// Squares Union
// Draw two squares, emphasizing their union

import java.applet.*;
import java.awt.*;
import java.lang.Math;
import TransformableSquare;

public class SquaresUnion extends SquaresApplet {
  public void init() {
    this.setBackground(Color.white);
    this.setForeground(Color.black);
    update(getGraphics());			  // force window create

    square1 = new TransformableSquare(188, imageBufferSize.height/2, 210);
    square1.rotate(2 * Math.PI * 45 / 360);
    square2 = new TransformableSquare(260, imageBufferSize.height/2, 160);
    super.init();

    redrawImage();
  }

  // draw the image
  // roughly - two thick squares, the intersection is striped vertical lines
  public void redrawImage() {
    Graphics g = imageBuffer.getGraphics();
    clearImageBuffer();

    // draw two filled black squares
    g.setColor(getForeground());
    g.fillPolygon(square1.getPolygon());
    g.fillPolygon(square2.getPolygon());

    // make smaller filled white squares inside
    square1.scale(.5);
    square2.scale(.5);
    g.setColor(getBackground());
    g.fillPolygon(square1.getPolygon());
    g.fillPolygon(square2.getPolygon());

    // restore the squares
    square1.scale(2);
    square2.scale(2);

    // draw a couple of circles in the middle of squares
    g.setColor(getForeground());
    g.fillOval(square1.center.x - 10, square1.center.y - 10, 19, 19);
    g.fillOval(square2.center.x - 10, square2.center.y - 10, 19, 19);

    // check how close the squares are
    int distanceSquared = 
      (square1.center.x - square2.center.x) *
      (square1.center.x - square2.center.x) +
      (square1.center.y - square2.center.y) *
      (square1.center.y - square2.center.y);

    // if they're close enough, draw a line between them.
    if (distanceSquared < (square1.scaleFactor + square2.scaleFactor) * (square1.scaleFactor + square2.scaleFactor) / 16) {

      // Cruft below is for drawing a thick line between two points.
      // First, figure out which distance is bigger.
      int xdistance, ydistance;
      xdistance = (square1.center.x - square2.center.x);
      if (xdistance < 0)
	xdistance = -xdistance;
      ydistance = (square1.center.y - square2.center.y);
      if (ydistance < 0)
	ydistance = -ydistance;

      // move one point at a time along the longer axis, drawing
      // lines along the way.
      if (xdistance > ydistance) {
	int x, dx;
	float y, dy;
	dx = (square1.center.x < square2.center.x) ? 1 : -1;
	dy = (float)ydistance / (float)xdistance;
	if (square1.center.y > square2.center.y)
	  dy = -dy;
	for (x = square1.center.x, y = square1.center.y;
	     x != square2.center.x;
	     x += dx, y += dy)
	  g.drawLine(x, Math.round(y) - 3, x, Math.round(y) + 3);
      } else {
	float x, dx;
	int y, dy;
	dy = (square1.center.y < square2.center.y) ? 1 : -1;
	dx = (float)xdistance / (float)ydistance;
	if (square1.center.x > square2.center.x)
	  dx = -dx;
	for (x = square1.center.x, y = square1.center.y;
	     y != square2.center.y;
	     x += dx, y += dy)
	  g.drawLine(Math.round(x) - 3, y, Math.round(x) + 3, y);
      }
    }
    
    repaint();
  }
}