Adding HTML to the chart

Your UDI can add HTML to its chart, either just as decoration or to provide additional functionality. This mechanism is very flexible, but it can become complicated if you want the UDI to interact with the HTML.

The HTML is added to the chart in a sandboxed iframe. It has no access to the rest of the web page, and it has no direct access to any framework or indicator features. However, the HTML can send messages to the UDI, and the UDI can send messages to the HTML. Therefore, for example, the HTML can have something like a button which sends a message to the UDI, and the UDI then carries out some action. Similarly, the HTML can have input fields. You can post a message to the UDI containing the value of the fields, and then use this data in the UDI to change its behaviour.

To display only HTML, with no standard indicator drawing, you simply return an empty plots[] array in your initialisation.