ue": null,
          "on": [
            {
              "events": "click",
              "update": "datum ? {value: datum.id, depth: datum.depth} : null",
              "force": true
            }
          ]
        },
        {
          "name": "clear",
          "value": true,
          "on": [
            { "events": "mouseup[!event.item]", "update": "true", "force": true }
          ]
        },
        {
          "name": "shift",
          "value": false,
          "on": [{ "events": "click", "upda