mutter/doc/cookbook/examples/script-ui.json

[
  {
    "id" : "stage",
    "type" : "ClutterStage",
    "is-default" : true,
    "width" : 400,
    "height" : 400,
    "color" : "#333355ff",
    "children" : [ "box" ]
  },

  {
    "id" : "box",
    "type" : "ClutterBox",
    "width" : 400,
    "height" : 400,

    "layout-manager" : {
      "type" : "ClutterBinLayout",
      "x-align" : "CLUTTER_BIN_ALIGNMENT_CENTER",
      "y-align" : "CLUTTER_BIN_ALIGNMENT_CENTER"
    },

    "children" : [
      {
        "id" : "rectangle",
        "type" : "ClutterRectangle",
        "width" : 200,
        "height" : 200,
        "color" : "red"
      }
    ]
  }

]