/*
 * graphical interfaces
 */

#include "config.h"

#include "interface.h"

// the simplest way I could imagine fast enough to find out wether a polygon
// is clockwise or ccw could probably be *much* faster
//
double winding (const points &v) t_no
{
  double wind = 0;
  
  points::const_iterator a = v.begin ();
  points::const_iterator b = a; b++;
  points::const_iterator c = b; c++;
  
  for (;;)
    {
      if (c == v.end ()) c = v.begin ();
      if (b == v.end ()) b = v.begin ();
      if (a == v.end ()) return wind;
      
      vec d = cross (b->v - a->v, c->v - b->v);
      
      if (abs (d) > 1e-6) // ignore almost coincident edges
        wind += normalize (d) * normalize (b->n);
      
      ++c;
      ++b;
      ++a;
    }
}