procedure TForm1.Button1Click(Sender: TObject);
var
pt: MapXlib_tlb.point;
pts: Mapxlib_tlb.Points;
f : Mapxlib_tlb.Feature;
mx: Double;
my: Double;
begin
pt:=CoPoint.Create() ;
pts:=CoPoints.Create ();
mx:=map1.CenterX;
my:=map1.CenterY;
pt.Set_(mx - 0.5, my - 0.5);
pts.Add(pt,EmptyParam);
pt.Set_(mx - 0.5, my + 0.5);
pts.Add(pt,EmptyParam);
pt.Set_(mx + 0.5, my + 0.5);
pts.Add(pt,EmptyParam);
pt.Set_(mx + 0.5, my - 0.5);
pts.Add(pt,EmptyParam);
pt.Set_(mx - 0.5, my - 0.5);
pts.Add(pt,EmptyParam);
f:=Map1.FeatureFactory.CreateLine(pts,EmptyParam);
Map1.Layers.Item(1).AddFeature(f,EmptyParam);
end;