How to Add direction to custom connections

I created custom element with the help of the link in bpmn.js. But custom elements do not have a direction (arrow ->), I would like to know how to add it to indicate the stream (current ----> target)


What is you mail element supposed to represent? What are you trying to achieve?

Here mail element is a just like simple custom task in bpmn workflow. Here, i wanted the arrow direction for mail element like same as the task element as shown above.

I guess the custom-elements example is not the right example for you then. Conisider using this example instead. It adds custom properties to an existing element, therefore, the resulting BPMN will be valid.