This commit does not try to make the events correct/perfect with regard to
GStreamer states, end-of-stream signalling, etc. It only tries to make the
events work consistently across all the methods on the playback controller.
* play(track) while already playing has changed from:
- playback_state_changed(old_state='playing', new_state='playing')
- track_playback_started(track=...)
to:
- playback_state_changed(old_state='playing', new_state='stopped')
- track_playback_ended(track=..., time_position=...)
- playback_state_changed(old_state='stopped', new_state='playing')
- track_playback_started(track=...)
* next() has changed from:
- track_playback_ended(track=..., time_position=...)
- playback_state_changed(old_state='playing', new_state='stopped')
- track_playback_ended(track=..., time_position=0)
- playback_state_changed(old_state='stopped', new_state='playing')
- track_playback_started(track=...)
to same as play() above.
* previous() has changed in the same way as next().
* on_end_of_track() has changed from:
- track_playback_ended(track=..., time_position=...)
- playback_state_changed(old_state='playing', new_state='playing')
- track_playback_started(track=...)
to same as play() above.
* stop() has reordered its events from:
- track_playback_ended(track=..., time_position=...)
- playback_state_changed(old_state='playing', new_state='stopped')
to:
- playback_state_changed(old_state='playing', new_state='stopped')
- track_playback_ended(track=..., time_position=...)
