BasicEdgeArrowRenderingSupport

/*
 * Copyright (c) 2005, The JUNG Authors
 * All rights reserved.
 *
 * This software is open-source under the BSD license; see either "license.txt"
 * or https://github.com/jrtom/jung/blob/master/LICENSE for a description.
 *
 * Created on Aug 23, 2005
 */
package edu.uci.ics.jung.visualization.renderers;

import java.awt.Shape;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;
import java.awt.geom.Line2D;
import java.awt.geom.PathIterator;
import java.awt.geom.Point2D;

import edu.uci.ics.jung.visualization.RenderContext;

public class BasicEdgeArrowRenderingSupport<V,E> implements EdgeArrowRenderingSupport<V, E>  {

    public AffineTransform getArrowTransform(RenderContext<V,E> rc, Shape edgeShape, Shape vertexShape) {
    	GeneralPath path = new GeneralPath(edgeShape);
        float[] seg = new float[6];
        Point2D p1=null;
        Point2D p2=null;
        AffineTransform at = new AffineTransform();
        // when the PathIterator is done, switch to the line-subdivide
        // method to get the arrowhead closer.
        for(PathIterator i=path.getPathIterator(null,1); !i.isDone(); i.next()) {
            int ret = i.currentSegment(seg);
            if(ret == PathIterator.SEG_MOVETO) {
                p2 = new Point2D.Float(seg[0],seg[1]);
            } else if(ret == PathIterator.SEG_LINETO) {
                p1 = p2;
                p2 = new Point2D.Float(seg[0],seg[1]);
                if(vertexShape.contains(p2)) {
                    at = getArrowTransform(rc, new Line2D.Float(p1,p2),vertexShape);
                    break;
                }
            }
        }
        return at;
    }

    public AffineTransform getReverseArrowTransform(RenderContext<V,E> rc, Shape edgeShape, Shape vertexShape) {
        return getReverseArrowTransform(rc, edgeShape, vertexShape, true);
    }

    public AffineTransform getReverseArrowTransform(RenderContext<V,E> rc, Shape edgeShape, Shape vertexShape,
            boolean passedGo) {
    	GeneralPath path = new GeneralPath(edgeShape);
        float[] seg = new float[6];
        Point2D p1=null;
        Point2D p2=null;

        AffineTransform at = new AffineTransform();
        for(PathIterator i=path.getPathIterator(null,1); !i.isDone(); i.next()) {
            int ret = i.currentSegment(seg);
            if(ret == PathIterator.SEG_MOVETO) {
                p2 = new Point2D.Float(seg[0],seg[1]);
            } else if(ret == PathIterator.SEG_LINETO) {
                p1 = p2;
                p2 = new Point2D.Float(seg[0],seg[1]);
                if(passedGo == false && vertexShape.contains(p2)) {
                    passedGo = true;
                 } else if(passedGo==true &&
                        vertexShape.contains(p2)==false) {
                     at = getReverseArrowTransform(rc, new Line2D.Float(p1,p2),vertexShape);
                    break;
                }
            }
        }
        return at;
    }

    public AffineTransform getArrowTransform(RenderContext<V,E> rc, Line2D edgeShape, Shape vertexShape) {
        float dx = (float) (edgeShape.getX1()-edgeShape.getX2());
        float dy = (float) (edgeShape.getY1()-edgeShape.getY2());
        // iterate over the line until the edge shape will place the
        // arrowhead closer than 'arrowGap' to the vertex shape boundary
        while((dx*dx+dy*dy) > rc.getArrowPlacementTolerance()) {
            try {
                edgeShape = getLastOutsideSegment(edgeShape, vertexShape);
            } catch(IllegalArgumentException e) {
                System.err.println(e.toString());
                return null;
            }
            dx = (float) (edgeShape.getX1()-edgeShape.getX2());
            dy = (float) (edgeShape.getY1()-edgeShape.getY2());
        }
        double atheta = Math.atan2(dx,dy)+Math.PI/2;
        AffineTransform at =
            AffineTransform.getTranslateInstance(edgeShape.getX1(), edgeShape.getY1());
        at.rotate(-atheta);
        return at;
    }

