analog clock hands w/ gfx

// draw analog clock
// does the hands only
template<typename Destination>
void draw_clock(Destination& dst, tm& time,const srect16& bounds) {
  srect16 b = bounds.normalize();
  uint16_t w = min(b.width(),b.height());

  // using a viewport to do our rotation
  // but we're not going to draw to it
  // instead we just use its rotate
  // and translate features.
  using view_t = viewport<Destination>;
  view_t view(dst);
  view.center(spoint16(w/2,w/2));

  // create the second hand
  srect16 sr(0,0,w/16,w/2);
  sr.center_horizontal_inplace(b);
  // rotate the second hand
  view.rotation((time.tm_sec/60.0)*360);
  // here we translate each of the
  // rectangle points using the view
  spoint16 second_points[] = {
    view.translate(spoint16(sr.x1,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y2)),
    view.translate(spoint16(sr.x1,sr.y2))
  };
  spath16 second_path(4,second_points);

  // create the minute hand
  view.rotation((time.tm_min/60.0)*360);
  spoint16 minute_points[] = {
    view.translate(spoint16(sr.x1,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y2)),
    view.translate(spoint16(sr.x1,sr.y2))
  };
  spath16 minute_path(4,minute_points);

  // create the hour hand
  sr.y1 += w/8; // shorter
  view.rotation((time.tm_hour/24.0)*360);
  spoint16 hour_points[] = {
    view.translate(spoint16(sr.x1,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y1)),
    view.translate(spoint16(sr.x2,sr.y2)),
    view.translate(spoint16(sr.x1,sr.y2))
  };
  spath16 hour_path(4,hour_points);

  // draw them

  draw::filled_polygon(dst,minute_path,color<typename Destination::pixel_type>::black);

  draw::filled_polygon(dst,hour_path,color<typename Destination::pixel_type>::black);

  draw::filled_polygon(dst,second_path,color<typename Destination::pixel_type>::red);

}