = n! / (m! * (n-m)!)
   * </pre>
   */
  static final int SEG_QUADTO = 2;

  /**
   * The current segment is a cubic parametric curve (more commonly known as
   * a Bezier curve). It is interpolated as t varies from 0 to 1 over the
   * current point (CP), first control point (P1), the second control point
   * (P2), and final interpolated control point (P3):
   * <pre>
   *  P(t) = B(3,0)*CP + B(3,1)*P1 + B(3,2)*P2 + B(3,3)*P3
   *    0 <= t <= 1
   *  B(n,m) = mth coefficient of nth degree Bernstein polynomial
   *         = C(n,m) * t^(m) * (1 - t)^(n-m)
   *  C(n,m) = Combinations of n things, taken m at a time
   *         = n! / (m! * (n-m)!)
   * </pre>
   */
  static final int SEG_CUBICTO = 3;

  /**
   * The current segment closes a loop by an implicit line to the previous
   * SEG_MOVETO coordinate.
   */
  static final int SEG_CLOSE = 4;

  /**
   * Returns the winding rule to determine which points are inside this path.
   *
   * @return the winding rule
   * @see #WIND_EVEN_ODD
   * @see #WIND_NON_ZERO
   */
  int getWindingRule();

  /**
   * Tests if the iterator is exhausted. If this returns false, currentSegment
   * and next may throw a NoSuchElementException (although this is not
   * required).
   *
   * @return true if the iteration is complete
   */
  boolean isDone();

  /**
   * Advance to the next segment in the iteration. It is not specified what
   * this does if called when isDone() returns false.
   *
   * @throws java.util.NoSuchElementException optional when isDone() is true
   */
  void next();

  /**
   * Returns the coordinates of the next point(s), as well as the type of
   * line segment. The input array must be at least a float[6], to accomodate
   * up to three (x,y) point pairs (although if you know the iterator is
   * flat, you can probably get by with a float[2]). If the returned type is
   * SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if
   * the returned type is SEG_QUADTO, the first two points are modified; if
   * the returned type is SEG_CUBICTO, all three points are modified; and if
   * the returned type is SEG_CLOSE, the array is untouched.
   *
   * @param coords the array to place the point coordinates in
   * @return the segment type
   * @throws NullPointerException if coords is null
   * @throws ArrayIndexOutOfBoundsException if coords is too small
   * @throws java.util.NoSuchElementException optional when isDone() is true
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  int currentSegment(float[] coords);

  /**
   * Returns the coordinates of the next point(s), as well as the type of
   * line segment. The input array must be at least a double[6], to accomodate
   * up to three (x,y) point pairs (although if you know the iterator is
   * flat, you can probably get by with a double[2]). If the returned type is
   * SEG_MOVETO or SEG_LINETO, the first point in the array is modified; if
   * the returned type is SEG_QUADTO, the first two points are modified; if
   * the returned type is SEG_CUBICTO, all three points are modified; and if
   * the returned type is SEG_CLOSE, the array is untouched.
   *
   * @param coords the array to place the point coordinates in
   * @return the segment type
   * @throws NullPointerException if coords is null
   * @throws ArrayIndexOutOfBoundsException if coords is too small
   * @throws java.util.NoSuchElementException optional when isDone() is true
   * @see #SEG_MOVETO
   * @see #SEG_LINETO
   * @see #SEG_QUADTO
   * @see #SEG_CUBICTO
   * @see #SEG_CLOSE
   */
  int currentSegment(double[] coords);
} // interface PathIterator