Just In Mac Pro · 2026 documentation

Overlays - Data Mappings v.2026.x

Data mappings enable the integration of external data sources into Custom Overlays. By reading external files, such as JSON files, at regular intervals, the Custom Overlay can be automatically updated. Below is an example that illustrates how to integrate an external data point.

Code Example (External Data Mapping):

{
  "data-adapters": [
    {
      "mappings": {
        "external_value": "external_value"
      },
      "update-interval": 2,
      "name": "datamapping",
      "type": "json",
      "url": "file:\/\/\/datamapping.txt"
    }
  ],
  "components": [
    {
      "insets": {
        "bottom": 0,
        "top": 0,
        "left": 0,
        "right": 0
      },
      "w": 250,
      "h": 50,
      "font": {
        "name": ".AppleSystemUIFont",
        "size": 40
      },
      "x": 25,
      "outline-width": -1,
      "y": 25,
      "draws-background": true,
      "hidden-when-empty": false,
      "metadata-value": {
        "prefix": "External: ",
        "accepts-number": true,
        "key": "external_value",
        "type": "number",
        "accepts-string": true,
        "retain-previous-on-empty": true,
        "minimum-integer-digits": 0,
        "maximum-integer-digits": 42,
        "minimum-fraction-digits": 0,
        "maximum-fraction-digits": 1
      },
      "background-colour": {
        "r": 0,
        "b": 0,
        "g": 0,
        "a": 0.5
      },
      "type": "text",
      "outline-colour": {
        "r": 0,
        "b": 0,
        "g": 0,
        "a": 1
      },
      "alpha": 1,
      "alignment": 1,
      "layer": 1,
      "hidden": false,
      "text-colour": {
        "r": 1,
        "b": 1,
        "g": 1,
        "a": 1
      }
    }
  ],
  "async-data-updates": false
}

External File (datamapping.txt)

{ "external_value": 17}

Result

Start:

{ "external_value": 17}

Value Change:

{ "external_value": 11}

Download

The example JSON code can be downloaded here.