Image events are never pushed.
ImageStatusCallback never pushes events because of how the last event time is stored: it is always updated even when no events is sent, and the comparison is wrong anyway (current time < next time instead of current time >= next time). Also, the way it's done, you can miss the last frame, so I suggest sending it when:
- last_acquired == -1
- status changed (this way there's an even when the last frame of an acquisition is available, because the status is back to "AcqReady" when the callback is called)
- current time > last event time + delay