Method ProcessEdgesAtTopOfScanbeam

blocks/Clipper/src/clipper.cpp:3009–3113

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

void Clipper::ProcessEdgesAtTopOfScanbeam(const cInt topY)
{
  TEdge* e = m_ActiveEdges;
  while( e )
  {
    //1. process maxima, treating them as if they're 'bent' horizontal edges,
    //   but exclude maxima with horizontal edges. nb: e can't be a horizontal.
    bool IsMaximaEdge = IsMaxima(e, topY);

    if(IsMaximaEdge)
    {
      TEdge* eMaxPair = GetMaximaPairEx(e);
      IsMaximaEdge = (!eMaxPair || !IsHorizontal(*eMaxPair));
    }

    if(IsMaximaEdge)
    {
      if (m_StrictSimple) m_Maxima.push_back(e->Top.X);
      TEdge* ePrev = e->PrevInAEL;
      DoMaxima(e);
      if( !ePrev ) e = m_ActiveEdges;
      else e = ePrev->NextInAEL;
    }
    else
    {
      //2. promote horizontal edges, otherwise update Curr.X and Curr.Y ...
      if (IsIntermediate(e, topY) && IsHorizontal(*e->NextInLML))
      {
        UpdateEdgeIntoAEL(e);
        if (e->OutIdx >= 0)
          AddOutPt(e, e->Bot);
        AddEdgeToSEL(e);
      } 
      else
      {
        e->Curr.X = TopX( *e, topY );
        e->Curr.Y = topY;
#ifdef use_xyz
		e->Curr.Z = topY == e->Top.Y ? e->Top.Z : (topY == e->Bot.Y ? e->Bot.Z : 0);
#endif
	  }

      //When StrictlySimple and 'e' is being touched by another edge, then
      //make sure both edges have a vertex here ...
      if (m_StrictSimple)
      {  
        TEdge* ePrev = e->PrevInAEL;
        if ((e->OutIdx >= 0) && (e->WindDelta != 0) && ePrev && (ePrev->OutIdx >= 0) &&
          (ePrev->Curr.X == e->Curr.X) && (ePrev->WindDelta != 0))
        {
          IntPoint pt = e->Curr;
#ifdef use_xyz
          SetZ(pt, *ePrev, *e);
#endif
          OutPt* op = AddOutPt(ePrev, pt);
          OutPt* op2 = AddOutPt(e, pt);
          AddJoin(op, op2, pt); //StrictlySimple (type-3) join
        }