DragEventArgs

This property needs to be adjusted by handlers to tell the engine that the event has been handled.

Note that this property needs to be set before the function synchronously returns. This means that setting the value in an async function after the first await or in an asynchronous callback, it cannot not be seen by the emitter of the event and the sender will consider the event as not being handled.

// wrong:
mode.addEventListener('drag-enter', async (evt) => {
  await something()
  evt.handled = true // will be set *after* all other event listeners have been invoked, only
})

// correct:
mode.addEventListener('drag-enter', async (evt) => {
  evt.handled = true // will be set immediately and 'mode' will see the change
  await something()
})