PortalSelector

type PortalSelector = 
  | string
  | null
  | ((context) => string | Element | null | undefined);

Resolves the JointJS selector used to find the React portal target node inside a cell view.

• A string is used directly as the selector for cellView.findNode().
• null disables all portal rendering.
• A function receives a PortalSelectorParams and returns:
  • a selector string, look up that node,
  • an Element, use that DOM node directly,
  • null, skip rendering for this cell,
  • undefined (or no return), fall back to joint-react's default selector.