/**
  * Cache the {@link Line2D} objects making up the maze.
  *
  * @param x Initial x coordinate.
  * @param y Initial y coordinate.
  * @param width Width of a cell.
  * @param height Height of a cell.
  */
 private void buildWalls(double x, double y, double width, double height) {
   Point p = maze.getSize();
   wallList = new ArrayList(p.getX() * p.getY());
   for (int i = 0; i < p.getY(); i++) {
     for (int j = 0; j < p.getX(); j++) {
       Cell cell = maze.getCell(new Point(j, i));
       if (cell.isWall(Direction.North)) {
         wallList.add(
             new Line2D.Double(
                 x + j * width, y + (i + 1) * height, x + (j + 1) * width, y + (i + 1) * height));
       }
       if (cell.isWall(Direction.East)) {
         wallList.add(
             new Line2D.Double(
                 x + (j + 1) * width, y + i * height, x + (j + 1) * width, y + (i + 1) * height));
       }
     }
   }
 }
  public void paintComponent(Graphics g) {
    super.paintComponent(g); // paint background
    Graphics2D g2 = (Graphics2D) g;

    // Turn on antialiasing
    Map m = new HashMap();
    m.put(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
    g2.addRenderingHints(m);

    // Figure out how large the maze is
    Point p = maze.getSize();

    double llx = 0.0, lly = 0.0, width = 0.0, height = 0.0, cellwidth = 0.0, cellheight = 0.0;
    // Do we need to update our cache?
    if ((panelSize == null) || (panelSize != getSize())) {
      panelSize = getSize();
      llx = (double) panelSize.width * 0.025;
      lly = (double) panelSize.height * 0.025;
      width = (double) panelSize.width - (double) panelSize.width * 0.05;
      height = (double) panelSize.height - (double) panelSize.height * 0.05;
      cellwidth = width / (double) p.getX();
      cellheight = height / (double) p.getY();
      buildWalls(llx, lly, cellwidth, cellheight);
      double diameter = java.lang.Math.min(cellwidth, cellheight) * 0.75;
      player =
          new Arc2D.Double(
              new Rectangle2D.Double(-diameter / 2.0, -diameter / 2.0, diameter, diameter),
              30.0,
              300.0,
              Arc2D.PIE);
      diameter = java.lang.Math.min(cellwidth, cellheight) * 0.30;
      projectile =
          new Arc2D.Double(
              new Rectangle2D.Double(-diameter / 2.0, -diameter / 2.0, diameter, diameter),
              0.0,
              360.0,
              Arc2D.PIE);
    }

    // Flip coordinate system
    g2.translate(0.0, (double) panelSize.height);
    g2.scale(1.0, -1.0);

    // Draw the maze walls
    g2.setStroke(new BasicStroke(2.0f));
    g2.setColor(Color.black);
    g2.draw(new Rectangle2D.Double(llx, lly, width, height));

    Iterator it = wallList.iterator();
    while (it.hasNext()) {
      Object o = it.next();
      if (o instanceof Shape) {
        g2.draw((Shape) o);
      } else {
        throw new Error();
      }
    }

    Font font = new Font("Arial", Font.PLAIN, 9);
    FontRenderContext frc = g2.getFontRenderContext();

    // Obtain the location of the distinguished client
    Point cp = maze.getClientPoint(client);

    for (int i = 0; i < p.getY(); i++) {
      for (int j = 0; j < p.getX(); j++) {
        boolean cellVisible = true;
        Line2D visLine =
            new Line2D.Double(
                llx + (cp.getX() + 0.5) * cellwidth,
                lly + (cp.getY() + 0.5) * cellheight,
                llx + (j + 0.5) * cellwidth,
                lly + (i + 0.5) * cellheight);

        /* Visibility testing */
        /* Iterator visIt = wallList.iterator();
        while(visIt.hasNext()) {
                Object o = visIt.next();
                if(o instanceof Line2D) {
                        Line2D l = (Line2D)o;
                        if(l.intersectsLine(visLine)) {
                                cellVisible = false;
                        }
                } else {
                        throw new Error();
                }

        } */
        if (cellVisible) {
          Cell cell = maze.getCell(new Point(j, i));
          Object o = cell.getContents();
          if (o != null) {
            if (o instanceof Client) {
              Client c = (Client) o;
              if (c instanceof GUIClient) {
                g2.setColor(Color.green);
              } else if (c instanceof RobotClient) {
                g2.setColor(Color.red);
              } else if (c instanceof RemoteClient) {
                g2.setColor(Color.magenta);
              }

              double xoffset = llx + j * cellwidth + (cellwidth / 2.0);
              double yoffset = lly + i * cellheight + (cellheight / 2.0);
              Direction orient = c.getOrientation();
              g2.translate(xoffset, yoffset);
              double rotation = 0.0;
              if (orient.equals(Direction.South)) {
                rotation = -java.lang.Math.PI / 2.0;
              } else if (orient.equals(Direction.North)) {
                rotation = java.lang.Math.PI / 2.0;
              } else if (orient.equals(Direction.West)) {
                rotation = java.lang.Math.PI;
              }
              g2.rotate(rotation);
              g2.fill(player);
              g2.rotate(-rotation);

              GlyphVector name = font.createGlyphVector(frc, c.getName());
              g2.scale(1.0, -1.0);
              g2.setColor(Color.black);
              g2.drawGlyphVector(name, 0.0f, 0.0f);
              g2.scale(1.0, -1.0);
              g2.translate(-xoffset, -yoffset);

            } else {
              if (o instanceof Projectile) {
                g2.setColor(Color.yellow);
                double xoffset = llx + j * cellwidth + (cellwidth / 2.0);
                double yoffset = lly + i * cellheight + (cellheight / 2.0);
                g2.translate(xoffset, yoffset);
                g2.fill(projectile);
                g2.translate(-xoffset, -yoffset);
              }
            }
          }
        }
      }
    }
  }