gcc/libjava/classpath/gnu/java/awt/java2d/PolyEdge.java

/* PolyEdge.java -- An edge in a polygon, used for polygon filling
   Copyright (C) 2006 Free Software Foundation, Inc.

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
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */


package gnu.java.awt.java2d;

/**
 * An edge in a polygon. This is used by the scanline conversion algorithm
 * implemented in {@link AbstractGraphics2D#rawFillShape}.
 *
 * @author Roman Kennke (kennke@aicas.com)
 */
public class PolyEdge
  implements Comparable
{

  /**
   * The start and end coordinates of the edge. y0 is always smaller or equal
   * than y1.
   */
  public double x0, y0, x1, y1;

  /**
   * The slope of the edge. This is dx / dy.
   */
  double slope;

  /**
   * The intersection of this edge with the current scanline.
   */
  double xIntersection;

  /**
   * Creates a new PolyEdge with the specified coordinates.
   *
   * @param x0 the starting point, x coordinate
   * @param y0 the starting point, y coordinate
   * @param x1 the end point, x coordinate
   * @param y1 the end point, y coordinate
   */
  PolyEdge(double x0, double y0, double x1, double y1)
  {
    if (y0 < y1)
      {
        this.x0 = x0;
        this.y0 = y0;
        this.x1 = x1;
        this.y1 = y1;
      }
    else
      {
        this.x0 = x1;
        this.y0 = y1;
        this.x1 = x0;
        this.y1 = y0;
      }
    slope = (this.x1 - this.x0) / (this.y1 - this.y0);
    if (this.y0 == this.y1) // Horizontal edge.
      xIntersection = Math.min(this.x0, this.x1);
    else
      xIntersection = this.x0 + slope * (Math.ceil(this.y0) - this.y0);
  }

  /**
   * Sorts PolyEdges by the x coordinate from the minimum x value.
   */
  public int compareTo(Object o)
  {
    PolyEdge other = (PolyEdge) o;
    int comp = 0;
    if (x0 < other.x0)
      comp = -1;
    else if (x0 > other.x0)
      comp = 1;
    return comp;
  }

  public String toString()
  {
    return "Edge: " + x0 + ", " + y0 + ", " + x1 + ", " + y1 + ", slope: "
           + slope + ", xIntersection: " + xIntersection;
  }
}