Method AppendPolygon

renderers/agg/src/clipper.cpp:1273–1372

//------------------------------------------------------------------------------

void Clipper::AppendPolygon(TEdge *e1, TEdge *e2)
{
  //get the start and ends of both output polygons ...
  PolyPt* p1_lft = m_PolyPts[e1->outIdx];
  PolyPt* p1_rt = p1_lft->prev;
  PolyPt* p2_lft = m_PolyPts[e2->outIdx];
  PolyPt* p2_rt = p2_lft->prev;

  //fixup orientation (hole) flag if necessary ...
  if (p1_lft->isHole != p2_lft->isHole)
  {
    PolyPt *p;
    PolyPt *bottom1 = PolygonBottom(p1_lft);
    PolyPt *bottom2 = PolygonBottom(p2_lft);
    if (bottom1->pt.Y > bottom2->pt.Y) p = p2_lft;
    else if (bottom1->pt.Y < bottom2->pt.Y) p = p1_lft;
    else if (bottom1->pt.X < bottom2->pt.X) p = p2_lft;
    else if (bottom1->pt.X > bottom2->pt.X) p = p1_lft;
    //todo - the following line really only a best guess ...
    else if (bottom1->isHole) p = p1_lft; else p = p2_lft;

    SetHoleState(p, !p->isHole);
  }

  EdgeSide side;
  //join e2 poly onto e1 poly and delete pointers to e2 ...
  if(  e1->side == esLeft )
  {
    if(  e2->side == esLeft )
    {
      //z y x a b c
      ReversePolyPtLinks(*p2_lft);
      p2_lft->next = p1_lft;
      p1_lft->prev = p2_lft;
      p1_rt->next = p2_rt;
      p2_rt->prev = p1_rt;
      m_PolyPts[e1->outIdx] = p2_rt;
    } else
    {
      //x y z a b c
      p2_rt->next = p1_lft;
      p1_lft->prev = p2_rt;
      p2_lft->prev = p1_rt;
      p1_rt->next = p2_lft;
      m_PolyPts[e1->outIdx] = p2_lft;
    }
    side = esLeft;
  } else
  {
    if(  e2->side == esRight )
    {
      //a b c z y x
      ReversePolyPtLinks( *p2_lft );
      p1_rt->next = p2_rt;
      p2_rt->prev = p1_rt;
      p2_lft->next = p1_lft;
      p1_lft->prev = p2_lft;
    } else