Most everything in our Draw( ) method is straightforward, with two exceptions.

        int xflag = 0;
        for (x = xMin; x <= xMax; x++) {
            if ((e0|e1|e2) >= 0) {
                r.pixel[y+x] = color;
                xflag++;
            } else if (xflag != 0) break;
            e0 += A0;
            e1 += A1;
            e2 += A2;
        }
	

• All three edges are tested with a single comparison by oring together the three edges and checking if the result is positive. If any one of the three is negative then its sign-bit will be set to a 1, and the result of the or will be negative.
  
  
• Since triangles are convex, we can only be inside for a single interval on any given scanline. The xflag variable is used to keep track of when we exit the triangle's interior. If ever we find ourselves outside of the triangle having already set some pixels on the span then we can skip over the remainder of the scanline.