[
  {
    "id" : "layout",
    "type" : "ClutterBoxLayout",
    "vertical" : true,
    "spacing" : 12,
    "pack-start" : false
  },
  {
    "type" : "ClutterStage",
    "id" : "main-stage",
    "children" : [
      {
        "id" : "test",
        "type" : "ClutterBox",
        "layout-manager" : "layout",
        "children" : [
          {
            "id" : "child-1",
            "type" : "ClutterRectangle",
            "width" : "3 em",
            "height" : "3 em"
          }
        ],
        "constraints" : [
          {
            "type" : "ClutterAlignConstraint",
            "name" : "x-align",
            "factor" : 0.5,
            "align-axis" : "x-axis",
            "source" : "main-stage"
          },
          {
            "type" : "ClutterAlignConstraint",
            "name" : "y-align",
            "factor" : 0.5,
            "align-axis" : "y-axis",
            "source" : "main-stage"
          }
        ]
      }
    ]
  }
]