The NodeTilt( ) Function

ShowNode (
  double *p,             //Pointers to feature's EARTH &
  int *q,                //SCREEN co-ordinates arrays.
  char *n,               //Pointer to annotation name.
  int c                  //Display colour (can be black)
) {
  double
    tilt = *(p + 2),     //tilt of feature on the Earth
    CosPsi = *(p + 3),   //Cosine of bearing
    TanPsi = *(p + 4),   //Bearing of feature from centre
    t,                   //Angle in generation of ellipse
    z, w;                //Working variables

  int
    x = *(q + 1),        //x-position of observed object
    y = *(q + 2),        //y-position of observed object
    i = 1,               //`first time through' switch
    r = 7,               //major axis radius of ellipse
    u,                   //Ellipse-gen X-displacement
    v,                   //Ellipse-gen Y-displacement
    l = 0,               //Nš of characters in annotation
    c = *(n + 14) - 48;  //Display colour

  If(CosPsi != 0) {      //To prevent division by zero
    if(s) c = 0;         //set colour black if re-display
    _setcolor(c);

  //Take t round in a full circle in 0.1 radian steps

    for(t = 6.5; t > 0; t -= .1) {
      w = tilt * r * cos(t);
      z = CosPsi * (r * sin(t) - w * TanPsi);
      v = w / CosPsi + z * TanPsi;
      u = z;
      if(i == 0)                 //If not first pass of loop,
        _lineto( x + u, y + v ); //draw line to next valid point
      else {
        i = 0;                   //else clear `first pass' flag
        _moveto( x + u, y + v ); //and set position to start of 
      }                          //ellipse locus.
    }
    _floodfill(x, y, c);         //Fill in the ellipse
    while(*n != ' ') {l++; n++;} //Find length of city name
    n -= l;

    /* Annotate the ellipse with the name of the city or way 
       point it represents. Place the name at the left, right,
       above or below the ellipse as appropriate. */

    switch(*(n + 15)) {
      case 'L': x -= (7 + l * 7); break;            //left
      case 'R': x += 10; break;                     //right
      case 'A': x -= (l * 7 / 2); y -= 13; break;   //above
      case 'B': x -= (l * 7 / 2); y += 13;          //below
    } annotate( x, y, l, n );
  }
}