import java.applet.*;

/** Bresenham algorithm for drawing a line */
public class Bresenham extends DDA {

  /* these need to be instance variables so that we can display them with
     the showState() method */
  int x;
  int y;
  int p;
  int const1;
  int const2;

  public String showState() {
    return "x = " + x +
      "\ny = " + y +
      "\np = " + p +
      "\nconst1 = " + const1 +
      "\nconst2 = " + const2;
  }


  void drawLine(int x1, int y1, int x2, int y2) {
    int dx = x2 - x1;
    int dy = y2 - y1;
    const1 = 2*dy;
    const2 = 2*(dy-dx);
    p = 2*dy - dx;
    y = y1;
    for (x = x1; x <= x2; x++) {
      drawPixel(x,y);
      if (step()) return;
      if (p < 0) {
	p += const1;
      } else {
	p += const2;
	y++;
      }
    }
  }
  
}