// Squares Intersect
// Draw two squares, then highlight their intersection

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

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

    square1 = new TransformableSquare(2*imageBufferSize.width/5, imageBufferSize.height/2, 4*imageBufferSize.width/9);
    square1.rotate(2 * Math.PI * 45 / 360);
    square2 = new TransformableSquare(3*imageBufferSize.width/5, imageBufferSize.height/2, 3*imageBufferSize.width/7);
    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.scalePixels(-10);
    square2.scalePixels(-10);
    g.setColor(getBackground());
    g.fillPolygon(square1.getPolygon());
    g.fillPolygon(square2.getPolygon());

    // now paint vertical lines in the intersection
    g.setColor(getForeground());

    // Find the smaller bounding box (well, not quite - but close)
    TransformableSquare smallerSquare;
    smallerSquare = (square1.scaleFactor < square2.scaleFactor ? square1 : square2);
    Rectangle bound = smallerSquare.getPolygon().getBoundingBox();

    int x, y1, y2;
    // scan across the bounding box
    for (x = bound.x; x < bound.width + bound.x; x+=6) {
      y1 = bound.y;
      // scan down, looking for first intersection
      while (y1 < bound.height + bound.y &&
	     !(square1.inside(x, y1) && square2.inside(x, y1)))
	y1++;
      if (!(square1.inside(x, y1) && square2.inside(x, y1)))
	continue;				  // not found this time..

      // scan down, looking for when we leave the intersection
      y2 = y1;
      while (y2 < bound.height + bound.y &&
	     (square1.inside(x, y2) && square2.inside(x, y2)))
	y2++;
      // draw a line inbetween
      g.fillRect(x-1, y1, 3, y2-y1);
    }

    // restore squares to original size
    square1.scalePixels(10);
    square2.scalePixels(10);
      
    repaint();
  }
}