anchor.diff:        Procedure stbtt__add_point(points: PStBttPointArray; n: Integer; x, y: Single);
         Function stbtt__tesselate_curve(points:PStBttPointArray; var num_points: Integer; x0, y0, x1, y1, x2, y2, objspace_flatness_squared: Single; n: Integer): Integer;
         Procedure stbtt__rasterize_sorted_edges(resultBitmap:Image; e:EdgeList; vsubsample, off_x, off_y: Integer);
  -      Procedure stbtt__fill_active_edges(scanline: PByteArray; len: Integer; e: PStBttActiveEdge; max_weight: Integer);
  -      Function new_active(Const e: TStBttEdge; off_x: Integer; start_point: Single): PStBttActiveEdge;
  +      Procedure stbtt__fill_active_edges(scanline: PByteArray; len: Integer; e:TStBttActiveEdge; max_weight: Integer);
  +      Function new_active(Const e: TStBttEdge; off_x: Integer; start_point: Single):TStBttActiveEdge;
   
       Public
         Constructor Create(Source:Stream); Overload;
  
positive.code:          while step^<>nil do
           begin
              z := step^;
              if (z^.ey <= scan_y) then
              begin
                 step^ := z^.next; // delete from list
                 z^.valid := 0;
                 Dispose(z);
              end else begin
                 Inc(z^.x, z^.dx); // advance to position for current scanline
                 step := @(PStBttActiveEdge((step^)^.next)); // advance through list
              end;
           end;
  
  
negative.code:    active := nil;
     j := 0;
     max_weight := 255 div vsubsample;  // weight per vertical scanline
  
     y := off_y * vsubsample;
  
  