The onRowClick event is fired when the user clicks a task row header of the Gantt Chart, before the default action (specified by the rowClickHandling property).
The default action can be canceled by calling args.preventDefault().
args.task - a DayPilot.Task object representing the task
args.x (number) - the column index (available since 2023.1.5529)
args.preventDefault() - cancels the default action
Gantt Chart config:
{
  rowClickHandling: "Enabled",
  onRowClick: (args) => {
    DayPilot.Modal.alert("Clicked: " + args.task.id());
  },
  // ...
}