    protected AffineTransform getReverseArrowTransform(RenderContext<V,E> rc, Line2D edgeShape, Shape vertexShape) {
        float dx = (float) (edgeShape.getX1()-edgeShape.getX2());
        float dy = (float) (edgeShape.getY1()-edgeShape.getY2());
        // iterate over the line until the edge shape will place the
        // arrowhead closer than 'arrowGap' to the vertex shape boundary
        while((dx*dx+dy*dy) > rc.getArrowPlacementTolerance()) {
            try {
                edgeShape = getFirstOutsideSegment(edgeShape, vertexShape);
            } catch(IllegalArgumentException e) {
                System.err.println(e.toString());
                return null;
            }
            dx = (float) (edgeShape.getX1()-edgeShape.getX2());
            dy = (float) (edgeShape.getY1()-edgeShape.getY2());
        }
        // calculate the angle for the arrowhead
        double atheta = Math.atan2(dx,dy)-Math.PI/2;
        AffineTransform at = AffineTransform.getTranslateInstance(edgeShape.getX1(),edgeShape.getY1());
        at.rotate(-atheta);
        return at;
    }

    /**
     * Returns a line that intersects {@code shape}'s boundary.
     *
     * @param line line to subdivide
     * @param shape shape to compare with line
     * @return a line that intersects the shape boundary
     * @throws IllegalArgumentException if the passed line's point2 is not inside the shape
     */
    protected Line2D getLastOutsideSegment(Line2D line, Shape shape) {
        if(shape.contains(line.getP2())==false) {
            String errorString =
                "line end point: "+line.getP2()+" is not contained in shape: "+shape.getBounds2D();
            throw new IllegalArgumentException(errorString);
            //return null;
        }
        Line2D left = new Line2D.Double();
        Line2D right = new Line2D.Double();
        // subdivide the line until its left segment intersects
        // the shape boundary
        do {
            subdivide(line, left, right);
            line = right;
        } while(shape.contains(line.getP1())==false);
        // now that right is completely inside shape,
        // return left, which must be partially outside
        return left;
    }

    /**
     * Returns a line that intersects {@code shape}'s boundary.
     *
     * @param line line to subdivide
     * @param shape shape to compare with line
     * @return a line that intersects the shape boundary
     * @throws IllegalArgumentException if the passed line's point1 is not inside the shape
     */
    protected Line2D getFirstOutsideSegment(Line2D line, Shape shape) {

        if(shape.contains(line.getP1())==false) {
            String errorString =
                "line start point: "+line.getP1()+" is not contained in shape: "+shape.getBounds2D();
            throw new IllegalArgumentException(errorString);
        }
        Line2D left = new Line2D.Float();
        Line2D right = new Line2D.Float();
        // subdivide the line until its right side intersects the
        // shape boundary
        do {
            subdivide(line, left, right);
            line = left;
        } while(shape.contains(line.getP2())==false);
        // now that left is completely inside shape,
        // return right, which must be partially outside
        return right;
    }

    /**
     * divide a Line2D into 2 new Line2Ds that are returned
     * in the passed left and right instances, if non-null
     * @param src the line to divide
     * @param left the left side, or null
     * @param right the right side, or null
     */
    protected void subdivide(Line2D src,
            Line2D left,
            Line2D right) {
        double x1 = src.getX1();
        double y1 = src.getY1();
        double x2 = src.getX2();
        double y2 = src.getY2();

        double mx = x1 + (x2-x1)/2.0;
        double my = y1 + (y2-y1)/2.0;
        if (left != null) {
            left.setLine(x1, y1, mx, my);
        }
        if (right != null) {
            right.setLine(mx, my, x2, y2);
        }
    }

}