docs: function mxStackLayout(graph, horizontal, spacing, x0, y0, border)
  {
  	mxGraphLayout.call(this, graph);
  	this.horizontal = (horizontal != null) ? horizontal : true;
  	this.spacing = (spacing != null) ? spacing : 0;
  	this.x0 = (x0 != null) ? x0 : 0;
  	this.y0 = (y0 != null) ? y0 : 0;
  	this.border = (border != null) ? border : 0;
  }