nulledge.java

ALGAE是一个快速创建算法演示的框架。目前支持的算法实现语言包括java和c

package edu.odu.cs.zeil.AlgAE.Client.DataViewer.DataGraph;

import edu.odu.cs.zeil.AlgAE.Direction;
import edu.odu.cs.zeil.AlgAE.Client.DataViewer.DataGraph.Edge;
import edu.odu.cs.zeil.AlgAE.Client.DataViewer.DataGraph.Edgeable;
import edu.odu.cs.zeil.AlgAE.Client.GraphicsInfo;

import java.awt.Color;
import java.awt.Point;
import java.awt.FontMetrics;
import java.awt.Graphics;


  
/**
 *  A NullEdge is an edge with a source but no destination.
 *  This may not make mush sense in classical graph theory, but in
 *  AlgAE a NullEdge is used to represent null pointers.
 */
public class NullEdge extends Edge
{

  NullEdge(Edgeable src, int direction, Color colour, String edgeLabel)
  {
    super (src, null, direction, colour, edgeLabel);
  }
  

  Point entryPoint()
  {
    return source.exitPoint(Direction.SW);  // For lack of anything better
  }
  
  

  void draw(GraphicsInfo gi)
  {
    Graphics g = gi.g;
    g.setColor (color);

    // Draw a small circle at the exit point.
    Point sourcePt = exitPoint();
    drawExitPoint (gi, sourcePt);


    if (label != null && label.length() != 0)
      {
	FontMetrics fm = gi.g.getFontMetrics();
	int labelwidth = fm.stringWidth(label);
	int labelheight = fm.getAscent();
	switch (dir) {
	case Direction.NW:
	  g.drawString (label,
			sourcePt.x - (1 + gi.getTextOffset().width)/2 - labelwidth,
			sourcePt.y);
	  break;

	case Direction.NNW:
	case Direction.N:
	case Direction.NNE:
	  g.drawString (label,
			sourcePt.x - labelwidth / 2,
			sourcePt.y - (gi.getTextOffset().height+1)/2);
	  break;
	  
	case Direction.NE:
	  g.drawString (label,
			sourcePt.x + (1 + gi.getTextOffset().width)/2,
			sourcePt.y - (gi.getTextOffset().height+1)/2);
	  break;
	  
	case Direction.ENE:
	case Direction.E:
	case Direction.ESE:
	  g.drawString (label,
			sourcePt.x + (1 + gi.getTextOffset().width)/2,
			sourcePt.y);
	  break;
	  
	case Direction.SE:
	  g.drawString (label,
			sourcePt.x + (1 + gi.getTextOffset().width)/2,
			sourcePt.y + labelheight);
	  break;
	  
	case Direction.SSE:
	case Direction.S:
	case Direction.SSW:
	  g.drawString (label,
			sourcePt.x - labelwidth / 2,
			sourcePt.y + labelheight
			  + (1 + gi.getTextOffset().height)/2);
	  break;
	  
	case Direction.SW:
	  g.drawString (label,
			sourcePt.x - labelwidth - (1 + gi.getTextOffset().width)/2,
			sourcePt.y + labelheight
			  + (1 + gi.getTextOffset().height)/2);
	  break;
	  
	case Direction.WSW:
	case Direction.W:
	case Direction.WNW:
	  g.drawString (label,
			sourcePt.x - labelwidth,
			sourcePt.y);
	  break;
	  
	  
	}
      }
  }


  double length()
  {
    return 0.0;
  }
  

  double positionScore(double targetLength)
  {
    return 0.0;
  }

}